Analytical and experimental study on noncontact sensing with embedded fiber-optic sensors in rotating metal parts

Layered manufacturing can build functional metal parts with fiber-optic sensors placed within the structure and fully embedded. These sensors can be used to gain data for validating or improving designs during the prototype stage or to obtain information on the performance and structural integrity of functional components in service in hostile environment. This paper presents a new technique for noncontact thermal strain measurement in rotating metal components with embedded fiber Bragg grating sensors. Two different tunable laser diodes were incorporated into the sensing system to monitor the Bragg grating wavelength shifts, and thus the thermal strain can be determined. Experimental results validate the feasibility of this technique. The noncontact sensing system could provide a useful sensing tool to optimize the design for turbine blades and other rotary metal tooling, especially those exposed to hostile environments.