Department of Machine and Industrial
Product Design
Contact person: Dr. Tibor Goda (e-mail: goda.tibor@gt3.bme.hu)
LUBRICATION AND FRICTION PREDICTION
GM research topics relating to this area : 8, 10, 65
Initial guess for the film thickness
Competence in:
(distance between mean surfaces at the
given node)
1. Modeling of adhesion
2. Boundary lubrication
(shear strength of
the boundary layer)
3. Numerical modeling
of fluid and mixed
friction
Geometrical sizes of the seal and the rod
Material properties of the rubber seal (E,n)
Sealed pressure (psealed)
Rod speed (outstroke+instroke)
Fluid viscosity at atmospheric pressure (m 0)
Pressure viscosity coefficient (a)
Combined surface roughness of the rod and
the seal (s,R,h)
Coefficient of friction at asperity contact (f)
Length of the sealing zone (L)
Number and coordinates of contact nodes
Static contact pressure at the contact nodes
(psc)
Influence coefficient matrix for the contact
nodes (Iij)
Static film thickness at the contact nodes (Hs)
Calculation of leakage
and friction force
Department of Machine and Industrial Product Design
Contact
analysis
(GreenwoodWilliamson
contact model)
Contact pressure
due to asperity
contact (pcontact)
t
Discretized Reynolds
equation (linear algebraic
equations) non-linearity induced
by pressure dependent viscosity
Calculation of the total pressure
(pt=pfluid+pcontact)
 I p  p 
ik
Calculation of the
truncated film
thickness (hT)
Fluid pressure (pfluid)
Location of the full film and the cavitated regions
N
k 1
Calculation
of the flow
factors
sc k
Calculation of seal deformation
induced by hydrodynamic and contact
pressure
Updated film thickness
Hi  Hs 
N
 I p
ik
k 1
t
 p sc k
2
LUBRICATION AND FRICTION PREDICTION
4. Oil/grease lubricated sliding contact
4000
80
3000
60
2
y = -0.0003x + 1.9665x + 1956.8
2000
40
1000
-0.7963
y = 862.87x
0
0
20°C
500
1000
1500
8
100
Grease Molykote PG 54
20
0
2000
Friction force, N
5. Modeling of
rheological
behavior of
lubricants
Shear stress, Pa
5000
Viscosity
Viscosity, Pas
Shear stress
h1 = 1um
measured
h1 = 0.5 um
h1 = 0.15 um
h1 = 0.2 um
Diapragm seal, l =100 mm,
6
4
Rmax=2 mm
2
h  0.2 Pas, t bound = 0.43 MPa,
0
0
0.02
0.04
0.06
0.08
Sliding speed, m/s
Shear rate, 1/s
Present research activity of the department in this field:
EU FP6 research project „Knowledge-based Radical Innovation Surfacing for
Tribology and Advanced Lubrication” (EU Project Reference NMP3-CT-2005515837, www.kristal-project.org)
References:
[1] Kozma, M.: „Hydrodynamic and boundary lubrication of elastomer seals”, 19th International
Conference on Fluid Sealing, Poitiers, France
[2] Goda T. J.: "Numerical modelling of lubrication in reciprocating hydraulic rod seals„, Proceedings of
sixth conference on mechanical engineering, ISBN 978-963-420-947-8, (2008)
0.1
RUBBER PHYSICS
CONTACT MECHANICS, RUBBER FRICTION (SLIDING
AND ROLLING), FE MODELLING
GM research topics relating to this area : 31
Competence in:
1. Modeling of the non-linear, time- and
temperature-dependent material behavior
of rubber and rubber-like materials
2. Characterization of the asphalt’s
surface topography (Power Spectral Analysis,
surface roughness measurements, etc.)
3.57
log10APSD
-3
A PSD [μm4]
qx, qy [μm-1]
3.90
-3
-0.3
3. Contact modeling of rubber/ rough
counterpart sliding pairs
Department of Machine and Industrial Product Design
-6.59
-0.3
log10qx
log10qy
-7.05
-0.3
log10qx
4
RUBBER PHYSICS
CONTACT MECHANICS, RUBBER FRICTION (SLIDING
AND ROLLING), FE MODELLING
4. FE modeling of hysteresis induced rolling
and sliding resistance
5. FE modeling of hysteresis
induced and friction related heat
generation (thermo-mechanical
coupled analysis)
Present research activity of the department in this field:
EU FP6 research project „Knowledge-based Radical Innovation Surfacing for Tribology
and Advanced Lubrication” (EU Project Reference NMP3-CT-2005-515837, www.kristalproject.org)
References:
[1] Goda, T.; Pálfi, L.; Váradi, K.; Garbayo, E.; Bielsa, J.M.: “FE prediction of the hysteretic component of
rubber friction: importance of the Maxwell-parameters”, Fall Rubber Colloquium, (2008), pp. 128
[2] Felhős, D.; Xu, D.; Schlarb, A.K.; Váradi, K.; Goda, T.:”Viscoelastic characterization of an EPDM
rubber and finite element simulation of its dry rolling friction”, EXPRESS POLYMER LETTERS, Vol. 2,
No.3, (2008) pp.157-164
Department of Machine and Industrial Product Design
5
FE THERMAL MODELLING
GM research topics relating to this area : 67
Temperature [°C]
Competence in:
1. Transient and steady-state FE
thermal modeling (heat partition,
thermal contact resistance,
contact conductive heat flux,
etc.)
Temperature [°C]
195
195
Z
Z
27
X
X
I/a
II/a
T °C
Z
2. Stick-slip related thermal
problems
27
194
X
X
Z
110
#1
#2
POINT A
27
27
#1
POINT B
I/b
Department of Machine and Industrial Product Design
195
110
#2
3. Coupled thermo-mechanical
analysis
T °C
II/b
6
FE THERMAL MODELLING
4. Moving and distributed
heat source models
Present research activity of the department in this field:
Hungarian National Scientific Research Foundation project: „Friction behaviour
and failure mechanisms of polymer, elastomer, ceramic and composite structural
components”, OTKA (NI 62729)
References
[1] Lestyán, Z.; Váradi, K.; Albers, A.: „Contact and thermal analysis of an alumina-steel dry sliding friction
pair considering the surface roughness”, TRIBOLOGY INTERNATIONAL, Vol. 40, pp. 982-994 (2007)
[2] Fekete, G.; Váradi, K.; Leali, M.; Bottarelli, F.: "Thermal FE analysis of a pneumatic cylinder„,
Proceedings of sixth conference on mechanical engineering, ISBN 978-963-420-947-8, (2008)
Department of Machine and Industrial Product Design
7
WEAR DETECTION AND SIMULATION
GM research topics relating to this area : 101
Competence in:
1. FE wear simulation
Start
Initial geometry
FE contact
calculation (instroke)
Nodal Contact Normal Stress
Specific wear rate
Wear calculation
Nodal wear depth
Moving the nodes
New geometry
FE contact
calculation
(outstroke)
Nodal Contact Normal Stress
Wear calculation
Nodal wear depth
Moving the nodes
New geometry
End
Department of Machine and Industrial Product Design
8
WEAR DETECTION AND SIMULATION
2.56
0
2. Modeling and interpretation of typical
wear mechanisms
z
[μm]
3. Characterization of worn surfaces
- 5.56
[mm]
x
[mm]
y
3
3
Present research activity of the department in this field:
Hungarian National Scientific Research Foundation project: „Friction behaviour
and failure mechanisms of polymer, elastomer, ceramic and composite structural
components”, OTKA (NI 62729)
References:
[1] Kónya, L.; Váradi, K.: „Wear simulation of a polymer-steel sliding pair considering temperature- and
time-dependent material properties”, in Friedrich, K.; Schlarb, A.K. (editors) „Tribology of Polymeric
Nanocomposites”, TRIBOLOGY AND INTERFACE ENGINEERING SERIES, No. 55, Elsevier, (2008)
ISBN 978-0-444-53155-1
Department of Machine and Industrial Product Design
9