Session: Virtual Presentations in Acoustics, Vibration, and Phononics

Paper Number: 94922

94922 - Bolted Lap Joint Monitoring Using Ultrasonic Guided Waves Considering Temperature Variations 

Bolted lap joints widely serve as a key connection approach in a large family of engineering infrastructures, the loosening of which will considerably hazard the structural safety and integrity and may even cause catastrophic failures. Structural Health Monitoring (SHM) and Non-Destructive Evaluation (NDE) systems strive to provide solutions for the detection and quantification of bolt loosening. Among various methods, ultrasonic guided waves have shown their superb capability. To date, the monitoring processes reported in existing literatures are usually conducted at room temperature. However, the ambient temperature in which the bolted structure serves is subjected to a range of variations. Changes in temperature may affect different components in a bolted structure, resulting in the change of sensing signals. This may be especially critical for nonlinear ultrasonic techniques, considering they aim to detect early-stage bolt looseness. Thus, the effect of temperature change in an SHM system for bolt monitoring cannot be ignored. This study investigates a variety of linear and nonlinear ultrasonic methods based on vibro-acoustic modulation (VAM) for monitoring bolt looseness. By studying the influence of temperature changes in these methods, a set of compensation algorithms are proposed to eliminate the influence of structural temperature changes on the monitoring results.

After a systematic discussion of the mechanism behind linear and nonlinear ultrasonic techniques for bolt looseness detection, experiments are performed on bolted structures at ambient temperature to illuminate contact acoustic nonlinearity (CAN) and vibro-acoustic modulation (VAM) phenomenon. The experiments utilize the pitch-catch method with piezoelectric wafer active sensors (PWAS) as the transmitter and the receiver. By generating ultrasonic, mixed frequency interrogative wavefields into the bolted connection, the sensing signal energy, high-order harmonics, and mixed responses picked up by the receiver under different bolt pre-tightening forces are observed respectively. A comprehensive damage index (CDI) associated with the linear energy and nonlinear components change is then proposed to evaluate bolt looseness in an entire tight-to-loose service span. To further study the effect of temperature change on the sensing signal, bolt with different degrees of looseness is heated to different temperatures. Active sensing experiments are conducted at different temperatures to study the effect of temperature changes on bolt with different degrees of looseness. The experimental results show that the effect of temperature change on the linear ultrasonic method is relatively small, while the influence on the nonlinear ultrasonic method is relatively large. By integrating the experimental results of different bolt looseness degrees and temperatures, the effect of temperature changes on the bolt loosening degree over the full service status can be obtained. Then, the temperature compensation of the comprehensive damage index (CDI) of the looseness degree is conducted. Validation experiments show that the temperature compensation for bolt looseness is highly accurate and effective. The proposed ultrasonic guided wave method with temperature compensation algorithm has great application potential in future bolt looseness monitoring tasks. The paper finishes with summary, concluding remarks, and suggestions for future work.

 

Keywords: bolt looseness, temperature compensation, vibro-acoustic modulation, nonlinear ultrasonic, structural health monitoring; nondestructive evaluation; guided waves

Presenting Author: Xuezhi Peng University of Michigan-Shanghai Jiao Tong University Joint Institute

Presenting Author Biography: M.S. in mechanical engineering, UM-SJTU Joint Institute, Shanghai Jiao Tong University, 2020.9-present<br/>B.S. in mechanical engineering, UM-SJTU Joint Institute, Shanghai Jiao Tong University, 2016.9-2020.8

Authors:

Xuezhi Peng University of Michigan-Shanghai Jiao Tong University Joint Institute
Yanfeng Shen University of Michigan-Shanghai Jiao Tong University Joint Institute