,such a simple and straight forward explanation. Thank you for that.
"The PCG iterative solver might take tens or hundreds ofinternaliterations to solve [K]{u}={F} one time. It is possible that the internal PCG iteration fails to converge." Yes, that is what I was asking actually. How do we know that internal PCG iterations have failed to converge? I mean how to diagnose it? What measures should be taken to solve this problem?
Moreover, you mentioned, "Nodal deformation {u} are the unknowns, applied forces {F} are known. The matrix equation [K]{u}={F} is solved for the unknown nodal deformations." If this is the case, then I think in non-linear analysis, we should be expecting the force/moment/displacement convergence curve (i.e. the magenta curves) to always be equal to zero. Since we are already making use of the external forces to actually calculate the nodal displacements. So there shouldn't exist any difference between the [F] (external force) and [K][U]. What would you say on this?
Plus, I just want to confirm one more thing. So why is the static structural an implicit solver? I mean we are applying the force at a specific iteration of a certain time step, the stiffness matrix is already know at that specific iteration of that certain time step (being assembled from the already calculated nodal displacements from previous iteration) and we just calculate the nodal displacements from here for the next iteration. Simple. Why does it make the analysis implicit?