How to define multilinear stress-strain curve in ansys APDL

- May 10, 2020 at 11:44 pm
  
  indra1994
  Subscriber
  
  Hi,
  
  I am trying to define a multilinear stress-strain curve for each SOLID185 element in my ANSYS model. The stress-strain relationship is shown below. So far I have no idea how to define this multilinear relationship in ANSYS APDL 2019 R2. I tried to model it as Multilinear Isotropic Hardening but ANSYS throws error as the tangent slope can not be less than zero.
  
  Can Anyone please help me with this?
- May 15, 2020 at 8:23 pm
  
  John Doyle
  Ansys Employee
  
  KINH and MISO plasticity models do not support negative slopes as you have reported.
  
  Make sure that your data input represents true-stress vs true strain. The slope might be positive after all.
  
  If that is not the issue, there is another option. TB,NLISO,, will support a negative slope beyond yielding.
  
  Keep in mind, the negative slope implies instability. Static analysis under a force based load will likely not converge if all the elements in the primary load path go totally plastic.
  
  Hope this helps.
- May 15, 2020 at 8:25 pm
  
  indra1994
  Subscriber
  
  Thanks for your reply, It really helps.