Session: MF-02-05 Materials for Hydrogen Service (Joint with CS-02 and HT-07) - Specimen Size and Rate Effects

Paper Number: 105339

105339 - Fracture Toughness Evaluation for an Ultra-High Strength Steel in High-Pressure Hydrogen Environment I: Establishing the Testing Method for a Thin Plate 

Since the 1970s, it has been an important technological issue to improve fuel efficiency and reduce CO₂ emissions by reducing the weight of automobile bodies using high-strength steel. In recent years, ultra-high-strength steel with a tensile strength (TS) of 1.5 GPa class has come to be applied to structural members of car bodies, and it is naturally forecasted that further weight reduction will be required in the future by adopting thinner plates with higher-strength. In general, hydrogen susceptibility of steels increases with an increase in TS, especially in the strength range of TS ≥ 1.2 GPa, for which countermeasures against hydrogen embrittlement are required even when used in air. Fracture toughness is one of the important strength properties in strength design of thin-walled parts for automobiles. Although hydrogen significantly reduces the fracture toughness of high-strength steel, little information has been obtained on its fracture toughness under the influence of hydrogen. In this study, we established an optimal experimental method for evaluating the fracture toughness of steel sheets with TS of 1.7 GPa in high-pressure hydrogen gas. The fracture toughness of a middle-crack tension (MT) specimen of 1.6 mm in thickness was measured in air and 90 MPa hydrogen gas, for which the effect of hydrogen is discussed.

Presenting Author: Yuya Tanaka Fukuoka University

Presenting Author Biography: Yuya Tanaka is an assistant professor of Mechanical Engineering at Fukuoka University. His work focuses on the fatigue limit, fatigue crack-growth threshold, and fracture toughness of metallic materials.

Authors:

Yuya Tanaka Fukuoka University
Naoki Hirakawa Graduation School of Engineering, Kyushu University
Hisao Matsunaga Department of Mechanical Engineering, Kyushu University
Kaneaki Tsuzaki Research Center for Structural Materials, National Institute for Materials Science (NIMS)
Akinobu Shibata Research Center for Structural Materials, National Institute for Materials Science (NIMS)