Nonlinear ultrasonics for in situ damage detection during high frequency fatigue

Abstract

In this paper, we report the use of the feedback signal of an ultrasonic fatigue system to dynamically deduce fatigue damage accumulation via changes in the nonlinear ultrasonic parameter. The applicability of this parameter in comparison to the resonant frequency for assessment of fatigue damage accumulation in a wrought aluminum alloy has been demonstrated, without the need for coupling fluids or independent generation of incident ultrasonic waves. The ultrasonic nonlinearity increased and the resonant frequency of the system decreased with initiation and propagation of the major crack. The nonlinear ultrasonic parameter shows greater sensitivity to damage accumulation than the resonant frequency. The number of cycles for crack propagation, estimated based on the changes in the nonlinear ultrasonic parameter, is in very good agreement with calculated crack growth rates based on the fractography studies.

A novel method for extracting acoustic nonlinearity parameters with diffraction corrections

“…(18), the average fundamental pressure at a propagation distance z is dependent on the source pressure amplitude 0 p , the source diameter a, and the receiver diameter b, as well as the attenuation coefficient 1 a (a material parameter) and the diffraction correction. The average second harmonic pressure is more complicated and additionally depends on the material parameters b and 2 a , as well as the diffraction correction, as seen in Eq.…”

“…Eq. (13) is also an exact solution to the second harmonic wave equation in the quasi-linear theory since the exact linear solution 1 p is used in the right hand-side of Eq. (13) to calculate an additional pressure perturbation due to nonlinearity.…”

“…For solids, acoustic nonlinearity has been used to characterize material damage and microstructural changes [1][2][3]. For fluids, studies of acoustic nonlinearity are mainly focused on harmonic imaging of biological tissues [4,5].…”

An Efficient and Accurate Method for Calculating Nonlinear Diffraction Beam Fields

“…The acoustic nonlinearity parameter is one of the quantitative indicators that is known to be more sensitive to certain damages and material states than traditional linear parameters such as velocity, attenuation. For solids, acoustic nonlinearity has been used to characterize material damage and microstructural changes [1][2][3]. For fluids, studies of acoustic nonlinearity were mainly focused to harmonic imaging of biological tissues [4,5].…”

VHCF of spray formed hypereutectic aluminium silicon alloy

“…Additionally, means of non-linear acoustics are employed in computer control and data acquisition for monitoring and analysis of the specimens' vibration properties in CA experiments [2]. The method allows deriving the resonance frequency as well as the non-linearity parameter rel , which may serve for early detection of fatigue damage [3]. Changes in resonance frequency and non-linearity parameter rel are indicators for microstructural changes and are used to monitor progress of fatigue damage in the VHCF regime.…”