Critical Experiments for Structural Members of Micro Image Strain Sensing Sensor Based on Smartphone and Microscope

Strain is one of the key concerns of structural health monitoring (SHM), and effective measurement of structural strain is very important for structural health condition assessment. The purpose of this paper is to investigate the application of the micro image strain sensing (MISS) sensor based on smartphone and microscope for measuring strain parameters of structural members. Firstly, metal tensile tests were performed to verify the effectiveness of the MISS sensor, and the strain results measured by the fiber Bragg grating (FBG) sensor and the MISS sensor were compared. The results showed that the mean error between the MISS and FBG sensor measured results is 7.1 με in the metal tensile test. Then, a concrete beam bending test was carried out; the mean relative error of strain values between the FBG sensor and the MISS sensor is 2.5%. Overall, the strain measurements of the MISS sensor matched well with those from the FBG sensor in each experiment. This study validates the reliability and accuracy of the MISS sensor for strain detection and the MISS sensors can play a more powerful role in SHM due to their robustness, simplicity, and low cost.