Abstract
This paper proposes a self-sensing nonlinear ultrasonic technique for fatigue crack detection under temperature variations. Fatigue cracks are identified from linear (α) and nonlinear (β) ultrasonic parameters recorded by a self-sensing piezoelectric transducer (PZT). The self-sensing PZT scheme minimizes the data acquisition system’s inherent nonlinearity, which often prevents the identification of fatigue cracks. Also, temperature-dependent false alarms are prevented based on the different behaviors of α and β. The proposed technique was numerically pre-validated with finite element method simulations to confirm the trends of α and β with changing temperature, and then was experimentally validated using an aluminum plate with an artificially induced fatigue crack. These validation tests reveal that fatigue cracks can be detected successfully in realistic conditions of unpredictable temperature and that positive false alarms of 0.12% occur.
Highlights
Failure of steel structures can have catastrophic consequences
It should be noted that the crack detection technique is specific to the test specimens and it should be noted that the crack detection technique is specific to the test specimens and the piezoelectric transducer (PZT) configurations used in this study, and caution is advised before generalizing the findings the PZT configurations used in this study, and caution is advised before generalizing the findings presented here to other applications
This paper describes a novel nonlinear ultrasonic fatigue crack detection technique that can
Summary
Failure of steel structures can have catastrophic consequences. Bridge collapse [1] and liquefied petroleum gas (LPG) tank explosion [2] are typical accidents associated with structural damage in steel members. A fatigue crack will cause a nonlinear interaction with ultrasonic waves, which manifests as ultrasonic super-harmonics if the structure is excited with an ultrasonic signal of a given frequency This method is highly sensitive to a fatigue crack’s nonlinear behavior, including micro-plastic deformation, dislocation, and clapping. The sub-harmonic method requires excitation power higher than a threshold determined by the force needed to generate clapping between the crack interfaces [11] Excitation power of this magnitude may be difficult to apply to real structures under harsh environmental and operating conditions. Since the proposed technique uses only a single PZT to generate and measure ultrasonic nonlinearities caused by a fatigue crack, the implementation problems associated with the need for sophisticated installation design and electrical distortion can be minimized [16,17].
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