Identifying fabrication defects of metal packaged fibre Bragg grating sensors for smart pre-stressing strands

Abstract

Metal packaged fibre Bragg grating sensors have the potential to provide reliable measurements of temperature and strain in high stress environments for the purpose of structural health monitoring. However due to the induction brazing fabrication process a small percentage of sensors are found to have defective brazed joints. We demonstrate a defect identification procedure derived from the batch temperature calibration of fibre Bragg grating sensors for temperature and strain measurement, allowing defective sensors to be identified before installation. The procedure was demonstrated on a sample of twelve temperature sensors fabricated for a small-scale smart pre-stressing strand validation test.