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Back Stress in Abaqus

Could you please advise if that is correct to select higher number of back stresses (as input) while simulating test results in Abaqus?

It appears to me that the higher number of back stresses (say selecting number of back stresseses in Abaqus >= 5) give me a better fit to the test results. For my case, 5 is an optimal value as increasing it will not affect the results, much.

Thank you.

ABAQUS (6.8, 6.9 EF) - Effect of the number of back stresses

Since ABAQUS 6.8, a new feature has been added to the combined hardening material input.

Let's assume a combined Kinematic and Isotropic hardening case, such as those happen in metals.

"Half cycle" uni-axial test results has been utilized to model the yield stress-plastic strain behavior as well as the Kinematic behavior of the metals.

In the same user interface,  there is an option to choose the number of back stresses.

Is the number of 1 back stress is equivalen to the case of linear kinematic hardening (Ziegler's)?

Tensile coupon test - simulation of tensile coupons (after necking)

I have carried out several coupon tests (rectangular coupons similar to
those of ASTM E8). Some of these tests have kind of weird behavior. The
problem arises when I simulate results with ABAQUS. It goes pretty well
until a few steps after necking. Test and ABAQUS results match exactly
until several steps before fracture. After this point, there is a
discrepancy between results and my attempts in capturing the observed
behavior was unsuccessful. (around 10% or more plastic strain).

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