Detection technique of stress waves based on fiber Bragg grating

The detecting method of stress wave generated by split Hopkinson pressure bar based on fiber Bragg grating (FBG) is proposed; the principle is outlined and the relationship between strain and center wavelength shift of FBG is discussed. The strain pulses generated by direct impact and impacting with the pulse shaper are measured using the FBG and strain gauges which are axially symmetrically pasted to the same section of the cylindrical rod. It can be concluded that the time domain signal and the frequency spectrum of the results with FBG and strain gauges are consistent by contrast and analysis. The maximum strain reaches -1087.04 με with error of 2.26% for a given impacting velocity of 11.33 m/s. When FBG and the pulse shaper are adopted, the impacting veloctiy is 9.8 m/s, and the longitudinal wave speed is measured to be 5236.4 m/s with the error of 2.84%. The error range can meet the basic requirements of engineering tests.