Key Engineering Materials Vols. 304-305

Abstract: In this paper the modeling method of object entity in the environment of virtual is introduced and the three-dimensional simulation model of grinding wheel is established in Visual C++ programming language and OpenGL tool. The simulated experiment is made, which can indicate the effect of different parameters to grinding process. It proved the reliability and practicability of virtual wheel through comparing the simulation results and experimental data.

Abstract: This study focuses on experimental and theoretical investigations of grinding forces for nanostructured WC/12Co coatings. In this study, nanostructured WC/12Co coatings are ground on a precision surface-grinding machine with four diamond wheels of two bond types and three grit sizes. A mathematical model is proposed to predict grinding forces per unit area and per grit, and is used to fit the experimental data. The model is also subsectioned into two different parts with one part fitting grinding forces for the smaller grit depth of cut condition and the other part for the larger grit depth of cut condition. Grinding mechanisms are also discussed in terms of grinding forces and grit depth of cut.

Abstract: This paper presents a comparison study of surface hardening by grinding versus machining. The technological, economical and ecological merits of machining hardening and grind-hardening process for steels are described. The mechanisms of machining hardening and grind-hardening of steels are investigated and compared. The phase transformation, plastic deformation and white layer generation are the principal factors contributing to the hardened surface layer by machining and grinding. The influences of the process parameters on the penetrated hardness are given for both grind-hardening and machining hardening operations. The future development trends of the grind-hardening and machining hardening are also presented.

Abstract: In the present study, zirconia ceramic, crystal and two typical natural granites were ELID ground on a precision grinding machine under the same condition. The surface appearances during the grinding process with different mesh size metal bonded diamond wheels were examined to describe the formation of finely finished granite surfaces. According to the detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of the main mineral components for natural granites are really similar to other brittle materials during ELID grinding process. However, the differences of material performances cause the granite materials to be larger critical grain depth of cut and more ductile during finely grinding.

Abstract: In order to improve the grindability of titanium alloys, the inhibition of chemical affinity between abrasives and titanium alloys and cooling enhancement in grinding zone are carried out in this paper. Slotted electroplated CBN grinding wheels with optimum topography are used, and different grinding fluid supply systems such as conventional tangential spraying coolant supply, inner chamber coolant jet impingement, radial high-pressure coolant jet impingment are employed in creep feed deep grinding experiments on titanium alloy (TC4). The experimental results show that high-pressure jet impingement has remarkable cooling effect. The temperature of the workpiece surface can be steadily kept below the critical film boiling temperature 120~130°C, while the workpiece surfaces is badly burnt with conventional coolant supply. The study will exploit an important research orientation that has great potential in high efficiency grinding. Further perfection of this study will not only enable us to increase the available material removal rate to a new level but also solve the workpiece burn problem of the difficult-to-machining materials in high efficiency grinding.In order to improve the grindability of titanium alloys, the inhibition of chemical affinity between abrasives and titanium alloys and cooling enhancement in grinding zone are carried out in this paper. Slotted electroplated CBN grinding wheels with optimum topography are used, and different grinding fluid supply systems such as conventional tangential spraying coolant supply, inner chamber coolant jet impingement, radial high-pressure coolant jet impingment are employed in creep feed deep grinding experiments on titanium alloy (TC4). The experimental results show that high-pressure jet impingement has remarkable cooling effect. The temperature of the workpiece surface can be steadily kept below the critical film boiling temperature 120~130°C, while the workpiece surfaces is badly burnt with conventional coolant supply. The study will exploit an important research orientation that has great potential in high efficiency grinding. Further perfection of this study will not only enable us to increase the available material removal rate to a new level but also solve the workpiece burn problem of the difficult-to-machining materials in high efficiency grinding.

Abstract: On the basis of analyzing the brittleness, ductileity, and the removal mechanisms of the^nano-ZrO2 Ceramics, the critical ductile grinding depth formula of the nano-ceramics was established. Due to superductileity of the nano-ZrO2 ceramics, it couldn’t apply the formula of the common engineering ceramic material according to experimental results. The value of material coefficient ζ has relations with not only the material characteristics but also the processing methods and the processing parameters. It was proved that ζ has great effects on the accuracy of theoretical calculation. Experimental results showed that the critical ductility grinding depth of the nano-ZrO2 ceramics is up to 12 µm in common grinding methods, while in ultrasonic grinding is up to 20µm. The grinding chips with and without ultrasonic vibration assistance were discussed.

Abstract: In ELID (Electrolytic In-process Dressing) operations, the setting of starting point is quite important for reducing waste of time and for achiving high quality surface. In this study, the authors proposed a new describing mode for ELID grinding. The oxide layer formed on the wheel surface was divided to four sub-layer: porous-layer, polishing-layer, grinding-layer and interface-layer. The influence of the oxide layer on material removal rates and surface properties was investigated. It was found that, olny the oxide layer with thickness less than 24'm has capability of material removal. In ELID grinding, optimal thickness of the oxide layer is about 8~9'm. And the oxide layer with thickness of 4~9'm is suitable for grinding.

Abstract: As a special instantaneous bond, particle-dispersed Electrorheological-fluid (ER fluid) is used to cohere abrasive particles in the ER fluid so as to form dynamical tiny grinding wheel in grinding. This technique eliminates the dimension restriction of traditional concretion abrasive grinding wheel and is applicable in optics glass polishing to meet machining demands for micro-apparatus within millimeter or sub-millimeter microstructure. By regulating some parameters such as voltage, ingredient, volume rate of ER fluid, machining time, as well as distance between cone-tool and workpiece etc, the size, rigidity, and abrasive mutual combine-intensity of the micro grinding wheel can be controlled in order to achieve an expected machining effect. Experiments have been carried out by using SEM to analyze the characteristics in applying this technique.

Abstract: Polycrystalline diamond (PCD) composite sheet is a kind of material for cutter blank, which is formed by uniformly mixing micron diamond particles and metal binder powder such as Co and Ni, then sintered on WC under high pressure and high temperature. PCD tools have broad application and very high commercial value. However, compared with other materials, PCD tools’ service life relies greatly on blade sharpening quality. This paper just experimented on preparing precision blade of CTB002 PCD composite sheet on grinding machine of high precision diamond tools and with different performance parameters of TYROLIT diamond grinding wheel. Rotational speed of grinding wheel, grain size of grinding wheel and grinding pressure were researched in the orthogonal test method, which have the largest influence on grinding process, and influencing rules and the best combination of the three parameters are obtained.

Abstract: A size intelligent prediction control model during traverse grinding is constructed. The model is composed of the neural network prediction model, the deformation optimal adaptive control system and fuzzy control model. Dynamic Elman network is used in the prediction model. The first and the second derivative of the actual amount removed from the workpiece are added into the network input, which can greatly improve the prediction accuracy. The flexible factor is introduced to the fuzzy control model, which can self-adapt and adjust the quantification factor and scale factor in the fuzzy control. Simulation and experiment verify that the developed prediction control model is feasible and has high prediction and control precision.