This work exploits the high accuracy of the mixed 3−field u/e/p formulation to address materially non-linear inelastic problems including isochoric deformations.

Motivated by the strain-driven format of several constitutive equations used in FEA, the mixed u/s/p formulation is reinterpreted, selecting the deviatoric strains as primary variables, together with the displacements and the pressure field.

The mixed formulation is complemented with several constitutive equations suitable for Solid and Fluid Mechanics.

The convergence rate upon mesh refinement, as well as the enhanced accuracy of the stress and strain fields is proven in several non-linear problems with isochoric deformation in both the elastic and the inelastic ranges. 2D and 3D problems involving different FE discretizations are solved with J2−plasticity, J2−damage and Bingham models, all of them including strain localization. Numerical results show that perfectly convergent and mesh-independent results are achieved in terms of peak load, failure mechanism, stress release and energy dissipation. Revealing comparison with the u/p formulation is also addressed.

这项工作利用混合3场u / e / p公式的高精度来解决材料非线性非线性问题，包括等速变形。

受FEA中使用的几个本构方程的应变驱动格式的激励，重新解释了混合的u / s / p公式，选择了偏应变作为主要变量，并选择了位移和压力场。

混合的配方补充了适用于固体和流体力学的几个本构方程。

网格细化的收敛速度以及应力场和应变场的增强精度已在弹性和非弹性范围内等速变形的几个非线性问题中得到证明。利用J 2-可塑性，J 2-损伤和Bingham模型解决了涉及不同FE离散的2 D和3 D问题，所有这些都包括应变局部化。数值结果表明，在峰值载荷，破坏机理，应力释放和能量耗散方面，均获得了完全收敛且与网格无关的结果。还讨论了与u / p公式的比较。