拉拔试验研究的现状与发展

加筋土界面的摩擦特性是现代加筋土技术研究的热点和难点,是彻底弄清加筋机理和建立加筋土理论体系的关键。许多学者做了大量的试验和理论研究工作,取得了一些成果,但由于影响筋土界面摩擦特性的因素多,情况复杂,加之目前由于实验设备及方法的限制,有许多问题还未能彻底搞清楚。本文介绍了目前国内外在此问题上的一些研究成果,着重分析了试验的影响因素、存在的问题及今后发展方向。     

Numerical Investigation on Two-dimensional Boundary Layer Flow with Transition

As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics （CFD）. A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation （RANS） in this paper. Turbulence model plays a significant role in the complex flows＇ simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox （2006） k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition＇s behavior.     

船用海水泵机械轴封漏水故障分析及排除

考虑到船用海水泵机械轴封漏水是该设备常见故障,从实践经验出发,分析船用海水泵机械轴封漏水原因,提出解决故障的方法和改进措施。     

复合搅拌摩擦点焊旋转半径对接头组织和性能的影响

对2 mm 2A12-T4铝合金薄板采用复合搅拌摩擦点焊进行焊接,测试不同旋转半径下的复合搅拌摩擦点焊接头的抗剪力,并观察和分析复合搅拌摩擦点焊接头在拉伸时的断裂途径及微观组织.结果表明:当其他参数不变时,复合搅拌摩擦点焊接头抗剪力和断裂途径随旋转半径和塑性环形貌的不同而变化;在旋转半径为1.2mm时,接头的抗剪力达到...     

船用铝合金角接的固定轴肩搅拌摩擦焊焊具设计研究

针对船舶常用的5系与6系铝合金的角接开展目定轴肩搅拌摩擦焊的焊具设计研究,对焊具材料的选择及热处理工艺、轴肩和搅拌针的结构型式以及两者间的配合方式等展开了分析研究.     

摩擦板支撑型高桩梁板码头设计

桩基结构设计是高桩码头设计的重点,常规高桩码头水平荷载完全由桩基本身承担,从而导致码头桩基数量多、尺度大、工程造价高.针对水平荷载导致码头桩基结构增加的难题,通过在码头后方设置摩擦板支撑系统,承担水平荷载,并利用有限元计算方法与传统高桩码头进行对比计算,揭示摩擦板支撑系统的作用机理和作用效果.结果表明,摩擦板支撑系统可...     

Flow resistance characteristics of water in narrow annulus during heat exchange

Considering the special resistance characteristics of fluids flowing through ducts with small gaps, experiments are per-formed to investigate the resistance characteristics of single-phase water, which is forced to flow through vertical annuli. The gap sizes are 0.9, 1,4 and 2.4ram, respectively. The experiments are conducted under condition of 1 atm. The water in the annuli is heated by high temperature water reversely flowing through the inner tube and the outer annulus. The results show that the flow pattern begin to change from laminar to turbulent before Reynolds number approaches 2000, the flow resistance in annulus has llttie relations with the temperature difference and ways of being heated, but mainly depends on the ratio of mass flux to the width of annulus.     

轮轨相互作用有限元分析

本文在Ｋａｔｏｎａ工作的基础上，发展了一种新的接触摩擦单元。这种单元能够模拟具有初始裂缝或无初始裂缝两物体间的摩擦滑动、张开和闭合过程。运用虚位移原理和结合考虑接触面上的约束条件，建立了接触摩擦问题增量形式的有限元刚度矩阵和荷载向量。在程序设计中，这种新单元可用标准的有限元集成规则组装到有限元程序中，作为实际应用的例子，文章了轮轨相互作用问题，并与不考虑接触摩擦影响的有限元分析是有效的，具有算法简