When refining the elements to double size, why won the computation converge?
Convergence of these nonlinear models depends on numerous factors that require some experience in nonlinear mechanics to understand. Even the term convergence has several different meanings. You are talking about the numerical convergence of the Newton schemes. The main determinants of whether the Newton iterations will converge in this particular problem are: (1) the compressibility modulus for the slightly compressible models (augmented lagrangian) problems. As this is made higher, the stresses will be more converged and strains closer to incompressible, but the stresses being higher will require smaller loads steps and more Newton iterations to converge without stresses overflowing and causing NaNs. Hence you may lower the modulus at least to get an initial estimate solution; (2) the step size: as the problem gets more degrees of freedom you often need to take smaller steps to get solustion without numerical instabilities; (3) the error tolerance for stopping the Newton scheme: Beca
