Failure for Optistruct
Altair EmployeeHello,
I want to bend a beam until that beam reach failure. I'm using moment for the load.
I use MAT1 and MATS1 for the material. but it is useless, it never be fail. somebody told me to use MATF. but I don't have any idea how to use it. because there is no guidance to use it.
anybody know something?
Answers
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Matf is usually applied for failure calculation for composites.
What do you mean by failure in your case?
Mats1 should model elasto plastic behavior, amd you should have plasticity and some decrease in stiffness, but in OptiStruct you will not see element deletion.
If you want to see your elements failing and vanishing, you need to go to RADIOSS.
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hello mr. koga
In my case, Failure means that the material wont get any load anymore.
I put the Moment-Rotation picture below.
It said that the beam wont get any higher load (moment in my case) if the beam reach its ultimate load.
its like the maximum load of the material can accept. and in any reference that I read, it's because the material pass through the ultimate stress of stress-strain curve.
but I use elastic-plastic behaviour in MAT1 and MATS1, and the load still increase. and if I put some load again. it wont converged.
and I'm very thankful for your help because you always answer my question
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Hi,
If this is material related only, you can only have elasto plastic behavior, and so the maximum that you will get is perfect plasticity, with near zero slope of the stress strain curve.
The behavior in your curve is only related to material or also includes some nonlinear geometric behavior?
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hello,
do you mean the nonlinear geometric behavior is the percentage of strain more than 5%, then yes it is.
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Have you included PARAM,LGDISP,1 or in your loadstep Nlparm(LGDISP)?
This also turns on large displacements.
For convergence issues, try adding NLADAPT to your loadstep and change a few convergence parameters such as max number of cutbacks, maximum DT, etc..
Also request PARAM, NLMON, DISP so that OptiStruct will write a separate . H3D file showing the displacement for each attempt in load increments. You can load this in HV and try to figure out what is going on. Also in the .out file a more detailed description on convergence is shown.
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