A Modified Time Reversal Method for Guided Wave Detection of Bolt Loosening in Simulated Thermal Protection System Panels

Abstract

In this work, a modified time reversal method is proposed for guided wave detection and localizing loosened bolt in a complicated multibolt-jointed structure. Different from the traditional time reversal guided wave method, the response signal due to a tone burst input received at the healthy state is time reversed and recorded as a standard reemitting signal. In the detection process, this recorded standard signal is used for all damage cases to yield time reversal-focalized reconstruction signals. This largely improves the sensitivity of the focalized signal to damage state. In this paper, the peak amplitude of the focalized wave packet in the reconstructed signal is calculated and utilized as tightness index. By bonding PZT transducers at different joint locations inside the structure, multiple tightness indices, where each tightness index presents the correlation between the current joint condition to its healthy condition at the joint, can be obtained. To analyze a large number of tightness indices, a principle component analysis method is introduced, and a neural network-based loosening detection method is proposed. The proposed method is experimentally validated in a simulated double-layer bolt-jointed thermal protection system panel. Experimental results illustrate that the proposed method is effective to identify and localized the bolt loosening in complicated multibolt-jointed structure. The detection and identification of the location of multibolt loosening is realized.

A nonlinear ultrasonic method for real-time bolt looseness monitoring using PZT transducer–enabled vibro-acoustic modulation

“…Because of its spacetime-matched filtering property, good anti-noise performance property, and less channel interference property, the time-reversal method has been widely used in the field of SHM (Miao et al, 2011;Yu and Leckey, 2013). As shown in Figure 4 (Wu et al, 2018a), the schematic indicates the principle of the time-reversal method for bolt looseness detection:…”

Experimental research on online monitoring of high temperature and high speed airflow ablation of quartz ceramic thermal protection structure using guided wave

“…Wang et al 19 took advantage of GW and performed experimental research on the disband damage monitoring of foam-based thermal insulation systems in a load-temperature environment; the results showed the effectiveness of the proposed research. Wu et al 20 proposed a modified time reversal method for locating loosened bolt, and verified its effectiveness in a simulated TPS steel panel. Liu et al 21 presented a numerical study of GW wavenumber change in TPS with debonding defect by using local wavenumber method.…”

Multi-scale entropy based damage detection for thermal protection structures with variation of ambient temperature

“…Le conducted experiments to detect damage in TPS by comparing the natural frequencies and damping ratios with those of healthy state (Le and Goo, 2020). Wu et al (2018) used embedded PZT transducers inside the TPS to detect loosen bolts. In this work, the piezoelectric transducers are used as both actuators and sensors to excite and receive signals.…”