95 resultados para Reuss


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Thesis (doctoral)--Friedrich-Alexanders-Universitat Erlangen.

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Thesis (doctoral)--Friedrichs-Universitat, Halle-Wittenberg.

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The overall elastic response of a bundle of coated cylinders is a major aspect of thermal, nuclear and automotive engineering designs. This paper extends the previous work on tubular bundles to assess the effect of coating material and thickness. A major contribution from this paper is determining the overall transverse elastic response of coated thick cylinders by extending the Michell stress function approach in conjunction with contact mechanics. Finite element results using contact elements pave the way for applying the contact stress boundary conditions for Michell analysis. Theoretical and finite element analyses overall give results consistent with the previous work, and the results also fall within the well-established Voigt-Reuss bounds. (C) 2013 Elsevier Ltd. All rights reserved.

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Computational models based on the phase-field method typically operate on a mesoscopic length scale and resolve structural changes of the material and furthermore provide valuable information about microstructure and mechanical property relations. An accurate calculation of the stresses and mechanical energy at the transition region is therefore indispensable. We derive a quantitative phase-field elasticity model based on force balance and Hadamard jump conditions at the interface. Comparing the simulated stress profiles calculated with Voigt/Taylor (Annalen der Physik 274(12):573, 1889), Reuss/Sachs (Z Angew Math Mech 9:49, 1929) and the proposed model with the theoretically predicted stress fields in a plate with a round inclusion under hydrostatic tension, we show the quantitative characteristics of the model. In order to validate the elastic contribution to the driving force for phase transition, we demonstrate the absence of excess energy, calculated by Durga et al. (Model Simul Mater Sci Eng 21(5):055018, 2013), in a one-dimensional equilibrium condition of serial and parallel material chains. To validate the driving force for systems with curved transition regions, we relate simulations to the Gibbs-Thompson equilibrium condition

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以爆炸排淤填石法为背景,对相关岩土介质的本构模型进行了探讨。分析认为,在以LS.DYNA 动态有限元分析程序对爆炸排淤填石法的数值模拟中,岩土介质不适于采用Mohr.Coulomb 模型,堆石体宜采用Drucker-Prager 模型,淤泥宜采用Prandtl-Reuss 模型;利用LS-DYNA 程序对淤泥的本构模型进行了验证和确认,计算表明:在形成爆炸空腔的高应变率阶段,淤泥表现为理想不可压缩流体的性质;在小药量小抵抗线条件下,在淤泥自重作用下的低应变率变形阶段,其粘性效应可以忽略不计。

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<正> 1.弹塑性有限元分析的基本公式根据von Mises 屈服准则和Prandtl-Reuss塑性流动律,可以导出弹塑性阶段的应力增量-全应变增量之间的本构关系:{dσ}=[D_(eP)]{dε} (1)其中{dσ}为应力增量列阵,{dε}为应变增量列阵,[D_(eP)]为弹塑性系数矩阵,它的表达式为:其中(?)为有效应力,[D_e]为弹性系数矩阵,H=(?)/((?)~p)为有效应力和有效塑性应变曲线的斜率.增量形式的平衡方程为:[K]{△u}={△P} (3)其中[K]为总体刚度矩阵,{△u}为位移增量列阵,{△P}为外载荷增量列阵.2.几种解法方程(3)是非线性的.对于一般问题,精确求解比较困难.目前,一般都用近似法来求解.下面介绍几种解法.

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第一章 绪论
1、1土的本构特性
1、2土本构模型的发展简史
1、3土本构模型的研究动向
2、1应力分析
第二章 连续介质力学的基本概念
2、1、1一点的应力状态、应力张量
2、1、2Cauchy公式、求和协定
2、1、3主应力
2、1、4偏应力
2、1、5八面体应力、纯剪应力、主剪应力
2、1、6应力空间、应力路径
2、1、7应力Mohr圆和应力Lode参数
2、2应变分析
2、2、1一点的应变状态、应变张量
2、2、2应变Cauchy公式
2、2、3主应变
2、2、4偏应变
2、2、5八面体应变、纯应变、主剪应变
2、2、6应变空间、应变路径
2、2、7应变率张量、应变增量张量
2、2、8应变Mohr圆
2、2、9有限应变
2、3基本方程
2、3、1连续方程
2、3、2运动微分方程
2、3、3协调方程
2、3、4能量方程
2、3、5本构方程
2、3、6边界条件和初始条件
第三章 经典塑性理论简述
3、1屈服准则
3、1、1初始屈服
3、1、2后继屈服
3、1、3几种屈服条件
3、2加载和卸载准则
3、2、1理想塑性材料的加载和卸载
3、2、2硬化材料的加载和卸载准则
3、3硬化规律
3、3、1各向同性硬化模型
3、3、2随动硬化模型
3、3、3混合硬化模型
3、4塑性公设
3、4、1Drucker塑性公设
3、4、2Ильюшин塑性公设
3、5流动规则
3、5、1塑性位势理论的基本概念
3、5、2流动规则
3、6塑性形变理论与塑性增量理论
3、6、1塑性形变理论
3、6、2塑性增量理论
第四章 土的弹性本构模型
4、1线弹性模型
4、1、1广义Hook定律
4、1、2正交各向异性线弹性体
4、1、3横观各向同性线弹性体
4、1、4各向同性线弹性体
4、2应变能和应变余能
4、3能量正定性与弹性材料稳定性
4、4具有割线模量的非线性弹性模型
4、4、1全量型应力—应变关系
4、4、2增量型应力—应变关系
4、5Cauchy弹性模型
4、5、1全量型Cauchy弹性模型应力—应变关系
4、5、2增量型Cauchy弹性模型应力—应变关系
4、6超弹性模型
4、6、1全量型超弹性模型应力—应变关系
4、6、2增量型超弹性模型的应力—应变关系
4、7次弹性模型
4、8结语
5、1本构关系的普遍表达式
第五章 土的弹性—理想塑性模型
5、2本构模型中材料常数的确定
5、3本构模型的数值计算
5、4Prandtl—Reuss模型
5、5Drucker—Prager模型
5、6Coulomb模型
6、1本构关系的普遍表达式
第六章 土的弹性—硬化塑性模型
6、2剑桥模型
6、3修正剑桥模型
6、4Lade—Duncan模型
6、5帽盖模型
6、5、1一般增量应力—应变关系与刚度矩阵的推导
6、5、2模型的拟合过程
6、5、3帽盖模型的数值计算
第七章 土的粘弹塑性模型
7、1土的流变学基本模型
7、2Maxwell体模型
7、3Kelvin体模型
7、4粘塑性体模型
7、5三元模型
7、6多元件组合模型
8、1弹塑性横观各向同性模型
第八章 土本构模型的近期发展
8、2非线性弹性—硬化塑性帽盖模型
8、3弹/粘塑性动态帽盖模型
8、4多重屈服面模型
8、5边界面模型
8、6内时本构方程
9、1基础的沉降与塌陷
第九章 土本构模型在工程中的应用
9、1、1具有不同材料常数的Drucker—Prager模型
9、1、2具有非相关联流动的Drucker—Prager模型
9、1、3具有相关流动的帽盖模型
9、2堤坝的非线性分析
9、3基坑开挖的非线性分析
9、3、1基坑竣工后状况
9、3、2边坡对地震过程的响应
9、3、3地震后的滑移
参考文献

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Upgrading two widely used standard plastics, polypropylene (PP) and high density polyethylene (HDPE), and generating a variety of useful engineering materials based on these blends have been the main objective of this study. Upgradation was effected by using nanomodifiers and/or fibrous modifiers. PP and HDPE were selected for modification due to their attractive inherent properties and wide spectrum of use. Blending is the engineered method of producing new materials with tailor made properties. It has the advantages of both the materials. PP has high tensile and flexural strength and the HDPE acts as an impact modifier in the resultant blend. Hence an optimized blend of PP and HDPE was selected as the matrix material for upgradation. Nanokaolinite clay and E-glass fibre were chosen for modifying PP/HDPE blend. As the first stage of the work, the mechanical, thermal, morphological, rheological, dynamic mechanical and crystallization characteristics of the polymer nanocomposites prepared with PP/HDPE blend and different surface modified nanokaolinite clay were analyzed. As the second stage of the work, the effect of simultaneous inclusion of nanokaolinite clay (both N100A and N100) and short glass fibres are investigated. The presence of nanofiller has increased the properties of hybrid composites to a greater extent than micro composites. As the last stage, micromechanical modeling of both nano and hybrid A composite is carried out to analyze the behavior of the composite under load bearing conditions. These theoretical analyses indicate that the polymer-nanoclay interfacial characteristics partially converge to a state of perfect interfacial bonding (Takayanagi model) with an iso-stress (Reuss IROM) response. In the case of hybrid composites the experimental data follows the trend of Halpin-Tsai model. This implies that matrix and filler experience varying amount of strain and interfacial adhesion between filler and matrix and also between the two fillers which play a vital role in determining the modulus of the hybrid composites.A significant observation from this study is that the requirement of higher fibre loading for efficient reinforcement of polymers can be substantially reduced by the presence of nanofiller together with much lower fibre content in the composite. Hybrid composites with both nanokaolinite clay and micron sized E-glass fibre as reinforcements in PP/HDPE matrix will generate a novel class of high performance, cost effective engineering material.

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Examination of samples of bryozoans from the south- eastern slope sediments of Australia ("Franklin" SLOPE Stations 6, 7), has revealed the presence of many specimens of several genera with species which have minute, rooted colony forms. Among these are new species of the genera Batopora Reuss (B. problematica) and Lacrimula Cook (L. affinis). The structure of colonies is briefly described. The family Batoporidae is considered to contain only these two genera, although they have relationships with the discoidal genus Orbitulipora, and similarities in colony form to the genera assigned to the Conescharellinidae.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The aim of this study was to determine the prevalence of anti-Leptospira spp. antibodies in dogs living in the urban area of the city of Ilheus, Bahia, Brazil using the microscopic agglutination test (MAT) to investigate 24 serovars. A semi-structured questionnaire was administered to dog owners to collect data about demography, husbandry and environmental factors. The prevalence of anti-Leptospira spp. antibodies in the population of 282 dogs was 7.1% (95% confidence interval: 4.4-10.7%). Serovar Copenhageni was the most prevalent, followed by serovars Bratislava, Canicola and Gryppotyphosa. No risk factor was detected with regard to demography (age, gender and breed), husbandry (Leptospira vaccinations, food and water exposure through their environment, hunting habits, contact with other animals and contact with rats) and environmental factors (sewage network, garbage collection, history of flooding, river proximity and wastelands). Despite the low prevalence found in this study, the seroprevalence of Leptospira spp. in healthy dogs in Ilheus indicates the presence of this agent in the environment, which may be a source of human infection. Knowledge of the serovars present in this environment is important for understanding the epidemiology of leptospirosis and establishing public health policies aimed at its control. (C) 2012 Elsevier B.V. All rights reserved.