Eiichi Sato

Single crystal Cu–Al–Mn shape memory alloy fabricated by abnormal grain growth is a strong candidate for actuators of heat switches that can adjust the heat flow to control the temperature inside a spacecraft appropriately. In this study, we proposed a suitable thermomechanical treatment of Cu–16.9Al–11.4Mn (mol%) alloy to stabilize its single–crystal orientation within the desired orientation region, i.e. RD//<510>, through forming texture before single crystallization heat treatment. Strong texture of the desired orientation was formed after rolling and annealing at 740°C 1 h of needle–like α+β duplex microstructure derived from Bainite microstructure. The texture became stronger when the above treatment was repeated twice. After forming a texture, single crystallization was achieved by oscillating the temperature between 740°C and 500°C five times and final annealing of 900°C 1 h. Finally, single crystals of the desired orientation were obtained with a probability of 80%. Repeated tensile tests on the obtained single crystals showed a good superelastic properties with superelastic strain of 7%.

By utilizing the shape memory effect and superelasticity of shape memory alloys, it is expected that temperature control of spacecraft and vibration isolation inside rockets can be realized with compact and lightweight devices. Recently, copper–based shape memory alloys have attracted attention because of their lower stress and temperature hysteresis and larger amount of shape recoverable strain than Ni–Ti alloys. In particular, new uses of shape memory alloys that utilize bending deformation of plate materials are being investigated, and it is expected that both large displacement and generated force can be achieved with a small material. On the other hand, bending deformation involves local stress concentration and complex deformation behavior, making device design difficult. In this study, we analytically propose a method to control the shape of the bending load–displacement curve, which is an important guideline for device design, by non–uniform changes in plate geometry using finite element analysis. The plate width was varied non–uniformly so that the bending stress distribution was uniform across the plate, thereby relieving stress concentration and reducing the maximum stress. In addition, the shape of the load–displacement curve could be changed from the conventional complicated behavior in which load decrease and increase are mixed as displacement increases, to a behavior that shows only load increase from the initial stage of deformation.

<p>SLIM (Smart Lander for Investigating Moon) is the Lunar Landing Demonstrator which is under development at ISAS/JAXA. SLIM demonstrates not only so-called Pin-Point Landing Technique to the lunar surface, but also demonstrates the design to make the explorer small and lightweight. Realizing the compact explorer is one of the key points to achieve the frequent lunar and planetary explorations. This paper summarizes the preliminary system design of SLIM, especially the way to reduce the size.</p>

<p>Ceramic/metal brazing was investigated to produce light-weight and highly-efficient ceramic thrusters. Silicon nitride ceramic and metal bars were brazed using an Ag-based brazing material. Four-point bend tests were conducted at room and high temperatures to evaluate the strength of the brazed joints. Computational fluid dynamics (CFD) and finite element method (FEM) analyses were also performed to investigate the effect of the construction and shape of the joints on the stress distribution around them. It was demonstrated that brazing was a great candidate as the joining technique, and a 20 N ceramics/metal brazed thruster was successfully produced.</p>