Development Of Eddy Current Sensor For Surface Defect Detection Of Welds

As a common processing method,welding is widely used in all walks of life.Since the welding process is easily affected by the external environment,this will cause surface defects such as depressions,undercuts,cracks(surface),arc scratches,and residual fractures on the weld surface.At present,in the detection of weld surface defects,the traditional contact detection method has some shortcomings of slow inspection and easy scratching of the surface;the commonly used non-contact inspection method also has limitations in detecting complex shapes and large weld surfaces.Therefore,in order to realize online weld surface defect detection,it is of great practical significance to launch the development of eddy current sensors for surface defect detection of welds.Firstly,this paper analyzes the equivalent circuit of the eddy current displacement sensor based on the basic theory of electromagnetic field.The finite element simulation analysis of the designed sensor probe is carried out by using ANSYS Maxwell simulation software,and the accuracy of the finite element simulation results is verified by experiments.Afterward,the influences of coil excitation frequency,detection inclination angle and surface defects on simulation eddy current density and magnetic induction intensity are further studied.Then,the hardware structure of eddy current displacement sensor is studied,each circuit module of eddy current displacement sensor is designed,and a prototype of eddy current displacement sensor is manufactured.The eddy current displacement sensor was developed in real time by using the ordinary least square method and the single-chip microcomputer program.In order to verify the effect of temperature compensation,the linearity of the compensated eddy current displacement sensor is tested;The test results show that the sensor after temperature compensation has good linearity,and the linearity error at room temperature is ±0.242%,which is lower than ±1%in the market.Finally,based on the developed eddy current displacement sensor,the overall inspection system was designed for the purpose of detecting the surface defects of the weld seam.The overall detection system is preliminarily designed,and the experimental platform was built on the basis preliminarily of this design by planning the motion trajectory of the manipulator and designing the surface contour acquisition system.The eddy current displacement sensor can be combined with the manipulator and applied to the detection of weld surface defects.In order to verify the rationality and accuracy of the detection results,the METRASCAN 750-R^TMnon-contact 3D laser scanner was used for verification.