Materials Science Forum Vols. 626-627

Abstract: Titanium alloys are extensively applied in aerospace, automotive, biomedical, and chemical industries owing to their excellent performance combining high strength-to-density ratio, good corrosion resistance, and high strength at elevated temperature. Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloys are used to replace the most common Ti-6Al-4V in some important applications such as some parts in aerospace engine. The purpose of this paper is to evaluate the machinability of TC11 alloys in the finish hard turning conditions. The paper presents the machinability results of TC11 alloys compared with Ti-6Al-4V, and analyzes the variables such as cutting force, surface integrity, and tool wear mechanism in the experiments.

Abstract: In order to increase the material removal rate of silicon wafer, composite abrasives slurry was used in CMP. Zeta potential of polymer particle was measured and interaction potential energy between silica abrasives and polymer particles in slurry were analyzed and calculated. Adsorptions between silica abrasives and polymer particles were observed with TEM. CMP experiments had been taken to analyze the effects of polishing parameters (the concentration of colloidal silica and polymer particle, the pressure and the speed of polishing) on the material removal rate. The mechanism of polymer particle in polishing was elaborated. Experimental results indicated that PS, PMMA and BGF polymer particles could adsorb silica abrasives in slurry. Silica shell/PS core, silica shell/PMMA core and silica shell/BGF core particles could be used to formulate composite abrasives slurries. The material removal rate with composite abrasives slurry was higher than that of single abrasive slurry. The maximum material removal rate was obtained with silica shell/BGF core composite abrasives slurry.

Abstract: The paper discusses the near wall region of soft abrasive particle flow in weak force finish machining method. Turbulent flow morphology in near wall region of rectangular channel with different viscosity is numerically simulated and compared. Through the analysis of kinetic equation of abrasive particle, the abrasive particle motion trace of different diameter in turbulent flow with different viscosity is simulated and compared. The result reveals the condition under which the fluids with different viscosity can form Turbulent flow is different. The greater the viscosity is, the greater the velocity needed is. Also the quantitative relation of velocity and flow volume is available to determine the pump parameter in abrasive particle flow machining. Fluid at wall has pressure and shear stress on work piece. The greater the viscosity and velocity is, the greater the wall pressure and shear stress is. So it is helpful to make material removal on work piece surface. But the greater the viscosity is, the greater the velocity attenuation of abrasive particle is. Abrasive particle mainly move along the flow direction with the movement of fluid. The velocity attenuation of larger diameter abrasive particle is much than the smaller particle but the latter can maintain greater velocity in a longer distance favorable for collision with the work piece surface salient.

Abstract: To guarantee the efficiency and accuracy of machining in high speed machining, a novel vector blending algorithm for velocity smooth link is proposed. Based on efficient acceleration/deceleration technique for a single distance movement, the desired acceleration/deceleration characteristics can be selected. According to acceleration/deceleration characteristics, two different acceleration/deceleration profiles for two corresponding distance movements are constructed respectively. Under the condition of length of movement, highest velocity and direction of motion, two different acceleration/deceleration profiles are blended. On-line implementation results show that the proposed approach makes velocity link smoothly and efficiency and accuracy of machining can be guaranteed.

Abstract: Combined the analytic method with the finite element method, the data necessary for calculating the heat distribution ratio for high speed cutting was mined first, and the experimental result was used to validate the authenticity of finite element modeling. Then, the ratio of heat distribution for high speed cutting based on the analytic model was obtained by customizing the special subroutine developed by the authors, which provides a new method for calculating the heat distribution.

Abstract: The objective of this study is to realize high-speed and high-accuracy electrical discharge machining (EDM) of micro holes using a combination of a conventional EDM machine and a maglev local actuator. In this paper, the conventional EDM machine and the wide-bandwidth, high-precision, 5-DOF controlled maglev local actuator are combined and cooperatively controlled. Then to accelerate the debris ejection from the machined holes, the driving methods of the axial jump and radial vibration of the electrode are discussed. The experimental results show that the maglev local actuator can adjust the gap between the electrode and a workpiece speedily, and the machining speed is improved by 434.2%, compared with conventional EDM machine. Moreover, by the jump and the circular motion of the electrode, the debris ejection can be accelerated, the abnormal electrical discharge can be avoided, and the machining speed also is improved by 580.3%.

Abstract: In Micro Wire Electrical Discharge Machining (Micro-WEDM), the kerf width varies with different machining parameters, which will greatly influence the machining precision. In order to study the kerf variations in Micro-WEDM, the influence of kerf variation is analyzed and the experiment considering the kerf width and machining speed are performed on self-developed micro-WEDM under different machining parameters. With the reference of the experiment results, 32μm wide slot is machined with Φ30μm wire-tool on stainless steel workpiece.

Abstract: In micro electrical discharge machining (micro-EDM) of deep holes, the debris dispersed in gap may increase the possibility of secondary discharge, resulting in electrode shape changing and low accuracy of machined hole. In this paper, the debris movement caused by flow fluid in the machining gap is analyzed to understand the mechanism of debris transport by using software, FLUENT. Comparison of debris movement calculated by the modified N-S equation and N-S equation is conducted. Debris movement calculated by the modified N-S equation is demonstrated to be correct by experiment. The simulation results can explain the phenomena such as subulate electrode and hole, unstable machining process and low machining speed in micro-EDM of deep holes. It is helpful to improve the process of micro-EDM.

Abstract: Based on Multi-Point (MP) forming technology and Single-Point Incremental (SPI) forming technology, MP-SPI combined forming method for sheet metal is proposed, the principle and two different forming techniques are illustrated firstly. Then the paper is focused on numerical analysis for the novel forming technique with explicit Finite Element (FE) algorithm. During simulation of spherical work-piece, dimpling occurs as a main forming defect in MP-SPI combined forming process. Simulation results show that the dimpling defect can be suppressed effectively by using elastic cushion. An appropriate thickness of elastic cushion is necessary to prevent dimpling. And also the deformation of the work-piece is sensitive to the shape of elastic cushion. The combined forming test shows that the numerical simulation result is closed to the experimental result.

Abstract: A reversible machining method using micro electrical discharge machining (EDM) was developed. This new method can achieve depositing or selective removing of metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one EDM machining system. In micro EDM deposition process, brass, tungsten and steel material can be deposited successfully. The deposited material has compact fine texture and combines close to workpiece. Then, micro complex structures by series deposition strategy and sub-deposition strategy were deposited. In the selective removal process, the machining effects of different working mediums were researched. Results show that the machining effect in liquid medium is better than that of in air. Finally, using the micro reversible EDM process, a micro square column with 0.070mm in side length, 0.750mm in height and a micro cylinder with 0.140mm in diameter, 1.180mm in height were fabricated.