Study On The Key Techniques In The Electrochemical Machining Of Titanium Alloy Diamond-hole Grille

Titanium alloy grille is an important component of aircraft.The grille usually adopts diamond-hole structure with a small corner radius.The surface quality of titanium alloy grille parts should higher.To meet such application requirements,A high efficient processing technique for diamond-hole grille is needed.In this paper,both theoretical and experimental studies are used to develop an electrochemical machining method for titanium alloy diamond-hole grilles by investigating key technical aspects,such as the electrolyte composition,composite side wall insulation of the diamond-shaped cathode,and vibrating feed flow control.The problem of geometric precision control for titanium alloy diamond-hole grille is solved.The major experimental work and research results of this study are summarized below.1.The polarization and dissolution of titanium alloy were obtained based on the study of the electrochemical properties of titanium alloy in NaCl electrolyte,NaNO₃ electrolyte and mixed electrolyte.The polarization curve and surface morphology under low current density show that the alloy is in an activated state in NaCl electrolyte,while a passivation regime exists in the NaNO₃electrolyte and surface passivation easily,with a long incomplete passivation zone in mixed electrolytes,the surface morphology is significantly improved in mixed electrolytes.Under high current density,the surface of the alloy shows growing and overlapping pitting corrosion on the alloy in NaCl electrolyte,and severe dissolution and peeling occur in NaNO₃ electrolyte.In mixed electrolytes,the ions inter-penetrate to enhance the precision and quality of surface formation.These results provide the theoretical basis for the electrochemical machining of titanium alloy diamond-hole grille.2.A method for the insulation of the cathode side wall of the titanium alloy electrochemical machining tool was proposed.The influence of different thickness of insulating layer on the electric field distribution of the side wall of the cathode was studied.The composite insulation layer for the diamond tool side wall was prepared by a lab-made micro-arc oxidation electrophoresis composite process to test the influence of the insulation layer on electrochemical machining.The results demonstrate that the high durability composite insulation layer effectively restrains the stray electric field on the side wall,and substantially improves the machining accuracy of the side walls and rhombic angle position.By calculating the fluid-structure interactions between the diamond cathode and the insulation layer,the changes in the flow field distribution and shear stress on the side wall were determined,and were used to study the impact of the vibration frequency and amplitude on the shear in the insulation layer.The shear stress of insulating layer under maximum operating condition was calculated.Thus provide basis for design and preparation of high performance insulating layer.3.A coupled multiple-physical field model for the vibrating feed electrochemical machining of the diamond-hole grille was established.Using coupled multiple-physical field calculations,the interplay among the flow field,bubble rate,and fluid heat transfer in the machining gap during vibration feeding of the diamond tool was determined,along with the effects of the vibration frequency and amplitude on material removal.Relevant experiments were carried out to give theoretical and experimental evidence of the significant enhancement of flow field stability by vibration feeding of the diamond cathode during electrochemical machining.4.A complete solution to the engineering application of diamond-hole grille precision electrochemical processing technology was put forward.Analyses and experimental results using three different electrolyte groove configurations on the cathode showed that the electrolyte should flow through the groove in short arcs,and that reasonable vibration feeding process parameters markedly improves the machining precision the side wall of the grille.With taper angle,diamond corner angle,and side gap as the technical standards in grille machining,an orthogonal experiment was designed for diamond-hole grille to investigate the relation between design factors and process objectives.An ECM response surface function and a model with multi-objective optimization were obtained.The genetic algorithm was used to optimize the multi-objective process,thus provide an important reference for the application of diamond-hole grille.