Analysis of the performance of strain magnification using uniform rectangular cantilever beam with fiber Bragg gratings

A thorough analysis of the performance of different strain magnification structures with fiber Bragg gratings (FBG) is demonstrated in this paper. Four kinds of cantilever beams with different shapes have been designed by using a laser cutting technique. Simulation results show that the strain magnification structures of the different cantilever beams are different. There is a positive and linear correlation between the displacement of the free end of the cantilever beam and the average strain at the pasting position of the FBG. The correlation is used to calculate the displacement sensitivity and analyze the efficacy of the different strain magnification structures. Sensitivity enhancement factors (compared to a reference beam) of 2.67, 2.14 and 2.57 were measured experimentally for the different beam shapes studied, while the theoretical prediction factors were 2.67, 2.24 and 2.55, respectively. There is a reasonable agreement between simulation and experiment, which shows that the efficacy is related to the increasing rate of the average strain over the FBG length. The proposed method can be used to enhance the sensitivity of the FBG sensor and further improve the sensor structure design.