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ANSYS-Steel beyond yield point -Engineering strain or true strain for Plastic strain

  1. Dec 2, 2012 #1
    I am trying to do a problem on Material Non-linearity , to model steel for large deformation , beyond yield point ,
    I have tensile testing data for the steel ( in form of Engineering stress vs Engineering strain).

    for defining the model , I chose Multilinear Isotropic hardening
    now there are 2 options
    stress vs total strain & stress vs Plastic strain

    Which option should I choose ( I was asked to choose Stress vs Plastic strain )
    Also , what values should I use ? Engineering stress , Engineering Plastic strain (engineering strain - engineering stress/youngs modulus ) ;
    or True stress and true strain values ( I know how to calculate them )

    can any one clarify?

    Also , to make it clear , I am trying to simulate a 4 point bending test , I know how to do contact analysis etc , I am only confused about the material modelling part
     
  2. jcsd
  3. Dec 26, 2012 #2
    Re: ANSYS-Steel beyond yield point -Engineering strain or true strain for Plastic str

    Sir, since you are concerned with the field of material science, may I ask a question in that regards??

    I wanted to know why are there two yield points in a stress strain curve ?
     
  4. Dec 26, 2012 #3
    Re: ANSYS-Steel beyond yield point -Engineering strain or true strain for Plastic str

    The difference between engineering strain and true strain only becomes significant when phenomena such as tensile necking occur.

    In normal engineering structures plastic analyis is conducted as a transition from linear-elastic to full plastic and the resulting stress block deduced, often as the formation of a plastic hinge. In this type of analysis the strain remains small and limited by elastic engineering considerations.
     
  5. Dec 26, 2012 #4
    Re: ANSYS-Steel beyond yield point -Engineering strain or true strain for Plastic str

    thnksss.....but i was asking about the upper and lower yield points....the case of true engineeriing stress-strain curve and normal stress-strain curve arises only after the ultimate failure stage...
    can you tell something regarding the reason as to why there are two yield points, upper and lower??
     
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