薄膜非线性撕裂三种弯曲模型的解答及讨论

针对薄膜非线性撕裂的弯曲模型,引入了3种表征薄膜撕裂过程的双参数准则.这3种表征分别为:(1)界面断裂韧度和分离应力;(2)界面断裂韧度和薄膜的裂尖转角;(3)界面断裂韧度和薄膜在裂尖的临界Mises等效应变.从3种双参数准则入手,分析并给出了针对上述各准则的薄膜非线性撕裂问题的解答.通过分析和比较,建立弯曲模型解答与严格平面应变弹塑性分析解答之间的关联.

Modeling Nonlinear Peeling of Ductile Thin Films-Critical Assessment of Analytical Bending Models Using FE Simulations

Three analytical double-parameter criteria based on a bending model and a two-dimensional finite element analysis model are presented for the modeling of ductile thin film undergoing a nonlinear peeling process. The bending model is based on different governing parameters: (1) the interfacial fracture toughness and the separation strength, (2) the interfacial fracture toughness and the crack tip slope angle, and (3) the interfacial fracture toughness and the critical Mises effective strain of the delaminated thin film at the crack tip. Thin film nonlinear peeling under steady-state condition is solved with the different governing parameters. In addition, the peeling test problem is simulated by using the elastic-plastic finite element analysis model. A critical assessment of the three analytical bending models is made by comparison of the bending model solutions with the finite element analysis model solutions. Furthermore, through analyses and comparisons for solutions based on both the bending model and the finite element analysis model, some connections between the bending model and the finite element analysis model are developed. Moreover, in the present research, the effect of different selections for cohesive zone shape on the ductile film peeling solutions is discussed.

Mode I crack growth resistance of metallic foams

A Dugdale-type cohesive zone model is used to predict the mode I crack growth resistance (R-curve) of metallic foams, with the fracture process characterized by an idealized traction-separation law that relates the crack surface traction to crack opening displacement. A quadratic yield function, involving the von Mises effective stress and mean stress, is used to account for the plastic compressibility of metallic foams. Finite element calculations are performed for the crack growth resistance under small scale yielding and small scale bridging in plane strain, with K-field boundary conditions. The following effects upon the fracture process are quantified: material hardening, bridging strength, T-stress (the non-singular stress acting parallel to the crack plane), and the shape of yield surface. To study the failure behaviour and notch sensitivity of metallic foams in the presence of large scale yielding, a study is made for panels embedded with either a centre-crack or an open hole and subjected to tensile stressing. For the centre-cracked panel, a transition crack size is predicted for which the fracture response switches from net section yielding to elastic-brittle fracture. Likewise, for a panel containing a centre-hole, a transition hole diameter exists for which the fracture response switches from net section yielding to a local maximum stress criterion at the edge of the hole.

Las bodas de Camacho y una relectura del mito de D. Quijote desde versiones operísticas del episodio cervantino

Resumen: El mundo de la ópera es un campo de permanentes ebulliciones aunque todavía se le endilguen acusaciones falsas de inmovilidad y anquilosamiento. No cesan de componerse obras con lenguajes innovadores sobre temáticas inéditas. Se experimenta —a veces, abusivamente— con puestas en escena heterodoxas, y las investigaciones hallan partituras perdidas o relegadas que hacen variar, permanentemente, el mapa del canon del género. En el presente trabajo, se analiza un caso-testigo de estas continuas mutaciones. Es la recuperación entre 2006 y 2011 de tres óperas compuestas entre 1760 y 1830 sobre el episodio del Quijote referido a las bodas de Camacho. Reviste particular relevancia, a mi juicio, porque no solo ha aumentado el caudal del repertorio operístico conocido sino que por sus relaciones con la literatura nos alerta a los estudiosos de ésta acerca de fenómenos que no podemos dejar de considerar. Ellos atañen a la recepción de la obra cervantina y al mito de D. Quijote, mito cuya expansión sobrepasa, ampliamente, al público lector de la obra. Nos conduce, por lo tanto, más allá de lo literario, a las complejidades de la construcción del imaginario cultural.

Anuario de la Facultad de Ciencias Económicas del Rosario, Vol. 10, 2014

Contenido: Contabilidad y estados contables : implicancias del nuevo ordenamiento del Código Civil y Comercial de la Nación / Guillermo Boggino ; Clide Palacios -- De la inconmensurabilidad a la multimodalidad, un camino sin cisuras / Francisco Casiello ; Luis Herrera -- Ejercicios con la relación entre crecimiento económico y gasto público / Juan Sebastián Landoni -- La vigencia de las ideas de Ludwig Von Mises, para la interpretación de los problemas de Latinoamérica, en la actualidad / Guillermo Covernton -- Servicio de consulta / Patricia Constantini -- La inserción laboral de jóvenes profesionales con discapacidad en el marco de la responsabilidad social empresaria y los indicadores no financieros en la gestión sostenible / Analía Cinalli -- Una nueva menesterosidad para habitar la enseñanza de la filosofía / María del Huerto Revaz -- Los activos intangibles : una incertidumbre en la información contable / Vanesa Vazzano -- El modelo de gestión estratégica de recursos humanos como herramienta de desarrollo, crecimiento, eficiencia y modernización de la gestión pública / Hilda Delaux -- Estudio de la estabilidad de una variante del modelo de la telaraña / José Semitiel ; Angélica Arnulfo ; Cintia Cianciardo -- Microcréditos : tensión social ente destinatarios y tasa de interés / Germán Messina

Phase Transformation Accommodated Plasticity In Nanocrystalline Nickel

Based on detailed x-ray diffraction and transmission electron microscopy we have found body-centered-cubic (bcc) Ni upon room-temperature rolling of nanocrystalline (nc) face-centered-cubic (fcc) Ni. The bcc phase forms via the Kurdjumov-Sachs (KS) martensitic transformation mechanism when the von Mises equivalent strain exceeds similar to 0.3, much higher than accessible in tensile testing. The fcc and bcc phases keep either the KS or the Nishiyama-Wasserman orientation relationship. Our results provide insights into the deformation physics in nc Ni, namely, the fcc-to-bcc phase transformation can also accommodate plasticity at large plastic strains. (C) 2008 American Institute of Physics.

La burbuja inmobiliaria americana

Resumen: Axel Leijonhufvud, economista reconocido internacionalmente por sus trabajos sobre la literatura de John Maynard Keynes y el keynesianismo (Leijonhufvud, 1968), ofreció su lectura de la crisis subprime de 2008, reconociendo que la misma encaja más con la teoría austríaca del ciclo económico de Ludwig von Mises y Friedrich Hayek, que con el marco teórico keynesiano. En este artículo ofrecemos evidencia para tal afirmación.

对塑性理论中几个有争议问题的讨论

<正> 1.引言屈服面的形状及其随变形历史的演化规律,在固体材料塑性变形理论的研究中占有十分重要的地位.引人注目的是目前所得到的屈服面试验数据中出现了一些不尽一致甚至相互矛盾的现象.对于初始屈服面,继 Tresca 的最大剪应力准则、Mises 的最大形变能准则之后,Ишлинский(1940)提出最大偏应力

弹塑性有限元的一些解法比较

<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.

Study of three elastic-plastic constitutive models by non-proportional finite deformations of OFHC copper

Experimental stress-strain data of OFHC copper first under torsion to 13% and then under torsion-tension to about 10% are used to study the characteristics of three elastic-plastic constitutive models: Chaboche's super-positional nonlinear model, Dafalias and Popov's two surface model and Watanabe and Atluri's version of the endochronic model. The three models, originally oriented for infinitesimal deformation, have been extended for finite deformation. The results show (a) the Mises-type yield surface used in the three models brings about significant departure of the predictions from the experimental data; (b) Chaboche's and Dafalias' models are easier than Watanabe and Atluri's model in determining the material parameters in them, and (c) Chaboche's and Watanabe & Atluri's models produce almost the same prediction to the data, while Dafalias' model cannot accurately predict the plastic deformations when a loading path changes in its direction. Copyright (C) 1996 Elsevier Science Ltd

水中悬浮隧道在冲击载荷作用下的计算模型与数值模拟

建立了水中悬浮隧道在冲击载荷作用下的简化计算模型。用等效质量法将圆柱壳分布质量折算成冲击点处的集中质量,模型中考虑流体附加质量和系统阻尼的影响。根据碰撞过程中的动量守恒、变形过程中的能量守恒以及结构的位移与内力关系,得到问题的解析解。为验证解析解,在ANSYS/LS-DYNA中建立了动态冲击有限元分析模型。通过算例分别考察了在忽略和考虑流体附加质量两种情况下,冲击点位置和冲击速度对冲击点处最大径向位移的影响,将解析解与数值解进行对比,结果吻合较好。然后采用数值模拟方法得到了系统阻尼对计算结果的影响规律。数值模拟过程中还可以得到冲击点处的最大Mises应力。

压力容器和管道随机局部减薄的有限元分析

按照压力容器和管道随机局部减薄后的厚度分布的随机性和各个部位的弹性模量的随机性,将有限元模型中的单元厚度和材料弹性模量处理成指定的随机分布,来模拟实际结构中的厚度和弹性模量的随机性。利用通用有限元软件对建立的受内压作用局部随机减薄的压力容器和管道的有限元模型的求解,获得了该随机模型的Mises应力分布特征。通过对弹性模量,减薄程度等随机量关于应力分布的敏感性分析,为该类结构的可靠性评估提供了力学依据。本文方法适用于许多结构随机性的模拟,也对确定性评定方法的一个补充和完善。

Ahozkotasunaren irakaskuntza bigarren hezkuntzako testuliburuetan

[EN]Traditionally writing skills have been given priority in language teaching and so, oral skills have been put aside. However, during the last years many voices have asserted the importance of oral skills. Therefore, they claim that oral language teaching must be emphasized at school. Also, the necessity of strengthening oral language is shown in the new curriculum. Nevertheless, those intentions are reflected in very different ways in textbooks. In this work we have looked into the treatment that oral language is given in teaching materials because, in our opinion, textbooks are one of the most important tools for teachers. The facts show that the importance given to oral language and the exercises and tools needed to work that skill are very different from one publishing house to another. Besides, we have confirmed that all the textbooks don’t satisfy the requirements proposed in the Basque official curriculum (e.g. didactic sequences) or that the approach to the text or the way to work with it are not always what they should be. Therefore, it is obvious that we have still a long way in the field of oral language and specially in the way of teaching oral skills

Alegia klasikoak euskaraz: Isopeteko, La Fontaineren eta Samaniegoren alegien berridazketen azterketa

521 p.

Modelagem numérica de elementos tracionados em aço inoxidável com parafusos defasados

Atualmente, a utilização do aço inoxidável em elementos estruturais é considerada uma solução cara para os problemas da engenharia estrutural. Todavia, mudanças de atitudes dentro da construção civil, uma transição global para um desenvolvimento sustentável e redução em impactos ambientais têm seguramente provocado um aumento na utilização do aço inoxidável. As normas de projeto de aço inoxidável atuais são, em grande parte, baseadas em analogias assumidas com o comportamento de estruturas desenvolvidas com aço carbono. Todavia, o aço inoxidável apresenta quatro curvas não-lineares tensão versus deformação (tensão e compressão, paralela e perpendicular a laminação do material), sem patamar de escoamento e região de encruamento claramente definidos, modificando assim, o comportamento global das estruturas que o utilizam. Em elementos estruturais submetidos a forças axiais de tração, a ruptura da seção líquida representa um dos estados limites últimos a serem verificados. Com o objetivo de se avaliar a resistência a tração de elementos estruturais aparafusados em aço inoxidável S304, este trabalho apresenta um modelo numérico baseado no método dos elementos finitos através do programa Ansys (versão 11). A não-linearidade do material foi considerada através do critério de plastificação de Von Mises e curvas tensão versus deformação verdadeira. A não-linearidade geométrica foi introduzida no modelo através da Formulação de Lagrange atualizado. O modelo numérico foi calibrado com resultados experimentais obtidos em ensaios de laboratório, a partir de ligações aparafusadas alternadas rígidas, onde não se ocorre nenhuma rotação entre os membros, transferindo nenhum momento fletor, apenas esforço normal e cisalhante.