Research On Electron Beam Welding Technology Based On ASAAC Standard Module Liquid- Cooled Airbone Rack

The operational performance of a fighter depends largely on the performance of the avionics system.In order to take the initiative in future wars,the integrated modular avionics system is the trend of the times.Therefore,the package density,module power and installation density of the line replaceable module(LRM)will increase sharply,which puts higher requirements on the heat dissipation performance of the airborne chassis/rack.The traditional heat dissipation method is mainly forced air cooling.However,with the successful application of the liquid cooling technology on the F-22 fighter jet,the liquid cooling technology has received unprecedented attention worldwide and quickly become the mainstream cooling technology of the integrated modular avionics system.China's avionics system cooling technology is relatively late compared to the Western industrialized countries,the foundation is weak,and innovative research is less,in the aspect of airborne chassis,mainly the forced air-cooled cooling of the substations is the main method,and the liquid-cooled technology is still in the research stage.Based on an integrated broadband airborne liquid-cooled rack developed and designed by a research institute,this paper carries out the secondary design of the process structure based on the analysis of its structural functions.Based on the welding test and finite element analysis,the materials,joint structure,welding process and welding sequence of the liquid cooling rack were determined.Research and analysis of the material design and weldability of aluminum alloy vacuum electron beam welding;An interfacial electron beam welding joint with a compact structure,strong anti-vibration and anti-impact ability and low process difficulty is designed and its electron beam welding process method is designed.Through analysis and comparison,the final decision was made for the use of heat treatable 6061 aluminum alloys for vacuum brazing of the upper,middle,and lower cold plates of liquid-cooled racks.High-strength 5A06 aluminum alloy is used for side plates,shunt side plates,and runner cover.Vacuum electron beam welding with high energy density,small heat affected zone and high weld strength between the cold plate and the(split)side plate and the shunt side plate and the flow channel cover plate.The intercommunication joint of the cold plate and the split side plate is designed as a hollow joint of the hollow structure,and the joint which only serves as a connection and meets the strength requirement can be designed as a solid joint.In this paper,the influence of electron beam welding process parameters on weld formation,stress deformation of liquid cooling rack and off-line programming of electron beam are further studied.When the other parameters are changed,the welding speed,the beam flow and the focusing current are changed,and the change of the focusing current has the greatest influence on the weld shape.The change of welding speed or welding beam has little effect on the weld appearance,which is mainly reflected in the change of welding depth.The faster the welding speed,the smaller the penetration depth;the larger the welding beam,the greater the penetration depth.The welding sequence was optimized by numerical simulation of the split side plates and the rack.At the same time,the simulation results showed that the peak value of the equivalent welding residual stress did not change significantly with the increase of the heat input,but the high stress area increased significantly and the residual stress in the farther region from the weld increases significantly with the increase of heat input.As the de-stressing temperature of the heat treatment increases,the residual stress level of the residual welding of the rack decreases.The off-line programming research for the shunt side panel shows that the MASTERCAM software can automatically generate the path G code,and the workpiece coordinate system conversion based on these G codes can quickly and efficiently and accurately prepare various complicated welding trajectories.