Cancel
Showing results for 
Search instead for 
Did you mean: 

Multi step non-linear

Valued Contributor
Valued Contributor

Can you specify multiple load steps in a non-linear analysis?  Specifically, I would like to load and then unload to check permanent deformation.

 

Do I have to do this in advanced non-linear and I get plastic strain?  I did not see where I could specify 2 load cases and also strain.

 

Thanks,

Rich

3 REPLIES

Re: Multi step non-linear

Siemens Phenom Siemens Phenom
Siemens Phenom

Yes, you can create multiple load steps by creating subcases and then specify the desired total load in each case. So, create 2 load cases, one with your maximum load, and a second load case with a very small, effectively zero load. Then in analysis manager create 2 subcase, use maximum load for subcase 1 and "zero" load for subcase 2.

 

You can use regular nonlinear statics or the advanced nonlinear solver. You will need to create a nonlinear material to include plasticity and use one the available options for specifying the stress-strain relationship.

Re: Multi step non-linear

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Rich,

As an add-on to Joe comments you can run the EXAMPLE-25 of FEMAP under HELP > EXAMPLES to understand better the process of creation of the FEMAP model: a simply rod model will be built out of a material which will become nonlinear after the model reaches a defined yield crite­ria (von Mises Stress). The model will be loaded axially beyond the yield stress and then unloaded. These loading conditions will leave the rod plastically deformed. The displacement and strain results will then be viewed with an XY plot.

 

nonlinear-load-unload.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: Multi step non-linear

Valued Contributor
Valued Contributor

Ok, I played with a simple example.  I guess I was confused with "Cases" and had expected to see "load steps" and something that tells Femap/Nastran to proceed from a prior load step to another.

 

It seems to do this automatically...making some assumptions about what is wanted.

 

Any recommendations on how to continue an analysis until it stops converging due to a plastic hinge?

 

Thanks,

Rich