Quasi-static Response of Explicit Analysis – Lesson 2

How to judge if the response of an explicit analysis can be considered as quasi-static in Ansys LS-DYNA® nonlinear dynamics structural simulation software?

To judge if the response of an explicit analysis can be considered as quasi-static, one can do the following:
1) Plot the time history of critical response quantities, such as nodal velocities or element stresses, and see if there is any significant vibration.
2) Check the energy balance plots through glstat, for the whole model, and matsum, per part (maybe more important), and make sure that the kinetic energy is very small compared to the internal energy. This would mean that most of the external work is converted to internal energy. If the kinetic-to-internal energy ratio is something like 1%, it could be assumed that the dynamic effects have no impact on the results.
3) Run an analysis with a more gradual (slower) loading ramp and see how much the results are affected. If the results are not affected much then the faster loading rate can be used in further analyses.
4) Another way is to compute the dominant vibration mode that the applied loading will excite and make sure that the loading ramp duration is at least 3 to 5 times the natural period of that mode.