Accuracy Improvement of Residual Stress Measurement by Chirp Compensation of FBG

A chirp compensation method of fiber Bragg grating (FBG) is proposed to improve the residual stress measurement accuracy in the hole-drilling method. The effects of the radii of the hole, the distance between the FBG and the hole, the Young's modulus of the material, and the residual stress on the FBG chirped spectra are analyzed. The relationship between radii of the hole, the distance between the FBG and the hole, the full-width at half maximum (FWHM), and the peak wavelength are established. The feasibility of the method is verified through experiments, which shows that the residual stress measurement error can be reduced by the compensation method.

I. Introduction

Residual stress in a structural material or component is the stress that exists in the object without (and usually prior to) applying any service or other external loads. The engineering properties of materials and structural components, notably fatigue life, distortion, dimensional stability, corrosion resistance, and brittle fracture, can be considerably influenced by residual stress [1], [2]. Therefore, it is necessary to measure residual stress.