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

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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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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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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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

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Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

Shanwei Hu, Xinhua Liu

《化学科学与工程前沿（英文）》 2021年第15卷第3期页码 579-590 doi: 10.1007/s11705-020-1953-6

摘要： Dual-loop circulating fluidized bed (CFB) reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability. However, the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms, meaning it has been heavily based on empiricism and stepwise experiments. Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them. This article proposed a general method for modeling multi-loop CFB systems by utilizing the energy minimization multiscale (EMMS) principle. A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors, to achieve the mass conservation and pressure balance in each circulation loop. Based on the modularization strategy, corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor. This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.

关键词： multi-loop circulating fluidized bed mathematical modeling energy minimization multiscale virtual fluidization mesoscale structure

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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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多尺度材料与过程设计的数据驱动和机理混合建模方法 Perspective

周腾, Rafiqul Gani, Kai Sundmacher

《工程（英文）》 2021年第7卷第9期页码 1231-1238 doi: 10.1016/j.eng.2020.12.022

摘要：

世界人口的不断增长要求加工业以更高效和更可持续的方式生产食品、燃料、化学品和消费品。功能性过程材料是这一挑战的核心。传统上，人们根据经验或者通过反复试验的方法来发现新型先进材料。随着理论方法和相关工具的不断改进和计算机能力的提高，现在流行使用计算方法来指导材料选择和设计，这种方法也非常有效。由于材料选择与材料使用的过程操作之间存在很强的相互作用，必须同时进行材料设计和过程设计。尽管有这种重要联系，但由于通常需要使用不同规模的多个模型，材料和过程的集成设计并不容易。混合建模为解决此类复杂的设计问题提供了一个有前景的选择。在混合建模中，用数据驱动模型描述原本计算成本高昂的材料特性，而用机理模型表示众所周知的过程相关原理。本文重点介绍了混合建模在多尺度材料和过程设计中的重要性。首先介绍通用设计方法，然后选择了六个重要的应用领域：四个来自化学工程领域，两个来自能源系统工程领域。对于选定的每个领域，讨论了使用混合建模进行多尺度材料和过程设计的最新研究。最后，本文给出了结论，指出当前研究的局限性和未来的发展空间。

关键词：数据驱动代理模型机器学习混合建模材料设计过程优化

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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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智能制造控制——多尺度研究领域的挑战

Han-Xiong Li, Haitao Si

《工程（英文）》 2017年第3卷第5期页码 608-615 doi: 10.1016/J.ENG.2017.05.016

摘要：

《中国制造2025》计划要求从顾客到产品等全部环节的全面自动化。这将为生产制造系统的各个环节带来巨大挑战。在未来的加工制造领域中，全部的设备和系统应当具有对控制性和适应性的感知能力和基础智能化处理的能力。在研究中，经过关于多尺度动力学在现代加工制造系统中应用的讨论后，一个五层的功能结构被用于不确定的加工制造过程。多尺度力学包括：多时间尺度、多时空尺度以及多尺度的动力学标准。随着快速与慢速的时间尺度对设计的更多要求，不同的尺度所对应的不同控制行为也将呈现区分化。低速时间尺度下的操作需要更多的定量化手段，与此同时，高速时间尺度下的监管也需要更多高质量的手段。智能生产系统应当拥有灵活应变的能力、较好的适应能力及足够的智能化程度。这些能力需要我们通过控制性手段进行区分化处理并应用在不同方面，如智能感知、优化设计、智能学习等。最后，将一个典型的喷射点胶系统模型用于多尺度建模和控制。

关键词：系统建模过程控制人工智能加工制造喷射点胶

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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 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