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

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Frontiers in Energy 2016年第1期10卷 29-36页

作者： Yujie DING Jing LIU Key Lab of Cryogenics and Beijing Key Lab of CryoBiomedicalEngineering Technical Institute of Physics and Chemistry ChineseAcademy of Sciences Beijing 100190 China Key Lab of Cryogenics and Beijing Key Lab of CryoBiomedicalEngineering Technical Institute of Physics and Chemistry ChineseAcademy of Sciences Beijing 100190 Department of Biomedical Engineering School of Medicine Tsinghua University Beijing 100084China

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 inves- tigated 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

Partition method and experimental validation for impact dynamics of flexible multibody system

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Acta Mechanica Sinica 2018年第3期34卷 482-492页

作者： J.Y.Wang Z.Y.Liu J.Z.Hong School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one of the main difficulties in many engineering applications. The numerical approaches being used widely in impact analysis are mainly from two fields： multibody system dynamics （MBS） and computational solid mechanics （CSM）. Approaches based on MBS provide a more efficient yet less accurate analysis of the contact/impact problems, while approaches based on CSM are well suited for particularly high accuracy needs, yet require very high computational effort. To bridge the gap between accuracy and efficiency in the dynamic simulation of a flexible multibody system with contacts/impacts, a partition method is presented considering that the contact body is divided into two parts, an impact region and a non-impact region. The impact region is modeled using the finite element method to guarantee the local accuracy, while the non-impact region is modeled using the modal reduction approach to raise the global efficiency. A three-dimensional rod-plate impact experiment is designed and performed to validate the numerical results. The principle for how to partition the contact bodies is proposed： the maximum radius of the impact region can be estimated by an analytical method, and the modal truncation orders of the non-impact region can be estimated by the highest frequency of the signal measured. The simulation results using the presented method are in good agreement with the experimental results. It shows that this method is an effec-rive formulation considering both accuracy and efficiency. Moreover, a more complicated multibody impact problem of a crank slider mechanism is investigated to strengthen this conclusion.

关键词： Partition method impact dynamics Experimental investigation Efficiency and accuracy Partition principle

Initial Conditions of impact dynamics

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Journal of Shanghai Jiaotong university(Science) 2010年第3期15卷 368-371页

作者：董富祥洪嘉振朱焜余征跃 Department of Engineering Mechanics Shanghai Jiaotong University

The effects of the initial conditions of impact dynamics equations are investigated numerically and experimentally.The inadequacies of previous studies on initial conditions are pointed out.Then a coefficient of velocity jump at the moment of impact is introduced,and the experiments for the mental rods are implemented to validate the appending constraints modeling methods for impact process.The comparisons between the experimental and simulated results at different coefficients are used to study the effects of the velocity jump conditions to the numerical simulation.The results indicate that the physical velocity response of bodies during impact is smooth;the different values of velocity jump only have small effects on numerical oscillation of velocity response,and they have no effects on the time history of impact force.

关键词： impact dynamics velocity jump impact experiments numerical simulation

Partition method for impact dynamics of flexible multibody systems based on contact constraint

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Applied Mathematics and Mechanics(English Edition) 2013年第11期34卷 1393-1404页

作者：段玥晨章定国洪嘉振 School of Mechanical Engineering Zhengzhou University School of Science Nanjing University of Science and Technology Department of Engineering Mechanics Shanghai Jiao Tong University

The impact dynamics of a flexible multibody system is investigated. By using a partition method, the system is divided into two parts, the local impact region and the region away from the impact. The two parts are connected by specific boundary conditions, and the system after partition is equivalent to the original system. According to the rigid-flexible coupling dynamic theory of multibody system, system＇s rigid-flexible coupling dynamic equations without impact are derived. A local impulse method for establishing the initial impact conditions is proposed. It satisfies the compatibility con- ditions for contact constraints and the actual physical situation of the impact process of flexible bodies. Based on the contact constraint method, system＇s impact dynamic equa- tions are derived in a differential-algebraic form. The contact/separation criterion and the algorithm are given. An impact dynamic simulation is given. The results show that system＇s dynamic behaviors including the energy, the deformations, the displacements, and the impact force during the impact process change dramatically. The impact makes great effects on the global dynamics of the system during and after impact.

关键词： flexible multibody system impact dynamics partition method impulse-momentum method contact constraint

Modeling the dynamics of firms' technological impact

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Chinese Physics B 2021年第12期30卷 111-120页

作者：徐舒琪 Manuel Sebastian Mariani 吕琳媛 Yangtze Delta Region Institute(Huzhou)&Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaHuzhou 313001China University Research Priority Program on Social Networks University of ZurichCH-8050 ZurichSwitzerland Beijing Computational Science Research Center Beijing 100193China

Recent studies in complexity science have uncovered temporal regularities in the dynamics of impact along scientific and other creative careers, but they did not extend the obtained insights to firms. In this paper, we show that firms' technological impact patterns cannot be captured by the state-of-the-art dynamical models for the evolution of scientists' research impact, such as the Q model. Therefore, we propose a time-varying returns model which integrates the empiricallyobserved relation between patent order and technological impact into the Q model. The proposed model can reproduce the timing pattern of firms' highest-impact patents accurately. Our results shed light on modeling the differences behind the impact dynamics of researchers and firms.

关键词： firm technological impact patent analysis impact dynamics

Experimental study on anti-penetration mechanism of bolted composite protective structure with limited span under impact of low-velocity projectile

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Defence Technology（防务技术） 2022年第6期18卷 995-1005页

作者： Yu-jia Liu Dian Li Hai-liang Hou Zhu-jie Zhao Yue Xie College of Naval Architecture and Ocean Engineering Naval University of EngineeringWuhan430033China

In order to study the influence of the bolt joint mode on low-velocity projectiles penetrating the composite protective structure,two bolt joint models which connect the composite target to the fixed frame were designed,the ballistic test of the bolted composite protective structure with limited span was carried out,and the bearing and failure characteristics of the bolted region,as well as the energy dissipation of each part of the structure,were analyzed.The results show that in the condition of lowvelocity impact,there are three failure modes for the bolted composite protective structure subjected to projectile penetration,including failure of the impact point of the composite target,failure of protective structure connecting components and failure of the holes in the bolted region of the composite target;the failure mode of bolt holes in the bolted region has a great influence on the protection performance,and the allowable value of the bearing capacity of the bolted region depends on the sum of the minimum failure load in the failure modes and the friction force;shear-out failure occurring in the bolt holes in the bolted region exerts the greatest effect on ballistic performance,which should be avoided;When simultaneous failure occurs in the bolted region and the free deformation region of the composite protective structure,the energy absorption per unit surface density of the composite protective structure reaches the maximum,which can give full play to its anti-penetration efficiency.

关键词： impact dynamics Composite protective structure Bolt joint Ballistic test Failure modes

Theoretical analysis for self-sharpening penetration of tungsten high-entropy alloy into steel target with elevated impact velocities

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Acta Mechanica Sinica 2021年第6期37卷 970-982,I0002页

作者： Haihua Chen Xianfeng Zhang Chuang Liu Wei Xiong Mengting Tan Lan-Hong Dai School of Mechanical Engineering Nanjing University of Science&TechnologyXiaolingwei 200Nanjing210094China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Science University of Chinese Academy of SciencesBeijing101408China

The“self-sharpening”effect has been observed experimentally in the penetration of tungsten high-entropy alloy(WHEA)into steel targets in previous study.From the microscopic observation of the residual WHEA long-rod projectile(LRP),the multiphase structure at micro-scale of WHEA is the key effects on self-sharpening penetration process.In order to describe the distinctive penetration behavior,the interaction between micro phases is introduced to modify the hydrodynamic penetration model.The yield strengths of WHEA phases are determined based on the solid solution strengthening methods.Combined with the elbow-streamline model,the self-sharpening mechanism is revealed in view of the multi-phase flow dynamics and the flow field in the deformation area of the LRP nose is characterized to depict the shear layer evolution and the shape of the LRP’s nose as well as the determination of the penetration channel.The self-sharpening coefficient considering the reduction of nose radius is proposed and introduced into the penetration model to calculate the depth of penetration and the penetration channel.Results show that the multi-phase interaction at the microscopic level contributes to the inhomogeneous distribution of the WHEA phases.The shear layer evolution separates part of the LRP material from the nose and makes the nose radius decrease more quickly.It is also the reason that WHEA LRPs have a pointed nose compared with the mushroom nose of WHA heavy alloy(WHA)LRPs.The calculated results agree well with the corresponding experimental data of WHA and WHEA LRPs penetrating into semi-infinite medium carbon steel targets with elevated impact velocities.

关键词： impact dynamics Long-rod projectile Tungsten high-entropy alloy(WHEA) Self-sharpening penetration Solid solution strengthening