Steel as an Elastic/Perfectly Plastic Material

Can anyone tell me the best way to model steel so that it behaves elastically to its yield point, then plastically beyond? I think it's possible using the Calculix solver and one of the nonlinear material types, but I can't figure out how they work exactly.


  • You can use these settings:

    Analysis type: Nonlinear Static 3D
    Solver: CCX
    Material: Mechanical type = Isotropic, plastic type = bilinear

    Here's an example with a force that increases with time that causes elastic deformation initially, then plastic deformation towards the end.

  • Thanks for the help so quickly, Victor! I'll give it a try when I get back to the office tomorrow.
  • Got it. Works great, Victor!

    Does anybody know where to find material info online to get the properties necessary for inputs, like tangent modulus?
  • Hi!
    Make attention because the first point under *PLASTIC card is the yield point and so the strain must be the true plastic strain.
    About material info on plastic field you can find several models. I use the models on attached pictures for European structural steels on CCX.
    For the Standards that I know (European Standards) plastic analysis refers to elastic-perfect pastic material model or bilinear model with strain hardening. For example EN 13445 (pressure vessels) admits plastic analysis for pressure components using bilinear material models (EN13445 Part 3 - Annex B).
    Make attention to yielding criterion and to flow rules on plastic analysis

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  • Thanks for the tip Andrea!
  • edited November 4
    IN718 bolt bending in the thread. Elastic case and plastic case, 75F. True stress strain curve.

    Bending bolts is not good.
    IN718 bolt 75F true stress strain.jpg
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