Research On Variable Groove Recognition And Weld Formation Of Rotating Arc Narrow GAP Welding

As a high efficiency welding method,Rotating arc narrow gap welding has been widely used in medium plate welding.To ensure welding quality,it is necessary to do some researches on weld formation.The traditional arc sensor and passive vision sensor are easily influenced by the shape of the bottom slope during the sensing process,which causes tracking precision error and affects the weld formation.Therefore,it is necessary to use the active visual sensing technology to extract the shape of the workpiece,and to lay a foundation for the control of welding quality by studying the forming rules of different groove shapes.First,in order to overcome the shortcomings of the previous sensing technology which is easily affected by the shape of the slope,the active optical vision sensing technology was used to identify the groove shape in front of the welding.According to the characteristics of narrow gap welding,a groove morphology extraction algorithm that suitable for narrow gap welding was proposed.Aiming at the problem of large computation of the whole image,an automatic ROI algorithm that using arc location to determine the position of laser stripe was proposed;the laser stripe region was automatically extracted through double-threshold based on the difference among the arc pixel value,the laser stripe pixel value and the background pixel value,this ROI algorithm can accurately extract the region of the laser stripe.Aiming at the problem of spattering,we compared the size of the laser stripe and the circumference of the splash contour to remove the smaller splash,the algorithm can effectively remove splashes scattered around the laser stripe.Then,the parallel thinning method was used to refine the laser stripe and complete the extraction of the feature points of the laser stripe.Finally,the accuracy of the visual algorithm for horizontal width of narrow gap was within 0.5mm,and the recognition accuracy of vertical depth was less than 0.8mm.Then,welding experiments with four different groove shapes were carried out.The experimental results showed that the groove shape influences the weld formation.Under the same rotation radius,the V groove was easier to get the bottom penetration than the I groove,and the bottom of the V groove had an inverted cone shape.Under different rotation radius,the side wall penetration under large rotation radius was deeper,and the thickness was 1.5mm smaller than small rotation radius.Finally,two equivalent heat sources were designed by ANSYS software,and the numerical simulation of weld formation under different rotation radius was carried out.The results of comparison between simulation result and experimental result showed that the distribution of temperature field and thermal cycle curve could match the experimental result well,and this simulation could provide a reference for future welding experiments.