quasi-static analysis

[amar]

Hello,
Thank you very much for your help regarding my previous post. Continuing on with the riveting analysis with Explicit. I want to do a quasi-static analysis. I am applying a 0.13 inches displacament to the rivet. I have gone through the manual on quasi-static analysis. I just had a couple of questions on that. I am not sure of the typical riveting speeds in practice. I searched on that but did not find anything useful. Right now, I am running the analysis for different time periods, 0.001 sec, 0.01 sec, 0.1 sec. As per the manual for longer times inertia effects should be negligible and the results should converge. What results exactly should one look at for comparison? The results that you are interested in? Since my analysis has all deformable bodies (aluminum + rubber) is comparing the kinetic energy and internatl energy ratio for the whole model appropriate? If at increasing time periods your results dont converge how do you determine if it is quasi-static? The manual says runing your analysis at the natural time scale of the process should ensure a quasi static analysis. I am not clear what exactly is the natural time scale (is it the actual total time required for the process?) In one analysis abaqus has introduced material damping to "smooth" the KE plot. Is this neceessary and if so for all the bodies?
thanks a lot
amar

[Jorgen]

Explicit simulation are good because you can often get an answer. The problem is that you don't always know if the answer is the correct answer. To perform quasi-static analysis it is typically required to scale the density of the different materials. The problem is that it is not always easy to a priori figure out how much you can scale the density before the inertial terms start to dominate. One approach is exactly what you described: try different mass scaling until you are confident that the results that you get are OK. To compare two solutions you can basically use any output measure that you like. It should not matter. I often use stress and/or strain. The actual time scale that the manual refers to is the time scale associated with no mass scaling. That way you know that you capture the right amount of inertial forces.