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A DEM investigation on simple shear behavior of dense granular assemblies

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Journal of Central South University 2015年第12期22卷 4844-4855页

作者：史旦达薛剑峰赵振营史跻宇 School of Ocean Science and Engineering Shanghai Maritime University School of Engineering and Information Technology Federation University Australia Jiangsu Zhongshe Engineering Consultancy Group

A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element *** series of numerical tests were performed to examine the effects of initial porosity,vertical stress and particle shape on simple shear behavior of the samples,*** was found that during simple shear the directions of principal stress and principal strain increment rotate differently with shear strain *** non-coaxiality between the two directions decreases with strain level and may greatly affect the shear behavior of the assemblies,especially their peak friction *** numerical modelling also reveals that the rotation of the principal direction of fabric anisotropy lags behind that of the major principal stress direction during simple shear,which is described as fabric hyteresis *** degrees of fabric and interparticle contact force anisotropies increase as particle angularity increases,whereas the orientations of these anisotropies have not been significantly influenced by particle *** extended stress–dilatancy relationship based on ROWE-DAVIS framework was proposed to consider the non-coaxiality effect under principal stress *** model was validated by present numerical results as well as some published physical test and numerical modelled data.

关键词： simple shear non-coaxiality fabric anisotropy shear strength discrete element method

Technical Development of simple shear Deformation Experiments Using a Deformation-DIA Apparatus

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Journal of Earth Science 2010年第5期21卷 523-531页

作者： Tomohiro Ohuchi Takaaki Kawazoe Norimasa Nishiyama Yu Nishihara Tetsuo Irifune Geodynamics Research Center Ehime University Senior Research Fellow Center Ehime University

Technical developments for simple shear deformation experiments at high pressures were made. The newly designed cell assembly can be compressed by deformation-DIA apparatuses with the MA 6-6 system, which consists of six second-stage tungsten carbide anvils （with a truncated edge length of 5 mm） and the anvil guide. Deformation of samples was barely observed during the compression process, showing that the shear strain of the deformed samples can be measured by the rotation of a strain marker. simple shear deformation experiments on anhydrous and hydrous oli- vine aggregates were conducted under upper mantle conditions （pressures of 5.2-7.6 GPa and temperatures of 1 473-1 573 K）, and sample deformation with a shear strain of 7=0.8-1.2 was successfully achieved at a shear strain rate of 4.0×10^-5-7.5×10^-5 s^-1. The present study extended the pressure range of simple shear deformation experiments in the deformation-DIA apparatus from 3 GPa in an early study to 7.6 GPa at high temperatures.

关键词： simple shear deformation deformation-DIA MA 6-6 upper mantle.

Prediction of Buckling of Plain Knitted Fabric Sheets Subjected to simple shear in Wale Direction

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Transactions of Tianjin University 2007年第6期13卷 391-397页

作者：张义同敖涛徐家福 School of Mechanical Engineering Tianjin University

Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined.

关键词： knitted fabric knitting structure buckling wrinkling simple shear

Influence of strain rate on grain refinement and texture evolution under complex shear stress conditions

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Journal of Magnesium and Alloys 2023年第7期11卷 2558-2584页

作者： Zhaocan Li Guoqin Wu Jianmin Yu Jiebing Wang Jingjing Han Huiyong Cui Zhimin Zhang College of Materials Science and Engineering North University of China3 Xueyuan RoadTaiyuan 030051China Science and Technology on Space Physics Laboratory China Academy of Launch Vehicle TechnologyBeijing 100076China

The effects of different complex shear stress conditions on grain refinement and texture evolution of Mg-13Gd-4Y-2Zn-0.5Zr alloy were *** increasing strain rate,the average grain size of compression-shear(CS)and compression-torsion(CT)samples are decreased,and the grain size of dynamic recrystallization(DRX)grains is also *** is because that the precipitation number ofβphases is increased,and the hindering effect on grain growth can be significantly *** DRX fractions of CS and CT samples are decreased with increased strain *** low DRX fraction at high strain rate is related to the insufficient time for grains to *** DRX process can be promoted by the PSN mechanism of second phases,and the grain growth can be restricted by the pinning *** the same time,the texture strength is enhanced as the strain rate ***,the kinking degree of lamellar long-period stacking ordered(LPSO)phases is *** complex shear stress conditions,non-basal slip,especially pyramidal slip,is easily activated and the texture is deflected *** with the CS samples,CT samples have smaller average grain size,higher DRX fraction,and lower texture strength for a certain strain *** is because that the equivalent stress of the CT sample is larger,the stress triaxiality is smaller,so more serious dislocations are piled up near grain boundaries and second *** the same time,since CT sample was sheared with torsion,the dislocation movement path can be called“rotational dislocation accumulation”,and the longer distribution path of the CT sample is generated,so more sub-grains and low-angle grain boundaries(LAGBs)are *** with the CS sample,more huge-angle grain boundaries(HAGBs)and DRX grains are formed from grain boundary to grain interior,so better grain refinement effect is achieved.

关键词： simple shear Compression-shear Compression-torsion Grain refinement Texture evolution ASB

The Early Mesozoic NE-SW Extensional Model and Exhumation Processes at the Southeastern Margin of the Central Asian Orogenic Belt:Insights from the Strain and Kinematic Vorticity Analysis of the Sonid Zuoqi Ductile Detachment Zone

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Acta Geologica Sinica(English Edition) 2024年第5期98卷 1141-1153页

作者： LI Jianbo SONG Zhijie LEI Hengcong ZENG Tao East China University of Technology Nanchang 344000China

The Sonid Zuoqi ductile detachment zone is located at the southeastern margin of the Central Asian orogenic belt(CAOB),striking EW and dipping to the *** major rock type of the Sonid Zuoqi ductile detachment zone is mylonite derived from *** sequence of mylonite features is:(1)S and C foliations of mylonite,and(2)extensional crenulation cleavage(ecc)or C′and the kinematic vorticity(Wk)value changed from 0.70 to 0.95 and from 0.37 to 0.69,respectively;the strain type of the mylonites within the Sonid Zuoqi ductile detachment zone is compressional to planar *** strong deformation mylonite and Halatu plutons yielded a zircon U-Pb age of 244 Ma and a zircon(U-Th)/He age of 214 Ma,*** on the strain and kinematic vorticity analysis,together with the zircon U-Pb and zircon(U-Th)/He ages and the regional tectonic background,the study area experienced three stage evolution:tangential simpleshear(244 Ma),simple-shear-dominated general shear represented by upper crustal extension(224 Ma)and pure-shear-dominated general shear represented by the Halatu pluton doming(214 Ma),which constrained the early Mesozoic NE-SW crustal extension at the southeastern margin of the *** NE-SW extension probably originated from the postorogenic extensional collapse of the CAOB,subsequent exhumation being controlled by the far afield effects of the closure of the Mongol-Okhotsk belt.

关键词： strain simple shear pure shear kinematic vorticity ductile detachment zone

Geometry and kinematics of brittle deformation in the Central Cameroon shear Zone (Kékem area): Implication for gold exploration within the Central Africa Fold Belt in Cameroon

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China Geology 2021年第2期4卷 245-255页

作者： De Pesquidoux I Tchaptchet Tchato Jacqueline Tchakounte Aurélie Ngamy Kamwa Jean Pierre Tchouankoue Soumyajit Mukherjee Department of Earth Sciences Faculty of SciencesUniversity of YaoundéIYaoundéP.O.BOX:812Cameroon Department of Mining Engineering and Minerals processing Faculty of Mines and Pretrolum IndusriesUniversity of MarouaMaroua P.O.BOX:46Cameroon Geodynamics Laboratory Department of Earth SciencesIndian Institute of Technology BombayPowaiMumbai Maharashtra 410076India

The Central Africa Fold Belt(CAFB)is a collision belt endowed with gold deposits in Eastern Cameroon area mined for about 50 ***,favorable areas for gold exploration are poorly *** paper presents(1)the kinematics of the brittle deformation in the Kékem area in the SW portion of the Central Cameroon shear Zone and(2)constraints gold mineralization events with respect to the collisional evolution of the *** authors interpret that the conjugate ENE to E and NNW to NW trending lineament corresponds to the synthetic(R)and the antithetic(R’)shears,which accompanied the dextral slip along the NE to ENE striking *** latter coincides with the last 570-552 Ma D3 dextral simple shear-dominated transpression,which is parallel to the BétaréOya shear zone hosting gold *** mineralizations,which mainly occurred during the last dextral shearing,are disseminated within quartz veins associated to Riedel’s previous structures reactivated due to late collisional activities of the CAFB as brittle *** mineralizations occurred mainly during the 570-552 Ma D3 *** reactivation,which might be due to dextral simple shear during mylonitzation,plausibly remobilized the early gold deposits hosted in syn-compressional rocks and/or possibly focused deep-sourced fluid mixed with those released by ***,the Central Cameroon shear Zone where Kékem is located,and which shows similar petrographical and structural features to those controling Batouri gold district,is a target area for gold exploration in Cameroon.

关键词： Gold deposit Gold mineralization Gold exploration SRTM images Riedel fractures simple shear Congo Craton Kékem Central Africa fold belt Cameroon

Numerical modeling of extensional sedimentary basin formation with MATLAB:Application to the northern margin of the South China Sea

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Numerical modeling of extensional sedimentary basin formatio...