Learning Forum

[lilly0420]

Hi,

I am currently modeling a drop weight test using LS-prepost

The plate is in a shell element and the impactor is in a rigid body.

To model the drop weight test, I gave a initial velocity to the impactor with LOAD_BODY_Z for gravity.

I compared the result of the reaction force and the displacement of the impactor, here.

 

The initial slope seemed correct, but the maximum force was way lower. Also another problem here was that the impactor doesn't rebound.

 

I changed the impactor from MAT_rigid to MAT_elastic and did the same job, then the rebound does happen.

Though the F-D result was not correct for now. 

 

Maybe, for rigid body, load_body doesn't work? Or contact force or others? 

I wonder what is the difference.

 

[Dennis Chen]

perhaps rephrase your question while being a little more specific.   For example, what do you mean by correct when you say your F-D is not correct, how did you define correctness and what is your result that you believe to be incorrect.   If it is indeed objectively incorrect, what were specifics of your set up and what were some possible reasons that it's incorrect.   Is it really only possible because of the choice of mat card for your impactor?   

There's not a lot of point to use rigid body as impactor as it's unlikely that it will contain elements that will determine your stable time increment.    The target, if it's the focus of your study, would contain elements with way smaller characteristic length.     Do you have correct rate effects captured in the material model for the target?  what about your element formulation for the shell body.   how is the shell body constrained?   What contact card did you use?

I hope what can help you is also to re-read your own question and see how it's missing information that you know, but didn't write down, which is critical to properly define what the problem is.