ABSTRACT This paper outlines an experimental investigation into the durability of large-scale adhesively bonded joints with a thick layer of methyl methacrylate adhesive (MMA). Ageing has been performed by immersion in a 3.5 wt% NaCl solution for 10 weeks at 50°C. Two aged and one unaged specimen were subjected to tensile testing, and three aged and one unaged specimen were loaded up to ~ 3.5 million fatigue cycles followed by a residual tensile test. The ductility of the adhesive is affected by ageing and fatigue testing. Despite a decrease in ductility, the plastic zone development was adequate for the required strain redistribution without compromising the joint performance (strength and stiffness) demonstrating the fatigue tolerance of the joint. The shear, longitudinal, and peel strain values in the adhesive bulk are evaluated by digital image correlation. The shear strength values are significantly higher than the requirements following from the design. All specimens failed by sudden delamination of the composite plate. Post-mortem analysis showed no corrosion travel at the interface of steel and adhesive.

AbstractThis work reports a study of the fatigue behaviour and quasi‐static strength of full‐scale adhesively bonded steel‐composite joints. Three joints with an approximately 10‐mm‐thick layer of methyl methacrylate adhesive were manufactured in dockyard conditions. One specimen was tensile tested till failure, while two specimens were subjected to ~3.5 million fatigue cycles, followed by a residual tensile test supported with digital image correlation. The shear, longitudinal and peel strain values within the adhesive bondlines are significantly higher at the gripped sides due to the asymmetrical design of the steel brackets. All specimens showed a significantly higher shear strength than the design values defined by the shipbuilder. Fibre Bragg sensors monitored strains at steel and composite constituents and allowed to detect damage onset and evolution in tensile tested specimens. A finite element model of the joint was developed with material and interface properties based on dedicated small‐scale experiments. The simulation results of strains during a static load test corresponded closely to the DIC measurements. All specimens failed near the composite‐adhesive interface due to delamination of the composite panel.

Onboard observer programs have been implemented since the 2000′s to monitor the impact of tropical tuna fisheries on pelagic ecosystems. The recent development of Electronic Monitoring Systems (EMS) offer new insights to improve the monitoring and estimation of discards at sea, which remains a challenge for observers on board purse seiners where catch handling occurs simultaneously at different places on the vessel and often represents large volumes discarded within a short amount of time. In this study, data collected through EMS installed on board French tropical tuna purse seiners operating in the Indian Ocean were used to examine the sorting process and test optimized observer sampling strategies to obtain robust estimates of discards. We used EMS “counts per minute” data to estimate the total amount of discards in numbers, as well as discards per taxa by fishing set. Results indicate differences in the flow of discards among species and sorting location with 82% of the individuals released through the discard belt in the lower deck, the rest being directly released from the upper deck. Observer sampling strategies were simulated with the aim of optimizing the total sampling duration and the duration of sampling sequences by assessing the bias and coefficient of variation of the estimates. Based on these results we recommend a protocol for onboard observers using a minimal coverage of 22 min of sorting operations in the lower deck, with sampling sequences of 2–4 min for large volumes of catch. Further strategies to improve the estimation of discards combining onboard and electronic observations are also discussed.

Abstract Offshore underwater structures degrade over time due to the harsh environment and operating conditions of the structure leading to potential problems such as fatigue cracking or corrosion. This necessitates the need for regular inspection, monitoring, and possibly repair to ensure that the structurescontinue to operate safely. However, conventional inspection techniques face significant challenges when inspecting subsea structures, particularly related to the access of the area of interest. Removal of marine growth in these areas and the safe use of remotely operated vehicles (ROVs) can be time consuming and problematic. To address these challenges, a unique approach was developed that combines different advanced non-destructive testing (NDT) techniques to maximize productivity and minimize intrusions while ensuring the data collected is the high quality needed for integrity assessment, allowing for the safe operation of critical assets. This approach involves a combination of long-range ultrasonic testing (LRUT) technology with marinized transducer tooling, underwater Pulsed Eddy Current (PEC) testing, and underwater Alternating Current Field Measurement (ACFM) to inspect subsea structures. The LRUT technology is initially used to screen piles for overall condition with marine growth only needing to be removed at the tool location. PEC is used to verify critical findings without removing any marine growth. ACFM is used to inspect underwater welds for fatigue cracks, all with minimal removal of marine growth. This approach has successfully implemented in the field, including the use of underwater marinized LRUT collars, to inspect approximately 1000+ piles of circular piles (LRUT for 700+ circular piles and ACFM & PEC for 1000+ piles which includes circular and hexagonal piles) with different diameters and wall thicknesses. This technical paper provides details about the challenges encountered during implementation and how they were overcome. Furthermore, it shares real site experience and results of this innovative inspection program. The results were validated by cross-checking with other techniques such as underwater ultrasonic thickness gauging (UTG) and close visual inspection (CVI) by qualified divers to ensure accuracy and reliability of the results.

The fundamental solution of the ship-motion problem, known as the ship-motion Green function associated with a pulsating and translating source, is formulated and analyzed based on the weakly damped free-surface flows. The inclusion of viscous effects modifies the dispersion relation, resulting in the existence of three wavenumbers instead of two, as observed in inviscid fluids. The Green function with viscous effects is examined in relation to these three complex wavenumbers, and novel formulations of Havelock's type are developed. Special attention is paid to the analysis of several numerical issues and the treatment to resolve them. The wavenumber integral function involved is analyzed using contour integration in the complex plane, leading to a classical formulation that includes the exponential integral function and a constant function representing the contributions of residues. Additionally, new series and Taylor expansions are developed to facilitate the integration of the ship-motion Green function on ship hull and the free surface. Furthermore, derivatives and antiderivatives of the wavenumber integral function have been obtained for all three formulations. Numerical examples are included to illustrate the soundness of the formulations and their efficiency in numerical evaluations. At the critical frequency, in particular, the Green function with viscous effects is shown to be finite and its magnitude decreases along the horizontal distance from the source. Finally, benefits of introducing viscous effects in the fundamental solution are examined and emphasized in the discussion and conclusions.

Abstract. This paper provides a summary of the work done within Phase IV of the Offshore Code Comparison Collaboration, Continued, with Correlation and unCertainty (OC6) project, under International Energy Agency Wind Technology Collaboration Programme Task 30. This phase focused on validating the loading on and motion of a novel floating offshore wind system. Numerical models of a 3.6-MW horizontal-axis wind turbine atop the TetraSpar floating support structure were compared using measurement data from a 1:43 Froude-scale test performed in the University of Maine’s Alfond Wind-Wave (W2) Ocean Engineering Laboratory. Participants in the project ran a series of simulations, including system equilibrium, surge offsets, free-decays, wind-only conditions, wave-only conditions, and a combination of wind and wave conditions. Validation of the models was performed by comparing the aerodynamic loading, floating support structure motion, tower base loading, mooring line tensions, and keel line tensions. The results show a good estimation of the aerodynamic loading and a reasonable estimation of the platform motion and tower base fore-aft bending moment. However, there is a significant dispersion in the dynamic loading for the upwind mooring line. Very good agreement was observed between most of the numerical models and the experiment for the keel line tensions.

Real-time assessment of flooding risk associated with the collision between two ships, requires a fast estimation of damage dimensions and associated survivability. The state-of-the-art frameworks for risk assessment on passenger ships do not consider a direct evaluation of damages through crash simulations but refer to probabilistic considerations, modelling damage characteristics according to statutory marginal distributions of damage breaches too old to be any longer relevant. In any case, such an approach is not possible for the real-time risk assessment process developed in project FLARE, aimed at promoting the employment of first-principles tools for risk evaluation. In this spirit, the present work investigates the possibility of developing a database-oriented damage breach model, which employs direct crash analyses with the super-element code SHARP. However, the sole usage of crash simulations is not suitable for real-time applications. Therefore, starting from the collision simulation database, surrogate models have to be derived for real-time application. In this specific case, three different strategies have been used for the models creation namely: multiple linear regressions, neural networks and decision trees. Here, the strategy to build the database and application on a reference passenger ship is described, highlighting the differences in accuracy and calculation time between the proposed surrogate models.

Earth's inner core acquires texture as it solidifies within the fluid outer core. The size, shape and orientation of the mostly iron grains making up the texture record the growth of the inner core and may evolve over geologic time in response to geodynamical forces and torques1. Seismic waves from earthquakes can be used to image the texture, or fabric, of the inner core and gain insight into the history and evolution of Earth's core2-6. Here, we observe and model seismic energy backscattered from the fine-scale (less than 10 km) heterogeneities7 that constitute inner core fabric at larger scales. We use a novel dataset created from a global array of small-aperture seismic arrays-designed to detect tiny signals from underground nuclear explosions-to create a three-dimensional model of inner core fine-scale heterogeneity. Our model shows that inner core scattering is ubiquitous, existing across all sampled longitudes and latitudes, and that it substantially increases in strength 500-800 km beneath the inner core boundary. The enhanced scattering in the deeper inner core is compatible with an era of rapid growth following delayed nucleation.

This study aims at the experimental investigation of wave-induced motions and loads of a containership model without forward speed in -120 degree oblique regular waves to study the influence of the wave steepness and provide reference data for future benchmark studies. A mooring system with 4 horizontally arranged spring lines was used to maintain the heading angle of a 1/65 scaled 9-segmented model designed to be as rigid as possible.Focuses were on studying the nonlinear effects due to the wave steepness on the vertical bending moment (VBM) and horizontal bending moment (HBM) near amidships, and 6-DOF motions at the center of gravity (COG) of the model. Several wave series that are distinguished by wave steepness were considered in the experiment accordingly. Each series consists of waves with various periods that were intended to cover the peak of the wave bending moment transfer functions. Through this, the nonlinear wave effects on the responses of the rigid body at various periods were determined. It was confirmed that the steeper wave contributes to the increase in the higher-order harmonic components including slamming events in the bending moments measured. The change in the characteristics of the wave bending moments according to the change in wave steepness was found to be very different from the linear response.A detailed discussion was made on the influence of the mooring system on the asymmetric horizontal bending moment (HBM) and the change in the average yaw motion. Experiments with and without a mooring system under the same wave condition were conducted, and the effect of the mooring system was identified. It was qualitatively confirmed that the mooring system’s restoring moment correlates with the asymmetric HBM and average yaw movement change.