Key Engineering Materials Vols. 375-376

Abstract: This paper introduces and summarizes the slicing technology of large-scare silicon wafers. And the research status of ID slicing, wire saw slicing and WEDM is summed up. Finally, this document indicates the direction of research and the development.

Abstract: With widely using difficult-to-process materials, such as the stainless steel and SnSb alloy, the magnetic-electrochemical compound polishing process has been paid much more attention by some Japanese and Chinese researchers. In the paper, the math model of the movement of the charged particles in a magnetic field is established through the analysis of its movement process, using Coulomb laws and Lorentz force. The velocity equations and loci equations are concluded, and the movements of there typical particles are compared carefully and analyzed. Therefore, the function of the magnetic field is drawn. In the end, to verify the model, the magnetic- electrochemical compound polishing process were tested and the results were compared with those obtained from the model, the results showed the movement model was reasonable and the analyzing to function of magnetic field was correct.

Abstract: According to the size effect theory established on the concept of geometrically necessary dislocations and results of nano-indentation experiments, a novel brittle-ductile mechanism of ultra-precision turning of single crystal silicon is proposed. The accurate critical chip thickness is firstly calculated on the basis of theoritical analysis. A macro-micro cutting model is created based on the brittle-ductile transition mechanism. Finally, the results of study are testified through experiments.

Abstract: With more and more applications of glass in advanced fields of science, the demand for glass machining precision and efficiency has increased greatly. More and more attention is being paid to glass cutting by ordinary tool because precise glass parts with various shapes can be obtained at high efficiency and low cost. But, in this method, rounded cutting edge radius of tool has important influence on precision and integrity of surface. This paper presents the laws of glass crack initiation and propagation when a cylindric indenter is used for glass indention. Research results show that two cracks that are symmetrical to the normal plane of the indentation surface occur suddenly when the load increases to a critical value. Closing occurs in the two cracks during unloading. The interior angle between the two cracks and critical load increase with rounded edge radius of cylindric indenter linearly.

Abstract: Microstructure of machined copper chips at very low velocity was characterized by transmission electron microscopy. The structure of the machined chip produced by reasonable combinations of machining parameters is virtually entirely occupied by isolated equiaxed submicron grains of 100~300nm in size with high-angle boundaries. A finite element model was developed to study large plastic deformation in plain orthogonal machining copper. The numerical results show most of the grain refinement associated with the formation of ultra-fine grained chip may be attributed to the large shear strain imposed in the deformation zone. It is feasible to take machining process as a method of preparing ultra-fine grained materials. But the optimal design of the machining process requires a precise and quantitative understanding of the mechanics of deformation-induced subgrain microstructure.

Abstract: The chip formation and morphology are definitely affected by tool geometry and cutting parameters such as cutting speed, feed rate, and depth of cutting. An experiment investigation was presented to study the influence of tool geometry on chip morphology, and to clarify the effect of different cutting parameters on chip deformation in orthogonal turning the wheel steel. The result obtained in this study showed that tool geometry affected the chip morphology significantly; cutting speed was the most contributive factor in forming saw-tooth chip.

Abstract: In machining, the size effect is typically characterized by a non-linear increase in the specific cutting energy (or specific cutting force) as the uncut chip thickness is decreased. A finite element model of orthogonal micro-cutting was established to study the influence of tool edge radius on size effect when cutting 7050-T7451 aluminum alloy. Diamond cutting tool was used in the simulation. Specific cutting force and specific cutting energy are obtained through the simulation. The nonlinear scaling phenomenon is evident. The likely explanations for the size effect in small uncut chip thickness were discussed in this paper.

Abstract: Effects of additive powders on the machining mechanism of powder mixed EDM were researched. The whole discharging process was discussed based on theory of plasma and dielectric. Experiments, oscillograms and energy spectrum analysis gotten in experiments were performed in order to examine the changes of discharge between EDM and powder mixed EDM.