Physical Modeling Of Cutting Processes And Study On Cutting Technology Of Aluminum Honeycomb Core Material

With the rapid development of modern aviation technology,honeycomb core sandwich composite material has become one of the fourth largest aviation structural materials immediately after aluminum,steel and titanium.Compared to other traditional metal materials,the biggest advantage of honeycomb core sandwich composite materials is its high specific strength and specific stiffness.The strength and stiffness of this material can be significantly enhanced is with the cost of a very small weight increase.However,the machining process of honeycomb core material is also different from that of traditional metal materials.It brings new challenges to the field of cutting in all aspects such as clamping design,cutting process simulation and physical modeling,processing quality evaluation and low defect process optimization.And this is mainly because the honeycomb core material has unique topology,anisotropic mechanical characteristics and the weak rigidity in-plane.Therefore,this paper will start from the structural characteristics of honeycomb core materials,develop the new clamping device based on honeycomb core thin-walled porous structure,study mechanical model and heat transfer model and cutting quality evaluation methods and propose a new process optimization strategy,the main work is as follows:Based on the structural characteristics of aluminum honeycomb core material,this paper studied the following six aspects: clamping device design,cutting process simulation,cutting mechanics modeling,temperature distribution modeling,experiment research and surface quality evaluation,and processing technology optimization.A full range of research work on cutting technology of honeycomb core material was carried out.(1)Based on the structural characteristics of honeycomb core,this paper put forward the ice freezing clamping method based on the rapid thermoelectric cooling technology of semiconductor.It not only achieved the machining clamping of the honeycomb core workpiece,but also increases the in-plane rigidity of the honeycomb core material.This paper confirmed the clamping reliability of the ice freezing platform by means of structural design,theoretical analysis and experimental verification,and provides the clamping foundation for the subsequent experimental research and application.(2)The mechanism of chip formation and removal of honeycomb wall was studied by cutting simulation,and based on the single honeycomb wall cutting process,a multi-element composite cutting force model of honeycomb core was established.The effects of different honeycomb wall entrance angle,tool structure and cutting parameters on the honeycomb wall cutting process were studied.The effects of different cutting angles on the cutting force,cutting deformation,chip formation,honeycomb wall deformation and processing crack were compared and analyzed.Based on the time-varying characteristics of the entrance angle of each honeycomb wall and the topology of honeycomb core material,this paper established a multielement composite cutting force prediction model and verified the accuracy of the model by the honeycomb core cutting force experiments with different parameters.(3)Considering the spatial structure of the honeycomb core material,an anisotropic threedimensional equivalent heat transfer model was established,which contains heat conduction and thermal convection.Based on the honeycomb core combination milling cutter,the moving surface heat source of the hogger cutter and the line heat source of the circular blade were proposed.And the temperature distribution prediction model of the honeycomb core workpiece based on the two heat sources was established.The temperature distribution prediction model was validated by the honeycomb core milling temperature experiments.Finally,the temperature distribution of the honeycomb core during the milling process and the heat affected zone were studied.It was found that the milling temperature of the honeycomb core was maintained at a high temperature in the tool area,and drastically decreased out the tool area,and the heat affected area of the combined milling cutter was studied.(4)This paper studied the cutting force,temperature,and surface defect characteristics of under conditions of different cutting tools and cutting parameters,proposed a statistical classification and evaluation method for typical processing defects of honeycomb core material,disscused the topographical characteristics of various types of defects and produce typical conditions,and comparative analysed the intrinsic relationship between the force and heat and the processing defects.The effect of spray water mist and ice filling auxiliary treatment on the quality of honeycomb core processing was analyzed.It was found that spray mist treatment had a significant effect on the combination milling cutter under the whole test parameters and the integral-type cutting tool under a small milling depth.Based on the research on the distribution of the entrance angle of the honeycomb core milling surface defects,the concept of "reverse milling area advantage" of honeycomb core material milling quality was put forward.According to the statistical research,it was found that the distribution of honeycomb core milling defects was concentrated in three regions.For the defects of regular distribution,the low defect optimization method for all the honeycomb walls to avoid the three concentrated regions was established.For the defects of irregular distribution,the cutting method optimization method was proposed to reduce the cutting force and cutting temperature based on the removal rate of the material.Finally,the conditions of keeping the joint milling surface and the side milling surface free of defects were studied.