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

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

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Solar PV-Battery-Electric Grid-Based Energy System for Residential Applications: System Configuration and Viability

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Research 2019年第1期2019卷 486-502页

作者： V.Bagalini B.y.zhao R.z.Wang U.Desideri University of Pisa DESTEC Largo Lucio LazzarinoPisa 56122Italy Institute of Refrigeration and Cryogenics Shanghai Jiao Tong UniversityShanghai 200240China

Distributed renewable energy share increase in electricity generation is creating challenges for the whole power system,due to its intermittent and nonprogrammable *** storage has the potential to solve those issues although its technical,economic,and environmental impact is up for *** paper presents a study about a PV-battery energy storage system installed in a gridconnected residential apartment in the Green Energy Laboratory at Shanghai Jiao Tong University,*** experimental results show how the presence of energy storage reduces the midday feed-in of excess PV power and the evening peak demand,providing benefits to the distribution network in terms of reduced voltage swings and peak *** the Chinese context,an economic analysis is carried out to assess the profitability of residential PV-battery systems,using the net present value as the economic indicator of an 18-year investment in which the battery pack is replaced twice(6 life years).The analysis shows that such system is not economically viable due to a combination of low electricity prices,valuable PV incentives,and high technology ***,considering a future scenario of doubled electricity tariff,halved export tariff,and falling technology costs(-66%battery and-17%PV and inverter),PV-battery investment becomes profitable and shows more resilience to future scenarios than PV-only investment.

关键词： battery Battery Solar

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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

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Stabilization of Traffic Flow Based on the Multiple Information of Preceding Cars

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Communications in Computational Physics 2008年第4期3卷 899-912页

作者： D.F.Xie z.y.Gao X.M.zhao State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China. Institute of System Science School of Traffic and TransportationBeijing Jiaotong UniversityBeijing 100044China.

To enhance the stability of traffic flow,a new car-following model is proposed by taking into account the support of intelligent transportation system(ITS)information,which includes both the headway and the velocity difference of multiple preceding *** new model is based on the Optimal Velocity(OV)model and its extended *** stability condition of the model is obtained by using the linear stability *** nonlinear analysis,the modified Korteweg-de Vries equation is constructed and solved,and the traffic flow is classified into three types,***,metastable,and *** jam phase can thus be described by the kink-antikink soliton solution for the mKdV *** numerical simulation results show that compared with previous models considering only one of the ITS information,the proposed model can suppress traffic jams more efficiently when both headway and velocity difference of arbitrary preceding cars are taken into *** results of numerical simulation coincide with the theoretical ones.

关键词： Traffic flow car-following model stability analysis ITS information

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EFFECT OF LOW-FREQUENCy ELECTROMAGNETIC FIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES OF HDC 2024 ALUMINUM ALLOy

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 205-210页

作者： Q.F. zhu z.H. zhao J.z. Cui y.B. zuo F. Qu Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern Univer- sity Shenyang 110004 China

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm× 200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting processre- spectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could sub- stantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.

关键词： Horizontal direct chill casting Low frequency electromagnetic field 2024 aluminum alloy Microstructures Macrosegregation

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An explicit solution to a three-dimensional wedge problem considering two edges effect

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Friction 2020年第2期8卷 370-383页

作者： L.GUO z.M.zHANG W.WANG y.zhao P.L.WONG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Mechanical Engineering City University of Hong KongHong Kong SARChina

The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded *** algorithm makes use of a recently published concept of transformation matrix,by which the original surface loads are converted to equivalent loads in *** three loaded edges are considered *** developed algorithm is used to study the effects of two free edges of a steel block and tapered rollers with different contact *** two load-free edges can substantially increase deformation if the two edges are close in *** results of the tapered roller simulation show that deformation is considerably sensitive to the contact angle of the tapered *** largest deformation appears at the big end of the ***,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.

关键词： contact mechanics two edge surfaces finite line contact tapered roller contact

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LOW CyCLE FATIGUE BEHAVIOR OF Az91HP ALLOy IN AS HIGHP RESSURE DIE CASTING

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Acta Metallurgica Sinica(English Letters) 2000年第4期13卷 961-966页

作者： Liu, z. Xu, y.y. Wang, z.G. Wang, y. Liu, z.y. Inst of Metal Research Chinese Acad of Sciences Shenyang China

Fully reversed total strain-controlled low-cycle fatigue tests were conducted at room temperature in air to study the fatigue behavior of Az91HP magnesium alloy in as high pressure die casting and subsequently heat treatment. All the specimens in different heat histories exhibit cyclic strain hardening in different degrees. It is difficult to distinguish the fatigue behavior of the die casting specimens from that of the solution aging specimens. The solution treated specimens show longer fatigue life at high strain amplitude and shorter fatigue life at low strain amplitude than the die casting and solution aging specimens though they have the lowest yield strength with higher strain hardening. Fatigue fracture surfaces for strain amplitude larger than 0.005 show very similar to those found by monotonic tensile tests. The SEM examination reveals that the regions of fatigue crack growth and final fracture can be characterized by quasi-cleavage mechanisms, but some shallow dimples, slip bands and secondary cracks are found on the fracture surface in the fracture crack growth areas.

关键词： Cracks Die casting Fatigue of materials Heat treatment

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Moment Redistribution Effect of the Continuous Glass Fiber Reinforced Polymer-Concrete Composite Slabs Based on Static Loading Experiment

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Structural Durability & Health Monitoring 2025年第1期19卷 105-123页

作者： zhao-Jun zhang Wen-Wei Wang Jing-Shui zhen Bo-Cheng Li De-Cheng Cai yang-yang Du Hui Huang Offshore Oil Engineering Co.Ltd. Tianjin300461China Department of Bridge Engineering School of TransportationSoutheast UniversityNanjing211189China

This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment *** experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was *** composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab *** methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel *** experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal *** contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading *** the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan *** the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span *** GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span *** test specimens experienced compressive failure of concrete at the mid-span *** results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support *** proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.

关键词： Moment redistribution GFRP-concrete composite slabs bending moment experimental study analysis model

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Grids of stellar models including second harmonic and colors:solar composition(z = 0.0172,X = 0.7024)

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Research in Astronomy and Astrophysics 2015年第12期15卷 2244-2262页

作者： Mutlu y?ld?z Ege University Department of Astronomy and Space Sciences

Grids of stellar evolution omy/astrophysics, such as planet hosting are required in many fields of astron- stars, binaries, clusters, chemically peculiar stars, etc. In this study, a grid of stellar evolution models with updated ingredients and recently determined solar abundances is presented. The solar values for the initial abundances of hydrogen, heavy elements and mixing-length parameter are 0.0172, 0.7024 and 1.98, respectively. The mass step is small enough （0.01 M） that interpolation for a given star mass is not required. The range of stellar mass is 0.74 to 10.00M. We present results in different forms of tables for easy and general appli- cation. The second stellar harmonic, required for analysis of apsidal motion of eclips- ing binaries, is also listed. We also construct rotating models to determine the effect of rotation on stellar structure and derive fitting formulae for luminosity, radius and the second harmonic as a function of rotational parameter. We also compute and list colors and bolometric corrections of models required for transformation between theo- retical and observational results. The results are tested for the Sun, the Hyades cluster, the slowly rotating chemically peculiar Am stars and eclipsing binaries with apsidal motion. The theoretical and observational results along isochrones are in good agree- ment. The grids are also applicable to rotating stars provided that equatorial velocity is given.

关键词： stars: interior -- stars: evolution -- binaries: eclipsing -- stars: chemi-cally peculiar

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Preface to the Special Issue:Friction Stir Welding and Processing

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 1-2页

作者： z.y.Ma Institute of Metal Research Chinese Academy of SciencesShenyangChina

Friction stir welding(FSW),a highly effi cient solid-state joining technique,was invented at The Welding Institute,UK,in *** frictional and adiabatic heating,plastic deformation and solid-state diff usion,FSW has been widely accepted as a“green”welding technology owing to its energy effi ciency and environment ***,FSW has achieved broad application in various industries,such as aerospace and transportation,and is considered the most signifi cant development in the fi eld of material joining over the past two *** stir processing(FSP),later developed based on the fundamental principles of FSW,has been demonstrated as an eff ective and versatile metalworking technique for modifying and fabricating metallic materials.

关键词： FSP Preface to the Special Issue:Friction Stir Welding and Processing

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