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Thermal reffusivity: uncovering phonon behavior, structural defects, and domain size

Yangsu XIE, Bowen ZHU, Jing LIU, Zaoli XU, Xinwei WANG

《能源前沿（英文）》 2018年 第12卷 第1期   页码 143-157 doi: 10.1007/s11708-018-0520-z

摘要： To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we make a systematic review on the newly developed thermal reffusivity theory. Like electrical resistivity which has been historically used as a theory for analyzing structural domain size and defect levels of metals, the thermal reffusivity can also uncover phonon behavior, structure defects and domain size of materials. We highlight that this new theory can be used for not only metals, but also nonmetals, even for amorphous materials. From the thermal reffusivity against temperature curves, the Debye temperature of the material and the ideal thermal diffusivity of single perfect crystal can be evaluated. From the residual thermal reffusivity at the 0 K limit, the structural thermal domain (STD) size of crystalline and amorphous materials can be obtained. The difference of white hair and normal black hair from heat conduction perspective is reported for the first time. Loss of melanin results in a worse thermal protection and a larger STD size in the white hair. By reviewing the different variation of thermal reffusivity against decreasing temperature profiles, we conclude that they reflected the structural connection in the materials. Ultimately, the future application of thermal reffusivity theory in studying 2D materials and amorphous materials is discussed.

关键词： thermal reffusivity theory     phonon behavior     structure defects     structural thermal domain (STD) size     2D material     amorphous material    

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Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0758-y

摘要： Accurately controlling the nodal lines of vibrating structures with topology optimization is a highly challenging task. The major difficulties in this type of problem include a large number of design variables, the highly nonlinear and multi-peak characteristics of iteration, and the changeable orders of eigenmodes. In this study, an effective material-field series-expansion (MFSE)-based topology optimization design strategy for precisely controlling nodal lines is proposed. Here, two typical optimization targets are established: (1) minimizing the difference between structural nodal lines and their desired positions, and (2) keeping the position of nodal lines within the specified range while optimizing certain dynamic performance. To solve this complex optimization problem, the structural topology of structures is first represented by a few design variables on the basis of the MFSE model. Then, the problems are effectively solved using a sequence Kriging-based optimization algorithm without requiring design sensitivity analysis. The proposed design strategy inherently circumvents various numerical difficulties and can effectively obtain the desired vibration modes and nodal lines. Numerical examples are provided to validate the proposed topology optimization models and the corresponding solution strategy.

关键词： nodal line     topology optimization     structural dynamics design     material-field series-expansion    

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Magnetic confinement fusion: a brief review

Chuanjun HUANG, Laifeng LI

《能源前沿（英文）》 2018年 第12卷 第2期   页码 305-313 doi: 10.1007/s11708-018-0539-1

摘要： Fusion energy is considered to be the ultimate energy source, which does not contribute to climate change compared with conventional fossil fuel. It is massive compared with unconventional renewable energy and demonstrates fewer safety features compared with unconventional fission energy. During the past several decades, never-ceasing efforts have been made to peacefully utilize the fusion energy in various approaches, especially inertial confinement and magnetic confinement. In this paper, the main developments of magnetic confinement fusion with emphasis on confinement systems as well as challenges of materials related to superconducting magnet and plasma-facing components are reviewed. The scientific feasibility of magnetic confinement fusion has been demonstrated in JET, TFTR, JT-60, and EAST, which instigates the construction of the International Thermonuclear Experimental Reactor (ITER). A fusion roadmap to DEMO and commercial fusion power plant has been established and steady progresses have been made to achieve the ultimate energy source.

关键词： fusion energy     magnetic confinement     tokamak     structural material     superconducting magnet    

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Dynamic material performance of cold-formed steel hollow sections: a state-of-the-art review

Cameron B. RITCHIE, Jeffrey A. PACKER, Xiao-Ling ZHAO, Amin HEIDARPOUR, Yiyi CHEN

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 209-227 doi: 10.1007/s11709-017-0388-8

摘要： This paper presents a literature review focused on the material performance of cold-formed, carbon steel, hollow structural sections under impulsive (highly dynamic) loading. Impulsive loading, represented by impact and blast, is characterized by a very rapid, time-dependent loading regime in the affected members and materials. Thus, the effect of high-strain-rate loading is initially reviewed. Next the material toughness, an important energy-absorption property and one measure of a material’s ability to arrest fracture, is considered by means of studying the Charpy V-notch behavior. The response of hollow sections under axial and lateral impact loading is then reviewed. ??Studies of blast on hollow sections, most of which fall under the categories of contact/near-field loading or far-field loading are presented. Under large-scale field blast experiments, cold-formed hollow sections have shown excellent behavior. Software for modeling blast loading and structural response, the latter including single degree of freedom analysis and explicit finite element analysis, is described and discussed.

关键词： cold-formed steel     hollow structural sections     composites     impulsive loading     impact     blast     experimentation     analysis     material properties    

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Influence factors on natural frequencies of composite materials

Bo WANG, Feng ZHAO, Zixu ZHAO, Kunpeng XU

《机械工程前沿（英文）》 2020年 第15卷 第4期   页码 571-584 doi: 10.1007/s11465-020-0592-4

摘要： Compared with traditional materials, composite materials have lower specific gravity, larger specific strength, larger specific modulus, and better designability structure and structural performance. However, the variability of structural properties hinders the control and prediction of the performance of composite materials. In this work, the Rayleigh–Ritz and orthogonal polynomial methods were used to derive the dynamic equations of composite materials and obtain the natural frequency expressions on the basis of the constitutive model of laminated composite materials. The correctness of the analytical model was verified by modal hammering and frequency sweep tests. On the basis of the established theoretical model, the influencing factors, including layers, thickness, and fiber angles, on the natural frequencies of laminated composites were analyzed. Furthermore, the coupling effects of layers, fiber angle, and lay-up sequence on the natural frequencies of composites were studied. Research results indicated that the proposed method could accurately and effectively analyze the influence of single and multiple factors on the natural frequencies of composite materials. Hence, this work provides a theoretical basis for preparing composite materials with different natural frequencies and meeting the requirements of different working conditions.

关键词： composite material     hammering and frequency sweep test     structural parameter     natural frequency    

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Research on recycled concrete and its utilization in building structures in China

Jianzhuang XIAO, Tao DING

《结构与土木工程前沿（英文）》 2013年 第7卷 第3期   页码 215-226 doi: 10.1007/s11709-013-0212-z

摘要： Large quantities of construction and demolition (C&D) building waste are being generated as a result of rapid urbanization and natural disasters in China. An increasing awareness of environmental protection is escalating C&D waste disposal concerns. This paper presents a brief introduction to current shaking table test research in China on structures built with recycled aggregate concrete (RAC). Test structures include a cast-in situ frame model, a precast frame model and a block masonry building. The test results prove that it is feasible to use RAC as a structural material in seismic areas, with recommended modifications and proper design, especially in low-rise structures. This paper also presents several successful applications of RAC in civil and structural engineering projects in China, which will serve to promote RAC as a global ecological structural material.

关键词： recycled aggregate concrete (RAC)     structural material     shaking table tests     building structure    

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混凝土结构性干预所必需的材料力学性能 Article

Tamon Ueda

《工程（英文）》 2019年 第5卷 第6期   页码 1131-1138 doi: 10.1016/j.eng.2019.02.012

摘要：

结构性干预包括修复和（或）改善结构性能。除了混凝土和钢材这两种典型的混凝土结构材料外，各种纤维增强复合材料（FRP），混合纤维、聚合物和黏合剂的黏结材料也常被用于结构性干预。为了预测结构性能，有必要开发一种不仅适用于钢材，而且适用于其他材料的通用方法。这种通用模型可以提供有关改善结构性能所需的力学性能的信息。外部黏结是一种典型的结构干预方案，在新结构中没有得到应用。为了在基体混凝土和外部黏结材料的接合点上获得更好的黏结强度，我们有必要阐明材料的性能和结构细节。本文介绍基体混凝土的力学性能和相关干预材料用于以下目的：①获得更高的抗剪强度和减少构件在结构性干预后的极限变形；②使外部黏结获得更高的黏结强度。本文得出的结论是，在有结构干预的结构中，为了提高结构的力学性能，干预材料的一些力学性能和结构细节是新的，且不同于没有干预的结构。例如，在无结构性干预的结构中，高强度和高刚度是材料的重要性能，而高断裂应力和低刚度是结构干预材料的重要性能。

关键词： 结构性干预     高断裂应力     无屈服     低刚度     粗糙度     FRP 聚合物    

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Liquid metal material genome: Initiation of a new research track towards discovery of advanced energy

Lei WANG, Jing LIU

《能源前沿（英文）》 2013年 第7卷 第3期   页码 317-332 doi: 10.1007/s11708-013-0271-9

摘要： As the basis of modern industry, the roles materials play are becoming increasingly vital in this day and age. With many superior physical properties over conventional fluids, the low melting point liquid metal material, especially room-temperature liquid metal, is recently found to be uniquely useful in a wide variety of emerging areas from energy, electronics to medical sciences. However, with the coming enormous utilization of such materials, serious issues also arise which urgently need to be addressed. A biggest concern to impede the large scale application of room-temperature liquid metal technologies is that there is currently a strong shortage of the materials and species available to meet the tough requirements such as cost, melting point, electrical and thermal conductivity, etc. Inspired by the Material Genome Initiative as issued in 2011 by the United States of America, a more specific and focused project initiative was proposed in this paper—the liquid metal material genome aimed to discover advanced new functional alloys with low melting point so as to fulfill various increasing needs. The basic schemes and road map for this new research program, which is expected to have a worldwide significance, were outlined. The theoretical strategies and experimental methods in the research and development of liquid metal material genome were introduced. Particularly, the calculation of phase diagram (CALPHAD) approach as a highly effective way for material design was discussed. Further, the first-principles (FP) calculation was suggested to combine with the statistical thermodynamics to calculate the thermodynamic functions so as to enrich the CALPHAD database of liquid metals. When the experimental data are too scarce to perform a regular treatment, the combination of FP calculation, cluster variation method (CVM) or molecular dynamics (MD), and CALPHAD, referred to as the mixed FP-CVM-CALPHAD method can be a promising way to solve the problem. Except for the theoretical strategies, several parallel processing experimental methods were also analyzed, which can help improve the efficiency of finding new liquid metal materials and reducing the cost. The liquid metal material genome proposal as initiated in this paper will accelerate the process of finding and utilization of new functional materials.

关键词： liquid metal material genome     energy material     material discovery     advanced material     room-temperature liquid alloy     thermodynamics     phase diagram    

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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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Approximation of structural damping and input excitation force

Mohammad SALAVATI

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 244-254 doi: 10.1007/s11709-016-0371-9

摘要： Structural dynamic characteristics are the most significant parameters that play a decisive role in structural damage assessment. The more sensitive parameter to the damage is the damping behavior of the structure. The complexity of structural damping mechanisms has made this parameter to be one of the ongoing research topics. Despite all the difficulties in the modeling of damping, there are some approaches like as linear and nonlinear models which are described as the energy dissipation throughout viscous, material or structural hysteretic and frictional damping mechanisms. In the presence of a mathematical model of the damping mechanisms, it is possible to estimate the damping ratio from the theoretical comparison of the damped and un-damped systems. On the other hand, solving the inverse problem of the input force estimation and its distribution to each SDOFs, from the measured structural responses plays an important role in structural identification process. In this paper model-based damping approximation method and a model-less structural input estimation are considered. The effectiveness of proposed methods has been carried out through analytical and numerical simulation of the lumped mass system and the results are compared with reference data. Consequently, high convergence of the comparison results illustrates the satisfactory of proposed approximation methods.

关键词： structural modal parameters     damping identification method     input excitation force identification     Inverse problem    

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工程材料研究中科学问题的思考

于翘

《中国工程科学》 1999年 第1卷 第3期   页码 1-4

摘要：

在不少场合下，航天用工程材料处在极端条件下工作，这就对材料提出许多特殊的要求，虽然国内外有一定的研究积累，但对更精确的模型和符合特定材料的损伤的状态方程，有待深一步研究。如高级弹头再入时气动加热和粒子云侵蚀以及两者耦合效应引起弹头防护材料增大后退量的问题；空中垃圾和微流星的高速碰撞对航天器的威胁；特别是核爆和激光武器对材料的损伤和破坏，实质上是辐射引起的热击波层裂破坏，这些都属于超高速碰撞对材料的响应问题。天线罩材料、吸波材料、红外隐身材料、电磁屏蔽材料都是具有不同波长电磁波的电磁功能材料，它们对固体介质的穿透、吸收、反射等会产生响应，不同的电磁功能材料，其宏观性能的物理参量不同，但有几个参量是通用的，如介电常数、磁导率和损耗角正切，搞清这些参量与材料微观结构的关系，可以为材料设计和材料创新提供科学依据。

关键词： 天线罩材料     吸波材料     红外隐身材料     电磁兼容材料    

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A novel approach to minimizing material loss for computer numerical control flank-regrinding of worn

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0757-z

摘要： Flanks of end mills are prone to wear in a long machining process. Regrinding is widely used in workshops to restore the flank to an original-like state. However, the traditional method involves material waste by trial and error and dramatically decreases the potential regrinding. Moreover, over-cut would happen to the flutes of worn cutters in the regrinding processes because of improper wheel path. This study presented a new approach to planning the wheel path for regrinding worn end mills to minimize material loss and recover the over-cut. In planning, a scaling method was developed to determine the maximum size of the new cutter according to the similarity of cutter shapes before and after regrinding. Then, the wheel path is first generated by envelope theory to regrind the worn area with a four-axis computer numerical control grinder according to the new size of cutters. Moreover, a second regrinding strategy is applied to recover the flute shape over-cut in the first grinding. Finally, the proposed method is verified by an experiment. Results showed that the proposed approach could save 25% of cutter material compared with the traditional method and ensure at least three regrinding times. This work effectively provides a general regrinding solution for the worn flank with maximum material-saving and regrinding period.

关键词： flank-regrinding     worn end mill     wheel position and orientation     material loss     over-cut    

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Effects of green roof damping and configuration on structural seismic response

《结构与土木工程前沿（英文）》   页码 1133-1144 doi: 10.1007/s11709-023-0959-9

摘要： Sustainable structures are critical for addressing global climate change. Hence, their structural resilience or ability to recover from natural events must be considered comprehensively. Green roofs are a widely used sustainable feature that improve the environment while providing excellent occupant amenity. To expand their usage, their inherent damping and layout sensitivity to seismic performance are investigated in this study. The soil of a green roof can serve as a damper to dissipate the energy generated by earthquakes or other dynamic events. Results of preliminary analysis show that a green roof soil can increase localized damping by 2.5% under both dry and saturated conditions. Based on these findings, nonlinear time-history analyses are conducted on a three-story building in SAP2000 to monitor the structural behavior with and without a green roof. The increased damping in the green roof soil is beneficial to the structural performance, i.e., it reduces the building displacement and acceleration by 10% and 12%, respectively. Additionally, certain configurations are more effective and beneficial to the structural response than others, which suggests the possibility of design optimization. Based on the findings of this study, new methods of modeling and considering green roofs in structural design are established.

关键词： green infrastructure     green roof     structural resilience     seismic design    

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Development of an integrated structural health monitoring system for bridge structures in operational

Xinqun ZHU, Hong HAO

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 321-333 doi: 10.1007/s11709-012-0161-y

摘要： This paper presents an overview of development of an integrated structural health monitoring system. The integrated system includes vibration and guided-wave based structural health monitoring. It integrates the real-time heterogeneous sensor data acquiring system, data analysis and interpretation, physical-based numerical simulation of complex structural system under operational conditions and structural evaluation. The study is mainly focused on developing: integrated sensor technology, integrated structural damage identification with operational loads monitoring, and integrated structural evaluation with results from system identification. Numerical simulation and its implementation in laboratory show that the system is effective and reliable to detect local damage and global conditions of bridge structures.

关键词： integrated structural health monitoring     operational conditions     vibration and guided wave    

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A MATLAB code for the material-field series-expansion topology optimization method

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 607-622 doi: 10.1007/s11465-021-0637-3

摘要： This paper presents a MATLAB implementation of the material-field series-expansion (MFSE) topo-logy optimization method. The MFSE method uses a bounded material field with specified spatial correlation to represent the structural topology. With the series-expansion method for bounded fields, this material field is described with the characteristic base functions and the corresponding coefficients. Compared with the conventional density-based method, the MFSE method decouples the topological description and the finite element discretization, and greatly reduces the number of design variables after dimensionality reduction. Other features of this method include inherent control on structural topological complexity, crisp structural boundary description, mesh independence, and being free from the checkerboard pattern. With the focus on the implementation of the MFSE method, the present MATLAB code uses the maximum stiffness optimization problems solved with a gradient-based optimizer as examples. The MATLAB code consists of three parts, namely, the main program and two subroutines (one for aggregating the optimization constraints and the other about the method of moving asymptotes optimizer). The implementation of the code and its extensions to topology optimization problems with multiple load cases and passive elements are discussed in detail. The code is intended for researchers who are interested in this method and want to get started with it quickly. It can also be used as a basis for handling complex engineering optimization problems by combining the MFSE topology optimization method with non-gradient optimization algorithms without sensitivity information because only a few design variables are required to describe relatively complex structural topology and smooth structural boundaries using the MFSE method.

关键词： MATLAB implementation     topology optimization     material-field series-expansion method     bounded material field     dimensionality reduction    

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标题 作者 时间 类型 操作

Thermal reffusivity: uncovering phonon behavior, structural defects, and domain size

Yangsu XIE, Bowen ZHU, Jing LIU, Zaoli XU, Xinwei WANG

期刊论文

Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

期刊论文

Magnetic confinement fusion: a brief review

Chuanjun HUANG, Laifeng LI

期刊论文

Dynamic material performance of cold-formed steel hollow sections: a state-of-the-art review

Cameron B. RITCHIE, Jeffrey A. PACKER, Xiao-Ling ZHAO, Amin HEIDARPOUR, Yiyi CHEN

期刊论文

Influence factors on natural frequencies of composite materials

Bo WANG, Feng ZHAO, Zixu ZHAO, Kunpeng XU

期刊论文

Research on recycled concrete and its utilization in building structures in China

Jianzhuang XIAO, Tao DING

期刊论文

混凝土结构性干预所必需的材料力学性能

Tamon Ueda

期刊论文

Liquid metal material genome: Initiation of a new research track towards discovery of advanced energy

Lei WANG, Jing LIU

期刊论文

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

Yu-Chin CHAN, Kohei SHINTANI, Wei CHEN

期刊论文

Approximation of structural damping and input excitation force

Mohammad SALAVATI

期刊论文

工程材料研究中科学问题的思考

于翘

期刊论文

A novel approach to minimizing material loss for computer numerical control flank-regrinding of worn

期刊论文

Effects of green roof damping and configuration on structural seismic response

期刊论文

Development of an integrated structural health monitoring system for bridge structures in operational

Xinqun ZHU, Hong HAO

期刊论文

A MATLAB code for the material-field series-expansion topology optimization method

期刊论文