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Method for evaluating microcrack width through nonlinear frequency mixing sound waves

A micro-crack, nonlinear technology, used in the analysis of solids using sonic/ultrasonic/infrasonic waves, processing of detected response signals, instruments, etc., can solve problems such as parameters that cannot be effectively evaluated for cracks

Active Publication Date: 2018-11-13
NANJING UNIV OF SCI & TECH
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Problems solved by technology

Based on this characteristic, the nonlinear mixed-frequency acoustic method modulates the excitation signal by changing the state of the crack with an external modulation signal, and can determine whether there is a micro-crack according to the generated nonlinear sidelobe, but it cannot effectively evaluate the parameters of the crack

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  • Method for evaluating microcrack width through nonlinear frequency mixing sound waves
  • Method for evaluating microcrack width through nonlinear frequency mixing sound waves
  • Method for evaluating microcrack width through nonlinear frequency mixing sound waves

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Embodiment Construction

[0017] The solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0018] Such as figure 1 As shown, the method for evaluating the width of microcracks by nonlinear mixed-frequency acoustic waves includes the following steps:

[0019] Step 1. Excite two columns of sound waves with different frequencies, which are respectively used as an excitation signal (detection signal) and a modulation signal.

[0020] It is generally required that the modulation signal is a low-frequency sound wave, and the frequency is the natural frequency of the structure. Its size varies with the structure, generally tens to several thousand Hz, and the frequency used in this manual is 1kHz; the detection signal is a high-frequency sound wave, and the frequency is much greater than Modulation frequency, in numerical analysis, it is generally advisable to take 20 to 50 times (the frequency multiplication of the modula...

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Abstract

The invention discloses a method for evaluating a microcrack width through nonlinear frequency mixing sound waves. The method comprises the following steps: firstly, exciting two rows of sound waves of different frequencies as an excitation signal and a modulation signal respectively; receiving mixed sound waves passing through a material, and carrying out fast Fourier transform so as to obtain afrequency spectrum of the mixed sound waves; analyzing the frequency spectrum of the mixed sound waves, confirming whether sidelobe order missing is caused or not, if sidelobe order missing is caused,calculating a microcrack width, or else modulating an amplitude of the modulation signal, and carrying out detection for another time. By adopting the method, under the condition that microcracks arealready confirmed in the prior art, the width of the microcracks can be confirmed according to influence of crack widths upon nonlinear sidelobe, and theoretical foundations can be provided for defect detection, crack growth and material service life evaluation.

Description

technical field [0001] The invention relates to non-destructive testing technology, in particular to a method for evaluating micro-crack width through nonlinear mixed-frequency sound waves. Background technique [0002] Non-destructive testing is a method of testing materials without damaging the shape and performance of materials. The propagation of sound waves in materials will be affected by the material structure. When the material structure is discontinuous or uneven, the propagation of sound waves will have phenomena such as reflection, refraction, scattering and delay. By detecting these sound wave parameters in the material, the Information such as impurities and cracks in the material can be obtained. [0003] Traditional crack detection methods determine the location and size of cracks based on changes in the linear characteristics of acoustic waves during propagation, but they can only detect larger cracks. Since cracks in materials can induce nonlinear phenomen...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/04G01N29/44
CPCG01N29/04G01N29/44G01N2291/0289
Inventor 袁玲唐俊杰
Owner NANJING UNIV OF SCI & TECH
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