基于相互积分的应力强度因子数值分析

应力强度因子可反映裂纹尖端弹性应力场的强弱,是解决结构疲劳断裂问题的重要参数。工程上常采用有限元分析软件对各种复杂裂纹体进行数值模拟进而求解断裂问题。有限元分析软件ANSYS提供后处理功能可直接计算各种断裂参数。借助ANASYS计算平台,分别采用传统的位移插值法和基于相互积分的数值方法可求得张开型二维及三维裂纹应力强度因子。将数值分析结果与二维裂纹的解析解和三维裂纹扩展实验的测量结果进行对比分析后发现,基于相互积分理论求得的应力强度因子更为精确,这种优势在三维裂纹数值分析中更为显著。     

CM三维复合地基研究现状及分析

 在前人复合地基研究的基础上，进一步明确了复合地基的基本概念、分类及其基本特点，并提出了CM三维复合地基的原理、形式以及工作机理，用柔性短桩处理浅层软弱土、刚性长桩控制沉降、褥垫层调整和改善桩土应力分担比。给出了CM三维复合地基承载力和沉降的设计计算思路。     

桩基础桥梁的土—结构动力相互作用

首先以加权残差公式为基础，采用积分方程方法推导与桩基础对应的层状场地动力刚度矩阿公式，并用解析解验证了数值分析的计算结果。然后用子结构法联合积分方程方法和有限元法的计算结果，求解土-结构动力相互作用的地震响应；最后以芜湖长江大桥主跨斜拉桥长塔墩的地震响应为例，将本文的计算结果与Penzien模型的计算结果作了比较。     

Convection and the seeding of the North Atlantic bloom

Observations of vertical velocities in deep wintertime mixed layers using neutrally buoyant floats show that the convectively driven vertical velocities, roughly 1000 m per day, greatly exceed the sinking velocities of phytoplankton, 10 m or less per day. These velocities mix plankton effectively and uniformly across the convective layer and are therefore capable of returning those that have sunk to depth back into the euphotic zone. This mechanism cycles cells through the surface layer during the winter and provides a seed population for the spring bloom. A simple model of this mechanism applied to immortal phytoplankton in the subpolar Labrador Sea predicts that the seed population in early spring will be a few percent of the fall concentration if the plankton sink more slowly than the mean rate at which the surface well-mixed layer grows over the winter. Plankton that sink faster than this will mostly sink into the abyss with only a minute fraction remaining by spring. The shallower mixed layers of mid-latitudes are predicted to be much less effective at maintaining a seed population over the winter, limiting the ability of rapidly sinking cells to survive the winter.     

土层液化过程中桩土相互作用的动力p-y曲线研究

依据加权余量法原理,推导了确定桩与液化土层相互作用振动台模型试验动力p-y曲线的方法。分析了具有不同初始相对密度的土层在液化过程中动力p-y曲线的弱化以及桩土相互作用阻尼的变化,对动力p-y曲线和拟静力弱化p-y曲线进行了比较。结果表明,依据静力p-y曲线、按折减系数法确定拟静力弱化p-y曲线时,折减系数的取值不仅取决于土层初始相对密度,还与土层的埋深有关。     

大跨度铁路桥梁刚度统一描述方法探讨

研究目的:本文在已建成的桥梁基础上,进一步开展了大跨度铁路桥梁刚度描述方法和预应力混凝土连续梁(刚构)桥刚度的限值研究,以提出一种大跨度铁路桥梁刚度问题的统一描述方法。研究结论:采用设计荷载下的梁端横向、竖向、扭转角及非梁端处横向、竖向、扭转角的变化率(即曲率)描述桥梁刚度,推导了大跨度铁路预应力混凝土连续梁(刚构)桥刚度设计参考限值。该方法不但能方便地描述简支梁的刚度问题,与现有规范相衔接,而且在描述规范所不能涵盖的大跨度桥梁、特殊桥梁结构刚度问题时也非常方便。研究方法和研究成果有利于提高桥梁刚度研究和设计水平,为发展更大跨度桥梁提供技术支撑。     

粤北山区高速公路煤系地层滑坡机理分析

以京珠高速粤境北段k18 170～k18 225滑坡为例,研究了煤系地层滑坡机理,通过对滑动带土的矿物组成及其物理力学性质分析,发现该类边坡滑坡的主要原因是煤系地层中的泥炭土含有一定比例的亲水矿物,在水的作用下力学性质发生大幅度降低.有限差分法分析结果表明:在边坡滑动带的泥炭层存在剪应力集中区,与滑动带的地质和物理力学滑坡分析结果相吻合.     

Research on interactive steering control strategy between driver and AFS in different game equilibrium strategies and information patterns

In the past decade, several publications have shown that it is advisable to design an advanced driver assistance system using a shared control structure. This paper is concerned with the modelling and verification of an interactive steering control strategy between a driver and an active front steering (AFS) controller to investigate the complex interactions between human driver and an AFS system. Using game theory as a general framework, a more comprehensive mathematical model system of interactive steering control potentially applicable to explore human drivers’ behaviours in shared control of intelligent vehicles is presented and discussed in this paper. The effects of different information patterns, namely the open-loop pattern and the closed-loop feedback pattern on modelling shared steering control between driver and AFS have been investigated. Simulation and hardware-in-loop implementation results prove the validity of steering interactive modelling in different game information patterns. Specifically, the results show that, in the Nash equilibrium strategy situation, the driver and the AFS controller may become more rational and reasonable in the process of completing the same dynamic task in the closed-loop feedback information patterns compared to the open-loop ones; and the differences between feedback Nash and feedback Stackelberg may depend on the step size of discretisation.     

绝对空间中的铁道车辆非线性动力学仿真

从铁道车辆三维可视化建模和仿真要求出发,基于面向对象软件技术,本文叙述了绝对空间中铁道车辆非线性动力学仿真的有关力学原理和计算结构,特别是Hertz理论在空间轮轨弹性碰撞中的完整应用。并用编制的仿真软件VSDS对ManchesterBenchmarks的客车模型进行了曲线通过工况仿真,指出绝对空间中铁道车辆非线性动力学仿真的可行性和实用性。     

Mathematical model of single-propeller twin-rudder ship

A mathematical model of a single-propeller twin-rudder ship has been developed from captive and free running model experiments. An open water rudder experiment was carried out to figure out the characteristics of the rudder. Captive experiments in a towing tank were carried out to figure out the performance of a single-propeller twin-rudder system on a large vessel. Interactions between the hull, propeller and twin rudders, including mutual interactions between the twin rudders, were expressed with several coefficients that were calculated from the experimental results at various ship speeds. In the analysis, the unique characteristics of a single-propeller twin-rudder ship, which affects rudder forces, were explained and formulated in the mathematical model. The captive model tests were conducted with zero ship’s yaw rate, so the interaction coefficients, which are influenced by the yaw rate, are determined from free running model experiments. Validation of the mathematical model of a single-propeller twin-rudder system for a blunt body ship is carried out with an independent set of free running experiments, which were not used for determining the interaction coefficients. The validated numerical model is used for carrying out simulations. Based on simulation results, some recommendations have been proposed for installing a single-propeller twin-rudder system.