降雨作用下裂隙红黏土边坡渗流特征与冲刷模式

针对降雨作用下裂隙红黏土边坡失稳破坏问题，开展红黏土边坡裂隙演化、降雨入渗及冲刷模型试验，提出基于图像摄影识别技术的边坡裂隙特征及含水率分布定量表征方法，揭示红黏土边坡裂隙演化规律，分析裂隙发育程度与降雨强度对红黏土边坡渗流特征与冲刷模式的影响。结果表明：干燥作用下红黏土边坡表面裂隙发育，其中坡面裂隙发育最强烈，其最大裂隙平均宽度为4.1 mm，最大裂隙深度为7.7 cm，最大裂隙率为10.4%，但坡底子裂隙和分支裂隙发育最充分，且主裂隙最先出现于远离坡面处；降雨作用下，雨水极易沿坡表裂隙形成优势流迅速渗入边坡内部，使边坡含水率增加且呈不均匀分布，出现局部暂态饱和区；裂隙发育程度和降雨强度的增强均会提高前期降雨入渗速率，并增加最终降雨入渗深度，其中坡底处入渗深度最大；极端降雨对裂隙红黏土边坡冲刷作用明显，造成坡面松散层流失，坡底显现冲刷痕迹，坡脚局部发生滑动。基于图像摄影识别技术定量分析边坡含水率分布的方法简单有效，研究成果可为裂隙性红黏土边坡灾害防治提供参考。     

船舶加筋板结构耐撞性能分析

提出计及摩擦力影响后船舶舷侧加筋板耐撞性能分析的一种简化分析方法,详细讨论了球鼻艏撞击作用下舷侧加筋板的渐进破坏过程,给出了相应的撞击力-撞深曲线和吸收能量-撞深曲线。通过与已有试验结果的比较表明,该简化分析方法能对船舶舷侧加筋板结构的耐撞性能做出合理预报,从而可用于设计阶段评估船体舷侧结构的耐撞性能。     

船舶板梁组合结构的振动分析

采用Ｍｉｎｄｌｉｎ板单元和参考轴杆单元,建立了考虑板剪切变形、骨架剪切变形和骨架偏心影响的船舶板梁组合结构振动分析模型,并研究比较了不同船舶板梁组合结构振动分析有限元模型的计算精度。最后通过对某舱室甲板固有频率计算值和实测值的比较,讨论了船舶局部结构振动分析中边界条件处理问题。     

质子交换膜燃料电池双极板材料及制备综述

质子交换膜燃料电池(PEMFC)的发展显示出了它成为清洁、高效和可靠电源的潜力。双极板(BP)作为PEMFC的关键部件之一,具有提供电气连接、输送反应气体、消散反应热、去除副产物的作用,但也是制约PEMFC成本的主要因素之一。根据双极板材料的不同可以分为金属双极板、石墨双极板和复合材料双极板,本文综述了双极板材料(金属、无孔石墨和复合材料)及其制备工艺。其中,金属双极板因其优异的机械和物理性能,与无孔石墨及复合材料相比具有较强的成本优势,在乘用车应用中备受关注,但其制造工艺和耐腐蚀性是金属双极板的主要关注点。未来,开发出优良的耐蚀性和导电性涂层或新型的双极板金属材料将极大地促进PEMFC在乘用车领域的应用。     

An approximate method to generate average stress–strain curve with the effect of residual stresses for rectangular plates under uniaxial compression in ship structures

The average stress–strain curve for rectangular plates under uniaxial compression in ship hull structures is generated on the basis of the existing design formulae. The dual-term equation for ultimate strength of uniaxially compressed plates is employed to generate the average stress–strain curve for long plates. Two alternatives proposed by Faulkner and Frankland, respectively, are considered. An approximate method to take into account the effect of residual stresses is proposed. By investigating the variation of the stress distribution at different stages of compression, the average stress–strain relationship of the rectangular long plates with the effect of residual stresses is derived from equilibrium. The behaviors of the wide plates are also discussed. The assumption proposed by Valsgard for the idealized stress distribution of wide plates under uniaxial compression is adopted. The average stress–strain relationship for wide plates is derived from the existing design formulae. Two equations proposed by Hughes and recommended by API for critical stress of the central portion of the wide plate are considered. The effect of residual stresses is also taken into account for wide plates.     

框架顶底板结构对比计算分析

城市下穿隧道闭口段常采用单箱多室框架结构形式。框架结构大多采用平面杆系计算方式进行结构模拟分析。由于平面杆系计算方法的局限性,特别是中墙、边墙忽略厚度对框架顶、底板的内力削峰的影响,设计中对框架顶、底板在竖墙处计算结果取值偏大,框架顶、底板在竖墙处配筋量大幅度增加,造成工程材料的浪费及工程投资的增加。现采用不同的计算方法对构件计算结果合理性和适用性作分析判断,对类似结构构件的计算取值合理性提供借鉴和参考。     

Dynamic plastic response of clamped stiffened plates with large deflection

Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method （FEM） and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.     

Spar平台垂荡板受迫振荡水动力特性研究

首先针对圆形实板以及不同透空率下垂荡板作受迫正弦振荡的水动力特性进行了数值模拟研究,得到垂荡板作正弦振荡的阻力和附加质量系数,进而分析得出透空率对垂荡板阻尼及附加质量的影响规律;其次比较了相同透空率情况下不同小孔数目对垂荡板水动力特性的影响,并比较了不同形状垂荡板的水动力特性;最后还对双板之间的间距进行了优化计算.在此基础上综合考虑垂荡板受迫振荡水动力特性,为深水Spar平台的垂荡板优化设计提供技术指导,使其能够有效地改善Spar平台的垂荡运动性能.     

基于NURBS的船体曲面切割和排板技术的探讨

船体曲线和曲面的分割与曲面排板是船舶计算机辅助设计与制造中的一项关键技术。本文使用一种新的算法实现了船体NURBS曲面的切割以及外板曲面的生成,并对某集装箱船的船体曲面和船体某外板曲面进行了计算,验证了该算法的正确性和可行性。     

有限长双层壳体声辐射理论及数值分析

研究流场中有限长加筋双层圆柱壳受径向点激励的振动和声辐射性能。壳体的振动用Fluegge壳体方程描述，将加强构件等价为对内外壳体的支持力，采用Helmholtz波动方程、壳体表面的边界条件和傅氏变换方法求解声压的表达式，然后将其引入壳体振动方程，最后求解双层壳体声-流体-结构耦合方程，计算结果用辐射声功率、表面振动均方速度级和辐射效率的形式表示。讨论了有限长单、双层壳体声辐射性能的差别以及双层壳体壳间连接形式和实肋板参数的变化对其声辐射性能的影响，得出结论：当内壳受激振动，通过外壳向外场辐射噪声时，其主要通道为连接内外壳壳体的实肋板，其次才是环形流场中的流体介质。