Impact stress on the body

lkwarm · March 25, 2015, 21:37

Software: ANSYS 15.0 Workbench
Application: Transient Structural analysis

I am trying to simulate impact stresses on 2 contacting bodies which are rotating about different axis. One of the body is assumed to be at constant rotational velocity and the other body is torsional spring loaded. Both the bodies come into contact and rebound and again come to contact.

My duration of interest is just 5 ms during which both the bodies come into contact thrice. The contact(frictional) formulation was done using pure penalty formulation. The simulation was successfully converged, but the results do not fall in the expected or experimental results range.

As the velocities and the contact stress obtained from the analysis are way higher than the experimental results i was thinking, this might be due to not including damping forces for the system. Using damping controls in analysis settings. Is it a right way to go forward with?.

Also high contact stress is the reason for high rebound velocity. Can you suggest me some method to reduce/ dampen the contact impact stress?.

siw · March 30, 2015, 13:56

The total time of 5 ms is very short for implicit time integration FEA; e.g. Transient Structural in ANSYS Mechanical. Are you using adaptive time stepping or a constant timestep? Can you use explicit time integration in Workbench (i.e. ANSYS Explicit STR)? Then you can use Body Interactions for the collision rather than a non-linear Contact (NL contacts greatly slow down simulations), see http://www.ansys.com/Products/Simula...licit+Dynamics.

lkwarm · March 30, 2015, 16:50

Thanks siw for your reply.. I know implicit scheme is really slow for the solution but I was unable to give nonlinear inertial loads in explicit.. So I went on to use implicit. I am not using automatic time stepping.. In order to reduce the simulation time I am using plane strain model. I have a different question here.

In plane strain models, what is the assumed thickness of the body. When I apply a load I can see the body accelerating, so there is an assumed thickness and hence mass for the assembly.. Thanks for your reply in advance

March 25, 2015, 21:37	Impact stress on the body	#1
lkwarm New Member Azif Ali Join Date: Mar 2015 Posts: 2 Rep Power: 0	Software: ANSYS 15.0 Workbench Application: Transient Structural analysis I am trying to simulate impact stresses on 2 contacting bodies which are rotating about different axis. One of the body is assumed to be at constant rotational velocity and the other body is torsional spring loaded. Both the bodies come into contact and rebound and again come to contact. My duration of interest is just 5 ms during which both the bodies come into contact thrice. The contact(frictional) formulation was done using pure penalty formulation. The simulation was successfully converged, but the results do not fall in the expected or experimental results range. As the velocities and the contact stress obtained from the analysis are way higher than the experimental results i was thinking, this might be due to not including damping forces for the system. Using damping controls in analysis settings. Is it a right way to go forward with?. Also high contact stress is the reason for high rebound velocity. Can you suggest me some method to reduce/ dampen the contact impact stress?.

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March 30, 2015, 13:56		#2
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 733 Rep Power: 25	The total time of 5 ms is very short for implicit time integration FEA; e.g. Transient Structural in ANSYS Mechanical. Are you using adaptive time stepping or a constant timestep? Can you use explicit time integration in Workbench (i.e. ANSYS Explicit STR)? Then you can use Body Interactions for the collision rather than a non-linear Contact (NL contacts greatly slow down simulations), see http://www.ansys.com/Products/Simula...licit+Dynamics.

March 30, 2015, 16:50		#3
lkwarm New Member Azif Ali Join Date: Mar 2015 Posts: 2 Rep Power: 0	Thanks siw for your reply.. I know implicit scheme is really slow for the solution but I was unable to give nonlinear inertial loads in explicit.. So I went on to use implicit. I am not using automatic time stepping.. In order to reduce the simulation time I am using plane strain model. I have a different question here. In plane strain models, what is the assumed thickness of the body. When I apply a load I can see the body accelerating, so there is an assumed thickness and hence mass for the assembly.. Thanks for your reply in advance