Cutting Force Modeling Based On Oblique Cutting Model In Hard-machined Material Curved Cutting Process And Cutting Parameters Optimization

Hard-machined materials have wide applications in weapons,vehicles,aviation,aerospace and other field.During cutting process of hard-machined materials,contour turning and curved geometry end milling are common machining processes.Due to changes in the curvature of the workpiece contour curve,cutting force varies during the cutting process,and mutations occur sometimes.In order to avoid the impact load between cutting tool and workpiece,the actual cutting parameters are chosen conservatively,thereby reducing machining efficiency,increasing energy consumption,and machining cost,which becomes the bottleneck of the development of the cutting technology.This paper established two cutting force models for contour turning and curved geometry end milling,respectively.The cutting parameters were optimized,and a hard-machined material curved cutting database system was designed and established.The main contents are as follows:(1)Research on cutting force modeling for contour turning process.Based on the concept of equivalent cutting edge,a cutting force model considering the influence of tool nose arc was established.According to the variation of contour curvature,the tool-workpiece geometry contact area evolution process at different cutting depths was investigated.B-spline curve method was used to parameterize the cutting edge and the workpiece contour curve,and Green algorithm was utilized to calculate a simply connected region cutting lay area,and polar coordinate differential element method was taken to calculate the direction angle of equivalent cutting edge.A uniform geometric parameters model was established,which could solve the condition when irregular geometry of the contact area occurs,while it could not be tackled by a common model.An oblique cutting model based on the principle of maximum shear stress was established to analysis the constrains relationships among cutting model coefficients,force vector,velocity vector and chip flow vectors,and a shear coefficient calibration method was proposed.The calibration tests of cutting force coefficients was conducted by turning a straight-line approach,and studied the influence of cutting lay area on cutting force model coefficients.A contour turning test was designed,and investigated the influence of the curvature of the curve on cutting force so as to verify the cutting force model.(2)Research on cutting force modeling for curved geometry end milling process.Based on Fourier series expansion,a cutting force model considering the influence of instantaneous feed direction was established.The tool trajectory was discretize,an equivalent feed calculating approach based on constant and variable radial depth of cut was proposed.A variable radial depth of cut geometrical model was established,and cut-in and cut-out vectors calculation method on three phases,i.e.,cutting in,continuous cutting,and cutting out,were proposed.An oblique cutting model based on the principle of minimum energy was established to analysis constraints relationship among cutting force model coefficients,force vector,velocity vector and chip flow vectors.A calibration method for cutting force model coefficients was proposed.The method can be completed based on just several testes for cutting force model coefficients calibration,which could reduce the workload of calibration tests and improve the efficiency of the calibration.Milling straight-line approach was used as cutting force coefficient calibration tests,and the influence of instantaneous undeformed chip thickness on cutting force model coefficients was studied.The constant radial depth of cut and constant curvature curved geometry end milling tests,and varying radial depth of cut and varying curvature curve end milling tests were designed,the influence of radial depth of cut and curvature curve on cutting force was investigated so as to verify the cutting force model.(3)Research on the improvement of knowledge-based multi-objective optimization algorithm and cutting parameters optimization technology.Based on knowledge multiobjective optimization algorithm,situational knowledge,normative knowledge and topographical knowledge were utilized,and expanded the space diversity of the population so as to enhance the algorithm performance.As for curve turning and curve end milling process,the improved algorithm for the optimization of cutting parameters was used based on the multi-objective functions of energy efficiency and processing costs,and it could provide theoretical guidance and technical support to optimize decision-making process.(4)Design and implementation the hard-machined materials curved cutting database system.The overall system architecture and database system function structure of the hardmachined materials cutting database system were designed,and the data physical structure model was constructed for cutting objects.Prototype system development was conducted based on B/S structure,and the main function of cutting data services and process knowledge services were achieved.Taking the prediction of contour turning force and turning parameter optimization for example,the system was verified.