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Large-stroke snap-through instability in the axial direction of a bi-stable structure with high slenderness

Theoretical & Applied Mechanics Letters 2025年第1期15卷 43-48页

作者： Huan Zhoua Qian Sun Haibin Xia Yiwei Xiong Youchao Yuan Yin Huang Jianghong Yuan Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 611756China Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Mechanical snap-through instability of bi-stable structures may find many practical applications such as state switching and energy *** there exist diverse bi-stable structures capable of snap-through instability,it is still difficult for a structure with high slenderness to undergo the axial snap-through instability with a large ***,an elastic structure with high slenderness is simply constructed by a finite number of identical,conventional bi-stable units with relatively low slenderness in series *** realizing the axial snap-through instability with a large stroke,common scissors mechanisms are further introduced as rigid constraints to guarantee the synchronous snap-through instability of these bi-stable *** global feature of the large-stroke snap-through instability realized here is robust and even insusceptible to the local out-of-synchronization of individual *** present design provides a simple and feasible way to achieve the large-stroke snap-through instability of slender structures,which is expected to be particularly useful for state switching and energy transforming in narrow spaces.

关键词： Synchronous instability Snap-through instability Bi-stability Large stroke High slenderness

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Preface to the Special Issue:Hydrogen Embrittlement and Storage

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1057-1058页

作者： Binhan sun Hao Chen Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai200237China Key Laboratory for Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing100084China

There is no doubt that hydrogen(H)is becoming one of the most promising sustainable energy carriers which can release at least partially the current strong reliance on fossil fuel-based energy and the resulting enviro... 详细信息

关键词： doubt Storage becoming

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A novel gyroscope based on the slow surface acoustic wave in a phononic metamaterial

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Microsystems & Nanoengineering 2024年第6期10卷 109-122页

作者： Fei Ge Liye Zhao Jiawen Xu Xukai Ding Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology Ministry of EducationSchool of Instrument Science and EngineeringSoutheast University210096 NanjingChina

Limited to the direct modulation on the surface acoustic wave(SAW)by the rotation,the conventional SAW gyroscopes incur weak Coriolis effects and gyroscopic *** this paper,we innovatively utilize a phononic metamaterial(PM)operated at whispering-gallery modes(WGMs)as the vehicle for the Coriolis effect rather than SAW *** gyroscopic effects of this PM are investigated,and a new SAW gyroscope is subsequently proposed based on the slow SAW in *** show,combining theoretical modeling and finite element method simulation,that the rate of rotation can linearly induce the splitting of WGMs and modulate the phase velocity of SAW down to 4600 m/s(initial phase velocity of 5355 m/s);the direction of rotation results in the chiral symmetry of the PM vibration and the asymmetric distribution of the transmissive ***,the proposed SAW gyroscope measures the angular velocity by detecting the phase shift resulting from rotation-dependent slow SAW in PM,obtaining a sensitivity of 0.016 deg/Hz when 50-cell *** with the existing SAW gyroscopes based on phase velocity modulation,the gyroscopic gain factor in this paper is enhanced by 430–1600 *** work jumps out of the framework of directly modulating SAW in gyroscopes and provides an innovative scheme of the indirect modulations from the rotation-dependent PM on SAW,showing excellent performance and potential for angular velocity measurement in extreme environments.

关键词： rotation wave angular

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On the micromechanism of superior strength and ductility synergy in a heterostructured Mg-2.77Y alloy

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Journal of Magnesium and Alloys 2024年第7期12卷 2793-2811页

作者： Yuliang Yang Yuxin Liu Shu Yan Shuang Jiang Zhufeng He Haizheng Pan Nan Jia Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang 110819China School of Materials Science and Engineering Northeastern UniversityShenyang 110819China Key Laboratory of Lightweight Structural Materials Northeastern UniversityShenyang 110819China

Heterostructured metals and alloys are a new class of materials in which mechanical behaviors between the heterogeneous regions are significantly different,and the mechanical properties of bulk materials are superior to the superposition of individual *** this paper,three distinct types of heterostructures were constructed in Mg-2.77Y(wt.%)alloy by applying simple thermomechanical ***,Type I:the non-recrystallized grains of several tens of microns were embedded in the micron-scaled recrystallized grains that were distributed along shear bands and dispersed near grain boundaries;Type II:the aggregations of micron-scaled recrystallized grains were surrounded by the non-recrystallized grains;Type II:the micron-scaled recrystallized grains dominated the microstructure,and the non-recrystallized regions with diameters of tens of micrometers were surrounded by those fine recrystallized *** tests showed that the material with type III heterostructure had the optimal combination of yield strength and uniform *** is attributed to its remarkable hetero-deformation induced(HDI)strengthening and dislocation *** the initial stage of plastic deformation(engineering strain below 4%),the rapid accumulation of geometrically necessary dislocations(GNDs)at the interfaces between recrystallized and non-recrystallized regions and between neighboring recrystallized grains lead to the significant HDI *** deformation proceeded,the HDI strengthening effect gradually decreased,and the traditional dislocation strengthening that was caused by GNDs accumulation at grain boundaries became ***-situ electron back-scattered diffraction(EBSD)testing revealed that the non-basal slip in the non-recrystallized regions became more remarkable in the late stage of deformation,which improved ductility and strain hardening of the *** findings provide new insight into the design of high-performance hexagonal close-pac

关键词： Heterostructure Magnesium alloy Hetero-deformation induced strengthening In-situ EBSD

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Influence of power dissipation value and deformation activation energy on recrystallization in compression deformation behavior of Mg-Li-Zn-Y alloy

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Journal of Rare Earths 2024年第12期42卷 2341-2349,I0006页

作者： Di An Bingyu Qian Ruizhi Wu Xiang Wang Legan Hou Xiaochun Ma Jinghuai Zhang Key Laboratory of Superlight Materials&Surface Technology Ministry of EducationCollege of Materials Science&Chemical EngineeringHarbin Engineering UniversityHarbin150001China College of Materials Science and Engineering Heilongjiang University of Science and TechnologyHarbin150022China

The thermal compression deformation behavior of Mg-6Li-11Zn-2.5Y alloy was systematically investigated by using the isothermal hot compression tests using the Gleeble-3500 thermal mechanical physical simulation system with the conditions of the temperature of 513-593 K and the strain rate of *** constitutive model and thermal processing map were *** variation pattern of the unstable region under different strains was analyzed and the safe processing region was *** influence of different power dissipation values and deformation activation energies on the dynamic recrystallization mechanism was *** results demonstrate that the deformation activation energy is 156.08 k J/*** unstable region gradually expands from the low temperature and low strain region to the high temperature and high strain region with the strain *** the unstable region,adiabatic shear band pear in a-Mg phase,of which the main reason is the poor processing formability in the unstable *** dominant nucleation mechanism is discontinuous dynamic recrystallization under the conditions of high power dissipation and low deformation activation ***,under the conditions of low power dissipation and high deformation activation energy,the nucleation mechanism is mainly driven by the particle stimulated nucleation.

关键词： Mg-Li Constitutive model Processing map Dynamic recrystallization Rare earths

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Generation and Suppression of Pendant Droplet Oscillation in Electron Beam Directed Energy Deposition

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engineering 2024年第6期37卷 215-229页

作者： Zhiyue Liang Zhenyu Liao Haoyu Zhang Zixiang Li Li Wang Baohua Chang Dong Du Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationTsinghua UniversityBeijing 100084China

Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing ***,the effects of EBs on pendant droplets at wire tips have not yet been *** aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet *** pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–***,another aim of this study is to create an oscillation suppression *** escalating asymmetric amplitude is the main characteristic of droplet *** primary oscillationinducing force is the recoil force generated from the EB-acted local surface of the *** physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the *** prerequisites for droplet oscillation include vacuum conditions,high power densities,and bypass wire feeding *** proposed EB–dynamic surrounding melting(DSM)method can be applied to conveniently and effectively suppress oscillations,enable the accurate transfer of droplets to the molten pool,and achieve stable processes for preparing the strut elements of lattice *** the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–*** this study,the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.

关键词： Additive manufacturing Electron beam freeform fabrication In situ monitoring Pendant droplet

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Probing the interlayer mechanical coupling of 2D layered materials-A review

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Progress in Natural science:materials International 2022年第5期32卷 528-537页

作者： Yinghui Sun Yufei Sun Rongming Wang Kai Liu Beijing Advanced Innovation Center for Materials Genome Engineering Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science School of Mathematics and Physics University of Science and Technology Beijing State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and Engineering Tsinghua University

Two-dimensional(2D) layered materials are assembled through the intralayer covalent bonds and interlayer van der Waals(vdWs) interactions. The relatively weak interlayer vdWs interactions result in the weak interlayer mechanical coupling between layers, which strongly impacts the overall mechanical properties of multilayer 2D materials or heterostructures. Experimentally probing the interlayer mechanical coupling is of vital importance on the accumulation of fundamental parameters for their applications in flexible and stretchable devices, yet there are hardly comprehensive reviews in this research field. In this review, we firstly introduce the probing methods of interlayer mechanical coupling, including high-frequency and ultralow-frequency Raman characterizations,nanoindentation of multilayer 2D materials or heterostructures, surface indentation, pressurized blister test,characterization of spontaneously formed nanoblisters, and nano-friction tests. Based on the analysis and comparison of the existing methods and results, we also discuss the advantages and limitations of each ***, the challenges and opportunities in this promising field are discussed. This review summarizes the recent progress in the probing of interlayer mechanical coupling of 2D layered materials and will provide important reference for the rational design of flexible and stretchable devices.

关键词： van der Waals interaction Mechanical properties Indentation Heterostructures

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Microstructure evolution of extruded Mg-RE-Ag alloy during short-time heat treatment

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Journal of Rare Earths 2024年第12期42卷 2350-2361,I0006页

作者： Zehua Li Jinghuai Zhang Shujuan Liu Jiaming Hao Liyuan Liu Yuying He Haodong Zhang Xingkai Jiao Xiaobo Zhang Ruizhi Wu Key Laboratory of Superlight Material and Surface Technology Ministry of EducationCollege of Material Science and Chemical EngineeringHarbin Engineering UniversityHarbin150001China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing Institute of TechnologyNanjing211167China

Microstructure regulation via short-time heat treatment is conducive to the optimization in the microstructure and properties of precipitable magnesium(Mg)alloys,but there is currently a lack of relevant *** this work,the microstructure evolution of a Mg-RE-Ag alloy during different short-time heat treatments was characterized and *** results show that extreme short-time heat treatment(ESHT,e.g.,2 min)at 450-480℃can greatly increase solute concentration in Mg matrix through the rapid re-dissolution of the second-phase and simultaneously maintain fine grains,while the ESHT at a too high temperature(e.g.,510℃)is not suitable due to excessive grain growth and coarse second phase regenerated at grain *** is found that 480℃is the approximate critical temperature for appropriate ESHT,and further prolongation of the time will lead to excessive grain *** is suggested that in addition to grain boundary migration,grain rotation is activated,resulting in the annihilation of high-angle grain boundaries with relatively low misorientation,as well as the reduction in the ability of the residual second phase to pin grain *** addition,the reasons for the abnormal grain boundary segregation and grain boundary continuous phase were analyzed from the perspective of interfacial *** study provides a basis for effective microstructure regulation of Mg-RE alloys.

关键词： Magnesium alloy Rare earths Microstructure Heat treatment Precipitates

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A new nonfullerene acceptor with an extended π conjugation core enables ternary organic solar cells approaching 19%efficiency

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Nano Research 2024年第5期17卷 4062-4068页

作者： Chunyan Liu Nailiang Qiu Zhengjin Li Yan Lu School of Materials Science and Engineering Tianjin Key Laboratory for Photoelectric Materials and DevicesKey Laboratory of Display Materials and Photoelectric DevicesMinistry of EducationTianjin University of TechnologyTianjin 300384China School of Chemistry Chemical Engineering and MaterialsJining UniversityQufu 273155China

In organic solar cells(OSCs),it is an effective way to improve the power conversion efficiency(PCE)by adding a guest component with appropriate absorption and energy levels in the host ***,a new nonfullerene acceptor(NFA)named TBF-2Cl was developed by the strategy of expanding theπconjugated core of 2,2’-(((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b’]dithiophene-2,7-diyl)bis(methaneylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(IDT-4Cl)with two benzene *** increase of benzene units,TBF-2Cl exhibits higher lowest unoccupied molecular orbital(LUMO)level of-3.75 eV than that of one benzene unit based NFA IDT-4Cl and fluorene core based NFA F-2Cl,which facilitates enhancing the open-circuit voltage(V_(oc))of ternary ***,TBF-2Cl film shows a medium optical bandgap with the absorption range from 500-800 nm,being well complementary with the wide bandgap polymer donor D18 and narrow bandgap NFA ***,a remarkable PCE of 18.92%with a high short-circuit current density(J_(sc))of 27.40 mA·cm^(-2),a fill factor(FF)of 0.749,especially an outstanding V_(oc) of 0.922 V was achieved for the optimal ternary device based on D18:TBF-2Cl:CH-6F,surpassing the binary counterpart(17.08%).The findings provide insight into the development of new guest acceptors for obtaining more efficient OSCs.

关键词： medium optical bandgap high lowest unoccupied molecular orbital(LUMO)level the third component ternary organic solar cell high open-circuit voltage

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Thermal fatigue and wear of compacted graphite iron brake discs with various thermomechanical properties

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China Foundry 2024年第3期21卷 248-256页

作者： Gui-quan Wang Zhuo Xu Zhong-li Liu Xiang Chen Yan-xiang Li School of Nuclear Equipment and Nuclear Engineering Yantai UniversityYantai 264005ShandongChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

The increase in payload capacity of trucks has heightened the demand for cost-effective yet high performance brake *** this work,the thermal fatigue and wear of compacted graphite iron brake discs were investigated,aiming to provide an experimental foundation for achieving a balance between their thermal and mechanical *** graphite iron brake discs with different tensile strengths,macrohardnesses,specific heat capacities and thermal diffusion coefficients were produced by changing the proportion and strength of *** peak temperature,pressure load and friction coefficient of compacted graphite iron brake discs were analyzed through inertia friction *** morphology of thermal cracks and 3D profiles of the worn surfaces were also *** is found that the thermal fatigue of compacted graphite iron discs is determined by their thermal properties.A compacted graphite iron with the highest specific heat capacity and thermal diffusion coefficient exhibits optimal thermal fatigue *** of the matrix at low temperatures significantly weakens the function of alloy strengthening in hindering the propagation of thermal *** the reduced hardness,increasing the ferrite proportion can mitigate wear loss resulting from low disc temperatures and the absence of abrasive wear.

关键词： compacted graphite iron brake disc thermomechanical properties thermal fatigue wear

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