Aiming at the need of safe operation of power plant,the nonlinear ultrasonic detection method of thermal damage of high temperature pipeline by collinear mixing is studied.The excitation conditions of significant mixing effect were determined by frequency sweep experiment,and nonlinear ultrasonic testing experiments were carried out on four Super304H pipes with different thermal damage degrees.The detection signals were analyzed by bispectrum to investigate the distribution of bispectrum of sum frequency component in phase interval,and the phase distribution range of nonlinear response caused by thermal damage was determined.The results show that the nonlinear acoustic coefficients extracted in turn have a good correlation with the thermal damage degree of the specimen,which can be used to characterize the thermal damage of the pipeline.The research work provides a feasible scheme for thermal damage detection of high temperature pipelines in power plants.
High temperature pipelineThermal damageWave mixing nonlinearUltrasonic testBispectrum
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