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Geometric nonlinear formulation for thermal-rigid-flexible coupling system

Acta Mechanica Sinica 2013年第5期29卷 728-737页

作者： Wei Fan jin-yang liu School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

This paper develops geometric nonlinear hybrid formulation for flexible multibody system with large deformation considering thermal effect. Different from the conventional formulation, the heat flux is the function of the rotational angle and the elastic deformation, therefore, the coupling among the temperature, the large overall motion and the elastic deformation should be taken into account. Firstly, based on nonlinear strain-displacement relationship, varia- tional dynamic equations and heat conduction equations for a flexible beam are derived by using virtual work approach, and then, Lagrange dynamics equations and heat conduction equations of the first kind of the flexible multibody system are obtained by leading into the vectors of Lagrange multiplier associated with kinematic and temperature constraint equations. This formulation is used to simulate the thermal included hub-beam system. Comparison of the response be- tween the coupled system and the uncoupled system has re- vealed the thermal chattering phenomenon. Then, the key parameters for stability, including the moment of inertia of the central body, the incident angle, the damping ratio and the response time ratio, are analyzed. This formulation is also used to simulate a three-link system applied with heat flux. Comparison of the results obtained by the proposed formulation with those obtained by the approximate nonlinear model and the linear model shows the significance of con- sidering all the nonlinear terms in the strain in case of large deformation. At last, applicability of the approximate non- linear model and the linear model are clarified in detail.

关键词： Thermal-rigid-flexible coupling - Thermal chattering Large deformation Stability analysis

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Investigation on the choice of boundary conditions and shape functions for flexible multi-body system

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Acta Mechanica Sinica 2012年第1期28卷 180-189页

作者： Ke-Qi Pan jin-yang liu School of Naval Architecture Ocean and Civil EngineeringShanghai Jiaotong University200240 ShanghaiChina

The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems. The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference （FFR） formulation. The deformations obtained by the absolute nodal coordinate （ANC） formulation which are transformed by two sets of reference coordinates are introduced as a criterion to verify the accuracy of the simulation results by using the FFR formulation. The relationship between the deformations obtained from different boundary conditions is revealed. Nu- merical simulation examples demonstrate that the assumed modes with cantilevered-free, simply-supported and free- free boundary conditions without inclusion of rigid body modes are suitable for simulation of flexible multi-body system with large over all motion, and the same physical deformation can be obtained using those mode functions, differ only by a coordinate transformation. It is also shown that when using mode shapes with statically indeterminate boundary conditions, significant error may occur. Furthermore, the slider crank mechanism with rigid crank is accurate enough for investigating boundary condition problem of flexible multi-body system, which cost significant less simulating time.

关键词： Multi-body systems. Boundary conditions - Assumed mode approach

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Geometric nonlinear dynamic analysis of curved beams using curved beam element

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Acta Mechanica Sinica 2011年第6期27卷 1023-1033页

作者： Ke-Qi Pan jin-yang liu School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University 200240 Shanghai China

Instead of using the previous straight beam element to approximate the curved beam,in this paper,a curvilinear coordinate is employed to describe the deformations,and a new curved beam element is proposed to model the curved *** on exact nonlinear strain-displacement relation,virtual work principle is used to derive dynamic equations for a rotating curved beam,with the effects of axial extensibility,shear deformation and rotary inertia taken into *** constant matrices are solved numerically utilizing the Gauss quadrature integration *** and Newton-Raphson iteration methods are adopted to solve the differential equations of the rigid-flexible coupling *** present results are compared with those obtained by commercial programs to validate the present finite *** order to further illustrate the convergence and efficiency characteristics of the present modeling and computation formulation,comparison of the results of the present formulation with those of the ADAMS software are ***,the present results obtained from linear formulation are compared with those from nonlinear formulation,and the special dynamic characteristics of the curved beam are concluded by comparison with those of the straight beam.

关键词： Curved beam element. Geometric nonlinear formulation Rigid-flexible coupling

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A new subregion mesh method for the investigation of the elastic-plastic impact in flexible multibody systems

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Acta Mechanica Sinica 2017年第1期33卷 189-199页

作者： Peng Chen jin-yang liu Guang-Can Lu Department of Engineering Mechanics School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai 200240 China

Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the local plastic deformation and the strict requirements of the spatial discretization. Owing to the nonlinearity of the stiffness matrix, the reduction of the element number is extremely important. For the contact-impact problem, since different regions have different requirements regarding the element size, a new subregion mesh method is proposed to reduce the number of the unnecessary elements. A dynamic model for flexible multibody systems with elastic-plastic contact impact is established based on a floating frame of reference formulation and complete Lagrange incremental nonlinear finite-element method to investigate the effect of the elastic-plastic deformation as well as spatial discretization. Experiments on the impact between two bodies are carried out to validate the correctness of the elastic-plastic model. The proposed formulation is applied to a slider-crank system with elastic-plastic impact.

关键词： Multibody dynamics Elastic-plastic impact Subregion mesh method Experiment

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Contact-impact formulation for multi-body systems using component mode synthesis

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Acta Mechanica Sinica 2013年第3期29卷 437-442页

作者： Peng Chen jin-yang liu Jia-Zhen Hong Department of Engineering Mechanics School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University

The efficiency and accuracy are two most concerned issues in the modeling and simulation of multi-body systems involving contact and impact. This paper proposed a formulation based on the component mode synthesis method for planar contact problems of flexible multi-body systems. A flexible body is divided into two parts： a contact zone and an un-contact zone. For the un-contact zone, by using the fixed-interface substructure method as reference, a few low-order modal coordinates are used to replace the nodal coordinates of the nodes, and meanwhile, the nodal coordinates of the local impact region are kept unchanged, therefore the total degrees of freedom （DOFs） are greatly cut down and the computational cost of the simulation is significantly reduced. By using additional constraint method, the impact constraint equations and kinematic constraint equations are derived, and the Lagrange equations of the first kind of flexible multi-body system are obtained. The impact of an elastic beam with a fixed half disk is simulated to verify the efficiency and accuracy of this method.

关键词： Contact-impact analysis · Flexible multi-body system · Component mode synthesis

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An efficient formulation based on the Lagrangian method for contact–impact analysis of flexible multi-body system

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Acta Mechanica Sinica 2016年第2期32卷 326-334页

作者： Peng Chen jin-yang liu Jia-Zhen Hong Department of Engineering Mechanics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiaotong University

In this paper,an efficien formulation based on the Lagrangian method is presented to investigate the contact–impact problems of f exible multi-body ***,the penalty method and the Hertz contact law are the most commonly used methods in engineering ***,these methods are highly dependent on various non-physical parameters,which have great effects on the simulation ***,a tremendous number of degrees of freedom in the contact–impact problems will influenc thenumericalefficien *** of these two problems,a formulation combining the component mode synthesis method and the Lagrangian method is presented to investigate the contact–impact problems in fl xible multi-body system ***,the finit element meshing laws of the contact bodies will be studied preliminarily.A numerical example with experimental verificatio will certify the reliability of the presented formulationincontact–***,aseries of numerical investigations explain how great the influenc of the finit element meshing has on the simulation *** the limitations of the element size in different regions are summarized to satisfy both the accuracy and efficien y.

关键词： Multi-body dynamics Contact–impact analysis Lagrangian method Component mode synthesis

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Calibration of Soil Electromagnetic Conductivity in Inverted Salinity Profiles with an Integration Method

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Pedosphere 2007年第2期17卷 246-256页

作者： YAO Rong-Jian yang jin-Song liu Guang-Ming Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 （China）.

Various calibration methods have been propounded to determine profiles of apparent bulk soil electrical conductivity (ECa) and soil electrical conductivity of a saturated soil paste extract (ECe) or a 1:5 soil water extract (EC1:5) using an electromagnetic induction instrument (EM38). The modeled coefficients, one of the successful and classical methods hitherto, were chosen to calibrate the EM38 measurements of the inverted salinity profiles of characteristic coastal saline soils at selected sites of Xincao Farm, Jiangsu Province, China. However, this method required three parameters for each depth layer. An integration approach, based on an exponential decay profile model, was proposed and the model was fitted to all the calibration sites. The obtained model can then be used to predict EC1:5 at a certain depth from electromagnetic measurements made using the EM38 device positioned in horizontal and vertical positions at the soil surface. This exponential decay model predicted the EC1:5 well according to the results of a one-way analysis of variance, and the further comparison indicated that the modeled coefficients appeared to be slightly superior to, but not statistically different from, this exponential decay model. Nevertheless, this exponential decay model was more significant and practical because it depended on less empirical parameters and could be used to perform point predictions of EC1:5 continuously with depth.

关键词： coastal saline soils electromagnetic conductivity exponential decay model integration calibration method inverted salinity profiles

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Fabrication of Highly Conductive Pd Nanowires using PDMS Transfer Method on DNA Scaffolds through Ethanol-Reduction

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Chinese Journal of Chemical Physics 2013年第5期26卷 607-611,I0004页

作者： Hong-bing Cai Zhen-xing Wang jin-yang liu Kun Zhang Xiao-ping Wang Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics University of Science and Technology of China Hefei 230025 China National Center For Nanoscience and Technolov Bellini: 100190 China Department of Physics University of Science and Technology of China Hefei 230025 China

We have developed a simple, productive, and ettectlve poly（cllmetnysltoxane） rranu fer method to fabricate highly conductive Pd nanowires following DNA scaffolds on various substrates, based on ethanolreduction at low temperature. Pd nanoparticles were selectively deposited and confined onto the DNA templates on a PDMS sheet to form Pd nanowires and then the nanowires were transferred to other various substrates with a low occurrence of par asitic nanoparticles. The structure, morphology and the conductance of Pd nanowires were characterized with transmission electron microscopy, field emission scanning electron mi croscopy, and electrical transport measurement, respectively. Moreover, the growth process of the Pd nanowires was investigated by varying the incubation time and reaction temper ature. The present strategy provides a new method to fabricate extremely dense, highly conductive, and well aligned Pd nanowires on various substrates, which make it promising for building nanosensors and nanoelectronic devices.

关键词： Pd nanowires DNA template Poly(dimethysiloxane) transfer Ethanol reduc-tion

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Nearly lattice-defect-free MOF membranes

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Science China Chemistry 2024年第3期67卷 741-743页

作者： Yuzhang Zhu yang liu Jian jin i-Lab Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China College of Chemistry Chemical Engineering and Materials ScienceSoochow UniversitySuzhou 215123China

Membrane technology has widely accepted as the most energy efficient technology for the separation of ions or molecules. As the core of the membrane technology, the chemical and structure nature of membrane materials determines the application and energy-efficiency of the technology. An advanced membrane that has a remarkable ability to selectively differentiate ions and molecules can significantly enhance the separation technology and revolutionize industrial separation processes.

关键词： processes. separation defect

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Regulation of interlayer channels of graphene oxide nanosheets in ultra-thin Pebax mixed-matrix membranes for CO_(2) capture

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Chinese Journal of Chemical Engineering 2024年第3期67卷 257-267页

作者： Feifan yang Yuanhang jin Jiangying liu Haipeng Zhu Rong Xu Fenjuan Xiangli Gongping liu Wanqin jin State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 211816China Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology School of Petrochemical EngineeringChangzhou UniversityChangzhou 213164China Shandong Production and Research Long Membrane Technology Development Co. Ltd.Yantai Economic Development ZoneYantai 265505China

For the application of carbon capture by membrane process,it is crucial to develop a highly permeable CO_(2)-selective *** this work,we reported an ultra-thin polyether-block-amide(Pebax)mixedmatrix membranes(MMMs)incorporated by graphene oxide(GO),in which the interlayer channels were regulated to optimize the CO_(2)/N_(2) separation *** membrane preparation conditions were systematically investigated on the influence of the membrane structure and separation performance,including the lateral size of GO nanosheets,GO loading,thermal reduction temperature,and *** results demonstrated that the precisely regulated interlayer channel of GO nanosheets can rapidly provide CO_(2)-selective transport channels due to the synergetic effects of size sieving and preferential *** GO/Pebax ultra-thin MMMs exhibited CO_(2)/N_(2) selectivity of 72 and CO_(2) permeance of 400 GPU(1 GPU=106 cm^(3)(STP)·cm^(2)·s^(-1)·cmHg^(-1)),providing a promising candidate for CO_(2) capture.

关键词： Mixed-matrix membrane Ultra-thin membrane Pebax Graphene oxide CO_(2) capture

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