Simulation Of Machining Deformation Of Thin-walled Deep-cavity Frame Parts

With the development of science and technology,the demand of the quality of parts is increasingly higher.In order to meet the requirement of the weight reduction and the performance optimization,thin-walled deep cavity components are widely used in the aerospace,military,automotive and other industries due to the advantages they offer,such as low specific weights,high specific strengths.However,owing to their characteristics of thin wall,light weight,low rigidity,complicated structures,this type of part can easily deform during processing and manufacturing,which leads to high processing cost,long time consuming and difficult to make the machining accuracy meet the design requirements.Because the components have deep cavities,the overhang of the tool is large during machining,which leads to low rigidity.Therefore,the thin-walled plates and the tool can easily deform under the effect of the cutting force,which highly influences the overall part quality and processing efficiency,resulting in uneven wall thickness of the workpiece.And this may even cause the damage of cutting tools and machine,and the scrap of parts,which seriously affect the processing accuracy and processing efficiency.At present,most enterprises still take the traditional way to processing,use the process parameters which are based on the experience,and small quantities with multi-step cutting processing in the actual processing of such parts.After the completion of processing,the parts which do not meet the requirements are usually manually corrected by the fitter to reduce the error.As we all know,this method has great drawbacks,which will lead to long processing cycle,high production costs,as well as processing accuracy and quality cannot be a guarantee of stability.Therefore,the control of processing error and improvement of the accuracy of the thin-walled deep cavity parts has become a serious problem to be solved in the current processing industry.Based on the research of Shaanxi Province Natural Science Basic Research Project "NC Machining Error Simulation Technology",this paper uses 2A12 aviation aluminum alloy as the research material to forecast the deformation of precision machining of thin-walled deep-cavity parts.In this paper,the key technologies of numerical simulation of thin-walled deep cavity parts machining are studied by means of theoretical analysis,mechanics modeling and experiment.The numerical simulation and machining deformation prediction of the whole process of thin-walled deep-cavity parts are realized.And the particle swarm optimization(PSO)algorithm is used to optimize the milling process parameters,which provides a scientific basis for further rational development of process plan and control of machining deformation.Specific research content includes the following aspects:1.Three-dimensional numerical simulation of milling process.Based on the two-dimensional orthogonal cutting model and the three-dimensional oblique cutting model,the numerical simulation of the milling force is carried out for the peripheral milling process of the 2A12 aviation aluminum alloy material,and the milling force model of the spiral end mill which close to the real milling is established.At the same time,the key technologies of cutting machining simulation,such as material constitutive model,chip separation standard and tool-workpiece contact friction model,are established and analyzed.2.Numerical simulation of milling error of thin-walled deep cavity parts caused by the cutting force.A method of continuous dynamic error prediction based on finite element method is proposed.Considering the continuous feeding process of the tool,a kinematics equation of the milling cutter is established,and the corresponding mechanical parameters are obtained.Finally,the movement state of the tool can be obtained at any time.At the same time,considering the backlash deformation of the workpiece after the release of the cutting force,when the workpiece element was judged to be failed,the material is removed using Boolean algorithm.In order to solve the thickness deviation of the instantaneous cutting layer,the calculation of the milling force in the motion equation takes into account the influence of the deflection of the workpiece/tool system.The instantaneous cutting layer thickness error is corrected by interactive method,in turn to obtain the more accurate instantaneous milling force.Besides,according to the established finite element model,an actual milling verification is implemented.By comparing the simulation values with the experimental values,it is proved that the simulation method can realize the deformation prediction of the thin-wall deep cavity parts.3.Simulation of spring back deformation of thin-walled parts caused by removal of the clamping force.The spring back deformation of the thin-walled parts after the release of the clamping force is carried out and the quantitative calculation of the machining error is studied.Based on the analysis of the clamping force removal mechanism of the effect on the springback deformation of workpiece,the analytical model of the springback of the workpiece after the release of the clamping force and the machining error caused is established.The grid-based point mapping algorithm is used to obtain the workpiece processing surface before and after releasing the clamping force.Thus,the clamping force release error of the thin-walled workpiece can be calculated.And the accuracy of the method is verified by an experiment.4.Optimization of milling process parameters for thin-walled deep cavity parts.In order to reduce the milling error of thin-walled deep cavity parts,the milling parameters are optimized by multi-objective particle swarm optimization algorithm based on the machining error prediction model.The milling force and surface roughness were chosen to optimize the direction of the surface error.The cutting speed,the feed rate and the axial cutting depth were optimized.And through programming to generate the graphical user interface of milling parameters to optimization,which can easily achieve the different conditions of milling parameters optimization calculation.And the correctness of the optimization algorithm is verified by simulation.5.Numerical simulation of milling machining deformation of thin-walled deep cavity integral structure.Based on the thin-walled deep cavity part milling deformation prediction model,the numerical simulation and actual milling experiment of the whole part machining deformation of a real component with thin-walled deep cavity frame structure are carried out by using the milling process parameters obtained by the optimization method.The deformation rule of the milling of the frame class thin-walled deep-cavity parts is successfully obtained.Through expansion,the technology can be applied to the processing deformation prediction of a variety of frame-like thin-walled parts,which can provide a strong technical support to the parts processing technology.