SimScale CAE Forum

FEA convergence based on given tolerance

Most often when you do nonlinear finite element analysis on SimScale, you see the convergence plot something like this:

This is the convergence plot of residuals. The red and green is relative and absolute respectively. Residual in convergence plot represents if either the solution has converged or not. In solid mechanics, the solution is considered converged if the reaction forces in the system matches the user applied forces under the user specified tolerance. This tolerance is what you normally give under Numerics for either absolute or relative convergence criteria as shown in figure below.

For example in above case, the relative error tolerance is set to 1e-6, then in one of the iteration if the relative error is reached until for example 1e-5 and the maximum iterations has been reached (i.e. 20 as in above case), then the solution will diverge and the timestep will cut down if Auto timestepping scheme was selected. On the other hand, 6.40 e-8 (highlighted in convergence plot figure above) will lead to converged solution.