纤维增强树脂基复合材料的疲劳剩余刚度研究进展

回顾了过去二十年来公开发表的复合材料刚度退化的主要模型,对这些模型做了分类和讨论.按照模型的理论基础及研究方法将它们分为了理论模型、半经验模型和经验模型三类.理论模型是指那些完全依赖于力学分析而得到的模型,这类模型建立了材料的微观损伤机理与宏观刚度退化之间的关系.经验模型通常不需要过多的力学分析,仅对大量实验数据进行经验性拟合,一般具有简单易用的形式.半经验模型是理论与经验模型的结合------在力学分析基础上的经验处理.      

固体非均质炸药冲击点火与起爆模型研究进展

综述了固体非均质炸药冲击点火与起爆模型研究的进展,主要探讨基于经验数据模型、微观机制 模型和分子动力学理论模型这3类模型的理论基础、存在的问题和工程应用前景,认为基于微观机制点火与 起爆模型具有物理概念清晰以及能够预测实验结果的优点和较好的工程应用前景,提出了后续发展的建议。     

基于人工神经网络的湍流大涡模拟方法

大涡模拟方法(LES)是研究复杂湍流问题的重要工具,在航空航天、湍流燃烧、气动声学、大气边界层等众多工程领域中具有广泛的应用前景.大涡模拟方法采用粗网格计算大尺度上的湍流结构,并用亚格子(SGS)模型近似表达滤波尺度以下的流动结构对大尺度流场的作用.传统的亚格子模型由于只利用了单点流场信息和简单的函数关系,在先验验证中相对误差较大, 在后验验证中耗散过强. 近几年来,机器学习方法在湍流建模问题中得到了越来越多的应用.本文介绍了基于人工神经网络(ANN)的湍流亚格子模型的最新进展.详细地讨论了人工神经网络混合模型、空间人工神经网络模型和反卷积人工神经网络模型的构造方法.借助于人工神经网络强大的数据插值能力,新的亚格子模型的先验精度和后验精度均有显著提升. 在先验验证中,新模型所预测的亚格子应力的相关系数超过了0.99,在预测精度上远高于传统的大涡模拟模型. 在后验验证中,新模型对各类湍流统计量和瞬态流动结构的预测都优于隐式大涡模拟方法、动态Smagorinsky模型、动态混合模型等传统模型.因此, 人工神经网络方法在发展复杂湍流的先进大涡模拟模型中具有很大的潜力.      

Dynamics of medium thickness plates interacting with a periodic Winkler’s foundation: non-asymptotic tolerance modelling

Medium thickness plates resting on a periodic Winkler’s foundation are investigated. New averaged non-asymptotic models for those plates are proposed. These models are based on the tolerance averaging technique. The main feature of these models is that they describe the effect of period lengths on the overall behaviour of the plate. It is also shown that from governing equations of these models, equations of simplified averaged models (called asymptotic models) can be obtained. An additional interesting feature of the proposed models is that the equations describe also the effect of normal stress in the thickness direction.     

引入惯性力影响的海底埋设管线的抗震设计方法

在现有海底管线抗震规范的基础上，根据海底铺设环境的实际情况，在考虑管线惯性力影响的情况下，提出了管土动力响应的新的力学模型，侧重分析引入惯性力与土壤滑移的影响，结合实际工程参数，对考虑惯性力后的动力学方程进行了仿真计算，比较了引入和不引入惯性力两种抗震设计方法的结果，这对海底管线的抗震设计有一定的参考和实际应用价值。     

求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

地质材料本构模型的最近进展

本文回顾工地质材料本构模型最近２０年来的发展。对几类地质材料的本构模型,如各向同性硬化模型、多重屈服面模型、边界面模型作了简要的评述。      

Two non-probabilistic set-theoretical models for dynamic response and buckling failure measures of bars with unknown-but-bounded initial imperfections

This paper is concerned with the problem of comparison of two non-probabilistic set-theoretical models for dynamic response and buckling failure measures of bars with unknown-but-bounded initial imperfections. Two kinds of non-probabilistic set-theoretical models are convex models and interval analysis models. In convex models and interval analysis models, the uncertain quantities are considered to be unknown except that they belong to given sets in an appropriate vector space. In this case, all information about the dynamic response and buckling failure measures of bars is provided by the set of dynamic responses and buckling failure measures consistent with the constraints on the uncertain quantities. The dynamic response estimate is actually a set in appropriate response space rather than a single vector. The set estimate is the smallest calculable set which contains the uncertain dynamic response, but it is usually impractical to calculate this set. Two set estimate methods are developed which can calculate the time varying box or hyperrectangle, i.e. interval vector in the response space that contains the true dynamic response. Comparison between convex models and interval analysis models in mathematical proofs and numerical calculations shows that, under the condition of the outer enclosed ellipsoid from a hyperrectangle or an interval vector, the set dynamic response predicted by interval analysis models is smaller than that yielded by convex models; under the condition of the outer enclosed hyperrectangle or an interval vector from an ellipsoid, the dynamic response set calculated by convex models is smaller than that obtained by interval analysis models.     

Hysteretic models with stiffness and strength degradation in a mathematical programming format

In this paper, we present several hysteretic models formulated using an energy approach. In each case, the behavior of the model is completely described by specifying two scalar-valued functions—a stored energy function and a dissipation potential. Consequently, different types of mathematical programs arise in incremental non-linear analyses involving these models. It is relatively well-known how classical plasticity models can be described using an energy approach, and lead to mathematical programming problems. However, in this paper, we demonstrate that plasticity models with non-associated flow rules, softening plasticity or strength degradation models, and damage or stiffness degradation models can be represented in this framework as well. The energy approach serves to unify formulation and implementation of a broad class of hysteretic models. In addition, it helps motivate regularization strategies needed in optimization and inverse problems. The types of models considered in this paper are ones commonly applied in earthquake engineering. MATLAB implementations are included as online supplemental data with this paper to illustrate the conceptual simplicity of implementing models formulated using this approach.     

裂隙岩体中非饱和渗流与运移的概念模型及数值模拟

探讨了裂隙岩体中非饱和地下水渗流与溶质运移的几种概念模型的构造及数值模拟问题 ,如裂隙网络模型、连续体模型、等效连续体模型、双孔隙度 (单渗透率 )模型、双渗透率模型、多组份连续体模型等。在裂隙岩体中 ,非饱和地下水的渗流可能只局限于岩体中的岩石组份、或裂隙网络 ,也可能在裂隙和岩石中同时发生 ;对前一种情形只需考虑单一连续体中的流动 ,而后一种情况则需要包括地下水在岩石和裂隙之间的交换。岩体中的裂隙网络往往是溶质运移的主要通道 ;但当溶质在裂隙与岩石之间的渗透和扩散是重要的运移机制时 ,就需要考虑岩石与裂隙界面处的溶质交换。为了模拟岩石与裂隙之间地下水和溶质的交换 ,就需要了解岩石与裂隙之间相互作用的模式和范围 ,使得这类问题的概念模型较单一连续体模型多了一层不确定性、其数值模拟也变得更为困难。因为在实际问题中不易、甚至根本不能判别非饱和渗流的实际形态 ,具体采用哪种模型主要取决于分析的目的和对现场数据的掌握程度。不论哪种模型都会受到模型及参数不确定性的影响 ,因此必须考虑与其他辅助模型的比较.