汽车炸弹爆炸冲击波作用下建筑物的动力响应分析

利用动力分析有限元程序LS-DYNA3D,对三层框架结构建筑物在汽车炸弹爆炸荷载作用下的动力响应进行数值模拟.将建筑物在空气冲击波作用下和空气冲击波与地震波共同作用的动力响应作了比较,得出不同位置处质点压力和等效应力等参数,分析了爆炸冲击作用下建筑物的破坏效应,为建筑结构的防护设计提供依据.     

制导炸弹水平侵彻爆炸作用下混凝土重力坝毁伤效应数值仿真

在综合考虑射弹的冲击侵彻作用、破碎弹壳爆炸能损耗、侵彻孔洞对爆轰产物的影响等因素的基础上,通过对制导炸弹GBU-28水平侵彻混凝土重力坝爆炸全过程的三维数值仿真,研究了混凝土重力坝在射弹侵彻爆炸下的动态响应及破坏效应.计算结果表明:侵彻爆炸的毁伤效应主要表现为坝体的局部破坏效应,而且呈现以爆炸作用为主侵彻作用为辅的破坏特征.细长弹药的侵彻爆炸破坏范围的增长主要体现在垂直弹轴方向.     

汽车炸弹钢箱梁内部爆炸局部破坏效应分析

采用ALE多物质流固耦合算法,对汽车炸弹 (TNT当量200kg~1500kg) 在双层桥梁下层桥面典型位置爆炸的局部破坏效应进行了数值模拟,研究了内爆炸冲击作用下钢箱梁的响应过程、破坏模式、破坏参数及其主要影响因素。结果表明：破坏模式及破坏参数与爆炸位置和TNT当量密切相关,爆炸位置对桥梁主要受力体系的受损程度影响较为明显,加劲肋对其垂直方向的破口具有约束作用,箱体对冲击波的约束效应使破坏作用加剧。合理设置加劲肋、加强重要构件和设置防爆层等措施有利于提高桥梁结构抗爆能力。     

水下爆炸载荷作用下细长体圆柱壳结构鞭状响应

采用2阶DAA流固解耦技术,对水下爆炸载荷作用下细长体圆柱壳结构的鞭状响应进行分析研究。经模型试验验证后,对细长体圆柱壳梁模型随不同药包爆炸方位、不同爆距及不同低频振动频率耦合程度变化时的鞭状响应进行计算,揭示圆柱壳梁模型在水下爆炸载荷作用下的总体低频运动特性及鞭状响应规律,为研究细长体圆柱壳结构在水下爆炸载荷作用下的鞭状效应总体损伤提供试验基础及理论方法。     

外接触爆炸荷载作用下大口径钢管变形与破坏效应的数值模拟

摘 要：基于动力有限元程序LS-DYNA及Lagrangian-Eulerian耦合方法,对大口径钢管在凝聚态炸药外接触爆炸载荷作用下的非线性动态响应过程进行数值模拟,描述了管道的变形情况、破坏过程以及管道内部应力的发展过程,分析了炸药质量、管道壁厚等因素对钢管破坏效应的影响。并在相同的条件下进行了实验研究,计算结果与实验数据具有较好的一致性。研究表明,小质量炸药爆炸后在装药与钢管接触处产生凹坑、鼓包及层裂等破坏效应;而较大质量炸药爆炸后在其爆破部位发生剪切破坏产生类似弹丸的破片,破片具有较大的动能,能够击穿另一侧管壁。研究结果可应用于管道结构在接触爆炸作用下的毁伤或防护方面的预测,从而为管道的安全防护设计提供理论依据。     

基于效应靶法评价爆炸冲击波毁伤的数值仿真

为反映爆炸冲击波对目标结构破坏程度的总体毁伤评价,建立了基于效应靶评价爆炸冲击波毁伤的方法.应用有限元动力学分析软件ANSYS/LS-DYNA,对效应靶在爆炸冲击波下的变形响应进行数值模拟研究,得到了挠度分别与炸距及TNT当量的函数关系,结合冲击波能量谱发现了自振频率对效应靶毁伤的影响,研究成果为战斗部爆炸冲击波的毁伤评价提供了依据和参考.     

双线隧道中单侧隧道内爆炸引起地面建筑的动力响应及滑移隔震研究

该文针对双线地铁隧道中单侧隧道内爆炸引起的附近地面建筑物的动力响应及滑移隔震效应进行了数值模拟研究。采用八结点等参元和集中质量体系来分别模拟包含隧道的有限土区和地面多层建筑,并将其耦合形成整个相互作用体系模型。在基底摩擦力计算中提出修正连续摩擦力模型,以克服传统Coulomb摩擦力模型的内在缺陷。通过与单线隧道内爆炸引起建筑物响应及滑移隔震效应的算例对比分析,揭示出地表建筑物在遭受地下单侧隧道内爆炸产生的经相邻隧道反射及衍射后的冲击波作用所引起的动力响应特征及其基底滑移隔震效果,从而为相关的理论研究和工程实践提供重要的数据参考。     

爆炸荷载作用下钢筋混凝土梁破坏形态有限元分析

在持续时间较长的爆炸荷载作用下,钢筋混凝土框架或梁通常会发生常见的弯曲破坏形态,但是在持续时间较短的爆炸荷载,如化学爆炸产生的脉冲荷载作用下,钢筋混凝土结构有可能在弯曲破坏发生之前产生剪切破坏。这种现象已被室内外试验所证实,其原因是脉冲荷载激发了结构中的剪力,从而使结构产生剪切破坏。为了预报钢筋单纯凝土梁在爆炸荷载下的响应破坏形态,本文提出了一种基于Ｔｉｍｏｓｈｅｎｋｏ梁理论的非线性分层梁有限元法。在材料模型中考虑了混凝土和钢盘的右面线性和应变速率效应等因素。应用这方法,本文计算分析了爆炸荷载作用下钢筋混凝土梁的动态响应以及弯曲、弯剪和剪切等不同的破坏形态,计算预报的结构动态响应和破坏形态与现场试验结果有较好的一致性。     

含铝炸药在混凝土介质中爆炸响应的FE-SPH算法模拟研究

本文采用自编程实现的二维轴对称FE-SPH耦合算法对含铝炸药在混凝土介质中的爆炸响应过程进行模拟研究。含铝炸药的爆炸过程采用JWL方程结合Miller反应率方程来描述,同时采用粒子接触算法避免爆炸响应后转化的SPH粒子点间形成堆积及非物理穿透。对不同含铝量的高能炸药在不同埋深下爆炸响应过程进行模拟,通过对混凝土的毁伤及预设动能杆的运动分析,结果表明,所实现的FE-SPH耦合算法能够稳定再现含铝炸药爆炸对混凝土介质的破坏响应过程,并且响应的特征参量也与实验数据吻合。     

水下和空中爆炸时混凝土重力坝动态响应对比分析

由于水和空气的物理属性差异以及与爆炸产物的界面作用效应不同,使得水下和空中爆炸冲击波传播特性及其荷载作用下的大坝结构动态响应存在较大的差异。通过构建混凝土重力坝水下爆炸和空中爆炸的全耦合数值仿真模型,考虑炸药起爆、冲击波传播、冲击波与结构的相互作用以及结构的动态响应等复杂过程,在对比分析爆炸冲击波在水下和空中传播特性的基础上研究了水下和空中爆炸冲击波对大坝动态响应及损伤程度的影响。研究表明,水下爆炸冲击荷载作用下混凝土重力坝动态响应及损伤程度均较同等炸药量下空中爆炸冲击荷载作用时大;在研究水工大坝抗爆性能时,应重点关注水下爆炸冲击波传播的特性及大坝在水下爆炸荷载作用下的动态响应。     

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.