Dynamic large strain measurement under high-temperature environment using a modified FBG sensor and plasma surface treatment

Large strain measurement under high-temperature environment has been a hot but difficult research issue in the fields of measurement and metrology. However, conventional resistive strain gauges are susceptible to electromagnetic interference at high temperature, and typical fiber sensors will be invalid under high-temperature environment or fall off under large strain conditions. In this paper, aiming to achieve effective and precision measurement of large strain under high-temperature environment, a systematic scheme combining a well-designed encapsulation of a fiber Bragg grating (FBG) sensor and a special surface treatment method using plasma is presented. The encapsulation protects the sensor from damage while achieving partial thermal isolation and avoiding shear stress and creep, resulting in higher accuracy. And the plasma surface treatment provides a new bonding solution which can greatly improve the bonding strength and coupling efficiency without damaging the surface structure of the object under test. Suitable adhesive and temperature compensation method are also carefully analyzed. Consequently, large strain measurement up to 1500 µɛ under high-temperature (1000°C) environment is experimentally achieved in a cost-effective way.