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Friction of graphene on a substrate with a cavity defect

Science China(Technological sciences) 2024年第9期67卷 2834-2841页

作者： ZHOU Peng HUO ZhanLei CHANG TienChong Shanghai Institute of Applied Mathematics and mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai Frontier Science Center of MechanoinformaticsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China The Center for Computational mechanics and engineering Applications Provincial Mechanics Experimental Teaching Demonstration CenterSchool of Civil EngineeringHebei University of EngineeringHandan 056038China Shanghai Institute of Aircraft mechanics and Control Tongji UniversityShanghai 200092China Joint-Research Center for Computational Materials Zhejiang LaboratoryHangzhou 311100China

The frictional behavior of supported graphene is known to be influenced by the physical properties and surface morphologies of the underlying substrate. However, it is unclear how a surface defect on the substrate affects the friction of supported graphene,and it is even unknown how to define the defect-induced friction force in this context. Here we conduct molecular dynamics(MD) simulations to investigate the friction between a square diamond slider and a graphene sheet supported by a copper substrate with a surface cavity defect. Our results demonstrate that the defect-induced friction exhibits a nonlinear increase with cavity size, while it decreases nonlinearly with slider size. We propose that the definition of defect-induced friction can be linked to the increase in friction work over the length of the slider, and is closely correlated to the defect-induced relative change in indentation dept. and the ratio of the cavity area to the contact area. These findings provide a comprehensive evaluation of the impact of a substrate cavity defect on the friction of supported graphene and offer insights that may have broader implications for understanding defect-induced friction in other two-dimensional materials.

关键词： friction graphene underneath substrate cavity defect

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Flow instability of supercritical hydrocarbon fuel in a multi-channel cooling system

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Chinese Journal of Aeronautics 2024年第2期37卷 283-295页

作者： Yichao JIN Kun WU Xuejun FAN Institute of Applied Physics and Computational Mathematics Beijing 100094China Institute of mechanics Chinese Academy of SciencesBeijing 100190China School of engineering Science University of Chinese Academy of SciencesBeijing 100049China

Thermally-induced flow instabilities are a critical issue in multi-channel regenerative cooling *** particular,the interactions between Density-Wave Oscillations(DWO)and Flow Maldistribution(FMD)can result in complex and disastrous instability *** study investigates the instability behaviors of hydrocarbon fluid in a four-channel system with a constant heat flux ratio using both frequency-and time-domain *** the heat flux increases,the in-tube flow sequentially destabilizes in each channel and converges to new equilibrium states,leading to the emergence of FMD *** also causes the system eigenvalue to change repeatedly from negative to positive rather than increasing ***,the system eigenvalues are between those of the two most unstable channels,indicating that the stability behavior of the entire system is dictated by the most unstable *** FMD occurs,flow oscillations are activated in channels with weak stability,and the in-tube flow is observed to evolve into various flow patterns,including stable flow,self-sustained oscillation,oscillation divergence,quasiperiodic oscillation,and oscillation *** novel instability mode of oscillation excursion involves a spontaneous transition of operating *** oscillates from an equilibrium state and then stabilizes at a new operational state after oscillation-induced ***,the newfound stable state may also be only temporary,with the in-tube flow regressing to the initial state,resulting in quasi-periodic oscillation.

关键词： Cooling Supercritical fluids Hydrocarbons Flow instability Flow maldistribution Density-wave oscillations

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Real-time arrival picking of rock microfracture signals based on convolutional-recurrent neural network and its engineering application

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Journal of Rock mechanics and Geotechnical engineering 2024年第3期16卷 761-777页

作者： Bing-Rui Chen Xu Wang Xinhao Zhu Qing Wang Houlin Xie State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of sciences Beijing100049China

Accurately picking P-and S-wave arrivals of microseismic(MS)signals in real-time directly influences the early warning of rock mass failure.A common contradiction between accuracy and computation exists in the current arrival picking ***,a real-time arrival picking method of MS signals is constructed based on a convolutional-recurrent neural network(CRNN).This method fully utilizes the advantages of convolutional layers and gated recurrent units(GRU)in extracting short-and long-term features,in order to create a precise and lightweight arrival picking ***,the synthetic signals with field noises are used to evaluate the hyperparameters of the CRNN model and obtain an optimal CRNN *** actual operation on various devices indicates that compared with the U-Net method,the CRNN method achieves faster arrival picking with less performance *** application of large underground caverns in the Yebatan hydropower station(YBT)project shows that compared with the short-term average/long-term average(STA/LTA),Akaike information criterion(AIC)and U-Net methods,the CRNN method has the highest accuracy within four sampling points,which is 87.44%for P-wave and 91.29%for S-wave,*** sum of mean absolute errors(MAESUM)of the CRNN method is 4.22 sampling points,which is lower than that of the other *** the four methods,the MS sources location calculated based on the CRNN method shows the best consistency with the actual failure,which occurs at the junction of the shaft and the second ***,the proposed method can pick up P-and S-arrival accurately and rapidly,providing a reference for rock failure analysis and evaluation in engineering applications.

关键词： Rock mass failure Microseismic event P-wave arrival S-wave arrival Deep learning

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Effect of intermittent joint distribution on the mechanical and acoustic behavior of rock masses

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Journal of Rock mechanics and Geotechnical engineering 2024年第4期16卷 1231-1244页

作者： Shuaiyang Fu Haibo Li Liwang Liu Di Wu Ben Wang State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of sciences Beijing100049China

The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic *** this study,numerical models of rock masses incorporating intermittent joints with different numbers and dip angles were produced using the finite element method(FEM)with the intrinsic cohesive zone model(ICZM).Then,the uniaxial compressive and wave propagation simulations were *** results indicate that the joint number and dip angle can affect the mechanical and acoustic properties of the *** uniaxial compressive strength(UCS)and wave velocity of rock masses decrease monotonically as the joint number ***,the wave velocity grows monotonically as the joint dip angle *** the joint dip angle is 45°–60°,the UCS of the rock mass is lower than that of other dip *** wave velocity parallel to the joints is greater than that perpendicular to the *** the dip angle of joints remains unchanged,the UCS and wave velocity are positively *** the joint dip angle increases,the variation amplitude of the UCS regarding the wave velocity *** reveal the effect of the joint distribution on the velocity,a theoretical model was also *** to the theoretical wave velocity,the change in wave velocity of models with various joint numbers and dip angles was consistent with the simulation ***,a theoretical indicator(*** tensor)was adopted to analyze the variation of the wave velocity and UCS.

关键词： Stochastic joints Intrinsic cohesive zone model Uniaxial compressive strength(UCS) Wave propagation Fabric tensor

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A novel relationship between elastic modulus and void ratio associated with principal stress for coral calcareous sand

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Journal of Rock mechanics and Geotechnical engineering 2024年第3期16卷 1033-1048页

作者： Ran Gao Jianhong Ye State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of sciences Beijing100049China

Elastic moduli,*** modulus G and bulk modulus K,are important parameters of geotechnical materials,which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical *** this study,a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloadingreloading tests are conducted to study several typical mechanical properties of coral calcareous sand(CCS),and the void ratio evolution during loading,unloading and *** test results show that the stress-strain curves during multiple unloading processes are almost parallel,and their slopes are much greater than the deformation modulus at the initial stage of *** relationship between the confining pressure and the volumetric strain can be defined approximately by a hyperbolic equation under the condition of monotonic loading of confining *** the condition of confining pressure unloading,the evolution of void ratio is linear in the e-lnp0 plane,and these lines are a series of almost parallel lines if there are multiple processes of *** on the experimental results,it is found that the modified Hardin formulae for the elastic modulus estimation have a significant deviation from the tested values for *** on the experimental results,it is proposed that the elastic modulus of soils should be determined by the intersection line of two spatial surfaces in the G/K-e-p’/pa space(pa:atmosphere pressure).“Ye formulation”is further proposed for the estimation of the elastic modulus of *** new estimation formulation for soil elastic modulus would provide a new method to accurately describe the mechanical behavior of granular soils.

关键词： Coral calcareous sand(CCS) Elastic shear modulus Elastic bulk modulus Triaxial test Estimation formulation Ye formulation

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Estimating shear strength of high-level pillars supported with cemented backfilling using the HoekeBrown strength criterion

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Journal of Rock mechanics and Geotechnical engineering 2024年第2期16卷 454-469页

作者： Kaizong Xia Congxin Chen Xiumin Liu Yue Wang Xuanting Liu Jiahao Yuan State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of sciences Beijing100049China

Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining *** the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(*** and internal friction angle)when they are supported by cemented *** this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure *** analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be *** value of s3max predicted using the proposed method is generally less than 3 *** this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb *** proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,*** situation in which the cohesion value is too large and the friction angle is too small can effectively be *** proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB *** shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical *** numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.

关键词： Deep metal mines High-level pillars HoekeBrown strength criterion Cemented backfilling Confining pressure Shear strength

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A review of in situ carbon mineralization in basalt

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Journal of Rock mechanics and Geotechnical engineering 2024年第4期16卷 1467-1485页

作者： Xiaomin Cao Qi Li Liang Xu Yongsheng Tan 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

Global warming has greatly threatened the human living environment and carbon capture and storage(CCS)technology is recognized as a promising way to reduce carbon *** storage is considered a reliable option for long-term carbon *** rich in alkaline earth elements facilitates rapid and permanent CO_(2) fixation as ***,the complex CO_(2)-fluid-basalt interaction poses challenges for assessing carbon storage *** different reaction conditions,the carbonation products and carbonation rates *** mineralization reactions also induce petrophysical and mechanical responses,which have potential risks for the long-term injectivity and the carbon storage safety in basalt *** this paper,recent advances in carbon mineralization storage in basalt based on laboratory research are comprehensively *** assessment methods for carbon storage potential are introduced and the carbon trapping mechanisms are investigated with the identification of the controlling *** in pore structure,permeability and mechanical properties in both static reactions and reactive percolation experiments are also *** study could provide insight into challenges as well as perspectives for future research.

关键词： Carbon mineralization Basalt CO_(2)-fluid-basalt interaction Petrophysical evolution Mechanical response Carbon capture and storage(CCS)

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A Review on Vibration Control of Multiple Cylinders Subjected to FlowInduced Vibrations

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China Ocean engineering 2024年第2期38卷 183-197页

作者： XU Wan-hai MA Ye-xuan State Key Laboratory of Hydraulic engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300350China Institute of mechanics Chinese Academy of SciencesBeijing 100190China

The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering *** FIV suppression is of great importance for the security of many cylindrical *** active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated *** to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV *** efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two *** control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control *** FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and *** FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence *** research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.

关键词： flow-induced vibration vibration control multiple cylinders tandem side-by-side staggered

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Swelling pressure evolution characterization of strong expansive soil considering the influence of reserved expansion deformation

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Journal of Mountain Science 2024年第1期21卷 252-270页

作者： LI Tianguo KONG Lingwei GUO Aiguo YAN Junbiao 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

Numerous engineering cases have demonstrated that the expansive soil channel slope remains susceptible to damage with the implementation of a rigid or closed protective structure. It is common for the protective structure to experience bulging failure due to excessive swelling pressure. To investigate the swelling pressure properties of expansive soil, the constant volume test was employed to study the influence of water content and reserved expansion deformation on the characteristics of swelling pressure in strong expansive soils, and also to explore the evolution mechanism of the swelling pressure. The findings demonstrate that the swelling pressure-time curve can be classified into swelling pressure-time softening and swelling pressure-time stability type. The swelling pressuretime curve of the specimen with low water content is the swelling pressure-time softening type, and the softening level will be weakened with increasing reserved expansion deformation. Besides, the maximum swelling pressure Psmax decreases with increasing water content and reserved expansion deformation, especially for expansion ratio η from 24% to 37%. The reserved deformation has little effect on reducing Psmax when it is beyond 7% of the expansion rate. The specimen with low water content has a more homogeneous structure due to the significant expansion-filling effect, and the fracture and reorganization of the aggregates in the specimens with low water content cause the swelling pressure-time softening behavior. In addition, the proposed swelling pressure-time curve prediction model has a good prediction on the test results. If necessary, a deformation space of about 7% expansion rate is recommended to be reserved in the engineering to reduce the swelling pressure except for keeping a stable water content.

关键词： Expansive soil Swelling pressure Reserved expansion deformation Water content

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Cavitation research with computational fluid dynamics:From Euler-Euler to Euler-Lagrange approach

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Journal of Hydrodynamics 2024年第1期36卷 1-23页

作者： Bin Ji Zi-yang Wang Huai-yu Cheng Rickard E.Bensow State Key Laboratory of Water Resources engineering and Management Wuhan UniversityWuhan430072China Department of mechanics and Maritime sciences Chalmers University of TechnologyGothenburgSweden

Unsteady cavitating flow often contains vapor structures with a wide range of different length scales,from micro-bubbles to large cavities,which issues a big challenge to precisely investigate its evolution mechanism by computational fluid dynamics(CFD)*** present work reviews the development of simulation methods for cavitation,especially the emerging Euler-Lagrange ***,the progress of the numerical investigation of hot and vital issues is discussed,including cavitation inception,cloud cavitation inner structure and its formation mechanism,cavitation erosion,and cavitation *** is indicated that the Euler-Lagrange method can determine cavitation inception point *** cloud cavitation,the Euler-Lagrange method can reveal the source of microbubbles and their distribution law inside the shedding *** method also has advantages and great potential in assessing cloud cavitation-induced erosion and *** the ever-growing demands of cavitation simulation accuracy in basic research and engineering applications,how to improve the Euler-Lagrange method’s stability and applicability is still an open *** further promote the application of this advanced CFD simulation technology in cavitation research,some key issues are to be solved and feasible suggestions are put forward for further work.

关键词： numerical simulation Euler-Euler method Euler-Lagrange method bubble dynamicsgy,Gothenburg,Sweden

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