Research On Path Planning Of Arc Additive Manufacturing For Repairing Large Defects Of Casting

The repair welding of large steel castings is the most important part of the process.The process is complicated and has many influencing factors.In this paper,a finite element model of multi-layer multi-bead and single-layer multi-bead deposition was established to study the influence of layer method and the deposition path inside the layer on the temperature field and stress field in the process of arc additive manufacturing for repairing large defects of casting.Firstly,a CMT(Cold Metal Transfer)single-layer single-bead deposition experiment was conducted to study the appearance of the weld bead under different process parameters,and the process specification interval for excellent appearance was obtained.On this basis,the quadratic regerssion model between the process parameters(including deposition rate,wire feed speed,welding torch swing width)and depdsition dimensions(including the width and height of the weld bead)was established.It can be used to analyze the influence of deposition process parameters on the size of the weld bead.At the same time,it is also possible to estimate the size of the weld path at different deposition process parameters,thereby providing bases for path planning of robot.The large defects of the casting was simplified as a regular surface,and the finite element model of the multi-layer multi-bead deposition of the surface layering method and the plane layering method was established.the temperature field and stress field distribution in the multi-layer deposition process were studied.The temperature field and stress field distribution in the multi-layer deposition process with two methods of layers were contrastively analyzed.The results show that the heat dissipation conditions after the formation of the curved layered method was better than the planar layered method.Comparing the residual stresses formed by the two layered methods,it is found that the stress in the planar layered mode was small in the small area at the bottom of the curved surface,and the stress was less of the surface layered mode in most other areas.And the distribution is more gradual and there are no major fluctuations.The finite element models of single-layer multi-bead depostion on the plane and on the sphere were established,and the influence of the deposition path inside the layer on the temperature and stress fields were studied.The results show that when deposited on a flat surface,the stress value after forming the spiral scanning path was smaller,and the stress in the middle of the deposition layer was smaller,and the stress at the edge of the deposition layer was larger.The overall stress distribution of the long-side scanning path and the short-side scanning path was not much different,and the residual stress perpendicular to the deposition direction was greater than the residual stress parallel to the deposition direction.When deposited on a sphere,the stress at the bottom of the surface in the deposition metal is greater than the stress at the edge,and the stress distribution after the contour offset scan path was deposited was better than the parallel scan path.A multi-layer multi-bead deposition experiment and a single-layer multi-bead deposition experiment were conducted,and a tensile test was performed on the formed part.The results show that the formed parts of the curved layered method have better tensile properties than the planar layered molded parts.Better tensile properties parallel to the direction of deposition than perpendicular to the direction of deposition...