Advanced Materials Research Vol. 797

Abstract: In cylindrical grinding, a sizing device is generally used to obtain the required dimension. However, the dimensional error can be caused by the thermal deformation of the workpiece even if grinding machine is controlled with the sizing device. To solve this problem, it is necessary to develop the grinding system that can consider the thermal deformation of the workpiece during grinding process. In this study, an advanced grinding system was developed, which can predict the net stock removal of ground workpiece immediately. The grinding experiment is carried out to verify the developed system.

Abstract: The thermocouple temperature measurement method was adopted to measure the surface temperature in micro-grinding experiment. According to the different grinding depth, the appropriate processing parameters were chosen to find out the temperature field distribution on the surface and in different depth of subsurface. It provided a reference basis in order to prevent the grinding burn. It proves that the method combining the finite element theory with experiment method is correct and feasible. It is a basis of the factors of the grinding temperature and surface integrity of the parts. Further more, it is of great significance that grinding mechanism and surface quality improving of the parts be discussed thoroughly.

Abstract: The cutting edge radius R_e leads to the minimum uncut chip thickness in micro machining. The single-edge single-grit model was developed for micro mill-grinding in this paper. Simulations for Ti6Al4V were performed in various cutting depths, and the minimum uncut chip thickness of micro mill-grinding was confirmed to be between 0.25R_e and 0.3R_e (approximate 0.275R_e). Various grain heights of protrusion were investigated to discuss the influence of grain depths of cut on the minimum uncut chip thickness. The minimum uncut chip thickness will increase if the grinding debris forms, while it will get smaller if the grinding debris cant be generated.

Abstract: The micro-processing technology has gradually become a hot topic problem, especially in micro-scale milling chatter prevention with the development of the information age. In allusion to the actual case of micro-milling, the dynamic theoretical research is analyzed in-depth about the Fourier method and the average tooth angle method. Compared to two ways, the former is close to the actual processing requirements. The lobes are obtained use the two ways. Micro milling parameters are selected in the stable area and unstable region. Stable and non-stable curve and surface quality of machined parts are obtained after micro-milling test. The chatter points, non-chatter point and uncertain point are obtained in the high spindle speed, which are consistent with theoretical analysis. In contrast, the distribution of chatter points in the low-speed spindle speed. The reason is that the damping effect is produced in the micro-scale milling process. The research of micro-scale milling chatter, which has a certain significance to improve parts of precision machined parts, reduce the wear and tear of the micro-milling blade and extend micro-tool life.

Abstract: mproving materials surface function by introducing nano/micro surface textures is of great interest in various fields. The authors have also achieved an improvement in the photocatalytic surface function by introducing the microcutting grooves texture on the titanium dioxide surfaces. In this report, the authors performed the vibration assisted cutting to fabricate finer surface microtextures anticipating future usage as microtexture moulds for the nanoimprinting and/or injection moulding. In the experiment, a pure copper plate was cut using a sharply pointed triangular diamond tip vibrated by a fast tool servo system in the direction of cutting depth with μm order amplitude and kHz order frequency. As a result, it was found that the periodical micro concave-convex patterns with the combinations of impressions and pileups can be obtained by the proposed method using almost the same vibration amplitude as the cutting depth. It was also achieved that a micro-textured surface with numerous concave-convex patterns less than 1 μm in height with 3 μm in pitch.

Abstract: This paper describes theoretical analysis of bending deflection and anisotropic rigidity of drill, and the induced radial forces in micro drilling. The main results obtained are as follows. (1) There are two different modes of drilling which cause bending deflection of drill and induce radial forces. They are position error mode and run-out mode. (2) The radial forces induced behave quite differently between the two modes. (3) The radial forces increases as the depth of hole increases, because the rigidity of drill beam increases. (4) The position error mode induces a cyclic stress in the drill which may cause a fatigue breakage.

Abstract: Micro milling has been known to behave quite differently from conventional macro milling. The effect of cutting speed on the machined surface roughness in micro milling of ductile materials was investigated in this paper. The micro flat end milling cutters of the diameters of 0.5 mm and 0.3 mm were taken to machine 6061 aluminum alloy and S20C low carbon steel. For comparison purpose, the cutter of the diameter of 10 mm was tested as well. It is found that the machined surface finish is closely related to the cutting speed. For a large size cutter, the roughness decreases with the increase of cutting speed as expected. But the decreasing trend is valid only up to a certain speed for the small diameter cutters. It is also noted that beyond this speed limit broken and powder type chips form easily. These chips will adhere to the machined surface and tool face and deteriorate machined surface as a result. Based on this finding, an approach by directing the cutting fluid to the cutting zone via high pressure air assistance is proposed. It is verified that the cutting force and its variation are greatly reduced, tool wear becomes less, and finish of the machined surface is significantly improved.

Abstract: Surface residual stress has become one of the important indexes measuring surface integrity in hard turning of precision parts. The type of surface residual stress and the influence rules of cutting parameters on surface residual stress in hard turning of GCr15 steel are studied in this paper. Research results show that no matter in common or ultrasonic turning, tangential surface residual compressive stress can be found in machined surface. The effect of cutting speed on the residual compressive stress is the greatest, the effect of feed rate takes the second place and the effect of depth of cut is minimal. The conclusions have provided experimental basis for enhancing the surface integrity of quenched GCr15 steel precision parts.

Abstract: The effect of low-frequency pulsed magnetic treatment on micro-hardness of W9Mo3Cr4V(W9) high speed steel (HSS) has been investigated. A low-frequency pulsed magnetic treatment system was designed and applied to treat the tool material. Experiments were conducted at different magnetic field intensities and pulse frequencies. Experimental results show that the low-frequency pulsed magnetic treatment can effectively increase the micro-hardness of W9 HSS in a proper treatment parameters. The micro-hardness change rate first increase and then stabilize as the magnetic field intensity increases. Pulse frequency has little effect on the treatment effect.

Abstract: To provide a fundamental knowledge for the high efficiency grinding and ultra-precision grinding of fused silica, ductile mode and brittle mode material removal mechanisms were investigated by conducting micro/nanoindentation experiments in the range of 4.9 mN - 1960 mN. Before observing cracks and determining the ductile to brittle transition penetration depth, the samples were etched with hydrofluoric acid to expose cracks. The typical damage morphology of fused silica was discussed by observing the surface and cross-section of indentations, and the depth of SSD was found to be determined by the cone cracks or borderline cracks in the different load range. The ductile to brittle transition penetration depth of fused silica under Vickers indentation was 180 nm.