Generally, there are three types of nonlinearity, i.e. material nonlinearity, deformation nonlinearity and constraint nonlinearity. If we do a frequency analysis, we don't see influences of material nonlinearity and deformation nonlinearity on the analysis results. Compared to some other FEA tools, ABAQUS has a unique feature of considering constraint nonlinearity, e.g. contacts, in the frequency analysis. I do see the difference when I include contact constraint in my ABAQUS model, comparing with linear model with beams and rigid bar connections. Does somebody also have experience on this topic? Please share your opinion. Thanks!

SIMULIA Champion ​​​​​​​