Hull form optimization from a hydrodynamic performance point of view is an important aspect of ship design. This study presents a computational method to estimate the ship seakeeping in regular head wave. In the optimization process the Genetic Algorithm (GA) is linked to the computational method to obtain an optimum hull form by taking into account the displacement as design constraint. New hull forms are obtained from the well-known S60 hull and the classical Wigley hull taken as initial hulls in the optimization process at two Froude numbers (Fn=0.2 and Fn=0.3). The optimization variables are a combination of ship hull offsets and main dimensions. The objective function of the optimization procedure is the peak values for vertical absolute motion at a point 0.15LBP behind the forward perpendicular, in regular head waves. http://www.transnav.eu the International Journal on Marine Navigation and Safety of Sea Transportation Volume 8 Number 1
In this paper, we examine the buckling behavior of piezoelectric laminated plate made of two-layered functionally graded materials (FGMs) that are integrated with surfacebonded piezoelectric actuators and is subjected to a combined action of uniform temperature change, inplane forces, and applied actuator voltage. Temperature-dependent material properties are assumed for both the substrate FGM layer and piezoelectric layers. Employing an analytical approach, five coupled governing stability equations, which were derived based on the first-order shear deformation plate theory, are converted into a fourth-order and a second-order decoupled partial differential equations. Then, an accurate analytical solution is proposed to solve them. Parametric studies are also undertaken, and show the effects of applied actuator voltage, volume fraction exponents, plate aspect ratio, ratio of piezoelectric layer thickness to thickness of FGM layer and temperature dependency, on the buckling load of the plate.
Manufacturing defects in the sandwich structures have significant impact on their ultimate strength performance. It is essential to codify some criteria for the effects of such defects on the performance of the structure in order to investigate the quality of sandwich compo-sites and their load-bearing capabilities. By means of such criteria, one can predict the property degradation of the defected structure in comparison to a defect-free one, and assess whether the faulty part could be remained in the structures. Among all the potential defects in a sandwich structure they could be induced during the Vacuum Infusion Process (VIP), the dry area defect is the most significant and frequently occurring one. Hence, adequate tests should be conducted in order to examine the effect of dry area defect on the structure. For this purpose, a methodology is required for preparing the defected samples similar to the main structure. The current study is aimed at suggesting two accurate approaches to induce artificial defects in sandwich structures manufactured implementing the vacuum infusion process. These methods are used for making some defected samples and their responses are compared with those of the defect-free structures. All samples are subjected to the uniform inplane compression loading and their behaviors up to the fracture point are evaluated to assess the remaining strength. Infusion process.
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