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Selection of Suitable Material Model within PolyUMOD Library

Posts: 7
Topic starter
Active Member
Joined: 7 years ago

Dear Jorgen,

Recently I have purchased MCalibration and PolyUMOD Library and did certain calibration work. In those work I realise that for same data set, for a certain material model, I obtain different material parameters when calibrating it at different occasions. But each will perfectly with with R2=0.999.

For example, if we have engineering stress vs strain data for a polymer; and calibrate with Bergstorm Boyce model ; at a certain instance I will get parameters of that model with R2=0.999 etc. (perfect calibration)

However when I test the same model again at different time, I will be able to match with Bergstrom Boyce model, but with different parameters of the same model. 

The question is how can a model will get perfect calibration with different parameter combination at different try out.

In this situation, May I know how to know in which try I get the correct parameters.

This question really bothering me.....

Your aid will help me a lot in using the software more efficiently.

Many Thanks 



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2 Replies
Posts: 17
Joined: 1 year ago

That is an interesting question. I have not seen your experimental data, but my guess is that you don't have enough experimental data for a proper calibration of the Bergstrom-Boyce (BB) model. Do you have, for example, different strain rates and/or loading and unloading?

If you have enough experimental data then it is usually very difficult to reach R2=0.999, and you usually get the same material parameters for each calibration attempt.


Posts: 7
Topic starter
Active Member
Joined: 7 years ago

Hi Dr Jorgen,

Many thanks for your prompt reply. Actually I am testing Soft Bio Tissues and that's the reason of selecting BB Model. However so far I have done Uniaxial tensile test (only loading till the sample fracture) for a single strain rate due to scarcity of the material. However I have planned to do more tests on that.

Just a few questions

1). Are there any model that is suitable for these bio materials that can be calibrated for one strain rate only for loading till fracture in PolyUMOD Library ?

In the attached file it is shown the results calibrated for BB model and ABAQUS HGO. BB is the most suitable one in that scenario. Complete curve till the fracture was not included in the calibration work as still i do not know how to include damage in the calibration curve.

If you have some time, can you put up a small video on how to introduce damage in the calibration please ?

However I enjoy the software and would like to explore more stuff in this software in the future.

Thank you very much Dr Jorgen.