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排序方式: 共有861条查询结果,搜索用时 15 毫秒
41.
H.A. Castillo P.J. Arango E. Restrepo-Parra G. Soto 《Surface & coatings technology》2010,204(24):4051-2681
Cubic boron-carbon-nitrogen c-BC2N films were synthesized in a laser ablation system using a target of B4C with 99.99% of purity and silicon substrates (111). The discharge atmosphere for the films growth was a CH4 + N2 mixture. The substrate temperature increased from room temperature to 650 °C. The chemical composition and bonding configuration were studied by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), finding B-N, B-C and C-C bonds. Moreover, the crystallographic microstructure was analyzed by means of X ray diffraction (XRD) and transmission electron microscopy (TEM), showing the presence of (111), (200) and (220) planes belonging to a diamond like cubic structure. Finally, an increase in the coating hardness as a function of the substrate temperature was observed, especially for temperatures higher than 530 °C. 相似文献
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43.
The role of in situ stirring under microwave-hydrothermal (M-H) conditions on the synthesis of barium titanate was investigated for the first time by powder X-ray diffraction and scanning and transmission electron microscopy. Stirring under M-H conditions in the temperature range of 150–200 °C led to enhanced crystallization of Ba titanate as revealed by yields compared to the static condition. In addition, stirring led to smaller and more uniform crystals under M-H conditions compared to those crystallized without stirring. Powder X-ray diffraction revealed the formation of only cubic polymorph of Ba titanate at or below 200 °C in 4 h with or without in situ stirring under M-H conditions. These results show that stirring is an important parameter during M-H synthesis of nanophase Ba titanate. 相似文献
44.
Prediction of flank wear by using back propagation neural network modeling when cutting hardened H-13 steel with chamfered and honed CBN tools 总被引:1,自引:0,他引:1
Productivity and quality in the finish turning of hardened steels can be improved by utilizing predicted performance of the cutting tools. This paper combines predictive machining approach with neural network modeling of tool flank wear in order to estimate performance of chamfered and honed Cubic Boron Nitride (CBN) tools for a variety of cutting conditions. Experimental work has been performed in orthogonal cutting of hardened H-13 type tool steel using CBN tools. At the selected cutting conditions the forces have been measured using a piezoelectric dynamometer and data acquisition system. Simultaneously flank wear at the cutting edge has been monitored by using a tool makers microscope. The experimental force and wear data were utilized to train the developed simulation environment based on back propagation neural network modeling. A trained neural network system was used in predicting flank wear for various different cutting conditions. The developed prediction system was found to be capable of accurate tool wear classification for the range it had been trained. 相似文献
45.
46.
C. E. Becze P. Clayton L. Chen T. I. El-Wardany M. A. Elbestawi 《International Journal of Machine Tools and Manufacture》2000,40(6):869
This paper investigates critical issues related to high-speed five-axis milling of hardened D2 tool steel (hardness HRc 63). A forging die cavity was designed to represent the typical features in dies and molds and to simulate several effects resulting from complex tool path generation. Cutting tool materials used were coated carbide for the roughing and semi-finishing processes and polycrystalline cubic boron nitride (PCBN) for the finishing process. The effects of complex tool paths on several critical machining issues such as chip morphology, cutting forces, tool wear mechanisms, tool life and surface integrity were also investigated. The main tool failure mode was chipping due to the machine tool dynamics. A five-axis analytical force model that includes the cutter location (CL) data file for computing the chip load has been developed. The effect of instantaneous tilt angle variation on the forces was also included. Verification of the force model has been performed and adopted as a basis for explaining the difficulties involved with high-speed five-axis milling of D2 tool steel. 相似文献
47.
提出一种通过控制六面顶压机冷却水的冷却功率来提高金刚石合成块温度控制精度的方法,设计了精度达0.5%的三线制热电阻温度采集电路、脉冲型涡轮流量计的信号采集电路和步进电机驱动电路。在STM32平台上,实现了步进电机的加减速控制和高精度脉冲频率的测量。结合带死区的增量式PID控制算法,获得了良好的冷却功率控制效果。 相似文献
48.
为了解UR5机器人实时轨迹变化情况,根据Denavit-Hartenberg参数法在MATLAB Robotics Toolbox中利用Link函数建立了UR机器人的三维数学模型,对UR5机器人进行了正、逆运动学求解与理论分析,推导出各个关节角之间的变化关系;利用三次多项式插值法对任意PTP (点到点)之间的空间轨迹规划进行理论分析,并结合MATLAB Robotics工具箱对UR5机器人数学模型进行了空间轨迹规划和仿真,得到了连续变化的轨迹曲线。仿真结果验证了机器人运动学模型的正确性和合理性,为UR系列机器人的进一步研究和应用提供了理论依据。 相似文献
49.
Theory and experimental calibration of density dependent modified Drucker-Prager/Cap (DPC) model are presented by using a novel instrumented cubic die in powder compaction tests. The cubic die is designed for directly determining the loading and unloading forces and displacements of powder compact inside the die in compaction and transverse directions without any additional calibration. The cap surface parameters and elastic properties are characterized by fitting stress and strain curves recorded during loading and unloading at different green density values and the plastic material parameters for failure surface are obtained by additional radial and axial compressive tests. The experimental data is subsequently used in the simulation of cubic die compaction to verify the results from the density dependent modified DPC model. 相似文献
50.
Y.M. Chong W.J. Zhang Y. Yang Q. Ye I. Bello S.T. Lee 《Diamond and Related Materials》2009,18(11):1387-1392
Cubic boron nitride (cBN) thin films were deposited on diamond-coated tungsten carbide (WC) cutting inserts using electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD). The effects of gas flow rate and substrate bias on the phase composition and structure of the BN films deposited on diamond surfaces were studied. It was revealed that both the cubic phase formation and the selective etching of hexagonal phase were controlled by modulating the hydrogen and boron trifluoride flow rate ratio. By the trial and error method the gas flow rate ratio and substrate bias voltage were optimized. Moreover the phase composition of the BN film was found to be affected by the thickness of diamond buffer layer and interrelated to the effective substrate bias. The hardness of the resulting cBN films reached the value of 70 GPa. In the synthesized coatings, the diamond beneath renders the best mechanical supporting capacity while the top cBN provides the superior chemical resistance and extreme hardness. The cBN/diamond bilayers deposited on WC inserts may serve as universal tool coatings for machining steels and other ferrous metals. 相似文献