In-Situ High Temperature and Large Strain Monitoring During a Copper Casting Process Based on Regenerated Fiber Bragg Grating Sensors

Abstract

In-situ temperature and strain during copper casting process were monitored for the first time based on regenerated fiber Bragg grating (RFBG) sensors, with the maximum temperature up to 1100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C and the largest compressive strain approximately −14 000 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> . A generalized fifth-order polynomial calibration function was used to convert the measured Bragg wavelengths from RFBG into temperature values. With an RFBG temperature sensor array, the temperature distribution as a function of time was obtained, revealing how the temperature gradient changed during the casting process. In-situ strain was measured by an RFBG strain sensor in direct contact with copper, showing the strain progression inside the copper at different temperatures during the casting. The RFBG-based in-situ monitoring method provides a new way for measuring multiple parameters in high temperature casting, which can be used for improving the design of the casting mold and upgrading the casting quality. Furthermore, our investigation lays a good foundation for fiber-embedded smart metal structures as it shows that fiber sensors can be embedded in copper casts without special surface treatment.