Fundamental Research On Electrochemical Rounding Of Sharp Corners Of Inner Wall Of Small Holes Formed By EDM

The sharp corners will appear on the inner surface after the air film hole on the engine blade processed by EDM,which results in stress concentration.A pulse electrochemical rounding processing method is proposed aiming at the difficulty of removing sharp corners on the inner surface of aero-engine air film hole machining to provide a solution to the problem of stress concentration at sharp corners.Considering that the engine blades are expensive and cannot be directly studied on the blades,the 60°oblique hole template with 0.7mm diameter of EDM is used as the research object.The influence of processing voltage,processing time,processing gap,electrode exposed length and processing depth on the phenomenon of chamfering of the exit in the inclined hole is analyzed.A mathematical model for removing the sharp corners of the inner wall of the oblique hole under the action of pulse current was established.And the process of electrochemical rounding of the sharp corners was simulated by COMSOL two-dimensional simulation,by which the flow velocity distribution,current density distribution and temperature distribution of the processing area were studied.The durability of the insulating layer of different shapes of the tube electrode was studied under the action of an external electric field.The influence of the relationship between the electrode drop position and the electrode exposed length on the fillet is analyzed.The fillet can be inverted when the difference between the electrode drop depth and the electrode exposed length is between 3.8 mm and 4.2 mm.Under the same conditions,the electrode drop position is inversely proportional to the electrode exposed length.In addition,the single factor experiments of machining voltage,machining gap and machining time were carried out.The exposed length of the electrode,the descending position,the voltage,the processing gap and the processing time were set as 1.4mm,5.2mm,13V,0.01mm and 60s,respectively.A rounded corner with a radius of 0.1mm was successfully processed on the sharp corner of the oblique hole of the superalloy,and the position of the sharp corner of the inclined hole surface has been expanded by 0.356mm.