EXPERIMENTAL STUDY ON ROUGHNESS PARAMETERS
VARIATION, DURING RUNNING – IN PERIOD,FOR A CYLINDERPLANE FRICTION COUPLE
Florin Petrescu, Anton Davidescu, Monica Vlase
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
ABSTRACT
This paper proposes a controlled running-in period of a TIMKEN couple surfaces, to provide for a continuous
lubricant film, as shown above, and also the optimum physic-mechanical properties of the superficial layer. In the
conditions of an optimum, controlled running-in period, the micro-geometry obtained at the end of the test can
provide the necessary conditions required by a continuous lubricant film, by providing an EHD regime or a partial
EHD regime.
An interesting behavior has the skewness factor (Rsk); its negative values indicate a micro-geometrical profile
asymmetry under the average line. That leads to an increasing real contact area with a good load force power of
the surface. All the samples indicate a strong decrease of the Rsk parameter in the second test time period. At the
end of the test period the Rsk parameter has negative values (<-2), thus indicating the end of the running-in
period.
The average radius variation at the top of the microroughness was always ascending for all the samples.
The maximum value was obtained for the I1.5.60 sample (r = 24,6μm), at the end of the running-in period, but it
hadn’t the best tribological behavior; the conclusion is that the radius value can’t be a parameter of appreciation
of the friction behavior of the roughness surface.
The average angle at the micro-asperities top (β) has an decreasing value in the first interval of the running-in
period, and then an increasing evolution, finally reaching bigger values than the initial one with maximum 20%;
the biggest value has the I10 sample (β=176°), sample that had the best tribological behavior; the conclusion is
that the (β) parameter can be used as an indicator of he friction behavior.
Keywords: Running-in period, rugosity, load force, friction-wear.
THE EFFECT OF WIBERG ANGLE ABOUT THE CONTACT
PRESSURE DISTRIBUTION IN THE NATURAL AND ARTFICIAL
JOINT
Andrei Tudor1), Carmen Parsu2) and Florina Opris3)
1) “POLITEHNICA” University of Bucharest, Department of Machine Elements and Tribology, ROMANIA
2) “COLENTINA” Hospital of Bucharest, Department of Orthopaedic Surgery, ROMANIA
3) “TITU MAIORESCU” Medicine Faculty of Bucharest, ROMANIA
ABSTRACT
The analogies and differences between the mechanical joints and the biological ones, in the presence of relative
motion, are based on the pressure distribution. The paper analysed a numerical model of the pressure distribution
and friction torq applicable to the spherical joint, specifically to hip. The effect of Wiberg angle about maximum
pressure contact is analysed as a function to clearance joint.
Keywords: Biotribology,. hip joint, contact pressure, clearance joint, friction torque.
INVESTIGATION OF LAYERS FORMED THROUGH
SELECTIVE TRANSFER WITH ATOMIC FORCE MICROSCOPY
Filip Ilie1) , Constantin Tiţa2)
1) Polytechnic University of Bucharest, Department of Machine Elements and Tribology, ROMANIA
2) School Group ”General Magheru» Râmnicu-Vâlcea” , ROMANIA
ABSTRACT
Atomic force microscopy (AFM) has become a versatile tool for investigating local mechanical properties. In
addition, through the AFM tip-couple interaction, it is possible to study the effects of perturbations and
modifications on the surface of samples, such as layers obtained by selective transfer.
The selective layer was obtained by friction between a surface of steel and a surface of copper alloy (bronze) and it
formed of very thin layer, tribologically generated on the surface of steel. The accurate knowledge of their
response to continuous AFM scanning could help to design new materials with desired mechanical properties. A
fundamental study of surface properties of the layers formed by selective transfer on nanoscale level should be
developed to have a satisfactory knowledge of responses of these layers at friction and wear.
In this paper, we present results obtained applying a new method for investigating friction and wear properties on
layers obtained by selective transfer.
Keywords: Atomic Force Mmicroscopy (AFM), selective transfer, friction and wear, ripple, topography.
CONTACT MODEL FOR A ROUGH SURFACE
Sorin Cănănău
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
ABSTRACT
The paper presents a model for the determination of the contact characteristics, pressure distribution and
subsurface stress field at the contact cylinder- plane. The first part of the paper presents the geometrical models
used to determine the stress field. There are three models (at different scale) identified. In the second part there is
performed an analysis with the first model, using a FEM cod and procedure in order to identify the stress filed.
Then, for the second order profile and the second model of contact we present a model for determination of the
asperity pressure distribution assuming the elastic-perfectly plastic deformation. The numerically generated rough
surface is the base for the contact algorithm. The results show differences in comparison wit results predicted by
Hertz theory. The maximum shear stress developed is significantly higher then predicted by theory.
Keywords: contact mechanics, profile, subsurface stress.
ANALYSIS OF GEAR QUALITY CRITERIA AND PERFORMANCE OF
CURVED FACE WIDTH SPUR GEARS
Laurentia Andrei1), Gabriel Andrei1), Douglas Walton2), Karl Dearn2)
1)
2)
The University “Dunarea de Jos” of Galati, ROMANIA
The University of Birmingham, UK
ABSTRACT
For plastic gears, developments in composites and tooth geometry are essential for their selection in power
transmissions. In order to enhance the transmissible power level of the plastic spur gears, an arc-shaped tooth is
designed, with variable height along the gear face width. There are two parameters that influence the tooth
geometry: the radius of the generating point, defining the tooth curvature, and the tool axis inclination, leading to
a tooth height variation. The paper deals with computerized design of the curved face width spur gear, as a
replacement of the traditional numerical procedure, focused on tooth surface generation, contact analysis and
stress calculation. The procedure enabled the correlation of the gear defining parameters such that interference
could be avoided. The gears mesh simulation illustrated the path of contact geometry and enabled a proper load
distribution for the finite element analysis. Compared to other standard spur gears, the designed curved face width
spur gears exhibited a higher bending resistance.
Keywords: Non-standard gear, curved face width tooth, plastic gear, gear mesh.
SOME ASPECTS ABOUT DRIVING WHEEL/RAIL CONTACT IN
STEADY STATE INTERACTION
Traian Mazilu
POLITEHNICA University of Bucharest, Dept. of Railway Vehicles, ROMANIA
The driving wheel/rail steady state interaction and the response to harmonic excitation were studied using a
complex model for track. The starting point for numerical simulations is the Green matrix of the track.
The wheel/rail displacements and the contact forces have been calculated to aim to analyze the particularly case of
driving wheel/rail interaction which is very interesting for corrugation wear issue.
The driving wheel/rail interaction behaviour due to parametric excitation caused by the discretely support of the
track is dominated by the first own frequency for
wheel/rail system. When the passing frequency over the sleepers equals the first own resonance frequency, the
wheel/rail contact forces – the normal force and the traction force - have the highest value and the wheel rolls over
the rail at the critical speed. The numerical results show that the effective traction force can be 8.5% from the
mean traction force. Consequently, the railway traffic at the critical speed must be avoided.
Generally, the driving wheel/rail interaction is characterised by the superposition of the roughness and parametric
excitation due to sleepers. The modulated oscillation phenomenon occurs – the carrier is the effect of the excitation
due to roughness and the modulated is given by the parametric excitation. The spectral components of both the
carrier and the modulated can be added in the pinned-pinned resonant/anti-resonant frequency range, especially.
Due to this effect, the effective traction force is very sensitive to the roughness wavelength of the running surface
and contributes to the rail corrugation.
The effective traction force increases as the tractive power increases. This aspect explains why the heavy
locomotives are more aggressive for rail.
Keywords: driving wheel, rail, steady state interaction.
INFLUENCE OF THE SLIDING SPEED ON THE
ELASTOHYDRODYNAMIC REGIME
Petre Lucian Seiciu
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
ABSTRACT
The study of the elastohydrodynamic (EHD) lubrication regime is characteristic for the heavily loaded gears and
can be modeled on a two disk (SAE) rig. It is very important to observe and determine the lubrication regime
because a full EHD lubrication regime assures low friction and wear, while a mixt lubrications leads to high wear
and traction values that generate surface destruction. The measurements were made for different values of sliding
speed, in order to see its influence on film thickness. There were observed also the influences of: load, temperature
and rolling speed.
Keywords: Elastohydrodynamic lubrication, Hertzian line contact.
TEST-RIG FOR PRESSURE MEASUREMENTS IN AN AEROSTATIC
BEARING
Ilie Muscă
“STEFAN CEL MARE” University, Department of Mechanical Engineering, Tribology and Contact Mechanics
Laboratory, Suceava, ROMANIA
ABSTRACT
The paper presents a test rig for local pressure investigation in an aerostatic or gasostatic bearing system. Using a
simple and performant computer assisted measurement device, pressure evolution in lubrication area can be
measured continuously or at different points, for different pocket geometry forms. Some experimental results are
also presented.
Keywords: aerostatic bearing, pressure measurement, tribology.
HYDRODYNAMIC EFFECTS OF TEXTURE GEOMETRIES ON
JOURNAL BEARING SURFACES
Nacer Tala-ighil1), Patrick Maspeyrot1), Michel Fillon1), Abdelhamid Bounif2)
1) Université de Poitiers, Laboratoire de Mécanique des Solides (LMS), UMR CNRS 6610, FRANCE
2) Université d’Oran, Faculté de Génie Mécanique, Laboratoire de Carburants Gazeux et Environnement,
ALGERIE
ABSTRACT
Lately, the expanding range of tribological applications to the microscopic levels has revived interest in this field.
Actually, little is understood about the subtle effects of variations of a journal bearing’s profile upon its
performance. The surface texturing is expected to make an important contribution to future technologies of
bearing.
Numerical study based on finite difference methods is used to find the tendency of important tribological properties
of a journal bearing such as minimum film thickness, maximum pressure, axial oil flow and friction torque.
The present work is a comparative study of the hydrodynamic effects of a few deterministic texture shapes in a
journal bearing application. The geometry and the size of textures affect load capacity and friction torque. The
parallelepipedic textures show advantages compared to the other geometries for the improvement of the
performances of the bearing. In general, the impact of shapes is more visible for higher asperity area in
accordance with the geometrical differences.
Keywords: texture, lubrication, hydrodynamic, journal bearing.
BEHAVIOUR OF A HYDRODYNAMIC JOURNAL BEARING: TORQUE
MEASUREMENT DURING START-UP
Jean Bouyer, Michel Fillon
Laboratoire de Mécanique des Solides, Université de Poitiers, UMR CNRS 6610, SP2MI, 86962 Futuroscope
Cedex, FRANCE.
ABSTRACT
The start-up friction coefficient in hydrodynamic bearings, used by engineers in the design of bearings, is most
often issued from an approximation. Several studies can be found in the literature on this topic but most of them
are concerned with air bearings or are only numerical. Other studies are more general and deal with the transient
thermal behaviour in journal bearings as well as in thrust bearings. Only few studies are focused on experimental
investigations of the friction coefficient or bush torque measurement. The aim of this study is to provide
experimental measurements of the bush torque during start-up for various static loads.
Keywords: journal bearing, experimental, torque, start-up.
WEAR BEHAVIOUR OF THE AL7175 ALLOY UNDER DIFFERENT
BULK STRESS STATES
M. Buciumeanu, A. S. Miranda, F.S. Silva
Department of Mechanical Engineering - University of Minho, Azurém, 4800-058 Guimarães, PORTUGAL
ABSTRACT
In what concerns the stresses involved in the process, most wear tests (namely those in the pin on disc and the pin
on plate configurations) are usually solely concerned with the stress state in the contact originated by the normal
and the tangential loads applied in the test. In some practical applications, however, besides the local contact
wear stresses, the component might be under additional stress states, either tension or compression. This is, for
example, the case of disc brakes in which thermal deformation of the disc induces bulk stresses. It is reasonable to
expect that the wear behaviour of materials might be affected by the stress states at which they are subjected,
either locally or in the bulk.
The present work presents an investigation of the wear behaviour of the Al 7175 alloy when subjected to different
stress states. It was observed that the bulk stress state has a substantial influence on the wear behaviour of the
material.
Keywords: wear, stress state, Al 7175 alloy.
THE INFLUENCE OF THE APPLIED LOAD ON THE FRICTION
COEFFICIENT OF THE SINTERED IRON BASE BEARINGS
Cristina Teişanu1), Ştefan Gheorghe1), Andrei Tudor2), Ion Ciupitu1)
1)
2)
University of Craiova, Faculty of Mechanics, Dept. of Technologies and Materials, ROMANIA
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
ABSTRACT
In the recent years the iron base sintered bearings production was considerable increased at the expense of the
copper based ones, due to the low cost and availability of the iron powders as well as the higher strength. The
mechanical properties of a part are strongly related to the composition of the materials. For tribological
applications, the properties of the surface are related to the different metallic and intermetallic phases formed in
the material.
The friction nature of the bearing type couple having the bearing bush made from sintered material is a function of
pores size, applied load, velocity, temperature, the quality and quantity of the stored oil and can appear as
hydrodynamic, mixed and limit friction.
The tribological features of the selected iron-copper based materials have been studied using an experimental
device for wear testing of the sliding bearings. The friction coefficient and wear resistance have been analyzed in
dry friction conditions.
The influence of the applied load and p x v values on the friction coefficient was studied. Also, the dependence of
the functioning time until the failure of the bearing (seizing) with the friction coefficient for the applied forces was
analyzed.
Keywords: Friction coefficient, sintered bearings, contact surface, dry friction.
FLAMMABILITY TEST DATA IN RISK ASSESSMENT
Lorena Deleanu1), Dragoş Buzoianu2), Ştefan Crăciunoiu2), Minodora Rîpă1), Constantin Spânu1)
1)
2)
University Dunărea de Jos Galaţi, ROMANIA
ICTCM, Bucharest, ROMANIA
ABSTRACT
This paper reviews the most recent information on standards dealing with testing fire-resistance of hydraulic fluids
in order to emphasis the importance of selecting hydraulic fluids including as basic criteria of reducing fire risk in
particular and general industrial applications, gives information on an original stand for determination of the
flammability characteristics of fire fluids in contact with hot surface and presents preliminary results of the tests.
These test results may be included in a risk assessment in order to enhance the security and health levels in
industry.
Keywords: flammability test, hydraulic fluid, risk assessment.
NITROGEN INFLUENCE ON INDENTATION FRACTURE TOUGHNESS
OF STAINLESS STEEL COATINGS
Mioara Thompson, Liviu Palaghian
University Dunărea de Jos Galaţi, ROMANIA
ABSTRACT
This paper studies some aspects of coatings fracture theory and the possibility of extending Lawn’s equation from
Vickers indenter geometry to the Rockwell one. Indentation tests were performed on stainless steel coatings
deposited on 35.CD.4 steel substrate. The stainless steel coatings were nitrogen added in order to improve the
fracture toughness. A comparison between different nitrogen concentrations has been made, based on the normal
critical load at the first crack appearance. This load was very accurate measured with an acoustic emission stateof-the-art device, Vallen System AMSY4. Based on measured diameters of the ring cracks, the crack length was
calculated. The normal critical load was precisely measured, due to acoustic emission method. Thus, it was
calculated the fracture coefficient, K. A fracture pattern diagram as a function of normal load was plotted for
stainless-nitrogen coating deposited on 35.CD.4 steel substrate.
Keywords: coatings, cracks, indentation test, fracture toughness, acoustic emission.
THE TOOL TO MODEL THROUGH MICRO STRAIN AND MICRO
CUTTING
Antonio Tache1), Carmen Tache2)
1)
2)
PERTOMSERVICE S.A. Bucuresti, ROMANIA
VALAHIA University of Targoviste, ROMANIA
ABSTRACT
The cutter wear is analised by a single hard fixed particle (inclusion) in brittle material. The shakedown pressure
of the inclusion contact is directly proportional to shear field stress of the cutter surface and is function of adhesive
coefficient. The deformation modes of cutter surface are shakedown, ploughing or cutting. The hard inclusions are
assumed to be spherical with constant radius and their position distribution is taken to be Gaussian. Higher hard
inclusions in sliding contact may cut or plough the cutter surface while lower hard inclusions contact cutter
surface elastically. It is analyzed the effect of all the hard inclusions contacts and it gives quantitative prediction of
wear coefficient.
Keywords: abrasive wear, hard inclusions, adhesion, plasticity criteria, micro cutting, wear intensity.
EXPERIMENTAL INVESTIGATIONS CONCERNING THE
MATHEMATICAL MODEL OF HARD DEPOSITS BY HIGH-SPEED
FLAME SPRAYING
Doina Petrescu,, Niculae Napoleon Antonescu, Marian Neacşu
Petroleum – Gas University of Ploiesti, Ploiesti, ROMANIA
ABSTRACT
A complex study was made by the paper’s authors by using certain independent models that take into account the
combustion process, the particles’ dynamic, the fluid’s dynamic and also the particle fluid transfer processes
where it takes place the high-speed flame thermal spraying. In order to realize this study it has been started with
the actual degree of the researches concerning the processes that take place in the combustion chamber.
In the present paper there were studied:
 the fluid’s parameters, the determination of the speed and fluid’s temperatures values (the mixture formed from
the particles and the combustible fluid fuel) from the characteristic points that exist on the particle route;
 the particle-fluid moment transfer;
 the heat transfer;
 the mass transfer during the thermal spraying.
Keywords: modulation, hard coatings, high-speed flame, wear resistence.
CHARACTERIZING THE WEAR PARTICLES OF INTERVERTEBRAL
DISC PROSTHESIS AND THEIR BIOLOGICAL RESPONSE
Monica Creţan Stamate, Mihai Gafiţanu, Ciprian Stamate
POLITEHNICA University of Iassy, Dept. of Machine Design and Mechatronics, ROMANIA
ABSTRACT
Prosthetic debris is the leading factor causing prosthetic loosening and requiring revision surgery. Wear debris is
formed over time with any prosthesis. Factors determining disc arthroplasty survivability are similar to those for
joint replacement technology, and include prosthetic wear, formation of wear debris, and tissue reaction to the
wear debris. All wear debris causes a foreign-body reaction that induces an inflammatory response, which results
in progressive local bone loss (osteolysis) and possible prosthetic loosening and failure. In this paper are
described the nature of particle shape and surface texture, as detected on the particle profile. Detailed surface
characteristics of the particles produced during fretting may well be significant in determining their biological
effects. Careful processing and analysis of the digitised image enabled both the sizes of micro-projections and their
relative numbers to be determined. Such processing of images of a large number of particles generated a
considerable amount of data. AutoCAD and MathCAD were used to establish categories the data and to compare
the nature of fretting particles generated by UHMWPE and, cobalt-chromium-molybdenum. Although showing a
tendency towards a spherical form, all two materials produced different results, with UHMWPE showing the
greatest diversity of textures and sizes.
Keywords: wear, prosthesis, particles, circularity, SEM.
INFLUENCE OF SHEAR STABILITY ON OILS BEHAVIOUR
Sorin Ciortan, Minodora Rîpă, Simona Chiculiţă
University “Dunărea de Jos”of Galaţi, Dept. of Machine Elements, ROMANIA
ABSTRACT
The paper presents a method to establish a link between the shear stability index and service behaviour of motor
oils. A standardized method for shearing stability establishing is combined with appropriated curve fitting and
plotting software in order to obtain the viscosity variations plots during the shearing testing. The plots are used to
optimize the oils choose for specified service requirements.
Keywords: shear stability testing, oil performance.
EXPERIENCES IN LUBRICATION OF NON-NATURAL GAS
FUELLED STATIONARY ENGINES
Franz Novotny-Farkas1), Karin Baumann1), Tibor Leimeter2)
1)
OMV Refining & Marketing, Competence Center Lubes, 2320 Schwechat, AUSTRIA
Gubkin Russian State University of Oil and Gas, Department of Chemistry and Technology of Lubricating
Materials and Chemmotology, Moscow, RUSSIA
2)
ABSTRACT
In Europe, a huge number of generators for electric power powered by those stationary engines are becoming
increasingly popular in regions where these renewable fuel sources are available. Nevertheless, the continuously
pending quality, caloric value and the harmful constituent of the non-natural gas fuel are placing greater demands
on the engine operation and its lubrication system. These phenomena drew our attention to the lubrication issues
of the stationary gas engines. These gas engines can expose the engine oil to severe chemical impact of dirt fuel
impurities, acidity, nitration and oxidation conditions and can be very sensitive to additive chemistry and oil
composition.
In this paper we provide a representative case study and we’ll report about our experiences on lubrication of gas
engines, fuelled with wood gas.
Keywords: biomass gasification, stationary gas engine, lubrication, oil condition monitoring
RESIDUAL STRESSES EFFECT ON FATIGUE LIFE OF ROLLING
CONTACTS
Spiridon Creţu, Marcelin Benchea
“Gh.Asachi” Technical University of Iasi, ROMANIA
ABSTRACT
The fatigue life tests carried out on two groups of ball bearings point out the positive influence of the compressive
residual stresses induced by a previous loading in the elastic-plastic domain.
The values of residual stresses are numerically evaluated by employing a three-dimensional strain deformation
analysis model. By considering the isotropic and non-linear kinematic hardening laws of Lemaitre-Caboche, the
model accounts for the cyclic hardening phenomena. To attain the final load of each loading cycle the two bodies
are brought into contact incrementally. The cyclic evaluation process of both plastic strains and residual stresses
is performed until the material shakedowns.
The von Mises equivalent stress is considered in Ioannides-Harris rolling contact fatigue model to obtain
theoretical lives of the ball bearings groups. The theoretical analysis reveals also greater fatigue lives for the ball
bearings groups with induced residual stresses than the fatigue lives of the group without induced residual
stresses.
Keywords: plastic deformation, residual stresses, rolling contact, fatigue life.
SEIZURE OF A HIGH-SPEED THREE-WAVE JOURNAL BEARING
Daniela M. Buzescu1), Mircea D. Pascovici2)
1)
2)
COMOTI -National Research & Development Institute for Gas Turbines –Bucharest, ROMANIA
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
ABSTRACT
This paper is focused on the geometry and operating parameters of the bearing experimentally studied at NASA
Glenn Research Center by F. Dimofte. It presents two simple thermoelastohydrodynamic (TEHD) models for two
typical mechanisms of seizure of a three-wave journal bearing: seizure during start-up under normal lubrication,
respectively seizure induced by lubricant starvation. A quasi-concentric bearing, typical for high speed
applications is analyzed.. Shaft thermal expansion and a relationship between the viscosity and clearance are
considered in a simplified manner. During start-up, the heat produced by viscous friction is assumed to be rejected
only by the oil flow. Under starvation condition, the heat is assumed to be rejected only through the housing. For
each case, a complex critical dimensionless number (called seizure number) which states the bifurcation between
stable and unstable condition is defined. The predicted results obtained with these models have been validated on
the case- experimentally studied at NASA.
Keywords: wave journal bearing, Seizure, TEHD analysis, high speed, Starved lubrication.
VISCOSITY OF AMORPHOUS MOLECULAR SUBSTANCES
Emanuel Diaconescu, Vlad Flaviu Zegrean, Oana Miron Onciul
University of Suceava, Department of Applied Mechanics, ROMANIA
ABSTRACT
Because the great majority of flow units in a liquid behave instantaneously in a solid-like manner, rheological
properties of molecular liquids subjected to high pressures may be measured by using corresponding molecular
solids. An existing simple shear device previously reported is improved allowing the measurement of the viscosity
of solid paraffin under controlled pressure and temperature. Experimental results show that some viscosity
properties in amorphous solids do not coincide with those found in liquids. To explain this difference, the solid
paraffin structure was investigated by aid of an AFM apparatus. This revealed that the structure is formed of a
mixture of clusters and simple molecules. A possible mechanism of flow in molecular amorphous solid was
advanced which explains the observed discrepancies.
Keywords: paraffin, viscosity, flow units, clusters, rheometer.
HIGH-SPEED HYBRID ANGULAR CONTACT BALL BEARINGS
LUBRICATED BY KEROSENE MIST
Viorel Paleu
“Gh. Asachi” Technical University of Iasi, Dept. of Machine Elements and Mechatronics, ROMANIA
ABSTRACT
This paper presents some experimental research, carried-out on 7206C hybrid angular contact ball bearings
lubricated by oil and kerosene mist. The monitored parameters are the friction moment of the testing bearing, and
the testing device house temperature. The developed tests proved that the hybrid ball bearings lubricated by
kerosene mist run with no problems at light load (200 N) and high speed (20,000 rpm). An equilibrium
temperature less than 480C was reached at 200 N axial load and 20,000 rpm. At 40,000 rpm, the friction moment
and the temperature within bearings are continuously increasing, the test being stopped when a temperature of
600C was reached on the house of the testing device.
Keywords: hybrid ball bearings, high-speed, lubrication, kerosene mist
NEW TEST FACILITY FOR FLUID FILM JOURNAL BEARINGS
Florin Dimofte1), Nicoleta M. Ene2)
1) The University of Toledo at NASA Glenn Research Centre, Cleveland, Ohio, USA
2) The University of Toledo, Toledo, Ohio, USA
ABSTRACT
This paper describes a new experimental rig to test journal fluid film bearings. It has been operating at the NASA
Glenn Research Center (GRC) in Cleveland, Ohio since August 2006. The rig can apply total radial loads of up to
133,000 N (30,000 lbs) and can rotate the shaft to speeds up to 13,000 RPM. The test bearing used in the initial
runs has a diameter of 68 mm and a length of 38 mm. Two such bearings are used to support the total load. The
shaft is also supported by two fluid film bearings. The rig is well instrumented for the measurement of oil flow, oil
inlet and outlet temperatures, bearing sleeve circumferential temperatures and the oil temperatures in oil supply
pockets. The shaft position is monitored by proximity probes. Vibration levels at four locations are also displayed
and recorded. Preliminary tests of wave bearings running at 8,000 RPM and loads to 20,000 N (4,500 lbs) show a
good agreement between the test and prediction data.
Keywords: test rig, fluid film bearings, wave bearing, PVD coatings.
RESEARCH REGARDING OF COMPOSITE MATERIALS UNDER THE
INFLUENCE OF ABRASIVE WEAR
Carmen Florea1), Alexandru Florea1), Mioara Chivu2)
1)
2)
University of Petrosani, ROMANIA
ICEM Bucharest, ROMANIA
ABSTRACT
The method described in the paper will permit to estimate the composite materials performances with different
structures and various working conditions, with a view to estimate useful life of technological equipments parts
which can be made of these materials.
Keywords: metallic composite materials, wear measurement.
INDUSTRIAL GEAR OILS FROM RENEGERABLE FEED STOCKS
Constantin Tănăsescu1), Diana Petre1), Liana Bogatu2), Niculae Napoleon Antonescu1)
1)
2)
Petroleum and Gas University of Ploieşti, ROMANIA
SC ICERP SA Ploieşti, ROMANIA
ABSTRACT
The aim of this research study is to obtain industrial gear oils. The formulation of this type of lubricant is based on
vegetbe oils or mixtures of vegetal oils with more stable base oils and appropriate additives. The study evaluates
the laboratory testing results regarding vegetal oil-based lubricating characteristics and oils obtained from base
oil mixture and suitable additives. The extreme pressure, antiwear properties and biodegradability of the industrial
gear oils composed of vegetal and mineral oils mixtures or vegetal and synthetic oils mixtures are acceptable.
Keywords: industrial gear oils, vegetal oils based lubricants, biodegradable lubricating oil.
GLOBAL METHOD USING EXPERIMENTAL DATA FOR
CHARACTERIZING THE LUBRICANTS DURABILITY
Alexandru Rădulescu1), Irina Rădulescu2), Corneliu Bălan1),
Florin Petrescu3), Nicolette Amelie Popescu Pogrion4)
1)
University POLITEHNICA Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
SC ICTCM SA Bucharest (Mechanical Engineering and Research Institute), ROMANIA
3)
TECHNICAL University of Civil Engineering of Bucharest, Faculty of Technical Equipment, ROMANIA
4)
National Institute for Materials Physics, Magurele, ROMANIA
2)
ABSTRACT
The paper presents a global method for characterizing the durability of lubricants, in order to establish the
moment of changing, using objectives criteria. Three types of lubricants, for essence and Diesel engine, have been
tested. The lubricants were in fresh and used state. For each kind of lubricant, the following tested have been
made: tribological, rheological and microscopical. The principal result is a new methodology, efficient,
performed and ecological for the evaluation and quantification of the wear degree and lubricants durability.
Keywords: lubricants, durability, experiment.
HIP JOINT CONTACT PRESSURE DISTRIBUTION PRIOR AND AFTER
TRIPLE OSTEOTOMY
Tiberiu Laurian1), Lucian Marinca2) , Andrei Tudor1) and Felix Pârvu1)
1)
2)
POLITEHNICA University of Bucharest, Dept. of Machine Elements and Tribology, ROMANIA
Clinic Hospital for Orthopaedics and Traumatology “Foisor”, Bucharest, ROMANIA
ABSTRACT
A 3−D reconstruction method based on CT scans was used to compute the femoral head coverage for dysplasic
hips prior and after reconstruction surgery. The triple osteotomy technique was used to “reorient” the acetabulum
of severe dysplasic hips. After 3−D reconstruction of the pelvis and the medial part of the femur, a finite element
model (FEM) was created which allowed for a static analysis contact study to quantify the contact pressure
distribution in the hip joint. After 3D reconstruction of the pelvis and the medial part of the femur, using a
specialized software MIMICS (Materialise), a finite element model (FEM) was created with ABAQUS/CAE
(Abaqus Inc.). A material assignment was performed for each element. A solution was found to account for the
presence of the cartilage layers. The FEM allowed for a static and dynamic analysis contact study to quantify the
contact pressure distribution in the hip joint.
Keywords: hip contact pressure, hip dysplasia, triple osteotomy, 3D bone reconstruction.
VEGETAL OILS AS LUBRICATION MATERIALS
Camelia Calomir, Ioan Ştefănescu, Liviu Şolea, George Chiriţă
University “Dunărea de Jos” Galaţi, ROMANIA
ABSTRACT
The success of vegetal oils is related to their biodegradability and reduced toxicity but a wide use is limited by
their insufficient stability in time. Biodegradable oils have ecological advantages, being comparable or better than
mineral ones.
This paper presents experimental results on oxidation resistance of sunflower oil used as lubrication materials.
Tests were done using both unadditivated sunflower oil, for grades as obtained after different steps of
manufacturing process and additivated sunflower oil.
The authors established that the vegetal oil obtained after the first two steps of manufacturing process presents the
most reduced oxidation phenomena and the friction coefficient shows that extraction coars sunflower oils oxidized
after 5h and additivated with the 2% ascorbic acid has a the best behaviour to the hydraulic oil H 32.
Keywords: lubrication materials, oxidation phenomena, friction coefficient.
ELECTROCHEMICAL AND MECHANICAL CHANGES
ON FATIGUE CORROSION DAMAGED SURFACES
Svetlana Băicean, Liviu Palaghian, Sorin Ciortan, Mioara Thompson
University "Dunărea de Jos" Galaţi, ROMANIA
ABSTRACT
The paper presents some surfaces changes aspects in fatigue corrosion damage based on electrochemical,
mechanical profilometry and microscopically analyze of cylindrical and plate steel specimens. The researches
have demonstrated that principal cause of damage for rotating specimen is localized pitting corrosion and for
plate specimen is generalized surface corrosion, manifested by oscillatory evolution of electrochemical
parameters.
Keywords: fatigue, corrosion, electrode potential, polarization, crack, damage.
DYNAMICS OF HIP ARTIFICIAL JOINTS WEAR
Lucian Căpitanu, Aron Iarovici, Justin Onişoru, Constantin Ţigăneşteanu, Marius Dima
Institute of Solid Mechanics, Romanian Academy, Bucharest, ROMANIA
ABSTRACT
In the present paper the authors try to evaluate, based on the results obtained from experimental and numerical
previous studies, the wear evolution in the components of a Total Hip Prosthesis (THP), during the service period.
Topographic investigations of polyethylene cup and femoral head surfaces, of a modular total hip prosthesis
retrieved after a service period of 10 years, are made. The aim of the study was the determination of: state of
surfaces (roughness, microhardness), surfaces wear type, localization and microscopic investigation of damages,
wear mechanism identification.
Keywords: wear, biotribology, total hip prostheses
SHEAR STABILITY AS OILS’ PERFORMANCE INDICATOR
Sorin CIORTAN, Minodora RÎPĂ, Simona CHICULIŢĂ, Constantin SPÂNU
University "Dunărea de Jos" of Galati, ROMANIA
ABSTRACT
The paper presents a comparative analysis between the shear stability tests results and four ball tests results for
some industrial oils. This correlation is used for establishing the way how the mechanical solicitations in oils
during service life affect the viscosity modification and, thus, the quality of oils.
Keywords: shear stability testing, oil performance, standard testing methods’ comparison.
ON TRIBOLOGICAL BEHAVIOUR OF THERMO-CHEMICAL
TREATED STEELS AFTER THERMO-MAGNETIC TREATMENTS
Carmen Penelopi PAPADATU
“Dunarea de Jos” University of Galati, ROMANIA
ABSTRACT
The paper presents an analysis on two grades of steel, subjected to nitrocarburized or nitrided thermo-chemical
treatment after thermo-magnetic treatments. Based on the concept of tribosystem, pairs of steel rollers were tested
in order to evaluate the tribological behaviour, using an Amsler machine, under rolling sliding motion, with two
sliding degrees, different contact loads and different testing time periods. I tried toestimate the durability of these
materials, the evolution of the surface structure parameters, at different moments during the tests, after applying
different thermo-chemical treatments and thermo-magnetic treatments (considered as non-conventional
treatments).
The performed tests allowed establishing the influence of the thermal, magnetic and mechanical parameters on the
behaviour of these two steel grades when tested under rolling-sliding conditions.
Keywords: thermo-magnetic, nitrocarburation and nitrided treatments, wear, X-ray diffractometry.
STUDY OF WEAR EVOLUTION FOR A HYDRAULIC OIL
USING A FOUR BALL TESTER
Constantin Spânu, Minodora Rîpă, Sorin Ciortan
University “Dunărea de Jos” of Galaţi, Galaţi, ROMANIA
ABSTRACT
Time is crucial for the wear of materials. Time of an experiment must be long enough to obtain an observable wear
but no so long to make the experiments expensive. For determining anti-wear properties of the hydraulic oils the
standard EN ISO 20623:2004 indicates 1 hour under an applied load of 150 N. The Romanian standard STAS
8618_1979 does not specify anything about this. The present paper had analysed the wear evolution for a hydraulic
oil, using the four ball tester, in order to determine the optimum duration for such a test. Supplementary, the
relation between mean scar diameter and the removed volumes of ball material is analysed.
Keywords: Hydraulic oil, four ball machine, anti-wear properties, mean scar diameter.