| Large-pitch screw threads are widely used in heavy equipment such as large machine tools and ten thousand ton presses.They are important parts for the transmission of power and displacement.Their machining accuracy directly affects the running accuracy of the equipment,so they occupy an important position in the production equipment of enterprises.Due to the characteristics of high feed,large cut depth and low speed,the cutting speed and feed speed do not match when turning large pitch thread,which leads to the sudden change of cutting load and causes violent vibration of the process system.The vibration of the large pitch thread tool under the action of multi-strength field coupling makes the size of the thermal field and the thermal concentration point on the surface of the tool change all the time,which leads to the severe wear of the tool surface,and seriously affects the life of the tool and the surface quality of the workpiece of the large pitch thread.Therefore,in view of the above problems,this paper based on the finite element analysis software DEFORM from the workpiece stress field and the tool temperature field,to explore the distribution law of vibration in the process of cutting,and the cutting parameters and tool structure parameters were optimized.Specific research contents are as follows:Firstly,the influence factors of vibration in the process of turning large pitch thread are analyzed,the source of vibration in the process of cutting is determined and the excitation model of the process system is established,and the vibration suppression measures are put forward from three aspects of tool structure,workpiece system and machine tool system respectively.Secondly,the force-thermal analysis is carried out on the tool with large pitch thread,and the force situation of the tool with large pitch thread is studied.The maximum stress on the tool front face and the stress and friction force on the tool back face are analyzed,and the force model of the tool front and back face is obtained.The source and distribution of heat in the cutting process were studied,and the temperature fields of the front and back surface of the cutting tool were analyzed.The temperature rise models of shear heat source,cutter-chip friction and cutter-working friction heat source were established.Again,with the consideration of vibration under the condition of big pitch thread tool thermal coupling field simulation analysis,by turning the big pitch screw orthogonal experiment,the vibration acceleration signal,adopt the method of quadratic integral vibration displacement,vibration acceleration signal can be converted to overlay the turning big pitch thread tools ideal trajectory equation,get the vibration under the action of the tip trajectory;The stress field of the workpiece and the temperature field of the tool under vibration were simulated and analyzed by using the finite element software DEFORM,and the variation rules of the stress field and temperature field under different strokes were obtained.Then the simulation data and experimental data were compared and analyzed to verify the validity of the simulation.Response surface method(RSM)was used to analyze the influence law of spindle speed,axial feed amount,tool back Angle and cutting edge radius on the maximum equivalent stress of workpiece and the maximum tool temperature,and it was confirmed that spindle speed had a great influence on the stress and temperature.Finally,an optimization model based on stress,temperature and cutting efficiency was established,and the optimal spindle speed,axial depth of cut,tool rear Angle and cutting radius were determined based on artificial bee colony algorithm.Then,the effectiveness of the optimization results was determined by comparing the cutting force and cutting vibration under different cutting parameters and tool structure parameters. |
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