problem for plotting stress strain curve

[henasr]

Dear all,
I am new with Abaqus. I am trying to plot stress-strain curve of a metal with Abaqus.
I gave Young's modulus, Poisson ratio and yield stress corresponding plastic strain.
After analysis the result didn't seem what i provided. Such as i provided maximum yield stress of 65 corresponding plastic strain of 0.155 but it showed maximum yield stress of 75 corresponding plastic strain 0.14
Any one can suggest me what is the problem?
My .cae file and .odb file link is

https://docs.google.com/viewer?a=v&...MzJkOS00ZjNiLWFjNWEtN2JlOTA1OTZkMTFi&hl=en_US

Thanks.
Abu Hena Muntakim

 

[corus]

You're probably looking at nodal stresses which have been extrapolated from the element integration points, hence a slight error can occur. The element stresses should follow the input stress-strain curve. Use a finer mesh to reduce this error.

 

[henasr]

Dear corus,

i tried with fine mesh but it didn't match with input stress-strain curve.
i also tried to make avg. value of nodal stress and strain but no change.

how can i see the element stress?

when i turn on nlgeon then in contour there are stress strain variation but if i turn it off then no change in stress strain in the part.why this happen? Can you please help me with the reason?

i have a test result curve of stress and strain. Is there any special thing to give input in yield stress and plastic strain.

Thanks.

 

[MechIrl]

You have a number of basic problems here..I'd strongly advise you to read the getting started Abaqus manual and do some of the tutorials.

Your boundary conditions do not constrain your part sufficiently for a uni-axial tensile test. NLGEOM should be on as you are dealing with finite deformations.You are also assuming plain strain,which I imagine is one of the main sources of the discrepancies in your results.

When entering plasticity data it should be in the form of true stresses and plastic strains. Technically these stresses should never decrease, to mimic failure you should introduce a damage model or an imperfection.

 

[henasr]

Thank you very much MechIrl.
i have done this job with 3D model.
getting started with Abaqus helps me to give right input format of material.