Learning Forum

[euklidespl]

Hello, 

Is it possible to use the Yoshida Uemori model and the Barlat model while taking into account the influence of the plastic strain rate on the yield stress?

[Armin]

Hello,

When using Barlat models, look for the entry HARD and the available options there. For example, in MAT_133 (*MAT_BARLAT_YLD2000) you can consider the strain rate sensitivity using a 3D table (see the screenshot below).

 

[euklidespl]

Hello, 

Thank you for your answer .Is a table containing the yield stress as a function of strain and strain rate the only way to take into account the strain rate effect? How about coefficient C and P  ? Will this coefficient work with barlat yld ?   

[Armin]

No problem at all.
Yes, for the Barlat model you can input C and P which are the coefficients of Cowper-Symond's equation to scale the reference hardening (stress-strain) curve at different strain rates. It is sometimes easier to directly input the stress-strain curves (from physical experiments, for example), but if you have the C and P coefficients available, you can use the Cowper-Symond's method as well.

[euklidespl]

In the Ls-Dyna manual I read that material number 242 integrates the Yoshida Uemori model with Barlat yld2000 (mat_133). While the mat_133 manual mentions the possibility of taking into account the strain rate, in the manual for mat_242 I found no mention of the strain rate.  I learned from you that it is possible to link the effect of strain rate with the barlatyld2000 model, but should I link the barlatyld2000 model (which takes into account the strain rate) with the yoshida uemori model? I'm asking because in the mat_242 instruction which links the Yoshida uemori  model with barlat_yld2000 there is nothing about the strain rate.

[Armin]

I see your points.
Looking at the MAT_242 incorporating kinematic hardening, it appears to me that the hardening of the material is inherently considered through the Yoshida-Uemori coefficients (unlike the MAT_133 where you could input the hardening curve separately). I would suggest you look at the Yoshida-Uemori equations to investigate if the strain rate sensitivity can be considered from there.