Within sheet metal forming, crashworthiness analysis in the automotive industry and ship research on collision and grounding, modelling of the material failure/fracture, including the behaviour at large plastic deformations, is critical for accurate failure predictions. In order to validate existing failure models used in finite element (FE) simulations in terms of dependence on length scale and strain state, tests recorded with the optical strain measuring system ARAMIS have been conducted. With this system, the stress-strain behaviour of uniaxial tensile tests was examined locally, and from this information true stress-strain relations were calculated on different length scales across the necking region. Forming limit tests were conducted to study the multiaxial failure behaviour of the material in terms of necking and fracture. The failure criteria that were verified against the tests were chosen among those available in the FE software Abaqus and the Bressan-Williams-Hill (BWH) criterion proposed by Alsos et al. 2008. The experimental and numerical results from the tensile tests confirmed that Barba's relation is valid for handling stress-strain dependence on the length scale used for strain evaluation after necking. Also, the evolution of damage in the FE simulations was related to the processes ultimately leading to initiation and propagation of a macroscopic crack in the final phase of the tensile tests. Furthermore, numerical simulations using the BWH criterion for prediction of instability at the necking point showed good agreement with the forming limit test results. The effect of pre-straining in the forming limit tests and the FE simulations of them is discussed.

A case study of a point-absorber wave energy converter (WEC) system is presented. The WEC system forms an array, with several WECs located around a central hub to which they are each connected by a short, freehanging power cable. The objective of the study is to analyse the dynamic characteristics and estimate the fatigue life of the power cable which is not yet in use or available on the commercial market. Hence, a novel approach is adopted in the study considering that the power cable's length is restricted by several factors (e.g., the clearances between the service vessel and seabed and the cable), and the cable is subject to motion and loading from the WEC and to environmental loads from waves and currents (i.e., dynamic cable). The power cable's characteristics are assessed using a numerical model subjected to a parametric analysis, in which the environmental parameters and the cable's design parameters are varied. The results of the numerical simulations are compared and discussed regarding the responses of the power cables, including dynamic motion, curvature, cross-sectional forces, and accumulated fatigue damage. The effects of environmental conditions on the long-term mechanical life spans of the power cables are also investigated. Important cable design parameters that result in a long power cable (fatigue) service life are identified, and the cable service life is predicted. This study contributes a methodology for the first-principle design of WEC cables that enables the prediction of cable fatigue life by considering environmental conditions and variations in cable design parameters.

S U M M A R YA 2-D model of a fault plane with inhomgeneous slip resistance is investigated using a finite element method. Slip is nucleated at a weak spot, and propagates initially in both directions. At one side of the nucleation point, the resistance to slip is assumed t o increase along the fault. This causes the slipping edge t o reverse its direction. In this way unidirectional slip with o n e leading and one trailing edge emerges. A t the leading edge slip is assumed to propagate according t o a critical shear stress criterion combined with a slip weakening law. At the trailing edge, where the process of healing occurs, slip is assumed to b e arrested in a n energy-neutral way. The simulations indicate that a steady state unidirectional slip is approached. The edge velocities can b e very high and even overshoot the shear wave velocity.

This study presents an experimental and numerical investigation of a taut-moored wave energy converter system with a point-absorber type of wave energy converter. The wave energy converter system consists of a buoy, a unique three-leg two-segment mooring system with submerged floaters, and a power takeoff system designed for the current experiment as a heave plate. The main objective of the study is to validate a numerical simulation model against experiments carried out in an ocean basin laboratory. Two physical models in model scales 1:20 and 1:36 were built and tested. The detailed experimental testing programme encompasses tests of mooring system stiffness, decay tests, and different sea state conditions for ocean current, regular, and irregular waves. A numerical model in the model scale 1:20 was developed to simulate coupled hydrodynamic and structural response analyses of the wave energy converter system, primarily using potential flow theory, boundary element method, finite element method, and the Morison equation. Several numerical simulations are presented for each part of the experimental testing programme. Results for the wave energy converter buoy motions under operational conditions from the experiments and the numerical simulations were compared. This study shows that the simulation model can satisfactorily predict the dynamic motion responses of the wave energy converter system at non-resonant conditions, while at resonant conditions additional calibration is needed to capture the damping present during the experiment. A discussion on simulation model calibration with regard to linear and non-linear damping highlights the challenge to estimate these damping values if measurement data are not available.