Discretization Challenges in Crash Simulations: Mesh, Geometry and Failure Criterion Effects From the Energy Perspective

Abstract

The simulation of collisions of ships using FEA has a long history of rules and guidelines to which such simulations should conform. Nevertheless, there are still subjects that lack thorough understanding in literature and standards. With the rise in popularity of stress state dependent failure criteria and the ability to simulate with smaller element sizes, new questions arise. This paper is part of an ongoing sensitivity study of the effect parameters such as element size, choice of failure criterion, geometric placement of the striking vessel and friction have on the dissipated energy in a collision simulation. It is shown that the use of different mesh sizes and different failure criteria results in different failure mechanisms and deformation patterns and have a great effect on dissipated energy. The stress states in which most of the plastic work is performed (and therefore energy is dissipated) are shown to be in the triaxiality range of 0.27–0.35. The energy contributions of the regions above that, towards equi-biaxial tension, and below that, towards pure shear, are very significant on first contact and shape the initial deformation mechanism. Furthermore it is shown that the placement of the incoming V-bow with respect to element boundaries significantly influences the energy absorption. The parameters influencing energy dissipation are numerous and just a very small selection is discussed in this paper. No perfect deterministic approach is presented in this paper, but a base for a probabilistic approach is given.