考虑应力三轴度的循环塑性数值分析

应力三轴度为静水应力与Mises等效应力的比值。静水应力导致体积变化,Mises等效应力反应形状改变。应力三轴度作为描述应力状态的参数,同时反映了体积变化和形状改变。以往循环塑性的研究对应力状态的考虑非常少,本文利用有限元软件ABAQUS提供的Chaboche组合硬化模型进行数值加载模拟,材料选用工业纯铜(T2),利用袁确定材料参数的方法确定参数值,并和试验结果对比分析确定参数的合理性;然后对不同应力三维度下的体胞模型进行有限元计算,分析应力三轴度对循环塑性的影响,得到影响的具体结论。     

三亚东河桥空间静动力分析

三亚东河桥是钢管混凝土桁架梁，其高跨比为桁梁国内之最。其强度、刚度、稳定性、动力性能满足规范要求。本文给出了计算模型，计算结果主要包括主桁的支点反力、竖向位移及轴力、最大应力，分析了本桥前三阶段的结构自振特性。提出了混凝土退出工作的临界条件，最不利应力的位置，中跨跨中几种可能状态下的最大应力值，墩顶位置的最大应力值及其原因。     

三亚东河桥空间静动力分析

三亚东河桥是钢管混凝土桁架梁,其高跨比为桁梁国内之最.其强度、刚度、稳定性、动力性能满足规范要求.本文给出了计算模型,计算结果主要包括主桁的支点反力、竖向位移及轴力、最大应力,分析了本桥前三阶段的结构自振特性.提出了混凝土退出工作的临界条件,最不利应力的位置,中跨跨中几种可能状态下的最大应力值,墩顶位置的最大应力值及其原因.     

复杂应力条件下砂土的强度规律及传统强度准则适应性分析

在砂土真三轴试验的基础上,分析了砂土在复杂应力条件下的强度变化规律,以及三个经典的强度理论(Lade-Duncan准则、Matsuoka-Nakai准则、Mohr-Coulomb准则)和真三轴试验之间的差异,探讨在复杂应力条件下经典强度准则的适应性,定量指出各个准则的强度误差。结果表明,在不同应力路径下,经典强度准则的常数项并不一直为常数,而是随着应力路径的变化而变化。在三个经典强度理论中,Mohr-Coulomb准则试验误差最大,Lade-Duncan准则试验误差最小。对于砂土,中主应力对强度参数φ值有一定影响。对于强度参数φ13随着中主应力比b值的增大而增大,在平面应变状态下(b=0.3左右)达到最大值,之后趋于稳定。     

全珊瑚海水混凝土的运用

海岛砂石材料少,但珊瑚礁繁多,珊瑚混凝土是指由珊瑚(砂)、水泥、外加剂和矿物掺合料等原材料按照一定的配合比制成的一种新型混凝土,珊瑚混凝土研究成为近年土木工程领域的研究热点。现有的珊瑚混凝土力学性能方面的研究,基本为单轴受力性能的研究,对于复杂应力状态下其受力性能的研究鲜有报道。珊瑚混凝土结构在工程应用中,往往处于多轴作用的复杂应力状态。因此,非常有必要对珊瑚混凝土在复杂应力状态下的受力性能进行更为深入、系统研究。     

复合应力状态下的混凝土强度研究与展望

通过大量国内外文献分析与研究,对复合应力状态下的混凝土强度研究进行了综述,分别介绍了复合应力状态下普通混凝土、活性粉末混凝土、塑性混凝土、再生混凝土及纤维混凝土强度的研究情况,并分析了它们的研究前景。     

泾渭地区深层Q2黄土工程力学特性的试验研究

Q2黄土是中更新世沉积具有弱湿陷性和结构性的粘性土.文中以真三轴仪为基础,模拟了在三维应力条件下Q2黄土的受力状况,进行了不同固结围压、含水率和中主应力比下Q2黄土的真三轴试验,研究了不同含水率黄土的应力应变特性.得到了如下结论:通过4种含水率、4种中主应力比、4种不同固结围压下的Q2黄土真三轴试验结果,分析了复杂应力...     

滚滑状态下轮轨热结构耦合应力应变分析

利用有限元软件ANSYS对轮轨在同一速度下的不同状态下进行数值仿真,分析轮轨的应力应变及温度变化规律。结果表明:在滚滑分析时,钢轨的等效应力比纯滑动的明显小,轮子的等效应力没有明显变化;虽然在滚滑状态下比滑动状态下轮轨的温度和塑性应变小,但减小幅度不大。     

钢结构稳定设计的探讨

通过几年的钢结构设计,探讨一下有关钢结构稳定方面的一些内容。本文针对钢结构稳定设计提出了在设计过程中设计人员应须明确了解的一些基本概念,以便设计人员参考。强度问题是指结构或者单个构件在稳定平衡状态下由荷载所引起地最大应力（或内力）是否超过建筑材料的极限强度,因此是一个应力问题。极限强度的取值取决于材料的特性,对混凝土等脆性材料,可取它的最大强度,对钢材则常取它的屈服点。稳定问题则与强度问题不同,它主要是找出外荷载与结构内部抵抗力间的不稳定平衡状态,即变形开始急剧增长的状态,从而设法避免进入该状态,因此,它是一个变形问题。如轴压柱,由于失稳,侧向挠度使柱中增加数量很大的弯矩,因而柱子的破坏荷载可以远远低于它的轴压强度。显然,轴压强度不是柱子破坏的主要原因。     

车辆轮轴过盈配合装配应力的一种非线性接触有限元分析

文中使用SolidWorks2007——COSMOSWorks软件对车辆轮轴各种过盈配合方式进行有限元分析计算。主要考虑过盈量、有无突悬量和过渡圆弧半径对车轴应力分布的影响。计算结果表明:过盈量是决定轮对过盈配合应力的主要因素。有突悬量时,车轴的应力集中得到缓和,轮毂的应力偏大一些。过渡圆弧半径大时,过渡圆弧部位应力状态较好,轮座与轴身应力较高;过渡圆弧半径小时,轮座与轴身应力较好,圆弧中部应力变化率较大。     

Effects of axial and residual stresses on thermoelastic damping in capacitive micro-beam resonators

This paper deals with effects of residual and axial stresses on thermoelastic damping (TED) in micro-beam resonators. Equations of coupled thermoelastic case for a capacitive micro-beam resonator have been governed using two dimensional non-Fourier heat conduction model based on continuum theory frame. A Galerkin based finite element formulation has been used to analyze TED for the first mode of vibration of the micro-beam resonator with both ends clamped and isothermal. Effect of axial stresses owing to stretching of the micro-beam on the TED ratio has been investigated. As results illustrate, this effect gets importance only when the resonator is vibrating about a large static deflection due to a bias DC voltage close to the pull-in voltage of the resonator, otherwise it can be neglected in calculations. Effect of compressive and tensile residual stresses has been also studied. The results show that compressive (tensile) residual stresses increase (decrease) the TED ratio considerably. The residual stresses effect has been also studied for various values of the micro-beam thicknesses. The results illustrate that the effect of residual stress on the TED ratio decreases by increasing the thickness of the micro-beam. The results show that, applying DC voltages near the pull-in voltage increases energy dissipation due to the TED considerably, therefore, there is a limitation for applied DC voltage for resonators, since residual stresses change the pull-in voltage of the resonator, hence, existing residual stresses can change the interval of the applied voltage limitation.     

桑树的种质资源、生态适应性及其应用前景

阐述了我国桑树种质资源的分布情况及其抗逆性和生态适应性,主要包括：耐寒性、耐渍性、抗旱性和抗污染及抗病虫害特性等．并以其生态适应性为基础,探讨了其在生态环境建设中韵潜力,以期为进一步拓展桑树资源的综合利用提供参考依据。     

An inverse quasi-static steady-state thermal stresses in a thick circular plate

The present paper deals with the determination of unknown temperature and thermal stresses on the upper surface of a thick circular plate. A thick circular plate is subjected to arbitrary known interior temperature under steady state. The fixed circular edge and lower surface of the circular plate are thermally insulated. The governing heat conduction equation has been solved by using Hankel transform methods. The results are obtained in series form in terms of Bessel's functions. The results for displacement and stresses have been computed numerically and illustrated graphically.     

对当前我国"数字鸿沟"问题研究的回顾与展望

本文简要回顾了我国关于“数字鸿沟”问题的研究历程；并对研究重点作了介绍；同时指出当前研究中存在的问题以及“数字鸿沟”问题的研究方向。     

A more rational approach to the problem of an elastoplastic thick-walled cylinder

A new incremental theory has been developed for solving the problem of partially yielded thick-walled cylinders. Incremental stresses and strains are directly used as variables, hence numerical differentiation in the evaluation of stresses and strains is not required. The stresses and strains in all principal directions can be computed at the same time from governing equations for each increment of loading. Since the consideration of loading history is involved, the present theory is particularly suitable for predicting stress and strain distribution of a thick-walled cylinder subjected to nonproportionate loading.     

论演讲稿语言冲击力生成模式

本文着重从语言表达的角度探讨演讲冲击力的生成模式：言之有物,演讲冲击力生成的支撑;言之灼灼,演讲冲击力生成的助推器;言之有效,演讲冲击力生成的归宿。     

CAS to make nine changes

CAS has to realize the following nine transitions under the guidance of thescientific outlook on development, stresses CAS President LU Yongxiang.     

独立学院财务管理浅谈

本文着重表述了独立学院财务管理的特点以及管理过程中的主要问题和应采取的对策,为独立学院的健康发展提出意见和建议。     

Stresses and deformations in pipe flanges subjected to creep at high temperatures

Various solutions have been made for determining the stresses in pipe flanges using the theory of elasticity (I). There are many cases, however, of pipe flanges which are subjected to stresses and at the same time a high temperature such that creep occurs.This paper gives an analysis of the stresses and deformations produced in a circular ring of rectangular cross section subjected to twisting couples uniformly distributed along its center line. Such a solution will also give an approximate analysis of the pipe flange. This approximation is justified in view of the complexity of the problem and the uncertainties still present in the fundamental creep-stress relation for metals. In the solution of this problem a deflection theory is also developed for straight beams subjected to bending accompanied by creep.     

大跨度V型墩连续刚构桥预应力空间效应分析

某桥为一座单箱双室变截面V型墩连续刚构桥,采用三向预应力体系,结构受力复杂,而设计时一般多采用平面计算方法,无法合理评定预应力筋的空间效应。采用有限单元法对其进行了三维实体有限元模拟计算,着重对三向预应力筋的空间效应进行了分析,对同类桥的设计提供了参考。