| Eddy current testing technology is a widely used nondestructive testing method in recent years. And it is a non-contact measurement especially available for crack detecting on metal surface, which has the merits of high detection sensitivity and fast testing velocity. In this paper, a crack detection system is designed based on eddy current testing technology to realize the detection of cracks with certain sizes on metal surface.Based on the analysis of eddy current testing technology, the paper designs the hardware and software of eddy current testing system. The hardware of eddy current testing system consists of signal generation circuit, AC Bridge and signal conditioning circuit. The signal generation circuit is used to generate stable and accurate excitation signal with enough power. AC Bridge is front end of the system, which consists of a detecting coil and a reference coil. These two coils are set on adjacent bridge arms for testing cracks in comparison mode. Signal conditioning circuit is designed for the amplification, filtering and demodulation of eddy current testing signal. Based on correlation detection technology, lock-in amplifier is designed to extract weak useful signal from strong noises. The anti-interference methods of eddy current testing are analyzed. Based on LabVIEW virtual instrument technology, the function modules of data storage, data acquisition and real-time display are realized in the software of eddy current testing system. The hardware and software of the system are debugged for their good condition. The standard specimen with different sizes of cracks is designed and measurement experiment on cracks of the standard specimen is carried out.From the experiment, it can be seen that eddy current testing signal of crack consists a wave crest and a wave trough, and the peak value becomes bigger as the width of crack increases. The result shows that the eddy current testing system obtains good effect on crack testing. |
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