共查询到20条相似文献,搜索用时 78 毫秒
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基于实验观察和理论研究, 重点分析了材料内部区域纤维束的空间构型, 建立了一个新的三维实体细观结构模型, 并指出了编织工艺参数和模型细观结构参数之间的关系。该模型较真实地反映了纤维束之间的相互挤压变形方式, 纤维束横截面积沿纤维束轴向不断变化, 更符合三维四向编织复合材料的实际结构。基于刚度体积平均及柔度体积平均混合思想, 建立了相应的刚度预报模型。用该模型计算编织复合材料几何特性及工程弹性常数的数值结果与试件实测数据吻合, 表明了该模型的合理有效性, 为进一步研究三维编织复合材料的拉伸强度及破坏机制提供了基础。 相似文献
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通过对炭/炭复合材料纤维束界面不同成型阶段结构和性能的研究, 探索束界面在制备过程中的形成规律. 采用顶出实验、SEM、Micro-CT、XRD以及Raman对不同成型阶段的炭/炭复合材料中纤维束/基体界面剪切强度、界面层结构进行了分析. 结果发现材料密度较低时, 石墨化程度增加不利于束界面剪切强度的提高; 随着材料密度的增大, 束界面剪切强度明显升高. 通过对其界面结构进行分析, 可以看出在沥青浸渍、炭化和石墨化的制备过程中, 炭基体优先在束内形成, 然后逐步向束界面层及束间空间发展, 最后束界面层组织结构趋于完善. 随着热处理温度的升高, 其界面层组织结构的石墨化程度逐渐增强, 其结晶程度也不断增强. 相似文献
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为了研究光纤与宽波导光栅的有效耦合,基于高斯光束与波导光栅的光耦合理论,以30μm宽波导光栅为研究对象,利用矩阵光学和高斯光束理论分析和设计了一种扩束光纤,并通过分析其耦合损耗,建立了扩束光纤与波导光栅耦合模型.优化所设计扩束光纤的结构参数后,得到束腰半径为10.8μm的输出光束.最后分析了扩束光纤的结构容差,并讨论了所设计扩束光纤的输出光束、单模光纤的输出光束以及束腰半径为16 μm的自由空间高斯光束各自在光栅表面的位置变化对光栅耦合效率的影响.可知扩束光纤输出的光束与单模光纤输出的光束相比具有较大的位置容差,与束腰半径为16 μm的自由空间高斯光束相比,光耦合效率基本相同. 相似文献
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玻璃纤维增强灌注型聚氨酯泡沫塑料的微观结构和增强 … 总被引:4,自引:0,他引:4
对玻璃纤维增强聚氨酯泡沫的微观结构形态及增强效果进行了研究。结果表明,纤维在体系内呈单根纤维,小束纤维及大束纤维等多种形态分布。单丝及小丝束可以成为泡沫结构的共同支柱而起增强作用,在小束丝附近出现密集泡孔,发生少量树脂积聚。 相似文献
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一种新型板束结构的板翅式换热器的数值模拟和优化设计 总被引:1,自引:0,他引:1
换热器是热力系少轴向导热的影响,设计出的换热器往往很长.为了使换热器的结构型式更为紧凑合理,提出了一种新型板束结构,将换热器沿长度方向折叠.对物理模型用有限元的方法进行了数值模拟,对新型板束结构换热器的传热性能和压力损失进行分析.计算发现,合理选择板束间隔热片的材料和厚度,可以使新型板束结构的板翅式换热器在保持优良传热性能的基础上,实现高效紧凑、布局合理的良好效果. 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献