Recent Researches in Manufacturing Engineering
SOME ASPECTS REGARDING MATERIALS USED IN
NON-METALLIC ELEMENTS CONSTRUCTION OF
ELASTIC COUPLINGS
Dr.eng. MARILENA RADU, Prof.dr.eng. DAN SĂVESCU
Intellectual Property Department, Product Design and Robotics Department
TRANSILVANIA University of Brasov
B-ul Eroilor nr.29, 500036, Brasov,
ROMANIA
[email protected], [email protected] http://www.unitbv.ro/
Abstract: This paper presents aspects regarding the construction of couplings with bolts using non-metallic
elements, e.g. rubber, having different hardness, the elements involved in torque transmission, in this case
elastic elements, having also different dimensions or forms, in the way to have a good elasticity and capacity
of vibration absorbtion. In paper there are also presented: the construction of non-metallic elements, the
method of experimental determination of longitudinal elastic modulus “E”, longitudinal elastic modulus “E”
values of three rubber qualities being used in FEM modeling, researches due on non-metallic elements from a
new coupling with bolts and rubber elements.
Key-Words: Elastic coupling, non-metallic elements, the physic-mechanic characteristics, the method of
experimental determination.
1 Introduction
2
The recommended non-metallic
materials for elastic couplings
The elastic couplings with non-metallic elements
accomplish the following functions: transmissions of
rotation motion and torque moment; damping of
shocks and vibrations; taking over axial, radial,
angular/mixed deviations. The non-metallic elements
are using, especially, for their big elasticity, a good
taking ower capacity of shocks and vibrations (to
suspensions of different equipments, the elastic
coupling design, in modifying of frequency by
resonance of a different subassemblies a.s.o.) having a
simple constructive forms.
In figure 1, a, is presented an original solution of an
elastic coupling with intermediary non-metallic
elements.
The non-metallic element has various shapes (see
figure 1, b…d), and it is made of various qualities of
rubber. The torque moment is transmitted from the
driver semi coupling 1 to the non-metallic elements 3,
of various shapes, through all the four cylindrical bolts
4, fixed rigidly on the driver semi coupling 1, and
through the intermediary disc 7 to the driven semi
coupling 2. The stresses which appear are compression
in the sense of the motion, in the area in front of the
bolts, crushing on the contact surface, and traction in
the area defined by section B-B.
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Rubber is a technical product consisted by
macromolecular compound, with long and flexible
linear chains, featured behavior by elastomer. It is
arise various rubber types (natural rubber, synthetic
rubbers), each from them were presented particular
advantages and disadvantages in specific
utilizations. The rubber macromolecule may move
one towards one to raised relative temperatures and
mechanic tensions. But and after rubbers cooling,
they may keep flow capacity (unlike plastic
materials and fibers) then on them action mechanic
forces, mostly if applied tension actions long time;
to very low temperatures rubbers may be come
breakables, losing elastic deformation capacity [2].
In rubber composition come into the following groups of
components: elastomers, active ingredients (black
pigment which affected the vulcanized process mode),
softening agents (they are adding flow capacity and they
are growing up elasticity and resistance at low
temperatures), inactive ingredients (they are reducing
rubber cost), protection groups and reticular groups. The
natural rubber is a product of vegetal origin contained in
secreted latex (watery suspension) by some plants (hevea
brasiliensis) which they are cultivated in countries with
tropical/equatorial clime like Brasilia, Malaysia.
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Recent Researches in Manufacturing Engineering
A-A
D
A
2
4
5
3
B
10
D1
1
De
C
6
C
7
11
8
B
Ds
a
A
L
c
b
d
Fig. 1: Elastic coupling with cylindrical bolts and intermediate non-metallic elements
The thermoplastics
The elastomers
Shore A
Shore D
The thermoplastic
Fig. 2. The classification of rubber types depending on hardness
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212
The transversal elasticity modulus
Recent Researches in Manufacturing Engineering
The elastomers
The thermoplastic
The thermoplastics
The thermorigides
Steel
Temperature
Fig. 3. The classification of rubber types in function by transversal elasticity modulus and temperature
Table 1. The thermic and mechanic properties’s types of compound rubber
0
Sh
30…90
%
…1000
Natural Rubber
Policloroprenic
-40…+140
5…27
40…95
… 800
rubber
Butadien-stirenic
-30…+130
5…24
40…95
… 700
rubber
Butil rubber
-50…+150
4…17
40…90
… 900
Butadienacrilonitrilic -30…+130
5…24
40…95
… 700
+
rubber
Hypalon rubber
-40…+140
4…20
40…95
… 600
Siliconic rubber
-100…+220
2…8
40…90
… 500
•
Viton rubber
-60…+220
8…16
60…95
… 300
+
Used notations: + high stability; - unstable (to degrade); • medium stability.
-
-
+
+
+
-
•
+
+
+
-
-
+
+
+
+
•
+
•
+
•
+
•
•
+
-
+
•
+
•
-
+
•
+
•
+
Table 2. The physic-mechanic characteristics of nonmetallic
materials for elastic elements of elastic couplings
Crt. Type of coupling
The
physic-mechanic
Nr.
characteristics
of
nonmetallic materials
ElonUltimate Hardgation
tensile ness,
at break,
strength,
0
2
Shore
A,
%
N/mm
min.
min.
min.
1. Elastic
coupling
15
85 ± 5 200
with frontal disc
2. Elastic
coupling
17
70 ± 5 300
with rosette
3. Elastic
coupling
17,5 65 ± 5 250
with prisms
4. Elastic coupling with
17,5 75 ± 5 400
nonmetallic slides
5. Elastic coupling with bolts
19
60 ± 5 500
This type of rubber is stable to water, isn’t dissolving in alcohol
acetone, it is dissolve in toluene, xilen or benzene. Vulcanized
natural rubber is distinguishing through high elasticity, at normal
temperature and also having god dynamic properties. The
synthetic rubber is synthetic polymers which may be processing
and vulcanized like natural rubber, obtained by polymerize
process or copolymerize, named monomer.
In figure 2 is presented a classification of rubber types in
function hardness. The classification of rubber types is
realized taking into account the using domains as follows:
1. rubbers for general using (isoprene, butadiene,
butadiene – styrene), used in products having the physical
properties of elastomers (tires, conveyance belts);
2.rubbers for special utilizations (etilen – propylene –
dienic, butadiene – nitrilic), used to products that
needs to have resistance to different chemical
agencies, functioning at high or low temperature.
The thermoplastic elastomers are mixed between the
classic elastomers and thermoplasts.
978-960-474-294-3
Acids, bases,
salts
N/ mm2
5…28
Steam
C
-30…+120
Hardness, Breaking
elongation,
Water
0
Ultimate
tensile
strength,
ASTM 3 Oil
rubber Temperature
by utilization,
ASTM 2 Oil
Type of
compound
ASTM 1 Oil
Resistance in:
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Recent Researches in Manufacturing Engineering
as seen in fig 5.
A comparison between them is presented in figure 2 and
figure 3, a comparison made concerning transversal
elasticity modulus and hardness. The thermoplastics are
non reticulate rubbers; they have elastic energy and are
able to function at high temperatures. The thermorigides
are powerful reticulate materials; they have elastic
energy, but not soften and decompose generating to high
temperatures [4]. This severe classification was realized
using the transversal elasticity modulus diagram, in
function on temperature, as seen in figure 3.
In table 1 are presented the principal thermo and
mechanical property’s types of compound rubber
offered by literature [1]. Table 2 presents the
physical and mechanical characteristics of nonmetallic materials utilized as elastic elements in
construction of elastic couplings [3].
Fig. 5. The device for reading of sample deformation
The deformation was read to each loading/unloading with
weights beginning with 1 kg (10N) until 5 kg (50N), with 1
kg rate [3]. After each loading/unloading was realized the
reading of sample deformation in those four marked points,
it was processing the results and by using the Hooke’s
relation was determined the longitudinal elastic modulus
“E” (ENR, ENBR, EEPDM) corresponding of each sample.
These values of longitudinal elastic modulus were
utilized in real determination of torque moment,
comparison with the theoretical values, and used in
FEM modeling of non-metallic shapes.
3 Problem Solution
In producers’ catalogues of different companies are
not indicated rubber qualities for elastic elements
used in couplings construction. As can be seen, in
literature there are not specified datailes about
longitudinal elastic modulus “E”. The non-metallic
different types of rubber qualities:
- NR - natural rubber;
- N.B.R. - acrilonitrilic rubber;
- E.P.D.M. propilen-dienic rubber.
For each rubber quality was determining the value
of longitudinal elastic modulus “E using a very
simple and known methodology.
P3
P2
P1
P3
P4
2
P4
2
3
1
3
1
4
P2
4 Conclusion
Following the results presented in this paper, it is
possible to formulate the following conclusions
concerning the materials used to realize elastic
couplings with non-metallic elements:
¾ It exists a various area by non-metallic materials
(eg.: natural rubber, butadiene-styrol rubber, perbunan
N, polyurethane, neoprene, EPDM, chloroprene etc.)
which may be used in non-metallic elements
construction, components of elastic couplings.
¾ Depending on materials hardness from which is made
the non-metallic element, it may obtain different rigidities.
¾ The rigidity of one non-metallic element, realized by
one rubber quality, may be influenced by homogenization
degree of composition used to mould casting.
¾ The elastic couplings with nonmetallic elements
presents the following advantages:
- its have great resilience;
- presents big capacity of damping;
- attenuate noise (because eliminate the contact metal on metal;
- they are simple as constructive point of view;
- they have a more small cost comparative with elastic
couplings with metallic elements; they are electro isolated.
P1
a
b
Fig. 4. The experimental determination of longitudinal
elastic modulus “E”
The method of experimental determination of longitudinal
elastic modulus “E” is presenting in figure 4; three samples,
3 having a cylindrical form and different quality of rubber
were tested through this method. Each sample was weighed
with an analytical balance and determined the mechanical
and dimensional characteristics. For those two identical
metallic discs, 1, 2 (see figure 4), realized from duralumin,
was determined the dimensional characteristics. Each nonmetallic sample was placed between the two metallic discs,
1 and 2, but on the disc 2 where marked four points
References:
[1] V.V. Jinescu, Physic properties and plastice materials
thermomechanics, vol. I. Technic Publishing, 1979.
[2] D. Mazilu, Moulds for rubber. Technic Publishing, 1975.
[3] M. Radu, Theoretical and experimental studies
concerning couplings with non-metallic elastic elements,
Doctoral thesis, Transilvania University of Braşov, 2005.
[4] D.S. Vasilescu, Operator books from rubber processing
industry. Technic Publishing, Bucharest 1981.
( P1 ...P4 ), in which was determined the sample’s
deformation. The reading of sample deformation was
realized by a micro limit apparatus having the detector fixed,
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