| Under the background of energy conservation,emission reduction and efficient manufacturing,the development of hybrid wire arc additive and milling subtractive manufacturing technology can better meet the needs of green sustainable development,rapid design and processing of modern manufacturing industry;Facing the requirements of high-efficiency and high-precision on-line maintenance support for the damage site conditions of large transmission shafts,gears and racks and other metal parts of ships,aircraft carriers and armored vehicles,the development of hybrid wire arc additive and milling subtractive manufacturing technology is one of the effective ways to meet the logistics support requirements of military equipment.The hybrid wire arc additive and milling subtractive manufacturing takes the arc as the heat source carrier to realize the melting combination of base metal and solder;in the process of wire arc additive forming,the forming efficiency,quality and cost of metal parts are closely related to the temperature distribution;the service life of cutting tools,the surface finish and quality of parts are also closely related to the temperature distribution.Therefore,the paper studies the hybrid wire arc additive and milling subtractive manufacturing from the perspective of temperature distribution in the manufacturing process.Firstly,based on magnetohydrodynamics the two-dimensional axisymmetric transient finite element model of wire arc additive forming was established and solved by using multi-physical field simulation software Comosl Multiphysics.Considering the heat transfer between arc and substrate,welding wire and environment,and taking the optimized wire arc cladding process parameters as the input,the formation of energy and the temperature distribution in the molten pool during the arc starting process were analyzed.Through the analysis of finite element simulation results,the effects of wire dry elongation and arc length on arc energy distribution and the distribution of arc and substrate temperature were obtained.The results show that the arc forms a "broom" shape in space,the arc length only affects the spatial distribution of the arc,does not affect the maximum temperature of the arc,and the dry elongation of the welding wire has little effect on the temperature of the arc and the substrate;when the dry extension of the welding wire is 15mm and the arc length is 5mm,the penetration depth of the molten pool is about 2mm and the diameter is about 5mm.Secondly,the simulact.welding was used to establish the three-dimensional temperature distribution models of single layer,single layer and multi-channel on flat plate and single layer and multi-channel on circular plate;using the optimized wire arc process parameters and Goldak heat source,the dynamic temperature distribution of the substrate under various arc additive conditions,such as single-layer single pass,single-layer ten pass stacking forming and circular single-layer three pass stacking forming,was studied.Through the simulation results,the effects of forming direction and inter pass cooling time on temperature distribution were analyzed.The results show that the forming direction has a certain influence on the temperature distribution,and the parameter that has a great influence on the temperature distribution is the inter pass cooling time;the cooling time between ten forming passes of single layer on flat plate is about 9.6s,and the cooling time between three forming passes of single layer on circular plate is about 40s,which is more convenient for subsequent milling.Thirdly,based on the heat conduction equation and finite difference method,a fast solution algorithm for the temperature distribution of arc additive forming was designed.The temperature distribution of single-layer single pass linear weld stacking forming on the flat plate was quickly calculated by Gaussian heat source and double elliptical heat source,and the calculation results were compared with the simulation results of finite element software.The comparison results show that the calculation results of the finite difference algorithm are consistent with the finite element simulation results,and there are some errors.When the finite difference algorithm is used to calculate the temperature distribution of single-layer single pass linear weld stacking forming,it is more suitable to use double elliptical heat source.Finally,the experimental system of hybrid wire arc additive and milling subtractive manufacturing was built,and the single-layer single pass forming experiment,single-layer forming substrate temperature distribution experiment,warm milling experiment and typical part repair experiment were designed and completed.The optimum wire arc additive process parameters were obtained by orthogonal experiment.The experimental results show that under the welding process parameters of 20V welding voltage,120A welding current and 500mm/min motion speed,the height difference between the head and tail of the formed weld is uniform,the variation consistency between passes is good,and the overall forming is uniform and flat;the experimental results of temperature distribution in arc cladding process are in good agreement with the numerical simulation results,which verifies the effectiveness of the established numerical analysis model;On this basis,the repair process of typical parts is formulated,and the repair experiment is carried out to verify the feasibility of the process.In this paper,the method of combining commercial finite element software simulation,selfwritten algorithm solution and experimental verification was used to study the arc temperature distribution,substrate temperature distribution,and temperature milling at different temperatures in the hybrid manufacturing of arc cladding additive and subtractive materials.Appropriate combination of arc cladding additive and subtractive materials mixed processing process parameters will lay the foundation for future research on the fusion mechanism of shape control and hybrid manufacturing. |
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