Pro/mechanica and plastic like materials 1

[MarkCopland]

Pro/mechanica and plastic like materials.

I have done some FEA analysis in metal parts using promechanica lineal analysis with WF3, with WF4 the hyperplasic model were introduced (so elastomers material like rubber) can be analysed, and now in WF5 elastoplastc material were introduced, both lineal and elastoplastic material works fine in metals.

Now I have seen studies on internet with promechanica where people perform FEA calculation with plastic like materials ( acrylic cast, nylon 6, or PE high viscosity), I am confused because those material are viscoelastic (in other words the are not lineal materials…) so what sort of assumptions they do to effectively modelling a plastic component.

I have never worked with plastic like materials, but I now got this question.

Any body have experience in this type of analysis?.

 

[napoleonm]

Mark.

Have a look at the theread thread828-184976 plastic analysis.

 

[brep]

Napleonm, the thread you linked to is very old At that time (in 2007) hyperelasticity has been introduced in WF4, but not elasto-plastic. Things have certainly moved on since then!

As MarkCopeland pointed out, WF5 introduced the capability to include elastoplastic material properties. There are a few common elastoplastic models provided, along with a nice graphical test data fitting utility to help you choose the "best" model.

However, viscoelastic models are not currently supported. These rate-dependent models are pretty complex and quite frankly the realm of research usage rather than most "designers". (lots of disclaimers here, but you get my drift?)

The fact is, *any* material can be modeled using linear, elastoplastic or whatever model you choose - **as long as you understand and accept whether your modeling/abstraction is appropriate for the situation"**. i.e. you need not use a viscoelastic model if you are comfortable that the loading rate is not a significant contributing factor to the analysis. However, if you are trying to model the stretching/snapping of silly-putty, then perhaps it needs to be there.

In summary of what turned into a long post: FEA is all about managing the abstractions and modeling decisions you make in order to break the problem down into something tractable, timely, believable and ultimately useful.

 

[pio3]

But now another question:

with WF4 (the version I can use at now)I can calulate "Large deformations" for plastic materials (an example also in the PTC web-site) but only for 1 component. So, I cannot use large diplacement for an assembly. Is this correct?

Look at the picture attached:
on the left the results after linear analysis
on the right the results after large displacement analysis