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采用有限元的方法来模拟纳米压痕实验的加、卸载过程,采用的是简化了的二维模型,有限元模型考虑了纳米压痕的标准Berkovich压头,介绍了有限元模型的几何参数、边界条件、材料特性与加载方式。从所得到的载荷与压入深度的关系曲线,以及由此计算而得到的硬度-位移曲线等为依据,对在纳米压痕测试过程中,不同的晶粒截面形状以及截面面积对整体材料的力学性能的影响进行了分析讨论。研究表明,在晶粒截面面积相等的情况下,当纳米压痕实验压入相同的深度时,晶粒的截面形状为矩形的材料的硬度高于晶粒的截面形状为三角形的材料的硬度,而且,当晶粒的截面形状相同的情况下,整体材料的硬度与晶粒截面的面积存在一种近似的正比例关系。这种研究结果说明,即使在材料相同的情况下,如果晶粒的截面形状不同,由于力学传递关系的不同,仍然能够使得薄膜具有不同的宏观力学性能。 相似文献
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针对深部岩土工程岩石参数获取成本高的问题,本研究借鉴压痕试验技术,研制了钻孔横向贯入仪,用于在钻孔中测定岩石的相关岩石力学参数。该设备具有便携、快捷、高效、低成本的特点。该设备通过获取4个不同曲率半径的压头在压入过程中的载荷-位移曲线,并对这些曲线进行分析从而获取岩石的相关力学参数。在大理石上进行钻孔横向贯入仪的初步应用,并在试验中引入声发射监测塑性变形的发展情况,揭示试验的压入曲线特性,从试验曲线中提取岩石的模量,通过与单轴试验结果进行对比,用钻孔横向贯入仪试验曲线提取的模量介于单轴试验的割线模量和弹性模量之间,并且与割线模量较为接近。认为钻孔横向贯入仪的试验结果可以代表现场岩石的力学参数,可供工程参考。 相似文献
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《Planning》2019,(6)
采用高功率脉冲磁控溅射技术在GH169高温合金表面沉积了TiN纳米涂层,利用XRD、SEM、纳米压痕仪等研究了负偏压对涂层的晶体结构、表面形貌、涂层厚度及力学性能的影响。结果表明:随着负偏压从50 V增加到200 V,TiN(111)晶面择优取向,涂层晶粒细化,致密度增加,表面粗糙度减小,涂层沉积速率降低(涂层厚度减小),涂层硬度和弹性模量呈现先减小后增大再减小的趋势,而膜基结合强度则是先增加后降低。当负偏压为150 V时,TiN涂层晶粒尺寸最小,致密度最好,综合力学性能最佳。 相似文献
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用冲击球压法研究了混凝土在室外、水和硫酸盐溶液中的压痕-应力关系和接触损伤的规律。结果表明:在不同环境下硬化阶段的混凝土的弹性模量随着龄期而增长,其中在硫酸盐溶液中增加最快,水中试件弹性模量次之,室外试件弹性模量增长最慢;对90d试件进行高温后的试验结果表明:水中试件表面力学性能降低程度最大,硫酸盐溶液中试件次之,室外试件降低程度最小,随着环境的逐步恶化,混凝土表面力学性能与整体力学性能之间的差距逐渐缩小。另外,对用球接触方法评价混凝土材料表面损伤程度的可行性和简便性进行了验证。 相似文献
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低碳城市规划:寻求低碳化发展 总被引:5,自引:0,他引:5
我们需要追求一种理想的"低碳"城市模式,来化解由于工业革命以来200年的"高碳"城市给人类社会带来的灾难风险。要发展理想的低碳城市,低碳城市规划理论和方法是必然的关键技术。仅仅通过节能减排的技术手段还不足以解决减少CO2排放问题,还需要以更加多元的标准衡量城市规划与建设,通过低碳城市规划寻求城市发展的低碳化方向,探索面向可持续未来的低碳城市发展模式。 相似文献
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In this study, the pyrolytic behaviors and the thermal-oxidation decomposition characteristics of organic carbon (OC), pyrolytically generated elemental carbon (PEC) and black carbon (BC) particles have been studied in inert and air atmosphere respectively, in order to develop a new PEC correction method for the determination of BC by using thermal oxidation method. Our results indicated that: 1) a part of OC can be removed by heating it at 400 °C in inert atmosphere and another part of OC was charred to form PEC, whereas, the weight of BC particles approximately keeps no change in the same conditions. 2) PEC and BC began to decompose at a similar temperature in air atmosphere. However, the decomposition rate of PEC is quite different from that of BC in air atmosphere and the difference varied with the temperature. As maximum, the decomposition rate of PEC is 5.64 times faster than that of BC particles at 500 °C in air atmosphere. Based on the difference of the decomposition rate between PEC and BC, a new method of PEC correction was developed for the thermal oxidation method. With the help of the new PEC correction method and thermal analyzer, we successfully determined OC and BC concentrations in actual soot sample and artificial soot samples. The results obtained with our PEC correction method are consistent well with the real value or those analyzed with thermal-optical method, suggesting that the novel PEC correction method have a high accuracy. 相似文献
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《Planning》2014,(2)
通过建立碳/碳(C/C)复合材料在宏观、微观不同尺度上的烧蚀模型,利用有限元方法分析了C/C复合材料在烧蚀过程中的体积损失、表面粗糙度以及烧蚀性能的变化规律。微观上,模拟了材料烧蚀呈现的尖笋状粗糙度形貌。宏观上,采用ALE方法,并基于实验结果通过Fortran编程控制材料表面烧蚀后退运动,建立了C/C复合材料表面烧蚀的多尺度热力耦合分析模型,并进行瞬态有限元分析。结果表明:材料烧蚀表面粗糙度程度与烧蚀速率、材料性能密切相关;并且随着材料烧蚀程度的不同,材料的表面应力也相应变化。 相似文献
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D. P. Healy 《Building Research & Information》2013,41(3):317-326
The carbon intensity of electricity is a key input to calculations of carbon emissions from buildings, and can be decisive in the selection of low- and zero-carbon technologies. The origin of the value for the carbon intensity of electricity is not well understood and its derivation is investigated. The carbon savings from gas-fired combined heat and power (CHP) vary greatly depending on the carbon intensity of electricity. The current debate about the effectiveness of CHP centres on detailed considerations about which values for the carbon intensity of electricity should be used. The expected future decarbonization of the electricity supply grid would considerably reduce carbon intensities, thus the longer-term trends in carbon intensity and their effect on the carbon savings from CHP are of greater importance. A new expression has been developed to describe the carbon savings from CHP and trigeneration as a function of varying carbon intensity of electricity. While CHP can offer limited carbon savings in the short-term, the future decarbonization of the electricity grid means that CHP will soon be among the most carbon-intensive technologies, and the use of trigeneration will cease to provide carbon savings even sooner. L'intensité carbone de l'électricité est un élément clé de calcul des émissions de carbone des bâtiments et peut être décisive dans le choix des technologies bas carbone et zéro carbone. L'origine de la valeur de l'intensité carbone de l'électricité n'est pas bien comprise et son mode de calcul est étudié. Les économies de carbone réalisées grâce à la production combinée chaleur-électricité (PCCE) issue du gaz varient considérablement selon l'intensité carbone de l'électricité. Les débats actuels sur l'efficacité de la production combinée chaleur-électricité (PCCE) se concentrent sur des considérations détaillées relatives aux valeurs qui devraient être utilisées concernant l'intensité carbone de l'électricité. La future décarbonisation prévue du réseau de distribution d'électricité réduirait considérablement les intensités carbone, de sorte que les tendances à plus long terme en matière d'intensité carbone et leur effet sur les économies de carbone réalisées grâce à la PCCE sont de la plus grande importance. Il a été élaboré une nouvelle expression permettant de décrire les économies de carbone réalisées grâce à la PCCE et à la trigénération comme étant une fonction de l'intensité carbone variable de l'électricité. Bien que la PCCE puisse assurer à court terme des économies de carbone limitées, la future décarbonisation du réseau de distribution d'électricité signifie que la PCCE figurera bientôt au nombre des technologies affichant les plus fortes intensités carbone et que l'utilisation de la trigénération cessera encore plus tôt d'assurer des économies d'énergie. Mots clés: réglementation du bâtiment, émissions de carbone, intensité carbone de l'électricité, production combinée chaleur-électricité (PCCE), technologies bas carbone et zéro carbone, bâtiments bas carbone, trigénération 相似文献
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Nineteen solvents were evaluated in batch tests involving the desorption of a representative organic adsorbate (phenol) from activated carbon. Three of the better solvents which also possess complete miscibility with water (acetone, dimethylformamide, methanol) were tested further in fixed-bed runs. The effects of solvent temperature and solvent flow rate on phenol desorption were evaluated. In addition, the recovery of phenol adsorption capacity by an activated carbon bed operated cyclically using a sequence of phenol adsorption, desorption with methanol, and rinsing with water was determined. It was found that solvent temperature and flow rate are not critical variables. Solvent volume and type were the most important factors in phenol desorption. A modest volume of methanol restored 88% of the fixed-bed adsorption capacity for phenol after 1 regeneration, and the capacity essentially leveled off after 5 regenerations at a value of 81% of the capacity of fresh carbon. Methanol regeneration is effective, easy to perform and offers convenient solvent recovery. Thus, it is an attractive alternative to thermal regeneration methods. 相似文献
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Petersen G Viviani D Magrini-Bair K Kelley S Moens L Shepherd P DuBois D 《The Science of the total environment》2005,338(3):159-182
Carbon dioxide (CO2) is considered the largest contributor to the greenhouse gas effect. Most attempts to manage the flow of CO2 or carbon into our environment involve reducing net emissions or sequestering the gas into long-lived sinks. Using CO2 as a chemical feedstock has a long history, but using it on scales that might impact the net emissions of CO2 into the atmosphere has not generally been considered seriously. There is also a growing interest in employing our natural biomes of carbon such as trees, vegetation, and soils as storage media. Some amelioration of the net carbon emissions into the atmosphere could be achieved by concomitant large withdrawals of carbon. This report surveys the potential and limitations in employing carbon as a resource for organic chemicals, fuels, inorganic materials, and in using the biome to manage carbon. The outlook for each of these opportunities is also described. 相似文献