Dear Mr. Bergström,

dear forum-users,

how did you derivate the jacobian of the neo-hookean model (Abaqus UMAT subroutine) in Chapter 10? I'm asking because I've derivated the lagrangian elasticity tensor from the second piola-kirchhoff stress tensor. By applying a push forward operation I get the eulerian elasticity tensor (same as in: Bonet & Wood: Nonlinear Continuum Mechanics For Finite Element Analysis (2nd Edition), p.170). The point is, your Jacobian is working and mine does not converge. What I'm doing wrong?

I've tested the Neo-Hookean model in a MSC.Marc subroutine (HYPELA2). With 2nd Piola-Kirchhoff-stresses / Lagrangian elasticity tensor / Large Strain / Total Lagrange everything is fine. But if I switch to Large Strain / Updated Lagrange settings in MSC.Marc Mentat and calculate the cauchy-stresses / eulerian elasticity tensor in my subroutine it does not converge at larger strains. I assume that I've made a mistake in the push forward operation of the elasticity tensor.

Thanks!

(sorry for the bad quality of my scan, forum is scaling down the resultion)

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