Institute of Microtechnology, Technische Universität Braunschweig, 38124 Braunschweig, Germany.
Institute for Microsensors, Actuators and Systems, University of Bremen, 28359 Bremen, Germany.
Sensors (Basel). 2022 Jul 19;22(14):5368. doi: 10.3390/s22145368.
Structural health monitoring of lightweight constructions made of composite materials can be performed using guided ultrasonic waves. If modern fiber metal laminates are used, this requires integrated sensors that can record the inner displacement oscillations caused by the propagating guided ultrasonic waves. Therefore, we developed a robust MEMS vibrometer that can be integrated while maintaining the structural and functional compliance of the laminate. This vibrometer is directly sensitive to the high-frequency displacements from structure-borne ultrasound when excited in a frequency range between its first and second eigenfrequency. The vibrometer is mostly realized by processes earlier developed for a pressure sensor but with additional femtosecond laser ablation and encapsulation. The piezoresistive transducer, made from silicon, is encapsulated between top and bottom glass lids. The eigenfrequencies are experimentally determined using an optical micro vibrometer setup. The MEMS vibrometer functionality and usability for structural health monitoring are demonstrated on a customized test rig by recording application-relevant guided ultrasonic wave packages with a central frequency of 100 kHz at a distance of 0.2 m from the exciting ultrasound transducer.
可以使用导波对复合材料制成的轻型结构进行结构健康监测。如果使用现代纤维金属层板，则需要集成传感器来记录传播的导波引起的内部位移振荡。因此，我们开发了一种坚固的 MEMS 速度计，它可以在保持层压板的结构和功能兼容性的同时进行集成。当在其第一和第二本征频率之间的频率范围内激励时，该速度计对结构声传播的高频位移直接敏感。该速度计主要通过为压力传感器开发的工艺来实现，但增加了飞秒激光烧蚀和封装。压阻换能器由硅制成，封装在顶部和底部玻璃盖之间。本征频率使用光学微振动计设置进行实验确定。在定制的测试台上，通过记录距离激励超声换能器 0.2 m 处中心频率为 100 kHz 的应用相关导超声波包，证明了 MEMS 速度计在结构健康监测中的功能和可用性。
