碳纤维布加固超役混凝土电杆的破坏机理及力学性能

以某电网某路段超过服役期的钢筋混凝土电杆为研究对象,选取电杆杆身与跨中带钢圈接头的杆身试件各6根,其中各取3根试件采用碳纤维布（CFRP）沿杆件纵向进行加固,并对其进行抗弯承载力试验,对比研究在不同的碳纤维布黏贴层数下加固电杆的受力性能和破坏机理。基于试验实测数据,对强度及刚度计算方法进行了研究,并提出了刚度退化的数学表达式。研究结果表明：采用碳纤维布加固电杆后,其破坏表现为混凝土与碳纤维布的表面粘脱失效所致,纵向碳纤维布被拉断作为最终破坏形态,破坏过程迅速,脆性明显;试件的截面应变分布符合平截面假定。加固前杆身试件的承载力退化严重,加固后混凝土电杆的承载能力和刚度均有显著提高,但加固电杆的损伤发展较加固前提早,且快而集中,综合多方面考虑,建议在混凝土电杆接头附近的一定距离内采取双层、杆身其余部位采用单层的碳纤维布加固方法。     

任意形状工件的体积测量仪

介绍了作者研制的任意体积测量仪(已拥有发明专利)的原理、结构和测量方法,并对某厂生产的汽车连杆成形各工步的整体体积、局部体积进行了实测。结果表明,该测量仪具有结构简单、测量精度高的特点,不仅能够测量密度大于水的工件的任意体积,还可以测量密度小于水的工件的任意体积。     

LMI Approach to Robust H∞/H2 Controller Design with Regional Poles Constraint of a Pump-Motor System

Whenfacing withthe practical servosystemcon-trol problem,the control systemis often required tomeet many performance indexes which include ti medomain,frequency domainand H∞/H2.Theseindex-es have explicit purpose and appliedsituation.For ex-ample,the H∞normbetween disturbance and outputrepresents the capability of noise-i mmune,the smallerthe H∞normis,the more excellent stiffness the sys-temhas.And the square of H2norm between inputand output is equal to the energy of the systempulserespo…     

侧向载荷下圆柱壳体断裂的ALE法数值模拟

为了了解侧向爆炸冲击载荷下圆柱壳体断裂过程,采用任意拉格郎日-欧拉方法、爆轰产物采用JWL状态方程对侧向爆炸冲击载荷作用下圆柱壳体断裂过程进行了数值模拟和分析．模拟结果表明,圆柱壳体爆炸断裂所需炸药量与壳体壁厚为递增线性关系,且这个线性关系的斜率随壁厚不同而改变．在其他条件相同的情况下,壳壁越厚,增加炸药量爆炸时壳体单元最大应力增加越慢．     

Stress integration and mesh refinement for large deformation in geomechanics

This paper first discusses alternative stress integration schemes in numerical solutions to large‐ deformation problems in hardening materials. Three common numerical methods, i.e. the total‐Lagrangian (TL), the updated‐Lagrangian (UL) and the arbitrary Lagrangian–Eulerian (ALE) methods, are discussed. The UL and the ALE methods are further complicated with three different stress integration schemes. The objectivity of these schemes is discussed. The ALE method presented in this paper is based on the operator‐split technique where the analysis is carried out in two steps; an UL step followed by an Eulerian step. This paper also introduces a new method for mesh refinement in the ALE method. Using the known displacements at domain boundaries and material interfaces as prescribed displacements, the problem is re‐analysed by assuming linear elasticity and the deformed mesh resulting from such an analysis is then used as the new mesh in the second step of the ALE method. It is shown that this repeated elastic analysis is actually more efficient than mesh generation and it can be used for general cases regardless of problem dimension and problem topology. The relative performance of the TL, UL and ALE methods is investigated through the analyses of some classic geotechnical problems. Copyright © 2005 John Wiley & Sons, Ltd.     

A quadrature formula for integrals with nearby singularities

The purpose of this paper is to propose a new quadrature formula for integrals with nearby singularities. In the boundary element method, the integrands of nearby singular boundary integrals vary drastically with the distance between the field and the source point. Especially, field variables and their derivatives at a field point near a boundary cannot be computed accurately. In the present paper a quadrature formula for ??‐isolated singularities near the integration interval, based on Lagrange interpolatory polynomials, is obtained. The error estimation of the proposed formula is also given. Quadrature formulas for regular and singular integrals with conjugate poles are derived. Numerical examples are given and the proposed quadrature rules present the expected polynomial accuracy. Copyright © 2006 John Wiley & Sons, Ltd.     

An extended finite element formulation for contact in multi‐material arbitrary Lagrangian–Eulerian calculations

Multi‐material Eulerian and arbitrary Lagrangian–Eulerian methods were originally developed for solving hypervelocity impact problems, but they are attractive for solving a broad range of problems having large deformations, the evolution of new free surfaces, and chemical reactions. The contact, separation, and slip between two surfaces have traditionally been addressed by the mixture theory, however the accuracy of this approach is severely limited. To improve the accuracy, an extended finite element formulation is developed and example calculations are presented. As a side benefit, the mixture theory is eliminated from the multi‐material formulation, eliminating the issues associated with the equilibration time between adjacent materials. By design, the new formulation is relatively simple to implement in existing multi‐material codes, parallelizes without difficulty, and has a low memory burden. Copyright © 2006 John Wiley & Sons, Ltd.     

平面运动刚体的惯性力系向任一点的简化

根据理论力学的知识，利用矢量法进行严密的数学推导，得出了作平面运动的任意刚体的惯性力系向任一点简化的结果，并由此结果进一步推导出了有对称平面的刚体在对称平面内作平面运动的惯性力系向其质心简化的结果，与目前出版物上的结果相一致。解决了多年来学习对平面运动的刚体的惯性力系简化结果的困惑，也为工程人员计算动力学问题提供了帮助。     

任意约束边界条件下初始缺陷压杆的稳定性分析

对各种边界条件下初始缺陷压杆的稳定性进行了系统的研究,讨论了不同边界条件和初始挠度对压杆稳定性的影响,得出了求解弹性边界约束系数、端点转角、端点弯矩和压杆挠度的公式,为进一步的理论分析打下了基础。     

分割多边形成凸多边形的算法

提出将任意简单多边形分割成若干个凸多边形的一种算法，主要思想是：首先确定多边形的凹点，然后利用连接凹点与落入该点Ｂ域中顶点的方法，消去该凹点，从而分割原多边形成两个子多边形，最后对子多边形递归使用该方法，直至消去全部凹点该算法分割多边形成Ｏ（ｌ）个凸多边形，其时间复杂性是Ｏ（ｎ）次乘法，其中ｎ是多边形的顶点个数，ｌ为凹点数目