Decoupled temperature and strain measurement with regenerated fiber Bragg gratings during an aluminum casting process

Abstract

An aluminum embedded fiber Bragg grating (FBG) sensor configuration for a decoupled temperature and strain measurement was proposed and demonstrated. This configuration consists of a three-point regenerated FBG (RFBG) sensor array with a distance of 8 mm in one fiber. One RFBG was in direct contact with the aluminum, whereas the other RFBGs were protected from the aluminum by a steel capillary. The RFBG in contact with the aluminum was influenced by temperature and strain, and the other RFBGs only by temperature. The casting mold used here had a second symmetric arm used for an additional temperature reference measurement with three RFBGs in one capillary. Two casting experiments with this configuration were made, and decoupled temperature and strain measurements based on one sensing fiber were demonstrated. The temperature values in the strain sensing fiber showed good agreement with the reference temperatures in the second casting arm. Thereby, it could be demonstrated that one fiber was sufficient for both temperature and strain measurement and that the temperature compensation for the strain sensor was successful. This is a significant step towards the application of smart casts.