Figure 20:

Deformations of the torsion test (Section 4.4), along with mean values of J within each element calculated via equation (69), using the Mooney-Rivlin material model, equations (46) – (49), with c₁, $c_2=9000\frac{\text{dyn}}{{\text{cm}}^2}$. The background Eulerian grid is not shown. Shown here are solid meshes with Q1 elements and m = 3969 solid DOF. The first row shows cases with ν_stab = .4, and the second row shows cases with ν_stab = −1 (here equivalent to κ_stab = 0 and no volumetric-based stabilization). The first column shows cases with modified invariants, and the second column depicts cases with unmodified invariants. Note the extremely unphysical deformations shown in panel (d) generated when using unmodified invariants without volumetric-based stabilization.