Godina / Year 2013
ZAGREB
Rujan / Listopad
Broj / No 10
Sadržaj / Content
1
2
Poruka predsjednice /A Message from the President
Poruka urednika /A Message from the Editor
Lovre KRSTULOVIĆ-OPARA:
APPLICATION of THERMOGRAPHY in ANALYSIS of FATIGUE STRENGTH of MATERIALS and STRUCTURES
Lovre KRSTULOVIĆ-OPARA:
PRIMJENA TERMOGRAFIJE u ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
3-11
12-17
Dubravko MILJKOVIĆ: ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
19-23
Petar SMILJANIĆ: ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
24-31
Radovi održani na savjetovanju MATEST 2011:
Dubravko MILJKOVIĆ: MISFUELING DETECTION WITH TWO OFFSETED CAPACITIVE FUEL SENDERS
32-38
Predstavljamo vam:
CROATIAINSPECT
39-41
NDT WEEK in ZAGREB
MATEST 2013
The Preliminary Program: CERTIFICATION 2013
42
43
44-45
HDKBR Centar za obrazovanje
HDKBR Centar za certifikaciju
MATEST 2013/ poster session
46
47
47
Pomoć u radu:
Goran DRAGIČEVIĆ
RJEŠENJE za POZICIONIRANJE ULTRAZVUČNIH APARATA
48
Izdavač: HDKBR
Hrvatsko društvo za kontrolu bez razaranja
Publisher: CrSNDT
The Croatian Society for Non Destructive Testing
Direktor / Director:
mr.sc. Miro Džapo
Tajništvo/Secretariat:
HIS, Petra Berislavića 6. 10000 Zagreb, RH
Tel: +385 (01) 60 40 451
Fax:+385 (01) 61 57 129
E-mail: [email protected],
Website: www.hdkbr.hr
Kontakt/Contact: Nina Bukovšak
Izdavački odbor:
Prof.dr.sc. Vjera Krstelj (Glavni urednikr)
Dr.sc. Dubravko Miljković (Izvršni urednik)
Dr.sc. Dario Almesberger
Prof.dr.sc. Nenad Gucunski
Mr.sc. Irena Leljak
Prof.dr.sc. Lovre Krstulović Opara
Bojan Milovanović, dipl.ing.građ. (mag. aedif.)
Mag.Nenad Nikolić
Suradnici:
Mag. Ivan Smiljanić (tehnička podrška)
Prof. Marina Manucci (eng. lektor)
Prof. Davor Nikolić (hrv. lektor)
Sandro Bura (priprema za tisak)
Nina Bukovšak (distribucija)
HDKBR Info izlazi četiri puta godišnje/ distribucija 300 kom/broj
CrSNDT journal is published four times a year/circulation 300 each journal
Godišnja pretplata 300 kn / 4 issues per year 40 Euro
Časopis je besplatan za članove HDKBR-a
The yournal is free for CrSNDT members
HDKBR Info možete pratiti na www.hdkbr.hr
An online version is available
DOSTAVA PRILOGA
HDKBR poziva članove i sve koji imaju materijale interesantne čitateljima
ovog časopisa da ponude priloge. Znanstveni i stručni radovi će biti recenzirani od strane međunarodno priznatih eksperata. Za reprodukciju publiciranih radova i izvadaka treba osigurati dozvolu. Tekstovi i mišljenja autora u časopisu ne moraju biti u suglasju sa stavovima HDKBR-a i uredništva.
Uredništvo ne nosi odgovornost za pogreške i propuste autora radova.
PAPER SUBMISSION
CrSNDT invites contributions that will be interesting for readers of HDKBR
info Journal. Technical papers submitted are peer-reviewed by an Internationaly recognised experts. Permition should be obtained for reproduction
of individual artlices and extracts.the Articles and views expressed in the
publication are not necessarily in line with CrSNDT, editor and editorial.
No liability is accepted for errors or omission.
OGLAŠAVANJE/ADVERTISEMENT
Cijena oglašavanja/The cost for advertising is:
Stranica/Page in yournal
Cijena za 4 broja /Cost for 4 numbers per
year
Zadnja/The last page
(cover page A4 size)
8000 kn
1080 Euro or 1380 $
(US)
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size)
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270 Euro or 395 $ (US)
Cijena oglasa u samo jednom broju iznosi pola cijene godišnjeg oglašavanja.
The price of advertisement published (in only one journal number) is half of the
yearly cost.
Poruka predsjednice
Poštovani čitatelji, drage kolegice i kolege, s radošću i veseljem vas pozivamo da se uključite i pomognete svojom prisutnosti u nastojanju HDKBR-a
da bude dio međunarodne “NDT” zajednice, doprinoseći tako unapređenju
znanja, poboljšanju obrazovanja u našoj profesiji i općenito boljoj i pouzdanijoj
primjeni nerazornih metoda u osiguravanju kvalitete i sigurnosti proizvoda i
usluga.
Za manje od mjesec dana u okviru značajnih međunarodnih sastanaka i
putem razmjene informacija, mišljenja i znanja na konferencijama MATEST
2013 i CERTIFICATION 2013, u okviru tjedna koji smo nazvali:
NDT week in Zagreb
7. - 12. listopada 2013.
pruža se prilika svakom sudioniku da dopuni svoja znanja, ovaj put posebno o razvoju sustava obrazovanja i certifikacije, te da sudjelovanjem i osobnim primjedbama doprinese unapređenju sustava
obrazovanja i certifikacije za osoblje koje primjenjuje nerazorne metode ispitivanja.
O programu savjetovanja i predavačima koje ćete imati prilike upoznati saznajte na stranicama ovog
broja časopisa, a više na www.certification2013.com.
Iskreno se zahvaljujemo svim članovima koji su godinama sudjelovali u radu naše udruge te je svojim znanjem i zalaganjem doveli do današnje razine razvoja, kada s ponosom obilježava 50 godina
uspješnog djelovanja. Zahvaljujemo se također međunarodnoj NDT zajednici koja je uvijek i na svim
razinama s velikom pažnjom i prijateljski prihvaćala naše sudjelovanje.
Sve vas s radošću očekujemo u Zagrebu.
A message from the President
Dear readers, dear colleagues,
it is with great joy and pleasure that we may invite you to participate and help us by your presence
in the efforts of CrSNDT to be part of the international “NDT” community, contributing thus to the
improvement of knowledge, enhancement of education in our profession and generally to better and
more reliable application of non-destructive methods providing quality and safety of products and
services.
In less than a month, as part of significant international meetings and through exchange of information, attitudes and knowledge at the Conferences MATEST 2013 and CERTIFICATION 2013, during
a week that we have entitled
NDT week in Zagreb
7-12 October 2013
every participant will have the opportunity to improve their knowledge, this time separately about the
development of the education and certification systems, and to contribute by personal attendance
and participation in discussions to the improvement of the education and certification systems for the
personnel applying non-destructive testing methods.
Please, find more information about the Conference Programme and about the presenters you will
have the opportunity to meet, on pages of this Journal, and even more at www.certification2013.com.
We would like to thank most sincerely all the members who have been participating in the activities
of our society, CrSNDT, for so many years, and whose knowledge and efforts have made it possible
to reach the today’s level of development, when we proudly celebrate the 50th anniversary of successful operation. We would also like to thank the international NDT community who has always and
at all levels with great attention and friendliness accepted our participation.
With great pleasure we are looking forward to meeting you in Zagreb.
Prof. Vjera Krstelj, Ph.D.
1
Poštovani čitatelju,
željeli bismo uvrstiti naš časopis u Scopus bazu podataka, što bi dalje
doprinijelo ugledu i važnosti časopisa. Scopus (u vlasništvu Elseviera)
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Da bi uspješno uvrstili časopis u bazu, napravili smo i neke korake koji
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autore da bi postigli bolju ujednačenost grafičkog izgleda objavljenih
radova i olakšali posao našem tehničkom uredniku.
Vaše sudjelovanje u časopisu od presudne je važnosti. Ako imate kakav zanimljiv i kvalitetan
znanstveni ili stručni rad, pošaljite nam ga za uvrštenje u sljedeće brojeve časopisa.
Dear reader,
Our current goal is to be included in the Scopus database which would further contribute
to the prestige and importance of the journal. Scopus (owned by Elsevier) is the largest
abstract and citation database of peer-reviewed research literature in the fields of science,
technology, medicine, social sciences and Arts & Humanities. It delivers a comprehensive
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international publishers with 20,000 peer-reviewed journals (including 2,600 open access
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For journal to be successfully included in the database we have made some steps to facilitate the listing. Journal now has its own, separate, web address within the society with a
new look, description and ethics of publication. We have prepared instructions for authors
to achieve greater graphical uniformity of published paper and to make life easier for our
technical editor.
Your participation in the journal is welcome. If you have interesting scientific and professional paper, please send it for inclusion in the next issues of the journal.
S poštovanjem / Sincerely
dr. sc. Dubravko Miljković
Izvršni urednik/Handling Editor
2
Lovre KRSTULOVIĆ-OPARA, Fakultet elektrotehnike, strojarstva i brodogradnje, Sveučilište
u Splitu, R. Boškovića 32, HR-21000 Split, www.fesb.hr/kk, [email protected]
ABSTRACT - Thermography is becoming more and more relevant method in industry
and as a research tool. It is an accepted method in many fields where non-destructive
testing is carried out. In this paper focus was on evaluation of stress concentrations and
fatigue of metal structures. Three thermographic methods: Thermoelastic stress analysis,
Risitano method and acquisition of plastification zone and fracture propagation, are addressed and compared with results of classical cyclic testing of Al2024 alloy specimens.
Specimens with three types of stress concentrator are used; 3 mm triangular notch, R3
mm circular notch, and a hole with 6 mm diameter. All thermographic methods showed
high level of coincidence with classical fatigue tests. Thermoelastic stress analysis provides first stress invariant field for cyclic loaded sample, revealing stress concentrations
near notches. Risitano method, from thermal dissipations at various levels of cyclic load,
estimates dynamic strength of materials. Fast cooled middle-wave infrared cameras enable locating and tracing material plastification and fracture propagation. The outcomes
of all evaluated methods are in accordance with each other.
Keywords: Thermoelastic stress analysis, Risitano method, plastification, fracture propagation, fatigue, cyclic loading
1.INTRODUCTION
Infrared thermography is nowadays an
accepted non-destructive testing (NDT)
method. It is applied as passive and active
method, as described in our previous work
[1-3]. Active thermography is used in NDT
of composite polymer materials. Passive
thermography is a method used in analysis
of materials and structures, e.g. fatigue
strength estimation. Passive thermography
can also be used in evaluation and detection
of plastification and fracture propagation.
When used in estimation of fatigue limit it can
be considered an NDT method due to the
fact that fatigue strength can be estimated
without destroying a single specimen.
Fatigue strength estimation is generally
based on destructive testing of specimens
or whole sections of structure with the goal
of predicting the fatigue limit of cyclic loaded
structures. Detection and prevention of
stress concentrations, as the main source
of fracture initialization, is mostly limited
to numerical simulations or experimental
measurements with methods such as strain
gauges, photoelasticimetry, etc. The
realistic visualization of structure’s stress
or strain distribution is hardly achievable
with the majority of NDT methods. Strain
gauges are applicable for dynamic strain
measurements, providing reliable results,
but with the drawback of enabling readings
only in locations of application. The current
development, sensitivity and price of IR
thermograpy equipment enabled several
thermographic approaches to become
popular and accepted as an NDT tool. In the
field of dynamic testing the Thermoelastic
Stress Analysis (TSA) [3-12] enables a
full field visualization of surface stress
distribution (the method provides first
stress invariant). The estimation of fatigue
strength is possible by several passive
thermography methods such as Risitano
method [13, 14] or Meneghetti method
based on energy dissipation [15, 16]. With
these methods it is possible to significantly
reduce, or completely avoid destruction of
test specimens, which reduces the time and
cost of fatigue testing.
3
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF
FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
1.INTRODUCTION
Lord Kelvin found that elastically deformed
bodies generate temperature changes when
loading is applied, where tension causes
cooling, while compression causes heating.
In zones of stress concentrations these
effects are more pronounced. For the case
of metals, e.g. steel or aluminium, these
changes are few milligrades, while for the
case of plastic deformations changes are
of several grades Celsius. These thermal
changes, characterized by significant heat
generation, enable detection and estimation
of plastification zone propagation, crack
propagation or final rupture scenario. The
described IR-based methods are applicable
to all structural materials, where applicability
depends on the surface emission
characteristics. Good emission coefficient
can always be achieved by the application
of high emissivity paint, e.g. Nextel
Velvet-Coating 881-21 [17] with emission
coefficient of 0.95, Figure 1. In this paper an
overview of three methods is given, where
the described methods enable visualization
of stress distribution, estimation of fatigue
limit and detection of plastification or
fracture propagation. The obtained results
are compared with classical fatigue testing
(S-N diagrams). The used specimens are
made of aluminium alloy Al2024 with cross
section of 20x4 mm and cyclically loaded
(r=Fmin/Fmax=0) with loading frequency of
20 Hz. The test specimens are machined
with stress concentrators in the form of 6
mm hole, V shape notch (3mm in depth)
and semi-circular notch (R3 mm). The cross
section of the notched zone is the same for
all specimens (14x4 mm).
Figure 1 - Experimental setup and specimens
with stress concentrators (V notch, semicircular
notch and hole)
4
Although all described methods are
fully applicable to reinforced polymer
composites, only aluminium alloy will be
addressed herein. Polymer composites are
characterized by significantly lower thermal
diffusivity so that the evaluation of such
materials is for some of the methods possible
even with LW thermal cameras based on
micro-bolometric detectors. Due to the high
thermal conductivity, high thermal diffusivity
and low thermal capacity, metal specimens
are characterized by fast thermal changes
requiring detection with cooled MW thermal
cameras based on photonic detectors. These
cooled MW cameras enable acquisition with
frame rates of over 700 Hz., where the limit
is not due to the technology of detector, but
due to the rate of data transfer to computer.
Fast cooled MW detectors enable sharp
images of dynamic occurrences (20 Hz
cyclic loading rate for described examples),
which is not the case for micro-bolometric
LW detectors. The results presented here
are provided by cooled MW camera FLIR
SC 5000, with image resolution of 320x256
pixels and sensitivity of 0.02 K. Currently on
the market there are similar cameras with
double resolution, same sensitivity, but with
lower frame rate. For the reduced image
size the frame rate is increased up to over
700 Hz. The IC camera used herein, for
the full image resolution (320x256 pixels),
enabled frame rates of around 150 Hz.
2.EVALUATION OF STRESS
DISTRIBUTION BASED ON
THERMOELASTICITY
In 1850 Lord Kelvin described the
thermoelastic effect based on the fact
that the applied load causes thermal
changes of objects. In 1915 Compton and
Webster conducted the first experimental
proof, while in 1967 Belgen provided the
first non-contact measurements [18].
With the development of non-contact IR
measurement technology method became
of particular scientific interest. In 1982 the
first images were provided by Ometron
SPATE 8000 instrument, where several
hours were needed for the acquisition of
∆T =
−α T
(σ + σ 2 )
ρ Cp 1
,
(1)
where α is coefficient of thermal expansion,
T is room temperature, ρ specimen density,
Cp thermal capacity at constant pressure,
while σ1 and σ2 are principal stresses.
Supposing that coefficients α, T, ρ and Cp
are constant for the observed specimen,
equation (1) provides direct relation between
increase in temperature and first stress
invariant (the sum of principal stresses,
where for the body surfaces 3rd principal
stress σ3=0). Relation (1) holds for adiabatic
condition (no gain or heat loss), which is
satisfied for fast load changes (around 10
Hz). Thus, the method requires acquisition
with fast cooled MW cameras, cyclic
specimen loading of approximately 10 Hz
(although loading can be reduced to 3 Hz)
and sufficiently high level of stress changes.
Load can be generated by magnetic field,
ultrasound, or dynamic load actuator as
described herein. When acquiring images
of a cyclically loaded specimen (Figure 1)
at load frequency of 20 Hz, cyclical heat
flashes are recorded (Figure 2). In zones
of stress concentrations these flashes are
stronger. The cyclically loaded specimen
in Figure 2 provides images of stress
distribution, where cooler zones are zones
with higher tensile stresses. As the camera
frame rate was set up to 50 Hz (camera
system enables higher frame rates), the
set of images in Figure 2 demonstrate the
problem of capturing the moment of highest
loading.
Figure 2 - Thermal flashes of cyclic loaded
specimen (loading frequency of 20 Hz)
Even when the moment of highest loading is
captured, relation (1) will not provide realistic
results. To obtain the precise reading of the
first stress invariant, an additional hardware
component, the so called Lock-In, is
required. The Lock-In provides information
about applied loading (e.g. the load cell
signal) and integrates it with thermal set of
images enabling correct stress distribution
based on relation (1). Figure 3 illustrates on
an example of fillet welded test specimen
[19] the difference between raw image
and image obtained after Lock-In image
processing.
Figure 3 - Raw image and stress distribution
after Lock-In image processing
5
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
stress distribution. The SPATE 8000 was
based on a single thermal detector (thermal
diode) and set of synchronized moving
prisms providing surface thermal scan. In
1994 the introduction of digital focal point
array technology enabled by instrument
Stress Photonic the stress distribution
acquisition within a few minutes.
The TSA method is based on the
thermoelastic relation:
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
Although a very reliable method, the TSA is
not so common in literature. The limitations
of the method are that cyclic loading is
required, the loading must achieve a certain
stress level, and the method requires
relatively expensive cooled LW camera.
The examples of the method are available in
references [6, 20-23]. The TSA method is a
full field NDT method providing visualization
of stress distribution for the whole observed
body surface. The method is similar to
the method of photoelasticimetry, with the
difference in result in the form of the first
stress invariant.
3.EVALUATION OF FATIGUE
LIMIT BASED ON THE
RISITANO METHOD
The Risitano method [13, 14] is based on the
fact that at the beginning of cyclic loading,
a small increase in specimen’s temperature
occurs. The increase is stabilized after a
few loading cycles, remaining constant
until rupture (constant supposing there is
no increase in temperatures of the whole
experimental setup). A few cycles before
rupture, there is significant increase in
specimen’s temperature, followed by
temperature drop after rupture. Figure 4
depicts the increase in temperature during
the first load cycles of specimen with
V-shaped notch, and sudden increase in
temperature for the last loading cycles
before rupture (example of 4 kN cyclic
loading). This effect is similar to the effect
of stress-strain hysteresis that can be
observed for the first few loading cycles and
the last few cycles before rupture during
standard fatigue cyclic test. This hysteresis
disappears at the beginning and reappears
close to the end of fatigue test. Contrary
to classical fatigue test, where several test
specimens are needed, the Risitano method
enables estimation based on a single test
specimen, where final specimen rupture
can be avoided. Fatigue limit is estimated
from the fact that for a certain amount of
load there is no temperature increase. The
method is simple and applicable using LW
6
micro-bolometric cameras. When applied
with more sensitive MW cooled cameras,
due to the higher acquisition sensitivity, small
thermal fluctuations appearing from elastic
loading-unloading thermoelastic effect
require additional smoothing of temperature
data readings. The upper diagram in Figure
5 displays raw temperature data. The lower
diagram in Figure 5 displays the smoothed
curve that enables easier data evaluation.
Thermal fluctuations in the upper diagram
are thermal flashes illustrated in Figure 2.
LW micro-bolometric cameras do not need
such data processing due to the fact that
sensitivity and frame rate of such cameras
are much lower.
Figure 4 - Increase, stabilization and final
increase of specimen’s temperature
Figure 5 - Thermal fluctuation and smoothed
thermal diagram acquired by LW cooled IR
camera
During elastic cyclic loading tension causes
cooling, while compression causes heating
of the test specimen according to relation
(1). Significant heat generation appearing
in zones of yielding enables recording the
whole plastification process. Materials with
high thermal capacity and low conductivity
enable use of LW micro-bolometric cameras.
Metals require acquisition with cooled LW
cameras. Figures 6-8 depict sequences
of plastification initialization, propagation
and final rupture. Temperature differences
between upper and lower part of specimens
are caused by heat flow due to the thermal
difference of grips, where lower grip is
connected to hot hydraulic piston and the
upper one is connected to the cooler load
cell.
Figure 6 - Propagation of plastification zone
until rupture for V-notched specimen
Figure 7 - Propagation of plastification zone
until rupture for specimen with hole
Figure 8 - Propagation of plastification zone until
rupture for specimen with semicircular notch
5.COMPARISON OF IR-BASED
METHODS WITH CLASSICAL
CYCLIC FATIGUE TESTS
To demonstrate the capabilities of IR-based
methods the obtained results are compared
with classical fatigue test for specimens
in Figure 1. The S-N diagrams (stress
vs. number of cycles) providing relation
between the level of sinusoidal cyclic loading
and the achieved number of cycles in the
logarithmic scale are depicted in Figures
9-11. Symbol “x” in diagrams symbolizes the
moment of specimen failure, while the red
lines are the mean values for cases where
several specimens are loaded with the
same cyclic load. Cycling was performed
on servo-hydraulic dynamic testing load
frame Instron 8800 50 kN at the frequency
of 20 Hz. Due to the limited number of
available specimens the number of three
specimens per each load case has not been
achieved. Although partial, S-N diagrams
do show material fatigue resistance, making
them comparable to the results obtained by
addressed IC-based methods.
Figure 9 - S-N diagram for V-shaped notch
7
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
4.EVALUATION OF
PLASTIFICATION AND
RUPTURE PROPAGATION
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
Figure 10 - S-N diagram for specimen with hole
Figure 11 - S-N diagram for semicircular notch
Figure 12 . Stress distribution of V-notched,
semicircular notched and specimen with hole at
8 kN cyclic loading
The TSA enables visualization of stress
distribution for all analyzed specimens.
Figure 12 depicts stress distribution
for maximal cyclic load level of 8 kN
(corresponds to nominal stress of 143 MPa).
Stress scale shows maximal stress
appearing for V-shaped notch (94.26 MPa),
while semicircular notch has minimal stress,
which is comparable to S-N diagrams,
where the lowest fatigue resistance
characterizes a V-notched specimen.
The specimen with hole has slightly lower
fatigue resistance than the semicircular
notched specimen, which is comparable to
maximal stresses in Figure 12 (48.87 MPa
for specimen with hole, 42.97 MPa for
the semicircular notched specimen).
Figure 13 - Stress distribution for specimen
with hole and semicircular notched specimen at
cyclic loading of 16 kN
The thermo elastic effect becomes
stronger at higher loadings. Thus, it is not
only necessary to achieve the required
loading frequency, but the loading level as
well. In Figure 13 the stress distribution
of V-notched specimen is not displayed
as the specimen already ruptured for
the loading lower than 16 kN (286 MPa).
The Risitano method is based on recording
the specimen’s temperature for cyclic
loaded specimen at different loading levels.
Figure 14 depicts the mean temperature of
the measured area (blue quadrilateral) for
6,000 cycles of sinusoidal loading at the
frequency of 20 Hz. Camera frame rate was
set to 50 Hz. Although higher frame rates
8
Figure 17 - Time diagram of mean temperature
for test area of semicircular notched specimen
Figure 14 - Time diagram of mean temperature
for test area
Thermal diagrams in Figures 15-17 depict
thermal increase during 6,000 loading cycles
for different load levels at the frequency of
20 Hz, where the ratio of load extremes was
r=Fmin/Fmax=0. The initial temperature
level depends on the specimen’s room
temperature and does not influence the
method as only relative thermal increase
during the test is observed. For each case
the thermal increase is higher for higher
loading levels. The rupture is characterized
by sudden increase in temperature,
followed by temperature drop after rupture.
Diagrams in Figures 18-20 are thermal
increases of mean temperatures displayed
in Figures 15-17. At the point where the line
defined by linear approximation reaches
zero the thermal increase is nominal
maximal stress, that is: for V-notched
specimen 44 MPa, for specimen with hole
123 MPa, and for semicircular notched
specimen 126 MPa. These results
correspond to the results of maximal stress
obtained by the TSA method at the same
level of loading (Figure 12), where maximal
stress is observed for V-notched specimen
(94 MPa), while for specimen with hole it
is 49 MPa, and for semicircular notched
specimen it is 43 MPa.
When comparing the results of the Risitano
method with the maximal nominal stress
in S-N diagrams (Figures 9-11), maximal
nominal stresses obtained by the Risitano
method correspond to the results obtained in
S-N diagrams. As fatigue tests on load frame
have not exceeded 106 cycles, the obtained
results cannot be fully compared, but the trend
of stress concentrator influence is clearly
visible. To make more precise predictions,
reaching 107 load cycles is required.
Figure 15 - Time diagram of mean temperature
for test area of V-notched specimen
Figure 16 - Time diagram of mean temperature
for test area of specimen with 6 mm hole
Figure 18 - Thermal increase vs. load level
increase and linear approximation of V-notched
specimen
9
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
are possible, high frame rates will result
in unnecessary increase in the collected
data. The length of the recorded sequence
depends on the temperature stabilization
period. In thermal diagrams in Figures 4, 1417, the thermal drop before the beginning
of cycling (Figure 15) is caused by initial
tension.
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
Figure 19 - Thermal increase vs. load level
increase and linear approximation of specimen
with hole
Figure 20 - Thermal increase vs. load
level increase and linear approximation of
semicircular notched specimen
During the Risitano method testing only three
specimens ruptured, which is significantly
lower than 23 specimens required for S-N
diagrams that did not provide final results of
maximal nominal stresses. The testing time
required for all specimens evaluated by the
Risitano method was several hours, while
S-N curves required two weeks of load
frame testing.
6.CONCLUDING REMARKS
In this paper an overview of the application
of IR-based methods to estimate fatigue
resistance, stress concentrations and
fatigue strength for metal specimens is
presented. All three described methods, i.e.
the TSA, the Risitano method and recording
of plasticity and crack propagation, are fully
applicable on polymer composites. When
evaluating metals, i.e. materials with high
diffusivity, LW micro-bolometric cameras
can only be used in the Risitano method.
The TSA requires cooled MW camera,
additional Lock-In hardware component, and
corresponding data processing software,
10
which increases the equipment price. These
prices have remained constant over the last
few years. There have been no significant
changes in technology, except that for the
same price a camera with double image
resolution can be obtained. Double image
resolution for the methods addressed here
is not necessary, and the increasing image
resolution decreases the camera frame rate,
which is an important issue. During the last
decade several companies that produced
MW cameras and image processing
software based on Lock-In approach (e.g.
Agema, Cedip) have been bought by bigger
global companies, mostly oriented towards
LW camera market, causing a stagnation of
research and applications in the field of TSA.
Except for some academic research work,
there have been no major steps forward in
industrial applications.
This particular area of research and
development still enables new approaches
and can be of great scientific interest. With
regional stagnation in industrial research
and development, the research in IR-based
methods stagnates as well, which keeps the
prices of MW thermal cameras high.
The TSA enables visualization of stress
field for object surface, thus enabling the
estimation of stress concentrations. When
comparing three addressed specimens,
it can be concluded that the one with
semicircular notch is characterized by the
lowest stress concentration and the highest
fatigue limit. This has been confirmed by
classical fatigue tests, i.e. S-N diagrams.
The results obtained by the Risitano method
correspond to the results of fatigue tests.
Fast cooled MW cameras enable evaluation
of plasticity and crack propagation including
specimen rupture. These observations can
be compared with the TSA, where if the
zone of fracture initialization corresponds
to stress concentration zones, it proves
that the stress concentration is the cause
of rupture. If this is not the case, then the
cause of rupture can be found in material
drawbacks or the machining method.
The TSA, the Risitano method and the
acquisition of plastification and fracture
7.References
[1] Krstulović-Opara, L., Domazet, Ž., Klarin,
B., Garafulić, E.: The Application of IR
Thermography to the NDT and Thermal Stress
Analysis, HDKBR info, no. 6/7, 17-22, 2012.
[2] Krstulović-Opara, L., Klarin, B. , Garafulić, E. and
Domazet, Ž.: Application of gradient based IR
thermography to the GRP structures inspection,
Key Engineering Materials, Vols.488-489, 682685, 2011.
[3] Krstulović-Opara, L. , Klarin, B., Neves,
P., Domazet, Ž.: Thermal imaging and
Thermoelastic Stress Analysis of impact
damage of composite materials, Engineering
Failure Analysis, vol. 18, 713–719, 2011.
[4] Lesinak, J.R., Boyce, B.R.: A high-speed
differential thermographic camera, SEM
conference, 1995.
[5] Lesinak, J.R., Bazile, D.J., Boyce, B.R., Zickel,
M.J.: Stress intensity measurement via infrared
focal plane array, ASTM conference, May 1996.
[6] Haldorsen, L.M.: Thermoelastic stress analysis
system developed for industrial applications,
Ph.D. Thesis, University of Aalborg, Institute of
mechanical engineering, 1998.
[7] Lesinak, J.R., Boyce, B.R., Howenwater, G.:
Thermoelastic measurement under random
loading, SEM conference, June 1998.
[8] Boyce, B.R.: Steps to modern thermoelastic
stress analysis, ATEM Conference, Ube, Japan,
July 1999.
[9] Honlet, M., Boyce, B.R.: Full-field thermoelasticity.
A new generation of an optical method showing
directly effects produced by mechanical strains,
15th WCNDT, Roma, Italy, 2000.
[10] Dulieu-Barton, J.M., Quinn, S.: Thermoelastic
stress analysis of oblique holes in flat plates, Int
J Mech Sci, vol. 41, 527–46, 1999.
[11] Boyce, B., Lesniak, J.: Unique applications of
thermoelastic stress analysis, Spring SEM
conference, 1999.
[12] Lesniak J, Bartel B.: An elevated-temperature
TSA furnace design, Exp Techniques, 20(2):96,
1999
[13] La Rosa, G., Risitano, A.: Thermographic
methodology for rapid determination of the
fatigue limit of materials and mechanical
components, International Journal of Fatigue,
vol. 22, 65-73, 2000.
[14] Fargione, G., Geraci, A., La Rosa, G., Risitano,
A.: Rapid determination of the fatigue curve
by the thermographic method, International
Journal of Fatigue, vol. 24, 11-19, 2002.
[15] Meneghetti, G.: Analysis of the fatigue strength
of a stainless steel based on the energy
dissipation, International Journal of Fatigue, vol.
29, 81-94, 2007.
[16] Minak, G.: On the Determination of the Fatigue
Life of Laminated Graphite-Epoxy Composite by
Means of Temperature Measurement, Journal
of Composite Material, vol. 44, 2010.
[17] Tang-Kwor, E., Matteï, S.: Emissivity
measurements for Nextel Velvet Coating 81121 between -36 °C and 82 °C., High Temp.-High
Press., vol. 33, 551-556, 2001.
[18] Boyce, B.R.: Steps to Modern Thermoelastic
Stress Analysis, ATEM Conference, July 1999,
Ube, Japan,1999.
[19] Pirsić, T. , Krstulović-Opara, L , Domazet, Ž.:
Thermographic Analysis of Stress Distribution in
Welded Joints, The European physical journal.
EPJ Web of Conferences, 6, 07004-p1 - 07004p6, 2010.
[20] Medgenber, J., Ummenhofer, T.: Assessment
fatigue damage in low-carbon steel using
lock-in thermography, 8th Int. Conference on
Quantitative infrared Thermography (QUIRT
2006), June 28-29, Padova, Italy, 2006.
[21] Lin, S.-J., Quinn, S., Matthys, D.R., New,
A.M., Kincaid, I.M., Boyce, B.R., Khaja, A.A.,
Rowlands, R.E.: Thermoelastic Determination
of Individual Stresses in Vicinity of a NearEdge Hole Beneath a Concentrated Load,
Experimental Mechanics, vol. 51, 797-814,
2011.
[22] Cavaliere, P., Rossi, G.L., Di Sante, R., Moretti,
M.: Thermoplasticity for the evaluation of
fatigue behavior of 7005/Al2O310p metal matrix
composite sheets joined by FSW, International
Journal for Fatigue, vol. 30, 198-206, 2008.
[23] Lesinak, J.R., Boyce, B.R.: A High-Speed
Differential Thermographic Camera, SEM
Conference, 1995.
11
APPLICATION OF THERMOGRAPHY IN ANALYSIS OF FATIGUE STRENGTH OF MATERIALS AND STRUCTURES
propagation are reliable approaches to
estimation of fatigue resistance and stress
concentration enabling assessment of
materials and structures. The presented
methods are dynamic, non-destructive
(except
fracture
propagation)
and
non-contact methods. The examples
demonstrated the ability of IR thermography
as a reliable NDT and experimental
mechanics tool.
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG
OPTEREĆENJA KONSTRUKCIJA
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
Lovre KRSTULOVIĆ-OPARA, Fakultet elektrotehnike, strojarstva i brodogradnje, Sveučilište u
Splitu, R. Boškovića 32, HR-21000 Split, www.fesb.hr/kk, [email protected]
SAŽETAK – Termografija, kao nerazorna metoda, ima sve veću primjenu u istraživanjima i industriji.
U radu je prikazana primjena termografije u procjeni koncentracije naprezanja te zamora materijala
i konstrukcija. Na primjerima uzoraka s koncentratorima naprezanja prikazana je primjena termografije u analizi metalnih materijala. U tu svrhu uspoređeni su rezultati klasičnih ispitivanja na umarlici
s tri termografske metode: termoelastičnom analizom naprezanja, Risitanovom metodom te metodom praćenja širenja zone plastifikacije i loma. Termoelastičnom analizom naprezanja na ciklički
opterećenim uzorcima dobiva se raspodjela naprezanja te koncentracije naprezanja na površini materijala. Risitanova metoda na temelju mjerenja porasta temperature ciklički opterećenog uzorka
s porastom opterećenja predviđa dinamičku čvrstoću uzorka. Zbog velike disipacije topline u zoni
plastifikacije i pukotine, brze srednjovalne kamere omogućuju praćenje tijeka plastifikacije i širenja
pukotine. Opisane metode primjerene su za dinamička ispitivanja, nerazorne su i beskontaktne te ne
utječu na rezultate ispitivanja.
Ključne riječi: termoelastična analiza naprezanja, Risitanova metoda, plastifikacija, propagacija pukotine, zamor, cikličko opterećenje
1.UVOD
Infracrvena termografija u širokoj je
primjeni kao nerazorna metoda ispitivanja
materijala, bilo kao pasivna bilo kao
aktivna termografija, o čemu je pisano u
nekim našim prethodnim radovima [1-3].
Aktivna termografija igra značajnu ulogu u
nerazornom ispitivanju kompozita. Pasivna
termografija ima značajnu ulogu u analizi
materijala i konstrukcija, a jedno bitno
područje primjene jest evaluacija pogonske
čvrstoće konstrukcija, točnije određivanje
dinamičke čvrstoće materijala, odnosno
konstrukcija. Termografija je primjenjiva
metoda u analizi loma, dok se u analizi
zamora i procjeni dinamičke čvrstoće može
smatrati nerazornom metodom s obzirom
da je procjenu moguće provesti bez loma
ispitivanog materijala, odnosno uzorka.
Analiza na zamor materijala i konstrukcija
uglavnom
podrazumijeva
razarajuće
ispitivanje uzoraka, odnosno čitavih
segmenata konstrukcija s ciljem utvrđivanja
životnog vijeka dinamički opterećenih
konstrukcija. Otkrivanje i izbjegavanje
koncentracija naprezanja, kao najčešćeg
uzroka otkazivanju konstrukcija, uglavnom
se ograničava na numeričko modeliranje i
simuliranje opterećenja te mjerenje nekom
od metoda eksperimentalne analize
12
naprezanja poput metode elektrootpornih
mjernih traka (tenzometri), fotoelastičnosti
i sl. Realni prikaz stanja raspodjele
naprezanja, odnosno deformacija, na čitavoj
površini ispitivanog objekta teško se dobije.
Tenzometri daju pouzdane informacije
i primjereni su dinamičkim ispitivanjima
konstrukcija u eksploataciji, no manjkavost
im je što očitavaju deformacije samo na
mjestu lijepljena tenzometra. Infracrvena
termografija relativno je novija metoda,
razvoj koje je omogućio razvoj kvalitetnijih
i cijenom pristupačnijih digitalnih detektora.
Ako se razmatraju tipična ispitivanja u
pogonskoj čvrstoći, termografija u okviru
metode termoelastične analize naprezanja
(Thermoelastic Stress Analysis – TSA) [312] omogućuje prikaz raspodjele sume
glavnih naprezanja po čitavoj površini
opterećenog tijela. Utvrđivanje dinamičke
čvrstoće pojedinog materijala moguće je
metodama poput Risitanove metode [13, 14]
ili Meneghettijeve metode [15, 16], temeljene
na disipaciji energije. Ovim metodama
moguće je bitno smanjiti broj potrebnih
uzoraka za ispitivanje, odnosno ispitivanje
se može svesti samo na jedan uzorak, što
nije slučaj kod klasičnog ispitivanja na zamor
koje iziskuje cijeli niz ispitivanja i epruveta.
Slika 1. (vidi strana 4)
Iako su opisane metode u potpunosti
primjenjive na polimerne kompozite,
ovdje će se komentirati samo primjena
na
metalima.
Polimerne
kompozite
karakterizira daleko veća toplinska tromost
(manja toplinska difuzivnost) te je za njihovu
evaluaciju u nekim metodama moguće
koristiti i dugovalne mikrobolometarske
kamere. Zbog svoje velike toplinske
vodljivosti i malog toplinskog kapaciteta
(velika difuzivnost), metale karakteriziraju
brze promjene temperature te su za njihovu
evaluaciju nužne brze hlađene srednjovalne
kamere. Za razliku od mikrobolometarskih
dugovalnih kamera, srednjovalne kamere
omogućuju akvizicije od preko 700 Hz.
Ovo omogućuju detektori koji se temelje na
tehnologiji fotonskog izbijanja, gdje granicu u
brzini akvizicije ne predstavlja sam detektor
nego prebacivanje signala u računalo. Brzi
detektori i pri ovim velikim frekvencijama
opterećenja (20 Hz u korištenim primjerima)
osiguravaju oštre snimke, što kod
mikrobolometarskih kamera nije slučaj.
Kamera korištena u ovdje prikazanim
primjerima je srednjovalna hlađena kamera
Flir SC 5000, rezolucije 320x256 piksela
i osjetljivosti 0,02K. Trenutačno su na
tržištu i kamere dvostruke rezolucije, iste
osjetljivosti, no brzina akvizicije u punoj je
rezoluciji manja. Ograničavanjem kadra
(polja aktivnih piksela kamere) povećava
se brzina akvizicije do vrijednosti preko 700
Hz. U punoj rezoluciji (320x256 piksela)
brzina je akvizicije oko 150 Hz.
1.EVALUACIJA NAPREZANJA
METODOM TERMOELASTIČNOSTI
Još 1850. god. lord Kelvin opisuje
termoelastični efekt, odnosno činjenicu da
pod djelovanjem sila dolazi do promjene
u temperaturi tijela. God. 1915. Compton
i Webster provode prvi eksperimentalni
dokaz, a 1967. Belgen vrši prva beskontaktna
mjerenja [18]. Metoda dobiva na značaju
kada se razvila tehnologija beskontaktnih
mjerenja putem termokamera. Godine 1982.
dobivaju se prvi snimci uređajem Ometron
SPATE 8000, a za akviziciju naprezanja
bilo je potrebno nekoliko sati s obzirom
da se uređaj temeljio na samo jednom
detektoru (diodi) i setu pomičnih zrcala
koja su sinkroniziranim radom omogućivala
prenošenje temperature s cijele površine
uzorka. God. 1994. uređajem Stress Photonic,
odnosno razvojem digitalnih detektora s
nizom piksela, omogućena je akvizicija
raspodjele naprezanja u nekoliko minuta.
13
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
Još je lord Kelvin ustanovio da je
karakteristika elastično deformiranih tijela
da djelovanjem opterećenja dolazi do
promjene temperature, pri čemu vlačno
naprezanje izaziva lokalno pothlađivanje,
a tlačno lokalno zagrijavanje tijela. Na
mjestima gdje su naprezanja veća i ove
su promjene veće. Promjene temperature
za
tipične
konstrukcijske
materijale
poput čelika i aluminija iznose nekoliko
desetinki stupnja Celzija ili Kelvina. Kod
naprezanja i deformacija kod kojih dolazi do
plastičnih deformacija i lomova materijala
temperature su znatno više, nekoliko
desetaka stupnjeva, pa termografija
omogućuje praćenje načina plastifikacije i
širenja pukotine sve do loma konstrukcije ili
uzorka. Navedene metode primjenjive su na
gotovo svim konstrukcijskim materijalima,
a mogućnost primjene uglavnom ovisi o
stupnju emisivnosti površine, što se lako
rješava bojanjem bojama visokog stupnja
emisivnosti (u radu je korištena boja Nextel
Velvet-Coating 881-21 [17], koeficijenta
emisivnosti 0,95, slika 1). U ovom članku
bit će dan pregled tri metode kojima se
omogućuje procjena raspodjele naprezanja,
određivanje dinamičke čvrstoće te praćenje
tijeka plastifikacije i širenja pukotine.
Rezultati će se usporediti s klasičnim
ispitivanjem na zamor u koju svrhu su
aluminijske epruvete (legura Al2024)
dimenzija poprečnog presjeka 20x4 mm
opterećivane vlačno sinusoidno (frekvencija
20 Hz, r=Fmin/Fmax=0). Na epruvetama
su izrezani koncentratori naprezanja u
obliku rupe u sredini promjera 6 mm te u
obliku polukružnog (radijus R3 mm) i V
koncentratora (dubina utora 3mm). Na
mjestu koncentratora površina poprečnog
presjeka za sve je uzorke ista.
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
Osnova
je
metode
jednadžba
termoelastičnosti:
−α T
(σ + σ 2 )
∆T =
ρ Cp 1
,
(1)
gdje je α koeficijent temperaturne ekspanzije,
T sobna temperatura uzorka, ρ gustoća, Cp
toplinski kapacitet pri konstantnom tlaku, a
σ1 i σ2 glavna naprezanja. Uzme li se da su
koeficijenti α, T, ρ i Cp za jedan promatrani
uzorak konstantni, jednadžba (1) daje
izravnu vezu između prirasta temperature
i invarijante naprezanja (suma glavnih
naprezanja, gdje je na površini tijela σ3=0).
Jednadžba (1) vrijedi samo za adiabatsko
stanje (nema dovođenja ili odvođenja
topline), što nije moguće postići, no ako su
promjene naprezanja dovoljno brze (oko 10
Hz) zadovljen je uvjet adiabatičnosti. Dakle,
potrebna je brza hlađena srednjovalna
kamera, uzbuda od približno 10 Hz (iako
su moguće i uzbude od 3 Hz), te dovoljni
iznos energije (naprezanja) da bi detektor
zabilježio učinak. Uzbuda može biti
magnetno polje, ultrazvuk i dinamičko
opterećenje što je ovdje slučaj. Promatra
li se dinamički opterećeni uzorak (slika 1)
pri frekvenciji uzbude od 20 Hz, vide se
uzastopni toplinski bljeskovi (slika 2). Na
mjestima gdje su naprezanja veća, veći su i
toplinski bljeskovi. Slika 2 prikazuje snimak
vlačno dinamički opterećenog uzorka, pri
čemu hladnije zone predstavljaju mjesta
s većim vlačnim naprezanjem. Kako je
frekvencija kamere namještenja na 50 Hz
(kamera omogućuje i veće frekvencije), niz
slika upravo demonstrira problem da je teško
kamerom zabilježiti trenutak maksimalnih
naprezanja.
Slika 2. (vidi strana 5)
I kada bi se snimilo maksimalno naprezanje,
korištenjem jednadžbe (1) dobila bi se
prevelika odstupanja od realnih iznosa
naprezanja. U cilju kvalitetnog računanja
sume glavnih naprezanja potrebno je
koristiti hardversku komponentu, tzv.
Lock-in, kojom se vrši spajanje na signal
uzbude (mjerna doza kidalice), te se uz
softversku obradu cijelog niza snimaka vrši
obrada, a korištenjem jednadžbe (1) dobiva
14
raspodjela naprezanja na površini tijela.
Slika 3 prikazuje primjer ispitne epruvete
kutnog zavara [19], gdje je na prvom
termogramu neobrađeni snimak kamere,
a drugi termogram predstavlja obradu uz
pomoć Lock-in hardverske komponente.
Slika 3. (vidi strana 6)
Iako vrlo pouzdana metoda, TSA se relativno
rijetko koristi te je vrlo malo objavljenih
radova na primjerima primjene TSA. Razlog
je tomu što je nužno ostvariti promjenjiva
naprezanja, što ta naprezanja moraju biti
dovoljnog iznosa da bi IC kamera zabilježila
učinke i što je metoda ograničena na skupe
srednjovalne hlađene kamere. Primjeri
primjene metode mogu se pronaći u
referencama [6,20-23]. Metoda je nerazorna
i predstavlja tzv. „Full field method”, metodu
punog polja koja omogućuje vizualizaciju
raspodjele naprezanja po površini. Slična je
metodi fotoelasticimetrije, s razlikom da je
rezultat suma glavnih naprezanja.
2.ODREĐIVANJE DINAMIČKE
ČVRSTOĆE RISITANOVOM
METODOM
Risitanova metoda [13, 14] temelji se na
činjenici da prilikom započinjanja cikličkog
opterećenja uzorka dolazi do blagog
rasta temperature. Porast se nakon par
ciklusa stabilizira te temperatura ostaje
konstantna sve do loma, zanemari li se
rast temperature cijelog mjernog sustava.
Neposredno pred lom temperatura naglo
raste. Slika 4 prikazuje, za slučaj trokutnog
koncentratora, porast temperature na
početku cikliranja te nagli skok temperature
neposredno pred lom (slučaj opterećenja
od 4 kN). Efekt je sličan efektu kad se
ciklira uzorak u umaralici pri ispitivanju na
zamor, gdje prvih par ciklusa u dijagramu
sila-pomak
(naprezanje-deformacija)
postoji histereza koja nakon par ciklusa
iščezava te se pojavljuje neposredno pred
lom. Za razliku od klasičnog ispitivanja
gdje je potrebno slomiti čitav niz epruveta,
Risitanova metoda omogućuje ispitivanje
na samo jednom uzorku, gdje se za zadane
Slika 4. (vidi strana 7)
Slika 5. (vidi strana 7)
3.EVALUACIJA TIJEKA
PLASTIFIKACIJE I ŠIRENJA
PUKOTINE
Pri elastičnim deformacijama vlačna
naprezanja izazivaju pad temperature, a
tlačna rast temperature prema jednadžbi
(1). U plastičnom području zbog tečenja
materijala i znatnog oslobađanja toplinske
energije (nekoliko desetaka stupnjeva),
IC kamerom moguće je zabilježiti proces
plastifikacije uzorka. Za materijale s velikim
toplinskim kapacitetom i malom vodljivosti
(niska difuzivnost) moguće je korištenje
dugovalnih mikrobolometarskih kamera. Za
metale nužne su brze hlađene srednjovalne
kamere. Na slikama 6-8 niz termograma
prikazuje zonu početka tečenja te širenje
pukotine sve do loma epruvete. Razlika u
temperaturi između gornje i donje polovine
epruvete uslijed je toplinskog toka između
donje toplije čeljusti (spojena na hidraulički
klip) i gornje hladnije čeljusti (spojena na
mjernu dozu).
Slika 6. (vidi strana 7)
Slika 7. (vidi strana 7)
Slika 8. (vidi strana 7)
4.USPOREDBA METODA
S KLASIČNIM PRISTUPOM
ODREĐIVANJU DINAMIČKE
ČVRSTOĆE
U cilju prikaza mogućnosti termografije
u procjeni zamora provedeno je klasično
ispitivanje na zamor epruveta sa slike 1.
S-N dijagrami, odnosno iznosi sinusoidnog
vlačnog naprezanja prema broju ciklusa do
loma prikazani su u logaritamskom mjerilu
slikama 9 - 11. Oznakama „x” u dijagramima
označava se lom, a crvenim oznakama
prikazane su usrednjene vrijednosti za slučaj
kad je nekoliko epruveta ciklirano s istim
iznosom opterećenja. Frekvencija cilkiranja
na servo-hidrauličkoj pet tonskoj dinamičkoj
kidalici (umaralici) Instron 8800 50kN je
iznosila 20Hz. Zbog dostupne količine
uzoraka nisu za sve iznose opterećenja
provedena uobičajena tri ispitivanja na lom,
no dijagrami pokazuju trend i usporedivi su
s kasnijim rezultatima opisanih IC metoda.
Slika 9. (vidi strana 8)
Slika 10. (vidi strana 8)
Slika 11. (vidi strana 8)
Termoelastičnom analizom naprezanja
dobiva se raspodjela naprezanja na
uzorcima s trokutnim, polukružnim i
kružnim koncentratorima. Slika 12 prikazuje
raspodjelu naprezanja za maksimalni iznos
opterećenja od 8 kN (odgovara naprezanju
143 MPa). Skala naprezaja pokazuje da se
maksimalna naprezanja javljaju za trokutni
koncentrator (94,26 MPa), dok polukružni
koncentratori imaju najmanju razinu
15
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
priraste opterećenja IC kamerom bilježe
prirasti u temperaturi uzorka. Pri tom
do loma epruvete ne mora nužno doći.
Iz trenda porasta i činjenice da se traži
naprezanje pri kojem porasta nema, slijedi
dinamička čvrstoća materijala odnosno
ispitnog uzorka ili dijela konstrukcije.
Metoda je jednostavna i primjenjiva
na
dugovalnim
mikrobolometarskim
kamerama. Kod primjene na preciznijim
hlađenim srednjovalnim kamerama, zbog
veće osjetljivosti, kamera bilježi sinusoidne
skokove temperature te je potrebno
zaglađivanje krivulje kako bi se lakše očitali
podaci. Gornji dijagram na slici 5 prikazuje
signal dobiven kao srednju vrijednost
očitanja u području koncentratora. Donji
dijagram na slici 5 predstavlja obradu
signala (filtriranje) s ciljem lakšeg očitanja
porasta temperature. Toplinski skokovi
na gornjem dijagramu slike 5 toplinski su
bljeskovi prikazani slikom 2. Potreba za
ovakvom obradom podataka ne postoji kod
dugovalnih kamera s obzirom da kamere
ne uspijevaju zabilježiti kolebanje topline,
kako radi osjetljivosti, tako radi frekvencije
akvizicije i tehnologije detektora.
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
naprezanja, što je u skladu s rezultatima S-N
dijagrama gdje se vidi da najnižu dinamičku
čvrstoću ima trokutni kondenzator. Okrugli
koncentrator (rupa u sredini) ima nešto
nižu dinamičku čvrstoću od polukružnih
koncentratora, što odgovara maksimalnim
očitanim naprezanjima na slici 12, odnosno
48,87 MPa za rupu u sredini, prema 42,97
MPa za polukružne koncentratore.
Slika 12. (vidi strana 8)
Pri većem je opterećenju termoelastični
učinak izraženiji, što ukazuje na činjenicu da
nije samo dovoljno postići frekvenciju, već
treba postići i određeni iznos naprezanja
kako bi se termoelastični učinak uočio. Na
slici 13 nije prikazan trokutni koncentrator
jer je već pri iznosima opterećenja od 16
kN (286 MPa) došlo do loma epruvete s
trokutnim koncentratorom.
Slika 13. (vidi strana 9)
Risitano metoda se sastoji u snimanju
temperature uzorka koji se ciklira na umaralici
(kidalici). Na slici 14 prikazan je dijagram
srednje temperature ispitnog pravokutnog
polja za 6000 ciklusa sinusoidnog
opterećenja frekvencije 20Hz. Frekvencija
snimanja kamere iznosila je 50 Hz. Iako
su moguće veće frekvencije snimanja, za
ovu vrstu analize za to nema potrebe jer
bi količina podataka bila prevelika. Period
dužine snimanja se odabire na način da
dođe do stabilizacije porasta temperature.
Na dijagramima temperatura (slike: 4, 1417), pred sam početak sinusoidnog cikliranja
(slika 15) vidljiv je pad temperature. Do pada
temperature nastaje prelaskom iz nultog
opterećenja u vlačno opterećenje cikliranja,
koje zbog prije opisanih razloga izaziva pad
temperature.
Početna temperatura ispitivanja određena
je lokalnim temperaturnim uvjetima u
laboratoriju i nije bitna za metodu ispitivanja
jer se prati samo porast temperature obzirom
na porast opterećenja. Na svim dijagramima
vidljivo je da je porast temperature veći
za veće iznose opterećenja. Sam lom
karakterizira nagli skok u temperaturi, nakon
kojeg slijedi hlađenje slomljenog uzorka, što
više nije predmet ispitivanja.
Slika 15. (vidi strana 9)
Slika 16. (vidi strana 9)
Slika 17. (vidi strana 9)
Dijagrami na slikama 18-20 predstavljaju
temperaturne priraste očitane s dijagrama na
slikama 15-17. Linearnom aproksimacijom
definiran je pravac čije sjecište s nultim
porastom temperature predstavlja dinamičku
čvrstoću koja za trokutni koncentrator iznosi
44 Mpa, za provrt u sredini 123 MPa, a
za polukružni koncentrator 126 MPa. Ovo
odgovara usporedbi iznosa maksimalnih
naprezanja dobivenih TSA metodom za
isti stupanj opterećenja (slika 12), gdje
je maksimalno naprezanje za trokutni
koncentrator 94 MPa, za rupu u sredini 49
MPa, a za polukružni koncentrator 43 MPa.
Uvrste li se vrijednosti dinamičke čvrstoće
dobivene Risitanovon metodom u S-N
dijagrame (slike 9-11), iznosi dinamičkih
čvrstoća
odgovaraju
očekivanim
vrijednostima iz S-N dijagrama. U klasičnim
ispitivanjima umaralicom broj cilkusa
uglavnom nije nadilazio milijun ciklusa (106
ciklusa), no trend je vidljiv. Za preciznije
određivanje dinamičke čvrstoće trebalo je
provesti ispitivanja reda veličine 107 ciklusa.
Slika 18. (vidi strana 10)
Slika 14. (vidi strana 9)
Slika 19. (vidi strana 10)
Temperaturni dijagrami na slikama 15-17
prikazuju snimanje temperaturnog porasta
za 6000 ciklusa opterećenja i razne stupnjeve
sinusoidnog opterećenja frekvencije 20
Hz, pri čem je odnos ekstrema opterećenja
r=Fmin/Fmax=0.
Slika 20. (vidi strana 10)
16
Ono što je bitno jest da su se Risitanovom
metodom polomile samo tri epruvete, što je
daleko manje od priloženih S-N dijagramima
gdje su polomljene 23 epruvete, s tim da
5.ZAKLJUČAK
U prethodnim poglavljima dan je pregled
primjene
termografije
kod
procjene
zamora i pogonskih opterećenja metalnih
konstrukcija. Sve tri opisane metode; TSA,
Risitanova metoda te praćenje propagacije
plastifikacije i pukotine, u potpunosti su
primjenjive kod kompozitnih materijala. Za
slučaj metala, odnosno materijala velike
difuzivnosti, dugovalne mikrobolometarske
kamere jedino se mogu primijeniti u
Risitanovoj metodi. Za TSA metodu
potrebno je uz hlađenu srednjovalnu
kameru imati i hardverski Lock-in dodatak
te pripadajući softver, što sve dodatno
poskupljuje
cijenu
opreme.
Prateći
cijene na tržištu nema vidljivih pomaka u
tehnologiji dostupnih srednjovalnih kamera,
osim u dvostrukoj rezoluciji. Dvostruka
rezolucija za opisane metode nije bitna
s obzirom da se dvostrukom rezolucijom
gubi brzina akvizicije (frekvencija kamere).
Cijene opreme u posljednjih se desetak
godina nisu promijenile, odnosno ostale su
iste. Kupnjom tvrtki koje su razvijale ovu
vrstu srednjovalnih kamera i pripadajućih
softverskih aplikacija (Agema, Cedip) od
strane multinacionalnih tvrtki orijentiranih
ka tržištu dugovalnih mikrobolometarskih
kamera došlo je do zastoja u razvoju
softvera i metoda mjerenja. Osim usamljenih
znanstvenih radova uglavnom nema većih
pomaka u industrijskoj primjeni.
Ovo je područje vrlo široko i još dovoljno
neistraženo te ima smisla i dalje istraživati
mogućnosti razvoja opisane metode.
Opadanjem istraživanja i primjene u
industriji šire regije došlo je do usporavanja
tempa razvoja opisanih metoda, što drži
tržište srednjovalnih kamera ograničenim, a
time cijene opreme ne padaju.
TSA metoda omogućuje prikaz raspodjele
sume glavnih naprezanja po površini te
time i procjenu koncentracije naprezanja.
Usporedbom triju uzoraka zaključuje se
da uzorak s polukružnim koncentratorom
ima najmanje naprezanje, a samim time i
najveću dinamičku čvrstoću, što potvrđuju
i klasična ispitivanja na zamor. Isto vrijedi
i za Risitanovu metodu kojom su se, uz
znatnu uštedu vremena i broja uništenih
uzoraka, dobila rješenja koja se također
podudaraju s klasičnim ispitivanjima na
zamor. Brze hlađene srednjovalne kamere
omogućuju i dobro praćenje širenja zona
plastifikacije te nastanka pukotine i loma.
Prikazom posljednjih kadrova neposredno
pred lom može se odrediti gdje nastaje
inicijalna pukotina te je usporediti s TSA.
Ako se lokacije poklapaju, koncentracija
naprezanja uzrok je loma, a ako se ne
poklapaju, razlog lomu treba tražiti u
greškama materijala i obradi uzoraka.
TSA, Risitanova metoda i praćenje
plastifikacije pouzdani su pristupi u
procjeni zamora i koncentracije naprezanja
konstrukcija. Metode su dinamičke,
nerazorne (s iznimkom praćenja loma) i
beskontaktne. Uz navedene metode, kao
i ostale metode primjene termografije za
nerazorna
ispitivanja, termografija se
dokazala kao pouzdana i primjenjiva metoda
eksperimentalne analize naprezanja.
17
PRIMJENA TERMOGRAFIJE U ANALIZI POGONSKOG OPTEREĆENJA KONSTRUKCIJA
dinamička čvrstoća nije određena zbog
nedovoljnog broja podataka i što se samo
za polukružni koncentrator poštovalo
pravilo od barem tri epruvete za jednu
razinu opterećenja. Vrijeme ispitivanja
za Risitanovu metodu iznosilo je par sati,
dok je za klasično umaranje na umaralici
potrošeno dva tjedna rada kidalice (kidalica
nije bila stalno opsluživana).
18
ENGINE MONITORS for GENERAL AVIATION
PISTON ENGINES CONDITION MONITORING
ABSTRACT – Classical engine gauges give very basic information about engine operation and condition. With graphical engine monitors is now possible to have substantially
more diagnostic information available in a timely and usable manner. This information
may provide better and more efficient engine operation. It can also detect most impeding
engine problems.
Keywords: engine monitor, aircraft, piston engine, general aviation
1. INTRODUCTION
Vast majority of general aviation aircrafts
(popularly known as small private airplanes)
are powered by gasoline piston engines. The
main source of engine information available
to pilot are several gauges indicating
cylinder head temperature (CHT), exhaust
gas temperature (EGT), engine rotational
speed (RPM, tachometer), fuel flow, oil
temperature and oil pressure, Figure 1.
These gauges give very basic information
about engine condition. E.g., single CHT
and EGT gauge gives an average of
each cylinder’s head and exhaust gas
temperature. Engine monitor, [1], [2],
replaces this older method of viewing of
only one temperature at time with precise
multi- cylinder engine monitoring of EGT
and CHT
less important parameters. Such engine
monitors cover much more engine data then
basic gauges in a cockpit (about dozen of
parameters that are also recorded and can
be analyzed later). By monitoring engine
parameters it is possible to detect minor
engine problems before they become large
ones. This device augments diagnostic
possibilities
of
classical
boroscope
inspection, engine oil analysis and magnetic
chip detector (detection of metal particle –
engine debris).
2. AIRCRAFT PISTON ENGINE
Piston engine is a heat engine designed to
convert energy into rotational mechanical
motion. It uses reciprocating pistons to
convert pressure into a rotating motion.
Typical main four strokes of the petrol
internal combustion engine are intake,
compression, power and exhaust strokes,
as shown in Figure 2. Piston aircraft engine
is not very efficient at converting energy
contained in a fuel to a mechanical
energy, Figure 3.
Figure 1 Classical gauges for monitoring
of aircraft piston engine (CHT, EGT, RPM rotation speed, FF - fuel flow, oil temperature
and oil pressure)
temperature plus myriad of other more or
Figure 2 Four strokes of the petrol engine
19
ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
Dubravko MILJKOVIĆ, HEP, Zagreb, CROATIA, Phone: (1)6113032; [email protected]
ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
engine can be run at temperatures that will
significantly reduce the life of some of its
parts and there is no automatic system or
computer to prevent or limit engine damage,
[5]. Excessive EGTs and/or CHTs cause
engine damage on a regular basis.
2. GRAPHICAL ENGINE MONITOR
Figure 3 Distribution of energy contained in
fuel in a piston engine, adopted from [3]
Only about one-third of the energy contained
in Avgas is converted into useful energy to
the propeller, [3]. Roughly half the fuel’s
energy is wasted out the exhaust pipe (if no
turbocharger is provided). The remaining
one-sixth is transferred to the cooling air
passing over the cylinder fins and through
the oil cooler.
Quality of the combustion process can be
assessed by monitoring the temperatures
of exhaust gases. Diminished efficiency of
the combustion process indicates various
engine problems like low compression, nonuniform fuel distribution, faulty ignition, and
clogged injectors, [4].
An aircraft engine, as one shown in Figure
4, does not have a detonation detector,
oxygen sensor or a computer to control
timing or fuel/air mixture based on throttle
position, temperatures, detectors or sensor
inputs (FADEC equipped aircraft piston
engines are still very rare). If a pilot
chooses, an aircraft
Figure 4 Lycoming IO-320 (four cylinder fuel
injection engine commonly used on
Cessna 172 aircraft)
20
Engine monitor is advanced and accurate
piston engine-monitoring instrument that
improves the pilots understanding of engine
operation, [1-5]. Temperatures are shown
graphically as bars on the display of an
engine monitor, Figure 5. Each column
in the bar on a display is composed of
a stack of segments. The total height of
each column represents the EGT while the
missing segment in the column represents
the CHT. In addition to graphically displaying
EGT and CHT temperatures, the instrument
continuously
displays
Turbine
Inlet
Temperature (TIT) on turbocharged engines.
Figure 5 Engine monitor with bar graph
display (Insight Avionics, older GEM 603)
For twin engine aircraft special variants
of engine monitors are developed
that simultaneously monitor and show
parameters of both engines on a display
of a single instrument, [6], Figure 6. New
products often have color display with
separate columns for EGT and CHT, [7],
Figure 7. Monitored engine
Figure 6 Engine monitor with bar graph
display for twin engine aircraft (JPI EDM 760)
% HP
% Horse Power
MAP
Manifold
Pressure
RPM
Revolutions
Per Minute
TIT
Turbine Inlet
Temperature
EGT
Exaust Gas
Temperature
CHT scale
It must be measured separately as it is
not simple function of separate EGTs.
Temperature probes are illustrated in
Figures 8-10, and its mounting in Figure
11.
CHT
Cylinder Head
Temperature
Cylinder I.D. box indicates which
cylinder temperatures are shown
in the digital display
Figure 7 Engine monitor with separate bars
for EGT and CHT (JPI EDM 830)
Figure 8 CHT Probe
parameters (available in JPI EDM 830)
are shown in Table 1. Similar parameters
are also available in other modern engine
monitors
Table 1 Monitored engine parameters
(JPI EDM 830)
Parameter
EGT
CHT
Description
Exhaust Gas Temperature
Cylinder Head temperature
OIL TEMP
Oil Temperature 1
OIL PRES
Oil Pressure 1
TIT 1
TIT 2
OAT
IAT
CRB
Turbine Inlet Temperature 11
Turbine Inlet Temperature 2 1
Outside Air Temperature
Compressor Discharge
Temperature 1
Intercooler Air Temperature 1
Carburetor Air Temperature 1
CDT - IAT
Intercooler cooling
CDT
RPM
Rotations Per Minute
MAP
Manifold Pressure
% HP
% Horse Power
CLD
CHT Cooling Rate 2
DIF
EGT Span 3
FF
Fuel Flow 1
1
optional, 2fastest cooling cylinder, 3difference
between the hottest and coolest EGT
Separate
temperature
probes
are
implemented for each cylinder. Cylinder
Head Temperature probe is fitted to the
cylinder head’s thermowell. Exhaust Gas
Temperature is measured with a probe that
penetrates the exhaust stack a few inches
from the cylinder. Turbine inlet temperature
is measured by a probe mounted in the
exhaust inlet leading to the turbocharger.
Figure 9 EGT Probe
Figure 10 TIT Probe
Figure 11 Mounting of temperature probes,
adopted from [4]
3. OPERATING MODES
Engine monitor typically has monitoring
and lean operation mode.
3.1. MONITORING MODE
In monitoring mode there is percentage
view and normalized view, [1, 4-8]. Percentage view easily discerns EGT differences across all cylinders. In normalized
view EGT temperatures are displayed with
all column peaks initially set to the same
half-height. This is useful for trend analysis
as it is possible to compare current engine
operation to prior engine operation.
21
ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
EGT scale
3.2.
LEAN OPERATION MODE
ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
Leaning is a process of adjusting fuel/air
ratio, [1], [2]. Adjusting the mixture is
necessary
combustion diagnosis and monitoring of
all critical temperatures. Data shown on
a display help diagnose mixture, timing,
compression, oil consumption and other
engine phenomena that can be used for
early detection of engine problems.
Documentation
accompanying
engine
monitors, [1, 4, 6-8], gives advices what to
verify (e.g. uniform rise in EGT with application
of mixture) and what to be alert for (e.g. high
or uneven EGT or CHT, cooling rate CLD)
for various flight phases of operation: Taxi
Run up Take off, Climb and Full Throttle
Operation, Cruise (leaning) and Descent.
Figure 12 Various relationships between the
mixture, fuel flow and engine power, adopted
from [4]
because during the flight engine operates
at various altitudes and corresponding air
pressures. It restores a significant amount of
engine power and hence improves aircraft
performance. Leaning process can be
performed by monitoring EGT temperature.
As the mixture is leaned, EGT rises to a
peak temperature and then drops as the
mixture is further leaned, [1, 4-8], Figure
12. The best operating mixture for aircraft
engines is in the vicinity of this peak (lean of
peak or rich of peak). Engine monitors are
equipped with the leaning find mode that
helps identify the first cylinder (in case rich
of peak) or last cylinder (if case lean of peak)
to reach peak EGT during a leaning process.
When this mode finds the leanest cylinder it
is not necessarily the hottest cylinder, but
the cylinder that has peaked, [4], [6], [7].
In all flight phases pilot must strictly observe
the red-line temperature limits imposed for
CHT, EGT and TIT during takeoff, climb and
high-performance cruise power operation,
[9]. Engine monitors have custom predefined
(but also custom adjustable) alarm limits set
to encompass all flight regimes, Table 2.
Values for alarm limits are determined from
engine producer documentation. Default
alarm limits are set to encompass all flight
regimes. When a parameter falls outside
of its normal limits, the digital display will
flash with the value and abbreviation of the
alarming item.
4.1.
SHOCK COOLING
Shock cooling is an excessively rapid
decrease in temperature of cylinders that
may happen during descent with idle
engine power setting. Damage from shock
cooling often manifests itself as stuck
valves and cracked cylinders. By observing
CLD parameter it is possible to operate an
engine in a fashion that avoids rapid cooling
of cylinder and associated damage.
Table 2 Default Engine Monitor Alarm Limits
Measurement
CHT
4. COMON FAULTS DIAGNOSTICS
Engine monitor is useful during all flight
phases. Its benefits are apparent to pilots
even while aircraft is still on a ground (during
taxi, run up and take off). Benefits include
22
OIL
TIT
CLD
DIF
MAP
Default Low
Limit
90 °F 32 °C
Default High
Limit
450 °F 230 °C
230 °F 110 °C
1650 °F 00 °C
-60 °F/min -33
°C/min
500 °F 280 °C
32 inch Hg
DIAGNOSTIC FAULT PATTERNS
Engine diagnostic charts in accompanying
documentation contain examples of
various bar patterns shown on a display
and corresponding symptom, probable
cause and recommended action that can
help diagnose and solve engine problems.
Patterns shown in Figures 13 and 14
illustrate just two engine problems. There
are about 15 bar graph patterns in diagnostic
charts, [1, 4, 6-8].
• Decrease in EGT of one cylinder may be
caused by intake valve not opening fully
or faulty valve lifter
5. CONCLUSION
The graphic engine monitor is the essential
tool for modern engine management. It
improves the pilot’s understanding of engine
operation and removes guesswork from
engine management.
Figure 15 Example from engine monitor log
50%
Figure 13 Intake valve or valve filter
• EGT and CHT are not uniform in case of
dirty fuel injectors or fouled plugs
50%
Figure 14 Dirty fuel injectors or fouled plugs
4.3.
DATA LOGGING
Engine monitor automatically records
engine parameters during each flight.
Example of one part of engine log (raw
data) is shown in Figure 15. Recorded data
can be downloaded with cable, wireless
connection or memory card for later analysis
using software, [10], installed on a PC for
sophisticated graphical analysis as illustrated
in Figure 16. This also includes plotting
the trends of user selected measurements
and generating flight summary. Analysis
software may also include engine monitor
simulator that simulates operation of engine
monitor display based on engine data
logged in previous flights. Suspicious data
logs can be sent to a mechanic or engine
manufacturer for further clarification.
Figure 16 Graphical representation of engine
parameters during one flight. Upper curves
show main data (EGT, CHT, TIT), lower curves
show optional data (CLD, OILT, FF, RPM, MAP)
Simultaneously it increases reliability of piston engine, flight safety and operational economics. With its diagnostic capabilities many
impeding failures can be detected. Engine
leaning with built in leaning find function is
crucial for optimum performance with benefits in improved fuel economy, reduced maintenance costs, and extended engine life.
6.REFERENCES
1. Graphic Engine Monitor Data Logging System, Insight
Avionics, USA, 1995 | 2. Bush M., EGT Myths Debunked,
Cirrus Pilot, Vol. 5, No. 7, July/August 2010 | 3. Bush M.,
Understanding CHT and EGT, Cessna Pilots Association,
April 2009 | 4. Pilot’s Guide: Engine Data Management,
EDM-700, EDM-800, EDM-711 Primary, J. P. Instruments,
California, USA, 2007 | 5. Roberts R., The Pilot’s Manual
for Leaning and Diagnosing Engine Problems, Electronic
International, Oregon, USA, 2004 | 6. Pilot’s Guide EDM760 Twin, JPI, California, USA, 2005 | 7. Pilot’s Guide EDM730, EDM-830, EDM-740, JPI, California, USA, 2005 | 8.
Ultimate Bar Graph Engine Analyzer (UBG-16) Operating
Instructions, Electronic International, Oregon, USA, 1997
| 9. Lycoming Operators Manual, Lycoming, USA, March
1973 | 10. Pilot’s Guide, EzTrends, J. P. Instruments, 2006
23
ENGINE MONITORS for GENERAL AVIATION PISTON ENGINES CONDITION MONITORING
4.2.
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA
PLINSKIH TURBINA GT 24/GT26
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Petar Smiljanić, ALSTOM HRVATSKA, Karlovac, Hrvatska
Ivan Smiljanić, Hrvatsko društvo za kontrolu bez razaranja, Zagreb, Hrvatska
SAŽETAK
Ispušno kućište, koje je dio kombiniranog sustava plinskih turbina GT 24 i GT
26, zaštićeno je od visokih temperatura posebnom oplatom. Oplata je izrađena
od limova austenitnog čelika koji se spajaju „montažnim” zavarenim spojevima.
Takvi zavareni „V”-spojevi moraju biti redovito kontrolirani zbog visokih radnih
temperatura kućišta i dinamičkih naprezanja kojima su podvrgnuti tijekom rada.
Na određenim pozicijama ti spojevi nisu dostupni s obiju strana, nego samo s
„čeone”, te se stoga mogu ispitivati samo ultrazvučnom metodom. Osim problema
dostupnosti zavara javlja se i problem grubozrnate strukture zavarenog spoja,
odnosno anizotropnosti ispitivanog materijala što otežava ispitivanje. Ultrazvučno
ispitivanje u ovakvim uvjetima zahtijeva poseban pristup, kao i posebnu dodatnu
opremu (etalone), što je detaljnije objašnjeno u ovom radu.
1. UVOD
Slika 1. Kombinirani proces plinske turbine GT 24 /GT
Plinske turbine GT 24, odnosno GT 26 (sl. 1) dizajnirane su kako bi mogle djelovati u
kombiniranom procesu koristeći prirodni plin kao primarno gorivo. Dio takvog kombiniranog
sustava, koji se nalazi između kućišta turbine i ispušnog difuzora, jest ispušno kućište.
Njegova je funkcija usmjeravanje ispušnih plinova iz niskotlačnog dijela turbine u ispušni
difuzor, pri čemu također podupire i montažu krajnjeg ležaja turbine. Kućište je podijeljeno
na gornju i donju polovicu, a obje se sastoje od vanjskog i unutarnjeg kućišta povezanih
izoliranim rebrima (sl. 1). Osnovna struktura zaštićena je od vrućih ispušnih plinova (preko
600 °C) oplatom kućišta ispod koje je izolacija za zaštitu kućišta od pregrijavanja te zbog
izbjegavanja gubitka toplinske energije sadržane u ispušnim plinovima.
24
Predmet ultrazvučnog ispitivanja u ovom su slučaju „montažni” zavareni spojevi s podložnom
trakom kanala i poklopaca kanala oplate ispušnih kućišta GT 24 /GT 26. Oplata je izrađena
od limova debljine 8 +/- 0,5 mm, a materijal je X 6 CrNiTi 18/10 (austenit). Oplata je
podvrgnuta visokim dinamičkim naprezanjima i vrlo visokim temperaturama, što su otežani
radni uvjeti, te se radi toga provodi ispitivanje u svrhu otkrivanje grešaka neprovarenog
korijena, nepotpunog protaljivanja osnovnog s dodatnim materijalom (greška naljepljenja),
zarobljenog oksida na skošenjima pripreme te pukotina u tijeku izrade i kasnije u tijeku
eksploatacije. Te greške su one koje je zapravo moguće detektirati ovom metodom, odnosno
tehnikom ispitivanja, s obzirom na specifične uvjete pod kojima se ispitivanja i provode.
Treba obratiti pozornost na dvije činjenice pri ovakvom ispitivanju. Prva je ta da je ispitivani
materijal austenitni čelik koji je anizotropan, te koji svojom grubozrnatom strukturom
ograničava prolaz ultrazvučnih valova kroz materijal zbog raspršenja velikog dijela energije
tih valova. Dok je gubitak ultrazvučne energije kroz osnovni materijal (koji je gotovo izotropan)
vrlo mali, dendritna struktura samog zavarenog spoja znatno pogoduje većim gubicima.
Razlika takvih gubitaka između osnovnog materijala i zavarenog spoja u ovom slučaju iznosi
oko 75%. Iz toga razloga potrebno je pomno odabrati vrstu sonde, kao i njezinu frekvenciju
(odnosno valnu duljinu valova kojima se ispituje grubozrnata struktura), a treba voditi računa
i o vrstama grešaka, odnosno njihovim lokacijama, koje se u takvom slučaju mogu detektirati
(problem detekcije grešaka unutar samoga spoja). Drugi problem ovog ispitivanja proizlazi
iz činjenice da je riječ o montažnim zavarenim „V”-spojevima koji su fizički dostupni samo s
jedne strane (čeone).
Naša iskustva pokazuju da je za provedbu ispitivanja dobro koristiti sljedeće norme:
-
za ultrazvučno ispitivanje zavarenih spojeva - EN 1714
- za ultrazvučne razine ispitivanja - EN 1712
- za karakterizaciju grešaka - EN 1713
- za kriterij prihvatljivosti - ISO 5817
25
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Slika 2. Ispušno kućište turbine: 1 - izolacija, 2 - osnovna struktura, 3 - oplata
2. PROVEDBA ISPITIVANJA
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
2.1. Ispitivano područje
Slika 3. Skica zavara oplate
Zahtjev za ispitivanje je sljedeći: ispituju se „V”-zavareni spojevi s nadvišenjem br. 1 i br. 2
(sl. 3) kanala 1 ÷ 10 (ukupno 20 zavara) te zona utjecaja topline po 10mm sa svake strane
zavarenog spoja. Kao što je i u uvodu naznačeno, osnovni je materijal austenitni lim debljine
8 +/- 0,5 mm. Kvaliteta površine mora biti takva da omogući pouzdano ispitivanje te se radi
toga u području skeniranja trebaju odstraniti sve nečistoće: prskanje dodatnog materijala,
ostaci toplinske obrade, neravnine i slično.
Detaljnije skice presjeka rebra, kao i ispitivanog područja dane su na slikama 4 i 5.
Slika 4. Rebro, presjek (crvenom oznakom naznačeno je zumirano područje koje prikazuje slika 5)
26
2.2. Postupak ispitivanja
Ispitivanje će se provesti prema EN 1714 [4] – metoda 3, koja definira osjetljivost ispitivanja.
Oprema koja se koristi za izvedbu ovog ispitivanja je sljedeća:
- ultrazvučni aparati s mogućnosti podešavanja frekvencija 1 ÷ 10 MHz, vertikalnom
linearnošću u granicama +/- 2 dB i horizontalnom linearnošću < 2%
- ispitna sonda MWB 70, frekvencije 4 MHz
- kontaktno sredstvo: gel ZG-F ili ulje
- etaloni:
• K2 – za baždarenje mjernog područja prema normi EN 27963 [1]
• EGH 1 – za određivanje osjetljivosti ispitivanja, izrađen prema zahtjevu iz EN
1714 [4] (sl. 6)
– materijal ovog etalona istovjetan je kao i ispitna pozicija (X6 CrNiTi 18/10)
– sadrži središnji reflektor of 1 mm te reflektor od 2 mm (dio skošenja pripreme
zavara)
• EGH 2 – etalon za karakterizaciju indikacija, s provarenom podložnom trakom (sl. 7)
• EGH 3 – etalon za karakterizaciju indikacija, za neprovareni korijen 2 ÷ 3 mm (sl. 8)
Navedeni etaloni EGH 1, EGH 2 i EGH 3 dizajnirani su od strane tehnologa koji provode
nerazorna ispitivanja. Dizajn sadržava detaljne nacrte sa svim potrebnim dimenzijama,
kao i materijal za koji je nužno da bude istovjetan s materijalom ispitivanog objekta. Dizajn
etalona EGH 1 temelji se na normi EN 1714 koja definira osjetljivost ispitivanja. Svrha je
etalona EGH 2 i EGH 3 da budu podloga za karakterizaciju navedenih indikacija koje je
ovim postupkom moguće otkriti, a koje mogu biti pokazatelji postojećih pogrešaka. Za izradu
etalona napravljen je naputak za tehnološki proces koji omogućuje kvalitetnu izradu etalona.
27
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Slika 5. Zavareni spoj kanala i poklopca
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Slika 6. Etalon EGH 1
Slika 7. Etalon EGH 2
Slika 8. Etalon RGH 3
Mjerno područje je 100 mm. Ono se podešava na K2 etalonu, tako da prvi signal sa r = 25
mm postavimo na 25 hds (horizontalni dijelovi skale) i 80% VE (visina ekrana), a drugi signal
na 100 hds. Zbog razlike u ultrazvučnim brzinama materijala etalona i materijala oplate prvi
signal sa 25 hds treba postaviti na 28 hds. Naime brzina transverzalnih ultrazvučnih valova
u materijalu etalona K2 (čelik) veća je od brzine istih valova u austenitnom materijalu, što
ima za posljedicu razliku u vremenu prolaza vala za upravo 3 hds-a na mjernom području
od 100 mm.
Referentna osjetljivost ispitivanja proizlazi iz norme EN 1714 i EN 1712. Prema metodi 3
određivanja referentne osjetljivosti za kutne sonde ≥ 70° i debljine ispitivanja 8 ÷ 15 mm
koristi se etalon s utorom dubine 1 mm (EGH 1) za izradu krivulje referentne osjetljivosti
ispitivanja (DAC krivulja) (sl. 9).
Slika 9. DAC krivulja referentne osjetljivosti
28
Slika 10. Signali od podložne trake
Uvođenjem ultrazvučne energije (skicirano zelenim strelicama) do greške neprovarenog
korijena s naznačenih pozicija sonde dobivaju se karakteristični signali prikazani na sl. 11.
Slika 11. Pozicije uvođenja ultrazvučne energije (etalon EGH 3)
Slika 12. Maksimalni signal na 21,5 mm
ultrazvučnog puta (7,3 mm dubine) s pozicije
skeniranja p/2. Ehodinamika signala je 16 ÷ 25
mm ultrazvučnog puta (5,5 ÷ 8,5 mm dubine).
Slika 13. Maksimalni signal na 64,5 mm
ultrazvučnog puta (22,1 mm dubine) s pozicije
skeniranja 3/2 p. Ehodinamika signala je 60 ÷
68,4 mm ultrazvučnog puta (20,6 ÷ 23,4 mm
dubine).
Uvođenjem ultrazvučne energije (skicirano zelenim strelicama) do greške naljepljenja s
naznačenih pozicija sonde dobivaju se karakteristični signali kao na sl. 14.
29
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Na sl. 10 prikazani su signali dobiveni skeniranjem sa strana kanala, međutim treba voditi
računa o tome da signali od podložne trake nisu uvijek prisutni, a ovise o položaju trake u
odnosu na oplatu kao i neprovarenosti zavarenog spoja trake i oplate. Ehodinamika signala
je 41 ÷ 47 mm ultrazvučnog puta (12 ÷ 16 mm dubine).
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
Slika 14. Pozicije uvođenja utrazvučne energije (etalon EGH 1)
Slika 15. Maksimalni signal na 36,3 mm ultrazvučnog
puta (12,4 mm dubine) s pozicije skeniranja između
p/2 i p. Ehodinamika signala je 32,1 ÷ 39,4 mm
ultrazvučnog puta (11 ÷ 13,5 mm dubine).
Slika 16. Maksimalni signal na 88,4 mm ultrazvučnog
puta (28,5 mm dubine) s pozicije skeniranja između
3/2p i 2p. Ehodinamika signala je 77,4 ÷ 91,4 mm
ultrazvučnog puta (26,5 ÷ 31,3 mm dubine).
4. ZAKLJUČAK
Dobivene ultrazvučne signale u tijeku ispitivanja, potrebno je procijeniti s obzirom na njihovu
visinu i karakter:
- treba razmotriti sve signale čija je visina veća od 33% visine DAC krivulje (-10 dB od
referentne razine)
- zabilježiti sve signale bez obzira na njihovu dužinu ako dosežu visinu -2 dB referentne
razine.
Prema ISO 5817 za klasu zavara C, sve indikacije dužine (l) u odnosu na debljinu (t) nisu
prihvatljive ako su zadovoljena dva uvjeta:
- l ≤ t i visina signala iznad je referentne razine
- l > t i visina signala je -6 dB od referentne razine (tj. 50% DAC krivulje)
Ako su ultrazvučne indikacije okarakterizirane kao planarne (pukotine, greške naljepljenja i
neprovarenog korijena), tada je to primarni kriterij za prihvaćanje ili odbacivanje. Indikacije
čija visina signala prelazi 30% DAC krivulje (-10 dB od referentne razine), a okarakterizirane
su kao planarne, nisu prihvatljive.
Opisana ultrazvučna tehnika ispitivanja u ovom postupku zavarenih „V”-spojeva oplate
ispušnog kućišta plinske turbine GT 24 /GT 26 pokazala se pouzdanom u otkrivanju
pogrešaka zavara i to neprovarenog korijena, nepotpunog protaljivanja osnovnog s dodatnim
materijalom, tj. greške naljepljivanja zarobljenog oksida na skošenjima pripreme i pukotina.
Ispitivanje se provodi prema EN 1714 - metoda 3, ali je potrebno koristiti:
30
Ovako primijenjena tehnika ispitivanja pokazuje dobre rezultate i uz činjenicu da je ispitivani
materijal austenitni čelik (X 6 CrNiTi 18/10).
5. LITERATURA
[1] EN 27963 - Welds in steel - calibration block No.2 for ultrasonic examination of welds
[2] EN 1712 - Non-destructive testing of welds – Ultrasonic testing of welded joints
[3] EN 1713 - Non-destructive examination of welds - Ultrasonic examination of weld joins – Acceptance levels
[4] EN 1714 - Non-destructive examination of welds - Ultrasonic examination of weld joins
[5] ISO 5817 - Welding - Fusion-welded joints in steel, nickl, titanium and their alloys (beam welding excluded)
– Quality levels for imperfections
[6] V. Krstelj „Ultrazvučna kontrola - odabrana poglavlja“, Sveučilište u Zagrebu, Fakultet strojarstva i
brodogradnje, 2003.
31
ULTRAZVUČNO ISPITIVANJE OPLATE ISPUŠNIH
KUĆIŠTA PLINSKIH TURBINA GT 24/GT26
1) ultrazvučni aparat s mogućnosti podešavanja frekvencija 1 ÷ 10 MHz, vertikalnom
linearnošću u granicama +/- 2 dB i horizontalnom linearnošću < 2%
2) ispitnu sondu MWB 70 (4 MHz)
3) za baždarenje mjernog područja etalon K2 (prema normi EN 27963)
4) za karakterizaciju indikacija izrađene etalone EGH 1 (prema zahtjevu iz EN 1714), EGH
2 i EGH3 pri čemu je važno da su etaloni napravljeni od istovjetnog materijala, odnosno da
imaju ista svojstva s obzirom na prijenos ultrazvučne energije. Također treba voditi računa
da dimenzije etalona odgovaraju stvarnom ispitivanom objektu.
MISFUELING DETECTION WITH TWO OFFSETED
CAPACITIVE FUEL SENDERS
Dubravko, MILJKOVIĆ, HEP - Croatian Electricity Company, Zagreb, CROATIA,
Contacts – mob: +385 98 9825602, e-mail: [email protected]
ABSTRACT - Misfueling of a general aviation aircraft with a Jet Fuel instead of an Avgas
can have dire consequences. In this paper simple non-destructive testing method is
proposed using two capacitive fuel senders that are vertically displaced in a fuel tank by
a small distance to detect such situation. Method is based on different readings for the
same fuel level in a tank (as fuel senders are displaced). Each fuel has different dielectric
constant. In case of correct fuelling difference between these readings will always fall
within narrow fixed interval.
MATEST 2011
1. INTRODUCTION
Misfueling is the introduction of an improper fuel into an aircraft’s tanks. The consequences
of misfueling can range from the benign (fuel system drainage) to the expensive (engine
replacement) to the disastrous (engine failure shortly after takeoff), [1]. Misfueling is always
potentially very serious event. The greatest danger for most general aviation pilots occurs
when a gasoline (Avgas) engine is serviced with jet fuel (often know to general population
as kerosene, but with commercial names Jet fuel A, A1, B, Avtur etc.). Most commercial
turbine engines can be run on avgas within the limits listed in the Pilot Operating Handbook.
However the gasoline engines cannot be run on jet fuel. If not supplied with fuel of a certain
octane rating, a gasoline engine will stop working, be damaged or destroyed by detonation.
Many practical aspects of misfueling prevention by conventional procedures for aviators are
described in great detail in [1]. In this paper simple method is proposed using two capacitive
fuel senders that are vertically displaced in a fuel tank by a small distance (i.e submerged to
different depth in fuel) to detect such situation. Method is based on different readings for the
same fuel level in a tank. Each fuel has different dielectric constant. In case of correct fuelling
difference between these readings will always fall within narrow fixed interval. However in
case of a misfueling, due to different dielectric constant of a mixture or layering of different
fuels (before they mix) with different dielectric constants and capacitive fuel senders vertically
submerged to different depths in different fuels, difference between readings will fall outside
of the acceptable interval. In the later case warning will be issued and additional probe of fuel
should be preformed. A lightly contaminated fuel (FAA test find it up to 6% volume mixture of
Jet Fuel in Avgas acceptable for lean rating but still unacceptable for rich rating) would pass
through with little or no detriment to engine. Requirement for accuracy of capacitive senders
is proposed based on tolerable mixture.
32
1.1
DIELECTRIC CONSTANTS OF AVIATION FUELS
Dielectric constants of aviation fuels are presented in Table 1 and Figure 1, [2].
Table 1 Dielectric constants of aviation fuels
Fuel
Avgas
Jet A, A1
Jet B
Fuel
20
Avgas1,96
2,13
Jet A, A1
Jet B2,06
Temperature (°C)
Temperature (°C)
2040
4060
1,96- 2,10
2,07
2,13
2,10
2,03
2,00
2,06
2,03
60
2,07
2,00
MATEST 2011
Jet fuel A and A1 have about 10% higher dielectric constant than Avgas.
Figure 1 Dielectric constant vs. temperature for typical aircraft fuel at 400 Hz
(adopted from [2])
1.2
DIELECTRIC CONSTANT OF THE FUEL MIXTURE
Dielectric constant of the fuel mixture can be determined by following equation:
where
k = pk 1 + (1 − p )k2
(1)
k is the dielectric constant of mixture
k1 is the dielectric constant of fuel 1
k2 is the dielectric constant of fuel 2
p is the volume part of fuel 1 in mixture, 0 < p < 1
33
1.3
PRINCIPLE OF CAPACITIVE FUEL SENDER
Capacitive fuel sender is based on tubular capacitor probe where fuel becomes dielectric, as
shown in Figure 2, from [3]. Principal of operation is based on the difference in the dielectric
properties of air and fuel, and described in great detail in [2]. At different fuel levels, different
values of capacitance are measured and therefore the level of fuel can be determined. AC
current is used in a process. As dielectric constants vary a little with temperature, better
capacitive fuel includes thermal compensation. Device itself is without any movable or
flexible parts. Advantages of capacitive fuel senders are high precision, high reliability and
good cost performance.
MATEST 2011
Figure 2 Fuel level sensor schematic
Theoretical capacitance of cylinder probe in vacuum is
C=
where is
q 2πε o L
=
V ln (b a )
(2)
L – length of probe
a – Outer radius of probe inner tube
b – Inner radius of probe outer tube
In a real life capacitance of a probe Cp consists of two parts: the effective capacitance CPeff
developed across the dielectric gap between the electrodes and the stray capacitance
CPstr developed between the tube and other items like adjacent structure. The overall dry
capacitance is expressed as
CPdry = CPeff + CPstr (3)
When the probe is fully submerged in a fuel of dielectric of k its capacity is
CPfull = kC
+ CPstr (4)
CPfull = (k − 1)CPeff + CPdry (5)
Peff
When the probe is partially submerged in a fuel of dielectric of k, where n is normalized value
between 0 and 1, its capacity is expressed by
CnPfull = n(k − 1)CPeff + CPdry 34
(6)
The change in capacitance CpnΔ from air to partial submersion is
CPn ∆ = CnPfull − CPdry (7)
CPn ∆ = n(k − 1)CPeff (8)
Electronic circuits supplied with the capacitive probe provide that a change in probe capacity
is transformed to the output voltage proportional to the fuel level in a tank (e.g. 0 – 5 V
range), where is r proportionality constant:
U out = rC
P
n ∆
+ U base (9)
After correct calibration Ubase is set to 0 and output voltage is expressed by
U out = rC
P
n ∆
(10)
Method uses two displaced capacitive fuel senders with temperature compensation. They
are submerged into fuel to different depth, as shown in Figure 3. First probe is submerged
almost to the bottom of the fuel tank, while second probe is offseted (displaced) by 25% of
the full tank fuel level (without some small amount of fuel under the first probe and bottom
of the fuel tank). For the particular fuel level in a fuel tank readings from both senders will
differ for a constant value (actually, readings will fall within narrow interval). If the fuel level in
tank is greater than 25% of full capacity both probes will be submerged in fuel. Fuel senders
have temperature compensation (due to slight change of dielectric constant of Avgas with
temperature). Offset value of 25% was chosen arbitrary as a compromise between precision
and necessary fuel level.
Figure 3 Fuel tank with two capacitive fuel senders submerged to different depths
(the diameter of fuel senders is enlarged in comparison with the tank for clarity purpose)
If we assume that CPeff is same in both fuel probes the capacity change from empty tank in
the first probe is
CPn ∆ ,1 = n(k − 1)CPeff (11)
35
MATEST 2011
2. METHOD
The capacity change from empty tank in the second probe is
CPn ∆ , 2 = (n − 0.25
)(k − 1)CPeff (12)
The capacity change between two probes is then
CP∆ = CPn ∆ ,1 − CPn ∆ , 2 (13)
CP∆ = 0.25 (k − 1)CPeff (14)
MATEST 2011
The output from fuel senders is voltage change proportional to change in capacitance:
U out ,1 = rC
P
n ∆ ,1
U out , 2 = rC
P
n ∆ ,2
(15)
(16)
∆U = U out ,1 − U out , 2 (17)
∆U = r (CPn ∆ ,1 − CPn ∆ , 2 ) (18)
∆U = 0.25 r (k − 1)CPeff (19)
where is
Uout,1 - the output voltage from the first fuel sender
Uout,2 - the output voltage from the second fuel sender
With the correct fueling difference ΔU will remain constant regardless of the fuel level within
a tank (once the tank is full over 25% and both probes are submerged). However in case
of misfueling, dielectric constant k of the mixture will change and so will difference ΔU.
Differences in values of dielectric constants of different fuels are not very large, actually
values are quite similar. For that reason it is necessary to detect subtle changes in ΔU.
(
)
∆U Avgas = 0.25 r k Avgas − 1 C Peff (20)
∆U Mix = 0.25 r (k Mix − 1)CPeff (21)
where is
ΔUAvgas - the difference between outputs of two fuel senders submerged in Avgas
ΔUMix - the difference between outputs of two fuel senders submerged in fuel
mixture (Avgas and Jet Fuel).
3. RESULTS OF CALCULATIONS FOR FUEL MIXTURES
In real application the precision class of fuel senders should be considered. If α is the relative
errors then the following relation is valid for Avgas
(1 − α )U out ,1 − (1 + α )U out , 2 < ∆U Avgas < (1 + α )U out ,1 − (1 − α )U out , 2 36
(22)
and the following for the case of mixed fuels:
(1 − α )U out ,1 − (1 + α )U out , 2 < ∆U Mix < (1 + α )U out ,1 − (1 − α )U out , 2 (23)
When considering the ratio ΔUMix / ΔUAvgas in worst case scenario both relative errors in
ΔUAvgas will be the opposite direction of both relative errors in ΔUMix.
0,25 r (k Mix − 1)CPeff
(
)
0,25 r k Avgas − 1 CPeff
(1 − 4α ) <
0,25 r (k Mix − 1)CPeff
∆U Mix
(1 + 4α ) <
∆U Avgas 0,25 r k Avgas − 1 CPeff
(
)
(24)
Table 2 Dielectric constants for various Avgas and Jet Fuel A1 fuel mixtures, ratio kMix-1 / kAvgas-1 and
minimal required accuracy class for fuel senders to detect ratio for a particular fuel mixture
Fuel volume mixture
Required accuracy class
kMix-1
Dielectric constant
Avgas
-------for fuel senders (%
Jet Fuel A1 (%)
(20° C)
(%)
kAvgas-1
precision accuracy)
100
0
1,9600
1
95
5
1,9685
1,0089
0,2
94
6 (FAA tolerance)*
1,9702
1,0106
0,2
90
10
1,9770
1,0177
0,2
80
20
1,9940
1,0354
0,5
70
30
2,0110
1,0531
1
60
40
2,0280
1,0708
1
50
50
2,0450
1,0885
2
40
60
2,0620
1,1063
2
30
70
2,0790
1,1240
2
20
80
2,0960
1,1417
2
10
90
2,1130
1,1594
2
0
100
2,1300
1,1791
2
max volume part of Jet Fuel in Avgas as suggested by tests performed by FAA (for real application
please do check this data)
*
4. DISCUSSION
As already mentioned there is just slight difference between the dielectric constant of correct
fuel (Avgas) and the dielectric constant of improper fuel (mixture of Avgas and Jet fuel).
Therefore method must be very sensitive to these subtle changes in dielectric constant.
That requires quite precise capacitive fuel senders (accuracy class 0,2). However, such
fuel senders are today commercially available under moderate price (few hundred USD),
particularly when considering application. Capacitive probe diameter should be large enough
(25 mm) to allow fuel mixing not just within a tank but also within the fuel probes. Fuel probes
span across most depth of the fuel tank and integrate dielectric constant of fuel at various
37
MATEST 2011
k Mix − 1
(1 − 4α ) < ∆U Mix < kMix − 1 (1 + 4α ) (25)
k Avgas − 1
∆U Avgas k Avgas − 1
Here is assumed that α << 1 and Uout,1 is close to Uout,2 (actually Uout,2 is, when tank is full, 33%
less than Uout,1, but here is still considered close), and worst case relative error is for more
precise consideration about ±3.5 α.
Dielectric constants for various Avgas and Jet Fuel A1 fuel mixtures, ratio kMix-1 / kAvgas-1 (and
hence ΔUMix / ΔUAvgas ) with minimal required accuracy class for fuel senders to detect the
ratio for particular fuel mixture (using ±4 α error) are presented in Table 2.
levels within a tank, not just at one point (what could be achieved with e.g. small capacitive
probe placed at the bottom of a tank). Due to inherent sensitivity to change of dielectric
constant method may encounter problems if fueled with Avgas that contain some additives
(i.e. slightly different variants of Avgas may available at different refueling locations). These
changes in dielectric constant must be somehow known in advance. Method will easily detect
fuel contaminated with water (water has high dielectric constant of around 80).
MATEST 2011
5. CONCLUSIONS
Proposed idea could be a valuable approach for detecting misfueling of general aviation
aircraft. It could be simple integrated into existing airplanes, replacing the old (unreliable)
type of floating fuel sender. By employing two commercially available high precision offseted
(displaced) fuel senders with temperature compensation it detects misfueling by detecting
a change in dielectric constant of the fuel. Fuel senders are submerged into fuel to different
depths and hence give different output voltages. The difference between these voltages is
constant regardless of the fuel level. In case of msifuelling this difference shifts from its usual
narrow range of values. Use of two fuel senders also gives redundant setup for measuring
fuel level within a tank. This paper is just theoretical basis, for the real application extensive
experiments would be needed, including process of initial mixing of fuels, influences of
various fuel levels in the tank (e.g. full tank, three quarters and half tank) after misfueling,
influences of fuel additives, effect of filling the fuel probes from the bottom and diffusion of
fuel mixture within the probe (need for the sufficient probe diameter).
6. REFERENCES
1. AOPA Safety Brief No 4: Misfueling, http://www.aopa.org/asf/publications/SB04.pdf (PDF,
accessed October 9, 2011)
2. Roy Langton, Chuck Clark, Martin Hewitt, Aircraft Fuel Systems, Wiley 2009, UK
3. Shenzhen, High accuracy capacitive fuel sensor, http://joint-tracking.com/Upload/
PicFiles/2010.7.20_9.28.8_9083.pdf (PDF, accessed October 9, 2011)
38
U ovom broju predstavljamo
CROATIAINSPECT.
vam
dugogodišnjeg
kolektivnog
člana,
društvo
T k a l č i ć e v a 7 / I V, 1 0 0 0 0 Z a g r e b , w w w. c r o a t i a i n s p e c t . h r
( 01/4874777 2 01/4873728 : [email protected]
Direktor i član Uprave Mario Štambuk, dipl. ing., ujedno je i potpredsjednik HDKBR-a. Osnovna
je djelatnost tvrtke kontrola kvalitete, nadzor u provođenja ispitivanja te osiguravanje kvalitete
opreme koja se koristi u naftnoj industriji, počevši od opreme za istraživanje i proizvodnju do
opreme za transport, preradu i skladištenje nafte i plina.
Uprava Croatiainspecta smještena je u samom centru Zagreba u Tkalčićevoj 7, pa je g.
Štambuk i najbliži susjed HDKBR, stoga je ovaj intervju iznimno brzo i lako dogovoren.
Budući da je naša djelatnost kontrola kvalitete, razvija se suradnja s društvom u više područja.
U samim počecima, a ove godine smo uspješno proslavili 40. godišnjicu naše tvrtke, osim
obrazovanja naših inspektora bila je i značajna suradnja na zajedničkim projektima uvođenja
nerazornih metoda u kontrolu kvalitete i razrada postupaka za potrebe ispitivanja bušotinske
opreme. Također treba naglasiti da su naši inspektori u okviru društva pratili i surađivali u
razvoju kontrole bez razaranja (KBR-a) i na taj način lakše izvršavali inspekcijske nadzore.
Iskustva koja smo stjecali u okviru našeg posla po cijelom svijetu, gdje smo imali prilike
vidjeti i upoznazi se s najsuvremenijom opremom za kontrolu cijevi i zavarenih spojeva
elektromagnetskim i ultrazvučnim tehnikama, prenosili smo i dijelili s kolegama u Hrvatskom
društvu za kontrolu bez razaranja.
Ultrazvučna kontrola zavarenog spoja cijevi
sa spiralnim zavarom
Magnetska kontrola UV-česticama u liniji
proizvodnje
Naravno da je neizostavno područje u kojem također surađujemo sustav osiguranja kvalitete
kao i praćenje relevantnih normi iz tog područja. U posljednje vrijeme, otkako sam član
Upravnog odbora HDKBR, rado se odazivam na europske i svjetske konferencije, tako da
sam imao čast i zadovoljstvo biti jedan od predstavnika HDKBR-a na konferencijama u
Valenciji i Durbanu.
39
PREDSTAVLJAMO VAM
Na kojem se području zasniva suradnja Croatiainspecta s HDKBR-om?
PREDSTAVLJAMO VAM
Durban, Svjetska konferencija KBR 2012.
Ovdje moram naglasiti da sam posebno bio očaran i ponosan dobrodošlicom domaćina,
predstavnika EFNDT-a i ICNDT-a, nama u HDKBR-u, duboko uvjeren da je to zahvaljujući
Vama, našoj dugogodišnjoj predsjednici, Vašem predanom radu te suradnji s međunarodnim
organizacijama.
Kako ste zadovoljni s obrazovanjem Vaših inspektora u području KBR-a u našem
društvu?
Teško je objektivno odgovoriti na ovo pitanje s obzirom da sam kao član Upravnog odbora
i sam odgovoran za rad i djelatnost društva. Moram međutim istaknuti da je organizacija
obrazovanja i sustav certifikacije znatno poboljšan, kao i kvaliteta i opseg predavanja i
materijala. Kao korisnik usluga Društva, iako je poboljšana frekvencija organizacije tečajeva,
još uvijek nije u potpunosti prilagođena zahtjevima nas iz privrede koji moramo često vrlo
brzo i tržišno reagirati. Znajući i da su mogućnosti organiziranja obrazovanja djelomično
ograničene, naime HDKBR ima određeni program tečajeva, a s druge strane upoznati
smo s potrebama obrazovanja i izvan Hrvatske, možda bi se problem mogao riješiti onlineobrazovanjem. Razmatram tu ideju i vjerujem da ću ako nađem dovoljno argumenata
predložiti tu ideju Centru za obrazovanje.
40
Molim Vas da nam se sada osobno predstavite zbog naših čitatelja koji nisu imali
prilike upoznati vas do sada.
Stalnim usavršavanjem na različitim tečajevima, bavio sam se i kontrolom bez i sa
razaranjem, auditima proizvođača, kontrolama označavanja, pakiranja, utovara i istovara
robe te ostalim aktivnostima inspektora strojarske opreme. Ovlašten sam inspektor Aramca,
naftne kompanije Saudijske Arabije, za što sam osim referenci i poznavanja engleskog jezika
trebao položiti poseban ispit o znanjima iz područja materijala, zavarivanja, ispitivanja bez
razaranja i poznavanja relevantnih normi. Brzo sam napredovao i postao voditelj poslova,
pomoćnik direktora pa do sadašnje funkcije člana Uprave.
Od 2001. do 2011. uz postojeći posao obavljao sam i poslove Predsjednika uprave
Adriainspekta i direktora Tehničke poslovnice.
za kontrolu kvalitete i kvantitete robe i trgovačku djelatnost Cargo Superintendence and
Trade Company, Ciottina 17b, 51000 Rijeka, Croatia, http://www.adriainspekt.hr
Glavna djelatnost Tehničke poslovnice upravo je pružanje usluge ispitivanja nerazornim
metodama, najčešće u riječkom okrugu u RN Rijeka, TE Rijeka, brodogradilištima 3. maj,
Viktor Lenac, Kraljevica, Janaf i ostalim pogonima.
Adriainspekt posjeduje laboratorij s opremom za nerazorna ispitivanja, certiificirano osoblje,
a od prošle godine ima i uređaj za digitalnu radiografiju. Također ima poslovnicu za kontrolu
nafte i derivata te poslovnicu za rude i poljoprivredu. U razdoblju mog rada u Adriainspektu
suradnja s HDKBR-om bila je dvostruka jer sam uključio obje tvrtke, odnosno kolege u
kontroli bez razaranja iz obiju tvrtki. Mislim da je važno napomenuti da sam dugogodišnji
član TO 135 za kontrolu bez razaranja pri HZN.
Kolega Štambuk, imate li Vi možda neko pitanje koje želite uputiti kolegama u kontroli
bez razaranja?
Nemam pitanje, ali bih želio iskoristiti prigodu i pozvati sve naše kolegice i kolege da nam
se pridruže i budu aktivni sudionici u tjednu „NDT week in Zagreb”, europske konferencije
o obrazovanju, certifikaciji i normizaciji, CERTIFICATION 2013 kao i MATESTA 2013,
međunarodne konferencije HDKBR-a, koji ove godine obilježava 50. obljetnicu.
Ovu prigodu da u Zagrebu imamo tako važan skup na kojem će se okupiti stručnjaci u
kontroli bez razaranja iz cijeloga svijeta ne smije se propustiti.
Kolega Štambuk, hvala na Vašoj podršci HDKBR-u.
41
PREDSTAVLJAMO VAM
Na FSB-u diplomirao sam 1984. godine i već prije obrane diplomskog rada zaposlio se i
počeo raditi kao inspektor, premda mi je moj mentor, cijenjeni prof. Šurina, ponudio mjesto
na katedri Automatika u strojarstvu. Stječući praksu kao mladi inženjer/inspektor, najprije
u inspekciji proizvodnje cijevi u Željezari Sisak, naučivši osnove tehnologija proizvodnje,
kontrole i zahtjeva API-normi, vrlo brzo počeo sam raditi i slične inspekcije po cijelome svijetu.
Tako sam prošao sve renomirane proizvođače cijevi, opreme za istraživanje i proizvodnju,
te transport i skladištenje od Amerike do Japana. Mnoge stvari vidio sam u funkciji daleko
prije nego su se pojavile kod nas. Tako naprimjer sustav osiguranja kvalitete, današnji HRN
EN ISO 9001, u Sumitomu (Japan) bio je u primjeni još 1985., dok je kod nas prvi skup na
tu temu koji smo mi organizirali pod pokroviteljstvom HGK-a bio održan nekoliko godina
kasnije, a još je prošlo par godina do početka certifikacije sustava.
NDT WEEK in ZAGREB
NDT WEEK in ZAGREB 7-12 October 2013
2013. godine HDKBR obilježava 50 godina kontinuiranog djelovanja u promociji i potpori
razvoja primjene nerazornih metoda u ispitivanju, kontroli kvalitete i tehničkoj dijagnostici.
Godine 1963. bila je to samo skupina entuzijasta svjesna važnosti uvođenja kontrole kvalitete i metoda koje to mogu osigurati. Danas HDKBR s ponosom najavljuje TJEDAN KBR-a u ZAGREBU
u kojem će s nama biti mnogi cijenjeni stručnjaci iz Europe i svijeta.
Croatian Society of Non-Destructive Testing, (HDKBR - local abrivation) is celebrating 50 years of
permanent activity in promoting and supporting R&D and implementation of NDT and Technical
Diagnostic.
In the year 1963, it was just a group of enthusiasts starting to implement NDT in Quality system.
We proudly invite you to NDT WEEK in ZAGREB. Many of renown scientists and experts from Europe
and wider will be with us working on NDT, nowdays an unavoidable proffession.
Monday 07.10.2013.
P.M.
ECEC meeting
Tuesday 08.10.2013.
ECEC & ICEC joint meeting*
EFNDT & ICNDT Certification executive Committee
Wednesday 09.10.2013. MATEST 2013
09:00-10:00
Opening MATEST 2013
10:30-18:00
ISO / TC 135 / SC 7 / WG9 meeting*
10:30-18:00
EFNDT BoD meeting*
10:00-13:00
16:00-18:00
EFNDT WG 5 meeting
19:30-22:00
Reception: HDKBR 50th annievrsary
MATEST 2013
Conference program
continuing
Thursday 10.10.2013. CERTIFICATION 2013
09:00-11:00
Opening
11:30-17:00
Session 1: ICNDT Regional groups
11:30-17:00
17:00-18:30
Session 2A: National Societies; Education
Qualification & Certification
Session 3: EFNDT and ICNDT MRA; Signature
ceremony
Friday 11.10.2013. CERTIFICATION 2013
13:00-15:30
15:30-17:00
Session 2B: National Societies; Education,
Qualification & Certification
Session 4: Quality system, Methods,
Laboratory; Different sectors approach
Session 5: Competence / Training syllabuses
Session 6: Safety & Security
17:00-17:30
Conclusions & Closing
19:00-22:00
Conference dinner
09:00-10:30
11:00-13:00
Saturday 12.10.2013.
09:00-12:00
EU Leonardo project meeting*
*Sastanci samo uz poziv/ *meetings by invitation only
42
16:00-18:00 EU Leonardo
project meeting*
MATEST
09.10.2013.
08:00 - 09:00
Registration
09:00 - 10:30
OPENING
09:00 - 09:20
Miro Džapo: Opening
09:20 - 09:40
Nenad Gucunski: Robotic Platform RABIT for Conditional Assessment
of Contrete Bridge Decks Using Multiple NDE Technologies
10:00 - 10:30
10:30 - 14:00
10:30 - 10:45
10:45 - 11:00
11:00 - 11:15
Dario Almesberger: NDT Methods in Exploration Works on the
Structure of Arena in Pula
Coffee break
SESSION 1
Lovre Krstulović, Endri Garafulić: Željko Domazet: Termography
Image Processing Techniques
Zoran Bičanić, Saša Bratko, Danko Dobranović: Experience in
Applying Infrared Thermography in Gas Leak Detection
Berislav Nadinić, Fran Jarnjak: Overview of Advanced UT Techniques
11:15 - 11:30
Sanja Rakljašić: Experience in Applying Phased Array in Inspection of
Welds on Small Dimensions Tubes
11:30 - 11:45
Zvonimir Ivković:Tracebility of NDT key documentation required by
PED 97/23 EC
11:45 - 12:00
Bruno Breka: Possibility of Achieving Requested Image Quality in Case
When Standard Requirements can’t be Achieved
12:00 - 12:15
Tomislav Andrić: Future Development of NDT Activities in Shipyard
Brodotrogir
12:15 - 12:30
Vladimir Zado: Ispitivanje zavarenih spojeva priključaka na poklopac
reaktorske posude ultrazvučnom metodom/ Testing of reactor vessel
head nozzle J groove welds by ultrasound
12:30 - 12:45
Dragica Krstić, Martina Pavec, Zdravko Schauperl: Characterization
of Foxing Stains in Eighteenth Century Books
12:45 - 14:00
Lunch
14:00 - 15:15
SESSION 2
14:00 - 14:15
Ivana Banjad Pečur: Istraživanja u građevinarstvu pomoću ispitivanja
bez razaranja/ Research in civil engineering using non-destructive testing
14:15 - 14:30
Roberto Rinaldi: The experience of ITC about certification: CM or NDT?
14:30 - 14:45
Noam Amir: Non-invasive inspection of Heat Exchanger Tubes
14:45 - 15:00
Mark Nel: The basic of TOFD
15:00 - 15:15
Mark Nel: The basic of Phased Array
15:15 - 15:30
Predrag Dukić: Risk base assesment
16:00 - 16:15
Dubravko Miljković: Statistical Properties of Aircraft Piston Engine
Monitor –CM Data
16:15 - 16:30
Mladen Vrebčević: Akreditiranje tijela za certificiranje osoblja
16:30 - 18:00
POSTER SESSION
43
MATEST 2013
09:40 - 10:00
The Preliminary Program: CERTIFICATION 2013
09:30 – 11:30
09:30 – 09:45
09:45 – 10:00
10:00 – 10:15
10:15 – 10:30
10:30 – 11:00
11:00 – 11:30
11:30 – 14:30
11:30 – 11:45
11:45 – 12:00
12:00 – 12:15
12:15 – 12:30
12:30 – 12:45
12:45 – 13:00
13:00 – 14:30
14:30 – 17:00
14:30 – 14:45
14:45 – 15:00
15:00 – 15:15
15:15 – 15:30
15:30 – 15:45
15:45 – 16:00
16:00 – 16:15
16:15 – 16:30
16:30 – 16:45
16:45 – 17:00
17:00 – 18:00
44
CERTIFICATION Day 1, 10.10.2013.
OPENING
Vjera Krstelj: Opening Lecture
Patrick Fallouey: EN ISO 9712 – Succesfull merging; What’s after?
Hajime Hatano: The activities of ISO/TC 135
Giusseppee Nardoni: Academia NDT international in Competence support
Questions and Discussion
Coffee break
SESSION 1: ICNDT REGINAL GROUP
Matthias Purschke: EFNDT Certification Agreement – Why to an European
Certificate?
John Zirnhelt, Sharon Bond, PK Yuen: Qualification and Certification in
Canada
Norikazu Ooka: Introduction of NDT Training course for Asia Pacific
Region and Activities of Task Group meeting being conducted by JSNDI
extra budget
Ir. Sajeesh K Babu: NDT Personnel Certification updates in Asia Pacific
Region
Patrick Brisset: IAEA activities related to NDT personnel training and
certification
Questions & Discussion
Lunch
SEASSION 2A: NATIONAL SOCIETIES: Education, Qualification,
Certification
Biserka B. Brezak: Accreditation; National, Regional and Worldwide
approach
Miro Džapo: Qualification and Certification in Croatia
Gerhard Aufricht, Roman Wottle: Experience with the professional,
modular NDT-Certification in Austria
Emilio Romero, Radolfo Rodriguez: The training and certification of NDT
personnel in Spain, past, present and future
Bento Alves, Claudia Almeida, M.Jose Teixeira: RELACRE, the
authorized Qualification Body for NDT in Portugal – Current Situation and
Main Challenges
Pavel Mazal, Bernard Kopec: Certification of NDT personnel in the
Czech Republic – situation and perspectives
Matt Gallagher, Philip Picton, David Gilbert: An integrated education
programme for NDT proffesionals
Vasil Nichev, Mitko Mihovski, Aleksander Skordev: Education and
Certification in Bulgaria. Specific approach
Questions & Discussion
Coffee Break
SEASSION 3: EFNDT and ICDNT MRA
Mike Farley / ICNDT – Patric Fallouey / CEN – Hajime Hatano /ISO
EFNDT and ICDNT MRA
- Signature ceremony -
09:15 – 09:30
09:30 – 09:45
09:45 – 10:00
10:00 – 10:15
10:15 – 10:30
10:30 – 10:45
10:45 – 11:00
11:00 – 12:15
11:00 – 11:15
11:15 – 11:30
11:30 – 11:45
11:45 – 12:00
12:00 – 12:15
12:15 – 12:30
12:30 – 13:45
12:30 – 12:45
12:45 – 13:00
13:00 – 13:15
13:15 – 13:30
13:30 – 13:45
13:45 – 15:00
15:00 – 17:00
15:00 – 15:15
15:15 – 15:30
15:30 – 15:45
15:45 – 16:00
16:00 – 17:00
45
The Preliminary Program: CERTIFICATION 2013
09:00 – 11:00
09:00 – 09:15
CERTIFICATION Day 2, 11.10.2013.
SESSION 2B: NATIONAL SOCIETIES: Education, Qualification, Certification
Milan Škrlet: Standardisation in Quality system in Croatia
Goran Sofronić, Dragana Kuzmanović, Davor Gruber:
Accreditation, Qualification and Certification of NDT personnel in Serbia
Goran Sofronić, Dragana Kuzmanović, Davor Gruber: Accreditation,
Qualification and Certification of NDT personnel in Serbia
Ekaterina Cheprasova: Russian Society for NDT’s Automated System of
NDT Specialists Training
Şinasi Ekinci: NDT Training and Certification in Turkey
Joseph Pessach: Qualification and Certification system in Israel
João Rufino: Qualification and Certification in ABENDI; Brazilian Association of NDT and Inspection
Coffee break
SESSION 4: Quality system, Methods, Labaratory; Different sectors
approach
Theobald O.J. Fuchs, Frank Sukowski, Christian Schorr, Tobias
Schön, Stefan Schröpfer, Ulf Hassler, Thomas Hofmann, Nils Reims:
High-Energy 3-D X-ray Tomography for Container Inspection
Ferenc Fücsök, Balázs Hámornik, Ferenc Marcsó: Experiences of the
proficiency tests in the Hungarian Association for NDT
Sergej Kolokolnikov, Antony Dubov: Certification scheme based on ISO
9712:2012 of NDT personnel for MMMM
Mykhail Kazakevych, Migoun Nikolay: Certification of product families
for penetrant testing
Elena Nicheva: Education and qualification requirements for NDT personnel at NPP Kozloduy
Coffee break
SESSION 5: Competence / Training syllabuses
Ralf Holstein, Rainer Link: ISO 9712 Level 3 Certification:
A Skeptical Approach
Radolfo Rodriguez, Emilio Romero: Proqualint, LEONARDO DA VINCI
programme. Development of NDT study materils in diferent languages.
Ir. Sajeesh K Babu: Comparison of training syllabuses in NDT
Prsonnel Certification
István Skopál: Competence control without “significant interruption”
John Thompson: The ICNDT Electronic Examination Question Book
Lunch
SESSION 6: SAFETY and SECURITY
Kurt Osterloh, Gerd-Ruediger Jaenisch, Daniel Kanzler: How to
approach rare events
Isaac Einav: See the invisible–innovative technology as tool for safety and
quality
Davor Zvizdić: University approach to Safety and Security
Ivica Prlić: Security, Education, Qualification, Certification
Closing
TEČAJEVI za KVALIFIKACIJU i CERTIFIKACIJU
Program tečajeva je razrađen u skladu sa
potrebama industrije, te kandidati mogu
odabrati pohađanje tečajeva u skladu sa
svojim obavezama.
Više od ovdje ponuđenih termina može
se dogovoriti, kao i održavanje tečajeva u
tvrtki, kada za to ima potrebe.
HDKBR Centar za obrazovanje
PLANIRAJTE i REZERVIRAJTE
ODMAH
Kandidati za tečajeve 3. stupnja trebaju
osim gore navedenog dostaviti životopis
u kojem treba navesti iskustva u kontroli
kvalitete.
Zamolbe za pohađanje 3. stupanaj dostavljaju se najkasnije do 15. listopada 2013.g.
Kandidati koji su završili studij na
sveučilištu, veleučilištu ili visokoj školi,
tehničkog ili prirodoslovno-matematičkog
usmjerenja stiču pravo na skračeni program
obrazovanja za glavnu metodu - 3 stupanj.
Stupanj
Termini
održavanja
Ultrazvučna kontrola
UT1
14.10.-25.10.2013.
Magnetska kontrola
MT2
25.11.-28.11.2013.
Vizualna kontrola
VT1
02.09.-04.09.2013.
Penetrantska kontrola
PT2
16.09.-19.09.2013.
Ultrazvučna kontrola
UT2
02.12.-13.12.2013.
Radiografska kontrola
RT2
04.11.-15.11.2013.
Opći dio; 3 stupanj
VT3
PT3
MT3
UT3
RT3
11. mjesec
Metoda
Glavna metoda;
3stupanj
9. mj, 10. mj
VAŽNA OBAVIJEST
Polaznici tečajeva od 1.1.2013. godine osiguravaju obrazovanje i mogućnost certifikacije
u skladu sa zahtjevima nove norme
HR EN ISO 9712
ČLANSTVO u HDKBR-u
Obavještavamo sve članove da je u tijeku izdavanje iskaznica za 2013. godinu.
Iskaznice će primiti samo članovi HDKBR-a koji su uplatom članarine za 2013. godinu
ili drugim osnovom stekli članstvo. Obzirom da članovi ostvaruju popust pri certifikaciji, te dobivaju časopis HDKBR Info i druge obavijesti iz Tajništva HDKBR-a, važne
za vaš profesionalni život, molimo vas da provjerite jeste li osigurali članstvo. Svi koji
žele izbjeći gubitak vremena na uplatu od 100 kuna svake godine mogu to učiniti jednokratno za više godina i pri tome ostvariti popust. Uplatom članarine za tri godine u
iznosu od 200 kn ili uplatom članarine za pet godina u iznosu od 400 kn.
Tajništvo HDKBR
46
STJECANJE UVJERENJA
Za stjecanje uvjerenja za određenu metodu,
stupanj obrazovanja i područje ispitivanja treba:
- dostaviti prijavnicu,
-uspješno završiti tečaj obrazovanja u HDKBR
Centru za obrazovanje ili u centru obrazovanja
priznatom od strane HDKBR Centra za
certifikaciju,
-potvrdu o radnom iskustvu i obavljenom očnom
pregledu.
Za stjecanje uvjerenja za ispitivanje tlačne opreme
prema članku 13. Pravilnika PED 97/23/EC
treba: - dodatno obrazovanje u trajanju od jednog
dana u HDKBR Centru za obrazovanje.
Cijena izdavanja certifikata po osobi: 150 eura +
PDV, u što je uključeno i obrazovanje u HDKBR
Centru za obrazovanje. Za svaku dodatnu metodu
cijena uvjerenja je 100 eura + PDV.
Metoda
Stupanj
Vrijeme
Vizualna kontrola
VT1
Vizualna kontrola
VT2
Magnetska kontrola
MT2
28.11.2013.
Penetrantska kontrola
PT2
19.09.2013.
Ultrazvučna kontrola
UT1
25.10.2013.
Ultrazvučna kontrola
UT2
13.12.2013.
Radiografska kontrola
RT2
15.11.2013.
3. stupanj: VT3,MT3,PT3,UT3,RT3,
13.12.2013.
Listopad
2013.
Članovi Društva imaju popust od 10 %.
HDKBR Centar za certifikaciju
CENTAR za CERTIFIKACIJU
Više o certifikaciji na www.hdkbr.hr ili telefonski u tajništvu HDKBR-a.
POSTER SESSION
Branko Jagodić,
Zlatko Horvat
Iskustva u ispitivanju zavarenih spojeva sitnozrnatih čelika/
The experiance of steel weldings
Gordan Polonijo
Ispitivanje zavarenih spojeva na “Cutter Suction Dredgeru”
i “Suction Hopper Dredgeru”/ Experiance in NDT of Cutter
Suction Dredgeru and Suction Hopper Dredgeru
Tamara Topić
Iskustva uvođenja nerazornih ispitivanja u programe obrazovanja; program veleučilišta/ The experiance of launching
NDT in high education; college programs
Ivan Gabrijel,
Bojan Milovanović, Ivana
Pečur Banjad, Nina
Štirmer
Primjena IC termografije za ispitivanje betonskih konstrukcija /Using IR thermography as a NDT method for
testing concrete structures
Ivan Gabrijel
Mikan Slijepac
Mladen Bošnjaković,
Krunoslav Jukić,
Josip Jukić
MATEST 2013/ poster session
09.10.2013;
16:30-18:30
MATEST 2013
Praćenje očvršćivanja betona metodom
akusto-ultrazvuka/Monitoring of concrete hardening
using acousto-ultrasonic method
Iskustva u ispitivanju radnih kola vodenih turbina/ The
experiance of NDT of water turbines
Zahtjevi za ispitivanje zavarenih spojeva tlačne opreme
prema EN i ASME / Examination requirements for welds
in pressure equipment according EN and ASME standards
47
POMOĆ U RADU; Goran Dragičević, Brodosplit
Za časopis uredio: Ivan Smiljanić
RJEŠENJE ZA POZICIONIRANJE ULTRAZVUČNIH APARATA
'Krautkramer USM 25' I/ILI 'Krautkramer USM 35'
POMOĆ U RADU
Slika 1. Ultrazvučni aparat Krautkramer USM 35
Ultrazvučni aparati Krautkramer USM 25 i Krautkramer USM 35 pouzdani su i često korišteni
modeli aparata, koje posjeduje mnogo NDT ispitivača diljem svijeta, kao i na našim prostorima. Međutim kod njih postoji jedna slaba točka, koja postaje očita tijekom dužeg korištenja
ovih aparata. Nakon određenog vremena (kraćeg nego što bi se očekivalo) pozicioneri ručice
gube svoju funkciju, zbog pucanja na mjestima gdje su najtanji. Mjesta nastanka oštećenja
prikazana su crvenim strelicama na slici 1. Jednostavno i zanimljivo rješenje nudi nam
kolega Goran Dragičević, zaposlenik Brodosplita.
Slika 2. Nacrt pozicionera ručice.
Slika 3. Slika sastavnih dijelova pozicionera
ručice
Prvi korak predstavlja izrada kapice od meke plastike za brtvila. Bolje bi rješenje bilo da
se kapice izrade od tvrde gume, ali takva bi opcija bila isplativa samo pri izradi u tvornici
jer je izrada kalupa za lijevanje najskuplja stavka. Drugi korak sastoji se od jednostavnog
navlačenja istih kapica na pozicionere, kako je prikazano na slici 2.
Za jasniju predodžbu na slici 3 dan je i prikaz sastavnih dijelova ovakvog pozicionera.
Nadamo se da će vam ponuđeno rješenje biti od koristi te zahvaljujemo kolegi Dragičeviću
što je svoj patent podijelio s nama. Ovom prigodom potičemo i sve vas na sličnu razmjenu
ideja koje nam olakšavaju svakodnevne radne aktivnosti.
48
49

Brochure UNICO Final_A4_BA_EN_ok.cdr

47th International Symposium FUELS 2014 PROGRAM

zbornik sažetaka

HDKBR Info 2012., broj 9

47th internantional Symposium FUELS 2014 SCHEDULE

HDKBR Info 2011., broj 3

The Drivers` Fuel Challenge 2013.

sustav za planiranje sastanaka za google app engine

IZDANJE / EDITION 10 / 2014