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Failure Mechanism

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SimulatingJules
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(@simulatingjules)
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Joined: 4 weeks ago

Hi all,

To have an apt material model is necessary to get good simulation results. Thus, you perform a tensile test/compression test to fit a suitable material model.

So far, you have got a nice colored picture in your FE solver. But still you need to interpret these results! From tensile tests, you have a critical stress and a critical strain, where plastic deformation or failure occurs. However, in a real setup and its simulation, you don't have pure tensile stress. You have a mix of tensile/compression and shear.

For metal, you can use the von-mises criterion or tresca for the failure criterion, what is very common. For plastics, on the other hand, I don't know such failure criterion.

So, is there a reasonable failure criterion available for plastics (e.g. in PolyUMod)? Implemented in a software or the theory for it somewhere published?

 

Thank you
Jules

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Jorgen
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I like the failure model that is part of the PolyUMod TNV model. See the following page more info: https://polymerfem.com/tnv-model/

/Jorgen

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SimulatingJules
(@simulatingjules)
Joined: 4 weeks ago

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@jorgen thanks for the prompt reply. I had a look in the theory described in the manual for strain and stress based failure predictions of the TNV model. I am just wondering, where do the formulas for the failure strain/stress come from? Did you postulate them?

The Hill Yield criterion is, as far as I know, a model for the beginning of plastic yield. So the failure is plastic deformation. 
But when failure is not plastic deformation but initiating a crack, the Hill criterion is not really good, am I right?

Are there other failure models in polyumod available?

 

Thanks
Jules

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