Method for detecting early-stage mechanical property degradation of material by utilizing nolinear rayleigh wave

Abstract

The invention discloses a method for detecting early-stage mechanical property degradation of a material by utilizing nolinear rayleigh wave, belonging to the field of nondestructive testing. The invention comprises the following steps: inputting frequency, periodicity and other parameters of a selected transmission signal to a signal generator to generate a required single sound signal, and determining the incident angle theta of the transmission signal according to the wave speed of a piece to be tested; collecting a non-linear Rayleigh wave signal in equal time intervals in the stretching or fatigue loading process of the piece to be tested; and carrying out Fourier transform to obtain basic wave amplitude and secondary harmonic amplitude, computing the ultrasound non-linear coefficient beta, and knowing the early-stage mechanical property degradation of the piece to be tested according to beta. In the invention, a sensor is directly arranged at the edge of the piece to be tested to transmit and receive Rayleigh wave to improve the excitation and receiving efficiencies of the signal and decrease the non-linear influence brought by the coupling of the sensor and the piece to be tested; and both the excitation and the receiving adopt the piezoelectric sensor, thus being more applicable to engineering actual situation, and realizing continuous on-line detection on the piece to be tested.

Description

A Method for Detecting Early Mechanical Property Degradation of Materials Using Nonlinear Rayleigh Waves technical field The invention relates to a method for non-destructive detection of early mechanical performance degradation of metal materials by using nonlinear Rayleigh waves, belonging to the field of non-destructive detection. Background technique It is a very common phenomenon that the mechanical properties of mechanical parts degrade due to long-term tensile, compressive or alternating loads, and eventually fracture failure. The degradation of mechanical properties of metal parts is mainly divided into three stages at the micro level: the generation of a large number of dislocations and the formation of resident slip bands, the increase of slip bands and the nucleation and growth of microcracks, the generation of macrocracks, and finally fracture failure. For well-designed structural elements, the first and second stages typically account for 60% to 80% of the ov...

AI Technical Summary

Problems solved by technology

Most of the current research is to use the longitudinal wave nonlinearity to measure the ultrasonic nonlinear coefficient of the material, and it is impossible to detect the degradation of the mechanical properties of the plate structure.

In addition, since the nonlinear coefficient β that characterizes the magnitude of the nonlinear effect of the material is very small, it is easily overwhelmed by the nonlinearity brought by the detection instrument, etc.

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