Learning Forum

[Jia-Wei Liao]

When I was doing nonlinear simulation of large deformation of breast compression, I saw that some papers used hyperelastic Mooney–Rivlin model, and some papers used hyperelastic neo-hookean model in the selection of breast material properties.

 

I used Mooney–Rivlin at the beginning, and the result was element highly distorted error. Later, I switched to neo-hookean and the other conditions were the same, and the calculation converged successfully.

 

I would like to ask what is the main difference between Mooney–Rivlin and neo-hookean? Why can the highly distorted element be solved after changing the material properties? The calculation results using neo-hookean will be more inaccurate than Mooney–Rivlin ?

Thanks for your help!!!

[John Doyle]

Both models are based on a strain energy density function.  NeoHookean is the simplest (mathematically) of all the hyperelastic options, but it also is limited to relatively small strain (<30%) and typically only curve fits well for mildly nonlinear stress strain curves without inflection points. 
I would refer you to Section 4.6 of the MAPDL Material Reference Guide available online for a more rigorous explanation of all the hyperelasticity material options.   
If NeoHooekan result passes all your validation requirements, then you should be fine to use it.