Convergence is achieved when the relative unbalance is less than or equal to 1.0. Basically, the Convergence tolerance at any step is computed by multiplying the relative convergence tolerance (1.0e-4) times the current magnitude of the load vector:
Tol = relTol * max( || internalForceVector ||, || externalForceVector || )
The unbalance error is calculated as:
Err = || internalForceVector - externalForceVector ||
Convergence is achieved if Err <= Tol, or:
relErr = Err/Tol <= 1.0
It is relErr that is reported on the screen and in the log file.