The Research And Application Of Wavelet Analysis In Ultrasonic Signal Processing

Aluminum alloy, as one of the nonferrous metal structural materials, is widelyapplied in modern industry. In heavy industries, such as aircraft manufacturing,shipbuilding industry and automobile manufacturing, aluminum alloy, instead of steeland cast iron in traditional way, can effectively reduce the weight of the componentsand improve their structural strength and cooling performance. In light industry areaeslike household appliance industry and construction material industry, aluminum alloyis also a wide-used material. However, among the various parts and accessories madeof aluminum alloy, there may be defective ones possibly caused by the flaw of thematerial itself, the production process or even the environmental influence. If theseparts and accessories can’t be found and eliminated, quality problems may occur,which causes enormous damage to people and property. Therefore, so as not todestruct the material’s original structure and chang its performance, it is of muchimportance to detect the applied aluminum alloy with nondestructive testing methodThis paper presents the application of wavelet analysis theory to thenondestructive testing of aluminum alloy in the following way:In the first place, the author investigates the theory of ultrasonic nondestructivetesting of type A pulse reflection and explains the descriptions of ultrasonic wave’sphysical quantities and its characteristics before he makes three steps for ultrasonictesting of aluminum alloy and gives each step a detailed analysis as well as establishestesting models.Secondly, the author introduces the basic principles of wavelet analysis. Hecompares wavelet analysis with other signal processing methods about theiradvantages and disadvantages, elaborates the concepts of continuous wavelettransform and discrete wavelet transform, and studies the characteristics and appliedoccasions of several usual wavelet function.To go further, the author gives a brief introduction to the concept of themulti-resolution analysis and probes into the features of wavelet basis function. Withsimulated experiment, he chooses wavelet sym8as the basis function of waveletanalysis for the aluminum alloy’s ultrasonic testing signal. In the end of the paper, the author has found the best way to get the denoisingthreshold and the accurate position of the internal defects of the aluminum alloy withMATLAB to do denoising and wavelet multi-resolution analysis respectively on thethree ultrasonic testing signals, which proves this paper has the value of engineeringapplication.