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Enhanced Natural Convection for Accelerating Melting of Phase Change Material in Cellular Structure through Inserting Fin

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Journal of Thermal Science 2024年第2期33卷 548-563页

作者： KONG Dekui zhang yongcun LIU Shutian State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian116024China

The design of thermal conductivity enhancers(TCE) is quite critical to overcoming the disadvantage of the poor thermal conductivity of phase change materials(PCM).The main contribution of this study is firstly to discuss how to actively enhance natural convection of the melted PCM in cellular structure by the fin formed in the structure under the condition of the same metal mass,apart from simultaneously improving heat conduction,which can boost the heat transfer ***,a tailored hybrid fin-lattice structure(HFS) as TCE is designed and fabricated by additive manufacturing(AM).A two-equation numerical method is applied to study the heat transfer of the PCM,and its feasibility is validated with the experimental *** numerical results indicate that enhanced natural convection and improved heat conduction can be obtained simultaneously when a well-designed fin is embedded into a lattice *** enhanced natural convection results in the improved melting rate and the decreased wall temperature;e.g.,the complete melting time and the wall temperature are reduced by 11.6% and 19.7%,respectively,because of the fin for metal ***,the parameters of HFS including the porosity,pore density,and fin dimension have a great impact on the heat *** enhancement effect of the fin for HFS on the melting rate of the PCM increases as the thermal conductivity of the base material *** example,when the fin is introduced into the lattice structure,the complete melting time is reduced by 24.1% for metal *** summary,this study enables us to obtain a good understanding of the mechanism of the heat transfer and provides necessary experimental data for the structural design of HFS fabricated by AM.

关键词： natural convection heat transfer enhancement phase change material additive manufacturing hybrid fin-lattice structure

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Enhancing buckling capacity of a rectangular plate under uniaxial compression by utilizing an auxetic material

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Chinese Journal of Aeronautics 2016年第4期29卷 945-951页

作者： zhang yongcun Li Xiaobin Liu Shutian State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology

Auxetic materials have previously been shown to enhance various performances due to its unusual property of becoming fatter when uniaxially stretched and thinner when uniaxially compressed (i.e., the materials exhibit a negative Poisson's ratio). The current study focuses on assessing the potential of an auxetic material to enhance the buckling capacity of a rectangular plate under uniaxial compression. The in-plane translational restraint along the unloaded edges that was often neglected in open literature is taken into consideration in our buckling model proposed in this study. The closed-form expressions for the critical buckling coefficient of the rectangle are provided and the predicted results agree well with those determined by the finite element method. Furthermore, the results indicate that the buckling performance of a rectangular plate under uniaxial compression can be significantly improved by replacing the traditional material that has a positive Poisson's ratio with an auxetic material when there is in-plane translation restraint along the unloaded edges. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.

关键词： Auxetic material Buckling Elastically restraint Negative Poisson's ratio Optimization

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A Realization Method for Transforming a Topology Optimization Design into Additive Manufacturing Structures

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Engineering 2018年第2期4卷 113-121页

作者： Shutian Liu Quhao Li Junhuan Liu Wenjiong Chen yongcun zhang State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian Liaoning 116024 China

Topology optimization is a powerful design approach that is used to determine the optimal topology in order to obtain the desired functional performance. It has been widely used to improve structural performance in engineering fields such as in the aerospace and automobile industries. However, some gaps still exist between topology optimization and engineering application, which significantly hinder the applica- tion of topology optimization. One of these gaps is how to interpret topology results, especially those obtained using the density framework, into parametric computer-aided design （CAD） models that are ready for subsequent shape optimization and manufacturing. In this paper, a new method for interpreting topology optimization results into stereolithography （STL） models and parametric CAD models is pro- posed. First, we extract the skeleton of the topology optimization result in order to ensure shape preser- vation and use a filtering method to ensure characteristics preservation. After this process, the distribution of the nodes in the boundary of the topology optimization result is denser, which will benefit the subsequent curve fitting. Using the curvature and the derivative of curvature of the uniform B-spline curve, an adaptive B-spline fitting method is proposed in order to obtain a parametric CAD model with the fewest control points meeting the requirement of the fitting error. A case study is presented to pro- vide a detailed description of the proposed method, and two more examples are shown to demonstrate the validity and versatility of the proposed method.

关键词： Topology optimization Additive manufacturing Characteristics preservation Adaptive fitting Shape optimization

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Double Star TC-1 observation of the earthward flowing plasmoids in the near magnetotail

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Chinese Science Bulletin 2007年第13期52卷 1843-1848页

作者： zhang yongcun LIU ZhenXing SHEN Chao DUAN SuPing HE ZhaoHai C M CARR H REME State Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China The Blackett Laboratory Imperial College London SW7 2BZ UK Centre d'Etudes Spatiale des Rayonnements BP 4346 31028 Toulouse Cedex 4 France

We analyze Double Star TC-1 magnetic field data from July to September in 2004 and find that plas-moids exist in the very near-Earth magnetotail. It is the first time that TC-1 observes the plasmoids inthe magnetotail at X > ?13 RE. According to the difference of the magnetic field structure in plasmoids,we choose two typical cases for our study: the magnetic flux rope on August 6 with the open magneticfield and the magnetic loop on September 14 with the closed magnetic field. Both of the cases are as-sociated with the high speed earthward flow and the magnetic loop is related to a strong substorm. Theions can escape from the magnetic flux rope along its open field line, but the case of the closed mag-netic loop can trap the ions. The earthward flowing plasmoids observed by TC-1 indicate that the mul-tiple X-line magnetic reconnection occurs beyond the distance of X=?10 RE from the earth.

关键词：磁层尾磁线圈焊接磁性

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The optimization model of the heat conduction structure

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Progress in Natural Science:Materials International 2008年第6期18卷 665-670页

作者： yongcun zhang,Shutian Liu* State Key Laboratory of Structural Analysis for Industrial Equipment,Department of Engineering Mechanics,Dalian University of Technology,Dalian 116024,China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian 116024 China

An optimization model considering a novel thermal performance index to be the objective function is proposed for minimizing the highest temperature in this ***,the performance of the conventional heat conduction optimization model,with the dissipation of heat transport potential capacity as the objective function,is evaluated by a one-dimensional heat conduction problem in a planar plate ***,a new thermal performance index,named the geometric average temperature,is *** new heat con-duction optimization model,with the geometric average temperature as the objective function,is developed and the corresponding finite element formula is *** results show that the geometric average temperature is an ideal thermal performance index and the solution of the new model is close to the theoretical optimal solution.

关键词： Optimization Heat conduction structure Dissipation of heat transport potential capacity Geometric average temperature Planar plate exchanger

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考虑瞬态温度和应力约束的承载隔热多功能结构拓扑优化

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力学学报 2023年第6期55卷 1288-1307页

作者：李帅张永存刘书田大连理工大学工业装备结构分析优化与CAE软件全国重点实验室辽宁大连116024

一体化热防护结构通常处于严酷的非稳态热环境,热载荷作用的时间效应(即瞬态热效应)明显.为了避免瞬态热分析的巨大计算消耗,以往的一体化热防护结构优化设计研究通常将瞬态传热等效为相同热边界条件下的稳态传热,将稳态传热分析的温度... 详细信息

一体化热防护结构通常处于严酷的非稳态热环境,热载荷作用的时间效应(即瞬态热效应)明显.为了避免瞬态热分析的巨大计算消耗,以往的一体化热防护结构优化设计研究通常将瞬态传热等效为相同热边界条件下的稳态传热,将稳态传热分析的温度场作为设计热载荷.然而,已有的研究表明稳态传热无法准确等效瞬态传热的作用效果,瞬态热效应对结构设计结果具有重要影响.文章研究了考虑瞬态热效应的一体化热防护结构优化设计问题,建立一种考虑瞬态温度和应力约束的一体化热防护结构拓扑优化方法.该方法以SIMP(solid isotropic material with penalization)法为基础,构建两种针对一体化热防护结构的热弹性结构拓扑优化模型:(1)考虑材料体积分数、最大应力和底面最大温度约束,以最小化结构应变能为目标的刚度设计模型;(2)考虑最大应力和底面最大温度约束,以最小化材料体积分数为目标的轻量化设计模型.通过求解瞬态热力耦合方程获得结构的热力耦合静力分析结果;通过响应量在空间和时间域的凝聚积分函数表征结构响应在时域内的最大值,并以此构建相应的约束和目标函数;采用伴随法推导约束和目标函数的灵敏度表达式.通过3个数值算例验证了本方法的有效性.数值算例结果表明,在瞬态传热条件下,本方法能够准确反映瞬态热效应对一体化热防护结构设计结果的影响;相比于基于稳态热分析的设计结果,考虑瞬态热效应的设计结果具有更优的性能.

关键词：一体化热防护结构拓扑优化瞬态传热温度和热应力约束

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Statistical analysis of relativistic electron precipitation in the magnetosphere from POES observations

Statistical analysis of relativistic electron precipitation ...

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2019年中国地球科学联合学术年会

作者： Huayue Chen Xinliang Gao Quanming Lu N.A.Tsyganenko yongcun zhang University of Science and Technology of China Saint Petersburg State University Department of Earth's Physics Saint Petersburg State University State Key Laboratory of Space Weather National Space Science Center

In this letter, we investigate the characters of relativistic electron precipitation(REP), which is derived from seven NOAA Polar-orbiting Operational Environmental Satellites(POES) in the time period from Jan 2012 to... 详细信息

关键词： Statistical analysis of relativistic electron precipitation in the magnetosphere from POES observations REP

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周期性复合材料等效传热系数预测的渐进均匀化新算法及其实现

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复合材料学报 2018年第1期35卷 208-217页

作者：张永存尚士朋梁宇静大连理工大学工程力学系工业装备结构分析国家重点实验室计算力学国际研究中心大连116023

渐进均匀化方法具有严格的数学基础,预测周期性复合材料的等效热传导系数具有较高的计算精度。本文提出了基于渐进均匀化方法预测周期性复合材料等效热传导系数的新算法。相比原有的算法具有两个优点:它的实现与代表体元方法一样简单,... 详细信息

渐进均匀化方法具有严格的数学基础,预测周期性复合材料的等效热传导系数具有较高的计算精度。本文提出了基于渐进均匀化方法预测周期性复合材料等效热传导系数的新算法。相比原有的算法具有两个优点:它的实现与代表体元方法一样简单,新的算法以现有的有限元商业软件为黑箱,通过简单的几个分析步骤,即可以获得复合材料的等效热传导系数;可以利用商业软件提供的多种单元类型去离散同一个单胞,在处理复杂几何单胞结构时,可以节约大量的计算费用。通过几个典型的算例,验证了方法的有效性。该工作对于推广渐进均匀化方法在预测复合材料等效热传导系数的广泛应用具有积极作用。

关键词：性能预测渐近均匀化方法等效热传导系数周期性复合材料材料设计

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考虑刚度特性的零热膨胀复合材料高许用温变设计

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复合材料学报 2021年第1期38卷 279-286页

作者：王炳达杨子豪张永存大连理工大学工业装备结构分析国家重点实验室大连116024

材料的宏观零热膨胀可以通过两种不同的正热膨胀材料在单胞尺度上的复合实现。该类材料虽然能在较大温度波动环境下保持较高的几何稳定性,但两种材料之间过大的热应力很容易导致材料失效,从而限制其许用温度变化范围(简称许用温变)。为... 详细信息

材料的宏观零热膨胀可以通过两种不同的正热膨胀材料在单胞尺度上的复合实现。该类材料虽然能在较大温度波动环境下保持较高的几何稳定性,但两种材料之间过大的热应力很容易导致材料失效,从而限制其许用温度变化范围(简称许用温变)。为此,提出以单位温升的最大热应力作为零热膨胀材料许用温变的衡量指标,通过解析和有限元数值仿真两种方法,对三种典型弯曲变形机制的零热膨胀材料进行许用温变和刚度特性分析,揭示了单胞可设计参数对其性能的影响规律。结果表明:在满足零热膨胀条件下,通过合理的单胞结构设计和选材设计,可以实现刚度与许用温变双目标共赢。

关键词：复合材料零热膨胀许用温变优化设计协同设计

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一种准确预测层合梁结构层间剪应力的新锯齿理论

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航空学报 2019年第11期40卷 129-142页

作者：杨胜奇张永存刘书田大连理工大学工程力学系工业装备结构分析国家重点实验室

层合梁是航空航天领域典型的承力构件,而过大的层间剪应力(层间处的横向剪应力)是导致其分层失效的主要原因。针对常见的层数较多的复合材料层合梁以及材料属性差异较大的三明治夹层梁,现有的理论模型仍然无法准确预测其横向剪应力。通... 详细信息

层合梁是航空航天领域典型的承力构件,而过大的层间剪应力(层间处的横向剪应力)是导致其分层失效的主要原因。针对常见的层数较多的复合材料层合梁以及材料属性差异较大的三明治夹层梁,现有的理论模型仍然无法准确预测其横向剪应力。通过构造一个新的线性分段锯齿函数,提出了一种能够准确预测层合梁结构横向剪应力的新锯齿理论模型。几个典型的数值算例表明,本文提出的新锯齿理论模型在计算层数较多和材料属性差异较大的层合梁时,具有较高的计算精度,能够准确预测层合梁的分层。另外,该模型预先满足横向剪应力层间连续条件,无需三维平衡方程后处理就能够准确预测层合梁的横向剪应力。位移场中未知量个数少,不含横向位移的一阶导,便于C0梁单元的构造。

关键词：锯齿理论层合梁夹层梁层间应力 Reissner混合变分原理

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