Impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering. Estimation of hydrodynamic impact forces especially during the first instances af...Impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering. Estimation of hydrodynamic impact forces especially during the first instances after the impact is very important and is of interest. Since the estimation of hydrodynamic impact load plays an important role in safe design and also in evaluation of structural weight and costs, it is better to use a reliable and accurate prediction method instead of a simple estimation resulted by analyzing methods. In landing of flying boats, some phenomena such as weather conditions and strong winds can cause asymmetric instead of symmetric descent. In this paper, a numerical simulation of the asymmetric impact of a wedge, as the step of a flying boat, considering dynamic equations in two-phase flow is taken into account. The dynamic motion of the wedge in two-phase flow is solved based on finite volume method with volume of fluid （VOF） scheme considering dynamic equations. Then the effects of different angles of impact and water depth on the velocity change and slamming forces in an asymmetric impact are investigated. The comparison between the simulation results and experimental data verifies the accuracy of the method applied in the present study.展开更多
Layer manufacture technologies are gaining increasing attention in the manufacturing for the production of polymer mould tooling. Layer manufacture techniques can be used in this potential manufacturing area to produc...Layer manufacture technologies are gaining increasing attention in the manufacturing for the production of polymer mould tooling. Layer manufacture techniques can be used in this potential manufacturing area to produce tooling either indirectly or directly, and powder metal based layer manufacture systems are considered as an effective way of producing rapid tooling. Mechanical properties and accuracy are critical for tooling. This paper reports the results of an experimental study examining the potential of layer manufacturing processes to deliver production tooling for polymer manufacture. A comparison between indirectly selective laser sintering and directly selective laser sintering to provide the tooling was reported. Three main areas were addressed during the study： mechanical strength, accuracy, and build rate. Overviews of the results from the studies were presented.展开更多
文摘Impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering. Estimation of hydrodynamic impact forces especially during the first instances after the impact is very important and is of interest. Since the estimation of hydrodynamic impact load plays an important role in safe design and also in evaluation of structural weight and costs, it is better to use a reliable and accurate prediction method instead of a simple estimation resulted by analyzing methods. In landing of flying boats, some phenomena such as weather conditions and strong winds can cause asymmetric instead of symmetric descent. In this paper, a numerical simulation of the asymmetric impact of a wedge, as the step of a flying boat, considering dynamic equations in two-phase flow is taken into account. The dynamic motion of the wedge in two-phase flow is solved based on finite volume method with volume of fluid （VOF） scheme considering dynamic equations. Then the effects of different angles of impact and water depth on the velocity change and slamming forces in an asymmetric impact are investigated. The comparison between the simulation results and experimental data verifies the accuracy of the method applied in the present study.
文摘Layer manufacture technologies are gaining increasing attention in the manufacturing for the production of polymer mould tooling. Layer manufacture techniques can be used in this potential manufacturing area to produce tooling either indirectly or directly, and powder metal based layer manufacture systems are considered as an effective way of producing rapid tooling. Mechanical properties and accuracy are critical for tooling. This paper reports the results of an experimental study examining the potential of layer manufacturing processes to deliver production tooling for polymer manufacture. A comparison between indirectly selective laser sintering and directly selective laser sintering to provide the tooling was reported. Three main areas were addressed during the study： mechanical strength, accuracy, and build rate. Overviews of the results from the studies were presented.
