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Application of interpolated double network model for carbon nanotube composites in electrothermal shape memory behaviors

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Acta Mechanica Sinica 2024年第8期40卷 133-153页

作者： Ting Fu Zhao Yan Li Zhang Ran Tao Yiqi Mao Department of engineering mechanics College of Mechanical and Vehicle EngineeringHunan UniversityChangsha410082China State Key Laboratory of Explosion Science and Technology Institute of Advanced Structure TechnologyBeijing Institute of TechnologyBeijing100081China

Multi-wall carbon nanotube filled shape memory polymer composite(MWCNT/SMC)possessed enhanced modulus,strength,and electric conductivity,as well as excellent electrothermal shape memory properties,showing wide design scenarios and engineering application *** thermoelectrically triggered shape memory process contains complex multi-physical mechanisms,especially when coupled with finite deformation rooted on micro-mechanisms.A multi-physical finite deformation model is necessary to get a deep understanding on the coupled electro-thermomechanical properties of electrothermal shape memory composites(ESMCs),beneficial to its design and wide *** into consideration of micro-physical mechanisms of the MWCNTs interacting with double-chain networks,a finite deformation theoretical model is developed in this work based on two superimposed network chains of physically crosslinked network formed among MWCNTs and the chemically crosslinked *** intact crosslinked chemical network is considered featuring with entropic-hyperelastic properties,superimposed with a physically crosslinked network where percolation theory is based on electric conductivity and electric-heating *** model is calibrated by experiments and used for shape recoveries triggered by heating and electric *** captures the coupled electro-thermomechanical behavior of ESMCs and provides design guidelines for MWCNTs filled shape memory polymers.

关键词： Shape memory polymer composite Viscoplastic constitutive relations Electro-thermomechanics Double network model Multiple shape memory

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Modeling Method of C/C-ZrC Composites and Prediction of Equivalent Thermal Conductivity Tensor Based on Asymptotic Homogenization

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工程与科学中的计算机建模(英文) 2024年第1期138卷 391-410页

作者： Junpeng Lyu Hai Mei Liping Zu Lisheng Liu Liangliang Chu Department of mechanics and engineering Structure Wuhan University of TechnologyWuhan430070China Hubei Key Laboratory of Theory and Application of Advanced Materials mechanics Wuhan University of TechnologyWuhan430070China

This article proposes a modeling method for C/C-ZrC composite *** to the superposition of Gaussian random field,the original gray model is obtained,and the threshold segmentation method is used to generate the C-ZrC inclusion ***,the fiber structure is added to construct the microstructure of the three-phase plain weave *** reconstructed inclusions can meet the randomness of the shape and have a uniform *** an algorithm based on asymptotic homogenization and finite element method,the equivalent thermal conductivity prediction of the microstructure finite element model was carried out,and the influence of component volume fraction on material thermal properties was *** sensitivity of model parameters was studied,including the size,mesh sensitivity,Gaussian complexity,and correlation length of the RVE model,and the optimal calculation model was *** results indicate that the volume fraction of the inclusion phase has a significant impact on the equivalent thermal conductivity of the *** the volume fraction of carbon fiber and ZrC increases,the equivalent thermal conductivity tensor gradually *** model can be used to explore the impact of materialmicrostructure on the results,and numerical simulations have studied the relationship between structure and performance,providing the possibility of designing microstructure based on performance.

关键词： 3D reconstruction randomheterogeneous media microstructure asymptotic homogenization effective properties

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Failure process and monitoring data of an extra-large landslide at the Nanfen Open-pit Iron Mine

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Journal of Mountain Science 2024年第9期21卷 2918-2938页

作者： WANG Jingxiang YANG Xiaojie TAO Zhigang HE Manchao SHEN Fuxin State Key Laboratory for Tunnel engineering China University of Mining and Technology(Beijing)Beijing 100083China School of mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China

An extra-large landslide occurred on June 19,2021,on the footwall slope of the Nanfen Open-pit Iron Mine in Liaoning Province,China,with a volume of approximately 1.2×107 *** elucidate the causative factors,development process,and destructive mechanisms of this catastrophic landslide,comprehensive field tests,investigations,and laboratory experiments were ***,the heavily weathered rock mass of the slope was intersected by faults and joint fissures,facilitating rainwater ***,the landslide contained a substantial clay mineral with highly developed micro-cracks and micro-pores,exhibiting strong water-absorption *** moisture content increased,the rock mass underwent softening,resulting in reduced ***,continuous heavy rainfall infiltration amplified the slope's weight,diminishing the weak structural plane's strength,leading to fracture propagation,slip plane penetration,and extensive tensile-shear and uplift failure of the *** study highlights poor geological conditions as the decisive factor for this landslide,with continuous heavy rainfall as the triggering ***,adverse environmental factors persistently affect the landslide,and deformation and failure continue to ***,it is imperative to urgently implement integrated measures encompassing slope reinforcement,monitoring,and early-warning to real-time monitor the landslide's deformation and deep mechanical evolution trends.

关键词： Landslide development process Extra-large landslide Heavy rainfall Failure characteristics Instability mechanism Landslide monitoring and early-warning

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Mechanism of high-preload support based on the NPR anchor cable in layered soft rock tunnels

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Journal of Mountain Science 2024年第4期21卷 1403-1418页

作者： SUI Qiru HE Manchao SHI Mengfan TAO Zhigang ZHAO Feifei ZHANG Xiaoyu State Key Laboratory for Tunnel engineering China University of Mining and Technology(Beijing)Beijing 100083China School of mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China

The control of large deformation problems in layered soft rock tunnels needs to solve *** roof problem is particularly severe among the deformation issues in *** study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large ***,we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor *** prominent roles of long and short NPR anchor cables in the support system are also *** results indicate the significance of high preload in controlling the roof of layered soft rock *** short NPR anchor cables effectively improve the integrity of the stratified soft rock layers,while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock ***,the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data.

关键词： Tunnel engineering Soft rock High-preload support NPR anchor cables

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Effect of Rigid Pitch Motion on Flexible Vibration Characteristics of a Wind Turbine Blade

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Energy engineering 2024年第10期121卷 2981-3000页

作者： Zhan Wang Liang Li Long Wang Weidong Zhu Yinghui Li Echuan Yang School of Mechanical engineering Anhui University of Science and TechnologyHuainan232001China School of mechanics and Optoelectronic Physics Anhui University of Science and TechnologyHuainan232001China Department of Mechanical engineering University of MarylandBaltimoreMD 21250USA School of mechanics and Aerospace engineering Southwest Jiaotong UniversityChengdu610031China School of Mechanical engineering Chongqing University of TechnologyChongqing400054China

Adynamic pitch strategy is usually adopted to improve the aerodynamic performance of the blade of awind *** dynamic pitch motion will affect the linear vibration characteristics of the ***,these influences have not been studied in previous *** this paper,the influences of the rigid pitch motion on the linear vibration characteristics of a wind turbine blade are *** blade is described as a rotating cantilever beam with an inherent coupled rigid-flexible vibration,where the rigid pitch motion introduces a parametrically excited vibration to the *** differential equations governing the nonlinear coupled pitch-bend vibration are proposed using the generalized Hamiltonian *** vibration characteristics of the inherent coupled rigid-flexible system are analyzed based on the combination of the assumed modes method and the multi-scales *** of static pitch angle,rotating speed,and characteristics of harmonic pitch motion on flexible natural frequencies andmode shapes are *** shows that the pitch amplitude has a dramatic influence on the natural frequencies of the blade,while the effects of pitch frequency and pith phase on natural frequencies are little.

关键词： Pitch motion wind turbine blade inherent rigid-flexible coupling vibration characteristics

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Mechanical behavior of 2G NPR bolt anchored rock samples under static disturbance loading

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Journal of Mountain Science 2024年第7期21卷 2494-2516页

作者： WANG Jiong JIANG Jian WANG Siyu CHANG Yiwen LIU Peng HE Manchao CHENG Shuang State Key Laboratory for Tunnel engineering China University of Mining and Technology(Beijing)Beijing 100083China School of mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China

The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering *** implementation of NPR(negative Poisson's ratio)bolts are capable of controlling large deformations in the surrounding rock *** paper focuses on studying the mechanical properties of the NPR bolt under static disturbance *** deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types(unanchored/PR anchored/2G NPR anchored)under static disturbance *** whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance *** the same time,the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count,energy,and *** deformation at the failure of the samples was calculated and analyzed by digital speckle *** findings indicate that the failure mode of rock is influenced by different types of *** peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5%when compared to the unanchored rock *** cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16%and 62.90%,*** maximum deformation of bearing capacity exhibits an increase of 59.27%,while the failure time demonstrates a delay of 42.86%.The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94%when compared to the rock anchored by PR(Poisson's ratio)*** cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16%and 43.86%,*** maximum deformation of the bearing capacity exhibits an increase of 50.43%,and the failure time demonstrates a delay of 32%.After anchoring by 2G NPR bolt,anchoring support effectively reduces the risk of damage caused by s

关键词： Anchored rock samples Static disturbance load Acoustic emission characteristics Digital speckle Negative Poisson's ratio

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Physics package based on intracavity laser cooling ^(87)Rb atoms for space cold atom microwave clock

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Chinese Physics B 2024年第7期33卷 22-26页

作者：邓思敏达任伟项静峰赵剑波李琳张迪万金银孟艳玲蒋小军李唐刘亮吕德胜 Aerospace Laser Technology and System Department Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China mechanics Chinese Academy of SciencesShanghai 201800China Center of Materials Science and Optoelectronics engineering University of Chinese Academy of SciencesBeijing 100049China

This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation,microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of 1.2×10^(-􀀀12) τ^(-1/2) with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.

关键词： atomic clock microgravity microwave cavity space station frequency stability

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Surrounding rock pressure in the tunnel portal section through moraine under freeze-thaw action

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Journal of Mountain Science 2024年第7期21卷 2480-2493页

作者： CHEN Zhimin LIU Baoli LIU Yaohui XU Jiangtao School of Civil engineering Lanzhou Jiaotong UniversityLanzhou 730070China CSCEC AECOM consultants Co. ltdLanzhou 730000China National and Local Joint engineering Laboratory of Road and Bridge engineering Disaster Prevention Technology Lanzhou Jiaotong UniversityLanzhou 730070China

Moraines,characterized by the accumulation of rock and soil debris transported by glacial activity,present unique challenges for tunnel construction,particularly in portal sections,due to prevailing geographical and climatic conditions that facilitate freeze-thaw *** these challenges,there is a dearth of studies investigating the influence of freeze-thaw action and water content on the mechanical properties of moraines,and no research on calculating surrounding rock pressure in moraine tunnels subjected to freeze-thaw *** this study,direct shear tests under freeze-thaw cycles were conducted to examine the effects of freeze-thaw cycles and water content on the mechanical properties of frozen moraine.A comprehensive parameter K,integrating the number of freeze-thaws and water content,was introduced to model cohesion *** on Terzaghi Theory,we propose an improved algorithm for calculating surrounding rock pressure at the portal section of moraine *** a tunnel as a case study,surrounding rock pressure was calculated under various conditions to validate the Improved Algorithm's *** results show that:(1)Strength loss exhibits a linear trend with the number of freeze-thaw cycles at water content levels of 4%and 8%,while at 12%water content,previous freeze-thaw cycles induce more significant damage to the soil.(2)Moraine saturation peaks between 8%and 12%water *** repeated freeze-thaw cycles,moraine shear strength initially increases before decreasing with varying water content.(3)The internal friction angle of moraine experiences slight reductions with prolonged freeze-thaw cycles,but both freeze-thaw cycles and water content significantly influence cohesion.(4)Vertical surrounding rock pressure increases after the initial freeze-thaw cycle,particularly with higher water content,although freeze-thaw cycles have minimal effect on it.(5)Freeze-thaw cycles lead to a substantial increase in lateral surrounding rock pre

关键词： Moraines Freeze-thaw cycles Direct shear test Surrounding rock pressure

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Failure mechanism and safety control technology of a composite strata roadway in deep and soft rock masses:a case study

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Journal of Mountain Science 2024年第7期21卷 2427-2444页

作者： ZHAO Chengwei ZHOU Hui SUN Xiaoming ZHANG Yong MIAO Chengyu WANG Jian State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China State Key Laboratory for Geomechanics and Deep Underground engineering China University of Mining and Technology(Beijing)Beijing 100083China School of mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China

The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor *** deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support *** to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding *** excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile *** numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was *** field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,*** demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.

关键词： 3DEC Composite strata roadway Soft rock NPR bolt and cable Asymmetric large deformation

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Energy Absorption by 3D-Printed Mesh Structures with a Negative Poisson’s Ratio

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 205-212页

作者： Wenyu Li Weiming Yang Mingze Li Xiang Zhang Ping Zhang Yucheng Zhao Peijian Chen Haishun Liu School of mechanics and Civil engineering China University of Mining and TechnologyXuzhou221116China School of Materials Sciences and Physics China University of Mining and TechnologyXuzhou221116China

A negative Poisson's ratio(NPR)structure represents optimal impact-resistance with applications in various fields,including the crash box in vehicles,which absorbs impact kinetic *** crash box is designed to deform in response to impact,increasing local structural density,which enhances impact resistance *** studies have only focused on the NPR effect in the plane dimension at low-speed *** studies have considered high-speed impact loads on three-dimensional NPR *** have developed two types of AlSi10Mg alloy energy-absorbing structures with NPR using three-dimensional printing technology,and have compared our systems with a conventional hexagonal mesh *** testing involved split-Hopkinson pressure bar measurements,which showed good agreement with dynamic numerical *** subjected to an impact load,the NPR structure exhibited better impact resistance and energy absorption compared with the positive Poisson's ratio *** proposed dual-layer hexagonal structure ensures an NPR effect while exhibiting higher strength and improved stability relative to the conventional concave hexagon structure.

关键词： Negative Poisson’s ratio Energy absorption 3D printing Split-Hopkinson pressure bar Numerical simulation

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