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Shock-induced fracture of dolomite rock in small-scale blast tests

Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1823-1835页

作者： pawel baranowski Michal Kucewicz Mateusz Pytlik Jerzy Matachowski Military University of Technology Faculty of Mechanical EngineeringInstitute of Mechanics&Computational Engineering2 Gen.S.Kaliskiego Street00-908WarsawPoland Central Mining Institute Conformity Assessment Body40-166KatowicePoland

This paper attempts to study dolomite failure using small-scale blast tests.The experimental setup consisted of a cylindrical specimen with a central borehole fitted with a detonation cord inside a copper pipe.The specimen was confined using lead material.During the test,acceleration histories were recorded using sensors placed on the lead confinement.The results showed that heterogeneity and initial cracks significantly influenced the observed failure and cracking patterns.The tests were numerically represented using the previously validated Johnson-HolmquistⅡ(JH-2)constitutive model.The properties of the detonation cord were first determined and verified in a special test with a lead specimen to compare the deformation in the test with that of numerical simulation.Then,the small-scale blast test was simulated,and the failure of the dolomite was compared with the test observations.Comparisons of acceleration histories,scabbing failure,and number of radial cracks and crack density confirmed the overall repeatability of the actual testing data.It is likely that the proposed model can be further used for numerical studies of blasting of dolomite rock.

关键词： Johnson-HolmquistⅡmodel(JH-2) Rock Blasting Fracture Small-scale test

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Dolomite fracture modeling using the Johnson-Holmquist concrete material model:Parameter determination and validation

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 335-350页

作者： Michal Kucewicz pawel baranowski Jerzy Maachowski Faculty of Mechanical Engineering Institute of Mechanics and Computational EngineeringMilitary University of Technology2 Gen.S.Kaliskiego StreetWarsaw00-908Poland

In this paper,the Johnson-Holmquist concrete(JHC)constitutive model is adopted for modeling and simulating the fracture of dolomite.A detailed step-by-step procedure for determining all required parameters,based on a series of experiments under quasi-static and dynamic regimes,is proposed.Strain rate coefficients,failure surfaces,equations of state and damage/failure constants are acquired based on the experimental data and finite element analyses.The JHC model with the obtained parameters for dolomite is subsequently validated using quasi-static uniaxial and triaxial compression tests as well as dynamic split Hopkinson pressure bar(SHPB)tests.The influence of mesh size is also analyzed.It shows that the simulated fracture behavior and waveform data are in good agreement with the experimental data for all tests under both quasi-static and dynamic loading conditions.Future studies will implement the validated JHC model in small-and large-scale blasting simulations.

关键词： Johnson-Holmquist concrete(JHC)model Rock modeling Dolomite Constitutive modeling Split Hopkinson pressure bar(SHPB) Fracture Triaxial compression

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The study of the interactions between graphene and Ge（001）/Si（001）

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Nano Research 2017年第11期10卷 3648-3661页

作者： pawel Dabrowski Maciej Rogala Iwona Pasternak Jacek baranowski Wlodzimierz Strupinski Marek Kopciuszynski Ryszard Zdyb Mieczyslaw Jalochowski Iaroslav Lutsyk Zbigniew Klusek Department of Solid State Physics Faculty of Physics and Applied Informatics University of Lodz Pomorska 149/153 90-236 Lodz Poland Institute of Electronic Materials Technology Wolczynska 133 01-919 Warsaw Poland Institute of Physics Maria Curie-Sklodowska University pl.M.Curie-Sklodowskiej 1 20-031 Lublin Poland Department of Solid State Physics Yuriy Fedkovych Chernivtsi National University Kotsubinsky 2 58012 Chernivtsi Ukraine

The interaction between graphene and germanium surfaces was investigated using a combination of microscopic and macroscopic experimental techniques and complementary theoretical calculations.Density functional theory （DFT） calculations for different reconstructions of the Ge（001） surface showed that the interactions between graphene and the Ge（001） surface introduce additional peaks in the density of states,superimposed on the graphene valence and conduction energy bands.The growth of graphene induces nanofaceting of the Ge（001） surface,which exhibits well-organized hill and valley structures.The graphene regions covered by hills are of high quality and exhibit an almost linear dispersion relation,which indicates weak graphene-germanium interactions.On the other hand,the graphene component occupying valley regions is significantly perturbed by the interaction with germanium.It was also found that the stronger graphene-germanium interaction observed in the valley regions is connected with a lower local electrical conductivity.Annealing of graphene/Ge（001）/Si（001） was performed to obtain a more uniform surface.This process results in a surface characterized by negligible hill and valley structures;however,the graphene properties unexpectedly deteriorated with increasing uniformity of the Ge（001） surface.To sum up,it was shown that the mechanism responsible for the formation of local conductivity inhomogeneities in graphene covering the Ge（001） surface is related to the different strength of graphene-germanium interactions.The present results indicate that,in order to obtain high-quality graphene,the experimental efforts should focus on limiting the interactions between germanium and graphene,which can be achieved by adjusting the growth conditions.

关键词： chemical vapor deposition,surface reconstruction,scanning tunneling microscopy,chemical bonding,first-principles calculation

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