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Special Column on Multiscale Stochastic Finite Element Method

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 105-106 doi: 10.1007/s11709-015-0297-7

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Multiscale stochastic finite element method on random field modeling of geotechnical problems – a fast

Xi F. XU

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 107-113 doi: 10.1007/s11709-014-0268-4

摘要： The Green-function-based multiscale stochastic finite element method (MSFEM) has been formulated based on the stochastic variational principle. In this study a fast computing procedure based on the MSFEM is developed to solve random field geotechnical problems with a typical coefficient of variance less than 1. A unique fast computing advantage of the procedure enables computation performed only on those locations of interest, therefore saving a lot of computation. The numerical example on soil settlement shows that the procedure achieves significant computing efficiency compared with Monte Carlo method.

关键词： multiscale finite element settlement perturbation random field geotechnical

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Multiscale computation on feedforward neural network and recurrent neural network

Bin LI, Xiaoying ZHUANG

《结构与土木工程前沿（英文）》 2020年第14卷第6期页码 1285-1298 doi: 10.1007/s11709-020-0691-7

摘要： Homogenization methods can be used to predict the effective macroscopic properties of materials that are heterogenous at micro- or fine-scale. Among existing methods for homogenization, computational homogenization is widely used in multiscale analyses of structures and materials. Conventional computational homogenization suffers from long computing times, which substantially limits its application in analyzing engineering problems. The neural networks can be used to construct fully decoupled approaches in nonlinear multiscale methods by mapping macroscopic loading and microscopic response. Computational homogenization methods for nonlinear material and implementation of offline multiscale computation are studied to generate data set. This article intends to model the multiscale constitution using feedforward neural network (FNN) and recurrent neural network (RNN), and appropriate set of loading paths are selected to effectively predict the materials behavior along unknown paths. Applications to two-dimensional multiscale analysis are tested and discussed in detail.

关键词： multiscale method constitutive model feedforward neural network recurrent neural network

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Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer

Xinyu HUI, Yingjie XU, Weihong ZHANG

《机械工程前沿（英文）》 2020年第15卷第3期页码 475-483 doi: 10.1007/s11465-020-0590-6

摘要： In this study, the micro curing residual stresses of carbon fiber-reinforced thermoset polymer (CFRP) composites are evaluated using a multiscale modeling method. A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure. Meanwhile, a representative volume element model of the composites is established at the microscale level. By introducing the information from the macroscale perspective, the curing residual stresses are calculated using the microscale model. The evolution of curing residual stresses reveals the interaction mechanism of fiber, matrix, and interphase period during the curing process. Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber. Furthermore, the curing residual stresses at different locations in the composites are calculated and discussed. Simulation results provide an important guideline for the analysis and design of CFRP composite structures.

关键词： CFRP curing residual stress multiscale modeling finite element method

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Topology optimization based on reduction methods with applications to multiscale design and additive

Emmanuel TROMME, Atsushi KAWAMOTO, James K. GUEST

《机械工程前沿（英文）》 2020年第15卷第1期页码 151-165 doi: 10.1007/s11465-019-0564-8

摘要： Advanced manufacturing processes such as additive manufacturing offer now the capability to control material placement at unprecedented length scales and thereby dramatically open up the design space. This includes the considerations of new component topologies as well as the architecture of material within a topology offering new paths to creating lighter and more efficient structures. Topology optimization is an ideal tool for navigating this multiscale design problem and leveraging the capabilities of advanced manufacturing technologies. However, the resulting design problem is computationally challenging as very fine discretizations are needed to capture all micro-structural details. In this paper, a method based on reduction techniques is proposed to perform efficiently topology optimization at multiple scales. This method solves the design problem without length scale separation, i.e., without iterating between the two scales. Ergo, connectivity between space-varying micro-structures is naturally ensured. Several design problems for various types of micro-structural periodicity are performed to illustrate the method, including applications to infill patterns in additive manufacturing.

关键词： multiscale topology optimization micro-structure additive manufacturing reduction techniques substructuring static condensation super-element

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A multiscale material model for heterogeneous liquid droplets in solid soft composites

《结构与土木工程前沿（英文）》 2021年第15卷第5期页码 1292-1299 doi: 10.1007/s11709-021-0771-3

摘要： Liquid droplets in solid soft composites have been attracting increasing attention in biological applications. In contrary with conventional composites, which are made of solid elastic inclusions, available material models for composites including liquid droplets are for highly idealized configurations and do not include all material real parameters. They are also all deterministic and do not address the uncertainties arising from droplet radius, volume fraction, dispersion and agglomeration. This research revisits the available models for liquid droplets in solid soft composites and presents a multiscale computational material model to determine their elastic moduli, considering nearly all relevant uncertainties and heterogeneities at different length scales. The effects of surface tension at droplets interface, their volume fraction, size, size polydispersity and agglomeration on elastic modulus, are considered. Different micromechanical material models are incorporated into the presented computational framework. The results clearly indicate both softening and stiffening effects of liquid droplets and show that the model can precisely predict the effective properties of liquid droplets in solid soft composites.

关键词： liquid in solid soft composite computational modeling multiscale model heterogeneity

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A multiscale-contour-based interpolation framework for generating a time-varying quasi-dense point cloud

Chu-hua HUANG,Dong-ming LU,Chang-yu DIAO

《信息与电子工程前沿（英文）》 2016年第17卷第5期页码 422-434 doi: 10.1631/FITEE.1500316

摘要： To speed up the reconstruction of 3D dynamic scenes in an ordinary hardware platform, we propose an efficient framework to reconstruct 3D dynamic objects using a multiscale-contour-based interpolation from multi-view videos. Our framework takes full advantage of spatio-temporal-contour consistency. It exploits the property to interpolate single contours, two neighboring contours which belong to the same model, and two contours which belong to the same view at different times, corresponding to point-, contour-, and model-level interpolations, respectively. The framework formulates the interpolation of two models as point cloud transport rather than non-rigid surface deformation. Our framework speeds up the reconstruction of a dynamic scene while improving the accuracy of point-pairing which is used to perform the interpolation. We obtain a higher frame rate, spatio-temporal-coherence, and a quasi-dense point cloud sequence with color information. Experiments with real data were conducted to test the efficiency of the framework.

关键词： Multi-view video Free-viewpoint video Point-pair Multiscale-contour-based interpolation Spatio-temporal-contour Consistency Time-varying point cloud sequence

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Connected morphable components-based multiscale topology optimization

Jiadong DENG, Claus B. W. PEDERSEN, Wei CHEN

《机械工程前沿（英文）》 2019年第14卷第2期页码 129-140 doi: 10.1007/s11465-019-0532-3

摘要： The advances of manufacturing techniques, such as additive manufacturing, have provided unprecedented opportunities for producing multiscale structures with intricate latticed/cellular material microstructures to meet the increasing demands for parts with customized functionalities. However, there are still difficulties for the state-of-the-art multiscale topology optimization (TO) methods to achieve manufacturable multiscale designs with cellular materials, partially due to the disconnectivity issue when tiling material microstructures. This paper attempts to address the disconnectivity issue by extending component-based TO methodology to multiscale structural design. An effective linkage scheme to guarantee smooth transitions between neighboring material microstructures (unit cells) is devised and investigated. Associated with the advantages of components-based TO, the number of design variables is greatly reduced in multiscale TO design. Homogenization is employed to calculate the effective material properties of the porous materials and to correlate the macro/structural scale with the micro/material scale. Sensitivities of the objective function with respect to the geometrical parameters of each component in each material microstructure have been derived using the adjoint method. Numerical examples demonstrate that multiscale structures with well-connected material microstructures or graded/layered material microstructures are realized.

关键词： multiscale topology optimization morphable component material microstructure homogenization

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Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MDmethod

Yue HOU, Linbing WANG

《结构与土木工程前沿（英文）》 2017年第11卷第3期页码 270-278 doi: 10.1007/s11709-017-0408-8

摘要： In this paper, a combined DEM-MD method is proposed to simulate the crack failure process of Hydrated Cement Paste (HCP) under a tensile force. A three-dimensional (3D) multiscale mechanical model is established using the combined Discrete Element Method (DEM)-Molecular Dynamics (MD) method in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). In the 3D model, HCP consists of discrete particles and atoms. Simulation results show that the combined DEM-MD model is computationally efficient with good accuracy in predicting tensile failures of HCP.

关键词： hydrated cement paste multiscale MD simulation DEM

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激光增材制造的热力学和动力学多尺度理解

顾冬冬, 马成龙, 夏木建, 戴冬华, 石齐民

《工程（英文）》 2017年第3卷第5期页码 675-684 doi: 10.1016/J.ENG.2017.05.011

摘要：

选择性激光熔化（SLM）增材制造（AM）技术已成为精密制造高性能复杂形状金属零件的重要选择。SLM AM 工艺涉及复杂的物理化学现象、热力学特性以及高能激光束融化散粉颗粒时产生的相变。本文提出了针对金属材料SLM 工艺的多尺度建模和协调控制，其中，金属材料包括铝（Al）基合金（AlSi10Mg）、镍（Ni）基超合金（Inconel 718）及陶瓷颗粒增强的铝基和镍基复合材料。从微观尺度研究氮化铝（AlN）颗粒在SLM 处理后的铝基纳米复合材料中的迁移和分布机制以及SLM处理后的碳化钨（WC）/Inconel 718 复合材料中增强体和基体之间梯度界面的原位形成。从中尺度研究AlSi10Mg 和Inconel 718 合金粉末的激光吸收和熔化/ 致密化特性。最后，从宏观尺度提出了逐行局部激光扫描过程中的应力发展和SLM 处理后的复合材料变形的参数依赖控制方法。多尺度数值模拟和实验验证方法有利于监测SLM AM 过程中复杂的粉末激光作用、传热传质特性以及微观结构和力学性能的发展。

关键词：增材制造选择性激光熔化多尺度建模热力学动力学

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智能互通信多尺度工程——面向未来的工程研究

袁月, 祝京旭

《工程（英文）》 2023年第30卷第11期页码 13-19 doi: 10.1016/j.eng.2023.03.021

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混凝土中碱硅反应效应的多尺度均质化分析 Article

Roozbeh Rezakhani, Mohammed Alnaggar, Gianluca Cusatis

《工程（英文）》 2019年第5卷第6期页码 1139-1154 doi: 10.1016/j.eng.2019.02.007

摘要：

碱硅反应（ASR）是混凝土结构（如桥梁和水坝）在长期的高湿度环境下发生的主要劣化机制之一。ASR是骨料中活性硅成分与水泥浆中碱金属离子之间发生的一种化学反应。这种化学反应会产生ASR凝胶，该凝胶吸水后膨胀，造成混凝土损坏和开裂，最终导致混凝土力学性能下降。本研究基于晶格离散粒子模型（LDPM），研究了混凝土的ASR损伤。LDPM可在粗骨料尺度上模拟混凝土，它是一种中尺度力学模型。作者已经成功地利用LDPM框架对ASR建模，并且通过实验数据对所得模型ASR-LDPM进行了校准和验证。本研究将ASR-LDPM用作中尺度模型，并采用最新开发的多尺度均质化框架来模拟ASR的宏观尺度效应。作者首先分析了由ASR-LDPM模拟的混凝土代表性体积元（RVE）在拉伸和压缩两种情况下的均质化行为，并研究了ASR对混凝土有效力学性能的影响。接下来，作者利用已开发的均质化框架再现了关于混凝土棱柱体自由体积膨胀的实验数据。最后，作者通过中尺度模型和所提出的多尺度方法，评估了压缩和四点弯曲梁中棱柱体的强度退化现象，以分析后者的准确性和计算效率。在所有数值分析中，作者考虑了具有不同内部粒子划分的RVE大小，以探讨它们对均质化响应的影响。

关键词：多尺度均质化代表性体积元碱硅反应晶格离散粒子模型

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Multiscale process systems engineering—analysis and design of chemical and energy systems from molecular

《化学科学与工程前沿（英文）》 2022年第16卷第2期页码 137-140 doi: 10.1007/s11705-021-2135-x

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Applications of dynamical complexity theory in traditional Chinese medicine

null

《医学前沿（英文）》 2014年第8卷第3期页码 279-284 doi: 10.1007/s11684-014-0367-6

摘要：

Traditional Chinese medicine (TCM) has been gradually accepted by the world. Despite its widespread use in clinical settings, a major challenge in TCM is to study it scientifically. This difficulty arises from the fact that TCM views human body as a complex dynamical system, and focuses on the balance of the human body, both internally and with its external environment. As a result, conventional tools that are based on reductionist approach are not adequate. Methods that can quantify the dynamics of complex integrative systems may bring new insights and utilities about the clinical practice and evaluation of efficacy of TCM. The dynamical complexity theory recently proposed and its computational algorithm, Multiscale Entropy (MSE) analysis, are consistent with TCM concepts. This new system level analysis has been successfully applied to many health and disease related topics in medicine. We believe that there could be many promising applications of this dynamical complexity concept in TCM. In this article, we propose some promising applications and research areas that TCM practitioners and researchers can pursue.

关键词： traditional Chinese medicine Multiscale Entropy dynamical complexity system level applications

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Visualization of force networks in 2D dense granular materials

Jianguo LIU, Qicheng SUN, Feng JIN,

《结构与土木工程前沿（英文）》 2010年第4卷第1期页码 109-115 doi: 10.1007/s11709-010-0003-8

摘要： Dense granular matter is a conglomeration of discrete solid and closely packed particles. As subjected to external loadings, the stress is largely transmitted by heavily stressed chains of particles forming a sparse network of larger contact forces. To understand the structure and evolution of force chains, a photoelastic technique was improved for determining stresses and strains in the assemblies of photoelastic granular disks in this paper. A two-dimensional vertical slab was designed. It contains 7200 polydispersed photoelastic disks and is subjected to a localized probe penetrating at the top of the slab to mimic the cone penetration test. The interparticle contact force distribution was found a peak around the mean value, a roughly exponential tail for greater force and a dip toward zero for smaller force. The force chain network around the probe tip was depicted, and the contact angle distribution of particles in force chains was found to be well aligned in the directions of major principal stress.

关键词： granular matter force chain multiscale modeling