I am trying to restart a dynamic structural simulation in CalculiX, but the results upon restart do not agree with a non-restart run. For example, running for 20 steps as the “correct” solution, then running for 10 steps, and restarting to run for 10 more. I have tried combinations of (*DYNAMIC,DIRECT), (*DYNAMIC,DIRECT,EXPLICIT), NLGEOM, constant *CLOAD, and variable *CLOAD amplitude. I get the same results across multiple CCX versions (CCX_2.10, CCX_2.11, and CCX_2.16).
The restart itself does not fail, but it does produce a result inconsistent with the non-restart “correct” solution (i.e. y-displacement of node 2302 at t=0.02 should be 9.644763E-02 but if restarted at t=0.01 and run to 0.02 gives 9.644786E-02).
Has anyone else come across this problem before?