Shan Shengbo, Hasanian Mostafa, Cho Hwanjeong, Lissenden Cliff J, Cheng Li
Department of Engineering Science and Mechanics, Penn State, State College, PA 16802, USA; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
Department of Engineering Science and Mechanics, Penn State, State College, PA 16802, USA.
Ultrasonics. 2019 Jul;96:64-74. doi: 10.1016/j.ultras.2019.04.001. Epub 2019 Apr 11.
A nonlinear ultrasonic method is proposed based on a group of newly discovered wave triplets where two primary codirectional shear-horizontal SH0 waves mix in a weakly nonlinear plate and generate a cumulative S0 Lamb wave at the sum frequency. Theoretical analyses show that any combination of two primary SH0 waves whose frequencies sum to the frequency at which the SH0 mode intersects the S0 Lamb wave mode results in an internally resonant secondary S0 Lamb wave. Moreover, the relationship between the frequency combination and the nonlinear Lamb wave generation efficiency is revealed, which guides further engineering applications. Finite element validations are carried out with the aid of a subtraction method for the nonlinear feature extraction. The cumulative effect of the generated S0 Lamb wave at the sum frequency as well as the influence of the frequency combinations on the nonlinear Lamb wave generation efficiency is confirmed. Experiments are performed to validate the proposed method as well as demonstrate its use for material characterization. The experiments require a gel filter to mitigate the influence of the undesired nonlinear sources. With the gel filter, the cumulative effect of the secondary S0 Lamb wave is verified and the corresponding slope is extracted and further used to characterize the material status of the fatigue samples. Results demonstrate the proposed method provides high sensitivity to early fatigue damage, which makes it promising for the further early damage detection applications.
基于一组新发现的波三重态提出了一种非线性超声方法，其中两个同向的主水平剪切波SH0在弱非线性板中混合，并在和频处产生一个累积的S0兰姆波。理论分析表明，频率之和等于SH0模式与S0兰姆波模式相交频率的任意两个主SH0波的组合都会产生内部共振的次级S0兰姆波。此外，揭示了频率组合与非线性兰姆波产生效率之间的关系，这为进一步的工程应用提供了指导。借助减法方法进行有限元验证以提取非线性特征。确认了在和频处产生的S0兰姆波的累积效应以及频率组合对非线性兰姆波产生效率的影响。进行实验以验证所提出的方法，并展示其在材料表征中的应用。实验需要一个凝胶滤波器来减轻不期望的非线性源的影响。使用凝胶滤波器，验证了次级S0兰姆波的累积效应，并提取了相应的斜率，进一步用于表征疲劳样品的材料状态。结果表明，所提出的方法对早期疲劳损伤具有高灵敏度，这使其在进一步的早期损伤检测应用中具有前景。
