关键词: Lamb波, 板结构, 离散圆弧成像, 全向型磁致伸缩传感器, 缺陷成像

Abstract: Lamb waves can achieve defect detection and monitoring with large scale and high efficiency in plate-like structures because of its advantages including long propagation ability and low attenuation. Thus, Lamb wave technology has immense application potential in nondestructive testing and structural health monitoring. Aiming at consistently exciting single Lamb wave, S0 mode, in circumferential direction and improving imaging ability for the wide range health monitoring of plate-like structure, an omni-directional S0 mode magnetostrictive transducer is developed on basis of magnetostrictive effect and it consists of a coil on PCB, a cylindrical magnet and a circular nickel patch. The experimental results firstly verify that this type of transducer can effectively produce the pure S0 mode in an aluminum plate. Then, the frequency response characteristics and omni-directivity of this developed transducer are tested. The results demonstrate that developed transducer has a center frequency of 365kHz and high omnidirectional consistency. Furthermore, a distributed sparse transducers array is built by using developed omni-directional S0 mode magnetostrictive transducers. An aluminum plate is detected in pulse-echo mode by using this transducer array. The combination of discrete arc imaging and data fusion algorithm is used to deal with multiple sets of data, which eliminates the dependence upon the signals in health condition compared with the conventional sparse transducers array imaging algorithms. The location and imaging of the defect could be well achieved without the need of reference signals in health condition.

Key words: defect imaging, discrete arc imaging, Lamb waves, omni-directional magnetostrictive transducer, plate-like structure