Experimental Study On Cutting Deformation And Cutting Force In High Speed Machining Of 45 Steel

As a kind of medium carbon steel which commonly used in engineering,45 steel has good thermal conductivity.In general,adiabatic shear will not occur in the cutting process of it.However,when the cutting speed increases to a certain critical value,or the hardness of the material increases after quenching,the adiabatic shear phenomenon will occur,and result in the serrated chips.In the existing research,most of them mainly focus on hardened 45 steel,but there is little research on45 steel.As a result,there are still some problems in machining,such as the machining mechanism needs to be further clarified,and the selection of process parameters is lack of basis.Therefore,this subject carried out experimental research on the cutting deformation and cutting force of 45steel.The cutting mechanism of 45 steel was deeply revealed,which provided a reference for the selection and optimization of process parameters.The main research contents and conclusions are as follows:(1)The orthogonal cutting experiment of 45 steel was designed.The orthogonal cutting experimental platform was built on the machining center.The tool holder device and workpiece for the experiment were designed.The machine tool,tool,measurement system of cutting force,and equipment for chip observation and hardness measurement were selected.The whole factor experimental parameters were determined.(2)The cutting deformation of 45 steel was analyzed.Macroscopic and microscopic observations of chips were carried out.The deformation coefficient,shear strain and shear strain rate of continuous chip were calculated.The influences of cutting parameters on them were analyzed.Through the geometric and physical characterization,the qualitative and quantitative analysis of the serrated chip on edge in the cutting process was carried out.The prediction results of the existing model of segment spacing were compared and analyzed.The results show that with the increase of cutting speed,the deformation coefficient,shear strain and the width of adiabatic shear band decrease,while the shear strain rate,serration degree and serration frequency increase.With the increase of cutting thickness,the deformation coefficient,shear strain and shear strain rate,serration frequency and the width of adiabatic shear band decrease,while the saw-tooth degree increases.With the increase of rake angle,the deformation coefficient,shear strain,serration degree and the width of adiabatic shear band decrease,while the serration frequency increases.The model of segment spacing based on energy dissipation has the higher prediction accuracy.(3)The static cutting force of 45 steel was analyzed.The effects of cutting parameters and rake angle on static cutting force were analyzed.The equation of static cutting force was established based on regression analysis,and the significance test was carried out.The prediction model of static cutting force was established based on BP neural network and verified by comparing with the experimental results.The results show that:The main cutting force and feed force decrease with the increase of cutting speed and rake angle,and increase with the increase of cutting thickness.Cutting thickness has the greatest influence on static cutting force,followed by cutting speed.Both regression model and BP neural network prediction model have high prediction accuracy.(4)The dynamic cutting force of 45 steel was analyzed.The signal decomposition and spectrum analysis of dynamic cutting force were carried out by the fast fourier transform and wavelet analysis.The effects of cutting parameters and rake angle on the dynamic cutting force were analyzed.The relationships between the dynamic cutting force frequency and serration frequency,and that between the amplitude and serration degree were analyzed.The results show that:With the increase of cutting speed and rake angle,the maximum value F_max and the amplitude F_d decrease.With the increase of cutting thickness,the maximum value F_max increases,and the amplitude F_d does not change.With the increase of cutting speed,there is a negative correlation between the amplitude F_d and the serration degree.