Algor's Bob Williams says any of the following methods will determine when results have converged satisfactorily and accurately:

Display precision contours. This is a color-coded graphical display of changes in results from one element to the next. This contour determines the mesh's effect on accuracy and supplies guidance for locations needing a finer mesh. A fine mesh on high-stress locations, rather than the whole model, trims analysis time.

Display unsmoothed result contours to see stepped changes between results for adjacent elements.

Display the model's residual forces and check reactions at supports to make sure they balance or at least meet expectations based on engineering judgment.

Inspect result values at the same location (the center for example) after each iteration.