Search

The aim of this article is to evaluate the effects of cargo relative weight and its distribution along the boat's length in addition to the relative water wavelength on the dynamic performance of a high-speed planing hull. Here, the dynamic performance is measured by the intensity of the boat's heave and pitch motions. The Zarnick's strip theory, which divides the vessel's hull into equal lateral sections, is used to study the applied forces on the vessel, and a MATLAB code is provided based on it. It is demonstrated that increasing the cargo weight and its distribution result in more heave and pitch, and the maximum amount of them are observed in the wave with a length of about 5 times the length of the boat. In addition, the interactive effects of cargo weight and its distribution on the heave and pitch motions are affected by the relative wavelength. Therefore, the more centralized cargo distribution is preferred to increase the dynamic performance of a heavy planing boat with cargo weights more than 50% of the boat's weight, while moving in short waves (λ⁄L<4); and for light cargo weight, less than 50% of the boat's weight, the favorite cargo distribution is broad. When the boat sails in long waves, the desired distribution is reversed. [ABSTRACT FROM AUTHOR]

Due to the presence of holes in composite mechanical joints, stresses around the holes are increased, and they may cause failure in the composites. Analysis of the composite behaviour after damage initiation around the holes is important, complex, and mostly three-dimensional. In order to achieve accurate results about the composite failure modes, damage analysis using a modern criterion is needed. In this research, to investigate the damage behaviour of a unidirectional multi-layered composite plate of a mechanical joint under pure tension, three codes are prepared in the USDFLD, VUSDFLD and VUMAT subroutines based on the Hashin criterion and implemented in ABAQUS software. These codes, using the methods of suddenly and gradually degradation in composite properties, progressively simulate the three-dimensional damage behaviour of the composite plate after damage initiation. The results show that, when a mechanical joint is under pure tension, the adequate distance from the edge of a hole to the edge of a composite plate is about two times the hole diameter. Furthermore, it is found that to rapidly investigate and analyse a mechanical joint in the composite structures, the USDFLD subroutine, which uses suddenly decreased material properties after damage initiation, is reasonable and more efficient. [ABSTRACT FROM AUTHOR]

Along with other hydrogen barrier coatings, thermally sprayed coating is one of the potential barriers against hydrogen permeation. In this research, specifications of hydrogen diffusion through thermally sprayed 316L stainless steel coating over structural steel are scrutinized by different methods, including complete and partial charging and discharging tests utilizing Devanathan–Stachurski cells. Besides, various mathematical methods are applied to obtain data about the diffusion coefficient of hydrogen, in addition to the solved and trapped hydrogen contents in the coating. The analyses are supported by means of X-ray diffraction (XRD) and microstructural observations to confirm interpretations of hydrogen permeation behavior across the coating. Because of the specific microstructure of the sprayed coatings and continuous ferritic phases across the coating, which develop short pathways for hydrogen diffusion, the thermal sprayed stainless steel coating exhibits diffusion coefficient near that of ferritic steels. Furthermore, the coating contains significantly more reversible and irreversible trap concentrations than that of ferritic steels comprise. [ABSTRACT FROM AUTHOR]