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From linear to nonlinear analysis

After performing a linear static analysis of an assembly with SOL 101, having found that in some cases stresses are higher than yield strength, I would like to perform a new analysis using the material nonlinearity (elastic-plastic behaviour), to measure the permanent strain.
The solver SOL 106 does not allow me to use the surface-to-surface contacts defined in the sim file (with friction and also offset on regions). Only surface-to-surface gluing can be copied, which I have defined too.

Is there a quick way to convert the linear model to a nonlinear analysis?

In the Basic Nonlinear Analysis User's Guide it is written:
"In NX Nastran, you can perform nonlinear static analysis using SOLs 106, or 153. Modeling options are compatible with linear analysis. For example, you can convert a SOL 101 model to a SOL 106 analysis by adding a few bulk data entries relevant to the nonlinear analysis to your input file.

These nonlinear properties and/or effects are defined by nonlinear material data (e.g., MATS1, MATHP, CREEP, and TABLES1), gap elements (GAP), slideline contact (BCONP, BLSEG and BFRIC) for nonlinear interface, and PARAMeter LGDISP for geometric nonlinearity."

Thanks in advance to whom can help me.

Giuseppe Catalano

Re: From linear to nonlinear analysis

Caro Giussepe,
To perform contact nonlinear analysis you will need a valid license for Advanced Nonlinear Module (SOL601/701). The following animation is a nonlinear analysis with surface-to-surface contact solved using SOL601 (see tutorial at

In fact, is very easy to convert a linear static model SOL101 to nonlinear static SOL106, but you need to be aware of the surface-to-surface contact limitations. For contact in SOL106 you need to use CGAP node-to-node contact elements. This element type can be used in both SOL101 & SOL106 analysis, then the model is ready to be solved easily by both solvers with little changes. En the following tutorial you have explained all the phases to define step-by-step a nonlinear analysis using NX NASTRAN BASIC NONLINEAR MODULE (SOL106) and compare results with SOL101:

Best regards,

Re: From linear to nonlinear analysis

Dear Blas,
unfortunately I have not the license for SOL601/701 but only for SOL106.
I am trying to add the CGAP elements to fem and do other adjustments to re-start analysis.
Thank you for your answer.