微細な亀裂が実験で消え、自己修復マシンの可能性が明らかに Microscopic cracks vanish in experiments, revealing possibility of self-healing machines
2023-07-19 サンディア国立研究所(SNL)
◆Sandia国立研究所とテキサスA&M大学の研究チームが、ナノスケールでの疲労損傷の自己修復に関する発見を論文で発表しました。従来、金属の自己修復は科学的な枠組みの外にあり、金属の割れ目は広がるものと考えられていましたが、今回の発見によりその理論が覆されました。この現象は、金属の自己修復に対する新たな理解をもたらし、材料科学の先駆的な進展となる可能性があります。一方で、まだ多くの不明点もあり、製造現場で実用化されるかどうかは今後の研究が必要とされます。
＜関連情報＞
冷間溶接による疲労亀裂の自律的治癒 Autonomous healing of fatigue cracks via cold welding
Christopher M. Barr,Ta Duong,Daniel C. Bufford,Zachary Milne,Abhilash Molkeri,Nathan M. Heckman,David P. Adams,Ankit Srivastava,Khalid Hattar,Michael J. Demkowicz & Brad L. Boyce
Nature Published:19 July 2023
DOI:https://doi.org/10.1038/s41586-023-06223-0
Abstract
Fatigue in metals involves gradual failure through incremental propagation of cracks under repetitive mechanical load. In structural applications, fatigue accounts for up to 90% of in-service failure1,2. Prevention of fatigue relies on implementation of large safety factors and inefficient overdesign3. In traditional metallurgical design for fatigue resistance, microstructures are developed to either arrest or slow the progression of cracks. Crack growth is assumed to be irreversible. By contrast, in other material classes, there is a compelling alternative based on latent healing mechanisms and damage reversal4,5,6,7,8,9. Here, we report that fatigue cracks in pure metals can undergo intrinsic self-healing. We directly observe the early progression of nanoscale fatigue cracks, and as expected, the cracks advance, deflect and arrest at local microstructural barriers. However, unexpectedly, cracks were also observed to heal by a process that can be described as crack flank cold welding induced by a combination of local stress state and grain boundary migration. The premise that fatigue cracks can autonomously heal in metals through local interaction with microstructural features challenges the most fundamental theories on how engineers design and evaluate fatigue life in structural materials. We discuss the implications for fatigue in a variety of service environments.
