Key Engineering Materials Vol. 499

Abstract: Numerical simulation of laser cladding is the main research topics for many universities and academes, but all researchers used the Gaussian laser light source. Due to using inside-beam powder feeding for laser cladding, the laser is dispersed by the cone-shaped mirror, and then be focused by the annular mirror, the laser can be assumed as the light source of uniform intensity.In this paper,the temperature of powder during landing selected as the initial conditions, and adopting the life-and-death unit method, the moving point heat source and the uniform heat source are realized. In the thickness direction, using the small melt layer stacking method, a finite element model has been established, and layer unit is acted layer by layer, then a virtual reality laser cladding manu-facturing process is simulated. Calculated results show that the surface temperature of the cladding layer depends on the laser scanning speed, powder feed rate, defocus distance. As cladding layers increases, due to the heat conduction into the base too late, bath temperature will gradually increase. The highest temperature is not at the laser beam, but at the later point of the laser beam. In the clad-ding process, the temperature cooling rate of the cladding layer in high temperature section is great, and in the low-temperature, cooling rate is relatively small. These conclusions are also similar with the normal laser cladding. Finally, some experiments validate the simulation results. The trends of simulating temperature are fit to the actual temperature, and the temperature gradient can also ex-plain the actual shape of cross-section.

Abstract: In order to enhance the efficiency of the Savonius rotor, this paper designs a new type of Savonius rotor with a rectifier. By using Computational Fluid Dynamics software to simulate and optimize the various parameters which affect the efficiency of the rotor. The sliding mesh method is applied here. The Cp-λ curves of wind turbine with different structural parameters are obtained after numerical simulation of flow field. On this basis, this paper gets the optimal structural parameters. And the results indicated that this new type of Savonius rotor has great improvement of efficiency compared with the traditional Savonius-type rotor.

Abstract: Diamond-coated drawing dies are considered as ideal drawing dies for their unique characteristics, such as high hardness, wear resistance and low friction. In order to utilize the superior characteristics of diamond coatings towards improving the drawing performance, the nonlinear FEM simulation is used to simulate the whole low carbon steel tube hollow sinking process, with 2D axi-symmetric elastic-plastic element. Based on the simulation results, the distributions of the axial stress and radial stress are analyzed, the influence of parameters of drawing dies on the diameter shrinkage is investigated. Optimal die parameters are obtained.

Abstract: In this study, an Al2O3-based functionally graded ceramic tool material reinforced with TiCN micro-particles and nano-Al2O3 particles was fabricated by using hot-pressing technique. The experimental results showed that optimal mechanical properties were achieved for the composite with the addition of nano-Al2O3 particles increasing from 10vol.% in the surface to 20vol.% in the core, with the flexural strength, fracture toughness and Vicker’s hardness being 1073MPa, 5.99MPa.m1/2 and 21.78GPa, respectively. The microstructure and phase composition of the composites were characterized with SEM, TEM and XRD. It is believed that addition of nano-Al2O3 increasing from the surface to the core, which developed an nano-particles-rich tougher core and a hard Al2O3/TiCN-rich surface, improved the integrated mechanical properties of micro-nano-composite graded ceramic material.

Abstract: For the technology of diamond cutting of optical glass, the high tool wear rate is a main reason for hindering the practical application of this technology. Minimizing the tool wear is of great significance in order to achieve the satisfactory surface quality and dimensional accuracy. For in depth understanding of the tool wear mechanisms, experiments of diamond turning with cutting distance increased gradually was carried out on soda-lime glass in this work. Experimental results indicate that the flank wear was predominant in diamond cutting glass and the flank wear land was characterized by micro-grooves, some smooth crater on the rake face was also seen. The mainly mechanisms inducing tool wear in diamond cutting of glass are diffusion, mechanical friction, thermo-chemical action and abrasive wear.

Abstract: Tool material has been one of the focuses in tool research. Diamond and cubic boron nitride (c-BN) are materials of exceptional and very similar properties that make them extremely valuable not only for the aesthetics of diamond. C-BN is a material synthesized rather recently that has rapidly spurred technological and scientific interest. Presently, both materials have found commercial applications. There is still a long way for the practical application of cBN film. The main problems are such as adhesion, thickness, purity, nucleating, and growth mechanism. We will develop a new way of DC plasma jet CVD way to synthesis the cBN film. The deposition of cBN films can be performed in a DC jet plasma CVD reactor by using an Ar-N2-BF3-H2 gas mixture, on the basis of deposition of diamond has been achieved.

Abstract: The relationship between fabrication pressure and microstructure evolution is proposed. A computer simulation coupled with fabrication pressure for the hot-pressing process of single-phase ceramic tool materials has been developed, which uses a two-dimensional hexagon lattice model mapped from the realistic microstructure without considering the presence of pores. The fabrication of single-phase Al2O3 is simulated. The mean grain size of simulated microstructure by Monte Carlo Potts model integrated with fabrication pressure increases with an increase in fabrication pressure, which is consistent with the experiment results. It is shown that Monte Carlo Potts model coupled with fabrication pressure may simulate the microstructure evolution of single-phase ceramic tool materials.

Abstract: A three dimension heat transfer model, using a commercial code Fluent software which was based on FEM, was developed to describe the grinding process of heat pipe grinding wheel in this paper. Temperature field of heat pipe grinding wheel was analyzed by this model to identify the effects of different conditions on the temperature of the work surface of grinding wheel including the heat flux of contact zone, cooling parameter and rotation speed of grinding wheel. The heat exchange performance of heat pipe grinding wheel also was studied based on the temperature of the work surface of grinding wheel. Model calculations showed that the high heat flux and unsatisfactory cooling capacity could cause a high temperature of the work surface of grinding wheel as well as the temperature of the work surface of grinding wheel was not affected by the rotation speed of grinding wheel. A significant amount of the input heat could be taken away from the heat pipe grinding wheel.

Abstract: There are some defects such as delamination and tools chipping etc. in drilling Ti/Carbon fibre interlaminated composites. To look for countermeasures, a special drill is developed considering tool material, geometry, coatings, cutting edge strengthening and drilling technology. The drill is comparable with imported tools as far as holes quality, efficiency and life are concerned. It is highly appreciated by customers.

Abstract: Isotropic pyrolytic graphite is a kind of graphite material. Because of its excellent performance, it is gradually used in aero-engine turbine shaft seals. But this material is a kind of brittle material, and it wears seriously during the cutting process. Through analysis of the process of cutting this material with PCD insert, the main wear region and the wear pattern at different cutting time were obtained. Using the scanning electron microscopy to observe the wear regions, the wear mechanism of PCD was obtained. At the first stage of the wear mechanisms were mainly mechanical wear and abrasive wear, the main wear regions were rake face and the cutting edge. With the increase of cutting distance, about 32 min later, both the depth of the crater on the rake face and the depth of micro grooves on the flank face were increased. Abrasive wear on the cutting face and the micro grooves wear on the flank face were the main wear pattern at the stable wear stage. At rapid wear stage, cutting edge was transformed from micro chipping into tool tipping. This caused by erosion wear .Experimental results indicated that the wear pattern was typical mechanical wear, abrasive wear, cutting edge erosion wear and possible adhesive wear.