Wireless stress measurement on metal surface based on passive integrated RFID sensor tag

Due to the long-term harsh working environment and cyclic loadings, deformations and cracks will occur on the large metal structures. Therefore, long-term detection of metal surface stress is essential to ensure the operation safety of large metal facilities. Compared with traditional nondestructive testing (NDT) technology, Radio Frequency Identification (RFID) sensor tag is more appropriate structural health monitoring (SHM) because of passivity and wireless. To improve the accuracy and detection repeatability of RFID in stress measurement, an integrated RFID sensor tag is designed to measure metal surface stress by experiment. An integrated RFID tag has microcontroller that converts sensor information as digital signals. The experimental results indicate that the relative measurement error of the proposed integrated RFID sensor tag is lower than other RFID sensor tags, and the absolute error is less than $\pm 26\ \mu\varepsilon$ . When the strain of the specimen is greater than $450\ \mu\varepsilon$ , the relative error is less than 2.5%. Besides, four repeat experiments illustrate that the proposed RFID stress measurement system has excellent detection repeatability, meanwhile the integrated RFID sensor tag shows excellent performance in measuring the micro-stress of metal structures, such as gearings, axles, and bearings.