简支圆板在复杂荷载作用下的塑性极限荷载统一解析解

本文采用双剪统一屈服准则对受线性荷载和边缘弯矩联合作用下的简支圆板进行了塑性极限分析，考虑了联合作用的两种形式，分别给出了统一的解析解。得到了极限荷载随不同屈服准则的变化曲线。对于不同的材料，本文均能给出相应的极限荷载。已有的Tresca准则、Von Mises准则、双剪应力准则的解答是文中解答的特例或逼近。本文得到的一系列有规则变化的解析解，可以适用于各种拉压强度相同材料的简支圆板的塑性极限荷载求解。文中统一解大于Tresca单剪理论解，它可以更好地发挥材料的强度潜力，工程应用可以取得明显的经济效益。     

Rheological studies of coal-oil mixtures

Summary Samples of stable coal-oil mixtures were prepared with coal concentrations ranging from 30–50% by weight. Extensive rheological data were obtained using capillary and cone-plate viscometers for samples of coal-oil mixtures and fuel-oil which served as a reference fluid. Viscosity measurements show coal-oil mixtures to be shear-thinning suspensions, i.e., the viscosity decreases moderately with increasing shear rates. In the concentration range of 30–40% coal, the coal-oil mixture shows a predominantly Newtonian behavior. For mixtures with coal concentrations higher than 40%, a yield point was observed. The study of these samples with the rotating-rod viscometer indicated a migration of coal particles away from the rotating rod with no noticeable rod climbing, thus no evidence of normal stress effects. The rheological data can be represented by any of the three two-parameter models: Power Law, Bingham Plastic, or Casson, with the last two models being more realistic and consistent with the observations.With 9 figures     

半无限空间重力隧洞洞室临塑状态分析

利用Mindlin给出的、半无限空间重力隧洞初始应力场下的完整应力解分析了洞室周边的应力分布规律,用数值方法计算出了最大压应力的位置;结合Mohr-Coulomb屈服条件,研究了洞室周边出现塑性点时洞室直径、围岩粘聚力、内摩擦角与相对埋深的关系,以便工程设计应用。     

用双剪应力屈服准则求轴对称球扁壳的极限荷载

本文导出轴对称球面扁壳在双剪应力屈服下的极限条件，并求出周边固定简支情况下的极限载荷。     

An effective computational algorithm for rate-independent crystal plasticity based on a single crystal yield surface with an application to tube hydroforming

Up to now, several computational methods have been proposed for crystal plasticity models. The main objective of these computational methods has been to overcome the problem with the non-uniqueness of active slip systems during the plastic deformation of a single crystal. Crystal plasticity models based on a single crystal yield function have been proposed as alternative algorithms to overcome this problem. But the problem with these models is that they use a highly non-linear yield function for the crystal, which makes them computationally expensive. In this paper, a computational method is proposed that would modify a single crystal yield function in order to make it computationally efficient. Also to better capture experimental data, a new parameter is introduced into the single crystal yield function to make it more flexible. For verification, this crystal plasticity model was directly applied for the simulation of hydroforming of an extruded aluminum tube under complex strain paths. It was found that the current model is considerably faster than the previous crystal plasticity model based on a power-law type single crystal yield surface. Due to its computational efficiency, the current crystal plasticity model can also be used to calculate the anisotropy coefficients of phenomenological yield functions.     

汽车薄钢板应力应变曲线及屈服轨迹的研究

采用十字形双向拉伸的实验方法对两种汽车用薄钢板BH220和SPEN进行了不同 加载路径下的双向拉伸试验，得到了不同应力状态下的应力应变关系曲线，同时，根据单位 体积塑性功相等的原则，确定了两种钢板等效塑性应变从0.2\%$\sim$2\%的实验屈服轨迹. 结果分析表明：不同加载路径下板料的应力应变关系不同，随着加载比例由单拉到等双拉状 态，板料的硬化指数逐步增大；实验屈服轨迹呈外凸性，且以等双拉为界的上下部分屈服轨 迹不对称，随着变形程度的增加，屈服轨迹向外扩大，但单拉时强化程度最小，而等双拉 时最大. 对BH220和SPEN钢板的实验屈服轨迹与几种常用理论屈服轨迹的比较发现，Hosford各向 异性屈服准则的理论轨迹与实验结果最为接近，Hill48准则与实验结果相差最大，此外一 向被视为只适用于各向同性材料的Mises准则与实验结果也较为接近，其他几个屈服准则的 理论屈服轨迹与实验点相差较大.     

考虑拉压强度差效应的厚壁圆筒承载能力分析

应用双剪统一强度理论，考虑材料的拉压异性和同性，推导了在内压力和轴力联合作用下的厚壁圆筒的塑性极限载荷表达式．在该表达式中，当反映中间主应力效应的系数取不同的值时，就能得到按Tresca屈服准则、线性逼近的Mises屈服准则和双剪应力屈服准则的计算结果，并且绘制了在相应准则下的极限应力线图．从而可知：在三维应力状态下，应用该理论，可以获得极限载荷分析的精确解；极限载荷线图与三种屈服准则的屈服曲线是相吻合的；计算的结果可以用于拉压异性和同性的材料，为工程应用提供了理论依据．     

拉压异性线性等向强化材料厚壁球壳极限分析

运用Mohr屈服准则对承受内压的拉压屈服强度不同的线性等向强化材料的厚壁球壳进行了极限载荷分析，得到了依赖于拉压比和强化模量的厚壁球壳极限载荷解析式和依赖于拉压比和强化模量的厚壁球壳极限载荷分析式。结果表明，材料拉压屈服强度的不同和强化特性对厚壁球壳极限载荷均有一定的影响。     

SECOND-ORDER MOMENT MODEL FOR DENSE TWO-PHASE TURBULENT FLOW OF BINGHAM FLUID WITH PARTICLES

The USM-θmodel of Bingham fluid for dense two-phase turbulent flow was developed, which combines the second-order moment model for two-phase turbulence with the particle kinetic theory for the inter-particle collision. In this model, phases interaction and the extra term of Bingham fluid yield stress are taken into account. An algorithm for USM-θmodel in dense two-phase flow was proposed, in which the influence of particle volume fraction is accounted for. This model was used to simulate turbulent flow of Bingham fluid single-phase and dense liquid-particle two-phase in pipe. It is shown USM-θmodel has better prediction result than the five-equation model, in which the particle-particle collision is modeled by the particle kinetic theory, while the turbulence of both phase is simulated by the two-equation turbulence model. The USM-θmodel was then used to simulate the dense two-phase turbulent up flow of Bingham fluid with particles. With the increasing of the yield stress, the velocities of Bingham and particle decrease near the pipe centre. Comparing the two-phase flow of Bingham-particle with that of liquid-particle, it is found the source term of yield stress has significant effect on flow.     

聚集诱导发光现象的理论研究

本文系统介绍了本课题组发展的分子辐射跃迁和无辐射跃迁速率常数的热振动关联函数理论方法的最新进展及其在聚集诱导发光领域的典型应用. 基于第一性原理计算, 定量考察了位阻、温度、聚集等因素对分子体系发光性质的影响. 从微观角度给出了分子聚集诱导发光机理： 分子激发态的无辐射能量衰减通道主要是对应于低频模式的芳香环扭转和高频模式的碳碳伸缩振动. 当位阻增加、温度降低或者分子聚集时, 芳香环的转动受限, 无辐射能量衰减通道被抑制, 导致无辐射跃迁速率常数降低, 而其对辐射跃迁速率常数影响不大, 从而提高分子的荧光量子产率, 荧光增强.