SBIR Phase II: Microminiature, High Resolution, Passive Peak Strain Detector for Smart Structures and Materials

该小型企业创新研究(SBIR)二期项目将能够检测峰值应变(PD)的密封封装的差动可变磁阻传感器(DVRT)与形状记忆合金(SMA)致动器相结合，以生产改进的无源PD。这些探测器可以承受恶劣的环境条件，例如潮湿、盐、振动，并且可以重新设置以供重复使用。智能结构中的传感器通常需要系统电源才能运行，但停电可能会导致关键数据丢失。因此，在智能结构中需要能够在没有电力的情况下，即被动地记录峰值信息的传感器。早期的被动PD依赖于测量相变诱发塑性(TRIP)钢的磁性能。然而，由于材料屈服，这些器件存在体积大、分辨率低、高度非线性以及一次性使用的限制。这项技术通过使用改良的微型DVRT-PD来解决这些问题。第一阶段成功地设计、制造和测试了密封包，并成功地使用了SMA来重置设备。研究了利用射频识别标签进行远程询问的技术，设计和制造了微功率样机，并演示了向形状记忆合金执行器无线输送能量的方法。在第二阶段，高度集成的微电子产品将与密封的DVRT-PD封装相结合，以生产自给自足、远程查询和远程可重置的PD。新型微功率传感器激励电路，能够进行远程询问，将被建造、测试和封装，用于独立的实验室评估和最终的现场部署。现场测试将包括对结构接缝、维修和包括桥梁在内的民用结构的支撑构件进行健康监测。DVRT-PD与这些结构的物理连接将以可靠性、低成本和易用性为设计目标。应用包括复合材料结构、飞机、火车、桥梁、大坝和建筑物的健康监测。这些系统的军事和商业市场非常重要。健康监测有可能提高军事、航空航天和民用结构的安全性和寿命。配备了峰值位移或应变测量设备的无源网络的传感器结构可以被询问它们对测试载荷或潜在破坏性事件的反应，并更换或重新设置嵌入的传感器以供未来询问。关键的民用和军用结构需要“智能”传感器来报告它们的应变历史；这有助于确保在暴露于潜在破坏性载荷后的安全运行，例如地震、飓风、军事战斗等。

This Small Business Innovation Research (SBIR) Phase II project combines hermetically packaged, differential variable reluctance transducers (DVRT) capable of peak strain detection (PD) with shape memory alloy (SMA) actuators to produce improved passive PDs. These detectors can withstand harsh environmental conditions, e.g., moisture, salt, vibration, and can be reset for repeated uses. Sensors in smart structures generally require system power in order to operate, but power outages may result in loss of key data. Therefore, sensors that can record peak information without power, i.e., passively, are needed in smart structures. Earlier passive PDs have relied on measuring the magnetic properties of transformation induced plasticity (TRIP) steels. However, these devices suffer from bulky size, low resolution, high nonlinearity, and a one time use limitation due to material yielding. This technology addresses these problems by using modified, microminiature DVRT-PDs. Phase I successfully designed, built, and tested hermetic packages, and SMAs were successfully employed for resetting of the devices. Techniques for remote interrogation using radio frequency identity tags were investigated, micropower prototypes were designed and built, and methods for wireless delivery of power to the SMA actuator were demonstrated. In Phase II, highly integrated microelectronics will be combined with the hermetic DVRT-PD packages to produce self-contained, remotely queried and remotely resettable PDs. Novel micropower sensor excitation circuits, capable of long range interrogation, will be built, tested, and packaged for independent laboratory evaluation and eventual field deployment. Field tests will include health monitoring of structural joints, repairs, and supporting members of civil structures, including bridges. The physical attachment of the DVRT-PDs to these structures will be designed for reliability, low cost, and ease of use. Applications include health monitoring of composite structures, aircraft, trains, bridges, dams, and buildings. Military and commercial markets for these systems are significant. Health monitoring has the potential to enhance the safety and life of military, aerospace, and civil structures. Sensate structures equipped with passive networks of peak displacement or strain measurement devices could be interrogated for their response to test loads or potentially damaging events, and either replaced or their embedded sensors reset for future interrogation. Critical civil and military structures require 'smart' sensors in order to report their strain histories; this can help to insure safe operation after exposure to potentially damaging loads, e.g., earthquakes, hurricanes, military combat, etc.