Investigation of thickness effects on fatigue crack propagation in freestanding single crystalline copper nano-films by in situ nanoscopic observation

2015 Fiscal Year Final Research Report

• Project/Area Number: 26889038
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Materials/Mechanics of materials
• Research Institution: Osaka University
• Principal Investigator: Kondo Toshiyuki 大阪大学, 工学(系)研究科(研究院), 助教 (70735042)
• Project Period (FY): 2014-08-29 – 2016-03-31
• Keywords: 材料強度学 / 薄膜 / 疲労 / き裂進展

Outline of Final Research Achievements

To investigate the thickness effects on fatigue crack propagation in submicron-thick freestanding metallic films, fatigue crack propagation experiments and nanoscopic observation of fatigue damage formation at the crack tip were conducted in single-crystalline copper (Cu) films with two various film thicknesses. In roughly 600 nm-thick Cu films, intrusions/extrusions were formed ahead of the crack tip, and the fatigue crack stably propagated. In contrast, in roughly 300 nm-thick films, the fatigue crack propagated by repeating retardation of crack propagation and slip line formation ahead of the crack tip, and subsequent rapid crack propagation along the slip line. Specific fatigue damage or intrusions/extrusions were not formed near the fatigue crack, and moreover the range of fatigue damage formation around the fatigue crack was localized. These results suggest the presence of the thickness effects on fatigue crack propagation in submicron-thick metallic films.

Free Research Field

機械材料・材料力学