Wireless Ultrasonic Lamb Measurement System And Lamb Signal In Steel Plate Processing And Analysis

With the fast development of the electronic technology and computer network technology, wireless communication technology becomes mature quickly. The traditional ultrasonic testing technology can no longer meet high reliability and high efficiency requirements in modern industry, combine wireless communication technology and ultrasonic Lamb measurement technology, develop an effective, online, practical wireless ultrasonic Lamb wave nondestructive measurement system become an important direction in the development of nondestructive testing.Firstly, based on the ultrasonic guided wave theory, in the paper, the Lamb wave theory is studied, the propagation characteristics and detection principle of the Lamb wave in the structure are discussed, solving riley-Lamb equation through the Matlab programming, and plotting the frequency dispersion curve of Lamb wave.Secondly, combining the characteristics of wireless communication technology and ultrasonic lamb measurement technology, a wireless ultrasonic nondestructive measurement system is developed, and the principle and component of the measurement system are analyzed. System uses CTS-3000to excite and receive the ultrasonic signal, and then the collected signal can be transmitted by the wireless transmission module which is controlled by the system level chip MSP430F149single-chip microcomputer. The wireless receiving module realizes serial communication between MCU and computer using the RS-232-C interface standard, and the signal is transmitted into a computer to display, record, store and process. Then the Lamb time-frequency analysis method is discussed and compared in the article, and the signal is analyzed from the time domain and frequency domain aspect respectively to find suitable method for analyzing the unsteady signal; The comparison among Fourier Transform, Short-Time Fourier Transform, Wavelet Transform and HHT transform is analyzed; Through the comparison with Fourier Transform, Short-Time Fourier Transform and Wavelet Transform, find the analysis method which is suitable for representing and evaluating the Lamb ultrasonic nondestructive detection for thin layer materials.Finally, time-frequency analysis and research on the Lamb signal collected from the steel structure are introduced, which mainly include the detections on no-defect steel and different size hole (artificial defects), analyses of time domain, frequency domain and time-frequency analysis (STFT and HHT) on the acquisition Lamb signal in method are compared, the experiment results show that the simulation defects existed in the plate can be identified effectively by the frequency domain and time domain analysis method. STFT can identify the Lamb wave modes in test signals effectively, and HHT method can reflect the distributions of the Lamb wave signal modes with time and frequency.