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Negative hardening parameter in NLSTAT thermal analysis

gopal_rathore

Hi,

I am working on a NLSTAT thermal analysis where I have a temperature dependent material properties (at two temperature conditions)

Used the foll. material cards:

1) MAT1 , MATS1

Used TABLSE S1 along with TABLE ST FOR Stress-Plastic strain curve and temperature value

Facing the foll. error now

*** ERROR # 3017 ***
Negative hardening parameter H = -22964.325723 found.
Negative value of H violates Drucker's stability postulate.
This error prevents further computations and must be corrected.

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Rahul Rajan_21763

During the nonlinear iterative solving process, the temperature loading is applied incrementally just as other loadings. As the temperature changes, the stress-strain curves will change as well. So it is possible that the negative H happens in the curve generated at the final iteration. I would suggest to check the data input carefully in HM to make sure all the data curves are correctly input.

gopal_rathore

Hi,

I have got temperature mapped on the nodes of the mesh and are in the range of 550K -599 K.To consider this temperature values , I have ,made two stress-strain curves i.e one at 373 and second at 573

Order in TABLEST is 373 K and then 573 K

Does the solver goes for linear interpolation between tow temperature values?

let me know if there is any ambiguity in the table

image.png.f6eafa8a704dfd56c59c36a5149dbf8c.png

image.png.0e4cd30c31ebf4ae8cdae7e82f43c4ba.png

Rahul Rajan_21763

I don't think we do extrapolation in this case, hence the error.

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