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Question is on the meaning of input variable TID within material model 163 of LS-Dyna 971.

Definition of TID variable.

TID: Table ID defining yield stress versus volumetric strain at different strain rates.

Remark of TID: Rate effects are accounted for by defining a table of curves using *DEFINE_TABLE. Each curve defines the yield stress versus volumetric strain for a different strain rate. The yield stress is obtained by interpolating between the two curves that bound the strain rate.

What I understand of the yield stress is a single point on a stress vs volumetric strain curve for each individual strain rate. So wouldn't that give me a yield stress vs volumetric strain point for each individual strain rate.

Is the yield stress referring to just the stress. Having trouble understanding the inputs, any clarification would be helpful.

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  • $\begingroup$ Welcome to Engineering Stack Exchange! This is going to need a lot more clarification. I note you have two questions, one a theoretical clarification request (Does the TID really mean different yield points for different strain rates), the second a question regarding specific inputs for the LS Dyna machine. $\endgroup$
    – Mark
    Aug 27 '18 at 16:22
  • $\begingroup$ While many people can probably answer the first (yes you do get different points for different strain rates), the second would be a bit more difficult and probably best answered by tech support for the specific machine. I am voting to close this as "unclear" for now, but please review and see if you can figure out if you want this in a theoretical framework or a machine-specific framework, and rewrite the question, preferably with a full list and source for the definition. Two separate questions in both frameworks is also acceptable. $\endgroup$
    – Mark
    Aug 27 '18 at 16:22
  • $\begingroup$ "the yield stress is a single point on a stress vs volumetric strain curve". That's not correct. Please read an introductory text on plasticity. $\endgroup$ Aug 28 '18 at 4:45
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While the yield stress is a well defined point in materials such as steel or other metals, that is not the case when we talk about foams. Here they are calling "yield stress" to the whole volumetric strain-stress curve. So they are basically asking for a number of strain-stress curves at different strain rates.

Or you can use material 63 if strain rate effects are not important.

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