Model Steel for Large Deformation: Multilinear Isotropic Hardening

[RKD89]

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 anyone 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

 

[prabhav30]

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 ?

 

[Studiot]

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.

 

[prabhav30]

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??