Hyperelastic model acting too stiff
I am working on calibrating the Yeoh hyperelastic model together with a prony series for a polyurethane coating material. I think i am 99% there, but for some reason the results using the calibrated hyperelastic model act strange (too stiff) in Abaqus although the results look fine in MCalibration even for virtual load cases. I confirmed this by doing a one element model (only for the hyperelasticity) where the stresses turned out to be more than 200 times larger than what i would expect. Therefore i supect there is something basic wrong, and not just a bad calibration (it looks quite good visually in MCalibration).
An example of the parameters i obtained for the Yeoh hyperelastic model is C10=93.8MPa, C20=-7.24MPa, C30=1.08MPa, D1=0.0018MPa^-1, D2=0.0347MPa^-1, D3=0.0347MPa^-1. Looking at other examples in literature for these parameters they seem too high (around a factor 100), but i can't find out where the mistake is. I tripple checked the units, tried calibrating using different types of experimental data, and more, but it did not solve the issue.
Anyone who has experienced something similar and have an idea of what could be wrong with my calibration?
Thank you in advance.
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Your deviatoric parameters do look problematic. I also doubt you need 3 coefficients to model the volumetric response unless you are studying extremely high pressures.
Let me know what loading mode your deviatoric characterization data is, and send me data points on this thread at 1%, 2%, 5%, 10%, 25%, 50%, 100%, 200%...up to failure strain. I will probably be able to tell you if your coefficients are even in the ballpark.