Study On Surface Morphology Of Vibration-assisted Machining

Vibration-assisted machining has unique advantages over traditional machining methods and has been widely used in the machining of various materials,such as ductile materials,brittle materials,composite materials,and even biological tissues.It is well known that the surface morphology of the machined parts directly affects their performance and service life,but there is a relative lack of research on the surface morphology of the machined parts after vibration-assisted machining.Therefore,this paper investigates the surface morphology of the machined parts after vibration-assisted machining based on different research methods for typical brittle materials and plastic materials,with the aim of applying this technology to material machining in a better and more efficient way.For the surface morphology of the machined parts after vibration machining of brittle materials,this paper reviews and summarizes the relevant research at home and abroad.It is found that the existing research mainly focuses on two-dimensional elliptical vibration machining or one-dimensional vibration machining in a single direction,and there are relatively few studies on the surface morphology after vibration machining in different directions.Therefore,in this paper,the effect of different ultrasonic vibration（UV）directions on the surface morphology of the brittle materials in ultrasonic vibrationassisted scratching（UVAS）is investigated by using finite element simulation and experimental methods with a typical brittle material（RB-SiC）and compared with conventional scratching（CS）.Further,based on the finite element simulation,the effect of vibration parameters on the surface morphology of RB-SiC in each UV direction and the mechanism are investigated.The results show that:（1）in the UVAS,the UV in xdirection leads to a smaller groove width than the CS,the UV in y-direction leads to a larger groove width,and the UV in z-direction leads to a larger groove depth;（2）after the CS,the bottom of the groove is messy and irregular,but after vibration machining,the bottom of the groove in different directions presents different regularities;（3）the UV in x-direction produces the best surface quality,the UV in y-direction leads to periodic laminar fractures at the bottom of the groove and extends to the sides of the groove to form shell-shaped fractures,and the UV in z-direction causes block fractures with higher frequency and smaller shape;（4）the increase of vibration frequency and amplitude can contribute to the reduction of cutting force;（5）in the UVAS,the depth and width of the grooves depend more on the amplitude than on the vibration frequency.Specifically,the greater the amplitude of the UV in the y-direction,the greater the width of the groove,and the larger the amplitude of the UV in the z-direction,the larger the depth of the groove.For the surface morphology of the machined parts after vibration machining of plastic materials,this paper summarizes and analyzes the existing surface morphology models.It is found that the surface morphology models are getting better,but the existing models do not consider the influence of the rake face and flank face on the machined surface generation.Therefore,in order to further improve the surface topography model to enhance its prediction accuracy,a new two-dimensional surface topography model in the orthogonal plane,i.e.,the surface residual height model,is developed in this paper.In the specific development of the model,a tool contact trajectory based on the circular family envelope principle is established,the critical cutting direction angle is redefined,and then the effects of the flank face,rake face,flank face and rake face together on the final surface residual height are analyzed.In addition,the material rebound,waviness of the tool cutting edge profile and residual errors are also considered in the model.Subsequently,the proposed model is validated by finite element simulation,and the results show that the total residual height values obtained from the simulation and theory are in good agreement,with a maximum relative error of only 9.1%.In addition,the residual height values obtained from the existing model are compared with the residual height values obtained from the model developed in this paper by fixing the calculation parameters.It is found that the non-extruded residual height values from the model developed in this paper are exactly the same as those obtained from the model previously proposed by Zhang et al.,which again confirms the accuracy of the model developed in this paper.