Nondestructive Testing Technology Of Electromagnetic Acoustic Emission With Eddy Current Excitation

As a new nondestructive testing method, electromagnetic acoustic emission technology plays an important role in the detection of metal crack defects in pressure vessels. At present, the traditional electromagnetic acoustic emission technology is introduced into the test piece by using the direct loading pulse current. This method has some disadvantages, such as exciting current is too large, loading is not convenient, and the noise is large. In order to solve these problems, the eddy current loading power source is designed, and the local eddy current loading of the tested part is designed. Eddy current excitation power supply in the process of loading, the power supply of the excitation coil does not need to be in contact with the test piece, the load is more convenient and flexible.In this paper, the basic principle of electromagnetic acoustic emission technology is studied, and the eddy current loading power supply is designed according to the requirements of the project. The eddy current loading power source is a sine wave transmitter with adjustable frequency. Power supply using DDS(direct digital frequency synthesizer) module produces sine wave, the use of THS3091 chip design power amplifier module. In the control, the use of STM32 microcontroller as the system controller, touch screen as the system display and input module. STM32 MCU and touch screen using the serial port for communication.The part of software design mainly includes STM32 related program and touch screen program. Which using keil uvision4 design STM32 main program, serial communication program, timer program and data processing program; the VGUS configuration software development touch screen configuration design, configuration screen, design the corresponding interface.In this paper, the eddy current excitation electromagnetic acoustic emission testing platform is built by using the acoustic emission detector of American PAC company, and the related experiments are carried out by using the eddy current loading power source. The experimental results show that the eddy current loading method is used to detect the electromagnetic acoustic emission, which can accurately locate the position of the defect. At the same time, the eddy current loading power supply is stable, and the parameters are easy to adjust, which can solve many problems brought by direct loading, and can meet the requirements of electromagnetic acoustic emission detection.