Hi. I am doing non linear FE analysis using a new material beam under flexural 2 point loading using ANSYS. I have defined a bilinear material model. The solution has converged. In results I am getting good stress strain curves (as expected, i.e slope decreasing post yield). However the load displacement curves show an increase in stiffness pattern. Please help me to correct the load displacement curves.
Dear Vaishali,
If you are doing a nonlinear analysis with non linear geometry effect on (nlgeom,on command in ANSYS), stiffness of beam may increase if deformations are large. The inclusion of large deflection means program accounts for changes in stiffness due to changes in shape. Stiffness of curved beams are higher than straight beam. Due to high deflection if straight beam turns in a curved beam its stiffness will increase. This phenomenon may explain the increasing stiffness till yielding. So in my opinion your results are correct if it is happening before yielding.
To understand/explain post yield behavior it will be better if you can share some relevant figures.
Regards
Hello Naveen ji,
Thanks for the response. I am talking about post yield behaviour. the S/S curve reduces its slope post yield but L/D curve stiffness either remains same or increasing a little bit post yield.
It will be better if you share photos of your model and both the curves...
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