Asymmetric Energy Damage Curve Approach for Fatigue Assessment of Notched Components Under Variable Amplitude Rotating Bending Loading

Accurate fatigue life prediction of notched components under variable amplitude rotating bending is complicated by the interplay of macroscopic stress gradients, localized notch plasticity, and load sequence effects. To address this, we propose an Asymmetric Energy Damage Curve Approach (AEDCA) that integrates the averaged Strain Energy Density (SED) into a nonlinear, path-dependent damage accumulation framework. Evaluated within a calibrated structural control volume, the SED unifies fatigue data of plain and notched S690 steel into a single geometry-independent master curve.

Unlike traditional energy-domain Palmgren-Miner rules, the AEDCA explicitly decouples high-to-low and low-to-high load transitions using independently calibrated interaction parameters, eliminating reliance on spectrum-specific empirical thresholds. Validated against a database of over 160 variable amplitude experiments, the AEDCA significantly outperforms linear damage rules. Monte Carlo analysis confirms the robustness of the model, demonstrating superior predictive accuracy across a 95\% plausible parameter space despite inherent calibration variability.

This framework provides a physically rigorous, mesh-insensitive solution for structural integrity assessments under complex service loads.