Prediction of Fatigue Crack Growth Life Intervals Under Multiaxial Random Vibration Using a Combined Time‐Domain and Frequency‐Domain Approach

ABSTRACT Vibration‐induced fatigue crack growth constrains damage‐tolerant design and reliability of equipment. Predicting crack growth life under vibrational conditions still faces challenges: The coupled effects of multiaxial vibration are not fully accounted for, crack tip–driving forces under vibration are not well characterized, and single‐value life predictions do not capture the stochastic variability of random multiaxial excitation. An interval‐based life prediction framework combining time‐ and frequency‐domain vibration‐fatigue analysis is proposed. A specimen enabling simultaneous Y–Z excitation is designed. Simulations are built on instantaneous crack‐tip stress intensity factor histories and consider two crack growth characterization parameters. Multiple time‐domain realizations matching the same target PSD are generated to obtain empirical life intervals. Experiments and simulations under Y, Z, and uncorrelated Y + Z excitation show that crack growth per unit time under biaxial loading exceeds the linear sum of the two uniaxial cases. Predicted lives agree with tests within 30%.