A Novel Acoustoelastic-Based Technique for Stress Measurement in Structural Components

Abstract

The acoustoelastic theory has been widely utilized for nondestructive stress measurement in structural components. Most of the currently available techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves, and rely on time-of-flight measurements to quantify the effects of stress state on wave speed. This adversely affects the sensitivity and accuracy of such techniques, and renders their accuracy limited by the precision within which time-of-flight can be determined.

In this work, a novel acoustoelastic-based stress measurement technique is developed by combining dispersion compensation algorithms and numerical optimization schemes. Dispersion compensation allows the use of highly-stress-sensitive, low-frequency flexural waves for stress measurement, which in turn enhances the sensitivity of the developed technique. The need for accurate time-of-flight measurements is eliminated in this work by analyzing the entire propagated waveform to reconstruct the dispersion curve over the frequency range of interest. The fact that an entire section of the dispersion curve, as opposed to a single wave speed measurement, is used to calculate the state of stress in the structure enhances the technique’s accuracy and robustness. A criterion for optimal selection of excitation waveform is developed in this work. The effects of material properties uncertainties on the accuracy of stress measurements are also investigated.