Oxidation-involved life prediction and damage assessment under generalized creep-fatigue loading conditions based on engineering damage mechanics

The object of this paper is to develop numerical procedures for creep-fatigue-oxidation life prediction and damage assessments based on engineering damage approach, in response to high-reliability and long-life design requirement that supports low-carbon and new -energy technologies. In order to achieve the prediction results in terms of cycle -dependent stress-strain responses, crack initiation life prediction and multi-damage evolutions, the generalized creep-fatigue loading conditions including tension-hold-only, compression-hold-only and tension-compression-hold-both, which are abbreviated as CP, PC, and CC types, are conducted for IN 718 at 650 degrees C. Results show that creep-fatigue deformation behaviors are well depicted through the evolutions of hysteresis loops, cy-clic softening curves and stress responses. With incorporating into oxidation damage especially under long-life conditions, both error band and probability density function for life prediction are quantitatively improved. In addition, the cycle-dependent roles in multi -damage evolutions are clearly observed in a set of radar graphs, where fatigue, creep and oxidation damage are manifested as different evolutionary features. Finally, the technical route in the transition from deterministic to probabilistic multi-damage assessments is discussed based on the established creep-fatigue-oxidation diagram.

Automated summary

The objective of this study is to develop numerical procedures for predicting creep-fatigue-oxidation life and assessing damage based on an engineering damage approach. The study focuses on supporting low-carbon and new-energy technologies and their high-reliability and long-life design requirements. The research explores the creep-fatigue behavior of IN 718 at 650 degrees C under various loading conditions and incorporates oxidation damage into the prediction. The results show improvements in the prediction accuracy and probability density function by considering oxidation damage. The study also demonstrates the cycle-dependent roles in multi-damage evolutions through radar graphs.