Nonlinear wave detection method for high-cycle fatigue damage of metal sheet

Abstract

The invention discloses a nonlinear detection method for high-cycle fatigue damage of a metal sheet. The method is suitable for detection and characterization of fatigue early-stage micro-defects and micro-damages in the metal sheet, and belongs to the field of nondestructive testing. The method comprises the steps: firstly, determining the excitation frequency of a fundamental frequency wave according to a measured object and a nonlinear Lamb wave resonance condition; arranging a pair of detection probes, namely an ultrasonic transmitting probe and an ultrasonic receiving probe, in the same side direction of a test piece, and carrying out nonlinear detection on the metal sheet structure; scanning different positions of the test piece by changing the excitation time delay of an excitation signal, and extracting a fundamental wave amplitude and a second harmonic amplitude; and finally, according to the change rule of the ultrasonic nonlinear coefficient along with the detection position, achieving detection of the fatigue damage of the metal plate and characterization of the damage degree. According to the invention, a band-pass filter at a certain frequency is introduced, and an original high-pass filter is replaced by the band-pass filter, so that the received signal is purer, and meanwhile, the data processing difficulty is greatly reduced.

Description

technical field [0001] The invention relates to the technical field of high-cycle fatigue damage detection of metal materials, in particular to a nonlinear wave detection method for high-cycle fatigue damage of thin metal plates. Background technique [0002] As an important energy conversion device, centrifugal compressor is widely used in important fields such as electric power, energy, metallurgy, petroleum, and chemical industry. The impeller and blade are the core modules of the centrifugal compressor, and FV520B high-strength steel is used as a common material for making the impeller and blade. Because of the harsh working environment, complex load bearing and long service time, fatigue failure is often prone to occur. For well-designed structural parts, early fatigue damage of materials (before the formation of macroscopic cracks) occupies a large proportion of the entire fatigue life, and for fatigue-damaged structural parts, its early performance degradation account...

AI Technical Summary

Problems solved by technology

Although the nondestructive testing technology included in the linear ultrasonic testing technique is ideal for detecting macroscopic defects in materials, it is not sensitive to early damage (such as dislocation structure, microcracks, holes) in the material before macroscopic cracks appear in the fatigue process

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