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

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RKD89
#1
Dec2-12, 05:50 PM
P: 45
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
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prabhav30
#2
Dec26-12, 06:45 AM
P: 2
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
#3
Dec26-12, 07:16 AM
P: 5,462
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
#4
Dec26-12, 08:26 AM
P: 2
ANSYS-Steel beyond yield point -Engineering strain or true strain for Plastic strain

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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