Forming Law Of Moving Electrochemical Machining Of U71Mn Stretched Parts

In the field of manufacturing,large and complex integral structural parts and stretching workpiece of hard-to-cut materials are widely used in aerospace,transportation,precision transmission,etc.The long stretched workpiece formed of U71 Mn material are mainly used for high-speed heavy-load transportation because of its high hardness and high strength.After a long time of use,the surface of workpiece will be damaged such as peeling off block,crushing and wave grinding.At present,the solution of mechanical milling has the disadvantages of poor surface quality,serious environmental pollution and high cost.The moving electrochemical machining(MECM)technology has the characteristics of smooth surface,good surface quality and low environmental pollution,which can enough avoid the problems caused by traditional milling and grinding.Therefore,in view of the defects of existing milling and grinding processes in realizing the machining of workpiece outer contour surface,this thesis research the problem of using MECM process to solve the machining of U71 Mn material stretched workpiece outer contour surface,and focuses on the research of workpiece forming mechanism and forming law,centering on the establishment of workpiece forming model during its MECM process,multi-physical field simulation and parameter range solution,and the research on the influence law of main parameters.Multi-parameter and differential equation optimization are studied in four aspects.The main research contents are as follows:(1)The MECM technology is used to realize the machining of the outer contour of the workpiece.The chemical composition and physical properties of the research object,the electrochemical characteristics in the machining process and the influence mechanism between various physical fields are analyzed.The cathode with machining surface of "wedge" shape is designed.The differential equation between material removal volume and machining time,cathode length and cathode moving speed in the process of workpiece forming is established by slice method,and the influence of inter electrode parameters on workpiece forming is studied.(2)Aiming at the influence of electric field,flow field and temperature field in the MECM process,several two-dimensional transient multi-field coupling simulation analysis are carried out by using COMSOL software.The mathematical modeling,geometric modeling and boundary modeling of the model are carried out,and the parameters in the model are solved.The distribution of each physical field under different cathode length,different machining gap and different cathode moving speed is studied.The influence laws of electrolyte inlet and outlet pressure,electrolyte temperature and machining voltage are simulated,and the appropriate parameter range is optimized.Preliminary validation of the forming equation has been achieved.(3)In order to analysis the influence of various factors on the workpiece forming process,single factor experiments and orthogonal experiments with six parameters such as cathode moving speed,pulse voltage,duty cycle,pulse frequency,electrolyte inlet pressure and initial temperature are designed and carried out.The effects of different parameters on material removal rate and roughness are analyzed through single factor experiment.At the same time,the order of the effects of six parameters on surface roughness,dimensional deviation and material removal rate is obtained through orthogonal experiment and range analysis,so as to obtain its forming law.(4)The process parameters are optimized by multi-objective genetic algorithm and the forming differential equation is optimized.Based on this,comprehensive experimental verification is carried out.The quadratic regression mathematical model of surface roughness,dimensional deviation and material removal rate is established,and the program code is designed by MATLAB software.The optimized parameter combination is as follows: cathode moving speed 16.6 mm/min,pulse voltage 16 V,duty cycle 70%,pulse frequency 450 Hz,electrolyte inlet pressure 0.45 MPa and electrolyte initial temperature 18 ?.The theoretical values of the three experimental indexes are as follows: surface roughness Ra 0.449 ?m.The dimensional deviation is 0.091 mm and the material removal rate is 64.7 g/min.The differential equation of the forming process is optimized,and a comprehensive experimental study is carried out based on the optimized results and optimized parameters.The experimental results are as follows: the surface roughness is Ra 0.470 ?m.The size deviation is 0.095 mm,the material removal rate is 63.4 g/min,and the deviation from the theoretical value is no more than5%.The correctness of the parameter optimization results and equation optimization results are verified.Finally,the chemical composition of the surface before and after machining is analyzed to confirm that the workpiece after MECM meets the machining requirements.Machining complex outer contour surface of U71 Mn stretched workpiece by MECM process can effectively solve the problems of poor surface quality and serious environmental pollution caused by milling and grinding technology,and the preliminary verification of MECM process and exploration of forming rules meet the requirements.