Evaluation of Degradation Behavior of SMA Thin Wire Microactuater under Low Hydrogen Concentration

2015 Fiscal Year Final Research Report

• Project/Area Number: 25420015
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Materials/Mechanics of materials
• Research Institution: Kobe University
• Principal Investigator: TANAKA Hiroshi 神戸大学, 工学(系)研究科(研究院), 准教授 (80236629)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 環境強度 / 形状記憶合金 / 水素環境 / 疲労 / マイクロアクチュエータ

Outline of Final Research Achievements

The effect of hydrogen environment on strength and fatigue life of thin wires of TiNi shape memory alloys were investigated. In all kinds of hydrogen environment, the fatigue life was clearly shorter than that in air, but there is little difference in the fatigue life between those hydrogen environments. A fatigue limit exists in air and in pure water but not in NaOHaq.
The time to failure of fatigue tests under high hydrogen concentration showed good agreement with those of constant stress tests and SSRT at maximum stress below 300 MPa, while a large difference in the time to failure could be seen at high maximum stress. For low hydrogen concentration, there was a large difference in the time to failure of fatigue tests, constant stress tests and SSRT at any maximum stress. Therefore, the life of TiNi thin wires under low maximum stress and strong hydrogen environment is controlled by hydrogen embrittlement, but cyclic stress affects the life under other fatigue conditions.

Free Research Field

機械材料・材料力学