共查询到20条相似文献，搜索用时 15 毫秒
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S. Toro P.J. Sánchez A.E. Huespe S.M. Giusti P.J. Blanco R.A. Feijóo 《International journal for numerical methods in engineering》2014,97(5):313-351
In the first part of this contribution, a brief theoretical revision of the mechanical and variational foundations of a Failure‐Oriented Multiscale Formulation devised for modeling failure in heterogeneous materials is described. The proposed model considers two well separated physical length scales, namely: (i) the macroscale where nucleation and evolution of a cohesive surface is considered as a medium to characterize the degradation phenomenon occurring at the lower length scale, and (ii) the microscale where some mechanical processes that lead to the material failure are taking place, such as strain localization, damage, shear band formation, and so on. These processes are modeled using the concept of Representative Volume Element (RVE). On the macroscale, the traction separation response, characterizing the mechanical behavior of the cohesive interface, is a result of the failure processes simulated in the microscale. The traction separation response is obtained by a particular homogenization technique applied on specific RVE sub‐domains. Standard, as well as, Non‐Standard boundary conditions are consistently derived in order to preserve objectivity of the homogenized response with respect to the micro‐cell size. In the second part of the paper, and as an original contribution, the detailed numerical implementation of the two‐scale model based on the finite element method is presented. Special attention is devoted to the topics, which are distinctive of the Failure‐Oriented Multiscale Formulation, such as: (i) the finite element technologies adopted in each scale along with their corresponding algorithmic expressions, (ii) the generalized treatment given to the kinematical boundary conditions in the RVE, and (iii) how these kinematical restrictions affect the capturing of macroscopic material instability modes and the posterior evolution of failure at the RVE level. Finally, a set of numerical simulations is performed in order to show the potentialities of the proposed methodology, as well as, to compare and validate the numerical solutions furnished by the two‐scale model with respect to a direct numerical simulation approach. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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金属-复合材料混合接头广泛存在于航空、船舶及汽车等领域,具有凹槽形貌的共固化金属-复合材料接头可保持复合材料结构的完整性和纤维的连续性。在被连接金属表面设计了±45°凹槽,评估了表面形貌对钢-玻璃纤维增强树脂复合材料(GFRP)接头胶接性能的影响,设计了单搭接拉伸剪切试验,验证胶接接头的剪切性能;在模拟中引入随机Weibull分布,定义内聚单元材料参数,结合矢量化用户材料(Vectorized user material,VUMAT)子程序模拟了接头的渐进失效过程,并建立±45°凹槽结构的代表性体积单元(Representative volume element,RVE)模型,分析了凹槽宽度和深度等参数对胶接接头的性能影响。研究表明,±45°凹槽结构可以显著提高钢-GFRP胶接接头的剪切强度,数值模拟强度和破坏模式与试验吻合;凹槽深度和宽度对结构胶接性能的影响显著,本文可为金属-复合材料接头的设计提供参考。 相似文献
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Q. Z. Xiao B. L. Karihaloo X. Y. Liu 《International journal for numerical methods in engineering》2007,69(12):2606-2635
In this paper, an incremental‐secant modulus iteration scheme using the extended/generalized finite element method (XFEM) is proposed for the simulation of cracking process in quasi‐brittle materials described by cohesive crack models whose softening law is composed of linear segments. The leading term of the displacement asymptotic field at the tip of a cohesive crack (which ensures a displacement discontinuity normal to the cohesive crack face) is used as the enrichment function in the XFEM. The opening component of the same field is also used as the initial guess opening profile of a newly extended cohesive segment in the simulation of cohesive crack propagation. A statically admissible stress recovery (SAR) technique is extended to cohesive cracks with special treatment of non‐homogeneous boundary tractions. The application of locally normalized co‐ordinates to eliminate possible ill‐conditioning of SAR, and the influence of different weight functions on SAR are also studied. Several mode I cracking problems in quasi‐brittle materials with linear and bilinear softening laws are analysed to demonstrate the usefulness of the proposed scheme, as well as the characteristics of global responses and local fields obtained numerically by the XFEM. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Amin Karamnejad Lambertus Johannes Sluys 《International journal for numerical methods in engineering》2016,107(7):580-602
A computational homogenization scheme is developed to model heterogeneous hyperelastic materials undergoing large deformations. The homogenization scheme is based on a so‐called computational continua formulation in which the macro‐scale model is assumed to consist of disjoint unit cells. This formulation adds no higher‐order boundary conditions and extra degrees of freedom to the problem. A computational procedure is presented to calculate the macroscopic quantities from the solution of the representative volume element boundary value problem. The proposed homogenization scheme is verified against a direct numerical simulation. It is also shown that the computational cost of the proposed model is lower than that of standard homogenization schemes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Asimina Manta Matthieu Gresil Constantinos Soutis 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(7):1441-1453
Important challenges are faced during the manufacturing of graphene nanoplatelet (GNP)/polymer composites, associated with material quality and how to eliminate or reduce fabrication‐induced defects in the effort to improve performance. In the present work, infrared thermography (IRT) is used to measure void content and map void distribution, formed during fabrication of GNP/epoxy nanocomposites. Taking into consideration the size of each pixel (~100 μm), this method enables the non‐destructive detection of flaws with a size of approximately 200 μm. Their effect on thermal conductivity of the nanocomposite is studied by a 3D multiscale finite element analysis. Generic and full‐field comparisons demonstrate a good agreement between measurements and numerical predictions, validating assumptions and simplifications made in the proposed model. 相似文献
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基于均匀化理论与有限元方法,针对双向连续纤维增强复合材料(CBFRC),建立了微观代表体积单元(RVE)模型,并预测了界面对CBFRC宏观等效力学性能的影响。在建立的RVE模型中,采用表面内聚力本构关系描述纤维/基体之间的界面。研究结果表明:不同界面刚度下,CBFRC中的基体发生不同形式的初始损伤。与界面断裂能相比,界面刚度和界面强度对CBFRC面外抗拉强度的影响较大,而对CBFRC面内抗拉强度的影响较小,且界面的存在会降低CBFRC整体的抗拉强度。随着纤维体积分数的增加,CBFRC面内的抗拉强度也随之急剧增加,但CBFRC的面外抗拉强度反而有减小的趋势。本文中所提出的方法能够简单有效地对实际复杂的三维纤维增强复合材料进行优化设计。 相似文献
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Representative volume: Existence and size determination 总被引：6，自引：0，他引：6
The concept of the representative volume element (RVE) is analysed in the present paper. For elastic materials the RVE exists and one can determine the size of the RVE. However, for other applications, such as the case of softening materials, the RVE may not exist. In the present work the RVE has been investigated for different stages of the material response, including pre- and post-peak loading regimes. Results were based on a statistical analysis of numerical experiments, where tests have been performed on a random heterogeneous material. 相似文献
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通过在代表性体积胞元(RVE)中嵌入内聚力面,建立了基于连续损伤力学的高抗冲聚苯乙烯多处银纹化细观机理模型。采用Quads准则作为内聚力面失效判据,引入材料刚度退化模型,利用非线性有限元方法研究了在单向拉伸载荷下高抗冲聚苯乙烯中银纹的萌生、生长和断裂过程及其规律。数值分析结果与实验中观察到的现象吻合较好,表明了本模型描述的内聚力面模拟银纹化过程的合理性。 相似文献
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It is well known that the structural performance of lightweight cellular solids depends greatly on the design of the representative volume element (RVE). In this article, an integrated topology optimization procedure is developed for the global stiffness maximization of 2D periodic and cyclic-symmetry cellular solids. A design variable linking technique and a superelement method are applied to model the structural periodicity and to reduce the computing time. In order to prevent the numerical instabilities associated with checkerboards in the design process, the quadratic perimeter constraint is used. Finally, the topology optimization problem is solved by the dual optimization algorithm. Several numerical examples are used to test the efficiency of the optimization procedure. Results show that the optimal topology of the RVE is not unique. It greatly depends on the size of the RVE. The computing efficiency can be greatly improved by means of the superelement technique. Also, for the optimal solution, the equivalent torsional rigidity has been compared with what is in the literature, to check the structural efficiency of the obtained topology. It has been observed that the current topology solution has the strongest rigidity when the same volume fraction of solid-phase materials is used. 相似文献
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In this paper, the mechanical response of incompressible particle-reinforced neo-Hookean composites (IPRNC) under general finite deformations is investigated numerically. Three-dimensional Representative Volume Element (RVE) models containing 27 non-overlapping identical randomly distributed spheres are created to represent neo-Hookean composites consisting of incompressible neo-Hookean elastomeric spheres embedded within another incompressible neo-Hookean elastomeric matrix. Four types of finite deformation (i.e., uniaxial tension, uniaxial compression, simple shear and general biaxial deformation) are simulated using the finite element method (FEM) and the RVE models with periodic boundary condition (PBC) enforced. The simulation results show that the overall mechanical response of the IPRNC can be well-predicted by another simple incompressible neo-Hookean model up to the deformation the FEM simulation can reach. It is also shown that the effective shear modulus of the IPRNC can be well-predicted as a function of both particle volume fraction and particle/matrix stiffness ratio, using the classical linear elastic estimation within the limit of current FEM software. 相似文献
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采用有限元-离散元耦合方法（FEM-DEM方法）,进行了氧化锆增韧氧化铝颗粒增强Fe45复合材料（ZrO2-Al2O3/Fe45）轴对称代表体元模型的拉伸断裂仿真分析。分析了FEM-DEM模型对单元尺寸的敏感性,结果表明采用,二阶实体单元加双零厚度内聚力单元的FEM-DEM模型降低了计算结果对单元尺寸的敏感性。ZrO2-Al2O3/Fe45复合材料拉伸断裂的模拟结果表明,颗粒形状对裂纹的扩展会产生较大影响,复合材料的开裂首先在垂直于拉力方向的界面处发生,界面裂纹扩展至基体应力集中处之后基体发生开裂,裂纹由开裂的界面和基体裂纹共同组成。 相似文献
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Jacob Fish Zheng Yuan 《International journal for numerical methods in engineering》2005,62(10):1341-1359
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Bin Sun 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(8):1837-1850
This paper addresses a novel continuum damage‐based method for simulating failure process of quasi‐brittle materials starting from local damage initiation to final fracture. In the developed method, the preset characteristic length field is used to evaluate damage instead of element, which is used to reduce the spurious sensitivity. In addition, damage is only updated in the most dangerous location at a time for considering stress redistribution due to damage evolution, which is used to simulate competitive fracture process. As cases study, representative numerical simulations of two benchmark tests are given to verify the performance of the developed continuum damage‐based method together with a used damage model. The simulation results of the crack paths for two concrete specimens obtained from the developed method matched well with the corresponding experimental results. The results show that the developed continuum damage‐based method is effective and can be used to simulate damage and fracture process of brittle or quasi‐brittle materials. And the simulation results based on the developed method depend only the preset characteristic length field and not grid mesh. 相似文献
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通过有限元方法研究了相同孔隙率下孔隙的分布、尺寸和形状等微观特征对碳纤维增强环氧树脂复合材料单向板横向拉伸强度的影响。首先使用Matlab对复合材料微观图像进行处理,提取孔隙的半径分布。然后通过C++编写多种孔隙随机分布算法,包括可以生成不同分布孔隙、不同尺寸孔隙以及不同形状孔隙的随机分布算法。最后通过Python参数化生成代表性体积单元（RVE）,用有限元方法研究相同孔隙率下孔隙的分布、尺寸和形状对碳纤维/环氧树脂复合材料单向板横向拉伸强度的影响。研究结果显示,孔隙率相同时,碳纤维/环氧树脂复合材料的孔隙形状对横向弹性模量的影响较大,孔隙尺寸和形状对横向拉伸强度有较大的影响。 相似文献
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In this paper, two brittle fracture problems are numerically simulated: the failure of a ceramic ring under centrifugal loading and crack branching in a PMMA strip. A three‐dimensional finite element package in which cohesive elements are dynamically inserted has been developed. The cohesive elements' strength is chosen to follow a modified weakest link Weibull distribution. The probability of introducing a weak cohesive element is set to increase with the cohesive element size. This reflects the physically based effect according to which larger elements are more likely to contain defects. The calculations illustrate how the area dependence of the Weibull model can be used to effectively address mesh dependency. On the other hand, regular Weibull distributions have failed to reduce mesh dependency for the examples shown in this paper. The ceramic ring calculations revealed that two distinct phenomena appear depending on the magnitude of the Weibull modulus. For low Weibull modulus, the fragmentation of the ring is dominated by heterogeneities. Whereas many cracks were generated, few of them could propagate to the outer surface. Monte Carlo simulations revealed that for highly heterogeneous rings, the number of small fragments was large and that few large fragments were generated. For high Weibull modulus, signifying that the ring is close to being homogeneous, the fragmentation process was very different. Monte Carlo simulations highlighted that a larger number of large fragments are generated due to crack branching. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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O. Lloberas‐Valls D.J. Rixen A. Simone L.J. Sluys 《International journal for numerical methods in engineering》2012,89(11):1337-1366
A hybrid multiscale framework is presented, which processes the material scales in a concurrent manner, borrowing features from hierarchical multiscale methods. The framework is used for the analysis of non‐linear heterogeneous materials and is capable of tackling strain localization and failure phenomena. Domain decomposition techniques, such as the ?nite element tearing and interconnecting method, are used to partition the material in a number of non‐overlapping domains and adaptive re?nement is performed at those domains that are affected by damage processes. This re?nement is performed in terms of material scale and ?nite element size. It is veri?ed that the results are independent of the chosen domain decomposition. Moreover, the multiscale analyses are validated with reference solutions obtained with a full ?ne‐scale solution procedure. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Gabriel Birck Antoniox Rinaldi Ignacio Iturrioz 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(12):2709-2724
The damage process in quasi‐brittle materials is characterized by the evolution of a micro‐crack field, followed by the joining of micro‐cracks, stress localization and crack instability. In network models, masses are lumped at nodal points which are interconnected by one‐dimensional elements with a bilinear constitutive relation, considering the energy consistency during the simulated process. In order to replicate the material imperfections, to render a realistic behaviour in damage localization, the model has not only random elastic and rupture properties, but also a geometric perturbation. In the present paper 2D plates with different levels of brittleness are simulated. The numerical results are presented in terms of global stress vs strain diagram, final network configuration, energy balance during the process and as geometric damage evolution. Therefore, the predictive potential of the lattice discrete element model to capture fracture processes in quasi‐brittle materials is demonstrated. 相似文献