The Hong Kong Polytechnic University, Shenzhen Research Institute, Shenzhen 518057, PR China; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
The Hong Kong Polytechnic University, Shenzhen Research Institute, Shenzhen 518057, PR China; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
Ultrasonics. 2014 Mar;54(3):770-8. doi: 10.1016/j.ultras.2013.09.023. Epub 2013 Oct 7.
A dedicated modeling technique for comprehending nonlinear characteristics of ultrasonic waves traversing in a fatigued medium was developed, based on a retrofitted constitutive relation of the medium by considering the nonlinearities originated from material, fatigue damage, as well as the "breathing" motion of fatigue cracks. Piezoelectric wafers, for exciting and acquiring ultrasonic waves, were integrated in the model. The extracted nonlinearities were calibrated by virtue of an acoustic nonlinearity parameter. The modeling technique was validated experimentally, and the results showed satisfactory consistency in between, both revealing: the developed modeling approach is able to faithfully simulate fatigue crack-incurred nonlinearities manifested in ultrasonic waves; a cumulative growth of the acoustic nonlinearity parameter with increasing wave propagation distance exists; such a parameter acquired via a sensing path is nonlinearly related to the offset distance from the fatigue crack to that sensing path; and neither the incidence angle of the probing wave nor the length of the sensing path impacts on the parameter significantly. This study has yielded a quantitative characterization strategy for fatigue cracks using embeddable piezoelectric sensor networks, facilitating deployment of structural health monitoring which is capable of identifying small-scale damage at an embryo stage and surveilling its growth continuously.
开发了一种专门的建模技术，用于理解在疲劳介质中传播的超声波的非线性特性，该技术基于通过考虑源自材料、疲劳损伤以及疲劳裂纹的“呼吸”运动的介质的改进本构关系。将用于激励和获取超声波的压电片集成到模型中。通过声非线性参数来校准提取的非线性。通过实验验证了该建模技术，结果显示两者之间具有令人满意的一致性，都表明：所开发的建模方法能够真实地模拟超声波中表现出的疲劳裂纹引起的非线性；随着波传播距离的增加，声非线性参数会累积增长；通过传感路径获得的这样的参数与从疲劳裂纹到该传感路径的偏移距离呈非线性关系；探测波的入射角和传感路径的长度都不会对该参数产生显著影响。这项研究使用嵌入式压电传感器网络为疲劳裂纹提供了一种定量表征策略，有助于部署结构健康监测，该监测能够识别胚胎阶段的小范围损伤，并持续监测其生长。
