Research On Grinding Force And Removal Mechanism Of Single Grain In Ultrasonic Vibration Assisted Grinding

With the increasing difficulties of machining precision and ultra-precision components,traditional machining methods can't satisfy the actual needs with the shortcomings such as low efficiency and poor machining qualities.Ultrasonic vibration assisted grinding,as a combination of ultrasonic vibration machining and conventional grinding,is a new kind of composite processing method which has the advantages such as high machining qualities,small cutting force.It is widely used in precision machining of hard-cutting materials.Single grain's micro cutting process is the basis of grinding wheel's macro cutting process.The way to study the mechanism of grinding through single grain's micro cutting process has been proven to be effective.In this paper,a device for ultrasonic vibration assisted grinding with single grain was designed and the ultrasonic vibration was applied on single grain in axial direction.Under the conditions of ultrasonic vibration assisted grinding and normal grinding,single grain's cutting force and material's removal mechanism were researched systematically through theoretical analysis and experiments.The scratches generated by single grain on workpiece under the condition of ultrasonic vibration were sine curve and interlaced.These under the condition of normal grinding were straight lines and distributed equidistantly.Single grain's motion equations and instantaneous velocity equations were built up.Meanwhile,the expressions about cutting path length and grinding ratio of single grain were obtained.The single grain's special processing characteristics were analyzed and the phenomenon that axial ultrasonic vibration causing the transformation of side faces and cutting edges of single grain was found.The effects of grinding parameters and grain sizes on cutting force of single grain were studied by orthogonal experiment and the optimal combination of grinding parameters was obtained.The comparison of grinding force ratio under two kinds of conditions was made.The wear patterns were observed and the connection between grinding force and the volume of wear was quantitatively analyzed.With the volume of wear increasing,the grinding force was becoming big.It was concluded that ultrasonic vibration changed the contacting status between single grain and workpiece and the cutting force was reduced.The influence of grain size and grinding depth on the law of material removal mechanism was researched.On the one hand,as the grain size becoming big,the proportion of brittle fracture removal increased gradually.Ultrasonic vibration reduced the proportion of brittle fracture and increased the proportion of the plastic deformation,which all contributed to the improvement of workpiece's surface quality.On the other hand,with the increase of grinding depth,the percentage of brittle fracture removal was increasing.When plastic material was grinded,ultrasonic vibration made the width of scratch bigger and the height of apophysis lower and the surface quality of workpiece was improved.