Fracture Behaviour of Two Creep-Resistant Materials Subjected to Cyclic Loading at Elevated Temperature

An alloy steel and a nickel-chromium alloy are shown to exhibit similar fatigue behaviour over a wide range of temperatures. Endurances tended to be time-dependent at elevated temperatures, and repeated-tension cycles were found to be more damaging than push-pull but less damaging than static-tension (creep). The behaviour was reversed at room temperature where failures tended to be cycle-dependent (number of cycles to failure independent of applied frequency) and creep loading was least damaging.Rupture data for repeated-tension tests at approximately 10 c/min were analysed by a creep technique. For a wide range of temperature, the expressions fitted the experimental points encouragingly closely and the technique appears to be a useful method of describing this type of data. Tests at room temperature having more than 104 cycles to failure were premature with respect to the analysed family of curves and this was attributed to failure occurring by a predominantly cycle-dependent mechanism. Fractures at hig...