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Nonlinear mechanics of a ring structure subjected to multi-pairs of evenly distributed equal radial forces

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Acta Mechanica Sinica 2017年第5期33卷 942-953页

作者： Q. Chen F. Sun Z. y. li l. Taxis N. Pugno Biomechanics laboratory School of Biological Science and Medical Engineering Southeast University State Key.l.boratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics School of Chemistry Physics and Mechanical EngineeringQueensland University of Technology (QUT) laboratory of Bio-Inspired and Graphene Nanomechanics Department of Civil Environmental and Mechanical Engineering University of Trento School of Engineering and Materials Science Queen Mary University of London Ket lab Italian Space Agency Via del Politecnico snc

Combining the elastica theory, finite element (FE) analysis, and a geometrical topological experiment, we studied the mechanical behavior of a ring subjected to multi-pairs of evenly distributed equal radial forces by.l.oking at its seven distinct states. The results showed that the theoretical predictions of the ring deformation and strain energy matched the FE results very well, and that the ring deformations were comparable to the topological experiment. Moreover, no matter whether the ring was compressed or tensioned by N-pairs of forces, the ring always tended to be regular polygons with 2N sides as the force increased, and a proper compressive force deformed the ring into exquisite flower-like patterns. The present study solves a basic mechanical problem of a ring subjected to lateral forces, which can be useful for studying the relevant mechanical behavior of ring structures from the nano- to the macro-scale.

关键词： Ring structures Mechanical properties Shape Strain energy

Nanocrystalline Ti49.2Ni50.8 shape memory alloy as orthopaedic implant material with better performance

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Journal of Materials Science & Technology 2019年第10期35卷 2156-2162页

作者： H.F.li F.l.Nie y.F.Zheng y.Cheng S.C.Wei R.Z.Valiev Department of Materials Science and Engineering College of EngineeringPeking UniversityBeijing 700877China Center for Biomedical Materials and Tissue Engineering Academy for Advanced Interdisciplinary StudiesPeking UniversityBeijing 100871China Department of Oral and Maxillofacial Surgery School of StomatologyPeking UniversityBeijing 100081China Institute of Physics of Advanced Materials Ufa State Aviation Technical UniversityUfaRussia Saint Petersburg State University Universitetskiy prospekt 28PeterhofSt.Petersburg198504Russia

Ti Ni alloys, with their unique shape memory effects and super elastic properties, occupy an indispensable place in the family of metallic biomaterials. In the past years, surface treatment is the main technique to improve the bioinert nature of microcrystalline Ti Ni alloys and inhibit on the release of toxic nickel ions to obtain excellent osteogenesis and osseointegration function. In the present study, nanocrystalline Ti49.2Ni50.8 alloy has been fabricated via equal channel angular pressing(ECAP), and the in vitro and in vivo studies revealed that it had enhanced cell viability, adhesion, proliferation, AlP(Alkaline phosphatase)activity and mineralization, and increased periphery thickness of new bone, in comparison to the commercial coarse-grained counterpart. These findings indicate that the reduction of grain size is beneficial to increasing the biocompatibility of Ti49.2Ni50.8 shape memory alloy.

关键词： Nanocrystallines Shape memory alloys Metallic biomaterials Orthopaedic implants TiNi alloys

Immanant positivity for Catalan-Stieltjes matrices

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Frontiers of Mathematics in China 2022年第5期17卷 887-903页

作者： Ethan y.H.li Grace M.X.li Arthur l.B.yANG Candice X.T.ZHANG Center for Combinatorics LPMCNankai UniversityTianjin 300071China

We give some sufficient conditions for the nonnegativity of immanants of square submatrices of Catalan-Stieltjes matrices and their corresponding Hankel *** obtain these sufficient conditions,we construct new planar networks with a recursive nature for Catalan-Stieltjes *** applications,we provide a unified way to produce inequalities for many combinatorial polynomials,such as the Eulerian polynomials,Schröder polynomials,and Narayana polynomials.

关键词： Immanant character Catalan-Stieltjes matrices Hankel matrices planar network

Compression Stability of Reversed Austenite in 9Ni Steel

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Journal of Materials Science & Technology 2012年第6期28卷 558-561页

作者： S.H.Chen M.J.Zhao X.y.l. l.J.Rong Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α transformation, while the hydrostatic pressure suppressed the -Υ-α transformation. The pressure dependent transformation behavior can be explained according to thermodynamic analysis.

关键词： 9Ni steel Martensite Reversed austenite Hydrostatic pressure Uniaxial compressive pressure

Simultaneous enhancement of mechanical and shape memory properties by heat-treatment homogenization of Ti_(2)Ni precipitates in TiNi shape memory alloy fabricated by selective laser melting

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Journal of Materials Science & Technology 2022年第6期101卷 205-216页

作者： H.Z.lu l.H.liu C.yang X.luo C.H.Song Z.Wang J.Wang y.D.Su y.F.Ding l.C.Zhang y.y.l. National Engineering Research Center of Near-net-shape Forming for Metallic Materials South China University of TechnologyGuangzhou 510640China Musculoskeletal Oncology Department Sun Yat-Sen University Cancer CenterGuangzhouGuangdong ProvinceChina Shenyang Aircraft Design and Research Institute Shenyang 110035China Guangdong Huayi Plumbing Fittings Industry Co. Ltd.Kaiping 529321China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SlM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti_(2)Ni precipitates in a Ti_(50.6)Ni_(49.4)SMA fabricated using SlM. Specifically, because of the complete solution treatment, nanoscale spherical Ti_(2)Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cy.l.s. These simultaneously enhanced properties are considerably superior than those of most previously reported Ti Ni SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti_(2)Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti_(2)Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in Ti Ni SMAs and will accelerate the wider application of SMAs.

关键词： Shape memory alloy Selective laser melting Heat treatment Mechanical properties Shape memory properties

Recent development in the application of bulk metallic glasses

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Journal of Materials Science & Technology 2022年第36期131卷 115-121页

作者： K.Gao X.G.Zhu l.Chen W.H.li X.Xu B.T.Pan W.R.li W.H.Zhou l.li W.Huang y.l. Dongguan yihao Metal Technology Co.ltd Dongguan 523686China Dongguan Eontec Co.ltd Dongguan 523686China Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Over the past decades,considerable efforts have been made in the commercial application of bulk metallic glasses(BMGs).Despite great challenges faced by the industrial players,significant progress has been achieved,and millions of commercial products for various kinds of applications have been shipped around the *** in this paper,we shall present the alloys suitable for the actual products in the application and discuss the merits of the processing technique of BMGs over the existing processing techniques and *** importantly we demonstrate the typical examples of products over the past few ***,future directions of the industrialization of BMGs are also discussed.

关键词： Bulk metallic glasses Commercial application Alloy design Products

Magneto-Impedance Effect of Composite Wires Prepared by Chemical Plating under DC Current

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Nano-Micro letters 2014年第3期6卷 227-232页

作者： D.l.Chen X.li H.l.Pan H.y.l.an Z.J.Zhao Department of Physics Engineering Research Center for Nanophotonics & Advanced Instrument Ministry of Education East China Normal University

CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composition, giant magneto-impedance(GMI) effect and magnetic properties were *** was shown that the circumferential domain structure of coating layer was induced by the DC current going through the wires. A maximum GMI ratio of 870% was obtained in the composite wire prepared under 150 m A and tested at 180 k Hz. It is 30 times higher than that of the composite wire plated in the same condition by conventional chemical plating method, indicating that CPUDC is an easy and effective approach to obtain composite wires and its applications will be further extended on magnetic sensors.

关键词： GMI Chemical plating Magnetic properties

Adaptive partitioning-based discrete unified gas kinetic scheme for flows in all flow regimes

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Advances in Aerodynamics 2023年第1期5卷 282-311页

作者： l.M.yang l.C.Han H.Ding Z.H.li C.Shu y.y.l.u Department of Aerodynamics College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China State Key.l.boratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key.l.boratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016China Department of Modern Mechanics University of Science and Technology of ChinaHefei 230027China National laboratory for Computational Fluid Dynamics Beihang UniversityBeijing 100191China Department of Mechanical Engineering National University of SingaporeSingapore 117576Singapore

To improve the efficiency of the discrete unified gas kinetic scheme(DUGKS)in capturing cross-scale flow physics,an adaptive partitioning-based discrete unified gas kinetic scheme(ADUGKS)is developed in this *** ADUGKS is designed from the discrete characteristic solution to the Boltzmann-BGK equation,which contains the initial distribution function and the local equilibrium *** initial distribution function contributes to the calculation of free streaming fluxes and the local equilibrium state contributes to the calculation of equilibrium *** the contribution of the initial distribution function is negative,the local flow field can be regarded as the continuous flow and the Navier-Stokes(N-S)equations can be used to obtain the solution ***,the discrete distribution functions should be updated by the Boltzmann equation to capture the rarefaction *** this,in the ADUGKS,the computational domain is divided into the DUGKS cell and the N-S cell based on the contribu-tion of the initial distribution function to the calculation of free streaming *** the N-S cell,the local flow field is evolved by solving the N-S equations,while in the DUGKS cell,both the discrete velocity Boltzmann equation and the correspond-ing macroscopic governing equations are solved by a modified *** more and more cells turn into the N-S cell with the decrease of the Knudsen number,a significant acceleration can be achieved for the ADUGKS in the continuum flow regime as compared with the DUGKS.

关键词： Boltzmann-BGK equation Discrete unified gas kinetic scheme Adaptive partitioning Discrete characteristic solution All flow regimes

Development of an Explicit Symplectic Scheme that Optimizes the Dispersion-Relation Equation of the Maxwell’s Equations

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Communications in Computational Physics 2013年第4期13卷 1107-1133页

作者： Tony W.H.Sheu l.y.l.ang J.H.li Department of Engineering Science and Ocean Engineering National TaiwanUniversityNo.1Sec.4Roosevelt RoadTaipeiTaiwan Taida Institute of Mathematical Science(TIMS) National Taiwan UniversityTaiwan Center for Quantum Science and Engineering(CQSE) National Taiwan UniversityTaiwan

In this paper an explicit finite-difference time-domain scheme for solving the Maxwell’s equations in non-staggered grids is *** proposed scheme for solving the Faraday’s and Amp`ere’s equations in a theoretical manner is aimed to preserve discrete zero-divergence for the electric and magnetic *** inherent local conservation laws in Maxwell’s equations are also preserved discretely all the time using the explicit second-order accurate symplectic partitioned Runge-Kutta *** remaining spatial derivative terms in the semi-discretized Faraday’s and Amp`ere’s equations are then discretized to provide an accurate mathematical dispersion relation equation that governs the numerical angular frequency and the wavenumbers in two space *** achieve the goal of getting the best dispersive characteristics,we propose a fourth-order accurate space centered scheme which minimizes the difference between the exact and numerical dispersion relation *** the computational exercises,the proposed dual-preserving solver is computationally demonstrated to be efficient for use to predict the long-term accurate Maxwell’s solutions.

关键词： Maxwell’s equations non-staggered grids zero-divergence fourth-order dualpreserving solver dispersion relation equations