Modeling hyperelasticity using Mooney-Rivlin strain energy density function

[VincentDillen]

Hi All,

I'm trying to model a hyper elastic material using the following equation, which is a simplified version of Mooney-Rivlin strain energy density function:

W=c(I-3)

But the problem is that when I am differentiating W with respect to E to obtain the components of my tensor, E disappears. In other words I get a CONSTANT value which means no variation.

What is wrong with my computation?
(I consider I=c11+c22+c33, E=2c+1)

Thanks

 

[IceBreakerSours]

Is this for coursework? Grab a decent book. Almost everything that you've written is wrong.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[VincentDillen]

No it's not for a coursework. But I'm new to FEM and continuum mechanics.
Thanks for guidance.

Vincent

 

[IceBreakerSours]

Okay, visit continuummechanics.org *AND* solidmechanics.org *AND* purchase a decent book on CM. Holzapfel's book is an easy read, for example.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083