Towards exploiting inelastic design for Inconel 625 under short-term cyclic loading at 600 ∘ C

Many industries rely on the Inconel 625 alloy to serve under thermomechanical operating conditions. Understanding the macroscopic cyclic inelastic behavior of this material is vital for accurate assessment of its load-carrying capacity at elevated temperatures. In this work, a uniaxial experimental program at 600 ∘ C is conducted to demonstrate designing for cyclic elastoplastic behavior (shakedown) as opposed to more restrictive first-yield, while still avoiding ratchetting or alternating plasticity. In particular, a range of cyclic stress amplitudes are imposed at non-zero mean stresses while maintaining a constant maximum stress. In addition, the effect of dynamic strain aging (DSA) on the macroscopic shakedown behavior is established under load control. The inelastic work done per cycle is used as a measure of severity of the cyclic inelastic behavior, and is evaluated by monitoring the evolution of the hysteresis loop width. It is found that when the maximum stress is constant, larger mean stress tests approach shakedown behavior. Furthermore, for the range of stress amplitudes and mean stresses considered, the cyclic elastoplastic shakedown behavior is not affected by the DSA, and only depends on the mean stress and stress amplitude.