Cathode Design And Experimental Research For Electrochemical Machining Of Trumpet-shaped Pin Hole

With the improvement of engine emission standards,the load on the piston pin hole is increasing.It is difficult to ensure the accuracy of the profile shape of the trumpet-shaped pin hole by using mechanical methods to process the forged steel piston pin hole.In this thesis,the pulse electrochemical machining method is used to process the pin hole of the piston.The cathode tool was designed and manufactured.Finally,the shape accuracy and surface roughness of the workpiece were explored through electrochemical machining experiment.In this thesis,firstly,the electrochemical characteristics of workpiece materials are studied,and the influence of electrode potential of alloy phase on surface forming accuracy and roughness is analyzed.The decomposition voltage of the workpiece material and the influence of electrolyte on the surface roughness of the workpiece were obtained by experiments.NaNO3 electrolyte was determined as the experimental processing electrolyte,and the experimental voltage range was determined.By studying the forming theory of electrochemical machining,the relation between the ablation rate and the machining clearance is obtained,and the machining gap at any time in the electrolytic process can be obtained.The simulation mathematical model of trumpet-shaped pin pass line based on electric field distribution was established.The simulation of electrochemical machining was carried out by using COMSOL Multiphysics software,and the rules of electrochemical machining were summarized through the simulation.BP neural network algorithm was used to modify the initial cathode,and finally the modified cathode tool was used for electrolytic simulation processing.The shape of trumpet-shaped pin pass could achieve greater precision.The surface roughness of the workpiece was studied by electrochemical machining,The effect of electrolyte mass fraction,processing voltage,duty ratio and pulse frequency on the surface roughness of the workpiece was investigated.Finally,the optimal parameter combination was found by designing orthogonal experiments.The final surface roughness value of the processed workpiece reached 0.172μm.The effect of various factors on the surface roughness was obtained through range and variance analysis:Sequence electrolyte concentration>Voltage>Duty Cycle.The cathode tool is used to explore the electrolytic forming of the trumpet-shaped pin hole profile.Different processing parameters are used to carry out a number of experiments,and the contour of the abnormal pin hole profile is obtained.By analyzing the profile error of the workpiece profile,the quantitative relationship between the error and the machining depth is obtained under the experimental processing parameters:voltage 12V,pulse frequency 10kHz,duty cycle 0.3,initial machining gap 0.10mm,electrolyte concentration 10%.According to the quantitative relationship between the error and the machining depth under specific conditions,a cathode correction method based on error compensation was established and verified by simulations.