Fatigue Crack Growth in a Monocrystal and Its Similarity to Short-Crack Propagation in a Polycrystal of Nickel

• Published in: Metals (Basel ) Vol. 13; no. 4; p. 790
• Main Authors: Petel, Avihai, Jager, Ales, Babai, Dotan, Jopp, Juergen, Bussiba, Arie, Perl, Mordechai, Shneck, Roni Z.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.04.2023
• Subjects: Crack propagation; Fatigue; fatigue crack propagation; Fatigue cracks; Fatigue failure; Fatigue testing machines; Fracture mechanics; Grain boundaries; Grain size; Laws, regulations and rules; Materials; Metal fatigue; Nickel; Polycrystals; Propagation; Short cracks; short fatigue cracks; Single crystals; Slip; Stress intensity factors; Stress propagation; Israel; Japan
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met13040790

Short fatigue cracks in polycrystalline materials are very important from both practical and basic aspects, yet they are very difficult to observe. Therefore, it is suggested to emulate some properties of short cracks with long fatigue cracks in monocrystals. Indeed, such experiments in pure nickel crystals prove that the three peculiar properties of short fatigue cracks in polycrystalline metals are observed in long cracks in monocrystals, i.e., a lower threshold of the stress intensity factor (ΔKI)th, a higher crack propagation rate at low ΔKI regimes, and the fact that different cracks exhibit different growth behaviors. The fatigue experiments in monocrystals reveal interesting details of the slip activity at the front of fatigue cracks, including a selection rule for the active slip systems above and below the crack, the slip behavior under conditions of steep strain gradients, and the activation of a new slip system.