Design And Research On The Identification System Of Typical Defects Inside Hetian Nephrite Under Ultrasonic Detection

As science and technology continue to advance and develop,most consumers of Hetian nephrite currently still use traditional means,combined with experience,to determine whether the interior of the nephrite contains cracks,water lines,cotton,and other defects.When consumers carve the nephrite they purchase,the internal defects affect the aesthetics of the carving and the artistic and cultural value of the nephrite is affected to some degree.In response to these problems,a research based on piezoelectric ultrasonic nondestructive testing technology is proposed,which combines signal processing algorithms and electronic computer technology to investigate the methods and equipment for detecting defects in Hetian nephrite.The main work of this paper includes.Establish a simulation model for detecting typical defects in Hetian nephrite based on piezoelectric ultrasonic inspection technology.Firstly,the various rock mechanical parameters of Hetian nephrite were obtained according to the rock compressive strength test,and the longitudinal sound velocity of Hetian nephrite was calculated by combining the rock mechanics and rock acoustics theories,followed by the use of COMSOL Multiphysics finite element simulation software to establish a simulation model based on piezoelectric ultrasonic technology for the detection of typical defects in Hetian nephrite;according to the results of the finite element model calculation,the ultrasonic wave propagation snapshot in Hetian nephrite was analyzed.Based on the results of the finite element model,the propagation snapshot of ultrasonic waves in Hetian nephrite is analyzed,and the results are consistent with the theory of propagation of sound waves in solid media;the ultrasonic signals of Hetian nephrite containing defects are obtained experimentally and compared with the simulated signals,and their characteristic patterns are consistent.A typical defect identification method for Hetian nephrite based on piezoelectric ultrasonic technology is proposed.Firstly,Gaussian white noise is added to the defect signal calculated in the simulation model,and three kinds of orthogonal wavelets,Daubechies,Symlet and Coiflets,are used to denoise the noise-containing simulation signal,and the signal-to-noise ratio values after comparing the three types of wavelet functions after noise reduction are shown,and the results show that the best denoising effect is achieved by using Coif4 wavelet function;then the denoised signal is subjected to frequency domain,time domain and time After verification,it is found that the SVM model has the best performance in recognition,and the recognition rate is high compared with the other two,and the recognition rate is above 85%.The results validate the feasibility of using wavelet denoising method,establishing multi-domain feature sets,PCA algorithm feature dimensionality reduction and recognition of typical defects of Hetian nephrite.A piezoelectric nondestructive testing device for detecting typical defects in Hetian nephrite was developed.The acquisition device of piezoelectric ultrasonic signal for typical defects of Hetian nephrite was integrated according to the demand of actual inspection,which contains signal excitation circuit,signal receiving circuit.At the same time,a Lab VIEW-based ultrasonic signal management software system was designed.After testing,the software system is more inclusive and has good stability.Therefore,it is considered that the experimental device can meet the demand of ultrasonic detection of typical defects in Hetian nephrite.