This is an estimate of the square root of the error in the total strain energy, which is the difference between the strain energy at the current pass and the exact strain energy, divided by the exact strain energy. To estimate the exact strain energy, the engine extrapolates the total strain energies of three successive passes.

The three successive passes are referred to as pass one, pass two, and pass three, with pass three being the most recent. The index might detect a significant error if the difference between pass three and pass two is not small compared to the difference between pass two and pass one. For multiple load sets, the value is the maximum over all load sets.

Return to Convergence Indicators or Global Energy Index.