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111.
通过改变高速车削淬火钢(Cr12)的切削用量,对切削力、切削温度、加工表面质量等进行了研究,结果表明合理选择切削用量,高速硬车削淬火钢可显著提高生产率及加工表面质量,并在一定程度上可取代磨削加工。 相似文献
112.
For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 106 cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30-50 μm) than those generated under oil-based cooling mode (i.e., 150-200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed. 相似文献
113.
非接触型光外差轮廓仪 总被引:1,自引:0,他引:1
本文介绍一种纳米级非接触型高精度光外差轮廓仪,它是基于普通光路的光外差干涉仪。工件表面被两束有微小频差的激光束所照射,其中一束经聚焦后用作测量光探针来扫描工件表面,另一束则用作参考光束。两束光经表面反射后产生干涉。测量信号和参考信号的相位差与表面的微不平值成正比。仪器的横向分辨率为2μm,高度分辨率为1 nm,它不需要对试样作大范围的调整,且可用试样自身作参考面。信号经光电转换后由微型计算机进行处理,它能快速完成测量、计算、显示及打印出各种参数和曲线。 相似文献
114.
Studies on the effect of temperature on the development of the yam moth, Dasyses rugosella Stainton were carried out in the laboratory at four different temperatures, 20°C, 24°C, 29°C and 33°C. The mean fecundity per female at 20°C, 24°C, 29°C and 33°C was 37.6±1.9, 84.2±2.7, 112.3±3.9 and 109.3±3.9 eggs, respectively. Oviposition period ranged from 4.7 days at 20°C to 2.9 days at 33°C. Hatchability of eggs was highest at 29°C with 70.0% and lowest at 20°C with 15.0%. The developmental time decreased with increase in temperature. The mean developmental time at 20°C, 24°C, 29°C and 33°C was 13.8±0.3, 7.8±0.2, 5.1±0.2 and 3.9±0.2 days for the egg, 90.0±0.7, 50.1±0.7, 36.1±0.8 and 23.6±0.8 days for the larval stages, 22.3±2.6, 12.2±0.2, 10.1±0.1, and 7.8±0.2 days for the pupa and 126.1±0.8, 70.1±0.8, 51.3±0.9, and 35.1±0.8 days for the period from egg hatching to adult emergence, respectively. Since fecundity, oviposition and development of the moth were impaired at 20°C, storage of yam tubers at low temperatures (well below 20°C but not lower than 12°C to avoid chilling injury) will significantly retard the development of D. rugosella and help in its control. Unmated individuals lived longer than their mated counterparts. Adult females were always larger than the males. The wing span of the female ranges from 16.9-18.5 and in males from 13.0-15.0 mm. The body length for males ranged from 5.0-6.5 and was 6.5-9.0 mm for females. 相似文献
115.
Different fluorination methods were applied to modify the surface properties of carbon fibers. The relationship between the degree of fluorination and the physicochemical properties of carbon fibers was studied using a combination of mechanical tests, elemental analysis (EA), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD). EA and XPS analyses of fluorinated carbon fibers showed that treatment with mixtures of F2/O2 introduced a much higher fluorine concentration than that with F2 only. However, XRD analysis showed that there was no increase in the interlayer distance, due to the mild fluorination condition applied. Consequently, the oxyfluorination was one of the more effective methods to increase surface polarity of carbon fibers, which probably played an important role in improving the tensile properties of the fibers in the epoxy resin system. 相似文献
116.
M.A Lillo-Ródenas 《Carbon》2003,41(2):267-275
Direct mixing of an anthracite with hydroxides (KOH or NaOH) and heat treatment up to 730 °C has shown to be a very good activation procedure to obtain activated carbons with very high surface areas and high micropore volumes. The reactions involved during the heat treatment of these hydroxide/anthracite mixtures have been analysed to deep into the fundamental of the knowledge of this chemical activation process, that has not been studied before. For this purpose, the present paper analyses the drying process, the atmosphere during the carbonisation, the chemical state of the activating agents (NaOH, KOH and Na2CO3) and the chemical reactions occurring during the heat treatment which have been followed by FTIR and TPD. The analysis of our results allows us to conclude that steam is a good atmosphere for the carbonisation process, alone or joined with nitrogen, but not as good as pure nitrogen. On the other hand, during the activation process, the presence of CO2 should be avoided because it does not develop porosity. The reactions, and chemical changes, involved during this chemical process are discussed both from a thermodynamical point of view as well as identifying the reaction products (H2 by TPD and Na2CO3 by FTIR). As a result, this paper helps to cover the present lack of understanding of the fundamentals of the reactions of an anthracite with hydroxides which are necessary to understand the activation of the material. 相似文献
117.
Shafeeque G. Ansari Mushtaq Ahmad Dar Young-Soon Kim Hyung-Kee Seo Gil-Sung Kim Rizwan Wahab Zubaida A. Ansari Jae-Myung Seo Hyung-Shik Shin 《Korean Journal of Chemical Engineering》2008,25(3):593-598
A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with
1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force
microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma
etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance
of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched
substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers.
Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332
cm−1 and a peak at ∼1,580 cm−1 for both samples. 相似文献
118.
119.
随着变频调速技术的蓬勃发展,变频器供电电机的温升问题已引起人们的广泛关注。本文首先讨论了电动机的温升限度;然后结合感应电机温升实验的相关数据分析了变频器供电对电动机温升的影响及其原因;最后从降低发热量和提高散热能力两方面提出缓解电机温升的措施,并指出了实际应用中应注意的问题。 相似文献
120.
Ahmad Nozad Golikand Elaheh Lohrasbi Mohammad Ghannadi Maragheh Mehdi Asgari 《Journal of Applied Electrochemistry》2008,38(6):869-874
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by
cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms,
polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface
area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The
formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of
a gas diffusion electrode for oxygen reduction reaction. 相似文献