Abstract
This study experimentally and numerically investigated the nonlinear behavior of the resonant bulk waves generated by the two-way collinear mixing method in 5052 aluminum alloy with micro-crack damage. When the primary longitudinal and transverse waves mixed in the micro-crack damage region, numerical and experimental results both verified the generation of resonant waves if the resonant condition was satisfied. Meanwhile, we found that the acoustic nonlinearity parameter (ANP) increases monotonously with increases in micro-crack density, the size of the micro-crack region, the frequency of resonant waves and friction coefficient of micro-crack surfaces. Furthermore, the micro-crack damage in a specimen generated by low-temperature fatigue experiment was employed. It was found that the micro-crack damage region can be located by scanning the specimen based on the two-way collinear mixing method.
Highlights
Due to the influence of fatigue loading, micro-cracks can be initiated in metallic material, which extends and degrades the material’s performance
Figure 16a1,b1 show the time-domain signals of the resonant wave mixing at the position of 80 mm and 105 mm away from the transverse transducer, respectively
A two-dimensional numerical model was built to investigate the resonant wave based on the two-way collinear mixing method in the resonant condition ω L /ωT = 2κ/(κ − 1) and the validity of locating the micro-crack damage region was verified numerically and experimentally
Summary
Due to the influence of fatigue loading, micro-cracks can be initiated in metallic material, which extends and degrades the material’s performance. It is of great importance to detect and evaluate micro-crack damage in materials at an early stage to ensure the safety of engineering structures. The feasibility of nonlinear ultrasonic techniques for detecting and evaluating early material degradation has been widely demonstrated by theory, simulation and experiment. As representative nonlinear ultrasonic techniques, higher harmonics technology [3,4,5,6,7,8,9] and wave mixing technology [10,11,12] have been commonly developed. The average or equivalent material nonlinearity in wave propagation paths can be tackled by higher harmonics technology. Shui et al [13] experimentally applied second harmonics of longitudinal wave to evaluate impact fatigue damage in adhesive bonding. Herrmann et al [14]
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