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101.
102.
Tiffany Davis Ling Pinzhi Liu Shangwu Xiong Donald Grzina Jian Cao Q. Jane Wang Z. Cedric Xia Rajesh Talwar 《Tribology Letters》2013,52(1):113-122
Properly designed micro-scale surface textures can have positive impact on adhesion reduction and lubrication enhancement, which can lead to lower friction and improved performance of a contact interface. The present study aims to utilize this function of textures to reduce the adhesion between a drill and a workpiece. In this study, rectangular surface textures were generated on the margins of drill bits using a diode-pumped Nd:YVO4 picosecond laser with a wavelength of 532 nm. Two designs were created in which the textures covered approximately 10 and 20 % of the margin surface area. Textured drills were tested by drilling a series of holes in a titanium plate while recording cutting forces, and the results were compared with the performance of baseline samples. Thermographic heat profiles and visual inspections of the drills were taken at increments of 5 and 10–15 holes, respectively. The comparison demonstrated an encouraging improvement in drill bit life as judged by the number of holes drilled before failure. Textured drills were found to reduce adhesion of titanium chips on the drill margins. This work has demonstrated the potential of texturing to significantly improve the lifetime of drill bits and similar cutting tools. 相似文献
103.
内蒙古苏里格甲醇厂一套天然气制甲醇合成气的装置原采用一段外热蒸汽转化工艺.甲醇生产能力为18×10^4t/a。与外加热蒸汽转化工艺相比,轻烃自热转化大约用1m^3 O2可替代0.5m^3 CH4,采用天然气纯氧自热转化制甲醇合成气的两段转化工艺(增设二段炉)进行改造,可增加甲醇生产能力15×10^4t/a,配套改造投产后甲醇生产能力可达到33×10^4t/a,改造后生产甲醇的天然气消耗量由1100m^3/t(标准)下降为960m^3/t(标准)。所用自热转化工艺采用多气流转化炉与低温混合喷射外燃式烧嘴配套的创新技术,该技术的成功应用,达到了节气12.7%、增产83.3%的目的。采用该新工艺生产甲醇合成气可节省原料天然气20%~30%,减排CO2 70%~95%。 相似文献
104.
对比分析了 C/ C和 C/ SiC刹车材料的力学性能和摩擦磨损性能。结果表明 , C/ SiC刹车材料的力学性能比 C/ C的高 , 而且 C/ SiC刹车材料克服了 C/ C静态摩擦系数低和湿态摩擦性能严重衰减的不足 , 说明 C/ SiC刹车材料是一种新型高性能刹车材料。以 C/ C复合材料为基础 , 在深入分析机轮刹车盘服役环境特点的基础上探讨了 C/ SiC刹车材料的力学性能、 热物理性能、 摩擦磨损性能、 复合材料结构和制造工艺等方面的优化设计途径和方法 , 为实现材料微结构2力学性能2摩擦磨损性能的协同设计与制造奠定基础。 相似文献
105.
Shangwu Fan Yifan Ning Xu Ma Chuan Yang Liuyang He Juanli Deng Laifei Cheng Litong Zhang 《Ceramics International》2018,44(13):15200-15207
FeSi2 modified C/C-SiC composites (C/C-SiC-FeSi2) are fabricated by chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI) with FeSi75 alloy. The effects of high-temperature annealing (1600?°C, 1650?°C, 1700?°C) on the microstructure and performance of C/C-SiC-FeSi2 are investigated. With the elevation of annealing temperature, the porosity of the composites and the content of SiC increase due to the evaporation of liquid Si and the further reaction of Si and C. The mechanical performance gradually decreases due to the catalytic graphitization of the carbon fiber, the high porosity and the thermal residual stress (TRS) caused by thermal mismatch of different phases. The coefficient of thermal expansion and thermal diffusivity slightly decrease with increasing annealing temperature for the increase of porosity. However, the friction performance of the heat treated materials at high braking speed are greatly improved attributing to the increase of SiC content and the capturing and storage function of pores on hard particles. 相似文献
106.
Haodong Sun Shangwu Fan Le Wang Xu Ma Juanli Deng Laifei Cheng Litong Zhang 《Ceramics International》2021,47(11):15568-15579
A combination method of precursor infiltration and pyrolysis (PIP), chemical vapor infiltration (CVI) and liquid silicon infiltration (LSI) was proposed to prepare PIP-SiC modified C/C–SiC brake materials. The SiC ceramic matrix pyrolyzed by polymethysilane (PMS) homogeneously dispersed in the fiber bundles region, which improved the plough resistance of local C/C region and the wear resistance of C/C–SiC brake materials. When the braking speed rises to 28 m/s, the fluctuation range of friction coefficient was limited to 0.026. The linear wear rate of the as-prepared composites was could be ~50% less than that of C/C–SiC, when the braking speed was above 15 m/s (for instance, the wear rate of 1.02 μm/(side·cycle) at 28 m/s less than 2.02 μm/(side·cycle) of traditional C/C– SiC). The fading ratio D of CoF under wet conditions was ~11%. The results showed that introducing PIP-SiC could stabilize the braking process and effectively prolong the service life of C/C–SiC brake materials. 相似文献
107.
在面向社区楼道或门栋监控中,人脸信息尤为重要。通过NB-IoT(窄带物联网)接入,可以满足低成本、广覆盖和多接入的需求,但是常规编码方法在窄带低码率下无法保障人脸质量。针对该问题,提出一种面向人脸业务的混合分辨率监控视频压缩方法。利用监控视频统计特性优化人脸检测速度,采用不同分辨率区别编码人脸和非人脸区域,在高倍率压缩下提高了人脸的可辨识性。实验表明,该方法相较于主流感兴趣区域编码,人脸区域PSNR提高了5.57 dB,编码速度提高了5.12倍,具备NB-IoT环境下的实用性。 相似文献
109.
C/SiC–ZrB2–ZrC composites were prepared by reactive melt infiltration (RMI) combined with vacuum pressure impregnation (VPI) method. B4C–C was first introduced into C/SiC composites with a porosity of about 30% by impregnating the mixture of B4C and phenol formaldehyde resin, followed by pyrolysis at 900 °C. The molten ZrSi2 alloy was then infiltrated into the porous C/SiC–B4C–C to obtain C/SiC–ZrB2–ZrC composites. The flexural strength was tested. The ablation behavior was investigated under an oxyacetylene torch flame. It has been found that the C/SiC–ZrB2–ZrC showed a high flexural strength and an excellent ablation resistance. The reactions between ZrSi2 alloy and B4C–C were studied, and a model based on these reactions was built up to describe the formation mechanism of the matrix. 相似文献
110.