Ut Signal Spectrum Analysis Of Basic Research

Among the five kinds of NDE ways (RT, UT, ET, PT, MT), Ultrasonic Testing technology develops very fast because of its merits such as good orientation, strong penetration ability, higher energy and no harm to human health.The analysis of ultrasonic wave spectrum is one kind of technology, in which the theories and methods of spectrum analyzing were applied. Generally, the information that provided by the original ultrasonic signals is too limited to meet the demand of wave analysis and characteristics identification. Therefore, these signals need to be further processed and transacted. Through the discrimination and analysis of spectrum of domain function, more useful information would be acquired to guide the research and engineering work. Because the characteristics of frequency domain is slightly affected by the coupling state and only related with the defects by revising of the system, the technology of ultrasonic wave spectrum analysis is necessary tool for quantity or automatic testing.Based on the character of ultrasonic spectrum analysis, considering the affection of the circuit responsion of checking system, coupling state, position of checking transducer, this thesis established reasonable ultrasonic spectrum analysis method. Using this method, several kinds of linear spectrum (such as phase amplitude spectrum, phase power spectrum) were researched and discussed.During the research, ultrasonic signal testing system was designated by adopting transform the average value of function to nought, optimizing of collection frequency and transducer frequency. Normalization method of ultrasonic testing signal, the advantages and disadvantages of time domain, frequency domain were discussed. The effect of adding windows that included Rectangle window Hanning window, Hamming window, Blackman window was also researched. Based on the above-mentioned studies, different kinds of frequency spectrum of different heat treatment technologies of 38CrMoAl steel were analyzed and researched. Results showed that the samples of different heat treatment technologies of 38CrMoAl can be comparatively preferable distinguished by real spectrum and phase spectrum of FFT. Further research on real and image spectrum of FFT discovered that using energy spectrum of real and image of FFT to discriminate these samples is more compact and convenient.