Interaction of Low-Frequency Guided Waves with Discontinuities
Modern methods of ultrasonic nondestructive testing allow one to detect defects in pipes with the help of guided ultrasonic waves. This chapter studies the propagation of longitudinal and torsional ultrasonic low-frequency guided waves in a pipe with discontinuities and defects. The defects considered for investigations include notches, holes, and their combination. Solid and finite element numerical models are developed for a sample pipe without defect, and for sample pipes with various types of defects. In order to simulate the propagation of ultrasonic guided waves in an isotropic medium, an excitation load is applied to one end of the pipe. For longitudinal guided waves simulation, the load vector is directed along the length of the pipe, and for torsional guided waves simulation, the load vector is directed tangentially to the circumference of the pipe. The results of the simulations allow us to estimate the amplitude and transit time of the impulse reflected from the defect and to analyze how various defects influence the stress–strain state of the pipeline.
KeywordsUltrasonic guided wave Low-frequency guided wave Nondestructive testing Defect detection Torsional wave Longitudinal wave Finite element method Stress–strain state
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