Research On Weak Magnetic Detection Technology Of Weld Nugget Morphology

As a popular metal connection method,welding is widely used in automotive,aerospace and other industrial manufacturing fields.The penetration,welding width and welding height are important geometric parameters of the weld nugget,which is an important indicator to ensure the welding quality.Due to the complex structure and irregular shape of the weld zone,the current research on the weld nugget parameters has certain limitations.In view of this situation,this paper proposed a weld nugget size detection method based on weak magnetic technology,and developed related equipment.Firstly,the paper described weak magnetic detection theory of weld nugget size,and proposed the calculation method of weld nugget size in combination with Biot-Savar's law.Secondly,obtuse fillet welding,right fillet welding and lap welding were taken as research objects.The detection coordinate system was established in the weld cross section,and the mathematical model for solving the weld nugget parameters was established according to the geometrical characteristics of different welds.Thirdly,according to the overall functional requirements of weld nugget size detection,the overall plan of the nugget size detection system was designed.On the hardware side,the array sensor was designed to collect the weak magnetic signal on the surface of the weld,and the inclination sensor was designed to measure the angle between the weld surface and the horizontal plane.On the software side,applied the moving least square approximation to fit the curve of the nugget contour,and calculated nugget size by the established mathematical model,used the coordinate transformation method to draw the nugget contour curve.The detection system software was written to realize functions such as data acquisition,processing,storage,and dimensional visualization.Finally,for the obtuse fillet welding of Q235 material with an Angle of 120 degrees and 105 degrees,as well as the right fillet welding and lap welding of high strength steel material,the nugget size test was carried out and compared with the results of macroscopic metallographic method.The results show that This method is suitable for the measurement of different types of weld nugget sizes and has a good detection effect.This topic provides a new idea for the measurement of weld nugget size,which lays a foundation for the automatic inspection of weld nugget size in the future and has broad application prospects.