Modeling And Numerical Calculation Method Of Temperature Field And Flow Field In Additive Manufacturing With Laser Coaxial Powder Feeding

Additive manufacturing with laser coaxial powder feeding is an advanced metal rapid prototyping technology.As heat source of the processing,laser has the advantages of stability,concentration,and adjustability.Due to the advantages of the coaxial powder feeding reduce consumables rate of the process.,this technology has application prospects incomparable with other technologies in the field of large-scale complex structure processing.However,it is difficult to control the influence of process parameters on the forming quality during the process of additive manufacturing with laser coaxial powder feeding.The temperature field and flow field in molten pool during the forming process have a significant impact on the forming quality,and the processing parameters cannot be predicted through pre-processing.Therefore,it is of great significance to use the simulation method to study the relationship between the process parameters of additive manufacturing,temperature field and flow field in molten pool.The main research work of this article is as follows:1)Establishing the temperature field model of Additive manufacturing with laser coaxial powder feeding based on cellular automata method.According to the layering and superimposing characteristics of the laser coaxial powder feed additive manufacturing process,the pre-processing of the cellular automata method is performed,including selecting the cell unit and cell neighbor type,setting the cell state attribute,and dispersion of time and space.Based on the mathematical difference of the Fourier heat conduction law and the energy governing equation,the cell heat conduction rules are obtained,and the boundary conditions at the gas-liquid surface and the solid-liquid surface are also considered.Based on the above content,a cellular automaton method of additive manufacturing temperature field model is established.2)Establishing the flow field model of molten pool in additive manufacturing based on cellular automata method.Based on the temperature field model,the flow mechanism of the molten pool fluid is analyzed,and five forces including gravity,surface tension at the gas-liquid interface,buoyancy,shear viscosity and pressure are summarized.Based on the mechanics of molten pool flow,the velocity conduction rules of the central cell in the X,Y,and Z directions are established according to the law of conservation of momentum to construct a molten pool flow field model.3)Carrying out the process research by experiment of laser coaxial powder feeding additive manufacturing process.Firstly,the experiment of designing nickel-based alloy powder in single-pass forming is conducted to study the effects of laser power,powder feed rate and other process parameters on the profile of the forming contour.The effect of energy ratio(energy per unit weight of powder)on the profile width and boundary angle is studied.Secondly,the experiment of 316 L stainless steel powder multi-layer forming was designed to study the effect of overlap rate and the number of scanning channels on the contour of the multi-layer single-layer forming.The experimental study of the above process parameters on the forming quality provides a theoretical basis for the analysis of the calculation results of the temperature and flow field models.4)Realizing the numerical calculation and visualization of temperature and flow field models based on C ++ and Matlab and analyzing the calculation results.According to the flow chart of temperature field and flow field algorithm designed by the model,the programming of temperature conduction rules and molten pool flow rules is implemented using C ++ programming language,and the calculation results are visualized and output through Matlab.The model parameters of temperature field and flow field are calculated by using the process parameters in experiment of additive manufacturing with laser coaxial powder feeding.Analyzing the changes of temperature field and molten pool flow field under different process parameters,including laser power,powder feed rate and laser scanning speed.At the same time,the temperature cycle curves at different positions of multi-layer single layer were analyzed and compared.The influence of laser power and powder feeding rate on the size of the molten pool is analyzed,which is of great significance to the actual process research.