A New Method For Detecting Metal Defects In Planar Array Electromagnetic Sensors

With the rapid development of our country's industry,the use of metal is increased rapidly,and various types of metal materials are widely used,such as construction,automobile manufacturing and aerospace industry.In the heavy use of metal,if the metal materials used are defective,safety hazards and industrial accidents will be caused.So effective detection of metal defects in the early stage is a key problem.In the detection of metal defects,a detection device consisting of one or two sensors is usually used for point-by-point scanning detection,but the test results are not accurate enough and time consuming.By increasing the number of sensors,the accuracy of detection can be improved,but the detection results are still abstract and can only reflect the partial characteristic information of metal defects.The accuracy of detection can be improved by the intuitive test results,and visual detection is one of the new directions in the development of metal defect detection technology.Electromagnetic tomography is a visual and nondestructive testing technique based on electromagnetic theory.This detection technology has the advantages of fast detection speed,high sensitivity,non-contact and visualization.In this paper,a new method for metal defect detection based on electromagnetic tomography is proposed.This paper mainly includes the following aspects:1.In order to get better detection results of metal defects,a new plane array electromagnetic sensor is designed.The new sensor consists of nine coils arranged in a 3 by 3 matrix.All coils are fixed in a square non-conductive plastic disk and parallel to each other to enhance mutual sense.2.A new method of metal defect detection based on electromagnetic tomography is used to detect the defective aluminum plates.Compared with traditional scanning method,the new method can obtain reconstructed images of metal defects,reconstructed images can visually reflect the location,shape and size information of metal defects.When the metal defect image is reconstructed,the new method needs to solve the inverse problem.Compared with the reconstructed image obtained by using L2 model and conjugate gradient algorithm,the marginality of reconstructed image obtained by using the Ll regularization model and SplitBregman algorithm has been effectively maintained.The simulation and experimental results show that the electromagnetic tomography detection method is more suitable for the reconstruction of metal defect image.3.In this paper,the software of EMT metal defect detection system is designed by LabVIEW.It mainly includes five modules:communication interface module,data acquisition and processing module,finite element mesh module,algorithm module and image display module.The reconstructed image of metal defect is visually displayed by the software.