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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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Structural evolution of Al–8%Si hypoeutectic alloy by ultrasonic processing

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journal of Materials Science & Technology 2017年第11期33卷 1235-1239页

作者： j.y.wang B.j.wang L.F.Huang Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China

High intensity power ultrasound was respectively introduced into three different solidification stages of Al–8%Si hypoeutectic alloy, including the fully liquid state before nucleation, the nucleation and growth process of primary α（Al） phase and L →（Al）＋（Si） eutectic transformation period. It is found that both the primary α（Al） phase and（Al ＋ Si） eutectic structure were refined by different degrees with various growth morphologies depending on the ultrasonic treatment stage. Based on the experimental results,the cavitation-induced nucleation due to the high undercooling caused by the collapse of tiny cavities was proposed as the major reason for refining the primary α（Al） phase. Meanwhile, obvious eutectic morphological change was observed only when ultrasound was directly introduced in the eutectic transformation stage, in which typical divorced eutectics and（Al ＋ Si） eutectic cells with symmetrical flower shape were formed at the top of the alloy sample. The introduction of ultrasound in each solidification stage also improves the yield strength of Al–8% Si alloy to a diverse extent.

关键词： Solidification Microstructure Metals and alloys Power ultrasound Refinement

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Ultrasonic solidification mechanism and optimized application performances of ternary Mg_(71.5)Zn_(26.1)y_(2.4) alloy

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journal of Magnesium and Alloys 2023年第10期11卷 3829-3839页

作者： y.j.Hu j.y.wang W.Zhai B.Wei School of Physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)y_(2.4) *** acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg_(3)Zn_(6)y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg_(3)Zn_(6)y phase. The morphological transition of(α-Mg+Mg_(3)Zn_(6)y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg_(3)Zn_(6)y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.

关键词： Three dimensional ultrasounds Quasicrystalline Mg_(3)Zn_(6)y phase Anomalous eutectic Mechanical performances Corrosion resistance

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First-principles Study of Point Defects in Stoichiometric and Non-stoichiometric y_4Al_2O_9

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journal of Materials Science & Technology 2013年第12期29卷 1161-1165页

作者： Z.Li B.Liu j.M.wang L.C.Sun j.y.wang y.C.Zhou Z.j.Hu High-performance Ceramics Division Shenyang National Laboratory for Materials ScienceInstitute of Metal ResearchChinese Academy of Sciences Aerospace Research Institute of Materials and Processing Technology

By using the first-principles calculation, we studied the mechanisms of point defects in y4AI209 （yAM）, a promising ternary oxide with excellent optical and thermal properties. It is found that the predominant native defect species is closely dependent on the chemical potentials of each constituent. In the case of O-rich condition, the oxygen interstitial has the very low defect formation energy, followed by the anti-site defects and AI vacancy; in the case of AI-rich condition, the oxygen vacancy yields the lowest defect formation energy, followed by the anti-site defects and AI interstitial. The present result shows that in all the possible chemical potential ranges, anti-site defects have relatively low defect formation energy and might exist in high concentration in yAM. Furthermore, AIy anti-site has relatively lower defect formation energy than the yAt anti- site throughout. The behaviors of defect complexes under non-stoichiometric condition, such as the AI203 or y203 excess, are also investigated. The results provide helpful guide to optimize the experimental synthesizing of yAM.

关键词： Ternary y-AI-O oxide Defect formation energy Chemical potential

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Strong Anisotropy of KTiOPO4 Crystals under an Electric Field Observed by Synchrotron Radiation Topography

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同步辐射装置用户科技论文集 1999年第1期 199-204页

作者： W.j.LIU j.y.wang 等 NationalLaboratoryofSolidStateMicrostructures NanjingUniversityNanjing210093P.R.China InstituteofCrystalMaterials ShandongUniversityJinan250100P.R.China

In-situ white-beam synchrotron radiation topographic observations under an electric field have been made on KTiOPO4 family *** investigation shows a strong enhancement of diffracted intensity of hkl reflections(l≠0) and the topographic extinction contrast,when the field is applied along the polar *** and undoped samples with grown-in defects are studied in *** is believed that the movement of K^+ ions driven by the field leads to a local accumulation of charges and the lattice *** the field-related phenomena appear to be related to the one-dimensional ionic conductance.

关键词： KTiOPO4晶体电场同步辐照地形观测

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The Application of Synchrotron Radiation Techniques to the Study of Domain Structures and their Dynamics in Ferroic Crystals

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同步辐射装置用户科技论文集 1999年第1期 183-192页

作者： S.S.jIANG j.y.wang 等 NationalLaboratoryofSolidStateMicrostructures NanjingUniversityNanjing210093.P.R.China InstituteofCrystalMaterials ShandongUniversityJinan250100P.R.China

The recent research work on domain structures and their dynamics in fenoelastic and ferroelectric crystals by white-beam synchrotron radiation topography is *** real-time imaging,fine-beam Laue diffraction,and anomalous-scattering topography were carried out to the study of the domain structures and phase transition in the ferroelastic NdP5O14 and LaP5O14,and ferroelectric KTa1-xNbxO3,(Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6,and KTiOPO4 *** preliminary results are presented and discussed.

关键词：铁电晶体畴结构动力学辐照

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GROWTH TWINS IN ybxy1—xAl3（BO3）4 AND NdxGd1—xAl3（BO3）4 CRySTAIS OBSERVED By WHITE—BEAM SyNCHROTRON RADIATION TOPOGRAPHy

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同步辐射装置用户科技论文集 2000年第1期 299-304页

作者： X.B.Hu j.y.wang 等

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Rapid Growth and Magnetic Properties of Fe7Co3 Intermetallic Compound

Rapid Growth and Magnetic Properties of Fe7Co3 Intermetallic...

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2012 International Conference on Mechanical Engineering and Materials(ICMEM 2012)

作者： y.y.Zhang W.j.yao W.Sun j.y.wang X.j.Han N.wang Department of Applied Physics Northwestern Polytechnical University School of Materials Science Shanghai Jiaotong University

By drop tube and melt spinning techniques,rapid growth of Fe7Co3 intermetallic compound has been *** microstructures and nucleation characteristics under different cooling rates are *** the increase of cooling rate,Fe7Co3 intermetallic compound grains are refined in both rapid growth *** observation and theoretical analysis indicate that the nucleation rate in single-roller quenching is much greater than that in free-fall method when the cooling rate is under a same *** comparison of magnetic property between the alloy ribbons and other dimensional magnetic material were *** superior soft magnetic properties of Fe-Co alloy ribbons changes sensitively with the cooling rate,which is mainly decided by the wheel velocity.

关键词： Intermetallic Rapid solidification Microstructure Magnetic

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Experimental study of the ultrasonic and mechanical properties of SRM under compressive loading

Experimental study of the ultrasonic and mechanical properti...

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中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： y.wang X.Li R.L.Hu S.D.Li j.y.wang Key Laboratory of Shale Gas and Geoengineering Institute of Geology and GeophysicsChinese Academy of Sciences School of Hydraulic Engineering Changsha University of Science and Technology

Experiments were conducted to investigate the relationship between the ultrasonic pulse velocity(UPV),transmission ratio(TR),attenuation coefficient(AC)and mechanical properties of soil and rock mixture(SRM)with different rock percentage,under uniaxial *** SRM specimens(50 mm diameter and100 mm height)with rock block percentage of 20,30,40,and 50%were produced to perform a series of Uniaxial Compressive Strength(UCS)*** ultrasonic wave was transmitted and received by a P-wave piezoelectric transducer(130 kHz)and the ultrasonic travel time and amplitude were recorded by an ultrasonic detector during the whole deformation process of *** the test results,the UPV decreased and AC increased with the increasing rock percentage for all specimens by ultrasonic inspection before UCS *** failure mechanism of all specimens showed splitting-sliding mixed pattern,macrocracks have a direction of 0-10°parallel or sub-parallel tonormal stress,and UCS decreased with increasing of rock *** addition,the UPV and TR have fluctuation growth trend with increasing of axial stress while the increment rate decreased *** statistical correlations between UPV and TR and axial stress are presented and ***,the relationship between ultrasonic parameters and axial stress for soil and rock specimens were also *** results confirm that the ultrasonic and mechanical properties of SRM are closely related to rock *** a special geomaterial,the mechanical properties of SRM are different from rock and soil;this can be further confirmed by ultrasonic tests.

关键词： Soil and rock mixture(SRM) Ultrasonic wave Mechanical properties Uniaxial compressive strength test

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Investigation of the Relationship Between SLA-1 and SLA-3 Gene Expression and Susceptibility to Escherichia Coli F18 in Post-weaning Pigs

Investigation of the Relationship Between SLA-1 and SLA-3 Ge...

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第五届中国畜牧科技论坛

作者： L.ye C.Zi X.M.Su Z.C.Wu G.Q.Zhu S.L.Wu j.y.wang College ofAnimal Science and Technology Yangzhou University College of Veterinary Medicine Yangzhou University yangzhou Public Technical Service Center for Large-scale High Efficient and Healthy Breeding of Pig Suzhou Taihu Pig Breeding Center

Porcine post-weaning diarrhea and edema disease are principally caused by *** strains that produce F18 ***1 genotyping and receptor binding studies divided piglets into *** F18-resistant and -sensitive groups,and the roles of SLA-1 and SLA-3 were ***-1 and SLA-3 expression was detected in 11 pig tissues,with higher levels of SLA-1 in lung,immune tissues and gastrointestinal tract,and higher levels of SLA-3 also in lung and lymphoid *** genes were expressed higher in F18-resistant piglets,and their expression was positively correlated in different tissues;a negative correlation was observed in some tissues of F18-sensitive group,particularly in lung and lymphatic *** ontology and pathway analyses showed that SLA-1 and SLA-3 were involved in 37 biological processes,including nine pathways related to immune *** observations help to elucidate the relationship between SLA class I genes and E. coli F18-related porcine gastrointestinal tract diseases.

关键词： Escherichia coli F18 post-weaning piglet SLA-1 SLA-3.

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