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Hazard potential of zones of weakness in gravity dams under impact loading conditions

Herbert LINSBAUER

《结构与土木工程前沿(英文)》 2011年 第5卷 第1期   页码 90-97 doi: 10.1007/s11709-010-0008-3

摘要: Dam constructions worldwide are designed and constructed in view of the strictest safety aspects for all static and dynamic load cases. As experience shows, however, formation of cracks in the “homogeneos concrete” as well as unsatisfactory compound behavior of lift joints are not to be excluded. These zones of weakness especially on the upstream side of the dam— exposed to high water pressure (static and dynamic)— represent an increased risk of safety. The main investigation, apart from the computation of the dynamic effects on the dam as a global structure, focuses on the stability analysis of a pressure-water filled crack configuration subjected to “dynamic loading” in the form of seismic action on the dam-reservoir-system and alternatively by “impact spot-loading” within sectors of the reservoir. A fracture mechanics based analysis shows an excessive potential of damage for the afflicted structure.

关键词: dam-reservoir     earthquake     impact     cracking     fracture mechanics    

Parameter studies on impact in a lap joint

Amir M. RAHMANI,Elizabeth K. ERVIN

《机械工程前沿(英文)》 2015年 第10卷 第1期   页码 64-77 doi: 10.1007/s11465-014-0322-x

摘要:

To represent a loose lap joint, a beam impacting four springs with gaps is modeled. Modal analysis with base excitation is solved, and time histories of contact points are closely monitored. Using the impulse during steady state response, six influential parameters are studied: damping ratio, contact stiffness, intermediate contact position, gap, excitation amplitude and beam height. For all parameters, the system response is highly controlled by modes with two contacting springs. Each parameter’s effect on system response is presented including unstable regions, unique trend behaviours result. Recommendations for structural designers are also noted.

关键词: impact mechanics     contact     joint behaviour     modal analysis     parameter study    

Water film coated composite liquid metal marble and its fluidic impact dynamics phenomenon

Yujie DING,Jing LIU

《能源前沿(英文)》 2016年 第10卷 第1期   页码 29-36 doi: 10.1007/s11708-015-0388-0

摘要: A composite liquid metal marble made of metal droplet coated with water film was proposed and its impact dynamics phenomenon was disclosed. After encapsulating the liquid metal into water droplets, the fabricated liquid marble successfully avoided being oxygenized by the metal fluid and thus significantly improved its many physical capabilities such as surface tension modification and shape control. The striking behaviors of the composite liquid metal marbles on a substrate at room temperature were experimentally investigated in a high speed imaging way. It was disclosed that such marbles could disintegrate, merge, and even rebound when impacting the substrate, unlike the existing dynamic fluidic behaviors of liquid marble or metal droplet. The mechanisms lying behind these features were preliminarily interpreted. This fundamental finding raised profound multiphase fluid mechanics for understanding the complex liquid composite which was also critical for a variety of practical applications such as liquid metal jet cooling, inkjet printed electronics, 3D printing or metal particle fabrication etc.

关键词: liquid metal marble     metallic droplet     composite fluid     impact dynamics     multiphase fluid mechanics    

Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

《结构与土木工程前沿(英文)》 2021年 第15卷 第3期   页码 623-642 doi: 10.1007/s11709-021-0726-8

摘要: In this study, gradual and sudden reduction methods were combined to simulate a progressive failure in notched composite plates using a macro mechanics approach. Using the presented method, a progressive failure is simulated based on a linear softening law prior to a catastrophic failure, and thereafter, sudden reduction methods are employed for modeling a progressive failure. This combination method significantly reduces the computational cost and is also capable of simultaneously predicting the first and last ply failures (LPFs) in composite plates. The proposed method is intended to predict the first ply failure (FPF), LPF, and dominant failure modes of carbon/epoxy and glass/epoxy notched composite plates. In addition, the effects of mechanical properties and different stacking sequences on the propagation of damage in notched composite plates were studied. The results of the presented method were compared with experimental data previously reported in the literature. By comparing the numerical and experimental data, it is revealed that the proposed method can accurately simulate the failure propagation in notched composite plates at a low computational cost.

关键词: progressive failure     notched composite plate     Hashin failure criterion     macro mechanics approach     finite element method    

航空航天技术与力学

陈士橹

《中国工程科学》 2003年 第5卷 第3期   页码 25-26

摘要:

文章论述了航空航天技术发展与力学学科发展的依存关系,讨论了力学学科间的交叉及交叉学科的产生,重点介绍了飞行力学与空气动力学、结构力学、一般力学、自动控制等学科间的关系,进而讨论了飞行力学的分支——弹性飞行器动力学。

关键词: 空气动力学     结构力学     一般力学     自动控制     飞行力学     弹性飞行器动力学    

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

《机械工程前沿(英文)》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0702-6

摘要: The creep life of an aeroengine recuperator is investigated in terms of continuum damage mechanics by using finite element simulations. The effects of the manifold wall thickness and creep properties of brazing filler metal on the operating life of the recuperator are analyzed. Results show that the crack initiates from the brazing filler metal located on the outer surface of the manifold with the wall thickness of 2 mm and propagates throughout the whole region of the brazing filler metal when the creep time reaches 34900 h. The creep life of the recuperator meets the requirement of 40000 h continuous operation when the wall thickness increases to 3.5 mm, but its total weight increases by 15%. Decreasing the minimum creep strain rate with the enhancement of the creep strength of the brazing filler metal presents an obvious effect on the creep life of the recuperator. At the same stress level, the creep rupture time of the recuperator is enhanced by 13 times if the mismatch between the minimum creep rate of the filler and base metal is reduced by 20%.

关键词: creep     life assessment     brazed joint     continuum damage mechanics     aeroengine recuperator    

Study of the mechanics of progressive collapse of FPB isolated beam-pier substructures

Jingcai ZHANG; Yong DING; Xinchun GUAN

《结构与土木工程前沿(英文)》 2022年 第16卷 第6期   页码 718-728 doi: 10.1007/s11709-022-0815-3

摘要: The horizontal stiffness of the isolated layer is reduced substantially by a friction pendulum bearing (FPB) toprotectthe structure from potential damages caused by earthquakes. However, horizontal stiffness is essential to progressive collapse resistance of structures. This paper presents a simplified model to assess the progressive collapse response of beam-pier substructure isolated by FPB. Progressive collapse resistance by flexural action of the beam and additional resistance owing to the horizontal restraining force was achieved. The influences of the equivalent radius and friction coefficient of the FPB, the applied axial force on the FPB, and span-depth ratio of the beam on the additional resistance were investigated. Simulations were conducted to verify the proposed model. The results show that progressive collapse resistance provided by horizontal restraining can be reduced as large as 46% and 88% during compressive arching action (CAA) and catenary action (CA), respectively. The equivalent radius of the FPB shows limited effect on the progressive collapse response of FPB isolated structures, but friction coefficient and applied axial force, as well as depth ratio of the beam, show significant influences on the additional progressive collapse resistance capacity. Finite element method (FEM) results are in good agreement with the result obtained by the proposed method.

关键词: friction pendulum bearing     progressive collapse     horizontal stiffness     compressive arching action     catenary action    

Advances in structural mechanics of Chinese ancient architectures

YU Maohong, ODA Yoshiya, FANG Dongping, ZHAO Junhai

《结构与土木工程前沿(英文)》 2008年 第2卷 第1期   页码 1-25 doi: 10.1007/s11709-008-0002-1

摘要: Chinese ancient architectures are valuable heritage of ancient culture of China. Many historical building have been preserved up to now. The researches on the structural mechanics of ancient architectures show the different aspects of structure and mechanics. Systematical studies on the structural mechanics of ancient architectures have been carried out at Xi’an Jiaotong University since 1982. It is related with the need of repair of some national preservation relics in Xi’an. These studies include: 1) Ancient wooden structures including three national preservation relics Arrow Tower at North City Gate, City Tower at East City Gate, and Baogao Temple in Ningbao, Zhejiang province. 2) Ancient tall masonry building, the Big Goose Pagoda and Small Goose Pagoda in Xi’an. 3) Mechanical characteristics of ancient soil under foundation and city wall; the influence of caves in and under the ancient City Wall on the stability of the wall. 4) The typical Chinese ancient building at the center of city: the Bell Tower and Drum tower. 5) The behavior of Dou-Gong and Joggle joint of Chinese ancient wooden structure. 6) The mechanical behavior of ancient soils under complex stress state. A new systematical strength theory, the unified strength theory, is used to analyze the stability of ancient city wall in Xi’an and foundation of tall pagoda built in Tang dynasty. These researches also concern differential settlements of Arrow Tower and resistance to earthquake of these historical architecture heritages. Some other studies are also introduced. This paper gives a summary of these researches. Preservation and research are nowadays an essential requirement for the famous monuments, buildings, towers and others. Our society is more and more conscious of this necessity, which involves increasing activities of restoration, and then sometimes also of repair, mechanical strengthening and seismic retrofitting. Many historical buildings have in fact problems of structural strength and stability; the need for further studies on structural mechanics and materials is definitely growing.

广义塑性力学及其运用

郑颖人,孔亮

《中国工程科学》 2005年 第7卷 第11期   页码 21-36

摘要:

分析了经典塑性力学用于岩土类材料的问题,它采用了3个不符合岩土材料变形机制的假设。从固体力学原理直接导出广义塑性位势理论,将经典塑性力学改造为更一般的塑性力学——广义塑性力学。广义塑性力学采用了塑性力学中的分量理论,能反映应力路径转折的影响,并避免了采用正交流动法则所引起的过大剪胀等不合理现象,也不会产生当前非关联流动法则中任意假定塑性势面引起的误差。给出了广义塑性力学的屈服面理论、硬化定律和应力-应变关系,并建立了考虑应力主轴旋转的广义塑性位势理论。屈服条件是状态参数,也是试验参数,只能由试验给出。应用表明,广义塑性力学可作为岩土材料的建模理论,还可应用于诸如极限分析等土力学的诸多领域,具有广阔的应用前景。

关键词: 岩土塑性力学     广义塑性力学     塑性势     屈服面     本构模型    

A computational toolbox for molecular property prediction based on quantum mechanics and quantitative

《化学科学与工程前沿(英文)》 2022年 第16卷 第2期   页码 152-167 doi: 10.1007/s11705-021-2060-z

摘要: Chemical industry is always seeking opportunities to efficiently and economically convert raw materials to commodity chemicals and higher value-added chemical-based products. The life cycles of chemical products involve the procedures of conceptual product designs, experimental investigations, sustainable manufactures through appropriate chemical processes and waste disposals. During these periods, one of the most important keys is the molecular property prediction models associating molecular structures with product properties. In this paper, a framework combining quantum mechanics and quantitative structure-property relationship is established for fast molecular property predictions, such as activity coefficient, and so forth. The workflow of framework consists of three steps. In the first step, a database is created for collections of basic molecular information; in the second step, quantum mechanics-based calculations are performed to predict quantum mechanics-based/derived molecular properties (pseudo experimental data), which are stored in a database and further provided for the developments of quantitative structure-property relationship methods for fast predictions of properties in the third step. The whole framework has been carried out within a molecular property prediction toolbox. Two case studies highlighting different aspects of the toolbox involving the predictions of heats of reaction and solid-liquid phase equilibriums are presented.

关键词: molecular property     quantum mechanics     quantitative structure-property relationship     heat of reaction     solid-liquid phase equilibrium    

环境友好型全水压冲击凿岩机动力学建模与数值仿真

岳文辉,刘德顺,伍先明,朱萍玉,李夕兵

《中国工程科学》 2007年 第9卷 第8期   页码 57-61

摘要:

介绍了以普通水作为传动、支撑推进、排屑和润滑介质的环境友好型全水压凿岩机;建立了以弹性杆、弹簧为基本单元的冲击凿岩机 波动力学模型;对YST–25全水压凿岩机进行了动态数值仿真与分析。研究结果表明:活塞最大压应力为102 MPa,最大拉应力为28 MPa,满足 了强度设计要求;钎杆中的应力比活塞的大;尽量减小活塞的截面积变化有利于延长活塞寿命;为了保证凿岩速度和能量传递效率,YST–25凿 岩机宜于在中硬到硬岩中钻进。这为环境友好型全水压冲击凿岩机的改进设计和效能评估提供了依据。

关键词: 冲击     波动力学     仿真     水压凿岩机    

钱学森与力学

谈庆明

《中国工程科学》 2001年 第3卷 第10期   页码 1-6

摘要:

介绍了钱学森先生在近代力学和技术科学发展中的贡献,特别是介绍了他为实现超声速飞行和火箭技术在一系列关键问题上所做的贡献。在研究过程中他不断开创出工程控制论、物理力学和喷气推进学等新的技术科学,从而促进了航空航天技术的飞跃发展。我们要学习体现在他身上的超前意识和务实精神,学习、理解并大力开展他所倡导的技术科学的研究工作。

关键词: 钱学森     力学     技术科学    

Analysis of actuating mechanics characteristics for a flexible miniature robot system

YU Lianzhi, YAN Guozheng, MA Guanying, ZAN Peng

《机械工程前沿(英文)》 2008年 第3卷 第1期   页码 66-70 doi: 10.1007/s11465-008-0006-5

摘要: Based on the inchworm movement, a miniature endoscope inspection robot system with a flexible structure is designed. The system is actuated by a pneumatic rubber actuator with three degrees of freedom, and it holds its position by air chambers. The actuating mechanics characteristics of the robot are analyzed. An electro-pneumatic pressure system is designed to control the motion of the robot. Results of the calculation and experiments are consistent, and the robot system can move smoothly in a soft tube.

关键词: calculation     consistent     endoscope inspection     electro-pneumatic     miniature endoscope    

矿山岩体力学及工程的研究进展与展望

谢和平

《中国工程科学》 2003年 第5卷 第3期   页码 31-38

摘要:

文章针对采矿工程的实际问题,综述了矿山岩体力学理论与应用的研究进展,主要内容包括矿山岩体力学的损伤研究与应用、矿山岩体力学的分形研究与应用和矿山岩体力学损伤与分形研究的工程应用;讨论了矿山岩体力学今后的研究方向,即深部开采带来的工程灾害防治、开采方法选择的科学问题与关键技术措施。

关键词: 矿山岩体力学     研究现状     展望    

Game theoretic analysis of environmental impact assessment system in China

CHENG Hongguang, PU Xiao, GONG Li, QI Ye

《环境科学与工程前沿(英文)》 2007年 第1卷 第4期   页码 448-453 doi: 10.1007/s11783-007-0071-8

摘要: Environmental impact assessment (EIA) system has been established in China since 1973. In present EIA cases, there are four participants in general: governments, enterprises, EIA organizations and the public. The public has held re

关键词: public     impact assessment     Environmental impact     general    

标题 作者 时间 类型 操作

Hazard potential of zones of weakness in gravity dams under impact loading conditions

Herbert LINSBAUER

期刊论文

Parameter studies on impact in a lap joint

Amir M. RAHMANI,Elizabeth K. ERVIN

期刊论文

Water film coated composite liquid metal marble and its fluidic impact dynamics phenomenon

Yujie DING,Jing LIU

期刊论文

Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

期刊论文

航空航天技术与力学

陈士橹

期刊论文

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

期刊论文

Study of the mechanics of progressive collapse of FPB isolated beam-pier substructures

Jingcai ZHANG; Yong DING; Xinchun GUAN

期刊论文

Advances in structural mechanics of Chinese ancient architectures

YU Maohong, ODA Yoshiya, FANG Dongping, ZHAO Junhai

期刊论文

广义塑性力学及其运用

郑颖人,孔亮

期刊论文

A computational toolbox for molecular property prediction based on quantum mechanics and quantitative

期刊论文

环境友好型全水压冲击凿岩机动力学建模与数值仿真

岳文辉,刘德顺,伍先明,朱萍玉,李夕兵

期刊论文

钱学森与力学

谈庆明

期刊论文

Analysis of actuating mechanics characteristics for a flexible miniature robot system

YU Lianzhi, YAN Guozheng, MA Guanying, ZAN Peng

期刊论文

矿山岩体力学及工程的研究进展与展望

谢和平

期刊论文

Game theoretic analysis of environmental impact assessment system in China

CHENG Hongguang, PU Xiao, GONG Li, QI Ye

期刊论文