| Low order structural elements are widely used in simulations because of their efficiency. In particular, shell element with one-point quadrature, e.g. Belytschko-Lin-Tsay element, is very popular for industry use cases. However, this kind of element formulations has several drawbacks: (1) rotational degrees of freedom need a complicated update procedure and cause some difficulties when applying hard- or soft-support boundary conditions; (2) the plane stress assumption requires modification to general 3D constitutive laws to be applied to shell elements; and (3) mid-surface description is not amicable to contact detection for some applications, e.g. forging. To address these problems listed above, some early research has shown that the 8-node solid elements can be successfully adapted for shell modeling, so long as the various locking phenomena are properly taken care of.;In this work, a solid-shell element is designed for use of modeling thin structures. By applying Assumed Natural Strain and Enhanced Assumed Strain methods, we remedy the various common locking modes: transverse shear locking, transverse thickness locking, membrane locking, volumetric locking and curvature thickness locking. Furthermore, the base of this element, being a solid element, has several virtues: (1) all degrees of freedom are displacements; (2) general constitutive laws can be used without modification; (3) and element surfaces are suitable for use in contact detection.;This element formulation is then combined with the phantom node method, which is equivalent to XFEM with only Heaviside enrichment and element-wise cracking, to model dynamic fracture problems. The integration in enriched elements utilizes the divergence theorem to turn volume integral into integral over surfaces, and provides better accuracy than the domain-fraction used in the original development. |
