A MODEL FOR PREDICTING THE RELIABILITY OF A MAN–MACHINE SYSTEM

A continuous-time Markov chain model, which considers the concept of human errors and recovery factors, is proposed for analysing the reliability of a man–machine system. This model can be applied to industrial systems such as the nuclear power plant, the NC machine cell, and the chemical plant. In order to show the application of the model and to validate its result, a computer animation program was written to simulate the control operation of a system. Some simulation experiments were conducted and the data were fed into the reliability model. The results show that the proposed model can perform well in comparison to the simulation output. In addition, some observations from the simulation experiments can also be applied to the design of a control system. © 1997 John Wiley & Sons, Ltd.     

车辆板簧系统的动力学研究

通过对车辆后轴板簧系统的建模,选择一个碰撞界面作为Poincaré映射的截面,解析法和数值法相结合,证明该系统通向混沌的道路不仅有倍周期道路,而且还存在拟周期道路等复杂的混沌演化过程。对该系统分岔与混沌行为的深入研究,为车辆和冲击振动系统的优化设计提供了依据。     

A STUDY OF PARTICLE MOTION IN TURBULENT SHEAR FLOW OF A SUSPENSION

A report is made on the measurement of turbulent shear flows of a two-phase suspension of particles in a carrier fluid by the recently developed laser-Doppler anemometry particle sizing techniques, one for small particles (smaller than 240 μm) and one for large particles (larger than 240 μm). A good deal of insights of the dynamics at the individual particle level has thus been gained which defy the explanations offered by the conventional macroscopic theories.

These new experimental findings have stimulated the development of a series of new theoretical approaches which are based on the individual particle's dynamical frequency response characteristics in a turbulent flow. These new theories provide explanations to the measured peculiar features of flow behavior as well as a better understanding of the physics of such flows.     

丙烯酸-丙烯酰胺的反相悬浮聚合及吸水性能的研究

以环己烷为连续相,十六烷基磷酸单酯为悬浮稳定剂,N,N＇-亚甲基双丙烯酰胺为交联剂,过硫酸盐为引发剂,采用反相悬浮聚合法合成了高吸水性丙烯酸钠-丙烯酰胺交联共聚物。研究了共聚物吸水性能与交联剂、引发剂用量、丙烯酸中和度、共聚单体组成、水中所含电解质浓度以及共聚物粒度的关系。制得的共聚物吸去离子水可达700g/g以上,吸0.9％NaCl溶液70g/g以上。     

偏氯乙烯—氯乙烯悬浮共聚速率模型

本文在偏氯乙烯－氯乙烯重量配比等于８５／１５的条件下，着重研究了引发剂浓度，温度等主要因素对悬浮共聚速率的影响，提出了共聚速率模型。在３５－６５℃温度范围内，建立了模型参数与聚合温度的关系式。在１０－８０％转化率范围内，本模型与实验结果能很好符合。     

悬索桥结构分析中索鞍的精确模拟

为在悬索桥结构分析中精确模拟索鞍,建立了索段一端固定于鞍座上的两节点“左鞍座单元”和“右鞍座单元”,以及索段中一点固定于鞍座上的三节点“鞍座单元”,此固定点为新单元的一个节点。它们通过自动调整索与鞍座的切点而处于平衡状态,从而简化了计算。单元算法的推导基于有限元分析的基本原理和弹性悬链线的精确解,并利用了处于平衡状态时索与鞍座之间的内力关系。新单元可以考虑鞍座重量的影响,鞍槽纵向曲线可为复合圆曲线。新单元可以同常规单元一样直接用于索结构的有限元分析,设计的算例验证了其正确性,工程算例显示了其在悬索桥结构分析中的应用。     

风-列车-大跨度悬索桥系统非线性耦合振动分析

考虑大跨度悬索桥结构的几何非线性因素,建立了风-列车-桥梁耦合系统动力分析模型。为了考虑结构大位移非线性因素的影响,在有限元建模时考虑悬索桥主缆自重垂度及缆索初始内力的作用,在动力平衡微分方程中增加了几何刚度矩阵,通过自编计算程序,研究了列车与风荷载同时作用下主跨1120 m的五峰山悬索桥设计方案的线性及非线性振动响应。计算结果表明,考虑结构的大位移非线性因素对桥梁位移及加速度时程曲线变化趋势的影响不大,但会使其响应极值减小,非线性因素对桥梁加速度产生的误差影响较大而对位移的误差影响较小。     

A METHOD FOR PREDICTING THE LIFETIME OF GAS TURBINE BLADES

–The article describes a method developed at ONERA for predicting the lifetime of gas turbine blades. This method makes use of non-linear viscoplastic constitutive laws, the problem being solved from a plane cross section assumption and through a time-step linearization. The initiation of the first macroscopic crack is calculated from a stabilized cycle condition. A blade test rig has been developed for checking the method under load and temperature conditions that are as close as possible to operational ones. The results of two series of tests on convection cooled IN100 blades prove the method to be acceptable to design engineers.     

一种通用的计算复合材料刚度的有限元方法

根据复合材料宏观有效模量的定义,本文通过在复合材料细观模型的边界施加六组特定形式的均匀边界条件,以三维有限元作为数值分析手段,对各种细观模型及增强相力学特性,可一次性全部解出复合材料的所有弹性系数。通过计算典型代表体元细观模型,验证了本文数值方法的准确性和优越性。     

INTERACTION OF GRAVITY AND ELECTROSTATIC EFFECTS IN PIPE FLOW OF A GAS-PARTICLE SUSPENSION

The interaction of gravity and electrostatic effects in isothermal, fully developed, horizontal turbulent pipe flow of dilute suspensions has been examined. Experimental study has validated the fact that, in the presence of gravity, increased space charge associated with increased local concentration due to gravity accentuates the asymmetry in mass flux and particles density distributions in the vertical plane passing through the pipe centerline. The space charge effect on the particle mass flux distribution near the pipe bottom is enhanced by increased particle density. Measurements were made with air suspensions of monodispensed particles of alumina and latex with non-uniform particle charge in pipes of 51 mm and 127 mm diameters.     

INTERACTION OF GRAVITY AND ELECTROSTATIC EFFECTS IN PIPE FLOW OF A GAS-PARTICLE SUSPENSION

ABSTRACT

The interaction of gravity and electrostatic effects in isothermal, fully developed, horizontal turbulent pipe flow of dilute suspensions has been examined. Experimental study has validated the fact that, in the presence of gravity, increased space charge associated with increased local concentration due to gravity accentuates the asymmetry in mass flux and particles density distributions in the vertical plane passing through the pipe centerline. The space charge effect on the particle mass flux distribution near the pipe bottom is enhanced by increased particle density. Measurements were made with air suspensions of monodispensed particles of alumina and latex with non-uniform particle charge in pipes of 51 mm and 127 mm diameters.     

悬索桥主缆线形解析方程解及应用

假设悬索桥主缆自重沿弧长均匀分布,加劲梁、桥面等其余恒载沿水平均匀分布,按考虑和不考虑主缆弹性伸长对主缆线比重影响的计算模型,根据主缆微元的力学平衡关系,通过引入一个参数u(shu=dy/dx),分别导出了悬索桥主缆成桥线形的解析参数方程。由边界条件,将定解问题转化为一组非线性方程组,以抛物线理论值为求解初始值,采用拟牛顿法求解中跨端点未知参数和主缆张力的水平分量。然后通过改变参数u来确定主缆线形坐标。最后由积分法导出了主缆索有应力和无应力长的计算公式。算例结果表明两种计算模型收敛速度较快,计算精度较高,都可以用于悬索桥设计与施工计算。     

一种估算结构件随机疲劳寿命的新方法

提出了基于随机载荷历程频率域信息──功率谱密度函数（Ｐ．Ｓ．Ｄ）估算结构件低周疲劳寿命的一种新的计算方法。采用这种方法只要已知应力历程的功率谱密度和材料应变疲劳性能参数就可对承载结构件进行随机疲劳寿命估算。因此，对于结构设计阶段的使用寿命预估具有实际意义。最后，通过对缺口件的随机疲劳寿命估算及与试验结果比较验证了本文方法的适用性。     

A CRACK CLOSURE MODEL FOR PREDICTING THE THRESHOLD STRESSES OF NOTCHES

A model is proposed to estimate the threshold stress range of a notched component. The model considers the variation of crack closure with crack length in the presence of a notch. The threshold stress range was found from the condition that the minimum value of effective threshold stress intensity range of a crack emanating from a notch equals the effective threshold stress intensity range of a “long” crack. The effects of notch depth, of notch acuity, of notch and specimen type, of load ratio, and of material properties on the threshold stresses were considered. Experimental data reported in the literature were used to assess the validity of the model. It was found that the model correctly predicts the behavior of cracks in notched components.     

悬索桥主缆系统数值解析法计算的一种收敛算法

从理论上证明了索段状态方程存在无解的情形,提出了在设计基准温度下成桥状态主缆系统数值解析法求解的迭代计算中存在收敛路径寻找的问题。针对已有数值解析法可能得不到解的缺陷,引入搜索算法和惩罚因子,对其进行改进,给出了惩罚因子的合理取值公式和改进后数值解析法的迭代步骤,确保了各种荷载情况的设计基准温度成桥状态主缆系统计算的快速高精度收敛。给出了数值解析法改进前不能收敛而按该方法改进后能收敛的算例。     

THE USE OF A LOAD SPECTRUM IN PREDICTING AIRFRAME FATIGUE DAMAGE

Abstract— The use of a load spectrum in airframe fatigue life predictions is considered. In-service fatigue lives are predicted using a probabilistic approach that takes into account the main aspects of deterministic methods. Expressions are derived for damage under fixed flight-hours together with data scatter. The influence of material fatigue properties on scatter are shown. An algorithm for obtaining simple formulae for accounting for equivalent airframe fatigue conditions are demonstrated. An example is given for deriving a safe fatigue life distribution function.     

交叉吊索用于改善悬索桥架设阶段的颤振稳定性

以某悬索桥设计方案为工程背景 ,应用多模态颤振分析方法 ,分析了该桥架设阶段颤振临界风速的发展趋势。以其中最危险的架设阶段为例 ,研究了在主缆与主梁之间设置交叉索这种结构措施提高系统颤振稳定性的效果。分析结果表明 ,交叉吊索可以显著地改善方案桥主梁架设阶段的颤振稳定性     

交叉吊索用于改善悬索桥架设计阶段的颤振稳定性

以某悬索桥设计方案为工程背景，应用多模态颤动分析方法，分析了该桥架设段颤振临界风速的发展趋势，以其中最危险的架设阶段为例，研究了在主缆与主梁之是设计交叉索这种结构措施提高系统颤动稳定性的效果，分析结果表明，交叉吊索可以显著地改善方案桥主梁架设阶段的颤振稳定性。     

THE DEVELOPMENT OF A MATHEMATICAL MODEL FOR PREDICTING THE DEPTH OF PLASTIC DEFORMATION IN A MACHINED SURFACE

The development and verification of a mathematical model for the prediction of plastic deformation in a machined surface are presented. The main assumption for developing this model is that there is a linear relation between plastic strain and the depth to which it extends. The model relates the work required to shear the workpiece material to the work needed to compress the workpiece material ahead of the cutting tool. The resulting depth of plastic deformation in the machined surface is a function of the true stress-strain characteristics of the workpiece material, the shear stress and shear strain on the shear plane, and the distribution of plastic strain. Results of the model agree well with data found in the literature. An improvement of the model is suggested through application of actual distribution data of plastic strain and calculation of frictional behavior on the rake face of the tool.     

高温悬浮态气固反应试验台的开发与应用

开发的高温、悬浮态气固反应试验台，是目前国内较先进的气固反应动力学试验装置，它能够比较接近生产实际状况地对各种粉体物料进行悬浮态气固反应动力学研究，所得规律可用来定量地指导工业反应器的设计和操作。