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# Beam Non linear stress distribution

Pioneer

Hi,

I'll performed a non linear analysis with beam model. I would obtain in advanced post a non linear stress distribution of stress (using equivalent stress plot).

How can I obtain it?

Best regards

Stefano

11 REPLIES

# Re: Beam Non linear stress distribution

Valued Contributor

With the advent of the solver NXN 9.0 (Femap 11.1.0) nonlinear materials for the beam elements are not supported

# Re: Beam Non linear stress distribution

Pioneer
I use autodesk nastran. I performed non linear analysis and using
equivalent plot stress I obtain a coherent result. But I'll evaluate the
non linear stress in cross section.

S.Milani

# Re: Beam Non linear stress distribution

Genius

I don't beleive this is true, because I recently had a convergence issue involving nonlinear material on a beam element in v11.3.0. And nonlinear output for the beam element is still available.

To answer OP's question, I don't think FEMAP supports an advanced display of nonlinear beam stresses on a 3D view of the beam element. Strand7 does this well: http://www.strand7.com/webnotes/search/?q=nonlinear+beam&all=

# Re: Beam Non linear stress distribution

Valued Contributor

# Re: Beam Non linear stress distribution

Genius

Hah, welp, I was using elastic-perfectly-plastic.

# Re: Beam Non linear stress distribution

Valued Contributor

Kava

Please indicate your settings for the calculation of non-linear material beam elements.

# Re: Beam Non linear stress distribution

Genius

Ah, I had no problem with it, I was just chiming in to try to help. I defined a plastic cutoff of 355 MPa in the Nonlinear tab of my material, which was applied to both plates and beams.

I ended up taking more nonlinear steps and that cured the problem. The strain increment was too large.

# Re: Beam Non linear stress distribution

Valued Contributor

Which of these materials allows to obtain a non-linear material for the analysis of beams?

# Re: Beam Non linear stress distribution

Genius

It was the middle one. I got nonlinear beam output, but the nonlinear beam plastic strain was always zero. I assumed it was because it did not yield. However, 3930..Nonlinear Beam EndB Pt4 Eqv Stress was just at the yield point (355 MPa), indicating yielding.

My mistake. It was at 35.5 MPa. Although I did get a divergence error on a nonlinear beam at one point, I corrected the model in the meantime to have higher yield strength and finer timesteps and that solved the problem. So I'm not sure what the whole story was honestly, but it's solved.