Only Keyword: only /DT/AMS must be present in order to invoke AMS with the targeted increased elementary time step (Radioss Engine Input).
/AMS is mandatory in the Radioss Starter Input in order to designate the selected parts or the entire model on which AMS is applied.

In /DT/AMS/Iflag if Iflag= 1, the tolerance for AMS convergence, Tol_AMS, must be provided. If Iflag is ignored, the default value (1E-3) for Tol_AMS is applied. It is not recommended to modify AMS tolerance, if it is not needed. Note that Tol_AMS was 1E-4 in 12.0.210.

In /DT/AMS/Iflag, if Iflag = 2, the display of the number of AMS iterations may help in debugging or monitoring convergence at no extra CPU cost. Maximum allowed iterations before sending a divergence message is 1000 by default. It is advised to NOT change this value. Anything above this maximum value, Radioss stops with the following error message:
  • Monitoring the number of iterations per cycle can help to understand the resulting AMS performance:
  • 75 to 100 iterations is a sign of a really bad convergence 50 iterations may not provide any speedup 30 iterations or less is considered a good convergence.

It is advised to use 0.67 as the scale factor, Δ T sca , rather than 0.9 (as well as in traditional nodal mass scaling /DT/NODA/CST, especially if it is used for comparison with the AMS results).

Target a minimum time step, Δ T min , from 10 to 20 times than the one used in /DT/NODA/CST, that is, start with 10 times, then check how far to go by verifying the numerical convergence, the gain of elapsed time, and the results quality.

/DT/AMS will not modify the global mass, therefore:
  • The global momentum of the related nodes is conserved.
  • A comparison with traditional mass scaling requires a minor added mass along the /DT/NODA/CST computation, if used as a reference.

/DT/Eltyp/Keyword3 is compatible with /DT/AMS, except /DT/INTER/CST (refer to Capabilities and Limitations for further details).

Use /DT/INTER/DEL as a workaround for slow convergence, or possible divergence, when invoking a nonlinear penalty stiffness with contact interfaces TYPE7, TYPE11, and TYPE19.

/ANIM/NODA/NDMAS may be added in order to output non-diagonal mass variation.

/ANIM/NODA/DINER may be added in order to output added inertia per nodes.