EFFECT OF TEMPERATURE‐DEPENDENT CRACK CLOSURE AND CRACK BRIDGING ON LONG CRACK PROPAGATION AT ELEVATED AND CYCLIC TEMPERATURE DURING HIGH CYCLE FATIGUE

This study addresses a persistent problem in high-cycle fatigue life prediction, observed growth-rate scatter under nominally similar ΔK and R conditions due to extrinsic shielding that varies with temperature. The purpose is to quantify how temperature-dependent crack closure and crack bridging relate to long-crack growth and how temperature level and within-cycle thermal range moderate these effects. Using a quantitative, cross-sectional, case-based design, we assembled a harmonized multi-case dataset and a structured literature corpus, reviewing 45 peer-reviewed papers to shape measurement rubrics and model specification. The empirical sample comprises enterprise-grade component cases from aerospace and power contexts with constant-elevated and cyclic temperature histories. Key variables include log(da/dN) as outcome, fracture-mechanics covariates ΔK, R, frequency, environment, surface finish, microstructure, temperature descriptors mean T, thermal mode, ΔT for cyclic cases, and mechanism indices for closure and bridging scored on five-point scales. The analysis plan applies hierarchical multiple regression with robust errors, entering controls, then mechanism indices, then prespecified moderation terms Temperature × Closure and Temperature × Bridging, with auxiliary ΔT terms for cyclic cases; robustness includes leave-one-case-out checks and an effective-range sensitivity using ΔKeff when opening fractions are available. Headline findings show ΔK and temperature are positively associated with growth, closure and bridging are protective with closure larger in magnitude, and temperature attenuates closure’s protection, ΔT raises growth and further erodes closure under cyclic service. Implications are practical, incorporate temperature mode and mechanism ratings into inspection planning and damage-tolerance models, report ΔK alongside mechanism indices or ΔKeff, and stratify assessments by thermal regime and environment.