In many situations, we tend to change the mesh density to study its effect on simulation responses. Two issues things that are seldom addressed are the contact thickness and the mass-scaling which blend in with the true effects of the mesh refinement. As stated in some of the earlier posts, LS-DYNA computes the contact thickness that is some fraction of the element edge length if SSTHK=0. For any mesh studies involving shells, one must always use SSTHK=1 such that the contact thickness is independent of the element dimensions. The second issue is the use of mass-scaling which can be minimized by choosing a DT that results in identical mass-scaling in all the comparitive runs. This can cause additional difficulties when several parameters such as contact stiffness in SOFT=1,2 are based on global DT which if changed will change stiffness. To avoid this, it is recommended to choose the minimum DT of all mesh variations as global DT for all simulations involving mesh refinements.