A New Perspective on Microstructure and Structural Design for Drastic Improvement of Hull Brittle Crack Propagation Arrest Performance

2020 Fiscal Year Final Research Report

• Project/Area Number: 20K20354
• Project/Area Number (Other): 18H05337 (2018-2019)
• Research Category: Grant-in-Aid for Challenging Research (Pioneering)
• Allocation Type: Multi-year Fund (2020); Single-year Grants (2018-2019)
• Review Section: Medium-sized Section 24:Aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Kawabata Tomoya 東京大学, 大学院工学系研究科(工学部), 教授 (50746815)
• Project Period (FY): 2018-06-29 – 2021-03-31
• Keywords: 脆性亀裂伝播 / 鋼 / 高靭化 / 亀裂分岐 / 表面加工 / ディンプル / 散逸エネルギー

Outline of Final Research Achievements

In this study, experimental research was conducted to pursue the feasibility of two innovative methods. As for the toughening condition by promoting crack branching, although we could not establish the technology to induce the branching artificially, we found the first data that the bifurcation speed is significantly different depending on the loading mode, which is very helpful for the artificial bifurcation generation. In addition, we proposed a new branching theory model. Regarding the dimple processing for maximizing the side ligament effect, it was experimentally shown that the crack propagation resistance increased with dimple processing.

Free Research Field

破壊力学

Academic Significance and Societal Importance of the Research Achievements

船体やエネルギー分野など高い信頼性を要求される大型溶接構造物において脆性破壊事故は絶対に避けなければならない破壊形態である。それらの発生を万が一想定した場合の脆性き裂伝播停止特性が実際に考慮されており、今後も構造物設計の要になる。大型化の著しいコンテナ船最大板厚である90~100mmは最新の圧延技術,TMCPのほぼ限界である。また高強度化についても溶接部疲労の観点から難しい。例えば目標厚を150mmと定めた場合高価なNiなどのレアメタル元素添加に頼らざるを得なくなり現状の延長線上では経済的に実現性が乏しい。これらの状況を打破できる効果的な脆性き裂伝播停止特性付与技術は産業上の大きなニーズである