Lack of quadratic convergence

[jfriedlein]

For numerical examples that incorporate shear components or distorted elements, no quadratic convergence for a full Newton-Raphson method can be achieved/seen. Maybe due to the "selective reduced integration" (or some type of this), which incorrectly (?) does not evaluate the true stress state at the midpoint of the element, leading to an inconsistent formulation and no proper convergence.