Towards a unified methodology for the simulation of rupture in collision and grounding of ships

• Simulation of eighteen indentation tests using the explicit finite element code Abaqus 6.10-2 and shell elements.
• Definition of the material true stress-strain curve using an isotropic hardening material that follows the J2 flow theory.
• Implementation of three rupture criteria; the critical equivalent plastic strain, the BWH and the RTCL criterion.
• Determination of the critical equivalent plastic strain as a function of the length over thickness ratio of the element.
• The criterion based on a critical equivalent plastic strain simulates the tests in a realistic manner.

The aim of the work is the definition of a procedure for the numerical simulation of the response of ship structures under accidental loading conditions, which suffer various different modes of failure, such as tension, bending, tearing and crushing and in particular to investigate the effect of material modeling, i.e. material curve and rupture criterion as well as mesh size and strain rate effect on the results. To this end, different material models and simulation techniques were used for the simulation of eighteen indentation tests conducted by different research groups. The simulations were performed using the explicit finite element code ABAQUS 6.10-2. The tests refer to the quasi-static and dynamic transverse and in-plane loading of various thin walled structures which represent parts of a ship structure. Three rupture criteria are incorporated into VUMAT subroutine, which interacts with the explicit finite element code and refers to an isotropic hardening material that follows the J2 flow theory assuming plane stress conditions, in order to investigate the prediction and propagation of rupture. The focus is on investigating whether it is possible to define a unified methodology, which is appropriate for the simulation of all different tests. Consistency in the numerical results is observed with the use of an equivalent plastic strain criterion, in which formulation a cutoff value for triaxialities below −1/3 is included.