Abstract: Aiming at background clutter of TOFD, the modified variable step size LMS was proposed for suppressing lateral wave of ultrasonic TOFD images. First, step factor of the relationship with the steady-state error was analyzed for obtaining the optimal variable and variable step iterative formula. Secondly, the memory factor concept was introduced for solving the problems of algorithm does not fully converge step factor has been reduced to a minimum. Finally, the algorithm was applied to non-near-surface and near surface defects defect images, the relationship between error signal and step size factor under different parameters was studied, filtering effect was compared, and the influence of each parameter was discussed. The results indicate that the suppression effect of lateral wave is the best when the value of α is 0.02 and the value of β is 0.8. This method can effectively removal the timing jitter lateral waves.
Key words: time of flight diffraction (TOFD); non-destructive testing; least mean square（LMS）; the memory factor; variable step