Portable Nondestructive Detecting Device Design Based On Eddy Current Sensor And Algorithms Related Analysis

Nondestructive testing of metal as an effective tool for industrial development is essential, to an extent to reflect level of industrial development in a nation. It is necessary requirement to design a nondestructive portable metal detector with functions of information collection, processing and storage, so that the use of this technology will be much more broadened. Pulsed eddy developed rapidly in recent years as a non-destructive testing of new technology, its broadband spectrum is available to more excitation-type defect information, and thus become a research hotspot of the field of non-destructive testing.Based on the analysis of foreign and domestic pulsed eddy current nondestructive testing technology research status, a nondestructive eddy current testing device design is improved and the subsequent time-frequency analysis for nondestructive metal detection data is designed and enhanced. The main work is as follows:First, a brief introduction about basic concepts and terms of eddy current theory, such as skin depth, is presented, and then introduce principles of pulsed eddy current testing techniques. Then, a three-dimensional finite element simulation about the impact of various eddy current sensor factors using software ANSYS is introduced. Thus, the results of factors such as coil size, pulse frequency, duty cycle and voltage magnitude are obtained and compared. Those works are for the foundation of detection device design and analysis of algorithms.Then, for the purposes of miniaturization, energy-saving and accuracy, a complete new pulsed eddy current inspection device for data collection is designed. Unlike other data collecting device, an overall structure using MSP430 series chips is designed knowing as multi-processor; to achieve the purposes of energy-saving, miniature and stabilization, I2C bus is applied for module communication, a three coaxial coil eddy current detector for pulse detection is designed, and inbuilt AD function is used.Finally, time-frequency analysis method is applied on data collected for further processing. Based on the analysis of various characteristics of time-frequency analysis method, methods such as pseudo-Wigner-Ville distribution (Pseudo Wigner-Villle Distribution, PWVD) and smoothed pseudo Wigner-Ville distribution (Smoothed Pseudo Wigner-Villle Distribution, SPWVD) are applied and enhanced to classify and meature metal defects.In short, a system of portable nondestructive detection device ranging from device design and data analysis is designed, and strong practical value of this system is proved.