Déformation cumulée tensorielle dans le référentiel en rotation logarithmiqueCumulated tensorial strain measure in the logarithmic rotating frame.

The time integration of strain rate tensor $\stackrel{?}{\mathit{D}}$ is a central problem in large transformations even if it is often an underlying one. The cumulated tensorial strains, obtained by the time integration of strain rate tensor $\stackrel{?}{\mathit{D}}$, allow the tackling of this problem from a geometrical point of view, and independently of material behaviour considerations. The time integration here takes place in the local objective frame defined by the logarithmic spin proposed by Lehmann et al. and Xiao et al. The numerical results obtained in a closed deformation path are presented here. The advantages and drawbacks of this novel integration for the development of behaviour laws are described. To cite this article: V. Mora et al., C. R. Mecanique 332 (2004).     

固支加筋方板在爆炸载荷作用下的刚塑性动力响应分析

采用能量法分析了固支加筋方板在爆炸载荷作用下的刚塑性动力响应。提出了该类结构在这种载荷作用下的两种变形模态和模态判别条件，导出了计及膜力影响的最大残余横向变形的计算方法及计算公式。并对两种变形模态进行了试验研究，取得了理论计算值与试验值相一致的好结果。     

界面裂纹尖端有限变形弹性场的渐近分析

采用完全非线性弹性理论，研究了一类新的可压缩超弹性材料形成的界面裂纹问题，给出了平面应变条件下裂尖场的渐近解．揭示了界面裂纹尖端场的变形特征．     

正交各向异性薄板的弹塑性屈曲分析

本文应用混合硬化正交各向异性塑性理论和屈曲的能量法则，推导了正交各向异性薄板在面内压缩情况下的弹塑性稳定方程，计算了相应的临界荷载，并讨论几何形状、边界条件及诱导荷载比等对临界应力的影响。分析表明材料的各向异性性质对弹塑性临界应力的有较大的影响。     

微纳米晶金属的应变率敏感性及应变硬化行为分析

基于亚微米、纳米晶粒组织塑性变形过程中多种变形机制(位错机制、扩散机制及晶界滑动机制)共存,建立了理论模型,用于定量研究亚微米、纳米晶粒组织的塑性变形行为.以铜为模型材料,计算分析了晶粒尺度、应变率以及温度对亚微米、纳米晶粒组织塑性变形行为的影响.结果表明:相比粗晶铜,亚微米晶铜表现出明显的应变率敏感性,并且应变率敏感系数随晶粒尺度及变形速率的减小而增大;同时,增大变形速率或降低变形温度都能提高材料的应变硬化能力,延缓颈缩发生,进而提高材料的延性.计算分析结果与实验报道吻合.     

Boundary Conditions for Plate Bending in One-dimensional Hexagonal Quasicrystals

For plate bending in one-dimensional (1D) hexagonal quasicrystals (QCs), the reciprocal theorem and the general solution for QCs media are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all order for plates of general edge geometry and loadings. Through generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed data must satisfy these conditions in order that they should generate a decaying state. When a set of stress edge-data or mixed edge-data is imposed on the plate edge, these decaying state conditions for the case of axisymmetric deformation of 1D hexagonal QC plates are derived explicitly. They are then used for the correct formulation of boundary conditions for the plate theory solution (or the interior solution). Furthermore, in the absence of phonon–phason fields coupling effect, corresponding necessary conditions for the case of transversely isotropic elastic plates are derived subsequently, and their isotropic elastic counterparts are also obtained.      

Brittle to Quasi-Brittle Transition

Abstract. The present study focuses on the kinetic and non-deterministic aspects of the brittle to quasi-brittle transition. A solid is approximated by a lattice formed by the interacting continuum particles and the evolution of damage is estimated using particle dynamics. The onset of transition is measured by the rate of the change of correlation length. The proposed method is illustrated on the examples of creep rupture, strain localization and dynamic expansion of a circular void in a brittle plate.Sommario. Viene posta l'attenzione sugli aspetti cinetici e non deterministici della transizione dal comportamento fragile a quello quasi-fragile. Un solido viene approssimato da un reticolo formato da particelle interagenti e l'evoluzione del danno viene stimata tramite la dinamica delle particelle. L'inizio della transizione viene misurato tramite la variazione della lunghezza di correlazione. Il metodo proposto viene illustrato su esempi di rottura per creep, localizzazione della deformazione e l'espansione di un foro circolare in una piastra fragile.     

流场中聚合物共混体系液滴形变的理论模型

讨论了两相聚合物共混体系中，悬浮于另一种牛顿（或粘弹）液体中的牛顿（或粘弹）液滴的形变理论模型．影响液滴形变的主要因素有两相的组成、粘度比和弹性比、动态界面张力、临界界面张力系数，外流场形式及其强度．对于两相均为牛顿流体的体系，理论预测能够与实验相符；对于两相（或其中一相）为粘弹流体的体系，由于弹性的影响而使液滴形变的研究变得复杂，理论模型尚需完善．建立完整的液滴形变理论模型还需深入研究界面层、微观分子形变、液滴之间及液滴和连续相介质之间的相互作用对液滴形变的影响     

船用惯性系统试验安装标校与变形测量

船用惯性系统试验安装标校和变形测量是提高测量精度,保证试验质量的关键技术,因此在对设备的安装误差和船体变形造成的测量误差进行分析的基础上,重点阐述惯性系统试验零位对准和变形测量的相关理论和工程技术。     

A Method for Determining the Viscoelastic Characteristics of Composites

An efficient method for determining the deformation function of a composite is discussed. The method is based on a fractional exponential representation of the deformation functions of the composite components. The viscoelastic solution is obtained using the Volterra principle. The deformation function is represented as a function of a base operator. Thus, the problem is solved by approximating the deformation function by a continued fraction and applying the method of operator continued fractions. A computational procedure is detailed and illustrated using data on longitudinal relaxation of polymethylmethacrylate. As an example, the deformation of a polymethylmethacrylate-based fibrous composite with viscoelastic properties is analyzed__________Translated from Prikladnaya Mekhanika,Vol. 41, No. 5, pp. 9–21, May 2005.