Low-power vibrothermography detection technique for surface cracks on composite sucker rod

Composite sucker rods are becoming increasingly popular in oil fields owing to their light weight and corrosion resistance. However, various defects may appear in the manufacturing and service of sucker rods. Unfortunately, research on defect detection is still insufficient for composite sucker rods. This study explores a surface crack detection technique for composite sucker rods based on low-power vibrothermography (LVT). First, an improved low-power piezoceramic actuator with a curved bottom is designed for rod-like structure. Second, the entire processes of LVT-based surface crack detection, including excitation signal generation, mechanical wave propagation, and heat generation at defects, are simulated and analyzed using the finite element method. The heat generation mechanism and characteristic at cracks are revealed by coupled thermo-electro-mechanical analysis. The superiority of the improved actuator is reflected by comparison with the conventional actuator. In addition, the simulation investigates the optimal excitation signal amplitude and circumferential angle between the actuator and the crack. Finally, a series of LVT detection experiments were conducted on a composite sucker rod with surface cracks, which not only proved the effectiveness of the LVT, but also validated the conclusions of the numerical simulations. The maximum temperature rise at the crack is 5.54 °C by using the improved actuator. Numerical simulation and experimental results demonstrate that the surface cracks of the composite sucker rod can be effectively detected using LVT with an improved piezoceramic actuator. This study provides a new direction for extending vibrothermography to the non-destructive testing of composite rod-like structures.