Prediction of low-cycle fatigue life of eccentric holes in disk based on a three-parameter critical distance model

To enhance the fatigue life assessment accuracy for critical regions of aero-engine turbine disks and support high-reliability, long-life disk design, the challenge of accurate low-cycle fatigue (LCF) life prediction for disk eccentric bore structures was addressed. An innovative three-parameter critical distance (TCD) model was proposed to overcome the limitations of traditional TCD models, which suffered from restricted fitting accuracy due to the complex relationship between stress gradients and fatigue life. The core innovations lied in: introducing normalized maximum stress gradient and high-stress zone dimensions to characterize stress gradient effects, establishing the three-parameter critical distance expression; revealing a strong correlation between stress gradients and critical distance, and validating through notch specimen LCF tests demonstrating differential evolution of critical distance with life under contrasting high and low stress gradients; establishing a comprehensive life assessment framework integrating elastoplastic finite element simulation with the Smith-Watson-Topper fatigue life model, enabling direct critical distance calculation and accurate life prediction. Validation via LCF testing on simulated disk eccentric bore specimens demonstrated that the proposed model significantly reduced life prediction error, bringing results from outside the triple error dispersion band of traditional methods to within a 1.5-fold dispersion band. A substantial improvement in prediction accuracy for life-critical regions with stress concentrations was achieved, directly supporting the aero-engine turbine disk strength design, safety margin optimization, and life extension decision-making, and underscoring its significant practical engineering value.