关于蜂窝结构面内剪切模量的注记

本文指出Gibson等提出的等壁厚峰窝结构在面内剪力作用下的单元分析不满足平衡条件.本文建立了等壁厚与非等壁厚峰窝结构在面内剪力作用下的合理的单元分析,导出了蜂窝结构面内折合剪切模量G_(xy)的计算公式.本文结果与实验数据符合得很好.     

Shear instability direction at a crack-tip in a thermoviscoplastic body

Deformation fields near a crack tip are analyzed for a thermoviscoplastic body deformed either in an antiplane shear or in plane strain. The effects of inertia forces and heat conduction are considered, but those of material elasticity are neglected. By assuming that a shear band initiating from the crack-tip propagates in the direction of the maximum effective stress. It is found that a shear band propagates along the crack ligament in the body deformed in an antiplane shear. For a body undergoing plane strain deformations, the direction of the propagation of the shear band depends upon the mode-mixity parameter and agrees with that observed by Kalthoff.     

Central Circular Sections of the Strain Ellipsoids

A simple direct proof is given of the known result that in any deformation x = x(X), the planes of the central circular sections of the material strain-ellipsoid at X are deformed into the planes of the spatial strain-ellipsoid at x. This revised version was published online in August 2006 with corrections to the Cover Date.     

变高度连续箱梁剪力滞效应试验研究

建立一三跨变高度连续箱梁和单跨变高度悬臂箱梁有机玻璃实验模型，三跨连续箱梁模型的跨径为46cm 86cm 46cm，箱梁高度沿纵向按二次抛物线变化，变化规律为y=4 0.0025x^2，单跨悬臂箱梁模型取自三跨连续箱梁的边跨，分别进行了集中载荷、均匀载荷作用下的剪滞效应试验研究。采用YJ-25静态电阻应变仪、平衡箱、电测读数稳定器，并用全桥测量，温度自补偿方法测定应变值，各种测试值均取分级荷载下读数的平均值，测量得到剪滞效应的应力、应变分布规律。模型试验的整个期间室内温度基本保持为18℃～20℃之间。用有限元法和有限段法对该模型进行了应力计算，与试验结果比较吻合较好。试验结果成功地应用于一种新的有限段法的考核。     

软土的各向异性损伤对剪切带形成的影响

在软土各向异性弹塑性损伤模型的基础上,把小应变模型扩展到有限应变模型,推导出不排水平面应变条件下的剪切带形成条件,分析K0固结状态下各向异性损伤对剪切带形成的影响.以上海软土为例,分析临界状态参数β=0.9时,损伤变量D1,D2的不同组合的剪切角和简单剪切模量与有效平均主应力比(g/p')的关系曲线.计算结果表明,损伤变量越大,越接近不稳定状态,垂直方向损伤对剪切带的影响比水平方向的强烈. 特别指出无论土为横观各向同性损伤的情况,还是各向异性损伤的情况,在本文研究的条件下,不稳定状态(g/p'为最小值)相应两个剪切角约在50°和130°,这对研究弹塑性损伤对剪切带形成与变化有指导意义.     

一种计入横向剪切变形的各向异性板弯曲分析新方法

本文提出一种各向异性板弯曲分析新方法,既考虑了横向剪切变形影响,又具有经典理论的简明性,易被工程人员接受。算例表明,本文方法分析精度较高。     

A Note on the Influence of Cohesive Stress-Separation Laws on Elastic Stress Singularities in Antiplane Shear

Elastic stress singularities occur at the vertices of reentrant corners with traditional, stress-free, boundary conditions. By recognizing cohesive stress action at sharp corners, and also introducing consistent cohesive laws ahead of corners, these singular stresses can be removed. This was earlier shown asymptotically for plane strain states: Here it is shown asymptotically for antiplane shear states.      

基于三阶剪切变形理论的悬臂输流管道自由振动

采用三阶剪切变形理论,结合有限元法研究了悬臂输流管道的自由振动问题．利用虚功原理建立了输流管系统的有限元方程,同时将悬臂端弹性支承以势能的形式引入到系统方程中,求解了系统前三阶的复频率．分别探讨了流体速度和弹簧刚度对系统复频率实部和虚部的影响,重点分析了弹簧刚度与前三阶固有频率间的关系．在弹性支承刚度为零的特例下,对比了本文结果与Timoshenko梁理论的结果,证明了本文方法的可靠性．研究发现系统固有频率的实部恒为负值,表明一端带有弹性支承的约束形式有利于提高悬臂输流管道自由振动的稳定性;流体的流动对管道振动起到了阻尼作用,在流动速度足够大的情况下,各阶振动固有频率均趋于零;当弹簧刚度为无穷大,且流体速度足够大时,输流管道将发生失稳．     

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讨论由一类超弹性材料—Blatz-Ko材料所组成的薄壁圆管在内压力作用下平面有限变形问题,得到了管径变化与内压力之间的解析关系．     

In General There Are No Unsheared Tetrads

Suppose the principal stretches are all different at a point P in a deformed body. In this case, it has been shown [1] that generally there is an infinity of non coplanar infinitesimal material line elements at P which remain unsheared following the deformation – that is, the angle between the arms of each pair of material line elements forming the triad remains unchanged. Here it is shown that in this case when all three principal stretches at P are different, there is no set of four infinitesimal material line elements, no three of which are coplanar, and such that the angle between each pair of the six pairs of material line elements is unchanged following the deformation. It is only when all three principal stretches at P are equal to each other, that there are unsheared tetrads at P, and in that case all tetrads are unsheared. This revised version was published online in June 2006 with corrections to the Cover Date.     

三轴测力传感器的剪切力高阶效应实验研究

本文通过实验,指出剪切力会使具有某种结构的三轴测力传感器产生高阶正应力效应,这种效应在理论上属于非线性弹性力学中的简单剪切问题,被称为“Poynting效应”,它有时严重地影响测力传感器的使用,甚至导致实验失败。然而,这种现象在线弹性力学中是无法解释的。因此,它应该引起三轴测力传感器设计者的注意。     

Deformation analysis of laser spectra based on S-R decomposition theorem

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A Note on Design of Fiber-Nets for Maximum Stiffness

For a specific fiber-net, the design variables are relative fiber density and fiber orientations. With a given amount of fibers, our objective is to maximize the stiffness (minimize the compliance) for a continuum subjected to a given load situation. Analytical optimality criteria are derived, and numerical optimization procedures are presented. Applications to a wedge problem from the literature, Royer-Carfagni (2000), and to a skew plate problem are shown, and the study includes the influence of a basic material to be reinforced. The procedure described can be combined with localized optimal design for density, orientation, and shape, “pointwise” or for design regions.     

计入横向剪切变形时层合板位移差分解法

在考虑横向剪切变形对层合板弹性解的影响时，本文提出一种数值计算方法。由边界条件给出边界结点位移的表达式，根据薄板的经典理论和一阶横向剪切变形理论导出位移增量所满足的平衡微分方程，引用经典理论计算的横向剪力修正了荷载列阵。致使在较粗的网格划分时、宽广的层合板长厚比范围内，仍能得到与解析解颇为一致的数值解。     

一种考虑横向剪切变形的三角形板弯曲单元

本文从部分协调的三角形薄板弯曲单元出发,并假设横向剪切应变在单元内线性变化,提出了一种考虑横向剪切变形的具有15个自由度的三角平板弯曲单元。该单元应用于薄板和中等厚度板分析均有较高的精度,计算效率高,可用于工程中具有复杂形状的薄板和中等厚度板结构的分析。     

剪切增稠液的力学性能与机理

剪切增稠液(shear thickening fluids,STFs)是一种新型功能材料,论文对其最新进展进行综述和评价.首先介绍了高性能STF的研制,分析了STF在不同外加载荷下的力学行为;然后从实验和理论等方面讨论了STF机理的研究现状;最后对STF的实际应用进行了总结,并对STF的发展前景进行了展望.     

剪切变形对FGM圆板轴对称屈曲的影响

基于一阶剪切变形板理论，推导了功能梯度材料圆形板在边界面内均布压力作用下的轴对称屈曲方程。在推导过程中，忽略了前屈曲耦合变形。利用一阶板理论与经典板理论屈曲方程之间在数学形式上的相似性，得到了一阶板理论下功能梯度材料圆板与经典板理论下均匀圆板临界屈曲载荷之间的解析关系。利用这个解析关系，可以直接从已有的较为简单的经典理论的结果，获得一阶板理论下功能梯度材料板的临界屈曲载荷。     

Shear Failure of Inconel 718 under Dynamic Loads

Kinetics of deformation and fracture of nickel–iron alloy Inconel 718 under dynamic shear loading was measured using a split torsional Hopkinson bar facility and high-speed photography. Tubular specimens with a reduced gage length and a starter notch were sheared at strain rates up to 6 × 10³ s⁻¹. High-speed photographs of fiducial lines scribed on the specimen surface showed the development of local strains and cracking. This paper describes the experimental and analytical procedures, illustrates average and local plastic strain evolution, and presents shear crack initiation times and propagation speeds.     

岩土中的剪切带局部化问题研究:回顾与展望

回顾了圆弧滑动面理论的产生及其在土坡抗滑动稳定分析和极限承载力计算中的应用，并指出了圆弧滑动面理论和刚塑性理论及极限平衡条件的关系及其局限性。介绍了剪切带局部化问题的研究现状，包括一些热点研究领域和最新研究成果。着重介绍了用子负荷面模型模拟超固结黏性土剪切带局部化和用动态剪切带单元模拟摩尔一库仑材料剪切带局部化的最新研究成果。对剪切带局部化问题研究提出了几个主要发展方向。     

温度和剪应变率历史对扭转载荷作用下铁基合金本构关系影响的研究

用间歇式加载的方法,研究了温度和剪应变率历史在20 ～500℃和0 .00167 ～800s- 1 的范围内对扭转载荷作用下铁基合金本构关系的影响。试验结果表明:应变率历史对该材料具有强化作用,而且其强度随剪预应变率的升高而提高;其对剪应变率历史的敏感性则随着温度的升高而降低。