Simulating large plastic deformation + defining material 1

[Rezette]

Hi, I am a Cosmos DesignSTAR user and I am trying to find out what the best way would be to define plastic material
behaviour.

I have to simulate loading of a part until breach. The construction is totally manufactured with alloy steel.
The material has a strain (after breaking) from 22%.

Will it be satisfying to use bilinear material for this
kind of analysis or do I have to use a more sophisticated
approach?

Does anybody have some suggestions for me?

Greetings,



Gilbert

 

[feadude]

You can use bilinear if you are simulating the material to UTS but not break point. This requires reduction in strain to UTS point, usually about 6% for A514 alloy steel ( not sure about your alloy steel?). If you are using Ziegler-Prager kinematic hardening, bilinear is the only choice you have anyway.
UTS+

YIELD+




(0,0)+

 

[Rezette]

Thanks FeaDude,

We just tested the parts today, but we didn't even measure
elongation. We reached the breaking point way long before
our FEA model has. The point at which we predicted yield
was also the breaking point. One thing we didn't put in
the model was the behaviour of the welding material.

I think I have to look at special theory for crack
initiation and propagation of welded connections.

Thanks,



Gilbert

 

[feadude]

something is not right because if yield and breaking point are the same this means material is brittle but u have indicated it is alloy steel (ductile material). Maybe ur welds are the high stress points. Welded joints should be designed to where the base metal is the failure point not the weld. This can be done by relocating the welded joints to lower stress areas ie internals of structure, etc