Metal Fatigue Crack Healing by DC Pulse and High Frequency Electronic Wind Control

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K18761
• 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: Waseda University
• Principal Investigator: Hosoi Atsushi 早稲田大学, 理工学術院, 教授 (60424800)
• Project Period (FY): 2022-06-30 – 2024-03-31
• Keywords: 疲労き裂治癒 / 高密度パルス電流

Outline of Final Research Achievements

The purpose of this study is to experimentally and analytically clarify the crack closure mechanism and damage recovery before crack initiation in high-density pulsed current. The fatigue crack closure mechanism in high-density pulsed currents is that the current bypassing the crack densifies at the crack tip, and compressive thermal stresses act on the crack tip. The yield stress is lowered under high temperature environment, resulting in plastic deformation, and after cooling, tensile residual stress is generated. Balanced compressive stresses act in the vicinity of the crack. Localized bending deformation and crack closure are observed. On the other hand, it was also found that the growth of the slip zone was suppressed by applying a high-density pulsed current before the crack initiation.

Free Research Field

材料力学

Academic Significance and Societal Importance of the Research Achievements

機械や構造物には寿命が存在する．金属材料の疲労破壊を遅延させる技術としては，ショットピーニングや高周波焼き入れ等の手法が挙げられてきた．しかしこれらの手法ではき裂や転位等の損傷自体を修復することはできない．根本的に疲労損傷部分を修復することでインフラの長寿命化，安全性の向上を低コストで行う技術が求められており，これらの技術は脱炭素社会や持続可能な社会の実現につながる．