Research On Nondestructive Testing System Of Electrical Impedance Of CFRP Board Based On Four-electrode Method

The four-electrode electrical impedance nondestructive testing technology has the characteristics of high accuracy,fast response,and easy operation.It can quickly detect specific composite areas,obtain impedance information,and determine whether there is damage,which is of great significance for improving airworthiness of aircraft.However,different electrode structure parameters have different effects on damage identification,and improper selection of electrode structure may even cause structural damage in composite materials to be unrecognizable.Based on the four-electric method of electrical impedance composite material nondestructive testing technology,this paper conducts in-depth research,analyzes the structural parameters that affect the performance of the sensor,and combines the performance indicators to optimize the structure,and builds a detection system to verify the feasibility of the sensor to detect damage.The research content of this article is as follows:(1)Firstly,analyze the principle of four-electrode electrical impedance detection,determine the performance evaluation index and structural optimization parameters of the four-electrode,The response surface mathematical model was established to obtain the sensitivity,measurement range,image correlation coefficient performance index response surface fitting function,and the accuracy of the fitting function was verified by the complex correlation coefficient and significance value.(2)A multi-objective genetic algorithm based on NSGA-Ⅱ was used to optimize the structural parameters of the four-electrode sensor,so as to obtain the optimal solution of the Pareto boundary,and it was compared with the traditional single-objective algorithm.The objective particle swarm optimization algorithm was used to analyze three kinds of damage,and the results show that the multi-objective genetic algorithm of NSGA-Ⅱ can obtain better sensitivity.,correlation coefficient and measurement range at the same time.(3)Construct a large number of four-electrode method scanning detection composite material damage models through Comsol finite element analysis software,obtain impedance information,The electrical information collected is processed by support vector machine network,and the penalty factor and kernel parameters are optimized by genetic algorithm to achieve effective damage classification.(4)Use the designed PCB sensor probe,LCR precision measuring instrument and Labview host computer to build an electrical impedance detection system to detect three types of damage,and verify the feasibility of the electrical impedance detection system in engineering practice from the sensitivity and imaging effect.