Experimental Study On Serrated Chip And Cutting Force In High Speed Cutting Of Ti6Al4V

Titanium alloys are widely used in aerospace,weapons and other fields because of their superior properties.But its machinability is poor.In high-speed cutting,there are many problems,such as large cutting force,high cutting temperature,serious tool wear and so on.It leads to high cost and low efficiency of in the manufacturing of titanium alloy part.In order to solve this bottleneck problem,it is necessary to further study the mechanism of titanium alloy in high-speed machining.Therefore,this subject carried out high-speed orthogonal cutting experiments of Ti6Al4V titanium alloy in a wide range of cutting parameters.The mechanism of high-speed cutting of Ti6Al4V was deeply revealed from the aspects of cutting deformation and cutting force.The main research contents and conclusions are as follows:(1)The cutting experiments of Ti6Al4V titanium alloy were carried out.A special tool holder was designed.The orthogonal cutting experimental platform was built on the milling machine.The fabrication of the test pieces was completed.The experimental tool,experimental machine tool,the equipment for chip observation and cutting force measurement were determined.The cutting parameters of whole factor experiment were selected and the experimental process was introduced.(2)The cutting deformation of Ti6Al4V titanium alloy was analyzed.The chips under different cutting conditions were observed.The formation mechanism of serrated chip was analyzed.Through the physical and geometric characterization of serrated chip,the influence of cutting parameters and rake angle on serrated chip were studied.Combined with the experimental results,the existing prediction model of segment spacing were compared and analyzed.The results showed that serrated chip can be produced in high-speed cutting of Ti6Al4V titanium alloy,which was caused by adiabatic shear.With the increase of cutting speed,the microhardness in the shear band increases gradually.With the increase of cutting speed,serration frequency and segmented degree increase.While the width and spacing of adiabatic shear band,segment spacing,tooth top angle and tooth bottom angle decrease.With the increase of cutting thickness,segmented degree,the width and spacing of adiabatic shear band,segment spacing increase,and serration frequency decreases.But the tooth top angle and tooth bottom angle have no obvious change.With the increase of rake angle,segmented degree,adiabatic shear band spacing,segment spacing decrease,and the serration frequency,tooth top angle,tooth bottom angle increase.However,the width of adiabatic shear band has no obvious change.Among the existing prediction models of segment spacing,the theoretical model based on energy dissipation has higher prediction accuracy.(3)The static cutting force of Ti6Al4V titanium alloy was analyzed.The influences of cutting parameters and rake angle on static cutting force were analyzed.The prediction model of static cutting force based on linear regression analysis and BP neural network were established respectively.They were verified by experimental data.The results showed that the static cutting force has the negative correlation with cutting speed and rake angle,and a positive correlation with the cutting thickness.The prediction results of the static cutting force model based on linear regression analysis and BP neural network are consistent with the experimental results.It can provide the theoretical basis for practical processing.(4)The dynamic cutting force of Ti6Al4V titanium alloy was analyzed.The influences of cutting parameters and rake angle on dynamic cutting force were analyzed.The relationship between dynamic cutting force and serrated chip was qualitatively analyzed.The theoretical prediction model of dynamic cutting force was established based on the amplitude of dynamic cutting force and the serration frequency.The results showed that when the cutting speed increases,the maximum value F_maxand amplitude F_dof dynamic cutting force decrease.When the cutting thickness increases,the maximum value F_maxand amplitude F_dof dynamic cutting force increase.When the rake angle increases,the maximum value F_maxof dynamic cutting force shows a decreasing trend,while the amplitude F_dhas no obvious change.With the increase of cutting thickness,there is a positive correlation between the amplitude of dynamic cutting force and the segmented degree.With the increase of cutting speed,there is a negative correlation between the amplitude of dynamic cutting force and the segmented degree.The predicted results of the dynamic cutting force model were basically consistent with the experimental ones.