Law of fracture life under creep–fatigue interactive conditions for Ni-base directionally solidified superalloy based on non-equilibrium science (the effect of stress holding time)

Issue title: Memorial Issue of Prof. Dr Bilal Dogan

Guest editors: A. Saxena, K. Nikbin and A.T. Yokobori Jr.

Article type: Research Article

Authors: Ozeki, Go^{; *} | Yokobori Jr., A. Toshimitsu | Sugiura, Ryuji | Ito, Michifumi

Affiliations: Graduate School of Engineering, Tohoku University, Sendai, Japan

Correspondence: [*] Address for correspondence: G. Ozeki, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. E-mail: ozeki@md.mech.tohoku.ac.jp.

Abstract: Ni-base directionally solidified superalloy are used under complex conditions of high temperature creep and fatigue interaction. Under these conditions, the characteristics of load frequency for fracture life show a nonlinear behavior, and these characteristics show various features depending on material, temperature and stress holding time. In this study, crack growth tests were conducted under creep–fatigue interactive conditions with stress holding time, tH using the in-situ observational system for directionally solidified Ni-base superalloy CM247LC. To characterize the load frequency of fracture life for CM247LC, the separate estimation of cyclic dependent from time dependent mechanisms was conducted. Additionally, a developed representation of the characteristic of fracture life under the conditions of creep fatigue interaction based on non-equilibrium science and chaos theory was proposed. Furthermore, verification of the established law of predicting the fracture life under creep–fatigue interactive conditions was conducted.

Keywords: Ni-base directionally solidified superalloy, fracture life, non-equilibrium science, creep–fatigue interactive condition

DOI: 10.3233/SFC-150183

Journal: Strength, Fracture and Complexity, vol. 9, no. 1, pp. 111-123, 2015