Ren Baiyang, Lissenden Cliff J
IEEE Trans Ultrason Ferroelectr Freq Control. 2016 Jan;63(1):178-85. doi: 10.1109/TUFFC.2015.2496423. Epub 2015 Oct 30.
The characteristics of Lamb waves, which are multimodal and dispersive, provide both challenges and opportunities for structural health monitoring (SHM). Methods for nondestructive testing with Lamb waves are well established. For example, mode content can be determined by moving a sensor to different positions and then transforming the spatial-temporal data into the wavenumber-frequency domain. This mode content information is very useful because at every frequency each mode has a unique wavestructure, which is largely responsible for its sensitivity to material damage. Furthermore, mode conversion occurs when the waves interact with damage, making mode content an excellent damage detection feature. However, in SHM, the transducers are typically at fixed locations and are immovable. Here, an affixed polyvinylidene fluoride (PVDF) multielement sensor is shown to provide these same capabilities. The PVDF sensor is bonded directly to the waveguide surface, conforms to curved surfaces, has low mass, low profile, low cost, and minimal influence on passing Lamb waves. While the mode receivability is dictated by the sensor being located on the surface of the waveguide, both symmetric and antisymmetric modes can be detected and group velocities measured.
兰姆波具有多模态和频散的特性，这给结构健康监测（SHM）带来了挑战，也带来了机遇。利用兰姆波进行无损检测的方法已经很成熟。例如，可以通过将传感器移动到不同位置，然后将时空数据转换到波数-频率域来确定模态成分。这种模态成分信息非常有用，因为在每个频率下，每种模态都有独特的波形结构，这在很大程度上决定了其对材料损伤的敏感性。此外，当波与损伤相互作用时会发生模态转换，使得模态成分成为一种出色的损伤检测特征。然而，在结构健康监测中，换能器通常位于固定位置且不可移动。在此，展示了一种粘贴式聚偏二氟乙烯（PVDF）多元素传感器具有同样的功能。PVDF传感器直接粘结在波导表面，能贴合曲面，质量轻、外形低、成本低，对通过的兰姆波影响极小。虽然模态可接收性取决于传感器位于波导表面，但对称和反对称模态都能被检测到，并且可以测量群速度。
