This paper presents a combined theoretical and experimental investigation of fracture penetration through an interface. The results have application to hydraulicfracture containment in sandstone or limestone reservoir strata bounded by shale layers. Several simplifying assumptions and approximations are made. We assume that the interface separates dissimilar but adhering materials that are elastic to first order. We consider only differences in material properties and take stresses to be locally uniform. Approximations are made that reduce the fourth-order equation of plane strain elasticity to the second-order Laplace equation. Crack shape is taken to be sinusoidal and fluid leakoff is ignored.Additional simplifying assumptions are made about the shape of the crack tip as it passes through the interface. Using a virtual work analysis, we derive a relation for internal fluid pressure required to extend the crack through the interface. This pressure is related to the equilibrium pressure needed to hold the crack barely open. A simple relation is obtained involving only the shear modulus and surface energy of the materials on either side of the interface.The theory was tested in laboratory experiments with Plexiglas TM/resin bonds. Test blocks of several configurations were used with various kinds of external loading.Cracks were initiated by applying grease pressure in thin notches. Pressures required to hold cracks in equilibrium were compared with those required to penetrate interfaces. Results were consistent with the theory within limits of precision in measuring surface energy. We conclude that the theory explains field observations of containment in a number of reservoirs that have been fractured hydrualically.However, practical value is limited by inability to estimate surface energies from logging or other wellbore data.

Comfort levels on modern superyachts have recently been the object of specific attention of the most important Classification Societies, which issued new rules and regulations for evaluating noise and vibration maximum levels. These rules are named "Comfort Class Rules" and set the general criteria for noise and vibration measurements in different vessels' areas, as well as the maximum noise and vibration limit values. As far as the vibration assessment is concerned, the Comfort Class Rules follow either the ISO 6954:1984 standard or the ISO 6954:2000. After an introduction to these relevant standards, the authors herein present a procedure developed to predict the vibration levels on ships. This procedure builds on finite element linear dynamic analysis and is applied to predict the vibration levels on a 60 m superyacht considered as a case study. The results of the numerical simulations are then benchmarked against experimental data acquired during the sea trial of the vessel. This analysis also allows the authors to evaluate the global damping ratio to be used by designers in the vibration analysis of superyachts.

To assess the safety of people and cargo onboard, severe environmental conditions are to be taken into account. In such conditions it could be necessary to use tools allowing the simulation of the nonlinear behaviour of a vessel free running and manoeuvring in waves. The need for applying such advanced tools in certain situations is one of the outcomes of the IMO discussion on the development of Second Generation Intact Stability Criteria, and, in particular, regarding tools for “Direct Stability Assessment” and for the development of ship-specific operational guidance. Within this context, a nonlinear time domain simulation tool is applied in this paper for the case of a container vessel. Simulations have been carried out considering the vessel free running in irregular waves. A set of conditions have been specified for identifying human-related, systems&machinery-related and cargo-related failures from time domain simulations. Some results are reported and discussed

Scrubber systems abate the sulphur oxide emissions of engines when cheap fuel oils that are high in sulphur content are employed as combustibles. However, the ships with these voluminous devices installed on board is space demanding. This work analyses the feasibility of incorporating the acoustic abatement of the exhaust gas noise functionality into the scrubber design to provide a combined scrubber–silencer system. For this purpose, a finite element analysis is performed on a simple expansion chamber, which is assessed using both analytical and experimental data. The transmission loss is the acoustic parameter chosen in this work. The numerical model depicts a good correlation with the transmission loss measured on a model scale scrubber. Finally, scrubber geometry modifications alter the transmission loss, changing and/or enhancing its featuring. These abilities indicate the feasibility to confer to scrubber silencing effects.

In this paper a specific procedure for the structural assessment of a container stack is implemented to a realistic case in order to evaluate its effectiveness in the prediction of the operational limits of a container vessel. The feasibility of an extensive calculation based on such procedure is tested, paving the way to the direct analysis of a container stack subject to the inertial loads arising from the ship motions. The procedure is based on a 3D non-linear FE analysis coupled with a direct simulation of non-linear ship motions for the determination of inertial forces acting on a container stack. A non-linear approach has been used for modelling both the ship motion response and the container stack structural response, leading to a global large amplitude analysis. A simplified model of a container stack has been defined in order to decrease the computational cost of the structural calculations, allowing for a use in the framework of an extensive analysis considering many different ship sailing conditions. As final results, diagrams showing the occurrence of failure of container structures or lashing equipment are presented