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Spherical Harmonics Expansion of Fundamental Solutions and Their Derivatives for Homogeneous Elliptic Operators 齐次椭圆算子基本解的球谐展开及其导数
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-28 DOI: 10.1142/S1756973717400066
V. Gulizzi, I. Benedetti, A. Milazzo
In this work, a unified scheme for computing the fundamental solutions of a three-dimensional homogeneous elliptic partial differential operator is presented. The scheme is based on the Rayleigh expansion and on the Fourier representation of a homogeneous function. The scheme has the advantage of expressing the fundamental solutions and their derivatives up to the desired order without any term-by-term differentiation. Moreover, the coefficients of the series need to be computed only once, thus making the presented scheme attractive for numerical implementation. The scheme is employed to compute the fundamental solution of isotropic elasticity showing that the spherical harmonics expansions provide the exact expressions. Then, the accuracy of the scheme is assessed by computing the fundamental solutions of a generally anisotropic magneto-electro-elastic material.
在这项工作中,提出了一个计算三维齐次椭圆偏微分算子基本解的统一方案。该方案基于瑞利展开和齐次函数的傅立叶表示。该方案的优点是将基本解及其导数表达到所需的阶数,而不需要任何逐项微分。此外,级数的系数只需要计算一次,因此所提出的方案对数值实现具有吸引力。该格式用于计算各向同性弹性的基本解,表明球面谐波展开提供了精确的表达式。然后,通过计算一般各向异性磁电弹性材料的基本解来评估该方案的精度。
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引用次数: 1
Multi-Scaling Homogenization Process for Nodular Cast Iron Using BEM 基于边界元法的球墨铸铁多尺度均匀化工艺
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-28 DOI: 10.1142/S1756973717400054
Adrián Alberto Betancur Arroyave, C. Anflor
In this work, a multi-scaling homogenization process using boundary element formulation (BEM) for modeling a two-dimensional multi-phase microstructure containing irregular’s inclusions is presented. The BEM is very attractive for multiscale modeling tools for heterogeneous materials. In this approach, the iterative inhomogeneity discretization of the external boundary is disregarded, leading to a computational low cost. This approach was used for solving the elastic problem of a representative volume element (RVE) and the field theory medium. The main goal relies on finding the effective properties of micro-heterogeneous materials within a homogeneous and orthotropic matrix. Expressions for evaluating the effective properties under Plane Stress (PT) for orthotropic materials were also presented. Generally, the numerical models consider the graphite nodules as voids for GGG-40 and the roundness is close circular geometry. In this sense, a nodular cast iron GGG-40 microgram was obtained by X-ray computed t...
在这项工作中,提出了一种使用边界元公式(BEM)来模拟含不规则夹杂物的二维多相微观结构的多尺度均匀化过程。边界元法是一种非常有吸引力的多尺度非均质材料建模工具。该方法不考虑外边界的迭代非均匀性离散化,计算成本低。将该方法用于求解具有代表性的体积元(RVE)和场论介质的弹性问题。主要目标依赖于在均匀和正交各向异性矩阵中发现微非均质材料的有效性质。给出了正交异性材料在平面应力作用下有效性能的计算表达式。通常,数值模型将石墨结核视为GGG-40的空洞,圆度为接近圆形的几何形状。在这个意义上,通过x射线计算得到了一个球状铸铁GGG-40微克。
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引用次数: 0
Spectral BEM for the Analysis of Wave Propagation and Fracture Mechanics 用于波传播和断裂力学分析的频谱边界元法
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-28 DOI: 10.1142/S1756973717400078
Jun Li, Z. S. Khodaei, M. Aliabadi
This paper presents a spectral boundary element formulation for analysis of structures subjected to dynamic loading. Two types of spectral elements based on Lobatto polynomials and Legendre polynomials are used. Two-dimensional analyses of elastic wave propagation in solids with and without cracks are carried out in the Laplace frequency domain with both conventional BEM and the spectral BEM. By imposing the requirement of the same level of accuracy, it was found that the use of spectral elements, compared with conventional quadratic elements, reduced the total number of nodes required for modeling high-frequency wave propagation. Benchmark examples included a simple one-dimensional bar for which analytical solution is available and a more complex crack problem where stress intensity factors were evaluated. Special crack tip elements are developed for the first time for the spectral elements to accurately model the crack tip fields. Although more integration points were used for the integrals associated w...
本文提出了一种用于分析动态载荷作用下结构的谱边界元公式。使用了基于Lobatto多项式和Legendre多项式的两种类型的谱元素。利用传统边界元法和谱边界元法,在拉普拉斯频域中对有裂纹和无裂纹固体中弹性波的传播进行了二维分析。通过施加相同精度水平的要求,发现与传统的二次元素相比,频谱元素的使用减少了建模高频波传播所需的节点总数。基准示例包括一个简单的一维杆,可以获得解析解,以及一个更复杂的裂纹问题,其中评估了应力强度因子。首次为谱元开发了特殊的裂纹尖端单元,以精确地模拟裂纹尖端场。尽管使用了更多的积分点来进行与w。。。
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引用次数: 5
Multi-Fidelity Modeling-Based Structural Reliability Analysis with the Boundary Element Method 基于多保真度建模的结构可靠性边界元分析
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-28 DOI: 10.1142/S1756973717400017
L. Morse, Z. S. Khodaei, M. H. Aliabadi
In this work, a method for the application of multi-fidelity modeling to the reliability analysis of 2D elastostatic structures using the boundary element method (BEM) is proposed. Reliability analyses were carried out on a rectangular plate with a center circular hole subjected to uniaxial tension using Monte Carlo simulations (MCS), the first-order reliability method (FORM), and the second-order reliability method (SORM). Two BEM models were investigated, a low-fidelity model (LFM) of 20 elements and a high-fidelity model (HFM) of 100 elements. The response of these models at several design points was used to create multi-fidelity models (MFMs) utilizing second-order polynomial response surfaces and their reliability, alongside that of the LFM and the HFM, was evaluated. Results show that the MFMs that directly called the LFM were significantly superior in terms of accuracy to the LFM, achieving very similar levels of accuracy to the HFM, while also being of similar computational cost to the LFM. These ...
在这项工作中,提出了一种使用边界元法(BEM)将高保真度建模应用于二维弹静力结构可靠性分析的方法。采用蒙特卡罗模拟(MCS)、一阶可靠度法(FORM)和二阶可靠度方法(SORM)对具有中心圆孔的矩形板进行了单轴拉伸的可靠性分析。研究了两个边界元模型,一个是20个元素的低保真度模型(LFM),另一个是100个元素的高保真度模型(HFM)。这些模型在几个设计点的响应被用于利用二阶多项式响应面创建高保真度模型(MFM),并对其可靠性以及LFM和HFM的可靠性进行了评估。结果表明,直接称为LFM的MFM在精度方面明显优于LFM,实现了与HFM非常相似的精度水平,同时也具有与LFM相似的计算成本。这些
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引用次数: 10
An Efficient Hybrid Implementation of MLPG Method MLPG方法的高效混合实现
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-28 DOI: 10.1142/S1756973717400029
M. Barbosa, E. Fontes, J. Telles, W. J. Santos
The computational implementation of moving least squares (MLS) shape functions is an important step to consider in some versions of the meshless local Petrov–Galerkin (MLPG) method for a variety of two-dimensional engineering problems. Here, the usage of conventional Gaussian quadrature in the MLPG may require an excessive number integration points to achieve acceptable accuracy. In addition, since for each integration point a search for nearby points contributing to the construction of the MLS shape functions is required, considerable increase in computational cost is often observed. Herein, an efficient hybrid implementation of CPU and GPU is proposed to accelerate the construction of MLS shape functions for MLPG. To this end, a new K-d-Tree (K-dimensional tree)-based data structure is introduced in order to accelerate the calculations involving computational geometry formulas such as MLS. The results are compared for implementations in CPU and CPU+GPU using K-d-Tree with the traditional algorithm of br...
在一些无网格局部Petrov-Galerkin (MLPG)方法中,移动最小二乘(MLS)形状函数的计算实现是考虑各种二维工程问题的重要步骤。在这里,在MLPG中使用传统的高斯正交可能需要过多的积分点才能达到可接受的精度。此外,由于对于每个积分点都需要搜索有助于构造MLS形状函数的附近点,因此经常观察到计算成本的显著增加。为此,提出了一种高效的CPU和GPU混合实现,以加快MLPG中MLS形状函数的构建。为此,引入了一种新的基于K-d-Tree (k维树)的数据结构,以加速涉及计算几何公式(如MLS)的计算。比较了K-d-Tree算法在CPU和CPU+GPU上的实现结果。
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引用次数: 2
Finite Element Analysis of Cylindrical Inclusions in Polycrystalline Nickel Alloys 多晶镍合金中圆柱形夹杂物的有限元分析
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-12-26 DOI: 10.1142/S1756973718500038
E. Bonifaz, A. Alban, A. Czekanski
Inspired by nanotubes, a 3D finite element model was developed to simulate the influence of cylindrical inclusions on the polycrystalline mechanical behavior of Nickel alloys. A dislocation based strain hardening model, constructed in the so-called Kocks–Mecking framework, is used as the main strategy for the constitutive modeling of individual bulk grains. To determine the influence of the inclusions distribution, the direction of applied load and the size of the matrix phase on the inelastic stress–strain distribution, the digital microstructure code DREAM.3D was coupled to ABAQUS[Formula: see text] finite element code through a MatLab[Formula: see text] program. Four affordable computational representative volume elements (RVEs) meshes of two different edge sizes and two different inclusion distributions were tested to investigate the relation between micro and macro deformation and stress variables. The virtual specimens, subjected to continuous monotonic strain loading conditions, were constrained with random periodic boundary conditions. The difference in crystallographic orientation, which evolves in the process of straining, and the incompatibility of deformation between neighboring grains were accounted for by the introduction of single crystal averaged Taylor factors, single crystal Young’s modulus, single phase elastic modulus and the evolution of geometrically necessary dislocation density. The effects of single crystal Young’s modulus, inclusion distribution and direction of the applied load upon the aggregate local response are clearly observed. Results demonstrate a strong dependence of flow stress and plastic strain on phase type, Young’s modulus values and direction of the applied load, but slightly on matrix grain size. The stress–strain curve extension and the variation in the elastic limit of the individual inclusions depend on the inclusion-matrix Young’s modulus difference and applied load direction. The difference in curve extension and the difference in elastic limit decrease as the Young’s modulus of the single crystal inclusion approach the Young’s modulus of the matrix majoritary phase, while the resistance to flow increases when the applied load is perpendicular to the inclusion longitudinal axis.
受纳米管的启发,建立了一个三维有限元模型来模拟圆柱形夹杂物对镍合金多晶力学行为的影响。在所谓的Kocks-Mecking框架中构建的基于位错的应变硬化模型被用作单个大块晶粒本构建模的主要策略。为了确定夹杂物分布、施加载荷的方向和基体相的尺寸对非弹性应力-应变分布的影响,通过MatLab程序将数字微观结构代码DREAM.3D与ABAQUS有限元代码[公式:见正文]耦合。测试了四个具有两种不同边缘尺寸和两种不同夹杂物分布的可负担计算代表性体积单元(RVE)网格,以研究微观和宏观变形与应力变量之间的关系。虚拟试件在连续单调应变加载条件下,受到随机周期边界条件的约束。通过引入单晶平均泰勒因子、单晶杨氏模量、单相弹性模量和几何必要位错密度的演变,解释了在应变过程中演变的结晶取向的差异以及相邻晶粒之间变形的不相容性。可以清楚地观察到单晶杨氏模量、夹杂物分布和施加载荷的方向对骨料局部响应的影响。结果表明,流动应力和塑性应变强烈依赖于相类型、杨氏模量值和施加载荷的方向,但略依赖于基体晶粒尺寸。单个夹杂物的应力-应变曲线延伸和弹性极限的变化取决于夹杂物基体的杨氏模量差和施加的载荷方向。当单晶夹杂物的杨氏模量接近基质主相的杨氏模量时,曲线延伸的差异和弹性极限的差异减小,而当施加的载荷垂直于夹杂物纵轴时,流动阻力增加。
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引用次数: 1
An Advanced Discrete Model with Applications in Medical Science 一种先进的离散模型及其在医学中的应用
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-11-14 DOI: 10.1142/S1756973718500014
B. Para, T. R. Jan
In this paper, we introduce a new discrete model by compounding two parameter discrete Weibull distribution with Beta distribution of first kind. The proposed model can be nested to different compound distributions on specific parameter settings. The model is a good competitive for zero-inflated models. In addition, we present the basic properties of the new distribution and discuss unimodality, failure rate functions and index of dispersion. Finally, the model is examined with real-life count data from medical sciences to investigate the suitability of the proposed model.
本文将两参数离散威布尔分布与第一类Beta分布复合,引入一种新的离散模型。该模型可以在特定参数设置下嵌套到不同的复合分布中。该模型是一个很好的竞争零膨胀模型。此外,我们给出了新分布的基本性质,并讨论了单峰性、故障率函数和色散指数。最后,该模型与现实生活中来自医学科学的计数数据进行检验,以调查所提出的模型的适用性。
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引用次数: 3
Free Vibration Analysis of Carbon Fiber-Carbon Nanotube-Polymer Matrix Composite Plates by a Finite Element-Based Multi-Scale Modeling Approach 基于有限元多尺度建模的碳纤维-碳纳米管-聚合物基复合材料板自由振动分析
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-11-09 DOI: 10.1142/S1756973718500026
M. Ahmadi, R. Ansari, H. Rouhi
The vibrational behavior of polymer matrix nanocomposite plates reinforced with carbon fibers (CFs) and carbon nanotubes (CNTs) is studied using the finite element method based on a multi-scale modeling approach. The influences of nano- and micro-scale are coupled through a two-step procedure. First, CNTs are dispersed into the polymer matrix. In the selected representative volume element (RVE), interphase due to chemical interaction between CNT and polymer matrix is considered. Also, the state of dispersion of CNTs into the matrix is assumed to be random. In the second step, CFs are randomly distributed in the reinforced polymer with CNTs. The reinforcement is carried out for various volume fractions of CFs and CNTs. Two three-dimensional models including the brick and shell ones are used to generate the results. Moreover, the analysis is presented for square plates under different types of boundary conditions. The effect of nanocomposite thickness on its vibrational response is also investigated.
采用基于多尺度建模方法的有限元方法研究了碳纤维和碳纳米管增强聚合物基纳米复合板的振动行为。纳米尺度和微米尺度的影响通过两步程序耦合。首先,将CNT分散到聚合物基体中。在选定的代表性体积元素(RVE)中,考虑了CNT和聚合物基体之间化学相互作用引起的界面。此外,假定CNT分散到基质中的状态是随机的。在第二步骤中,CF随机分布在具有CNT的增强聚合物中。对CF和CNT的不同体积分数进行增强。使用两个三维模型,包括砖和壳模型来生成结果。此外,还对不同类型边界条件下的方形板进行了分析。还研究了纳米复合材料厚度对其振动响应的影响。
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引用次数: 7
Stress Wave Propagation in Cracked Geological Solids Using Finite Difference Scheme 应力波在有裂纹地质实体中的有限差分传播
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-09-21 DOI: 10.1142/S1756973717500093
P. Kakavas, Nicos A. Kalapodis
The aim of this study is the numerical computation of the wave propagation in crack geological solids. The finite difference method was applied to solve the differential equations involved in the problem. Since the problem is symmetric, we prefer to use this technique instead of the finite element method and/or boundary elements technique. A comparison of the numerical results with analytical solutions is provided.
本研究的目的是对裂纹地质固体中的波传播进行数值计算。应用有限差分法求解了该问题所涉及的微分方程。由于问题是对称的,我们更喜欢使用这种技术,而不是有限元方法和/或边界元技术。给出了数值结果与解析解的比较。
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引用次数: 0
Symmetrical or Non-Symmetrical Debonds at Fiber-Matrix Interfaces: A Study by BEM and Finite Fracture Mechanics on Elastic Interfaces 纤维-基体界面的对称或非对称粘结:边界元法和弹性界面有限断裂力学的研究
IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS Pub Date : 2017-09-01 DOI: 10.1142/S175697371740008X
M. Muñoz-Reja, L. Távara, V. Mantič
A recently proposed criterion is used to study the behavior of debonds produced at a fiber–matrix interface. The criterion is based on the Linear Elastic–(Perfectly) Brittle Interface Model (LEBIM) combined with a Finite Fracture Mechanics (FFM) approach, where the stress and energy criteria are suitably coupled. Special attention is given to the discussion about the symmetry of the debond onset and growth in an isolated single fiber specimen under uniaxial transverse tension. A common composite material system, glass fiber–epoxy matrix, is considered. The present methodology uses a two-dimensional (2D) Boundary Element Method (BEM) code to carry out the analysis of interface failure. The present results show that a non-symmetrical interface crack configuration (debonds at one side only) is produced by a lower critical remote load than the symmetrical case (debonds at both sides). Thus, the non-symmetrical solution is the preferred one, which agrees with the experimental evidences found in the literature.
最近提出的一个标准用于研究纤维-基体界面上产生的脱粘行为。该标准基于线性弹性-(完美)脆性界面模型(LEBIM)和有限断裂力学(FFM)方法,其中应力和能量标准适当耦合。特别注意讨论了单纤维试样在单轴横向拉伸下脱粘开始和生长的对称性。考虑了一种常见的复合材料体系,玻璃纤维-环氧树脂基体。本方法使用二维(2D)边界元法(BEM)代码来进行界面失效的分析。目前的结果表明,非对称界面裂纹形态(仅一侧脱胶)是由比对称情况(两侧脱胶)更低的临界远程载荷产生的。因此,非对称解是优选的解,这与文献中的实验证据一致。
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引用次数: 3
期刊
Journal of Multiscale Modelling
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