Implementation and stability analysis of the QMITC-TLH elasto-plastic finite strain (2D) element formulation

In several articles that were published in the last few years, it was discussed the fact that some new four-node elements, based on the enhanced and mixed strain techniques, even though are stable for infinitesimal strain analyses, develop spurious zero energy modes under some finite strain deformation patterns. Hence, we find of strong interest to re-analyze our QMITC-TLH four-node element, previously formulated for elasto-plastic finite strain analyses. In this paper, we discuss some implementation details of the element and we show, for specific finite strain deformation patterns, that the element formulation is free from spurious zero energy modes.