Mechanical Model And Experimental Verfication Of NMQL Milling Of Aeronautical Aluminum Alloy

Aeronautical aluminum alloy is the main structure material of aircraft,rocket,spaceship and space station.Deformation and surface integrity of aeronautical aluminum alloy structural parts are the bottleneck of milling.The aeronautical aluminum alloy milling is through the cutting amount,material mechanical properties,machine tools and other parameters of collaborative control,to ensure the aeronautical aluminum alloy processing accuracy and surface quality.In particular,milling force is the decisive factor for material removal and workpiece surface integrity.However,because the milling force is the result of multi-parameter coupling of the process system,it is particularly important and challenging to establish the prediction model of milling force.Most of the existing milling force models are established in the traditional machining,which adopt the cooling and lubrication modes of flood and dry type.Among them,although the flood can effectively reduce the milling zone temperature,reduce the friction force between the tool and the workpiece,but its cutting fluid consumption is large,will cause liquid splash,affect the health of the operator,at the same time,serious pollution of the environment.In order to meet the current theme of clean and low carbon processing,the emergence of Nanofluid Minimal Quantity Lubrication technology provides a new way of production,which solves the problem of flood on the environment pollution and the technical bottleneck of insufficient MinimalQuantity Lubrication heat transfer capacity.However,in the milling process,the high-speed rotating milling cutter will disturb the surrounding air,produce radial flow,circumferential flow,return flow,etc.,and form a closed annular area around the milling cutter,which reduces the effective injection rate of cutting fluid into the interface between the milling cutter and the workpiece,and further weakens the cooling and lubrication effect of the milling area.According to the above problems,the flow field of cavity milling cutter under the constraint condition was analyzed by simulation and validated by orthogonal experiment to find the appropriate nozzle pose.At the same time,the empirical model and the instantaneous model of milling force of aviation aluminum alloy 7050 have been established under the condition of alumina NMQL,and the prediction system of milling force corresponding to the two models have been established.Specific works are as follows:(1)The simulation platform of airflow field on workpiece constraint interface of cavity milling cutter was constructed.The influence of milling cutter speed,helix angle and cavity shape on airflow field on workpiece constraint interface of cavity milling cutter was analyzed,and the nozzle posture(target distance,incident angle and elevation angle)in MQL milling cavity process is optimized.(2)The orthogonal experiment of the nozzle position in the milling of 7050aero-aluminum alloy cavity with NMQL was carried out.The effects of the three factors,target distance,incident Angle and elevation angle,on the milling force and roughness were analyzed,and the suitable position of the nozzle obtained by simulation was verified.(3)The instantaneous milling force model of integral end milling cutter under NMQL was established based on the double mechanism of the shear effect of front cutter face and the plough effect of back cutter face.The complex optimization design problem of milling parameters was decomposed into a relatively simple multi-stage condition evaluation problem by using the method of differentiating the milling cutter edge.A single factor experiment of instantaneous milling force coefficient was designed by introducing NMQL and milling feed factor into the instantaneous milling force coefficient.The waveform of numerical simulation instantaneous milling force was obtained,and compared with the measured one,the correctness of the simulation model was verified.(4)Design the NMQL milling 7050 aviation aluminum alloy of orthogonal experiment,using the four factors(spindle speed,axial cutting depth,the radial cutting depth and feed rate)four levels on the milling force experiment research,the effects of milling parameters on the three to the milling force,condition of nanofluids minimal quantities of lubricant is established the experience of the aviation aluminum alloy milling force model,Compared with the experimental results,it is shown that the predicted value by the theoretical formula is in good agreement with the measured value.(5)The prediction system of NMQL milling force was designed,and the instantaneous milling force prediction and the empirical model prediction were realized according to the milling parameters(spindle speed,axial depth,radial depth and feed speed)of the whole end milling cutter under the NMQL condition of 7050 aviation aluminum alloy.