Learning Forum

[javat33489]

I would like to hear the opinion of experts. How accurate is the calculation in LS-Dyna if only isotrope properties and bilinear kinematic hardening are specified for the material? For example, if the task is to drive a steel tooth into a piece of steel.

It happens that there are no other material data for calculation and you have to make do with what you have.

[Ram Gopisetti]

in other words, you are supplying the elastic and plastic properties to the model which is good,
can you elobrate " It happens that there are no other material data for calculation and you have to make do with what you have."
Cheers, Ram

[javat33489]

I wanted to say that for the calculation I only have the yield strength, tensile strength, Young's modulus, Poisson's ratio, melting temperature and that's it. And to solve the problem of inserting a tooth into a steel plate, I have to use bilinear kinematic hardening in ls dyna, it takes into account only the yield strength. I could solve the problem in a static formulation and use multilinear kinematic hardening there, but the calculation will take a very long time. In addition, for such a task, a very fine mesh of 0.1-0.3 mm is needed. Therefore, I solve the problem in Ls Dyna. My question is that I want to know from you professionals how accurate is the solution using bilinear kinematic hardening in setting such a problem as inserting a tooth into a steel plate and similar problems. You have a lot of experience in calculations, can you say? I made some tests: ls-dyna + bilinear kinematic hardening st structural + multilinear kinematic hardening with the same mesh and loads. ls-dyna showed a margin of safety of 1.01 st structural showed a margin of safety of 0.7 Now I want to figure out which is more accurate. I would like to solve such a problem in LS-Dyna, because there is a fast solver.

[Ram Gopisetti]

"I wanted to say that for the calculation I only have the yield strength, tensile strength, Young's modulus, Poisson's ratio, melting temperature and that's it. And to solve the problem of inserting a tooth into a steel plate, I have to use bilinear kinematic hardening in ls dyna," ---- How is this possible , you might want to account for tangent modulus ?, so this is just elastic.
"I could solve the problem in a static formulation and use multilinear kinematic hardening there, but the calculation will take a very long time. In addition, for such a task, a very fine mesh of 0.1-0.3 mm is needed. Therefore, I solve the problem in Ls Dyna." ---- is ths simulation follows implicit or explicit, are you expecting any element deleation or erosion?
i would consider Johnson-cook or any rate dependecy material model for this simulation.
on general note, does steel can punture steel ?
Cheers, Ram

[javat33489]

I'd like to use Johnson Cook too. But I'm trying to find the parameters for some approximate steel data. And I'm worried about the resulting odds.
Only an experienced person like you can help here.
Please look at my questions.
I made two tables for two materials, see what coefficients are obtained? this is real?
Where can I find out in what intervals these coefficients should correspond?
I don't know if they are true
I decided to do everything not according to the book, but according to this video:
please help me?

[Ram Gopisetti]

i guess you need to calibrate via experiemnt , there is more publised information on steel JC parameters modelded fro lsdyna.
I would recommed you to first start with literature review then start you FEA.
Cheers, Ram

[javat33489]

I tested the materials on a tensile testing machine. Now I'm trying to digitize them. Can you help me make a video?

[javat33489]

Help please

[javat33489]

Maybe someone has a ready-made excel spreadsheet for calculating Johnson-Cook? Or has anyone tried to find Johnson-Cook using the least squares method and finding a solution in Excel?