Structural contact modeling is a highly nonlinear problem. As surfaces come in and out of contact, load paths and stress states will abruptly change. The computational solvers in the COMSOL Multiphysics® software are designed to work with sufficiently smooth solutions, so solving such models is inherently challenging. To efficiently achieve a converged solution, most contact models will require some changes to the default model settings. Read more [Picture source: COMSOL, Inc. on youtube.com]