Fatigue Life Assessment of 90° Miter Bends under Resonant Vibration Using Strain Gauge Measurements and Numerical Analysis

Miter bends exhibit significant stress concentrations at geometric discontinuities, making them prone to fatigue failure under resonant conditions. This study presents a strain-based fatigue life assessment integrating Finite Element Analysis (FEA) and experimental validation. Modal analysis was performed by conducting numerical investigation to obtain natural frequencies and mode shapes, which were used as inputs for harmonic response analysis to identify critical locations. Experimental testing was conducted on a fixed–free setup under combined dead weight and resonant excitation using strain gauges and a load cell. Crack initiation was detected through strain spikes and confirmed using Magnetic Particle Testing (MPT). Measured microstrain was converted into stress, and fatigue life was evaluated using these experimental stress amplitudes. A Basquin S–N relation, calibrated all miter specimens, shows strong agreement with harmonic-FEA life. The model demonstrated excellent predictive accuracy, explaining 99.5% of the variance in