5 Replies Latest reply on Aug 7, 2012 10:04 PM by Umang Dighe

# contact stress

Hi all !

I am trying to simulate the stresses for a flat surface sitting on a cylinder. I understand that the contact surface is just a line. Can anyone tell me how to proceed for the stress analysis ? Is this non linear ?

The flat plate sits on the cylindrical wheel and the plate is loaded .

Thanks

Umang

• ###### Re: contact stress

Hi Umang: you are correct, it's actually nonlinear. This falls into the category of "Hertzian contact stress", for which solutions have been worked-out (there are explanations on wikipedia about this). It can be difficult to get convergence in a finite element model, but you're right you would have to use nonlinear algorithm to gradually step the loading increment, check contact surface changes, then check and update deformation and stiffness matrices, then check equilibrium, increment load a bit more, etc. It is not really a trivial problem.

• ###### Re: contact stress

Thanks Anthony.

I actually know the load on top of the flat plate and its not something we can control/reduce. I have license for non linear analysis. can you give me some suggestions on how to proceed ? do you think instead of a line contact, i provide a very small area for contact, the results would be acceptable as a first estimate ? I am not going to have the wheels in the analysis. I just need to figure out a way to provide a fixture that simulates how the plate is supported by the wheels.

Just a question : do you present at the SWW conferences ?? I think I have seen some of the videos on SW website. I liked them and learned some new stuff. If I get to attend the next SWW, Lets meet

Thanks.

Umang

• ###### Re: contact stress

Umang,

Actually, I believe you will have to include the wheels in the analysis. That is the only way to get reasonably accurate results. As Anthony said, learn about Hertz contact stress before you try and run an analysis. I don't find the Wikepedia article very illuminating. The development in my old book, Mechanical Engineering Design by Shigley is much easier for me to understand. Pull out your favorite textbooks and see if one of them will work better for you.

Jerry Steiger

• ###### Re: contact stress

I agree with Jerry. The nonlinearities will certainly be challenging and the numerical modeling for this (in my opinion) crosses-over into graduate student "research" territory (i.e., it can take a lot of fiddling with the numerical controls, rates of loading, mesh density, singularity adjustments, rates of contact convergence and associated area changes, etc.) - but graduate students will do it for free. You can just look-up the answers for this particular problem.

• ###### Re: contact stress

Thanks Jerry and Anthony.

I am going to learn about Hertz stresses and If I make some progress, I'll post here.

Thanks

Umang