摘要: In this paper, the disadvantages of the current CBN (Cubic Boron Nitride) grinding wheels were firstly introduced briefly, for indicating that it was very urgent and important to develop new kinds of grinding wheels with excellent performance to replace the conventional wheels. Then high temperature brazing experiments of monolayer CBN wheels with Ag-Cu-Ti filler alloy were carried out. The result shows that the filler alloy has good wetting capability towards CBN grits. The results of scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis show that, just because during brazing titanium atoms in filler alloys segregated preferentially to the surface of the CBN to form Ti-nitride or Ti-boride layer by reaction between titanium atoms and nitride and boron atoms at elevated temperature, strong chemical joining was formed in the interface between CBN grits and filler alloys. Finally, the contrastive grinding experiments were performed between the monolayer brazed CBN grinding wheels and the electroplated ones. The results show that the brazed wheels have more excellent performance than the latter.
摘要: The tool plays an important role in cutting process. The aim of this paper is to investigate the effect of tool geometrical parameters on the chip formation and cutting force with orthogonal cutting models. The large deformation Rigid-visco-plastic FEM program DEFORM-2DTM is used, and thermo-mechanical coupling effect are considered. The chip separation from workpiece is implemented by remeshing. Contrary to traditional cutting simulation, the workpiece is moved and
the tool is fixed, which is consistent with actual process. The effects of tool rake angle on the chip geometry and cutting force are analyzed. The simulated cutting forces are compared with results in other references. The research results are a help to cutting process study and cutting tool design.
摘要: Thermal shock resistance is one of the primary properties for the ceramic cutting tool materials with perspectives in high speed machining. An optimum model for the compositional design of the composite ceramic tool materials is built based on the thermal shock resistance. The thermal stress fracture resistance factor R is used to characterize the thermal shock resistance of the ceramic material. Results show that the developed (W,Ti)C/SiC/Al2O3 multiphase ceramic tool material can be expected to achieve the highest thermal shock resistance when the volume fraction
of (W,Ti)C and SiC is about 15.8% and 24.8%, respectively. Thermal fracture resistance of the (W,Ti)C/SiC/Al2O3 ceramic tool material is approximately 81-88% higher than that of the pure alumina ceramic when machining the hardened carbon steel, which coincides well with the theoretical prediction from the optimum model. It suggests that the method used here is feasible for the development of ceramic tool materials with designed thermal shock resistance.
摘要: Chemical mechanical polishing (CMP) has already become a mainstream technology in global planarization of wafer, but the mechanism of nonuniform material removal has not been revealed. In this paper, the calculation of particle movement tracks on wafer surface was conducted by the motion relationship between the wafer and the polishing pad on a large-sized single head CMP machine. Based on the distribution of particle tracks on wafer surface, the model for the within-wafer-nonuniformity (WIWNU) of material removal was put forward. By the calculation
and analysis, the relationship between the motion variables of the CMP machine and the WIWNU of material removal on wafer surface had been derived. This model can be used not only for predicting the WIWNU, but also for providing theoretical guide to the design of CMP equipment, selecting the motion variables of CMP and further understanding the material removal mechanism in wafer CMP.
摘要: Cutting tool and machining parameters selection are central activity in process planning, which was traditionally performed by numerical control programmers or machine tool operators. The surface integrity has great effect on part quality and the sudden tool failure increases the machining costs greatly. The present paper details the development of a cutting database system with surface integrity prediction and tool failure analysis functions (CUT-P&A). The design and implement of this
system has been presented. The system includes three main modules: cutting database, premature tool failure analysis and surface integrity prediction. The functions of this system include cutting tool selection and machining parameters recommendation, prediction of surface integrity and premature tool wear analysis. A case has been studied to explain the application of the system. The wide application of this system will be helpful for machining tool programmers, the improvement of
machined part quality and the reduction of machine cost.
摘要: To perform several micro-machining on same machine tool, a micro machining
equipment was researched and developed. The equipment adopts some high and new technologies. It is equipped with high precision XYZ stage, a spindle with high rotation accuracy and variable rotation speed, a granite worktable, a block electro discharge grinding unit for machining micro rod, a ultrasonic vibration unit for workpiece vibrating, a high frequency pulse power supply for micro-ECM and a video microscopic system with high enlargement factor. The equipment can
perform micro electro discharge machining (EDM), micro electrochemical machining (ECM), micro ultrasonic machining (USM) as well as their combination. It can also machine 3D microstructures. A series of experiments were carried out. Using micro-EDM, micro rods with the diameter of less than 5µm were ground on block electrode, micro holes and 3D microstructures were obtained. Shaped holes were machined by using combination of micro-EDM and micro-USM.
A micro hole with the diameter of 100µm was machined via micro-ECM.
摘要: With the advent of high-power pulsed lasers, laser peening has emerged as a new and very promising technique to improve the resistance properties of materials to fatigue, wear and corrosion. In this paper, the effect of laser peening on the surface performance of QT700-2 materials was investigated, the parameters of laser peening were optimized by an artificial neural network (ANN) method. A series of experiments was carried out by using a high-power, Q-Switched, pulsed neodymium-glass laser. The microstructure features were analyzed with SEM and the hardness and residual stresses at the surface and in-depth were measured. The results indicate that the depth of hardened layer was about 0.31ı1.40mm for a different shot number of 1-4 times and the compressive residual stress at the surface increases with increasing laser pulse energy, from -165MPa for the low
energy 12J to -410MPa for the higher energy 20J. Laser peening can restrain nucleation of fatigue cracks and improve the fatigue life of nodular cast iron materials.
摘要: While be ground, ceramic is prone to engender surface/subsurface crack damage layer because of great grinding force and high brittle of the material. The crack damage layer was investigated in this research. In experiment, it is observed that the surface/subsurface crack damage layer consists of three kinds of cracks: surface micro-cracks, surface macro-cracks and subsurface crack system. To evaluate expediently the degree of damage to the machined components, the index of surface/subsurface crack damage - Dc, is defined.