Defect detection in steel materials using sensors based on fiber Bragg gratings

The possibilities of detecting defects in steel material using the fiber Bragg gratings (FBG) are presented. Measurement of sensitivity to force change is ensured by shifting the FBG. Steel samples were used for the tests: one standard sample and the others had incisions. The incisions were at right angles and sharp to the axis of the fiber. The FBG was glued to the sample along its entire length and then lengthened by force. The transmission spectrum obtained on the OSA was used to determine the processing characteristics: the main minimum on the transmission characteristics and the full width at half maximum (FWHM) depending on the force transferred. On the first characteristic, the quantity of cuts can be detected (for a larger amount of cuts the main minimum changes significantly), and on the second characteristic, both the quantity of cuts (the greater the number of cuts the FWHM change is greater) and the angle of incision relative to the fiber axis, FWHM it decreased during increasing forces in the case of a right angle, while it increased in the case of an acute angle.