General Mechanical

General Mechanical

negative load-displacement curve

    • jjaafar68
      Subscriber

      Dear all, 


       


      I'm using Ansys Apdl v16 to model simple concrete beam under static load by using Solid65 element.

      after plot load-displacement curve , the curve stopped at the maximum load, unlike experimental there are no negative slope in the curve. 

      my question is, 

      is there any way to plot full load-displacement curve with the negative slope ? like the graph. 


       

    • mekafime
      Subscriber

      Hi,


      I usually change the sign in excel

    • Sandeep Medikonda
      Ansys Employee

      Hi, Isn't that post-buckling behavior?


      Did your model run to completion? I suspect it hasn't?


      Buckling is a numerical stability and your tangent stiffness matrix is going to zero.


      You can overcome buckling by adding some stabilization energy to your model.



      Regards,


      Sandeep


      Best Practices to post on the Student Community

    • peteroznewman
      Subscriber

      What was the load in your model: a force or a displacement?   A force load cannot solve past the maximum force, that is why it is required to have a displacement load on your structure and extract the reaction force. A displacement load can track a reaction force reaching a maximum and then plot the negative slope.


      Regards,


      Peter

    • OguzhanA
      Subscriber
      But if we have to apply environmental pressure (like external pressure) to a cylinder, we can't add displacement there, right?n
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