Research On Ultrasonic Vibration Assisted Mill-grinding Technology Of Three-dimensional Needled C/SiC Composite

C/SiC composite is a new type of composite made of silicon carbide as the matrix and carbon fiber as reinforced phase.It has a series of excellent properties,such as high specific strength,high specific mold,high temperature resistance and high temperature chemical stability.It has been widely used in various fields at present.However,as a representative of typical refractory materials,high strength,hardness and anisotropy of materials cause many difficulties in traditional machining.In this paper,the ultrasonic vibration technology is introduced into the traditional machining.The longitudinal vibration and the horizontal vibration along the feed direction were applied to the C/SiC composite workpiece.The grinding force,the machining defect,the tool wear and the surface roughness were compared.Ultrasonic vibration assisted mill-grinding is more conducive to improving the machined surface quality of C/SiC composites.The research results have theoretical guiding significance and engineering application value for high performance machining of C/SiC composite.Based on the single particle trajectory of traditional mill-grinding,the kinematic expressions of three kinds of ultrasonic vibration assisted mill-grinding single abrasive particles were established.The grinding characteristics of three different vibration modes were compared and studied through the Matlab simulation of the movement trajectory of the abrasive particles,and the best one-way vibration mode wasoptimized.The research showed that the ultrasonic vibration assistedmill-grinding along the feed direction and along the longitudinal vibration could achieve the intermittent machining of the cutting tool and the material.So these two machining methods are available for machining the C/SiC composite.At the same time,the simulation analysis of the assisted mill-grinding C/SiC composites under the different processing mode of single abrasive grain was carried out.It was concluded that the grinding force in the grinding process could be reduced by the ultrasonic vibration assisted mill-grinding and the longitudinal ultrasonic vibration assisted mill-grinding along the direction of the feed.At the same time,the grinding effect of the two kinds of vibration assisted mill-grinding was improved,and the grinding effect was focused on the feed vibration.The shear stress was reduced,while the longitudinal vibration was more prominent in improving the surface quality.The contrast experiments of the assisted mill-grinding along the feed direction,the longitudinal ultrasonic vibration assisted mill-grinding and the traditional mill-grinding C/SiC composites were designed,and the grinding forces under the three machining methods were studied and the variations of the three grinding forces with each grinding factor were discussed.The results show that the grinding forces of the two kinds of ultrasonic vibration assisted mill-grinding were obviously less than that of the traditional mill-grinding,and the grinding forces decreases more remarkably when the ultrasonic vibration assisted mill-grinding along the feed direction,which was in accordance with the simulation results.The relationship between the grinding forces and the grinding factors was:with the risen of the spindle speed,the three direction grinding forceswere both reduced,with the risen of the feed speed and the grinding depth,the three direction grinding forceswere both risen;and with the risen of the ultrasonic amplitude in a certain range could reduce the grinding forces,but the continuous increasing of the amplitude will lead to the increasing trend of the grinding forces.Through the analysis of the surface defects and tool wear of the C/SiC composite material after three kinds of machining modes along the feed direction ultrasonic vibration assisted mill-grinding,the longitudinal ultrasonic vibration assisted mill-grinding and the traditional mill-grinding,it was concluded that two kinds of ultrasonic vibration assisted mill-grinding could not only reduce the machining defects,get good surface quality,but also can improve tool weareffectively,extend tool life.The surface roughness changes situation of C/SiC composites were studied by single factor experiment under three different processing modes and the response surface experiment under the assisted mill-grinding of longitudinal ultrasonic vibration.The experimental results showed that the two kinds of ultrasonic vibration assisted mill-grinding could reduce the machined surface roughness,and the longitudinal ultrasonic vibration decreased more significantly.With the risen of the spindle speed,the surface roughnesswasreduced;with the risen of the feed speed and the grinding depth,the surface roughness was increased;and with the risen of the ultrasonic amplitude in a certain range could reduce the surface roughness.At the same time,it was concluded that the important degree of the influence of the grinding factors on the surface roughness was the following:the grinding depth was the largest,the spindle speed was second,the feed speed wasagain,and the ultrasonic amplitude was the least.