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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

Nanocrystalline Silicon Thin Films Fabricated at 80℃ by Using Electron Cyclotron Resonance Chemical Vapor Deposition

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Plasma Science and Technology 2010年第5期12卷 608-613页

作者： I.y.y.BU A.J.FLEWITT W.I.MILINE Department of Microelectronics Engineering National Kaohsiung Marine University Electrical Engineering Division Engineering Department Cambridge University

Deposition of nanocrystalline silicon （nc-Si） on glass at very low temperatures by electron cyclotron resonance （ECR） plasma enhanced chemical vapour deposition （PECVD） was investigated. It was shown that nc-Si could be deposited from hydrogen diluted silane gas at a substrate temperature of 80℃ with a crystalline fraction up to 80% and a lateral grain size of around 50 nm. This was achieved by growing the nc-Si in a low pressure regime which ensured that mono-silyl species were the dominant deposition precursor. Furthermore, a high flux of energetic hydrogen ions was required to induce crystallisation of the silicon material through a chemical annealing process.

关键词： low temperature nanocrystalline silicon ECR

Variations of properties across plate thickness for Al alloy 7010

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中国有色金属学会会刊：英文版 2005年第6期15卷 1258-1263页

作者： M.Salazar-Guapuriche y.y.Zhao A.Pitman A.Greene Materials Laboratory Airbus UK Broughton Chester CH4 0DR UKDepartment of Engineering The University of Liverpool Liverpool L69 3GH UK Department of Engineering The University of Liverpool Liverpool L69 3GH UK Materials and Process Group Airbus UK Filton Bristol BS99 7AR UK

The variations of electrical conductivity and hardness across the thickness of an Al alloy 7010 plate under the temper condition T7651 were investigated. The electrical conductivity and hardness respond in a reciprocal manner. Cross-sectional slices of the plate subjected to re-solutionising/natural ageing and re-solutionising/artificial ageing show the similar tendencies in property changes as in the as-received raw material. This clearly suggests that the property inhomogeneity across the plate thickness is inherent of the manufacturing route. The differences in properties through the plate thickness are due to the changes in the concentrations of the strengthening alloying elements in the solid solution and the associated changes in microstructure; these are believed to be mainly due to the nature of plate solidification and prolonged high temperature during the rolling operation. The combination of electrical conductivity and hardness can be used as an integral quality property indicator for assessing inhomogeneity of thick products.

关键词：铝合金镀层厚度硬度导电性

High-Speed Friction Stir Welding of T6-Treated B4Cp/6061Al Composite

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 67-74页

作者： y.Z.Li y.N.Zan Q.Z.Wang B.L.Xiao Z.y.Ma Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and Technology of China Shenyang 110016China

T6-treated 20 wt% B4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(NZ) of the joints, the B4 C particles were broken up and uniformly redistributed. The NZ exhibited lower hardness than the base metal(BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

Multi-place physics and multi-place nonlocal systems

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Communications in Theoretical Physics 2020年第5期72卷 120-132页

作者： S y Lou School of Physical Science and Technology Ningbo UniversityNingbo315211China

Multi-place nonlocal systems have attracted attention from many *** this paper,we mainly review the recent progresses on two-place nonlocal systems(Alice-Bob systems)and four-place nonlocal ***-place systems can firstly be derived from many physical problems by using a multiple scaling method with a discrete symmetry group including parity,time reversal,charge conjugates,rotations,field reversal and exchange *** nonlocal systems can also be derived from the symmetry reductions of coupled nonlinear systems via discrete symmetry *** the other hand,to solve multi-place nonlocal systems,one can use the symmetry-antisymmetry separation approach related to a suitable discrete symmetry group,such that the separated systems are coupled local *** using the separation method,all the known powerful methods used in local systems can be applied to nonlocal *** this review article,we take two-place and four-place nonlocal nonlinear Schr?dinger(NLS)systems and Kadomtsev-Petviashvili(KP)equations as simple examples to explain how to derive and solve *** types of novel physical and mathematical points related to the nonlocal systems are especially emphasized.

关键词： multi-place physics multi-place nonlocal systems symmetries integrable systems parity and time reversal soliton theory classical prohibitions

A novel supercapacitor-fuel cell hybrid cell

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Rare Metals 2006年第z1期25卷 12-18页

作者： WANG y ZHENG Jim P Department of Electrical and Computer Engineering Florida A&M University and Florida State University Tallahassee FL 32310 USA Department of Electrical and Computer Engineering Florida A&M University and Florida State University Tallahassee FL 32310 USA

A monolithic hybrid fuel cell (MHFC) with a novel configuration was proposed in an effort to improve the fuel cell performance during instantaneous power changes. A modified direct methanol fuel cell (DMFC) with a layer of hydrous ruthenium dioxide (RuO2·xH2O) sandwiched between the anode catalyst layer and membrane was used to demonstrate the principle of the MHFC. Experimental results indicate that the RuO2·xH2O layer is equivalent to a resistor-capacitor transmission line and functions similar to a capacitor in parallel with the anode electrode. The improvement in dynamic response of the MHFC was experimentally confirmed under step current change and square current pulse operating. The ionic conductivity of the RuO2·xH2O layer was also obtained.

关键词： hybrid devices direct methanol fuel cells hydrous ruthenium dioxide dynamic response

Neumann＇s method for boundary problems of thin elastic shells

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 543-556页

作者： y. S. NEUSTADT Department of Civil Engineering Samara State Architectural and Building University Samara 443001 Russia

The possibility of using Neumann＇s method to solve the boundary problems for thin elastic shells is studied. The variational statement of the static problems for the shells allows for a problem examination within the distribution space. The convergence of Neumann＇s method is proven for the shells with holes when the boundary of the domain is not completely fixed. The numerical implementation of Neumann＇s method normally requires significant time before any reliable results can be achieved. This paper suggests a way to improve the convergence of the process, and allows for parallel computing and evaluation during the calculations.

关键词： boundary problem thin elastic shell theory Neumann's method variational principle Korn's inequality distribution embedding theorem Green tensor

THEORy OF WATER WAVES IN AN ELASTIC VESSEL

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Acta Mechanica Sinica 2000年第2期16卷 97-112页

作者： D. y. Hsieh Division of Applied Mathematics Brown University USA

Recent experiments related to the Dragon Wash phenomena showed that axisymmetric capillary waves appear first from excitation, and circumferential capillary waves appear after increase of the excitation strength. Based on this new finding, a theory of parametric resonance is developed in detail to explain the on- set of the prominent circumferential capillary waves. Numerical computation is also carried out and the results agree generally with the experiments. Analysis and nu- merical computation are also presented to explain the generation of axisymmetric low-frequency gravity waves by tile high-frequency external excitation.

关键词： water waves elastic vessel Dragon Wash

Enhancing volumetric muscle loss(VML)recovery in a rat model using super durable hydrogels derived from bacteria

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Bioactive Materials 2024年第8期38卷 540-558页

作者： Seyyed Vahid Niknezhad Mehdi Mehrali Farinaz Riyahi Khorasgani Reza Heidari Firoz Babu Kadumudi Nasim Golafshan Miguel Castilho Cristian Pablo Pennisi Masoud Hasany Mohammadjavad jahanshahi Mohammad Mehrali younes Ghasemi Negar Azarpira Thomas L.Andresen Alireza Dolatshahi-Pirouz Burn and Wound Healing Research Center Shiraz University of Medical SciencesShiraz71987-54361Iran Department of Civil and Mechanical Engineering Technical University of Denmark2800Kgs LyngbyDenmark Department of Health Technology Technical University of Denmark2800Kongens LyngbyDenmark Pharmaceutical Sciences Research Center Shiraz University of Medical SciencesShirazIran Department of Orthopaedics University Medical Center UtrechtUtrecht3584 CXthe Netherlands Department of Biomedical Engineering Eindhoven University of Technologythe Netherlands Regenerative Medicine Group Department of Health Science and TechnologyAalborg University9260GistrupDenmark Department of Chemistry Faculty of ScienceUniversity of Jiroft***JiroftIran Faculty of Engineering Technology Department of Thermal and Fluid Engineering(TFE)University of Twente7500 AEEnschedethe Netherlands Transplant Research Center Shiraz University of Medical SciencesShirazIran Institute for Complex Molecular Systems Eindhoven University of TechnologyEindhoventhe Netherlands Department of Health Technology Section for Biotherapeutic Engineering and Drug TargetingTechnical University of Denmark2800Kongens LyngbyDenmark

Bacteria can be programmed to deliver natural materials with defined biological and mechanical properties for controlling cell growth and ***,we present an elastic,resilient and bioactive polysaccharide derived from the extracellular matrix of Pantoea *** ***,it was methacrylated to generate a new photo crosslinkable hydrogel that we coined Pantoan Methacrylate or put simply *** have used it for the first time as a tissue engineering hydrogel to treat VML injuries in *** crosslinked PAMA hydrogel was super elastic with a recovery nearing 100%,while mimicking the mechanical stiffness of native *** inclusion of thiolated gelatin via a Michaelis reaction with acrylate groups on PAMA we could also guide muscle progenitor cells into fused and aligned tubes-something reminiscent of mature muscle *** results were complemented by sarcomeric alpha-actinin immunostaining ***,the implanted hydrogels exhibited almost 2-fold more muscle formation and 50%less fibrous tissue formation compared to untreated rat *** vivo inflammation and toxicity assays likewise gave rise to positive results confirming the biocompatibility of this new biomaterial ***,our results demonstrate that programmable polysaccharides derived from bacteria can be used to further advance the field of tissue *** greater detail,they could in the foreseeable future be used in practical therapies against VML.

关键词： hydrogel simply fused