Prediction Of Milling Force For Multi-tooth Tool Milling CFRP

Carbon Fiber Reinforced Polymer Composites(CFRP)parts are usually manufactured in near-net shape.In order to achieve the connection and assembly requirements,the machining operation of milling is required.Due to the non-homogeneity and anisotropy of CFRP,some defects such as delamination,burrs,and poor surface roughness can occur under the action of cutting force during the process of milling CFRP.Therefore,it is necessary to control the cutting force reasonably for reducing the generation of defects during the machining CFRP.The prediction of milling force for multi-tooth milling carbon fiber reinforced polymer is studied in this paper.In the process of milling CFRP,the cutting edge of the milling tool is divided into several micro-element cutting edges,and the micro-element cutting is regarded as oblique cutting.The finite element model(FEM)of oblique cutting UD-CFRP with different fiber orientations is established,and the cutting force coefficient is calibrated by the oblique cutting FEM.The cutting force coefficient is substituted into the micro-element milling force model,and the micro-element cutting force is obtained,which is transformed into the coordinate system of milling workpiece,and then the micro-element milling force is obtained.The micro-element milling force is integrated along a single cutting edge of multi-tooth tool,and then the milling force in all cutting edges of multi-tooth tool is superimposed to obtain the milling force involved in the milling process.The predictive curves of the milling force for milling UD-CFRP with different fiber orientations are obtained in one cycle.The research contents of this thesis are as follows:Firstly,the process of milling is regarded as a superposition of several micro-element oblique cutting processes.The cutting force coefficient is calibrated by the simulation of oblique cutting FEM.Based on the model of micro-element milling force,the prediction model of milling force for multi-tooth tool milling UD-CFRP is established.At the same time,the microscopic mechanism of cutting CFRP is studied.The microscopic finite element models of two-dimensional and three-dimensional cutting are used to reveal the failure modes of fibers under different fiber orientation angles.The experiment of orthogonal cutting UD-CFRP plates is adopted to verify the FEM,and the variation of cutting force is obtained from the experiment and simulation with different fiber orientations.Secondly,the finite element model of oblique cutting UD-CFRP is established to simulate the process of oblique cutting UD-CFRP with different fiber orientations.The oblique cutting UD-CFRP with the four typical fiber orientation angles(0°,45°,90°,and 135°)is simulated firstly,and the FEM is verified by the oblique cutting experiment.Due to the tool cutting edge inclination angle in process of oblique cutting,the cutting force is divided into three directions.Due to the action of the out-of-plane axial force,the damage of sub-surface and chip formation is different from those of orthogonal cutting.After the model of oblique cutting is verified by experiment,the oblique cutting UD-CFRP plates with multiple fiber orientation angles are simulated based on the FEM,and then the cutting force coefficients are calculated by the cutting forces from the simulation,and the relationship between the cutting force coefficients and fiber orientation angles is obtained.Finally,the cutting force coefficients are substituted into the prediction model of milling force,and the prediction curves of milling force are obtained in one cycle.The experiment of multi-tooth milling UD-CFRP is carried out to verify theoretical prediction of milling forces.The results show that the prediction of milling force is accurate and the method of prediction is feasible.At the same time,the finite element model of milling UD-CFRP is established,and the actual milling process is performed by the dynamic finite element simulation.Combined with the results from milling experiment,the variation rule of the machined surface roughness with different fiber orientation angles is studied.