Materials Ultrasonic Non-destructive Evaluation System For Signal Processing And Analysis

With the development of computer technology,digital signal processing technology is widely used in the ultrasonic non-destructive evaluation.It not only enhances the signal noise ratio of ultrasonic signals,but also can efficiently improve the sensitivity and precision of defect testing.Therefore,signal processing system is an important part of the ultrasonic non-destructive evaluation domain.Since there is a close relationship between microstructure and properties of material,the testing and characterization of material microstructure is the important branch of material science,as well as the major part of ultrasonic non-destructive evaluation.Different microstructure has different mechanical properties,which will result in the variation of ultrasonic velocity and attenuation coefficient,the information parameter relative with microstructure in echo signal will also have a change.Based on above theory,this study established an Material Ultrasonic Non-destructive Evaluation System for Signal Processing and Analysis (MUNDESSPA) on the basis of the mathematical theory model for ultrasonic signal processing method and their characteristic parameters,employed the VC++ as system developing platform,C++ language as the programming language and MATLAB as assisted language.It realize the ultrasonic non-destructive evaluation for the porosity of Carbon Fiber Reinforced Polymer(CFRP) and the density of Cr₂O₃ coating irradiated by High-intensity pulsed ion beam(HIPIB).Different decomposition and about 22 mother wave functions for a series of Daubechies,Smylet and Coiflets are studied to reduce the noise of CFRP ultrasonic echo signals by the time frequency function GDI of MUNDESSPA.It is shown that db8 mother wave has the best effect on reducing the noise of CFRP ultrasonic echo signals by comparing and analyzing the signal noise ratio and the root mean square error of these mother waves.Processing procedure is very shortcut and convenient for employing the MUNDESSPA to reduce the noise by wavelet.Power spectrum analysis was investigated on the CFRP ultrasonic echo signals employed the frequency analysis function GDI of MUNDESSPA.A series of power spectrum characteristic parameters were extracted,and the relationship between the parameters and the porosity of CFRP(0.03%-2.3%) was analyzed.The study indicates that the porosity of CFRP can be characterized by Energy for Limited Frequency Band and Energy for Principle Frequency.The normalization power spectrum of the echo signals for the Cr₂O₃ coating irradiated by HIPIB were obtained via MUNDESSPA.Center frequency,Energy for Limited Frequency Band were extracted by the frequency analysis function GDI of MUNDESSPA.The study indicates that center frequency increases with the increase of density for the Cr₂O₃ coating irradiated by HIPIB.