Masahiro Kusaka

Automobiles are highly convenient and indispensable as a means of transportation in our lives, however traffic accidents are an important issue and casualties must be significantly reduced. Technology for automobile safety is required to reduce casualties caused by traffic accidents, and impact energy absorbing members, such as a crash box and a side member, are used to protect occupants in the event of an accident. These members are required to be lightweight in order to improve running distanse and be required to absorb more impact energy. The crash box requires the ability to suppress load fluctuations, and has high strength and large deformation to improve the impact energy absorption performance. In this study, the shapes of lattice structure imitating Miura-ori, which is a kind of origami, were examined with the aim of increasing the amount of impact energy absorbed by increasing the amount of deformation. From results obtained by the impact crushing analysis, it was found that lattice structures imitating Miura-ori with appropriate strut angles and diameters have small load fluctuations and excellent impact energy absorption performance.

Researches on crash boxes for automobiles are being carried out to reduce occupant damage caused by traffic accidents. We have been studying a crash box consisting of many cells with an elliptical hole for the purpose of improving energy absorption by increasing the amount of displacement during crushing. Our previous studies have showed that the tapers on the side plane of the crash box reduces load fluctuations, however the densification comes from middle part of the crash box. In this study, models that crushed from the impact face of the crash box were examined to reduce damage to the side members connected to the crash box. In addition, by comparing the performance of a crash box model consisting of cells with a circular hole and a crash box model with an elliptical hole, it was clarified that the crash box consisting of cells with elliptical holes had a large crushing displacement and was excellent in impact energy absorption.

A stent is a tubular network that is placed inside a blood vessel to support the narrowing of the blood vessel and keeps the blood vessel in an expanded state. The stent needs to have high extension rate since the stent is attached to the tip of the catheter and is carried through the blood vessel to the affected part. Our propose of this study is to develop a stent that can be expanded in the radial and longitudinal directions. We created a stent model imitating the Namako-ori, which was a type of folding origami, and analyzed the expansion behavior of the stent using FEM analysis. From the analysis results, it was confirmed that the proposed stent model could be extended in the radial and longitudinal directions.

In recent years, space debris has been on the increase. Space debris orbits around the earth at a maximum speed of 15 km/s(1). If space debris collides with a space station, it will cause enormous damage. Therefore, countermeasures against space debris collisions are indispensable for advancing space development. The purpose of this study is to clarify how the defending performance of the bumper shield can be improved to reduce damage to the space structure. Reimerdes et al.(4) showed that it was advantages to halve the thickness and install two bumpers than to install one bumper. In this study, the defending performance of the bumper shield in which one bumper was divided into plural bumpers in the thickness direction and those bumpers were arranged was examined by using SPH analysis. In addition, the bumpers with protrusions were examined to scatter fragments of debris and bumpers. From analysis results, it was found that the defending performance of the bumper shield was improved as the number of bumpers increased. The method of scattering fragments of debris and bumpers was effective for improving the defending performance. It was also found that the defending performance of the bumper with protrusions depended on the place where debris collided with the bumper. Therefore, it is considered that bumpers with protrusions are less reliable than flat bumpers. It is necessary to consider an effective method for scattering debris.