Analysis of the nonlinear reverberation of titanium alloys fatigued at high amplitude ultrasonic vibration

Abstract

The strong amplitude dependence of material parameters of microinhomogeneous materials can be used to link observations of nonlinearity to micro-scale damage. We have measured the amplitude dependence of the resonance frequency and damping characteristics in the reverberation field of the fundamental eigenmode of titanium alloy samples at regular instances during dynamic fatigue loading at high strains. The analysis of the reverberation is performed in the frequency domain using classical time-windowed FFT, as well as in the time domain using analytical functions with iteratively optimised parameters over each time window. The results show a significant increase of the nonlinearity in the frequency and damping characteristics of the signals observed during the fatiguing process.