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Compressive behavior and energy absorption of polymeric lattice structures made by additive manufacturing

Sheng WANG, Jun WANG, Yingjie XU, Weihong ZHANG, Jihong ZHU

《机械工程前沿（英文）》 2020年第15卷第2期页码 319-327 doi: 10.1007/s11465-019-0549-7

摘要： Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat dissipation. In this work, by combining experimental and numerical methods, we investigate the compressive behavior and energy absorption of lattices made through the stereolithography apparatus process. Four types of lattice structures are considered: (i) Uniform body-centered-cubic (U-BCC); (ii) graded body-centered-cubic (G-BCC); (iii) uniform body-centered-cubic with -axis reinforcement (U-BCCz); and (iv) graded body-centered-cubic with -axis reinforcement (G-BCCz). We conduct compressive tests on these four lattices and numerically simulate the compression process through the finite element method. Analysis results show that BCCz has higher modulus and strength than BCC. In addition, uniform lattices show better energy absorption capabilities at small compression distances, while graded lattices absorb more energy at large compression distances. The good correlation between the simulation results and the experimental phenomena demonstrates the validity and accuracy of the present investigation method.

关键词： lattice structure polymer compressive behavior additive manufacturing simulation

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Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

《结构与土木工程前沿（英文）》 2023年第17卷第2期页码 306-325 doi: 10.1007/s11709-022-0890-5

摘要： This paper numerically studied the effect of uncertainty and random distribution of concrete strength in beams failing in shear and flexure using lattice modeling, which is suitable for statistical analysis. The independent variables of this study included the level of strength reduction and the number of members with reduced strength. Three levels of material deficiency (i.e., 10%, 20%, 30%) were randomly introduced to 5%, 10%, 15%, and 20% of members. To provide a database and reliable results, 1000 analyses were carried out (a total of 24000 analyses) using the MATLAB software for each combination. Comparative studies were conducted for both shear- and flexure-deficit beams under four-point loading and results were compared using finite element software where relevant. Capability of lattice modeling was highlighted as an efficient tool to account for uncertainty in statistical studies. Results showed that the number of deficient members had a more significant effect on beam capacity compared to the level of strength deficiency. The scatter of random load-capacities was higher in flexure (range: 0.680–0.990) than that of shear (range: 0.795–0.996). Finally, nonlinear regression relationships were established with coefficient of correlation values (R²) above 0.90, which captured the overall load–deflection response and level of load reduction.

关键词： lattice modeling shear failure flexural failure uncertainty deficiency numerical simulation

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Modeling nanostructured catalyst layer in PEMFC and catalyst utilization

Jiejing ZHANG, Pengzhen CAO, Li XU, Yuxin WANG

《化学科学与工程前沿（英文）》 2011年第5卷第3期页码 297-302 doi: 10.1007/s11705-011-1201-1

摘要： A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells (PEMFC) was established by Monte Carlo method. The model takes into account all the four components in a typical PEMFC catalyst layer: platinum (Pt), carbon, ionomer and pore. The elemental voxels in the lattice were set fine enough so that each average sized Pt particulate in Pt/C catalyst can be represented. Catalyst utilization in the modeled catalyst layer was calculated by counting up the number of facets of Pt voxels where “three phase contact” are met. The effects of some factors, including porosity, ionomer content, Pt/C particle size and Pt weight percentage in the Pt/C catalyst, on catalyst utilization were investigated and discussed.

关键词： catalyst layer PEM fuel cell lattice model Monte Carlo method catalyst utilization

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Simulation of interfacial Marangoni convection in gas-liquid mass transfer by lattice Boltzmann method

Shuyong CHEN, Xigang YUAN, Bo FU, Kuotsung YU

《化学科学与工程前沿（英文）》 2011年第5卷第4期页码 448-454 doi: 10.1007/s11705-011-1142-8

摘要： Interfacial Marangoni convection has significant effect on gas-liquid and/or liquid-liquid mass transfer processes. In this paper, an approach based on lattice Boltzmann method is established and two perturbation models, fixed perturbation model and self-renewable interface model, are proposed for the simulation of interfacial Marangoni convection in gas-liquid mass transfer process. The simulation results show that the concentration contours are well consistent with the typical roll cell convection patterns obtained experimentally in previous studies.

关键词： interfacial Marangoni convection lattice Boltzmann method gas-liquid mass transfer

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slip investigation based on finite element modelling verified by experimental results on wind turbine lattice

Saleh YAGHOOBI, Ahmad SHOOSHTARI

《结构与土木工程前沿（英文）》 2018年第12卷第3期页码 341-351 doi: 10.1007/s11709-017-0393-y

摘要：

Slippage corresponds to the relative displacement of a bolted joint subjected to shear loads since the construction clearance between the bolt shank and the bolthole at assembly can cause joint slip. Deflections of towers with joint slippage effects is up to 1.9 times greater than the displacements obtained by linear analytical methods. In this study, 8 different types of joints are modelled and studied in the finite element program, and the results are verified by the experimental results which have been done in the laboratory. Moreover, several types of joints have been modelled and studied and load-deformation curves have also been presented. Finally, joint slip data for different types of angles, bolt diameter and bolt arrangements are generated. Thereupon, damping ratios (z) for different types of connections are reported. The study can be useful to help in designing of wind turbine towers with a higher level of accuracy and safety.

关键词： Joint slip cyclic loading Finite element modelling Experimental joint behavior damping ratios (

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URANS simulation of the turbulent flow in tight lattice bundle

Yiqi YU, Yanhua YANG

《能源前沿（英文）》 2011年第5卷第4期页码 404-411 doi: 10.1007/s11708-011-0165-7

摘要： The flow structure in tight lattice is still of great interest to nuclear industry. An accurate prediction of flow parameter in subchannels of tight lattice is likable. Unsteady Reynolds averaged Navier Stokes (URANS) is a promising approach to achieve this goal. The implementation of URANS approach will be validated by comparing computational results with the experimental data of Krauss. In this paper, the turbulent flow with different Reynolds number (5000–215000) and different pitch-to-diameter( / ) (1.005–1.2) are simulated with computational fluid dynamics (CFD) code CFX12. The effects of the Reynolds number and the bundle geometry ( / ) on wall shear stress, turbulent kinetic energy, turbulent mixing and large scale coherent structure in tight lattice are analyzed in details. It is hoped that the present work will contribute to the understanding of these important flow phenomena and facilitate the prediction and design of rod bundles.

关键词： tight rod bundle flow structure unsteady Reynolds averaged Navier Stokes (URANS)

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Robust topology optimization of multi-material lattice structures under material and load uncertainties

Yu-Chin CHAN, Kohei SHINTANI, Wei CHEN

《机械工程前沿（英文）》 2019年第14卷第2期页码 141-152 doi: 10.1007/s11465-019-0531-4

摘要： Enabled by advancements in multi-material additive manufacturing, lightweight lattice structures consisting of networks of periodic unit cells have gained popularity due to their extraordinary performance and wide array of functions. This work proposes a density-based robust topology optimization method for meso- or macro-scale multi-material lattice structures under any combination of material and load uncertainties. The method utilizes a new generalized material interpolation scheme for an arbitrary number of materials, and employs univariate dimension reduction and Gauss-type quadrature to quantify and propagate uncertainty. By formulating the objective function as a weighted sum of the mean and standard deviation of compliance, the tradeoff between optimality and robustness can be studied and controlled. Examples of a cantilever beam lattice structure under various material and load uncertainty cases exhibit the efficiency and flexibility of the approach. The accuracy of univariate dimension reduction is validated by comparing the results to the Monte Carlo approach.

关键词： robust topology optimization lattice structures multi-material material uncertainty load uncertainty univariate dimension reduction

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标准模型下基于高效分级身份的格上加密方案 Article

Feng-he WANG,Chun-xiao WANG,Zhen-hua LIU

《信息与电子工程前沿（英文）》 2016年第17卷第8期页码 781-791 doi: 10.1631/FITEE.1500219

摘要：本文在标准模型下，利用固定维数的格基代理算法提出了一种高效的格基分级身份加密方案。其公钥尺寸仅为(dm2+mn)log q比特，而消息-密文扩展因子仅为log q，其中d为最大分级深度，(n, m, q)为公开参数。本文构造了一种新的公钥赋值算法，将1个随机、公开的矩阵平均赋值为两个身份比特，从而仅仅需要d个公开矩阵来构造标准模型下的HIBE方案；与之相比，Crypto 2010所提出的HIBE方案中需要2d个同样尺寸的矩阵，公钥尺寸达到(2dm2+mn+m)log q。为了将该方案的消息-密文扩展因子压缩到log q，本文基于Gentry的加密方案建立了一种基础加密算法，一次加密操作中能够加密m2比特明文并得到m2log q比特密文。因此，文中所提方案在公钥尺寸、消息-密文扩展因子等方面具有一定的优势。基于差错学习问题的困难性，我们证明该方案在选择身份、选择明文攻击下是安全的。

关键词：分级身份加密；格密码；标准模型；差错学习问题；高斯

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十字型出口人员疏散的堵塞研究

陈涛,宋卫国,范维澄,陆守香

《中国工程科学》 2004年第6卷第4期页码 56-60

摘要：

在开放边界条件下，采用无后退有偏随机走动者格子气模型对十字路口的行人疏散动力学进行了计算和模拟。结果显示，当纬向边界行人密度保持恒定时，经向和纬向通道行人堵塞现象的出现取决于不同的经向边界行人密度；当纬向通道宽度保持不变时，发生堵塞的临界边界行人密度取决于不同的经向通道宽度，纬向和经向的行人堵塞动力学演变具有不同的特征。模拟结果对于疏散通道的设计具有指导意义。

关键词：人员疏散格子气模型堵塞相变火灾

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拆除爆破数值模拟研究进展

谢先启,刘军,贾永胜,孙金山

《中国工程科学》 2014年第16卷第11期页码 20-27

摘要：

评述了数值模拟技术在拆除爆破中应用的重要性，回顾了拆除爆破数值模拟的主要方法，论述了各种方法的优缺点。结合工程应用实例介绍了笔者及团队研发的离散元框架内的网格实体模型。分析了当前拆除爆破数值模拟技术存在的主要问题，对拆除爆破数值模拟技术的进一步发展进行了展望。

关键词：拆除爆破数值模拟离散元网格实体模型

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超轻折叠夹层圆柱壳的制备及力学性能测试 Article

李万欣, 郑青, 范华林, 冀宾

《工程（英文）》 2020年第6卷第2期页码 196-204 doi: 10.1016/j.eng.2019.11.008

摘要：

在本研究中，我们设计、制备和测试了两种新型折叠夹层圆柱壳。格栅夹芯具有周期性的“之”字形波纹，其脊线与谷线沿着轴向或环向延伸。通过自由振动和轴向压缩试验，我们研究了圆柱壳的固有频率、自由振动模态、承载能力和失效模式。通过减小局部蒙皮周期单元的尺寸，折叠格栅夹芯能有效地抑制折叠夹层圆柱壳的局部屈曲；通过提高夹层的剪切刚度，折叠格栅夹芯能有效地提高折叠夹层圆柱壳整体的抗屈曲性能。圆柱壳在材料失效模式下失效，其具有良好的承载能力。轴向折叠夹层圆柱壳具有更高的承载能力，而环向折叠夹层圆柱壳具有更高的固有频率。这两种折叠格栅内芯为工程师设计有强度或振动要求的夹层圆柱壳提供了一种选择。本研究也为大尺寸折叠结构的制作和工程应用提供了一种可行的方法。

关键词：折叠夹层圆柱壳制备力学试验

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Soil arching effect of Lattice-Shaped Diaphragm Wall as bridge foundation

Jiujiang WU, Lingjuan WANG, Qiangong CHENG

《结构与土木工程前沿（英文）》 2017年第11卷第4期页码 446-454 doi: 10.1007/s11709-017-0397-7

摘要： As a new type of bridge foundation, Lattice-Shaped Diaphragm Wall (hereinafter for LSDW) is highly concerned in relevant construction area but its research is far from achievement. Based on PFC , the soil arching effect of LSDWs is studied thoroughly in this paper and the special attention is given to its influencing factors. It turns out to be that a differential wall-soil settlement can be found at the lower location of soil core of an LSDW which is one of the trigger factors of soil arching; meanwhile, the differential settlement degree can reflect the exertion degree of soil arching; the shape of soil arching is basically a hemisphere which can be explained by the theory proposed by Hewlett and Randolph; normally, the chamber number is a negative factor for the development of soil arching; the soil arching effect is significantly influenced by the distance of two adjacent wall elements and the foundation depth, and a relatively large or small value of these factors is disadvantageous to the exertion of soil arching; in addition, the soil arching effect increase with the growth of stiffness and friction coefficient of particles and the friction coefficient of particles has insignificant influence on the development of soil arching effect compared with particle stiffness.

关键词： LSDW soil arching PFC^2D shape of soil arching influencing factors

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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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Design and applications of morphing aircraft and their structures

《机械工程前沿（英文）》 2023年第18卷第3期 doi: 10.1007/s11465-023-0750-6

摘要： Morphing aircraft can adaptively regulate their aerodynamic layout to meet the demands of varying flight conditions, improve their aerodynamic efficiency, and reduce their energy consumption. The design and fabrication of high-performance, lightweight, and intelligent morphing structures have become a hot topic in advanced aircraft design. This paper discusses morphing aircraft development history, structural characteristics, existing applications, and future prospects. First, some conventional mechanical morphing aircraft are examined with focus on their morphing modes, mechanisms, advantages, and disadvantages. Second, the novel applications of several technologies for morphing unmanned aerial vehicles, including additive manufacturing for fabricating complex morphing structures, lattice technology for reducing structural weight, and multi-mode morphing combined with flexible skins and foldable structures, are summarized and categorized. Moreover, in consideration of the further development of active morphing aircraft, the paper reviews morphing structures driven by smart material actuators, such as shape memory alloy and macro-fiber composites, and analyzes their advantages and limitations. Third, the paper discusses multiple challenges, including flexible structures, flexible skins, and control systems, in the design of future morphing aircraft. Lastly, the development and application of morphing structures in the aerospace field are discussed to provide a reference for future research and engineering applications.

关键词： morphing aircraft additive manufacturing lattice structure smart material flexible structure flexible skin

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♮-convexity and its applications in operations

Xin CHEN

《工程管理前沿（英文）》 2017年第4卷第3期页码 283-294 doi: 10.15302/J-FEM-2017057

摘要： -convexity, one of the central concepts in discrete convex analysis, receives significant attentions in the operations literature in recent years as it provides a powerful tool to derive structures of optimal policies and allows for efficient computational procedures. In this paper, we present a survey of key properties of -convexity and some closely related results in lattice programming, several of which were developed recently and motivated by operations applications. As a new contribution to the literature, we establish the relationship between a notion called -differential monotonicity and -convexity. We then illustrate the techniques of applying -convexity through a detailed analysis of a perishable inventory model and a joint inventory and transshipment control model with random capacities.

关键词： L^&natur -convexity lattice programming perishable inventory models random capacity