Research On Nondestructive Testing Technology Based On Improved Spectral Subtraction And Resonance Acoustics

As an effective means of detecting parts defects and improving the quality of parts,nondestructive testing technology is widely used in vehicles,ships,metallurgy,electric power,petrochemical,aerospace,nuclear energy and other industries.Aiming at the problem that the existing non-destructive testing technology cannot realize the rapid damage detection of largescale mechanical parts,this paper proposes a non-destructive testing technology based on improved spectral subtraction and resonance acoustic principles.This technology is used to determine the damage by obtaining the natural frequency of the part.The main contents are two aspects: there must be noise interference in the actual factory environment,using the improved spectral subtraction method to reduce the noise of the acoustic vibration signal;using the test built based on the principle of resonance acoustics The platform obtains the natural frequency of the part.In view of the problem of noise residue and "musical noise" generated by the original spectral subtraction noise reduction,continue to optimize the parameters on the improved spectral subtraction proposed by M.Berouti.According to the basic principle of spectral subtraction,the original spectral subtraction and improved spectral subtraction programs were written using MATLAB software,and the performance of the improved spectral subtraction was verified through the time-frequency analysis of the knocking vibration signal added to simulate factory noise and the signal after noise reduction.Noise reduction effect.According to the principle of resonance acoustics combined with hammering method,a non-destructive testing test platform is built.The platform is composed of electric power hammer,highprecision microphone,industrial sound card and analysis software.Taking the valve rocker arm as an example,the test mode and calculation mode of the part were obtained through the platform and ANSYS software,respectively,and the reliability of the platform data was verified by the comparison of the modal data.The repeatability verification of the platform is accomplished by 10 inspections of a good part.30 qualified parts,15 cracked parts,15 inclusion parts and 15 shrinkage cavity parts were tested on the platform,and the corresponding database was constructed by the test data.Based on the analysis of the database,the criteria for judging whether the parts are qualified or not are determined.10 parts of unknown state were randomly selected for testing,4 defective parts were successfully identified,and the test results were verified by mature non-destructive testing equipment.The feasibility of the NDT technique proposed in this paper is proved.