Study On Temperature Measurement Model Of Friction Stir Welding Core Area

Friction stir welding technology was born in 1991 at the Cambridge Welding Research Association in the UK.This technology has brought another welding revolution in industrial manufacturing field since laser welding.Once discovered,this invention has been widely concerned by scholars at home and abroad,and has shown great application prospects in the fields of aviation,aerospace,shipbuilding,nuclear industry,transportation and other industrial manufacturing.The welding process is a very complicated process.The welding temperature will directly affect the growth process of the metal grains in the molten pool,which will affect the phase transformation of the base metal.If the welding temperature is too high,the grain size of the heat engine affected area(TMAZ)will be coarse.If it is too low,the molten pool will condense too fast,affecting the quality of welding and easy to produce defective products.Therefore,it is necessary to obtain a friction stir welding temperature distribution.At this stage,the research on the temperature field of friction stir welding mainly focuses on the temperature distribution of the surface of the friction stir welding material outside the contact area between the stirring head and the welding material during the friction stir welding process.There is a lack of research on the temperature field in the core area of friction stir welding,especially on the surface of the welding material under the shoulder.This will inevitably affect the selection of welding parameters,thereby affecting the quality of welding and reducing the reliability of welding products.In order to solve the above problems,the temperature field in the core area of friction stir welding is studied in depth in this paper.The specific research contents are as follows:Firstly,on the basis of studying the heat transfer theory of metal welding deeply,the heat transfer mode of friction stir welding core area is analyzed and assumed by using Fourier law,and a heat transfer model of friction stir welding is proposed.Secondly,the contact model(GW model)of the smooth plane and the nominal flat rough surface is introduced to determine the boundary conditions of heat transfer in the core zone of friction stir welding.The heat transfer model in the core area is solved,and the expression of the surface temperature gradient in TMAZ is obtained by using the Gauss integral algorithm.According to Sterling-Boltzmann's law,the surface emissivity of aluminum alloy welding material is recalibrated.Based on the theory of radiant heat exchange,the relationship between the surface temperature of welding material in the core area of friction stir welding and the surface temperature of welding material in TMAZ is determined.On the basis of this relationship,the numerical solution of the temperature gradient in the core area is obtained based on the temperature measurement principle of the infrared camera.Finally,according to the established model,the numerical solution is simulated and analyzed by the simulation software of Matlab,and the variation characteristics of temperature gradient in the core area of friction stir welding is obtained.At the same time,the numerical solutions presented in this paper are compared with the experimental measurements of other scholars to verify the correctness and feasibility of the calculation model.