Abstract
AbstractTo clarify vacuum effects on fatigue crack growth in freestanding metallic thin films, experiments were conducted on approximately 500‐nm‐thick copper films inside a field emission scanning electron microscope. Fatigue crack growth accompanied by intrusion/extrusion formation occurred in vacuum, and da/dN was smaller than in air in the middle‐ΔK region (ΔK ≈ 1.7‐3.1 MPam1/2). Conversely, in the low‐ΔK region (ΔK ≲ 1.7 MPam1/2), da/dN was larger in vacuum than in air. Further, fatigue crack growth in vacuum occurred below the fatigue threshold in air (ΔKth,air). A nonpropagating crack after reaching ΔKth,air continued to propagate in vacuum when the environment changed from air to vacuum. This indicates that fatigue crack growth resistance is smaller in vacuum than in air under the same effective driving force. The fatigue damage area near the crack paths in vacuum in the low‐ΔK region became wider, suggesting that the nucleation of fatigue damage was enhanced in vacuum.
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