/DT/CST_AMS

Engine Keyword This option is a combination of nodal time step (/DT/NODA/CST) and advanced mass scaling (/DT/AMS) with the same target time step.

All elements having an initial elementary time step lower than specified criteria are automatically selected for AMS. Classical constant nodal time step is applied on the rest of the model.

Format

DT/CST_AMS/Iflag

Δ T sca Δ T min Δ T s c a _ a m s MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8akY=xipgYlh9vqqj=hEeei0xXdbb a9frFf0=yqFf0dbba91qpepeI8k8fiI+fsY=rqaqpepae9pg0Firpe pesP0xe9Fve9Fve9qapdbaGaaiGadiWaamaaceGaaqaacaqbaaGcba GaaeiLdiaadsfadaWgaaWcbaGaam4CaiaadogacaWGHbGaai4xaiaa dggacaWGTbGaam4Caaqabaaaaa@426E@

If Iflag =1 or 2, insert the next line

Tol_AMS

If Iflag =2, insert the next line

Niter Nprint

Definitions

Field Description SI Unit Example
Iflag Number of additional (optional) lines.
= 0 or blank
Only one card for Δ T sca and Δ T min is read.
=1
Tol_AMS are read from input.
=2
Tol_AMS, Niter, and Nprint are read from input.
  
Δ T sca Scale factor on critical time step.

Default = 0.9

  
Δ T s c a _ a m s MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8akY=xipgYlh9vqqj=hEeei0xXdbb a9frFf0=yqFf0dbba91qpepeI8k8fiI+fsY=rqaqpepae9pg0Firpe pesP0xe9Fve9Fve9qapdbaGaaiGadiWaamaaceGaaqaacaqbaaGcba GaaeiLdiaadsfadaWgaaWcbaGaam4CaiaadogacaWGHbGaai4xaiaa dggacaWGTbGaam4Caaqabaaaaa@426E@ Scale factor on critical time step for AMS (optional).

Default = 0.67

  
Δ T min Minimum time step. 2  
Tol_AMS Tolerance for AMS convergence.

Default = 10-3

  
Niter Maximum number of iterations in conjugate gradient.

Default = 1000

  
Nprint Frequency (number of cycles) for writing additional output about the number of iterations before convergence in the conjugate gradient.

Default = 0

  

Comments

  1. The Starter keyword /AMS must be defined in the Starter input file.
  2. The AMS is applied on an element when the initial elementary time step is less than:

    Δ T min Δ T s c a MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8akY=xipgYlh9vqqj=hEeei0xXdbb a9frFf0=yqFf0dbba91qpepeI8k8fiI+fsY=rqaqpepae9pg0Firpe pesP0xe9Fve9Fve9qapdbaGaaiGadiWaamaaceGaaqaacaqbaaGcba WaaSaaaeaacqqHuoarcaWGubWaaSbaaSqaaiGac2gacaGGPbGaaiOB aaqabaaakeaacqqHuoarcaWGubWaaSbaaSqaaiaadohacaWGJbGaam yyaaqabaaaaaaa@445E@

    . If the element is not selected, then /DT/NODA/CST is applied.
  3. The automatic element selection is performed in the Starter if the keyword /DT/CST_AMS is detected in the Engine input file. The element selection can be checked in the Starter output file.
  4. The AMS element selection can also be visualized in animation files using the keyword /ANIM/ELEM/AMS.
  5. For the AMS, if Iflag =0, the default values for Tol_AMS, Niter, and Nprint are used.
  6. For the AMS, if Iflag =2, the maximum number of iterations in conjugate gradient Niter, and the frequency for additional output Nprint, must be entered. Otherwise, the maximum number of iterations in conjugate gradient is set to its default value (1000), and no additional output is provided.
  7. For the AMS, if more than Niter iterations have been performed before convergence of the conjugate gradient, the following error message is output and the computation stops:
    “** ERROR: AMS IS LIKELY DIVERGING”
  8. For the AMS, if Nprint is specified, then at each Nprint cycle an additional output is provided including:
    • the number of iterations before convergence of the conjugate gradient at this cycle
    • the final residual norm, and the force vector norm
  9. It is also possible to combine the automatic element selection with manual element selection based on a group of parts. The part group must then be specified in Radioss Starter Input deck (/AMS).
  10. For additional information, refer to /DT/NODA/CST for constant nodal time step, /DT/AMS for the AMS and “Capabilities and Limitations and Limitations (may coexist, but out of the selected AMS part group) in Advanced Mass Scaling (AMS)” in the User Guide.