Study On Two-dimensional Micro-cutting Based On The Influence Of Tool-workpiece Rough Surface

Micro machining is a process of changing the surface and near surface properties of the material,the focus is not the whole material properties,but in microscopic friction contact characteristics and response characteristics of near surface materials.Because the micro cutting scale is small,the cutting edge of the blade edge radius and the actual tool-chip-workpiece surface characteristics have great influence to the micro cutting process which are closely related to the machined surface quality and the tool life.In this thesis,considering the tool-workpiece rough surface,tool-chip contacting surface,interaction between the asperities,the cutting edge radius,material elastic-plasticity theory and the thermal mechanical coupling,a two-dimensional model of micro-cutting aerospace aluminum alloy based on rough interface is established.From the perspective of microscopic thermodynamics and energy,the effects of rough contact interface on the stress concentration point,chip breaking position,chip shape and energy dissipation during the cutting process are analyzed.The results show that:in the micro cutting under two different contact interfaces,which are rough and ideal smooth,there are stress concentration points on the arc portion of the tool tip,however,the stress of the contact asperities under the rough interface is higher,that means greater stress concentration,which can easily cause fatigue damage and wear at the tool tip.Comparing the chip morphology under two different contact interfaces,it is found that the results obtained under the rough interface are more consistent with the literature experimental results.The position of the valley bottom of the rough surface of the chip layer will form stress concentration during cutting,and the position where the chip breaks mainly be these stress concentration points.The equivalent plastic strain,cutting force,temperature of chip bottom,and energy dissipation under the rough interface in the micro-cutting process are quite different from the ideal smooth interface.It can be seen that in the micro-cutting,the rough surface characteristics of the tool and workpiece should be considered due to the scale and machining accuracy.Under the influence of the rough contact interface,as the cutting speed increases,the chip morphology will transition from fragment to continuous chips,and the temperature of the rake face,the temperature of the bottom layer of the chip,and the growth rate of energy dissipation will also increase.Different tool rake angles have different squeezing state for the chips,so that the generated chips will transition from squeezing fragment chip to continuous chip with a radius of curvature,and the maximum tool temperature and surface node displacement will fluctuate with increasing rake angle.Because of the extrusion of the tool tip arc,the residual stress of the machined surface is mainly in the form of compressive stress under different cutting parameters.The results of the study have laid a certain theoretical foundation for improving the tool life,optimizing the tool design,exploring the frictional contact characteristics between the actual rough interface of tool-chip under microscopic conditions,and revealing the micro-cutting thermodynamic mechanism and micro-cutting essence.