General Mechanical

General Mechanical

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Material plasticity models and breaking point

    • Miguel
      Subscriber

      Hi,

      Why is it that the stress-strain line does not end/cut in the X point (tensile ultimate strength = 60MPa) in the graph for a material modeled like this?:

      And, correspondingly, why this ultimate strength (->breaking) is not somehow captured/shown in any result object (e.g. of a static analysis)?

      Is it feasible perhaps to use any user-defined result or any other way for this purpose?

    • peteroznewman
      Subscriber

      The material model does not include a failure point. 

      In the case of a ductile material, a failure criterion is when the Total Strain > Elongation, a material property. In your case, you could plot the Total Strain and set the maximum value on the legend to be 0.015 and color code in red any material that has failed.

      In the case of a brittle material, a failure criterion is when the Max Principal Stress > Ultimate Tensile Strength.  Ansys uses the Ultimate Tensile Strength in a Safety Factor plot in Mechanical.

      • Miguel
        Subscriber

         

        Thanks again Peter.

        In that case, shouldn´t ANSYS include this property (elongation) in the Engineering Data Toolbox "Strength" group? (as it does with ultimate strengths) 

        Also, are those criteria valid for cyclic loading with cumulative plastic strains/deformations too?

         

    • peteroznewman
      Subscriber

      I don't use the Safety Factor plots that require Engineering Data to have those strength values so I wouldn't use Elongation either.

      Yes, cyclic loading will accumulate plastic strain which is included in Total Strain.

      • Miguel
        Subscriber

        Fair enough. Then, what do you use instead?

        By the way, did you see the other (yet unanswered) questions I posted?

    • peteroznewman
      Subscriber

      For metal plasticity, plot the Total Strain and set the maximum value on the legend to be Elongation and color code in red any material that is above that value.

      Yes, I saw your other questions.

    • Miguel
      Subscriber

       

      Thank you Peter. In my model some parts are line bodies so I got this message about them:

      I plotted Beam-tool results (direct, bending and combined stresses) and I see they are above yield strengths for the used materials. Now I wonder whether there is a quick and easy way to get strains from them. Any suggestion?

       

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