Monitoring of Thermal Aging of Aluminum Alloy via Nonlinear Propagation of Acoustic Pulses Generated and Detected by Lasers

Abstract

Nonlinear acoustic techniques are established tools for the characterization of micro-inhomogeneous materials with higher sensitivity, compared to linear ultrasonic techniques. In particular, the evaluation of material elastic quadratic nonlinearity via the detection of the second harmonic generation by acoustic waves is known to provide an assessment of the state variation of heat treated micro-structured materials. We report on the first application for non-destructive diagnostics of material thermal aging of finite-amplitude longitudinal acoustic pulses generated and detected by lasers. Finite-amplitude longitudinal pulses were launched in aluminum alloy samples by deposited liquid-suspended carbon particles layer irradiated by a nanosecond laser source. An out-of-plane displacement at the epicenter of the opposite sample surface was measured by an interferometer. This laser ultrasonic technique provided an opportunity to study the propagation in aluminum alloys of finite-amplitude acoustic pulses with a strain up to 5 × 10−3. The experiments revealed a signature of the hysteretic quadratic nonlinearity of micro-structured material manifested in an increase of the duration of detected acoustic pulses with an increase of their amplitude. The parameter of the hysteretic quadratic nonlinearity of the aluminum alloy (Al6061) was found to be of the order of 100 and to exhibit more than 50% variations in the process of the alloy thermal aging. By comparing the measured parameter of the hysteretic quadratic nonlinearity in aluminum alloys that were subjected to heat-treatment at 220 °C for different times (0 min, 20 min, 40 min, 1 h, 2 h, 10 h, 100 h, and 1000 h), with measurements of yield strength in same samples, it was established that the extrema in the dependence of the hysteretic nonlinearity and of the yield strength of this alloy on heat treatment time are correlated. This experimental observation provides the background for future research with the application goal of suggested nonlinear laser ultrasonic techniques for non-destructive evaluation of alloys’ strength and rigidity in the process of their heat treatment.

Special Issue on Laser Ultrasonics

“…Zhan et al [5] describe the application of laser ultrasonic inspection to deformation and cracking caused by residual stress with application in laser welding technology. Li et al [6] report the first application of nonlinear longitudinal acoustic pulses generated and detected by lasers for nondestructive diagnostics of material thermal aging. Glushkov et al [7] applied the transient grating method to study the behavior of surface acoustic waves in nanowire-based composite structures.…”

Propagation of Non-Linear Lamb Waves in Adhesive Joint with Micro-Cracks Distributing Randomly

“…In recent years, the non-linear ultrasonic technique has received attention for the reason that it is highly sensitive to material micro-structures whose dimensions are much smaller than the wavelength of an ultrasonic wave [7][8][9][10][11][12]. Li et al [13,14] conducted studies on monitoring the thermal aging of aluminum alloy and detecting the delamination of lined anti-corrosion pipes using non-linear acoustics, which demonstrate the sensitivity of the non-linear ultrasonic technique to the damage. Compared with the linear ultrasonic technique, it is becoming a quite promising tool in the nondestructive characterization of the degrees of damages which are related to the micro-cracks [15][16][17][18].…”

Exploiting Slow Dynamics Effects for Damage Detection in Concrete

“…Several techniques for damage detection and localization have thus been developed based on the dynamics of the propagating wave to extract a nonlinear signature of the sample. Applications are reported for metals (Ohara et al, 2012;Hong et al, 2018;Li et al, 2019), composites (Amura and Meo, 2012;Genoves et al, 2015), rocks (Riviere et al, 2015), biological samples (Ulrich, 2007), etc. Damage related nonlinear elastic properties of materials of interest in civil engineering have also been widely studied: thermal induced damage (Payan et al, 2007;Scalerandi et al, 2013), corrosion cracks (Antonaci et al, 2013;Boukari et al, 2015), effects of carbonation (Bouchaala et al, 2011), or of static loads either external or shrinkage induced (Antonaci et al, 2010a,b;Kim et al, 2017), etc.…”