压力载荷下非粘结柔性立管应变影响因素分析

基于Abaqus/Explicit准静态和质量放大方法研究了一类典型非粘结柔性立管在压力载荷作用下应变响应特性,对影响立管整体轴向延伸率和绕轴向扭转角度的因素进行了分析。数值模型计入金属层实际截面形状、铺设角度以及几何、接触、材料非线性。计算结果表明：数值解与理论值吻合较好;立管端部边界条件对轴向延伸率影响不大但对绕轴向扭转角度影响较大;抗压铠装层为径向压力主要受力构件,其铺设角度虽然对压溃性能不大,但在应变分析中不可忽略;拉伸铠装层铺设角度对应变影响同样较大。文中数值方法可弥补理论方法限定在小位移、小变形范围,无法计入层间摩擦、材料非线性及初始制造椭圆率等缺陷。     

河床粗化研究的回顾及展望

本文综述了已有河床粗化的研究成果,包括河床粗化类型;床面可动层;粗化层的形成机理、级配计算、稳定性判别及河床极限冲刷深度的计算等,并用水槽及天然资料对粗化层级配计算方法作了简要评述,指出了尚有待改进的地方及今后着重开展的工作。     

Experimental study on the interlayer friction and wear mechanism between armor wires of umbilicals

Friction and wear behavior between armor wire layers of umbilical plays an important role in its mechanical properties, in particular its fatigue life. The present paper addresses friction tests to investigate the interlayer sliding friction and wear mechanism of armor wires in an umbilical. A series of friction tests were carried out to study the evolution of coefficient of friction (COF) and wear between armor wire layers. The results show that the COF increases with increasing number of reciprocating sliding cycles in dry friction condition. A dual stable trend was found in the evolution process of interlayer friction and wear of armor wires. A friction model was proposed to describe this trend by dividing the evolution process into three stages: the initial stable stage, the transition stage, and the latter stable stage. The mechanism of the dual stable trend was revealed, which was mainly caused by wear process of nylon fiber tape, and effected by dry/wet wear condition and wear coefficient. The effect of the contact condition, sliding amplitude and number of nylon fiber tape on COF was studied. The COF of the latter stable stage increases with increasing sliding amplitude and number of layers of nylon fiber tape. The finding in this paper provides a valuable approach for a more accurate fatigue life prediction of an umbilical.     

复合抗弹结构设计及隔热性能验证

超高分子量聚乙烯纤维增强塑料(UFRP)层合板具有良好的抗侵彻性能,但受温度影响明显,其热损伤的临界温度仅为147℃.为了避免火灾产生的高温使UFRP层合板失去抗弹性能,设计了以船用钢为前/后面板,SiO2气凝胶毡为隔热层,UFRP层合板为抗弹层的复合抗弹结构.在A60耐火等级标准条件下,对复合抗弹结构的有限元模型进行瞬态热分析,探索了复合抗弹结构内部的温度分布与SiO2气凝胶毡隔温层厚度的关系.根据有限元仿真结果,近一步对SiO2气凝胶毡隔热层厚度为20 mm的复合抗弹结构单元开展耐火试验.结果表明:SiO2气凝胶毡具有良好的隔热性能,在A60耐火等级标准条件下,保持复合抗弹结构中UFRP层合板抗弹性能完好所需的SiO2气凝胶毡隔热层厚度至少为20 mm.     

波浪作用下灌砌块石海堤的护面稳定性

通过物理模型试验,对一种新型的海堤护面结构形式——灌砌块石护面的稳定性进行研究,总结了波浪作用下灌砌块石护面失稳破坏的发展过程。研究结果表明:灌砌块石稳定性随破波参数的增大而减小、随开孔率的增大而增大,同时镇压层的设置有利于提高灌砌块石的稳定性。结合前人关于砌石护面稳定性的研究成果,给出了不同开孔率下灌砌块石护面稳定厚度计算公式。     

宽级配河床粗化稳定结构

本文阐述了宽级配河床粗化稳定结构的特性,得到了宽级配河床粗化稳定后的阻力规律、非均质沙起动概率及粗化层级配的计算方法,并利用各家水槽资料、San Luis河流(美国)及汉江丹江口水库下游资料与阻力公式及粗化层级配计算值进行了比较,二者基本吻合。     

基于FEMDEM的斜坡堤护面块体破坏的数值模拟

针对斜坡堤人工护面块体发生的接触碰撞问题,应用有限元离散元耦合法（FEMDEM）探讨了护面块体的碰撞 应力、裂缝形成以及断裂过程。算例结果表明：断裂破坏通常发生在边界转角及角点,FEMDEM能有效地模拟连续介质向 非连续介质的转化过程。     

A finite element model for flexible pipe armor wire instability

The constructive disposition of metallic and plastic layers confers flexible pipes with high and low axial stiffness respectively when tensile and compressive loads are applied. Under certain conditions typically found during deepwater installation or operation, flexible pipes may be subjected to high axial compression, sometimes accompanied by bending. If not properly designed, the structure may not be able to withstand this loading and fails. From practical experience observed offshore and in laboratory tests two principal mechanisms, which will be discussed in this paper, have been identified regarding the configuration of the armor wires. When the pipe fails by compression the armor wires may exhibit localized lateral or radial deflections, consequently permanent damage is observed in the armor wires with a sudden reduction of the structure’s axial stiffness. The pressure armor may also unlock, thus causing potential fluid leakage.In this work a finite element model is developed to estimate the critical instability load and failure modes. An axi-symmetric model is constructed employing a complex combination of beam and spring elements. For each armor layer only one wire needs to be modeled, hence the computational cost is minimized without compromising the phenomenon characterization. A parametric case study is performed for a typical flexible pipe structure, where the friction coefficient between the wire armors and the external pressure are varied, and the critical instability loads and failure modes are obtained and results are discussed.     

基于HLA的层次联邦在装甲部队仿真模型体系中的应用

基于仿真体系复杂度的提高，运用运筹学和现代作战建模方法，提出多联邦仿真系统中层次联邦实现的两种方法，研究了使用桥接成员实现层次联邦互连的思想，并对装甲部队相关的主要模型进行描述的基础上对装甲部队仿真模型体系进行了构建，对该模型的建立，将为我军装甲部队仿真模型体系的建设发挥指导作用。     

非粘合柔性管破段强度解析分析（英文）

This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA model and a number of test data, and showed reasonably good agreement. The theoretical analysis showed that the pressure armor layer enhanced the strength of the carcass against buckling, though the barrier weakened this effect. The collapse strength of pipe was influenced by many factors such as the inner radius of the pipe, the thickness of the layers and the mechanical properties of the materials. For example, an increase in the thickness of the barrier will increase contact pressure and in turn reduce the critical pressure.     

人工块体替代垫层块石的数值试验研究

针对大垫层块石选料困难和抛填理坡施工难度大、较难控制施工质量及进度的问题,通过水工物理模型试验及数值模拟的手段,对人工块体替代垫层块石可行性进行了初步探究。基于水工试验结论,利用CAD与CFD相结合的方式,建立了符合真实海况的三维防波堤水动力数学模型,并通过波面方程和物理模型试验对其有效性进行了验证。数值试验给出了不同垫层形式对波浪爬高的影响,探讨了护面块体的受力和块体间隙的流场分布。结果表明人工块体作垫层有一定可行性。为进一步探究护面层失稳的动力特征提供了依据,对工程设计中人工块体代替垫层块石的可行性提供参考。     

基于云重心理论的装甲师火力联合能力评估

装甲师火力联合能力是一个复杂的多指标综合体系,通过建立装甲师火力联合能力评估模型,确定评估指标,运用云重心理论对其进行探索。在对云重心理论介绍的同时详细地给出了其实现步骤,最后用加权偏离度（θ）来衡量火力联合能力与理想状态的偏离程度,以确定装甲师火力联合能力的优良,并结合算例验证此方法的实用性和有效性,增强模型的可信度和可操作性。对装甲师火力联合能力的评估提供了有效的方法和途径。     

联锁块铺面的有限元模型分析

通过建立联锁块铺面的平面应变、轴对称和三维实体有限元模型,分析了联锁块块间接缝参数对基层层底弯拉应力和土基顶面压应变的影响;提出了基于不同等效损伤原则的联锁块层等效模量的概念;比较了接缝与联锁块块间连续时不同有限元模型计算得到的联锁块层等效模量的差异;建立了等效模量与接缝参数的关系式;考虑了接缝与联锁块块间可脱开时联锁块层等效模量的变化,并给出了等效模量的推荐表。     

斜坡式护岸护面块体优化设计

结合物理模型试验,对某工程区域的斜坡式护岸护面块体的结构形式进行优化设计,并对护面块体的稳定性进行分析研究.优化方案实施后,使用安全,并获得良好的经济效益和社会效益.     

破片模拟弹侵彻陶瓷/船用钢复合靶板的理论分析模型研究

简要回顾了陶瓷/金属复合靶板的研究现状.根据船用钢的吸能特点和船用陶瓷轻型复合装甲的特殊性,将10 g破片模拟弹侵彻陶瓷/船用钢的过程分为两个阶段,分别计算了破片模拟弹的侵蚀变形能和船用钢背板的隆起-碟型变形吸能,并将后者分为径向弯曲变形能、径向膜托伸变形能及周向弯曲变形能等,给出了各种能量的计算公式,建立了计算弹道极...     

不同开孔率混凝土护面板上波浪打击力试验研究

波浪荷载是斜坡堤上混凝土护面板防浪特性的主要研究内容之一。通过物理模型试验,采用不规则波浪作用,对透水斜坡上不同开孔率混凝土面板受到的波浪打击力进行研究,分析了打击力1%值和1/3值随各影响因素的变化特性,提出了包含开孔率影响的单坡上波浪最大打击力计算方法,给出了波浪打击力的统计分布规律。     

美国气垫登陆艇装甲防护技术发展及其对总体性能的影响

美国气垫登陆艇(LCAC)的艇体浮箱及上层建筑均为焊接铝结构,板厚较薄,防弹能力较差,LCAC对驾驶舱等重要部位采用额外装甲进行防护。随着轻质装甲材料的发展,其单位面积质量大为减轻,LCAC将装甲防护范围进一步扩大,以增强中弹后的返航能力。文章系统介绍LCAC装甲防护技术的发展,并就装甲防护对总体性能的影响进行分析,也可为国内气垫船的技术发展提供借鉴。     

An investigation on flexible pipes birdcaging triggering

An investigation on triggering mechanisms for the birdcaging failure mode of flexible pipes, used in offshore oil and gas production, is carried out. From previous experimental observations, a conjecture is made: the local axisymmetric instability of the external plastic layer, caused by the high radial loading which is internally applied due to the helical armor wires tendency to expand when the pipe is subjected to compression, would be this trigger. A simple instability onset criterion for the external plastic layer, namely, the polymer intrinsic yielding limit stress, is proposed and assessed, analytically, numerically and experimentally for HDPE tubes. Then, previous birdcaging experimental observations are investigated further, focusing on the flexible pipe external plastic layer, to assess the proposed criterion. Strong evidences of validity are obtained.     

Application of analytical model in the prediction of dynamic responses and fatigue damage of flexible risers: Part I – Improvement of analytical model considering shear deformation and varying tension effects

Flexible risers have been widely utilized for the transfer of oil and gas products from a well to production units. The components of flexible risers, unlike steel risers, experience complex contact phenomena during bending. The contact between helical wires and adjacent layers especially causes a significant level of bending nonlinearity, making it hard to estimate the structural responses. Accordingly, a large-scale dynamic analysis of flexible risers usually involves an analytical model that predicts the bending moment and axial stress of helical wires based on theoretical approaches. The analytical model consists of an axis-symmetrical model and a bending model. Among them, the bending model plays a critical role in the prediction of the bending responses of flexible risers. The conventional bending models usually neglect the shear deformation of internal layers and continuity of sliding force, which leads to a significant error of analysis. Furthermore, the previous bending models assume that the contact pressure on helical wires is constant during bending. In real operating conditions, however, most flexible risers experience a considerable change of tension that governs the slip of helical wires. Hence, the current study presents a new dynamic analysis method for flexible risers. The suggested analytical model improves the bending model based on an accurate estimation of the internal strain field considering the shear deformation and continuous sliding force. Also, this study proposes a stiffness update method to reflect the effect of varying tension in the dynamic analysis. The presented method updates the bending property of flexible risers considering the continuous change of the contact pressure from varying tension. For the validation of suggested method, the current study carries out numerical simulations with a pure bending and varying tension for the internal diameter 7 inches flexible risers. It is identified that the suggested analytical model provides accurate analysis results. Moreover, it is found that the effect of varying tension gives a significant impact on the bending behavior of flexible risers by changing the slip condition of helical wires. Part I of this series of papers describes the detailed formulation method for the analytical model and with some verification examples. The suggested analytical model is expanded to the large-scale dynamic analysis in Part II for the investigation of the effect of shear deformation and varying tension.     

斜坡堤护面块体的安全度分析

斜坡堤护面块体的稳定重力通常按赫德森公式计算,但其安全水平并不明确。提出护面块体安全度的概念,推导出其数值为KN=2.2,两组断面模型试验的结果验证了这个数值是合适的。利用护面块体的安全度,可以客观确定护面块体的稳定重力、新型护面块体的稳定系数,还可用来校验现有各种护面块体稳定系数的合理性。