Simulating a Rail Wheel and Track setup for determining induced stress and studying effect of bearing load on Fatigue life of the model
Objective
To Perform a static structural analysis on the Railwheel and Track setup using Ansys
Compare a user defined result with inbuilt results.
Importing the model
The CAD model is imported and viewed in spaceclaim and making sure there are no errors in the geometry.
Simulation Setup
Contact Definition
The material is chosen as structural steel.
Contact - 1
The outer surface of the wheel and top surface of the track will come in contact. Hence a frictional contact is defined between them with a frictional coefficient of 0.3
Contact - 2
A frictionless contact is defined between the inner surface of wheel and outer contact area of shaft. It is done to give the bearing effect.
Joint Creation
Three Joints are created in this setup, they are fixed joint, Translational joint and Planar joint
Fixed Joint - The two side surfaces of the track are selected and fixed joint is applied. It is made to ensure that track doesn't have any degree of freedom.
Translational Joint - The Outer surface of shaft is selected and a translational joint is defined. This is done inorder to define joint displacement in analysis settings.
Planar Joint - The wheel must not move in away from track in lateral direction, hence a planar joint is defined for the wheel such that it always stays in plane with track.
(Joint - 1) Fixed Joint
(Joint - 2) Translational Joint
(Joint - 3) Planar Joint
Mesh generation
The contact area between the wheel and track where stresses occur are meshed with a face sizing of 35mm
Other area of the model are meshed with an element size of 50mm
Analysis settings
Displacement
The shaft is given a displacement of 500 mm in 5 steps , with 100 mm displacement for each step.
Bearing Load
Two different bearing load cases are done.
Case (1) - A bearing load of 100000 N is defined
Case (2) - A bearing load of 500000 N is defined ( 5 times the load value of case (1) )
Results
The model is solved and following results are generated Total deformation, Equivalent strain, Equivalent stress, Fatigue tool (Life in terms of number cycles) and a USER DEFINED result
The force-convergence plot is viewed and it can be concluded that the model results have converged without any convergence issues.
Case (1)
Total deformation
Equivalent Stress
It is clearly seen that stress is created on the contact area between wheel and track but the stress induced area is not clearly visible.
Area in which stress is induced is zoomed in and results are viewed.
Equivalent Strain
Case (2)
Total deformation
Equivalent Stress
Equivalent Strain
Comparing the results of two cases
Case (1) bearing Load - 100000 N
Case (2) bearing load - 500000 N
Total deformation - From the results it can be seen that total deformation stays the same on both cases
Equivalent Stress - Equivalent stress has increased from 146.89 Mpa in case (1) to 608 Mpa in case (2)
Equivalent Strain - Equivalent strain has also increased from 1.167-003 mm/mm in case (1) to 3.3113e-003 mm/mm in case (2)
Life of the model - Minimum number of life cycles has decreased from 4.1665e+005 cycles in case(1) to 2786.2 cycles in case (2)
Hence it can concluded that the increase in the bearing load causes an increase in induced stress and strain values , which ultimatley results in reduced fatigue life.
The model must be changed in order to accomodate an increased load from case (2) and have increased fatigue life.
USER-DEFINED RESULT
In the case (1) bearing load 100000 N , an user defined result for the total deformation is solved.
The expression for total deformation is sqrt(Ux^2+Uy^2+Uz^2).
It is same as inbuilt Total deformation value. Like this other specific results also can be requested by user.
Google drive link for the ansys file
https://drive.google.com/file/d/19smE9CankJPcxQl8xqWhSx5fgt7AKIpM/view?usp=sharing