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期刊论文 9

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三维细观模拟 1

介观尺度模型 1

介观模型 1

劈拉试验 1

动态荷载 1

抗拉强度 1

支承垫片 1

数据挖掘 1

材料模型 1

激光选区熔化 1

环境压力 1

珊瑚混凝土 1

电子束选区熔化 1

界面特性 1

细观尺度建模 1

试件形状 1

输运现象 1

钢纤维混凝土 1

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用于介观模拟电子束选区熔化的数据挖掘技术 Article

钱亚, 闫文韬, 林峰

《工程(英文)》 2019年 第5卷 第4期   页码 746-754 doi: 10.1016/j.eng.2019.06.006

摘要:

 在电子束选区熔化技术(EBSM)工艺中,制造部件的性质受到每一道熔道沉积质量的影响。然而,熔道的形成受到各种物理现象和工艺参数的支配,这些参数之间的相关性十分复杂,难以通过实验得出。近来,介观建模技术已成为模拟电子束(EB)熔化过程以及揭示特定熔道形貌的形成机制的手段。尽管如此,人们对工艺参数与熔道特征之间的相关性尚未有定量的理解。本文从介观模拟的结果出发,研究了熔道的形态特征,同时引入了熔道宽度和高度等关键性描述指标,以便从数值上评估沉积质量。本文还定量研究了各种工艺参数的影响,从而导出了工艺条件和熔道特征之间的相关性。最后,本文提出了一种由介观建模和数据挖掘技术组成的仿真驱动优化框架,并讨论了框架的潜力和局限性。

关键词: 电子束选区熔化     介观模型     数据挖掘    

bottleneck of phosphonic acid anchoring groups aiming toward enhancing the stability and efficiency of mesoscopic

《化学科学与工程前沿(英文)》 2022年 第16卷 第7期   页码 1060-1078 doi: 10.1007/s11705-021-2117-z

摘要: Novel near-infrared sensitizers with different anchoring groups aiming toward improved stability and efficiency of dye-sensitized solar cells were synthesized. Adsorption of these dyes on the mesoporous TiO2 surface revealed the dye adsorption rate of –CH=CH–COOH (SQ-139)>–CH=C(CN)COOH (SQ-140)>–PO3H2 (SQ-143)>–CH=C(CN)PO3H2 (SQ-148)>–CH=C(CN)PO3H–C2H5 (SQ-157)>–PO3H–C2H5 (SQ-151)>–CH=CH–COOH(–PO3H2) (SQ-162). The binding strength of these dyes on mesoporous TiO2 as investigated by dye desorption studies follows SQ-162>SQ-143>SQ-148>SQ-139>SQ-157~SQ-151>SQ-140 order. The acrylic acid anchoring group was demonstrated to be an optimum functional group owing to its fast dye adsorption rate and better binding strength on TiO2 along with good photoconversion efficiency. Results of dye binding on TiO2 surface demonstrated that SQ-162 bearing double anchoring groups of phosphonic and acrylic acid exhibited>550 times stronger binding as compared to dye SQ-140 having cyanoacrylic acid anchoring group. SQ-140 exhibited the best photovoltaic performance with photon harvesting mainly in the far-red to near-infrared wavelength region having short circuit current density, open-circuit voltage and fill factor of 14.28 mA·cm–2, 0.64 V and 0.65, respectively, giving the power conversion efficiency of 5.95%. Thus, dye SQ-162 not only solved the problem of very poor efficiency of dye bearing only phosphonic acid while maintaining the extremely high binding strength opening the path for the design and development of novel near-infrared dyes with improved efficiency and stability by further increasing the π-conjugation.

关键词: anchoring groups     adsorption behaviour     dye-binding strength     squaraine dyes     dye-sensitized solar cells    

Effect of catalyst layer mesoscopic pore-morphology on cold start process of PEM fuel cells

Ahmed Mohmed DAFALLA, Fangming JIANG

《能源前沿(英文)》 2021年 第15卷 第2期   页码 460-472 doi: 10.1007/s11708-021-0733-4

摘要: Water transport is of paramount importance to the cold start of proton exchange membrane fuel cells (PEMFCs). Analysis of water transport in cathode catalyst layer (CCL) during cold start reveals the distinct characteristics from the normal temperature operation. This work studies the effect of CCL mesoscopic pore-morphology on PEMFC cold start. The CCL mesoscale morphology is characterized by two tortuosity factors of the ionomer network and pore structure, respectively. The simulation results demonstrate that the mesoscale morphology of CCL has a significant influence on the performance of PEMFC cold start. It was found that cold-starting of a cell with a CCL of less tortuous mesoscale morphology can succeed, whereas starting up a cell with a CCL of more tortuous mesoscale morphology may fail. The CCL of less tortuous pore structure reduces the water back diffusion resistance from the CCL to proton exchange membrane (PEM), thus enhancing the water storage in PEM, while reducing the tortuosity in ionomer network of CCL is found to enhance the water transport in and the water removal from CCL. For the sake of better cold start performance, novel preparation methods, which can create catalyst layers of larger size primary pores and less tortuous pore structure and ionomer network, are desirable.

关键词: cold start     energy conversion     fuel cells     mesoscale morphology     tortuosity     water management    

Numerical simulation of damage in high arch dam due to earthquake

Hong ZHONG , Gao LIN , Hongjun LI

《结构与土木工程前沿(英文)》 2009年 第3卷 第3期   页码 316-322 doi: 10.1007/s11709-009-0039-9

摘要: Based on the assumption that concrete is macroscopic homogeneous, the cracking evolution process and damage mode of high arch dams are studied in consideration of the heterogeneity of concrete in mesoscale. The bilinear damage evolution model and the damage evolution model expressed in power function with descending section are adopted to combine with the Mohr-Coulomb criterion to investigate the crack development and fracture mode of high arch dams under the action of an earthquake. The analysis result of a high arch dam in China under design shows that cracks that take place in concrete are caused by excessive tensile stress. The cracks initiate at the middle of the dam top and distribute at the upper half of the dam while the rest of the parts remain intact. This conclusion agrees with the model test result.

关键词: mesoscopic heterogeneity     damage simulation in earthquakes     arch dam    

Mesoscopic properties of dense granular materials: An overview

Qicheng SUN, Feng JIN, Guohua ZHANG

《结构与土木工程前沿(英文)》 2013年 第7卷 第1期   页码 1-12 doi: 10.1007/s11709-013-0184-z

摘要: A granular material is a conglomeration of discrete solid particles. It is intrinsically athermal because its dynamics always occur far from equilibrium. In highly excited gaseous states, it can safely be assumed that only binary interactions occur and a number of kinetic theories have been successfully applied. However, for granular flows and solid-like states, the theory is still poorly understood because of the internally correlated structures, such as particle clusters and force networks. The current theory is that the mesoscale characteristics define the key differences between granular materials and homogeneous solid materials. Widespread interest in granular materials has arisen among physicists, and significant progress has been made, especially in understanding the jamming phase diagram and the characteristics of the jammed phase. In this paper, the underlying physics of the mesoscale structure is discussed in detail. A multiscale framework is then proposed for dense granular materials.

关键词: granular matter     macroscopic structure     jamming phase transition    

考虑垫片形状和尺寸效应的珊瑚混凝土劈裂抗拉性能的三维细观研究 Article

吴彰钰, 张锦华, 余红发, 方秦, 麻海燕, 陈力

《工程(英文)》 2022年 第17卷 第10期   页码 110-122 doi: 10.1016/j.eng.2021.02.024

摘要:

珊瑚混凝土(CAC)作为一种新型建筑材料,已经在岛礁工程结构建设领域引起了极大的关注。为了研究CAC的静态劈裂抗拉性能,本文提出了一种考虑骨料形状和空间分布随机性的三维(3D)随机混凝土细观模型,影响因素包括试件形状和支承垫片尺寸。我们建立了12 个不同的混凝土细观模型,按照试件形状可分为两种,即边长为150 mm的立方体和尺寸为ϕ150 mm×300 mm的圆柱体。其中,支承垫片宽度为6 mm、9 mm、12 mm、15 mm、18 mm和20 mm。本文系统分析和讨论了试件几何形状和垫片宽度对CAC劈裂抗拉性能的影响规律,研究内容包括混凝土开裂过程、最终破坏模式和劈裂抗拉强度(fst)。结果表明:本文所开发的细观模型具有很高的可靠性,并确定了适用于CAC劈裂抗拉性能模拟和预测的最优计算参数。CAC的fst值与试件形状和垫片宽度直接相关。其中,在垫片尺寸相同的情况下,立方体CAC试件的fst值要略高于圆柱体模型,表明可以采用断裂面积的差异来解释试件形状效应对CAC fst值的影响规律。此外,当垫片的相对宽度由0.04 增加到0.13 时,CAC的fst值会呈现逐渐增大的趋势。基于弹性力学理论,本文初步确定了不同垫片宽度条件下CAC fst的取值范围,这对于研究CAC的抗拉性能具有重要意义。

关键词: 珊瑚混凝土     三维细观模拟     劈拉试验     抗拉强度     试件形状     支承垫片    

Modeling of alkali-silica reaction in concrete: a review

J.W. PAN, Y.T. FENG, J.T. WANG, Q.C. SUN, C.H. ZHANG, D.R.J. OWEN

《结构与土木工程前沿(英文)》 2012年 第6卷 第1期   页码 1-18 doi: 10.1007/s11709-012-0141-2

摘要: This paper presents a comprehensive review of modeling of alkali-silica reaction (ASR) in concrete. Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material. The concept of ASR and the mechanism of expansion are first outlined, and the state-of-the-art of modeling for ASR, the focus of the paper, is then presented in detail. The modeling includes theoretical approaches, meso- and macroscopic models for ASR analysis. The theoretical approaches dealt with the chemical reaction mechanism and were used for predicting pessimum size of aggregate. Mesoscopic models have attempted to explain the mechanism of mechanical deterioration of ASR-affected concrete at material scale. The macroscopic models, chemo-mechanical coupling models, have been generally developed by combining the chemical reaction kinetics with linear or nonlinear mechanical constitutive, and were applied to reproduce and predict the long-term behavior of structures suffering from ASR. Finally, a conclusion and discussion of the modeling are given.

关键词: alkali-silica reaction (ASR)     modeling     concrete     mesoscopic     macroscopic    

变环境压力下的激光选区熔化——介观尺度模型与输运现象 Article

胡仁志, 罗曼乐兰, 黄安国, 吴甲民, 魏青松, 文世峰, 张李超, 史玉升, Dmitry Trushnikov, V. Ya. Belenkiy, I. Yu. Letyagin, K.P. Karunakaran, 庞盛永

《工程(英文)》 2021年 第7卷 第8期   页码 1157-1164 doi: 10.1016/j.eng.2021.07.003

摘要:

近期研究表明,相比常压条件下,采用真空或低压环境的激光选区熔化(SLM)工艺可获得缺陷更少、表面质量更优的打印件。虽然通过高速摄像实验已经对SLM工艺在真空环境下的介观物理过程进行了部分研究,但该工艺下影响熔池传热和流动方面的深层机理仍不十分清楚。为此,基于最近的激光焊接模型工作,我们首次建立了变环境压力下SLM工艺的介观尺度数学模型。我们模拟了大气压和100 Pa低压环境下SLM工艺中316L粉末的输运现象。研究发现,在典型工艺参数(激光功率:200 W;扫描速度:2 ms-1;粉末直径:27 µm)下,大气环境中熔池表面凹坑的平均温度将近2800 K,而在100 Pa环境压力时,平均温度仅为2300 K。由于在100 Pa低压条件下,蒸发引起的表面压力和环境压力之间的压差相对于大气环境下的压差更大,更易驱动高温流体流动,因此熔池表面流动速度更加剧烈(平均速度约为4 m·s-1)。研究表明,熔池表面周期性的波浪流动(周期:14 µs)直接影响堆积体的表面粗糙度。此外,由于雷诺数小于400且远低于湍流临界值,熔融金属液流动模式为层流,因此,黏性耗散的影响至关重要。在真空或低环境压力条件下,波纹的流动轨迹更长,使得波动更容易由于黏性效应被耗散,从而改善了打印件的表面粗造度。总之,我们的数学模型阐明了变环境压力下SLM工艺实验研究中观察到的有趣输运现象的物理机制,它有望成为优化SLM工艺过程的有力工具。

关键词: 激光选区熔化     介观尺度模型     环境压力     输运现象    

动态荷载作用下钢纤维混凝土细观模拟方法及应用综述 Review

张锦华, 吴彰钰, 余红发, 麻海燕, 达波

《工程(英文)》 2022年 第16卷 第9期   页码 220-238 doi: 10.1016/j.eng.2022.01.011

摘要:

近年来钢纤维混凝土(SFRC)因对动态和冲击荷载具有优异力学响应而备受关注。现有的试验结果表明,嵌入混凝土基体中的高强度钢纤维具有很强的桥接效应,可以增强纤维与基体之间的结合力,有助于改善SFRC 开裂后性能和残余强度。为了更好地了解钢纤维在基体中的行为表现,以及进一步掌握SFRC在动态荷载作用下的失效机理,细观模拟方法已被广泛用于模拟SFRC材料和结构件的动态响应。细观模拟方法假设SFRC 由不同的细观组分组成,包括钢纤维、粗骨料、砂浆基体和界面过渡区(ITZ)。本文全面综述了动态荷载下SFRC的最新细观模型和模拟过程,系统对比了不同数值模拟研究中SFRC细观模型的生成方法,包括钢纤维、粗骨料及其之间的ITZ。全面总结了不同细观组分的材料模型及纤维与混凝土基体间的相互作用关系。此外,列举了不同动态荷载(即压缩、拉伸和接触爆炸)作用下SFRC细观模拟应用实例。最后,重点分析了现有SFRC细观模拟方法存在的不足,对于SFRC的未来研究及发展具有重要意义。

关键词: 钢纤维混凝土     细观尺度建模     动态荷载     材料模型     界面特性    

标题 作者 时间 类型 操作

用于介观模拟电子束选区熔化的数据挖掘技术

钱亚, 闫文韬, 林峰

期刊论文

bottleneck of phosphonic acid anchoring groups aiming toward enhancing the stability and efficiency of mesoscopic

期刊论文

Effect of catalyst layer mesoscopic pore-morphology on cold start process of PEM fuel cells

Ahmed Mohmed DAFALLA, Fangming JIANG

期刊论文

Numerical simulation of damage in high arch dam due to earthquake

Hong ZHONG , Gao LIN , Hongjun LI

期刊论文

Mesoscopic properties of dense granular materials: An overview

Qicheng SUN, Feng JIN, Guohua ZHANG

期刊论文

考虑垫片形状和尺寸效应的珊瑚混凝土劈裂抗拉性能的三维细观研究

吴彰钰, 张锦华, 余红发, 方秦, 麻海燕, 陈力

期刊论文

Modeling of alkali-silica reaction in concrete: a review

J.W. PAN, Y.T. FENG, J.T. WANG, Q.C. SUN, C.H. ZHANG, D.R.J. OWEN

期刊论文

变环境压力下的激光选区熔化——介观尺度模型与输运现象

胡仁志, 罗曼乐兰, 黄安国, 吴甲民, 魏青松, 文世峰, 张李超, 史玉升, Dmitry Trushnikov, V. Ya. Belenkiy, I. Yu. Letyagin, K.P. Karunakaran, 庞盛永

期刊论文

动态荷载作用下钢纤维混凝土细观模拟方法及应用综述

张锦华, 吴彰钰, 余红发, 麻海燕, 达波

期刊论文