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restart

Valued Contributor
Valued Contributor

Can anyone point me to how to do a restart?

 

I ran a SOL 601 that stopped halfway through and I would like to try and continue from that point using a SOL 701 explicit analysis.

 

Thanks, Rich

4 REPLIES

Re: restart

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear AllTrans,

Restart is a useful feature in Advanced Nonlinear Solution (SOL601). It can be used when the user wishes to continue an analysis beyond its previous end point, or change the analysis type, loads or boundary conditions or tolerances. A restart analysis is selected by setting MODEX = 1 in the NXSTRAT entry. Recovering results from a restart file without continuing the analysis can also be done setting MODEX = 2.

 

According the NX NASTRAN QRG the parameter MODEX of NXSTRAT card indicates the mode of execution:

0 – Normal analysis run, i.e. not a restart analysis

1 – Restart analysis

2 – Recover results from restart (.res) file without running analysis for any additional time steps. GPFORCE and SPCFORCES cannot be recovered. MODEX=2 is supported only for SOL 601 analysis.

The restart (.res) file from a previous run must exist to do a restart analysis or result recovery. The filename and location of the restart file is determined by the “dbs” keyword. By default, dbs points to the current working directory with the prefix of the current job name. The IDs of grids, elements, properties, materials, contact sets, contact pairs and contact regions should be the same in both the original and the restart model. Note that keyword scratch=no must be used when running a restart analysis or result recovery.

 

nxstrat-restart.png

 

According the NX Advanced Nonlinear Manual the geometry, and most element data, cannot be changed in a restart analysis. However, the following changes are allowed:

 

  • Type of analysis can change. Static to dynamic and dynamic to static restarts are allowed.
  • Solution type can be changed. Solution 601 (static or dynamic) to Solution 701 restarts are allowed and viceversa. In this case, features not available in either solution type cannot be used.
  • Solution control variables can change. The flags, constants and tolerances for the iteration method, convergence, time integrations, automatic time stepping and loaddisplacement-
    control can be changed.
  • Externally applied loads and enforced displacements can be changed.
  • The material constants can be changed. However, note that in a restart run the same material model (with the same number of stress-strain points and the same number of temperature points, if applicable) must be used for each element as in the preceding run.
  • Boundary conditions can be changed.
  • Constraint equations and rigid elements can be changed.
  • Contact settings can be changed. This includes most contact set, contact pair and contact surface parameters.
  • Rayleigh damping coefficients can be changed.
  • Time increment and number of solution steps can be modified.
  • Time functions describing the load variations can be changed.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: restart

Valued Contributor
Valued Contributor

Thanks Blas.   A few more dumb questions:

 

1.  Do I modify the current analysis or create a new one?  Sorry, restarts are a new one for me.

 

2. Are there any simple examples or tutorials out there?

 

Thanks,

Rich

Re: restart

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Rich,

You can modify the current analysis or create a new one. The key is to use MODEX=1 and preserve the file with extension *.res to run the restart analysis, just created after the analysis was completed. If you create a new one you must copy the *.res file as well.

 

Here you are a workflow playing with the TSTEP card modified to achieve intended time steps:

 

nxstrat-restart-example.png

 

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: restart

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Rich,

Also remember: when changing from SOL 601 to SOL 701, all features used must be
supported by SOL 701, e.g., cannot have higher-order elements.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/