General Mechanical

General Mechanical

Linear Unrealistic Stress Strain graph

    • Faryal
      Subscriber

      PLA stress strain graph generated by ANSYSPLA stress/strain graphI have applied moment on a structure and as a result i am getting stress and strain readings. I obtained values for applying different moments using parametrization. I plotted the graph between the stress and strain as depicted in the image. The material used is PLA and it showed deviate from its linearity at 35 MPa. How to get a graph that is near to reality? What mistake i would be doing? Please Help

    • Wenlong
      Ansys Employee

      Hi,


      Do you have large deflection turned on? 


      Regards,


      Wenlong


       

    • peteroznewman
      Subscriber

      Do you have Plasticity in your Material Model?

    • Faryal
      Subscriber

      I did not included analysis of plastic behaviour. But the model shows perfectly elastic behaviour.

    • Faryal
      Subscriber

      I only included elastic modulus, tensile yield strength and tensile ultimate strength.

    • Faryal
      Subscriber

      Material Data

    • peteroznewman
      Subscriber

      The simplest plasticity model is Bilinear Isotropic Hardening.  There are only two inputs: Yield Strength and Tangent Modulus. Make sure you have the units set correctly when you enter the Yield Strength value.  Use 0 for the Tangent Modulus. This defines an Elastic-Perfectly Plastic material which is a good choice to deliver conservative results.

    • Faryal
      Subscriber

      I need another suggestion from you. How to get properties of 3D printed materials. As flexural modulus is always listed in the properties of PLA. 


      Can i get an ANSYS library of engineering Data for my work online?

    • Faryal
      Subscriber

      can i use tensile yield strength as yield strength in bilinear isotropic hardening?

    • peteroznewman
      Subscriber

      can i use tensile yield strength as yield strength in bilinear isotropic hardening?



      Yes.

    • Faryal
      Subscriber

      The simulation process is taking too much time and iterating the process of preparing models, building model and solving model after i have added the plastic model property.

    • Wenlong
      Ansys Employee

      Hi,


      I noticed in the screenshot you shared that you have "large deflection" turned off. I strongly recommend you turn it on for materials with plasticity to obtain more accurate results. 


      If you click on "Analysis Settings", it is under "solver controls".


      Regards,


      Wenlong


       

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