How to define different relation in compression and tension for steel material?

- December 3, 2020 at 3:10 pm
  
  Dadojin
  Subscriber
  
  hello,nI want to run certain nonlinear (geometrically and material) analysis of a steel structure.nFor this, I want to use multilinear material model (isotropic hardening)nI have a stress-strain relation defined - in the true stress and logarithmic strain (as there will be large deformations involved)nHowever, because of the necessity to input the stress-strain relation in true-log values, the relation in the tension and compression differs.nhow can I define a different stress-strain relation for compression and for tension with a multilinear material model and Mises plasticity?.thank you,nkind regards,nDanieln
- December 9, 2020 at 2:16 am
  
  Kai
  Ansys Employee
  
  Hi Dan, you can look at cast iron material model. It allows different behaviors in tension and compression directions.n
- January 10, 2021 at 6:46 pm
  
  Dadojin
  Subscriber
  
  hello Kai,nnThank you for the advicennHowever it seems to only allow weaker response in tension. I would need to define otherwise.nnfor example (from ansys example 4.19 cast iron):n/prep7nmp, ex, 1,14.773E6nmp,nuxy, 1,0.2273nn! Define cast iron modelnTB,CAST,1,,,ISOTROPICnTBDATA,1,0.04nnTB,CAST,1,1,5,TENSIONnTBPT,,0.000E-00,0.813E+04nTBPT,, 1.13E-04,0.131E+05nTBPT,, 8.69E-04,0.241E+05nTBPT,, 1.55E-03,0.288E+05nTBPT,, 2.32E-03,0.322E+05nnTB,CAST,1,1,5,COMPRESSIONnTBPT,,0.000E-00,0.300E+05nTBPT,, 1.62E-03,0.500E+05nTBPT,, 4.07E-03,0.581E+05nTBPT,, 6.56E-03,0.656E+05nTBPT,, 9.26E-03,0.700E+05nthat is working, but for example this one is not working (the macro below has been altered the way i have copied the compressive data into the tensile and risen the stress values a bit):n/prep7nmp, ex, 1,14.773E6nmp,nuxy, 1,0.2273nn! Define cast iron modelnTB,CAST,1,,,ISOTROPICnTBDATA,1,0.04nnTB,CAST,1,1,5,TENSIONnTBPT,,0.000E-00,0.350E+05nTBPT,, 1.62E-03,0.550E+05nTBPT,, 4.07E-03,0.620E+05nTBPT,, 6.56E-03,0.732E+05nTBPT,, 9.26E-03,0.785E+05nnTB,CAST,1,1,5,COMPRESSIONnTBPT,,0.000E-00,0.300E+05nTBPT,, 1.62E-03,0.500E+05nTBPT,, 4.07E-03,0.581E+05nTBPT,, 6.56E-03,0.656E+05nTBPT,, 9.26E-03,0.700E+05nIf i conduct a one element test, the response in this second case is just the same, for bot, tension and compression. However higher stresses should be achieved in case of tension.nnthank you,nregards,nDaniel

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