Hyperelastic material

[VaidehiChennubhotla]

Hi,

A Hyperelastic material model was used for compression test on a 50x50x50 mm block. The compression test data (FS curve) was overlaid on the CAE data. It fails to replicate the test data behavior miserably, shown in below picture. Hyperelastic material in general has uniaxial test data Nominal Stress, Nominal Strain and field variable. As I understand tensile test data is used twice and a shear field variable and shear failure criterion is given to show when it fails. Please correct me if I am wrong. I am having difficulty to match the CAE data to Test data. What can be done to the Hyperelastic material card, to make it match with test data? Any help would be greatly appreciated.

Regards,
Vaidehi

 

[FEA way]

Generally the same concepts as in the previous thread (about crushable foam material) apply. Besides that volumetric locking is much bigger problem with hyperelastic materials. Thus carefully select element type for the analysis. Also keep in mind that in case of hyperelastic materials you can use material calibration feature available in Abaqus/CAE.

 

[VaidehiChennubhotla]

Hi FEA way,

Thanks for the reply. I reduced the mesh size to 3 elements along the length, and also played around with the element type. One last time, I played around with the data a little bit and it gives me this warning. Would you be knowing what this means ?
***WARNING: THE PLASTICITY/CREEP/CONNECTOR FRICTION ALGORITHM DID NOT CONVERGE AT 8 POINTS

Regards,
Vaidehi

 

[FEA way]

Does your model have any of these features mentioned in the warning message ? It is highly advised to calibrate materials using very simple, single element models. Not only because they take less time to solve but also to avoid issues with additional features that are unnecessary for material calibration analyses.

 

[VaidehiChennubhotla]

Hi FEA way,

I think there is some hour glass effect in the model. The element seem to be flipping into the bottom nodes.

Regards,
Vaidehi

 

[FEA way]

Which type of elements is used in the case shown in this picture ? Which material model is that - hyperelastic or crushable foam ? Make sure that all units are correct.

Can you attach this model's file (.inp or .cae) ? I would take a closer look.