Temperature Detection Of Friction Stir Welding Based On Infrared Fhermal Image

Since the friction welding technology was invented by the Cambridge Welding Research Association in 1991,this technology has attracted widespread attention from scholars at home and abroad.Friction stir welding technology is gradually emerging in aerospace,shipping,transportation and other industrial manufacturing fields.However,as the welding process itself is relatively tedious,the welding quality is often affected by various factors in the welding process.Among many factors,temperature is especially important.The temperature in the welding process will directly affect the growth process of metal grains in the welding seam,and then it will affect the molding quality of the welding material to some extent.If the welding temperature is too high,the grain size of the weld and the area around the weld will be enlarged.If the temperature is too low,the welding seam will condense into a block after the agitator runs,which will affect the forming quality of the welding seam and lead to welding defects.Therefore,it is very necessary to obtain the temperature distribution and variation law of friction stir welding.At this stage,the research on the temperature mechanism of friction stir welding mainly focuses on the theoretical part.There is a lack of research on the actual temperature in the welding process,and the changeable influencing factors in the welding process cannot be simulated by theoretical simulation.Therefore,it is necessary to detect and analyze the real temperature in the welding process to determine the welding parameters and improve the welding quality.In order to solve the above problems,the practical temperature measurement of friction stir welding is studied in depth in this paper.The specific research contents are as follows:Firstly,according to the friction stir welding equipment and infrared thermal imager,the temperature detection system of friction stir welding is designed,including temperature detection device and temperature detection software.The temperature detection system combines the principle of radiation,the theory of infrared temperature measurement and the principle of infrared thermal imaging.The temperature information of the welding process is initially obtained through the temperature detection device,and then the accurate temperature distribution is obtained through the temperature detection software.Secondly,the main factors affecting the temperature detection accuracy in the welding process are comprehensively considered: Aiming at the noise factor,this paper obtains the image frequency domain subband coefficient by non-subtractive contour wave transformation,and the improved threshold function is used to suppress the subband noise coefficient and then reconstructs the image to reduce the influence of noise.Aiming at the factors of detection distance and detection angle,this paper deduces and simplifies the temperature measurement formula of thermal imager,and obtains the temperature compensation formula related to the distance and angle.Aiming at the emissivity factor of the object,this paper conducts data fitting on the results of the measurement experiment of the emissivity of the welding material,and obtains the change relation between the surface emissivity of the welding material and the corresponding temperature,so as to improve the accuracy of the temperature by ensuring the accuracy of the emissivity.Finally,the temperature detection system designed in this paper is used to test the temperature of friction stir welding of aluminum alloy welding parts with different models and thicknesses.The feasibility and reliability of the proposed method for temperature detection of friction stir welding are verified.On this basis,the temperature distribution and variation of welding process are analyzed according to the experimental results.