Time-dependent elastohydrodynamic analysis
of cam-roller contacts
Mohammad Shirzadegan
Roland Larsson
Andreas Almqvist
Division of Machine Elements
Luleå University of Technology, Sweden
Tribodays 2015, Nynäshamn
1
Elastohydrodynamic Lubrication
• is found in …
©
2
©
©
Aim of study
• Develop a model for fully deterministic
steady state and time dependent
simulation of finite EHL contacts.
• The model is used to perform numerical
simulation of cam and roller follower
contacts, over a complete engine cycle
with varying cam operating conditions.
3
Simulation of EHL contacts
Reynolds
Rheology
EHL
Force
balance
4
Elastic
deformation
Different roller geometries
𝑅𝑓
𝑅𝑦
𝑅𝑦 = ∞
𝑅𝑥
𝑅𝑥
𝑅𝑥
𝑅𝑦
𝑅𝑥
𝑅𝑓
Roller with rounded corner
5
𝑅𝑥
Crowned Roller
𝑅𝑥
Unprofiled Roller
Reynolds
equation
Linear
elasticity
equations
• Boundary
• Domain
Solver:
6
Steady sate simulations
 Validation
Inputs
𝐹 = 992.4 𝑁
𝑅𝑥 = 0.01905 𝑚
𝑚
𝑈𝑒 = 24.87
𝑠
𝐷 = 0.125
* [1]
Case A
𝜂0
Luleå
1.294
1.495
0.237
Case B
17.9 × 10−3 2.4 × 10−3 𝑃𝑎 𝑠
0.287
𝛼
14 × 10−8
0.96 × 10−8 𝑃𝑎−1
 EHL elliptical contact
[1] Nijenbanning.G, Venner C.H, Moes,H.,’’ Film thickness in elastohydrodynamically lubricated contacts’’,
7
7 1994,SSDI0043-1648(94), 06458-T
Results: Steady sate simulations
 Pressure distribution
Ph = 1.5 GPa
Ph = 1.25 GPa
Ph = 1.8 GPa
 Pressure & film thickness (axial direction)
1.2
1.0
0.8
0.6
0.4
0.2
0
0
0.1
0.2
0.3
Y
8
0.4
0.5 0
0.1
0.2
0.3
Y
0.4
0.5 0
0.1
0.2
Pressure
Film thickness
0.3
Y
0.4
0.5
Time dependent simulation
 Validation
𝑋𝑑 = −0.75
𝑋𝑑 = 0
9
[1] Venner: Transient Analysis of Surface Features in an EHL Line Contact in the Case
of Sliding
𝑋𝑑 = −0.5
𝑋𝑑 = 0.5
Time dependent simulation
10
𝑋𝑑 = −0.75
𝑋𝑑 = −0.5
𝑋𝑑 = 0
𝑋𝑑 = 0.5
Time dependent inputs
 Input parameters
Load
Velocity
Radii of
curvature
cam
11
Results: Time dependent simulations
 Pressure distribution
T=0 [-]
T=17 [-]
12
T=12 [-]
T=20 [-]
Results: Time dependent simulations
 Pressure & film thickness (axial direction)
T=0 [-]
T=17 [-]
13
T=12 [-]
T=20 [-]
Results: Time dependent simulations
 Film thickness
14
Conclusion
 A fully coupled isothermal numerical model for
simulating the EHL finite line contacts was developed.
 The model was proven feasible for time-dependent
analysis of finite EHL line contacts found in real
applications such as the one typically found in a cam
mechanism.
15
Acknowledgements
16
17