Propagation Characteristics Research Of Ultrasonic Lamb Wave

Most of the times, materials must go through quality control and inspection strictly before they were used in the key component. Compared with conventional ultrasonic testing techniques, ultrasound Lamb wave has great advantage, and plays an important position in nondestructive testing. However it still exists some disadvantages, which include multi-mode and frequency dispersion and bring many problems in the practical detection, such as recognition of signal model, acquisition of the signal interpretation and so on. All of these greatly limit its application in industry.Lamb wave frequency dispersion curve is an important reference for nondestructive testing, before the Lamb wave detection technology can widely used, there are two problems need to be solved, they are frequency dispersion equation and the solution of fast drawing for the Lamb frequency dispersion curve. This paper introduced the theory of elastic dynamics wave equation and stress analysis of free board surface, then got the frequency dispersion equation Lamb wave, and put forward a simple, fast wave equation and a method for curving Lamb wave, at last the Lamb wave curve of specific plank can be drawn in the MATLAB software by Newton-Raphson method.The keys for Lamb wave testing are mode identification and precise explanation for the extraction of received signal. According to the Lamb wave frequency dispersion characteristics, the paper first put forward a new method to analyze propagation characteristics of Lamb wave, established the mode of propagation theory, then got the mathematical expressions. When the propagation of signal pattern Lamb wave is ideal conditions, through the MATALB software simulation, it can get time-frequency curve, amplitude-frequency curve and phase-frequency curve. Second, it used the faultless steel plate to stimulate Lamb wave of single pattern in ideal condition, collected signal through the signal acquisition system, and saved these data. By processing these data, the further understanding of the Lamb wave’s frequency dispersion characteristics.At the end of the paper, a time frequency analysis software of Lamb wave was made based on the GUIDE environment of MATLAB, the production of the software realizes human interaction, greatly promote the application of Lamb waves in nondestructive testing.