Temperature calibration for guided wave hybrid system with FBG-based Fabry-Perot sensor

Abstract

In a guided-wave-based damage detection hybrid system which combines piezoelectric transducers (PZT) and fiber Bragg grating (FBG) sensors, changes of temperature will affect both the propagation of Lamb waves and the fiber optic (FO) sensor’s spectrum. These variations will mask the changes caused by the occurrence of damage and thus make the damage detection unreliable, if not compensated for. This paper addresses the temperature effect calibration for Lamb wave signals measured by FBG-based Fabry Perot (FP) sensors. First, the temperature effect on the sensor’s spectrum is investigated, and a corresponding calibration method is derived and validated experimentally. After that, FBG-based FP sensor’s capability in measuring both Lamb wave signal (i.e. strain wave) and temperature separately is demonstrated. Finally, a validation test is conducted in which the current state signals are measured under a random temperature, different from that of the baseline temperature. Temperature effect on both sensor sensitivity and guided wave is calibrated based on the proposed calibration algorithm. The compensated signal is then tested with different types of damage index and its reliability in damage detection after applying the compensation algorithm is demonstrated.