Tabulated data for MAT LAW36 (PLAS_TAB), MAT LAW60 (PLAS_T3)

Autumn

Hello,

I have tabulated stress-plastic strain data for a certain material that, when plotted, looks something like figure (a) in the attached image, where the curves f_1 through f_5 are associated with different strain rates (and the strain rates associated with each function are such that 1 < 2 < 3 < 4 < 5). Thus, there is a bit of jumping around, and the data doesn't simply increase with increasing strain rate (unlike in figure (b) in the same attached image).

In the Radioss Reference Guide (2020), for both Law 36 and Law 60, it mentions "Strain rate values must be given in strictly ascending order". I am assuming this is only related to how the data is actually input into the material card and not how the data curves land on a stress-strain plot, but am curious about the expectations of what the data looks like, since the figure included with the definition of both material cards seems to suggest data from (b) is preferred (I have also attached the image from the Reference Guide).

Thus, does the stress-strain data also need to be increasing as in (b), or could it look like what's depicted in (a)?

Additionally, if it's possible to use tabulated data that looks like (a), I am wondering if MAT LAW60 could produce some weird results with its cubic interpolation or if there's any preference between using MAT LAW36 and MAT LAW60.

Thank you in advance for your help and any suggestions.

PaulAltair

Not sure on this, I ran a small test on the rate dependent tensile test model from help, swapping a pair of the curves over (3 and 5) while the model doesn't 'blow up' the results look a bit odd (strain rate is contoured in the example) (attached)

Radioss is interpolating between strain rates normally, it does this linearly, so not sure what it will be doing exactly in the scenario you describe, I'm not sure that would be a typical/foreseen usecase.