Theoretical prediction of the endurance limit of nano-materials

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K18675
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 18:Mechanics of materials, production engineering, design engineering, and related fields
• Research Institution: Osaka University
• Principal Investigator: Ogata Shigenobu 大阪大学, 大学院基礎工学研究科, 教授 (20273584)
• Co-Investigator(Kenkyū-buntansha): 新里 秀平 大阪大学, 大学院基礎工学研究科, 助教 (10853202)
• Project Period (FY): 2021-07-09 – 2024-03-31
• Keywords: 疲労寿命 / ナノ材料 / 変形素過程 / 理論予測 / 原子論 / 破壊 / 塑性変形

Outline of Final Research Achievements

This study targeted metal nanopillars and graphene sheets, which possess completely different bonding states;metallic bonds and covalent bonds, respectively;and exhibit different deformation capacities. By introducing initial defects into models of these materials, molecular dynamics methods were applied to analyze the time evolution of defects under cyclic loading. It was shown that the time until crack initiation decreases rapidly with increases in temperature and stress amplitude for both materials, indicating that treating the fundamental processes of fatigue as thermally activated processes is appropriate regardless of the bonding style. The process leading to fracture (or significant plastic deformation) under repeated loading involves multiple stages of thermal activation. Therefore, a theoretical prediction formula considering multi-stage thermal activation processes was constructed, compared with molecular dynamics analysis results, and its validity was demonstrated.

Free Research Field

機械材料、計算材料科学、計算材料力学

Academic Significance and Societal Importance of the Research Achievements

ナノデバイスは至る所で使用されている。それらは、使用温度の変化や外部からの力学的な振動などで繰り返し負荷を受けている。このような環境下にあるナノ材料が、いつ破壊するのかを実験以前に予測することは産業界においても重要なテーマである。しかしながら、これまでナノ材料の疲労研究はほとんど行われていない。本研究では、ナノ材料の疲労寿命を予測評価できる物理理論を構築し、その妥当性を確認することができた。この成果はナノ材料疲労の研究分野を大きく切り開くものであると考える。