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Analysis of the damage mechanism of strainbursts by a global-local modeling approach

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1671-1696页

作者： Jun Wang Derek B.Apel artur Dyczko Andrzej Walentek Stanislaw Prusek Huawei Xu Chong Wei School of Mining and Petroleum Engineering University of AlbertaEdmontonAlbertaT6G 2R3Canada Jastrze˛bska Spółka We˛glowa S.A.Group Aleja Jana Pawła II 4Jastrze˛bie-Zdrój44-330Poland Central Mining Institute Plac GwarkówKatowice140-166Poland

Strainburst is the most common type of rockbursts.The research of strainburst damage mechanisms is helpful to improve and optimize the rock support design in the burst-prone ground.In this study,an improved global-local modeling approach was first adopted to study strainburst damage mechanisms.The extracted stresses induced by multiple excavations from a three-dimensional(3D)global model established by fast Lagrangian analysis of continua in 3 dimensions(FLAC3D)are used as boundary conditions for a two-dimensional(2D)local model of a deep roadway built by universal distinct element code(UDEC)to simulate realistic stress loading paths and conduct a detailed analysis of rockburst damage from both micro and macro perspectives.The results suggest that the deformation and damage level of the roadway gradually increase with the growth of surrounding rock stress caused by the superposition of mining-or excavation-induced stresses of the panel and nearby roadways.The significant increase of surrounding rock stresses will result in more accumulated strain energy in two sidewalls,providing a necessary condition for the strainburst occurrence in the dynamic stage.The strainburst damage mechanism for the study site combines three types of damage:rock ejection,rock bulking,and rockfall.During the strainburst,initiation,propagation,and development of tensile cracks play a crucial role in controlling macroscopic failure of surrounding rock masses,although the shear crack always accounts for the main proportion of damage levels.The deformation and damage level of the roadway during a strainburst positively correlate with the increasing peak particle velocities(PPVs).The yielding steel arch might not dissipate kinetic energy and mitigate strainburst damage effectively due to the limited energy absorption capacity.The principles to control and mitigate strainburst damage are proposed in this paper.This study presents a systematic framework to investigate strainburst damage mechanisms using the global-local modeling approach.

关键词： Strainburst Numerical modeling Damage mechanism Finite difference method(FDM) Discrete element method(DEM) Underground mining

Deformation characteristics and inertial effect of complex aluminum alloy sheet part under impact hydroforming:experiments and numerical analysis

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Advances in Manufacturing 2023年第2期11卷 311-328页

作者： Liang-Liang Xia Shi-Hong Zhang Yong Xu Shuai-Feng Chen Boris B.Khina artur I.Pokrovsky Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016People's Republic of China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230000People's Republic of China Physical-Technical Institute National Academy of Science of Belarus220141MinskBelarus

Impact hydroforming(IHF),as a novel sheet metal forming technology with the advantages of high strain rate forming and flexible liquid loading,is highly suitable for efficiently manufacturing aluminum complex-shaped sheet parts.In this paper,deformation characteristics of complex sheet parts under IHF are systematically investigated.The mechanical properties of 2024 aluminum alloy under a wide range of strain rates(10-3 s-1–3.3×103 s-1)were studied.It indicated that the elongation of 2024 aluminum alloy was improved by 116.01%under strain rates of 3.306-×-103 s-1,referring to 10-3 s-1.Further,a complex-shaped part with symmetrical and asymmetrical structures was selected.The deformation characteristics of sheet and role of inertial effect under IHF were investigated with well-developed solid–liquid coupling finite element(SLC-FE)model with high accuracy.Differentiating deformation tendency is found for symmetrical structure with notably prior deformation at central zone,showing a“bulging”profile at initial forming stage.Whereas,synchronous deformation is presented for asymmetrical structure with a“flat”profile.Additionally,distinctive inertial effect was observed at different positions change for both symmetrical and asymmetrical structures,in which lower values were resulted at their central regions.Meanwhile,the inertial effect evolved with the impacting speed.Specially,larger difference of inertial effect was observed with increasing impacting speed.

关键词： 2024 aluminum alloy Impact hydroforming High strain rate Inertial effect

Introduction to investigations of the negative corona and EHD flow in gaseous two-phase fluids

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Plasma Science and Technology 2018年第5期20卷 147-156页

作者： Jerzy MIZERACZYK artur BERENDT Department of Marine Electronics Gdynia Maritime University Institute of Fluid Flow Machinery Polish Academy of Sciences

Research interests have recently been directed towards electrical discharges in multi-phase environments.Natural electrical discharges,such as lightning and coronas,occur in the Earth＇s atmosphere,which is actually a mixture of gaseous phase（air） and suspended solid and liquid particulate matters（PMs）.An example of an anthropogenic gaseous multi-phase environment is the flow of flue gas through electrostatic precipitators（ESPs）,which are generally regarded as a mixture of a post-combustion gas with solid PM and microdroplets suspended in it.Electrical discharges in multi-phase environments,the knowledge of which is scarce,are becoming an attractive research subject,offering a wide variety of possible discharges and multi-phase environments to be studied.This paper is an introduction to electrical discharges in multi-phase environments.It is focused on DC negative coronas and accompanying electrohydrodynamic（EHD） flows in a gaseous two-phase fluid formed by air（a gaseous phase） and solid PM（a solid phase）,run under laboratory conditions.The introduction is based on a review of the relevant literature.Two cases will be considered：the first case is of a gaseous two-phase fluid,initially motionless in a closed chamber before being subjected to a negative corona（with the needle-toplate electrode arrangement）,which afterwards induces an EHD flow in the chamber,and the second,of a gaseous two-phase fluid flowing transversely with respect to the needle-to-plate electrode axis along a chamber with a corona discharge running between the electrodes.This review-based introductory paper should be of interest to theoretical researchers and modellers in the field of negative corona discharges in single-or two-phase fluids,and for engineers who work on designing EHD devices（such as ESPs,EHD pumps,and smoke detectors）.

关键词： DC negative corona discharge Trichel pulses gaseous two-phase flow air withsuspended particle flow ESP EHD

The Impact of Bed Temperature on Heat Transfer Characteristic between Fluidized Bed and Vertical Rifled Tubes

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Journal of Thermal Science 2016年第5期25卷 476-483页

作者： artur Blaszczuk Wojciech Nowak Czestochowa University of Technology Institute of Advanced Energy Technologies Dabrowskiego 73 AGH University Science and Technology Faculty of Energy and Fuels Czarnowiejska 30

In the present work,the heat transfer study focuses on assessment of the impact of bed temperature on the local heat transfer characteristic between a fluidized bed and vertical rifled tubes(38mm-O.D.) in a commercial circulating fluidized bed(CFB) boiler.Heat transfer behavior in a 1296t/h supercritical CFB furnace has been analyzed for Geldart B particle with Sauter mean diameter of 0.219 and 0.246 mm.The heat transfer experiments were conducted for the active heat transfer surface in the form of membrane tube with a longitudinal fin at the tube crest under the normal operating conditions of CFB boiler.A heat transfer analysis of CFB boiler with detailed consideration of the bed-to-wall heat transfer coefficient and the contribution of heat transfer mechanisms inside furnace chamber were investigated using mechanistic heat transfer model based on cluster renewal approach.The predicted values of heat transfer coefficient are compared with empirical correlation for CFB units in large-scale.

关键词：循环流化床(CFB)锅炉传热特性垂直床温循环流化床锅炉纵向翅片管影响评估内螺纹管

On Plane Stress State and Stress Free Deformation of Thick Plate with FGM Interface under Thermal Loading

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Journal of Thermal Science 2016年第5期25卷 440-448页

作者： Damian Szubartowski artur Ganczarski Department of Mechanical Engineering Institute of Applied MechanicsCracow University of Technology

This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading.First,the Sneddon-Lockett theorem on the plane stress state in an isotropic infinite thick plate is generalized for a case of FGM problem in which all thermo-mechanical properties are optional functions of depth co-ordinate.The proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations that reduces it to the plane stress state problem.Then an existence of the purely thermal deformation is proved in two ways:first,it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient,second,proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation if only stress field is homogeneous in domain and at boundary.Finally,couple examples of application to an engineering problem are presented.

关键词：平面应力状态功能梯度材料载荷作用厚板自由变形热弹性方程界面热弹性变形

Hepatocellular carcinoma extracellular vesicle ECG score as a diagnostic tool close to the ideal

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Hepatobiliary Surgery and Nutrition 2023年第6期12卷 930-932页

作者： artur Słomka Tudor Mocan Arnulf G.Willms Veronika Lukacs-Kornek Miroslaw T.Kornek Department of Pathophysiology Nicolaus Copernicus University in ToruńLudwik Rydygier Collegium MedicumBydgoszczPoland UBBMed Department Babes-Bolyai UniversityCluj-NapocaRomania Department of Gastroenterology “Prof.Dr.Octavian Fodor”Regional Institute of Gastroenterology and HepatologyCluj-NapocaRomania Department of General and Visceral Surgery German Armed Forces HospitalHamburgGermany Institute of Molecular Medicine and Experimental Immunology University Hospital of the Rheinische Friedrich-Wilhelms-UniversityBonnGermany Department of Internal Medicine I University Hospital of the Rheinische Friedrich-Wilhelms-UniversityBonnGermany

Introduction In recent decades,numerous indicators for early detection and monitoring of hepatocellular carcinoma(HCC)have been suggested and published in reputable journals.These markers have gained recognition and endorsement from prominent international associations such as the European Association for the Study of the Liver(EASL),the Asian Pacific Association for the Study of the Liver(APASL),as well as national professional organizations like the American Association for the Study of Liver Diseases(AASLD),among others.

关键词： Extracellular vesicles(EVs) hepatocellular carcinoma(HCC) early-stage biomarker

Real prospects for the development of power technologies based on renewable energy sources in Poland

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Frontiers in Energy 2017年第2期11卷 168-174页

作者： Slawomir DYKAS artur SZYMANSKI Xiaoshu CAI Silesian University of Technology Institute of Power Engineering andTurbomachinery Konarskiego 20 44-100 Gliwice Poland Institute of Particle and Two-Phase Flow Measurement University ofShanghai for Science and Technology Shanghai 200093 China

In Poland more than 40% of the power units have been operating for over 40 years now and more than 10% are over 50 years old, which indicates a high degree of decrease in the value of the energy sector. An analysis of the energy market shows that every year a new power plant should be built with a capacity of 1000 MW to ensure the national energy security. An energy market research indicates that in Poland the structure of energy production is changing in recent years-the share of fossil (solid) fuels in electricity and heat production was approximately 88% in 2009, while in 2004 it reached 93%. According to the analysis of the market, it can be seen that conventional energy, mainly based on coal and lignite, has been the most important segment of the sector for a long time. In this paper the prospects for the development of power technologies based on renewable energy sources (RES) in Poland are presented.

关键词： renewable energy sources energy sector energy mix Poland

Explicit bivariate rate functions for large deviations in AR(1)and MA(1)processes with Gaussian innovations

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Probability, Uncertainty and Quantitative Risk 2023年第2期8卷 177-212页

作者： Maicon J.Karling artur O.Lopes Sílvia R.C.Lopes Mathematics and Statistics Institute Federal University of Rio Grande do Sul91500-900 Porto AlegreRSBrazil

We investigate the large deviations properties for centered stationary AR(1)and MA(1)processes with independent Gaussian innovations,by giving the explicit bivariate rate functions for the sequence of two-dimensional random vectors.Via the Contraction Principle,we provide the explicit rate functions for the sample mean and the sample second moment.In the AR(1)case,we also give the explicit rate function for the sequence of two-dimensional random vectors(W_(n))n≥2=(n^(-1(∑_(k=1)^(n)X_(k),∑_(k=1)^(n)X_(k)^(2))))_(n∈N)n≥2,but we obtain an analytic rate function that gives different values for the upper and lower bounds,depending on the evaluated set and its intersection with the respective set of exposed points.A careful analysis of the properties of a certain family of Toeplitz matrices is necessary.The large deviations properties of three particular sequences of one-dimensional random variables will follow after we show how to apply a weaker version of the Contraction Principle for our setting,providing new proofs for two already known results on the explicit deviation function for the sample second moment and Yule-Walker estimators.We exhibit the properties of the large deviations of the first-order empirical autocovariance,its explicit deviation function and this is also a new result.

关键词： Autoregressive processes Empirical autocovariance Large deviations Moving average processes Sample moments Toeplitz matrices Yule-Walker estimator

Parameter estimation in Manneville–Pomeau processes

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Probability, Uncertainty and Quantitative Risk 2023年第2期8卷 213-234页

作者： Barbara P.Olbermann Sílvia R.C.Lopes artur O.Lopes Faculdade de Matemática-PUCRS 90650-002 Porto AlegreRSBrazil Instituto de Matemática e Estatística-UFRGS 91500-900 Porto AlegreRSBrazil

In this paper,we study a class of stochastic processes{X_(t)}t∈N,where X_(t)=φ■T_(s)^(t)(X_(0))is obtained from the iterations of the transformation T_(s),invariant for an ergodic probabilityμ_(s)on[0,1]and a certain constant by partial functionφ:[0,1]→R.We consider here the family of transformations T_(s):[0,1]→[0,1]indexed by a parameters>0,known as the Manneville–Pomeau family of transformations.The autocorrelation function of the resulting process decays hyperbolically(or polynomially)and we obtain efficient methods to estimate the parameter s from a finite time series.As a consequence,we also estimate the rate of convergence of the autocorrelation decay of these processes.We compare different estimation methods based on the periodogram function,the smoothed periodogram function,the variance of the partial sum,and the wavelet theory.To obtain our results we analyzed the properties of the spectral density function and the associated Fourier series.

关键词： Manneville–Pomeau maps Long and not so long dependence Estimation Autocorrelation decay Spectral density function