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The stress-strain data for a plastic deformation is given in table. 

 I have two questions related to how that table is treated:

  • How is data interpolated? Is it piecewise linear or something else?
  • What if the plastic strain is larger than the maximum plastic strain provided in the table? I presume the data is extrapolated? But how? Using the linear interpolation between the last two points or something smarter?

Thank you

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  • $\begingroup$ There are a large number of possible ways, and the only way to be sure is to look at the official documentation. A good working assumption is linear interpolation, and linear extrapolation using the last two data points. $\endgroup$ Nov 30, 2021 at 18:18

2 Answers 2

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  1. I think the table lists the "true stress vs strain curve" data for a specimen going through cyclic loading (to yield) - unloading tests. In such an application, the yield point tends to move higher with the corresponding grows larger as well.

Example:

enter image description here

http://web.mit.edu/cortiz/www/Jerry/TPU_final.pdf

2)There is nothing to do with linear elastic behavior, thus I don't think you can extrapolate using such a relationship.

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If the table is input for your analysis, you can base settings of a plasticity model based it. Depending on the stress-plastic strain relation in the model, you may need to do different things:

  • generally curve fitting to find parameters required by the model
  • except for multilinear hardening model, where the table is the input as it is

Regarding the behaviour of the model after last point in the table:

  • general model: it will behave according to parameters of the model
  • multilinear hardening model: extrapolation of using the last 2 points is used (you can add a point with higher strain and the same stress compared to the last point to switch of the hardening after the last point in the original table)
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