G.Y. Liu

Formation of porous hydrophobic stainless steel surfaces by maskless electrochemical machining

Surface topography is an important feature, which directly affects the friction, corrosion and flow characteristics of a workpiece. In this study, a new approach was explored to produce a microporous structure by maskless electrochemical machining (ECM). A rough surface with a microporous structure was created on a stainless steel substrate, and the principle of the micropore formation was investigated. It was found that the microporosity could form, grow and interconnect when the potential of the anodic surface was higher than the pitting potential of the material. The electric field is an important factor, and the surface topography can be altered by changing the electrical parameters. The porous microstructure was observed by laser scanning confocal microscopy. The rough and porous surface, modified with 1-dodecanethiol, exhibits hydrophobic characteristics, with a static contact angle of 137° for water droplets. This is a significant improvement in the wetting properties for stainless steels.

Optimal Design of Rotary Ultrasonic Vibrator and Research on its Machining Experiments

In order to obtain well work performance, a new design process and the optimal method are systemically presented during ultrasonic vibrator’s design. Firstly, the general dimensions are calculated according to formula of ultrasonic theory. Secondly, 3D model without flange is established, and the best position setting a flange has been conformed through finite element analysis (FEM). Then constraints are laid on the flange, and the best model of vibration is obtained based on model analysis. The results are benefit to the following control design of ultrasonic vibrator. Finally, an ultrasonic vibration system has been made, and a series of experiments validate the feasibility of the design method.

A Study of the Material Removal Rate of Electrical Discharge Machining of Particle Reinforced Metal Matrix Composites with Concavo-Convex Electrode

A new concavo-convex electrode has been designed and fabricated. And an analysis of the electrical discharge machining (EDM) of a particulate reinforced metal matrix composite this new electrode was conducted in this study. The material removal rate (MRR) of new electrode and normal electrode are compared in different applied voltage and duty cycle conditions. It was found that EDM with this new electrode can accelerate the debris discharge during machining so that it has a higher MRR compared to the case where a normal electrode was employed. Moreover, by studying the waveforms, it could confirm that a stable processing condition can be obtained by employing the new electrode. The experiment results reveal that it is a feasible and effective way to machine MMCs by employing this new electrode.

A Study of the Mechanism of Electrical Discharge Machining of Particle Reinforced Metal Matrix Composites with Concavo-Convex Electrode

A new concavo-convex electrode has been designed and employed. And an analysis of the electrical discharge machining (EDM) mechanism of a particulate reinforced metal matrix composite with this new electrode was conducted in this study. It was found that EDM with this new electrode can accelerate the debris discharge during machining so that it has a higher MRR compared to the case where a normal electrode was employed. Moreover, by studying the surface craters, it could confirm that discharge craters tend to connect together for the normal electrode. This indicates an abnormal arcing condition. Thus, the wire electrode was easy to be broken. While for the new electrode, separated craters were observed on the machined surface. This means a stable processing condition. The experiment results reveal the processing mechanism of EDM electrical discharge machining of MMCs by employing this new electrode.

An Optimal Process for Ultrasonic Amplitude Transformer Design with FEM

The amplitude transformer is one of the most important parts in ultrasonic work system. To amplitude transformer, the resonant frequency and location of flange are two crucial design objectives. For variable cross-section amplitude transformer design, the traditional theory calculation seems to be too verbose and sometime hard to get efficient solution. This paper focuses on using commercial FEM software-ANSYS to achieve an optimal design of amplitude transformer.

Composite Tools Design for Electrolytic Magnetic Abrasive Finishing Process with FEM

In hybrid process of electrolytic magnetic abrasive finishing (EMAF), there are usually two structures on the tool design, separated or composited. This paper has been focused on the design of the composite tool. How to make electrolyte reach working area is a problem which should be solved for the EMAF process when the composite tool is used, therefore a hollow structure of magnetic pole has been put forward as one possible solution. To understand the effects of the structure parameters of the tool on the abrasive brush of EMAF, Finite Element Method (FEM) has been employed to establish the magnetic field model and analyze the distribution of magnetic induction on the workpiece surface and magnetic pole.

A Study of Numerical Simulation and Experiment Investigation on ECMM Processing of PRMMC

The differences between the Electrochemical Mechanical Machining (ECMM) progress of Particle Reinforced Metal Matrix Composites (PRMMC) and normal metal are the behaviors of non-conductive Particles. This paper employed Finite Element Method (FEM) to analyze the electrochemical reaction around the particle under different parameters. To seek applicable process, the electric filed analysis in the interelectrode gap of the ECMM process with the embedded tools has been adopted. Experiments about work voltage, electrode gap and the formula and concentration of electrolyte dissolution have been done. Through an ECMM hybrid process combined with a fast back grinding process, a surface about Ra 0.5um of PRMMC has been achieved.

An Investigation on PRMMC Polishing with Electrochemical Mechanical Machining Process

Since Particle Reinforced Metal Matrix Composites (PRMMC) normally applied Al2O3, SiC particle and other hard material as reinforce item, traditional manufacturing processes are hard to machine PRMMC with high efficiency and low tool cost. This paper presents an electrochemical mechanical (ECMM) hybrid polishing procedure for PRMMC, and the influences of parameters such as work voltage, grinding area proportion, the formula and concentration of electrolyte has been investigated. Through a hybrid polishing compound with a no Z direction feed pure mechanical grinding progress in Vx opposite direction, Ra around 0.5um PRMMC surface can be achieved.

Experimental Investigation on Metal Coating by Means of ESD

The technology of electro-spark deposition has been investigated and the thickness of H13 steel coating up to 16.2μm has been achieved by applied SH-1000 electro-spark deposition power. It analyzed the effect of parameters such as voltage, discharge frequency, argon gas flow and rate deposition on the deposition thickness. The optimum deposition parameters have been selected through the orthogonal design. In order to improve coating quality, a novel method based on ultrasonic-assisted electro-spark deposition has been put forward.

A Study on a Polishing Process of Cr12 Hardening Steel with the Embedded Combined Tools

This paper presents a electrochemical-mechanical combined polishing progress of Cr12 hardening steel with a new kind of embedded tool. The embedded tool has been composed of two parts, the metal base acting as electrode and the inlayer with electroplating diamond grains on its outside surface which serves as mechanical grinding abrasive. The two parts are agglutinated by adhesive which can keep a good insulation of the inlayer during the mechanical process. The inter-electrode gap can be changed by altering the metal base and inlayer’s diameter. Through the investigation of numerical simulation and polishing experiment, it can be found that lower feed, reciprocate speed, longer trip of reciprocating, smaller diamond grains make better surface quality.