| Particle-reinforced Titanium Matrix Composites,as a new type of lightweight structural material,have mechanical properties such as high specific strength,specific stiffness,fatigue resistance,wear resistance,high temperature resistance and corrosion resistance,and have broad application prospects in important fields such as aerospace,automotive and medical devices.However,the introduction of the reinforcing phase makes titanium matrix composites possess the difficult processing properties of poor thermal conductivity,small deformation coefficient and elastic modulus of the matrix material titanium alloy,as well as the characteristics of high hardness and high brittleness of the reinforcing phase material.In the process of machining,it is easy to have difficulties such as serious tool wear,short tool life,poor machining surface quality and serious hole defects.For this reason,this thesis investigates the cutting performance,particle breakage and surface defect distribution of titanium matrix composites with different volume fractions in terms of cutting surface formation mechanisms,mainly including.(1)The effects of the reinforcing phase content and cutting speed on the cutting force and cutting temperature were investigated and analysed.The results show that the reinforcing phase has a significant effect on the cutting force and cutting temperature,and the cutting force of 8%PTMCs increases by 30%compared to 5%PTMCs.The depth of cut resistance F_p increased by 21.82%,the feed resistance F_f increased by 21.82%,the main cutting force F_c increased by 10.73%and the cutting temperature increased by31.32%.Secondly,with the increase of cutting speed,the cutting force increased,the cutting speed from 15m/min～30m/min,the cutting force increased steeply,when v_c=30m/min,there is an inflection point,30m/min～150m/min,the cutting force increase tends to level off.(2)The Ti C was set as an ellipse with the long-short axis ratio of 2:1,and the two-dimensional cutting simulation of particle-reinforced titanium matrix composites containing Ti C particles was established.The mechanism of particle influence on cutting force during cutting process and the mechanism of crack sprouting and expansion of reinforced particles during cutting process until they fall off,thus forming hole defects on the machined surface,is revealed.The angle between the long axis of the particle and the positive direction of the X-axis is taken as the standard,and different tilt angles are set to explore the breakage of the particle under different tilt angles.And the effect of tool cutting path on particle breakage and machined surface was investigated with the center of ellipse as the reference.(3)Combined with 3D video microscopy and SEM,the influence law of particle reinforced content and cutting speed on surface roughness was investigated.The simulation experiments of particle breakage under different inclination angles and different cutting paths are verified,and the results show that the experiments are consistent with the simulation results and the simulation is realistic.The surface defect distribution in the peaks and valleys in the cutting path is investigated,and the effect of cutting speed on it is analyzed,which further reveals the formation and distribution of surface defects in the processing of particle-reinforced titanium matrix composites and provides experimental support for the next stage of surface defect suppression and the realization of an efficient and low-damage processing process.The research results of this thesis are helpful to solve the technical problems of severe surface defects,low processing efficiency and burned surface in the cutting process of particle-reinforced titanium matrix composites,and provide basic theoretical support for further realization of high-efficiency and low-damage cutting and processing process,which has a positive effect on improving the processing technology level of particle-reinforced titanium matrix composites and its application and promotion in actual engineering. |
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