Electrochemical machining （ECM） has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is...Electrochemical machining （ECM） has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 ram. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.展开更多
In counter-rotating electrochemical machining （CRECM）, a revolving cathode tool with hollow windows of various shapes is used to fabricate convex structures on a revolving part. During this process, the anode workpi...In counter-rotating electrochemical machining （CRECM）, a revolving cathode tool with hollow windows of various shapes is used to fabricate convex structures on a revolving part. During this process, the anode workpiece and the cathode tool rotate relative to each other at the same rotation speed. In contrast to the conventional schemes of ECM machining with linear motion of a block tool electrode, this scheme of ECM is unique, and has not been adequately studied yet. In this paper, the finite element method （FEM） is used to simulate the anode shaping process during CRECM, and the simulation process which involves a meshing model, a moving boundary, and a simulation algorithm is described. The simulated anode profiles of the convex structure at different processing times show that the CRECM process can be used to fabricate convex structures of various shapes with different heights. Besides, the variation of the inter-electrode gap indicates that this process can also reach a relative equilibrium state like that in conventional ECM. A rectangular convex and a circular convex are successfully fabricated on revolving parts. The experimental results indicate relatively good agreement with the simulation results. The proposed simulation process is valid for convex shaping prediction and feasibility studies as well.展开更多
Counter-rotating electrochemical machining(CRECM)is a novel shaping method with advantages in processing revolving parts,especially engine casings.However,few researchers have studied the anodic behaviour of the count...Counter-rotating electrochemical machining(CRECM)is a novel shaping method with advantages in processing revolving parts,especially engine casings.However,few researchers have studied the anodic behaviour of the counter-rotating state.This paper aims to analyse the anode dissolution behaviour of TA15 and obtain desired surface qualities in CRECM.The anodic characteristics were measured by polarization and cyclic voltammetry curves,and the passive-trans passive behaviour of TA15 was revealed.The electrode surface structures at different stages were analysed using electrochemical impedance spectroscopy(EIS),and a quantitative dissolution model was established to illustrate the electrochemical dissolution and structural evolution of the revolving surfaces.A series of CRECM experiments were conducted,and three stages(pitting corrosion,pitting expansion,and smoothing)were detected according to the current signals.In the first stage,an oxide film with small pores was formed initially on the metal surface when exposed to air.This air-formed oxide film was broken down locally during the electrochemical reaction process,resulting in the occurrence of pitting.With the increase of electricity,the oxide layer became thinner,and the pitting areas expanded and began to connect with each other.In this stage,the surface quality was poor owing to the uneven material dissolution.When the amount of electricity approximately reached a constant,the oxide layer was completely removed,and a very thin salt film was generated at the metal-electrolyte interface.In this stage,the material was dissolved uniformly,and the surface was smooth without pitting corrosion.Based on the obtained results,anode workpieces with grid-like convex structures were fabricated using CRECM.Both the revolving surface and the sidewalls of the convex structures can be controlled from pitting to smoothness.展开更多
基金Supported by Program for New Century Excellent Talents in University,China(Grant No.10-0074)
文摘Electrochemical machining （ECM） has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 ram. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.
基金supported by the Program for New Century Excellent Talents in University of China(NCET-10-0074)
文摘In counter-rotating electrochemical machining （CRECM）, a revolving cathode tool with hollow windows of various shapes is used to fabricate convex structures on a revolving part. During this process, the anode workpiece and the cathode tool rotate relative to each other at the same rotation speed. In contrast to the conventional schemes of ECM machining with linear motion of a block tool electrode, this scheme of ECM is unique, and has not been adequately studied yet. In this paper, the finite element method （FEM） is used to simulate the anode shaping process during CRECM, and the simulation process which involves a meshing model, a moving boundary, and a simulation algorithm is described. The simulated anode profiles of the convex structure at different processing times show that the CRECM process can be used to fabricate convex structures of various shapes with different heights. Besides, the variation of the inter-electrode gap indicates that this process can also reach a relative equilibrium state like that in conventional ECM. A rectangular convex and a circular convex are successfully fabricated on revolving parts. The experimental results indicate relatively good agreement with the simulation results. The proposed simulation process is valid for convex shaping prediction and feasibility studies as well.
基金supported by the National Natural Science Foundation of China(Grant No.51805259)the National Natural Science Foundation of China for Creative Research Groups(Grant No.51921003)+1 种基金the China Postdoctoral Science Foundation(Grant No.2019M661833)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_0192)。
文摘Counter-rotating electrochemical machining(CRECM)is a novel shaping method with advantages in processing revolving parts,especially engine casings.However,few researchers have studied the anodic behaviour of the counter-rotating state.This paper aims to analyse the anode dissolution behaviour of TA15 and obtain desired surface qualities in CRECM.The anodic characteristics were measured by polarization and cyclic voltammetry curves,and the passive-trans passive behaviour of TA15 was revealed.The electrode surface structures at different stages were analysed using electrochemical impedance spectroscopy(EIS),and a quantitative dissolution model was established to illustrate the electrochemical dissolution and structural evolution of the revolving surfaces.A series of CRECM experiments were conducted,and three stages(pitting corrosion,pitting expansion,and smoothing)were detected according to the current signals.In the first stage,an oxide film with small pores was formed initially on the metal surface when exposed to air.This air-formed oxide film was broken down locally during the electrochemical reaction process,resulting in the occurrence of pitting.With the increase of electricity,the oxide layer became thinner,and the pitting areas expanded and began to connect with each other.In this stage,the surface quality was poor owing to the uneven material dissolution.When the amount of electricity approximately reached a constant,the oxide layer was completely removed,and a very thin salt film was generated at the metal-electrolyte interface.In this stage,the material was dissolved uniformly,and the surface was smooth without pitting corrosion.Based on the obtained results,anode workpieces with grid-like convex structures were fabricated using CRECM.Both the revolving surface and the sidewalls of the convex structures can be controlled from pitting to smoothness.
