PRESS (Passive RFID Embedded Stress Sensor)

Critical hardware located on Naval aviation helicopters undergo regular torque checks are performed based on number of days between maintenance cycles and flight hours. It is imperative this hardware is correctly torqued to provide the right preload necessary to a bolted joint, preventing unwanted vibrations, slipping, and further loosening of the hardware. The majority of the critical hardware most frequently checked is located in the rotor, engine, and driveline of the helicopter. Current methods for performing these torque checks involves using a torque wrench, however some hardware requires multiple other components to be removed to get the wrench in place increasing time to do the task, or required an extension and/or universal socket joint, which reduces the accuracy of the set torqued value. Both methods of completing the torque check process burns a significant amount of time and resources. In the Phase I effort of this project, Lynntech will develop the PRESS (Passive RFID Embedded Stress Sensor) system. The PRESS system will be in the formfactor of a washer and replace the washers which are currently used. PRESS will have an embedded strain sensor which will be based on the axial force applied when torqueing the bolt. The value measured by the strain sensor can be converted into stress, which will then indicate the preload value experienced by the bolted joint. The preload valve can also be calculated into a torque value to ensure the hardware is within the original equipment manufacturer’s (OEM) specification. PRESS will have an integrated passive RFID tag which will communicate with an RFID reader when it is placed within range. The RFID reader will provide enough power for both the sensor portion and the RFID portion of PRESS.