| Ultrasonic digital testing technique has an important function in the field of the nondestructive testing. According to the digital signal processing of the sampling points the digital filtering and detection of ultrasonic echo signal can reconstruct the enveloping curve of the wave, exactly locate echo peak value and its time, and so fix the size of flaw and its location in the welding line. The method has many remarkable advantages such as highly testing speed, flexible processing, wide sphere of application, accurately locating the flaws and convenience etc. Along with the high-speed development of the computing and information technology, certainly it will get more and more attention in future.Based on the basic principles of ultrasonic testing and the basic methods of digital signal processing, this thesis has designed preprocessed hardware circuit, a digital filter and a digital detector according to the need of practical use and validated its correctness by experimental results.The following are main achievements of this thesis:1. Detailed discussion of the basic principles of ultrasonic testing and the basic methods of digital signal processing, analysis of combining both reasonably, putting forward corresponding mathematical processing model.2. Designed the front preprocessed hardware circuit of the digital filter and detector and achieved accurate acquisition of the ultrasonic signal.3. Put forward the automatic identification method of ultrasonic probe actual frequency, used subsection scanning technique to perform this function and compiled correlative program to validate it.4. Designed the digital filter of ultrasonic signal, compiled corresponding MATLAB software procedure, took an experiment towards input acquisition signal and got good results.5. Designed the digital detector of ultrasonic signal, compiled corresponding MATLAB software procedure to take testing and experimenting and got good wave and enveloping curve. Also analyzed the experimental results in detail.
|
PDF Full Text Request