两类特殊三次空间Bézier曲线的挠率特征分析

空间Bézier曲线的挠率在几何造型中被广泛应用. 文中利用笛卡尔符号法则讨论了两种特殊三次空间Bézier曲线的挠率单调性问题, 最后得出当空间三次Bézier曲线的控制边相等且中间控制边和相邻两控制边的夹角相等时, 挠率仅有一个极小值; 而当两夹角相等但控制边长成等差数列时, 文中给出了挠率单调及极值存在的充分条件.     

开口厚壁截面短构件的约束扭转1）

为了分析开口厚壁截面短构件的约束扭转问题,采用统一分析梁模型与有限节线法,对T形和L形厚壁截面短构件约束扭转时横截面的翘曲和应力分布情况等问题进行了分析研究.算例计算结果表明：开口厚壁截面短构件存在与其横截面形心位置不一致的扭转（弯曲）中心,构件在不过扭转中心的外力作用下会产生弯扭耦合变形,其横截面将产生不均匀翘曲,横截面上的翘曲正应力和扭转剪应力均呈非线性分布.     

基于扭秤的激光干涉差动测量微小冲量方法

基于扭秤测量冲量原理,结合激光干涉法差动测量角度的方法,提出一种基于扭秤的激光干涉差动测量微小冲量的方法。介绍系统的基本组成和测量过程,给出扭秤结构设计参数,并对系统参数进行了标定,结合设计参数与标定结果,对系统的分辨率、量程和精度进行了校核,在典型的测量环境下,对激光烧蚀靶材所形成的Ns量级微小冲量进行了测量,给出了典型的测量结果并进行分析。结果表明:所提出的基于扭秤的激光干涉差动测量微小冲量方法,系统分辨率可达10-7Ns量级,测量范围跨5个数量级,最大可以测量10-2Ns量级冲量,测量精度优于95%。     

圆中空夹层钢管混凝土柱扭转实验研究

以名义含钢率、外钢管强度和空心率为主要变化参数,设计了6根圆中空夹层钢管混凝土和1根双层空钢管试件,对其进行了扭转试验研究。试验结果表明:在加载过程中,钢管和混凝土变形协调,共同工作;试件表现出很好的塑性性能;试件名义含钢率和外钢管强度越大,试件抗扭承载力也越大;空心率越大,试件抗扭承载力也越大;圆中空夹层钢管混凝土比双层空钢管抗扭承载力有明显的提高。同时用有限元方法对试件扭矩-转角全过程曲线进行计算,计算结果与试验结果吻合良好。     

Tension–torsion fracture experiments – Part II: Simulations with the extended Gurson model and a ductile fracture criterion based on plastic strain

An extension of the Gurson model that incorporates damage development in shear is used to simulate the tension–torsion test fracture data presented in Faleskog and Barsoum (2013) (Part I) for two steels, Weldox 420 and 960. Two parameters characterize damage in the constitutive model: the effective void volume fraction and a shear damage coefficient. For each of the steels, the initial effective void volume fraction is calibrated against data for fracture of notched round tensile bars and the shear damage coefficient is calibrated against fracture in shear. The calibrated constitutive model reproduces the full range of data in the tension–torsion tests thereby providing a convincing demonstration of the effectiveness of the extended Gurson model. The model reinforces the experiments by highlighting that for ductile alloys the effective plastic strain at fracture cannot be based solely on stress triaxiality. For nominally isotropic alloys, a ductile fracture criterion is proposed for engineering purposes that depends on stress triaxiality and a second stress invariant that discriminates between axisymmetric stressing and shear dominated stressing.     

引力波探测中的被动隔振系统

介绍了引力波探测实验中的被动隔振系统的基本原理和研究现状,讨论其性能及特点.低频被动隔振系统,如七级气体弹簧隔振系统,多级隔振堆,四级悬臂弹簧隔振系统以及三级弯曲弹簧隔振系统在10Hz以上,都具有好的隔振性能;倒摆、折叠摆、 X摆和锥摆等超低频水平隔振系统实现了几十秒的共振周期;建立在对称扭杆弹簧系统基础上,构思新颖的被动垂直隔振系统克服了传统被动垂直隔振系统无法解决的困难,实现了超低频被动垂直隔振.      

Stress state of a cross-base prism under torsion

The stress state of a cross-base prism under torsion is analyzed. The lower- and upper bounds for stresses are found by solving an infinite system of linear algebraic equations and using Koyalovich’s limitants method. It is proved that the infinite system is regular and that its solution exists and is unique. The asymptotic behavior of the unknowns is established. The convergence of the series for stresses is accelerated Translated from Prikladnaya Mekhanika, Vol. 44, No. 11, pp. 79–93, November 2008.     

基于小子样理论的坦克扭力轴疲劳寿命分析

基于小子样的思想,探讨扭力轴表面缺陷对其疲劳寿命的影响,有助于进一步找到降低扭力轴表面凹坑对扭力轴疲劳寿命影响的方法.     

四阶整数辛群中扭元的共轭类

本文给出四阶整数辛群中扭元的全部共轭等价类.总共有55个不同的扭元等价类,它们的阶数分别是2, 3, 4, 5, 6, 8, 10, 12.没有其它阶的扭元.     

The ultimate state of polymeric materials and laminated and fibrous composites under asymmetric high-cycle loading

The prediction of the high-cycle fatigue strength of polymeric and composite materials in asymmetric loading is considered. The problem is solved on the basis of a nonlinear model of ultimate state allowing us to describe all typical forms of the diagrams of ultimate stresses. The material constants of the model are determined from the results of fatigue tests in symmetric reversed cycling, in a single fatigue test with the minimum stress equal to zero, and in a short-term strength test. The fatigue strength characteristics of some polymers, glass-fiber laminates, glass-fiber-reinforced plastics, organic-fiber-reinforced plastics, and wood laminates in asymmetric tension-compression, bending, and torsion have been calculated and approved experimentally. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 87–102, January–February, 2008.