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Influence of mandrel-cores filling on size effect of cross-section distortion of bimetallic thin-walled composite bending tube

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Chinese Journal of Aeronautics 2023年第3期36卷 421-435页

作者： Yingxia ZHU Miaomiao WAN Wei CHEN Yun WANG Wenbin TU Fan XU School of Mechanical Engineering Jiangsu UniversityZhenjiang 212013China School of Mechanical Engineering Guilin University of Aerospace TechnologyGuilin 541004China

Two new size factors of cross-section hollow coefficient and bending degree are introduced to reveal the size effect of bending forming of bimetallic composite *** coefficient and bending degree can limit the commonly used bent tube to the size description range of(0,2.00).The evolution laws of the cross-section distortion forms in the hollow coefficient-bending degree interval are revealed as well as the action of the mandrel-cores on the size *** show the mandrel-cores filling can expand the forming limit of the bent tube,but also bring two other forming defects of wrinkle and *** identification factor(hollow coefficient multiply bending degree)provides a method for querying the cross-section distortion forms of all composite bending *** the identification factor interval(0,1.00),the distribution area of bending forming defects of the composite tube is *** thin-walled composite bending tube collapses when identification factor in(0,0.39),wrinkles when identification factor in[0.39,0.50),and ruptures when identification factor in[0.50,1.00).The mathematical model of size effect is derived,by which the average cross-section distortion rate is found to distribute like a radial leaf in the hollow coefficient-bending degree qualified forming *** best forming zone is hollow coefficient 0.46-0.68,and bending degree 0.25-0.47.

关键词： Bending Bimetallic composite tube Cross-section distortion size factor size effect Mandrel

Tailoring mechanical properties of PμSL 3D-printed structures via size effect

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International Journal of Extreme Manufacturing 2022年第4期4卷 261-268页

作者： Wenqiang Zhang Haitao Ye Xiaobin Feng Wenzhao Zhou Ke Cao Maoyuan Li Sufeng Fan Yang Lu Department of Mechanical Engineering City University of Hong KongKowloonHong Kong SAR 999077People's Republic of China Nano-Manufacturing Laboratory(NML) City University of Hong Kong Shenzhen Research InstituteShenzhen 518057People's Republic of China Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518055People's Republic of China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of TechnologyWuhan 430070People's Republic of China School of Mechano-Electronic Engineering Xidian UniversityXi'an 710071People's Republic of China State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001People's Republic of China

Projection micro stereolithography(PμSL)has emerged as a powerful three-dimensional(3D)printing technique for manufacturing polymer structures with micron-scale high resolution at high printing speed,which enables the production of customized 3D microlattices with feature sizes down to several ***,the mechanical properties of as-printed polymers were not systemically studied at the relevant length scales,especially when the feature sizes step into micron/sub-micron level,limiting its reliable performance prediction in micro/nanolattice and other metamaterial *** this work,we demonstrate that PμSL-printed microfibers could become stronger and significantly more ductile with reduced size ranging from 20μm to 60μm,showing an obvious size-dependent mechanical behavior,in which the size decreases to 20μm with a fracture strain up to~100%and fracture strength up to~100 *** size effect enables the tailoring of the material strength and stiffness of PμSL-printed microlattices over a broad range,allowing to fabricate the microlattice metamaterials with desired/tunable mechanical properties for various structural and functional applications.

关键词： 3D printing projection micro-stereolithography(PμSL) size effect microfiber mechanical properties microlattice metamaterial

Specimen size effect on the fracture energy of architected stretchable materials

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International Journal of Smart and Nano Materials 2023年第4期14卷 420-439页

作者： Xiao Li Libo Men Yilin Yu Zhaoyang Hou Zhengjin Wang State Key Laboratory for Strength and Vibration of Mechanical Structures Department of Engineering MechanicsSchool of Aerospace EngineeringXi'an Jiaotong UniversityXi'anPR China

Architected stretchable materials with well-organized microarchitectures evolve very rapidly due to their potential in customizing mechanical properties and achieving exotic *** many applications,the architected stretchable materials are required to sustain large deformation,and their fracture is ***,the size effect on the fracture of architected stretchable materials is still ***,we study this issue by experiment and finite element *** is found that the fracture energy of architected stretchable materials increases with the specimen size ratio,H/h,within a *** H/h reaches a transition ratio,Rt,the fracture energy approaches a *** transition ratio differentiates the size-dependent and size-independent fracture behavior of architected stretchable *** mechanical properties of constituent material only have a minor effect on the transition *** degree of constraint and stress concentration at the node,which are affected by the geometry of the unit-cell,dominate the specimen size *** result gives a practical guidance in choosing the specimen size to measure the steady state fracture energy of this class of *** work provides insights into the fracture of architected stretchable materials and design for fractureresistant architected stretchable devices.

关键词： Architected stretchable materials fracture energy size effect transition ratio

size effect and growth options over firm lifecycle

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Journal of Management Science and Engineering 2022年第2期7卷 197-212页

作者： Qiang Li Hao Liu Yong Zeng School of Manggement and Economics Univeriy of Electronic Science aond Tec hnology of ChinaCherngdu611731China School of Finance.Guongdong Univerity of Foreign Studies.Cuangzhou 510006.China Institute of Financial Openess and Asset Management Guangzhou510006China

The size effect can be attributed to the relative importance of growth options versus assets-in-place in total *** incorporating the changing trend of growth options over firm lifecycle into the dynamic investment model developed by Berk et al.(1999)。this paper demonstrates that the gradual exhausting or exercising of growth options would cause a downward pattern of size effect over firm lifecycle,while new growth options created by R&D or innovative investments can intensify size *** a sample of listed firms in USA stock market during the period of 1963-2018,both cross-sectional evidence on individual stocks and time-series evidence on portfolios analysis support theoretical preditions well,and empirical findings are robust for different methodologies,different measures of the exerci sing/creating of growth options,and for China's stock market.

关键词： Growth options size effect Firm lifecycle Stock returns|

size effect on transverse free vibrations of ultrafine nanothreads

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中国物理B:英文版 2023年第9期32卷 21-27页

作者：郑卓群李晗宿柱丁楠徐旭占海飞王立峰 State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Management Science and Information Engineering Jilin University of Finance and EconomicsChangchun 130117China College of Mathematics Jilin UniversityChangchun 130012China College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China School of Mechanical Medical and Process EngineeringQueensland University of TechnologyBrisbane 4001Australia

Due to their unique properties and appealing applications,low dimensional sp^(3)carbon nanostructures have attracted increasing attention *** on the beam theory and atomistic studies,this work carries out a comprehensive investigation on the vibrational properties of the ultrathin carbon nanothreads(NTH).size effect is observed in transverse free vibrations of *** quantify such effects,the modified couple stress theory(MCST)is utilized to modify the Timoshenko beam *** to the first four order frequencies of NTHs from atomistic simulations,the critical length scale parameter of MCST is calibrated as 0.1 *** is shown that MCST has minor effect on the first four order modal shapes,except for the clamped *** makes the modal shapes at the clamped boundary closer to those observed in atomistic *** study suggests that to some extent the MCST-based Timoshenko beam theory can well describe the transverse vibration characteristics of the ultrafine NTHs,which are helpful for designing and fabricating the NTH-based nanoscale mechanical resonators.

关键词： carbon nanothread size effect natural frequency modal shapes molecular dynamics simulation

size effect in the Al3Sc dispersoid-mediated precipitation and mechanical/electrical properties of Al-Mg-Si-Sc alloys

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Journal of Materials Science & Technology 2020年第22期54卷 78-84页

作者： Ruihong Wang Shengyu Jiang Bao'an Chen Zhixiang Zhu School of Materials Science and Engineering Xi'an University of TechnologyXi'an710048PR China State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute Co.Ltd.Beijing102209PR China

A significant size effect is found in the Al3 Sc dispersoid-mediated precipitation in an Al-Mg-Si-Sc *** the Al3 Sc dispersoid size smaller than about 40 nm,β " precipitates nucleate directly on the coherent dispersoids and grow by sacrificing the *** the dispersoid size greater than^40 nm,Q' and U2 phases are additionally produced that nucleate on the dislocations induced by the semi-/incoherent *** and electrical properties are highly sensitive to the Al3 Sc dispersoid-tuned *** co-precipitation of β",Q' and U2 phases leads to an obvious improvement in hardness and simultaneously in electrical conductivity.

关键词： Al-Mg-Si-Sc alloy Al3Sc dispersoids Precipitation size effect Hardness and conductivity

size effect of sandstone after high temperature under uniaxial compression

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Journal of Central South University 2015年第5期22卷 1901-1908页

作者：苏海健靖洪文茅献彪赵洪辉尹乾王辰 State Key Laboratory for Geomechanics & Deep Underground Engineering(China University of Mining & Technology) School of Mechanics and Civil Engineering China University of Mining & Technology

Uniaxial compression tests on sandstone samples with five different sizes after high temperature processes were performed in order to investigate the size effect and its evolution. The test results show that the density, longitudinal wave velocity, peak strength, average modulus and secant modulus of sandstone decrease with the increase of temperature, however, peak strain increases gradually. With the increase of ratio of height to diameter, peak strength of sandstone decreases, which has an obvious size effect. A new theoretical model of size effect of sandstone material considering the influence of temperature is put forward, and with the increase of temperature, the size effect is more apparent. The threshold decreases gradually with the increase of temperature, and the deviations of the experimental values and the theoretical values are between 0.44% and 6.06%, which shows quite a credibility of the theoretical model.

关键词： high temperature process sandstone size effect threshold

size effect of fullerene cages and encaged clusters in M3N@C2n

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Science China Chemistry 2009年第5期52卷 584-589页

作者： GAN LiHua School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China School of Chemistry and Chemical Engineering Southwest University Chongqing China

Based on the calculated findings that the sizes of encaged clusters determine the structures and the stability of C80-based trimetallic nitride fullerenes (TNFs), more extensive density functional theory calculations were performed on M3N@C68, M3N@C78 and M3N@C80 (M=Sc, Y and La). The calculated results demonstrated that the structures and stability undergo a transition with the increasing of the sizes of the cages and clusters. Sc3N is planar inside the three considered cages, Y3N is slightly pyramidal inside C68-6140 and C78-5 and planar inside I h C80-7, however, La3N is pyramidal inside all the three cages. Those cages with pyramidal clusters inside deformed considerably, compared with their parent cages. In these cases, the bonding of metallic atoms toward the cages does not play an impor-tant role, and the encaged cluster tends to be located inside the cages with the largest M-M and M-C distances so that the strain energy can be released mostly. These calculations revealed the size effect of fullerene cages and encaged clusters, and can explain the position priority of M3N inside fullerene cages and the differences in yield of M3N@C2n.

关键词： trimetallic nitride fullerenes (TNFs) density functional theory (DFT) size effect stability

size effect of deformation nanotwin bundles on their strengthening and toughening in heterogeneous nanostructured Cu

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Science China(Technological Sciences) 2021年第1期64卷 23-31页

作者： YOU ZeSheng LUO ShuSen LU Lei Herbert Gleiter Institute of Nanoscience Nanjing University of Science and TechnologyNanjing 210094China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Herein, we fabricated a heterogeneous nanostructured Cu with deformation nanotwin bundles(NTBs) embedded in a matrix of nanograins by means of dynamic plastic deformation at liquid nitrogen temperature. We conducted fracture mechanical measurements to investigate the effect of longitudinal length of the NTBs on their strengthening and toughening. Results suggest that an increase in the NTB length had a marginal influence on the tensile strength;however, it remarkably promoted both fracture initiation toughness and crack growth toughness. Longer NTBs are more effective not only in intrinsically enhancing crack tip plasticity by suppressing the strain localization and void nucleation but also in serving as crack bridges behind the crack front to extrinsically resist the fracture by shielding the crack tip.

关键词： fracture toughness nanotwins J-integral size effect toughening mechanism