Jacobian of hyperelastic model

Hi, everyone.

I was working with the umat of hyperelastic model (espacially the Mooney-Rivlin model). Firstly I read the Abaqus Theory Manual, in section 4.6.1, the material jacobian C_ijkl are consisted of deviatoric part C-s and volumetric part K, see the equation (4.6.1-12)([B]FIG.1[/B]). Also the abaqus gave the details of jacobian of Neo-Hookean model([B]in FIG.2[/B]). But I can not figure out where the second to last term in the expression comes from.Would you kindly help me ?

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Hi zqctate,

Did you manage to figure out the above? I am currently trying to understand the same example.

Regards,

Robbie