Quantitative Research On Micro Crack Based On Magnetic Flux Leakage Sensor Of Module Combination

There are many non-destructive testing methods in industry, such as eddy inspection, magnetic powder inspection, magnetic flux leakage(MFL)inspection,ultrasonic inspection and so on. on.Among them,MFL inspection is a classical NDT technology, with the characteristics of quick speed, high detection rate, high sensitivity, and easy operation. MFL inspection can work in all complex environment,and be able to realize quantitative inspection more easily. This paper applied MFL methods for detecting cracks on the specimen. During the course of testing, we need not only find where the defect exists,but also analyze the defect quantitatively to realize accurate prediction of defect parameter. The main research content is as follows:On the basis of theoretical study, the principles of magnetic flux leakage detection technology are discussed, and some concepts in this detecting method are introduced. Then this paper uses magnetic dipole to study the relation between rectangle crack and MFL field, and gets the change rule between the two variables.Meanwhile, some other influencing factors in MFL are also analyzed.Aimed at crack detection, magnetic flux leakage sensor of module combination is designed and developed. On the other hand, signal processing and collection circuit is designed and put up. Then the sensor and circuit make up the whole MFL detection system.On the basis of this, a defect recognition system based on BP neural network is proposed, which uses experimental signals as training samples to train the BP neural network, later defect parameters map to the experimental sample signals. Use the given defect leakage magnetic field to estimate the corresponding defect parameters,and the final errors between predictive results and actual results are within the allowable range, so the accuracy and reliability of the method are proved.