In this study, the thermodynamic performance of a ventilated brake disc was improved by securing structural stability and verified through bench experiments. A brake disc is a braking device that decelerates a vehicle or stops it, and the disc should maintain a reliable braking force. The temperature rise on the disc surface has the greatest effect on the braking force. In recent years, many studies have been conducted on the shape of the disc in order to secure stable braking force and heat dissipation at the same time. However, as the disc surface is processed further, it becomes more difficult to have stable braking force, although the heat dissipation property is improved. Therefore, in this study, disc shapes were designed to improve heat dissipation performance while maintaining structural performance. The stress and temperature distribution were analyzed using ANSYS and optimal design of disc shapes was performed through PIAnO. In addition, to compare and verify the initial model and the optimized model, a prototype was fabricated to judge the feasibility of the optimization using a dynamometer. It can be expected that the heat dissipation performance and driving safety can be improved by using new brake discs.
The edge wave on a uniform-sloped seabed was described by the velocity-potential function by Mok and Yeh in 1999. Edge waves cannot be extended above a certain level from the still-water level, and the upper limit of the run-up of the edge waves for given conditions is found here. In this study, quantitative mass transport by the edge waves of the beach is introduced. The maximum run-up height is decided from the wave’s amplitude at shoreline, and the maximum run-up distance from the shoreline is proportional to the wavelength of the edge waves. The fluid alongshore-mass-transport profile shows that the strongest mass transport rate corresponds to the position offshoreward multiplied by 0.0362 times the wavelength, and its magnitude is 1.23 times the mass-transport rate at the shoreline. The maximum cross-sectional total mass-transport rate is 0.214 times the mass transport at the shoreline, multiplied by the wavelength for the maximum run-up condition. This study suggests that edge waves cannot be increased infinitely and that there is a maximum run-up on the coast.
The aim of this study was to design operation methods for three-stage coil gun experiments and to fabricate and compare prototypes of control systems using these methods. Two methods are proposed: (1) recognizing the position of a projectile using a photointerrupter and (2) operating a control circuit to supply power to a silicon-controlled rectifier when the projectile reaches an intended position by registering the delay time between coil gun operations. The distance between the projectile and the solenoid coil during a coil gun operation is a key design factor. For the multi-stage coil gun manufactured in this study, the discharge time must be determined according to the position of the projectile, which moves at high velocity. Therefore, the selected method should have minimal operation error and allow the circuit to be easily used according to the coil gun stage and configuration. This study compares the prototypes of coil gun discharge circuits that were fabricated based on the proposed methods by applying them to three-stage coil guns and measuring their velocities. The findings of this study could be used to suggest design methods for experimental models for coil guns with fewer stages according to the final velocity and coil gun stage to be manufactured.
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