碳纤维束间的摩擦磨损特性

为了对碳纤维束的磨损程度进行定量分析以及探索碳纤维束间摩擦磨损机制,采用自制的摩擦模拟实验装置,研究了摩擦次数、加载力、摩擦角度对碳纤维束摩擦损伤的影响。通过对比摩擦前后碳纤维束的拉伸断裂强力、毛羽量和表面浆膜形态评价了其磨损程度。结果表明:随着摩擦次数、加载力的增大,碳纤维束的磨损程度逐渐加剧;当摩擦角度在90°~30°范围变化时,碳纤维束的拉伸断裂强力随着角度的减小而小幅度下降;而当摩擦角度为0°时,碳纤维束的拉伸断裂强力急剧下降。同时,结合纤维束接触理论和黏性薄膜压痕法揭示了碳纤维束摩擦损伤机制,发现有效接触面积的变化是导致碳纤维束磨损程度改变的主要因素,且纤维束间的有效接触面积随加载力的增大而增大,随摩擦角度的增大而减小。      

不同冲蚀角条件下QAl9-4铝青铜的冲蚀磨损特性

利用自主研发的转盘式冲蚀实验装置,通过失重分析、表面形貌观察以及表层粗糙度测定,探讨了QAl9-4铝青铜在不同冲蚀角度条件下的冲蚀磨损特性。结果表明,在0~30°冲蚀角度范围内,铝青铜试样的累积质量损失随角度增大而增加;当冲蚀角度大于30°后,累积质量损失降低。随着冲蚀角度的逐步增大,冲蚀磨损形成的试样表面缺陷逐渐从沿水流方向的长程犁沟向带有凹坑的短程犁沟变化,且试样表面平均粗糙度逐渐降低。     

乘用车前挡风玻璃角度对行人头部/颅脑损伤影响研究

头部/颅脑损伤在车辆与行人碰撞事故中频繁发生,而行人头部与挡风玻璃的碰撞是导致头部损伤的主要原因。旨在采用数值模拟方法研究乘用车挡风玻璃倾斜角度对行人头部/颅脑损伤的影响。采用TNO多刚体行人模型和THUMS4.0头颈部有限元模型耦合得到新的行人碰撞数值模型,并结合已有的多刚体乘用车模型,借助真实的行人碰撞交通事故案例对该耦合模型进行基于人车动力学响应的有效性验证。在此基础上,构建人车碰撞模型矩阵,其中挡风玻璃角度的变化范围设定为24°~50°(间隔为2°),车辆速度设置为45 km/h,行人与车辆碰撞位置时分别处于车辆前保险杠前端1/2和1/3处。分析结果表明,该耦合模型可以较准确地再现事故中的行人动力学响应;行人碰撞保险杠前端中间(即1/2处)位置时的头部损伤较1/3处更严重;头部损伤在本文所分析的变化范围内随挡风玻璃角度的增加呈先减小后增加的变化趋势,且当挡风玻璃角度位于32°~34°左右时损伤风险较低。     

考虑艏摇的半潜式平台涡激运动试验研究

为研究半潜式平台的涡激运动特征,进行了水槽模型试验研究。测试了流向角为0°、15°、30°及45°时,在不同来流速度下半潜式平台的横荡、纵荡及艏摇运动响应;并以艏摇运动为重点,从响应幅值、运动频率等角度出发,探讨其涡激运动的关键特征。结果表明:在不同来流方向情况下,半潜式平台均未发生明显的频率锁定现象。当流向角为0°和15°时,平台三自由度响应随约化速度的增加近似呈线性增大的趋势;当流向角为30°和45°时,在约化速度4～10附近平台响应出现了明显的共振现象,并在此现象结束后响应大幅减小,之后,随着约化速度的增加再次大幅增大。除个别工况外,艏摇与横荡均高度耦合,其响应频率主峰值基本保持1∶1关系;艏摇固有周期对平台三自由度运动频率及幅值影响均不明显。流向角为45°时,平台的艏摇运动最为剧烈,在各个约化速度下响应幅值均数倍于其他流向角。另外,在0°流向角时观察到了"驰振"现象;15°流向角的多个约化速度下观察到了"自激"现象。     

冲蚀角度对建筑用钢化玻璃和普通玻璃喷砂磨损粗糙度的影响及三维分析

采用气流挟沙喷射法对钢化玻璃和普通玻璃在不同角度下进行冲蚀试验,利用激光共聚焦显微镜(LSCM)和扫描电子显微镜(SEM)表征玻璃表面微观结构和形貌的变化,对比研究了冲蚀角度对建筑用钢化玻璃和普通玻璃喷砂磨损粗糙度和损伤形貌的影响和机制.研究结果表明:随着冲蚀角度的增加,钢化玻璃和浮法玻璃的冲蚀率均逐渐增大,冲蚀损伤区域深度和宽度也逐渐增大,损伤区域形状由椭圆向圆形转变,冲蚀剖面轮廓由抛物线形向圆锥形转变.钢化玻璃的粗糙度随冲蚀角度增加逐渐增大,浮法玻璃粗糙度随冲蚀角度增加先增后减,冲蚀角度为45°时达到最大.相同冲蚀角度下,浮法玻璃的损伤程度远大于钢化玻璃.当冲蚀角度为15°时,材料的损伤由沙粒微切削作用引起,材料表面粗糙度较小;冲蚀角度为45°时,材料的损伤由沙粒切削和裂纹扩展共同引起,沙粒铲削作用明显,材料表面粗糙度大;冲蚀角度为90°时,材料的损伤由裂纹叠加引起,钢化玻璃的粗糙度达到最大而浮法玻璃的粗糙度达到最小.冲蚀角度为15°和45°时,浮法玻璃表面粗糙度参数均大于钢化玻璃,冲蚀角度为90°时,钢化玻璃粗糙度评价参数均大于浮法玻璃.钢化玻璃表面轮廓微观不平度平均间距在冲蚀角度15°时达到最大,在冲蚀角度45°时达到最小;浮法玻璃在冲蚀角度15°时达到最大,在冲蚀角度45°时达到最小.     

香烟和蚊香超细微粒粒径谱特征

使用FMPS(Fast Mobility Particle Sizer)对香烟和蚊香燃烧产生的超细微粒数量粒径谱进行测量研究.结果发现,香烟烟雾ETS(Environmental Tobacco Smoke)和蚊香烟雾在10~500nm范围内呈对数正态单峰分布,香烟颗粒平均粒径(CMD)为118.7nm,蚊香颗粒CMD为80.3nm,两者数量粒径谱有类似的演变规律,但是总浓度衰减率有较大不同,香烟颗粒平均衰减率为0.066 1,蚊香颗粒平均衰减率为0.054 4.衰减率随着粒径的增大而减小,香烟颗粒各粒径段上颗粒的衰减率均大于蚊香颗粒.同时,在衰减的60min内香烟和蚊香颗粒CMD分别增大了近30%和25%.     

玻璃纤维/环氧树脂复合材料的粒子冲击磨损研究

本文研究了玻纤/环氧复合材料的粒子冲击磨损问题.结果表明:随粒子冲击速度的增加,材料的磨损率呈指数增加;随粒子冲击角度的增加,材料的磨损率先增加,在90°附近出现最大值,然后下降,在0°～180°内磨损曲线呈对称分布;磨损率还与材料中纤维取向有关,当纤维与磨面平行时,材料的耐磨性最低,当纤维与磨面垂直时,材料的耐磨性最高.      

压裂球座冲蚀磨损规律研究和结构优化

针对压裂球座锥段处冲蚀磨损严重将影响滑套的开启和压裂施工正常进行的问题,基于固液两相流和冲蚀理论,建立了压裂球座冲蚀模型,分析了球座冲蚀磨损原因。采用控制变量法,分析了压裂液排量、颗粒浓度、颗粒直径、黏度对球座冲蚀磨损的影响。通过分析可知:随着压裂液排量和颗粒浓度的增加,球座冲蚀速率增大;随着颗粒直径和黏度的增加,球座冲蚀速率减小。为减少球座冲蚀磨损,分析了不同锥角和结构形式的球座锥段冲蚀速率;得出锥角在20°~30°范围内最为合理,锥段为凹面结构和双角度结构的球座,其冲蚀速率都较小。分析结果对水平井投球滑套分段压裂技术的改进和现场压裂施工具有指导意义。     

滚动碰撞式调制质量阻尼器力学模型及参数分析

滚动碰撞式调制质量阻尼器(PTRMD)由调谐质量阻尼器及颗粒阻尼器发展而来,其在土木工程减振控制领域中的研究仍处于初步分析与探索阶段,阻尼器自身参数及外部激励条件对其减振性能的影响尚不明确。在考虑颗粒与主体结构碰撞和摩擦效应的基础上,建立PTRMD力学模型,并将颗粒和结构的振动过程划分为非碰撞过程、碰撞过程及黏滞振动过程;建立PTRMD-单自由度结构运动微分方程并分别对其进行求解;基于数值仿真分析方法,分别对碰撞间隙比、颗粒运动频率比、滚动摩擦因数、碰撞恢复系数、颗粒质量与简谐激励强度及频率等参数对PTRMD减振性能的影响进行研究。结果表明:颗粒运动频率比较小时,PTRMD减振效果随碰撞间隙比的增加而基本成线性增加,且受激励幅值的影响较小;当颗粒运动频率比较大时,其减振效果随碰撞间距比的增加先增大后减小,且受激励幅值影响较大。     

爆炸荷载作用下覆土库外部冲击波传播规律

为了研究爆炸荷载作用下覆土库外部冲击波的传播规律,采用有限元软件ANSYS/LS-DYNA,结合将覆土库结构破坏与冲击波传播先后模拟的新手段,对覆土库外部距爆心比例距离小于15 m/kg~(1/3)范围内空气冲击波的传播过程进行模拟,并对模拟所得不同测线方向(0°、60°、90°、135°和180°)冲击波峰值超压和冲击波到达时间进行分析。结果表明:测点距爆心比例距离在1～15 m/kg~(1/3)范围内,随比例距离的增大,在60°和90°测线方向,冲击波峰值超压衰减率从87.63%降到26.39%;在135°和180°测线方向,冲击波峰值超压衰减率从81.19%降到1.39%。随着测点距爆心比例距离的增大,冲击波峰值超压呈指数型衰减,冲击波到达时间呈线性增加。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

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.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

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...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The 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.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.