4 Replies Latest reply on May 11, 2015 3:32 PM by Jared Conway

    Hardening Factor and Maximum incremental strain

    Jessie Brambell

      Hello everybody,

       

      I have two quick questions regarding some material data and property settings in non-linear dynamic studies.

       

      1) What is hardening factor?

       

      I've looked around and can't seem to find out what it is or what it does! I found a thread which pointed out it may be related to work hardening, but I'd really like more of a detailed answer of what is is and what its purpose is in nonlinear dynamic simulations.

       

      2) From what I understand, maximum incremental strain is the maximum strain that may occur between time steps during a nonlinear solve, otherwise the time step is reduced and the iteration is repeated to hopefully get a lower strain between steps. Now, this may seem like a dumb question, but is the maximum incremental strain based off engineering strain? i.e (L - Lo)/Lo where L is the stretched length, and Lo is the initial length? Or is it based off logarithmic strain? (Which I don't understand entirely). If anything I'd just like some clarification on how maximum incremental strain works in the nonlinear dynamic simulations. Also, I'd love to know whether increasing its value would be considered a bad idea or not. (i.e leads to poor results).

       

      Thank you for your time!

        • Re: Hardening Factor and Maximum incremental strain
          Shaun Densberger

          1) What is hardening factor?

           

          The Hardening Factor defines the ratio of kinematic to isotropic hardening, where pure isotropic hardening will have a Hardening Factor of 0 while pure kinematic hardening will have a factor of 1. In isotropic hardening the yield surface maintains the same shape and increases in size as the plastic strains increase. In kinematic hardening the yield surfaces maintains the same shape and size and translates around in stress space. Typically, metallic undergo isotropic hardening while plastics and hyperelastic materials undergo kinematic hardening. However, real metals exhibit both isotropic and kinematic hardening, hence the ratio factor.

           

          2) From what I understand, maximum incremental strain is the maximum strain that may occur between time steps during a nonlinear solve, otherwise the time step is reduced and the iteration is repeated to hopefully get a lower strain between steps. Now, this may seem like a dumb question, but is the maximum incremental strain based off engineering strain? i.e (L - Lo)/Lo where L is the stretched length, and Lo is the initial length? Or is it based off logarithmic strain? (Which I don't understand entirely).

           

          What strain formulation is used depends on how large the strains are; engineering strain applies to small strains whereas logarithmic strain applies to large strains. I'm not sure whether SW allows the user to control whether engineering or true strain is used, but the safe assumption is to use logarithmic strain (sometimes called true strain).

           

          If anything I'd just like some clarification on how maximum incremental strain works in the nonlinear dynamic simulations.

           

          What exactly do you want to know?

           

          Also, I'd love to know whether increasing its value would be considered a bad idea or not. (i.e leads to poor results).

           

          The maximum incremental strain is not something that you typically play around with, as excessively large incremental strains can lead to inaccurate results and/or numerical convergence issues.

          • Re: Hardening Factor and Maximum incremental strain
            Jared Conway

            hardening > 2015 SOLIDWORKS Help - Plasticity Tresca Model described here. takes into account isotropic and kinematic hardening if that needs to be accounted for in your analysis. i've been supporting simulation users for 10 years, i've seen 1 person use it and hardening evaluation was the specific goal of his analysis and had very good data to build a good model to use it.

             

            incremental strain > as shaun said, it is a solver parameter best left untouched unless you really need it. generally a last ditch effort to help a solution solve but most of the time when needed it is because there is something else wrong with the setup of the analysis. again, 10 years supporting users, have never seen the developers recommend this unless it was the last option.

            • Re: Hardening Factor and Maximum incremental strain
              Zhang Yu

              hill jared conway:

              I meet the same question too,could tall us how to get the data of RK ,or where can we consult to the data of RK