I was wondering if there is any information out there about exactly when a linear FEA should be run non-linear.  I realize that there isn't a defininative line that separates the two, but are there any recommendations as to when the linear assumptions fall apart? It seems that the large deflection setting detects geometric non-linearity, so I assume that's one sign the problem is no longer linear - but this does not account for a non-linear material.  For example, if the modulus E changes slope by ??%, the linear assumption is no longer reliable, and Solidworks recommends the non-linear package.  It seems like a guideline like this would be helpful to companies trying to understand if they need to upgrade to SW Simulation premium.