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International Journal of Mining Science and Technology 2023年第4期33卷 411-422页

作者： Zhi Zhao Yundong Shou Xiaoping Zhou School of Civil Engineering Wuhan UniversityWuhan 430072China National Center for International Research on Deep Earth Drilling and Resource Development Faculty of EngineeringChina University of Geosciences(Wuhan)Wuhan 430074China

Cracking behaviors of rocks significantly affect the safety and stability of the explorations of underground space and deep *** understand deeply the microscopic cracking process and mechanical property of rocks,X-ray micro-computed tomography(X-μCT)is applied to capture the rock *** digital color difference UNet(DCD-UNet)-based deep learning algorithm with 3D reconstruction is proposed to reconstruct the multiphase heterogeneity microstructure models of *** microscopic cracking and mechanical properties are studied based on the proposed microstructure-based peridynamic *** show that the DCD-UNet algorithm is more effective to recognize and to represent the microscopic multiphase heterogeneity of *** damage characteristic index of multiphase rocks increases,transgranular cracks in the same grain phase,transgranular and intergranular cracks of pore-grain phase,intergranular and secondary transgranular cracks and transgranular crack between different grains *** ultimate microscopic failure modes of rocks are mainly controlled by the transgranular cracks-based T1-shear,T3-shear,T1-tension,T2-tension and T3-tension failures,and the intergranular cracks-based T1-tension,T1-shear and T3-shear failures under uniaxial compression.

关键词： X-μCT imaging Deep learning Microscopic multiphase heterogeneity uniaxial compression Transgranular-intergranular cracks

Grain size reduction of copper subjected to repetitive uniaxial compression combined with accumulative fold

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Chinese Physics B 2009年第2期18卷 815-820页

作者：邹永涛雷力王赵王江华张伟贺端威 Institute of Atomic and Molecular Physics Sichuan University College of Physical Science and Technology Sichuan University

This paper reports a novel method of repetitive uniaxial compression combined with accumulative fold for preparing bulk submicron- to nanocrystalline copper starting with a coarse grained counterpart. Grain size reduction and microstrain variations of the high purity copper samples after different passes of compression and fold are investigated by scanning electron microscope and x-ray diffraction （XRD）, respectively. Our results show that the average grain size of samples decreases from about 830 nm to 127 nm as the number of compression passes increases to 30. Microstrain in the compressed sample is found to increase for the first 20 passes, but to decrease at the last 10 passes. The variations of compressive yield strength and the shift of XRD peaks to larger diffraction angles are observed in the squeezed sample. Our experimental results demonstrate that the repetitive uniaxial compression combined with accumulative fold is an effective method to prepare bulk nanocrystalline metallic materials, in particular for soft metals such as Cu, Al and Pb.

关键词： uniaxial compression accumulative fold grain size reduction bulk nanocrystalline materials

Orientation dependence of structural transition in fcc Al driven under uniaxial compression by atomistic simulations

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Chinese Physics B 2011年第4期20卷 391-396页

作者：李莉邵建立段素青梁九卿 Institute of Theoretical Physics and Department of Physics Shanxi University Institute of Applied Physics and Computational Mathematics

By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal A1 caused by uniaxial strain loading along the [001], [011] and [111] directions. We find that the structural transition is strongly dependent on the crystal orientations. The entire structure phase transition only occurs when loading along the [001] direction, and the increased amplitude of temperature for [001] loading is evidently lower than that for other orientations. The morphology evolutions of the structural transition for [011] and [111] loadings are analysed in detail. The results indicate that only 20% of atoms transit to the hcp phase for [011] and [111] loadings, and the appearance of the hcp phase is due to the partial dislocation moving forward on {lll}fcc family. For [011] loading, the hcp phase grows to form laminar morphology in four planes, which belong to the {111}fcc family; while for [111] loading, the hcp phase grows into a laminar structure in three planes, which belong to the {111}fcc family except for the （111） plane. In addition, the phase transition is evaluated by using the radial distribution functions.

关键词： single crystal Al molecular dynamics simulations uniaxial compression phase transition

Mechanical and microstructural response of densified silica glass under uniaxial compression: Atomistic simulations

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Chinese Physics B 2020年第10期29卷 507-514页

作者： Yi-Fan Xie Feng Feng Ying-Jun Li Zhi-Qiang Hu Jian-Li Shao Yong Mei School of Science China University of Mining and TechnologyBeijing 100083China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyBeijing 100083China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Institute of Defense Engineering AMSPLABeijing 100036China

We investigate the mechanical and microstructural changes of the densified silica glass under uniaxial loading-unloading via atomistic simulations with a modified BKS potential. The stress–strain relationship is found to include three respective stages: elastic, plastic and hardening regions. The bulk modulus increases with the initial densification and will undergo a rapid increase after complete densification. The yield pressure varies from 5 to 12 GPa for different densified samples. In addition, the Si–O–Si bond angle reduces during elastic deformation under compression, and 5-fold Si will increase linearly in the plastic deformation. In the hardening region, the peak splitting and the new peak are both found on the Si–Si and O–O pair radial distribution functions, where the 6-fold Si is increased. Instead, the lateral displacement of the atoms always varies linearly with strain, without evident periodic characteristic. As is expected, the samples are permanently densified after release from the plastic region, and the maximum density of recovered samples is about 2.64 g/cm^3, which contains 15 % 5-fold Si, and the Si–O–Si bond angle is less than the ordinary silica glass. All these findings are of great significance for understanding the deformation process of densified silica glass.

关键词： silica glass uniaxial compression densification atomistic simulation

Failure mechanism of full-size concrete filled steel circle and square tubes under uniaxial compression

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Science China(Technological Sciences) 2015年第10期58卷 1638-1647页

作者： CAI JingMing PAN JinLong SHAN QiFeng Key Laboratory of Concrete and Pre-stressed Concrete Structures of Ministry of Education Southeast University

In this paper, the failure mechanisms of full-size concrete filled steel tubes(CFST) under uniaxial compression were investigated with nonlinear finite element method. Existing experimental results were employed to verify the validity of the finite element models of CFST specimens. Then, the numerical analysis was further conducted to study the mechanical behaviors of full-size CFST columns with circular and square cross sections under uniaxial compression. The simulation results indicate that the distribution of the contact pressure between circular steel tube and core concrete is much more uniform than that between square steel tube and concrete, resulting in much higher confinement and more efficient interaction between steel tube and core concrete in circular CFST columns, as well as ultimate load capacity and ultimate displacement. Extensive parametric analysis was also conducted to examine the effect of various parameters on the uniaxial compression behaviors of circular and square CFST columns.

关键词： CFST uniaxial compression finite element analysis interaction mechanism

Strain field investigation of limestone specimen under uniaxial compression loads using particle image velocimetry

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Journal of Central South University 2011年第5期18卷 1619-1625页

作者：徐金明程昌宏陆海平 Department of Civil Engineering Shanghai University Hunan Zhongda Design Institute Company Limited Central South University

The particle image velocimetry (PIV) method was used to investigate the full-field displacements and strains of the limestone specimen under external loads from the video images captured during the laboratory *** original colorful video images and experimental data were obtained from the uniaxial compression test of a *** eliminate perspective errors and lens distortion,the camera was placed normal to the rock specimen *** converted into a readable format of frame images,these videos were transformed into the responding grayscale images,and the frame images were then *** full-field displacement field was obtained by using the PIV technique,and interpolated in the sub-pixel *** displacement was measured in the plane of the image and inferred from two consecutive *** local displacement vectors were calculated for small sub-windows of the images by means of *** video images were interrogated in a multi-pass way,starting off with 64×64 images,ending with 16×16 images after 6 iterations,and using 75% overlap of the *** order to remove spurious vectors,the displacements were filtered using four filters:signal-to-noise ratio filter,peak height filter,global filter and local *** cubic interpolation was utilized if the displacements without a number were *** full-field strain was then obtained using the local least square method from the discrete *** strain change with time at different locations was also *** is found that the normal strains are dependant on the locations and the crack *** 1.0 and 5.0 s prior to the specimen failure,normal strains increase rapidly at many locations,while a stable status appears at some *** the specimen is in a failure status,a large rotation occurs and it increases in the inverse *** strain concentration bands do not completely develop into the large cracks,and meso-cracks are n

关键词： rock materials limestone video image strain field uniaxial compression particle image velocimetry

Grain growth in AZ31 alloy after uniaxial compression

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Transactions of Nonferrous Metals Society of China 2010年第12期20卷 2215-2222页

作者： S.ABDESSAMEUD H.AZZEDDINE B.ALILI D.BRADAI Laboratoire Faculty of PhysicsUniversity of Sciences and Technology Houari Boumediene(USTHB)BP32El-Alia Bab EzzouarAlgiers 16111Algeria

The grain growth morphology,kinetics and texture change after uniaxial compression at 430 ℃ of an extruded AZ31 alloy were *** samples were loaded following two routes insuring two initial textures of the samples with compression direction parallel and normal to the extrusion *** both initial textures,a stable grain size is attained upon isothermal annealing and the grain growth kinetics can be described by:dn= dRn+kt with an n value of around *** annealing texture with grown grains is a retained hot deformation texture without emerging or strengthening other *** grain growth is not observed for annealing time up to 10 000 h at 450℃.

关键词： AZ31 magnesium alloy uniaxial compression annealing grain growth texture

Study on Acoustic Emission Characteristics of Self-Compacting Concrete under uniaxial compression Test

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Journal of Renewable Materials 2022年第8期10卷 2287-2302页

作者： Yongshuai Sun Guihe Wang Yixuan li College of Water Resources&Civil Engineering China Agricultural UniversityBeijing100083China School of Engineering and Technology China University of GeosciencesBeijing100083China

To study the relationship between acoustic emission characteristic parameters of self-compacting concrete(SCC)and its destruction evolution,under uniaxial compression,acoustic emission(AE)tests are performed on C30 selfcompacting concrete test blocks that are preserved for 7 days and 28 days,the corresponding relationship among energy,amplitude,ring count and different failure stages of the specimens are analyzed by AE experiment,and the spatial distribution of AE in each stage is described by introducing location *** test shows that there are two rules for the failure of SCC specimens cured for 7 days and 28 days:(1)The first failure law is divided into four stages according to the percentage of the stress value reaching the limit stress:Initial stage:above 10%,the compaction time of test block cured for 28 days is relatively low;Elastic failure stage:30%–35%,the cumulative value of each parameter increases linearly,and the cumulative value of the amplitude is the largest;Crack stable propagation stage:35%–90%,there is a moment that causes local stress concentration in both test blocks;Active stage:above 90%,the cumulative value of the parameter rises sharply,then continues to load the test block instability and damage.(2)The second failure law is divided into five stages according to the percentage of the stress value reaching the limit stress:Initial stage:15%–20%,the cumulative value of each parameter increases with time;Elastic failure stage:20%–40%,the cumulative value of the parameter continues to grow,but the growth curve is approximately parallel;Crack stable propagation stage:40%–60%,all parameters increased sharply and the increase reached the peak of the whole process;A stable state:60–80%,the emission characteristic parameter will become zero,and the stable state of the 28 days curing test block is lagging;Active stage:above 90%,the number of signals increased sharply,but the energy and amplitude are low,and the later test block is completely fractu

关键词： Acoustic emission change rule damage localization self-compacting concrete uniaxial compression

Extraction and identifcation of spectrum characteristics of coal and rock hydraulic fracturing and uniaxial compression signals

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International Journal of Coal Science & Technology 2023年第4期10卷 1-16页

作者： Ya′nan Qian Quangui Li Qianting Hu Zhizhong Jiang Ronghui Liu Jie Li Wenxi Li Changjun Yu State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China School of Resources and Safety Engineering Chongqing UniversityChongqing 400044China State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines(Anhui University of Science and Technology) Huainan 232001China Mining College of Guizhou University Guiyang 550025GuizhouChina China Coal Technology and Engineering Group Shenyang Research Institute Fushun 113122China

Microseismic(MS)events generated during coal and rock hydraulic fracturing(HF)include wet events caused by fracturing fuid injection,in addition to dry events caused by stress *** mixture of these two events makes efective fracturing MS events pickup *** study is based on physical experiments of diferent coal and rock HF and uniaxial *** diferences of waveform characteristic parameters of various coal and rock ruptures were analyzed using the Hilbert–Huang transform,leading to some useful *** phase characteristics of the acoustic emission(AE)energy difered signifcantly and responded well to the pumping pressure *** AE waveforms of HF exhibit similar energy and frequency distribution characteristics after Empirical mode *** main frequency bands for coal,sandstone,and shale samples are 100–300 kHz,while the mudstone sample is in the range of 50–150 *** decay ratios for coal,sandstone,shale and mudstone samples are 0.78,0.83,0.67 and 0.85,*** compared to the uniaxial compression test,the main frequency bands of HF were reduced for coal,sandstone and mudstone samples,whereas shale remained essentially *** duration,instantaneous energy,and total energy of the HF waveform are smaller than those of uniaxial compression,while the decay ratio is greater,especially for the mudstone *** waveform characteristic parameters,trained using the multilayer perceptron neural network,can efectively identify HF and uniaxial compression events with an accuracy of 96%.

关键词： Hydraulic fracturing uniaxial compression Hilbert-Huang transform Acoustic emission Microseismic

Unified analytical stressstrain curve for quasibrittle geomaterial in uniaxial tension, direct shear and uniaxial compression

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Journal of Central South University of Technology 2006年第1期13卷 99-104页

作者：王学滨 Department of Mechanics and Engineering Sciences Liaoning Technical University Fuxin 123000 China

Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stressstrain curves of quasibrittle geomaterial (such as rock and concrete) in uniaxial tension, direct shear and uniaxial compression were presented, respectively. The three derived stressstrain curves were generalized as a unified formula. Beyond the onset of strain localization, a linear strain-softening constitutive relation for localized band was assigned. The size of the band was controlled by internal or characteristic length according to gradient-dependent plasticity. Elastic strain within the entire specimen was assumed to be uniform and decreased with the increase of plastic strain in localized band. Total strain of the specimen was decomposed into elastic and plastic parts. Plastic strain of the specimen was the average value of plastic strains in localized band over the entire specimen. For different heights, the predicted softening branches of the relative stressstrain curves in uniaxial compression are consistent with the previously experimental results for normal concrete specimens. The present expressions for the post-peak stressdeformation curves in uniaxial tension and direct shear agree with the previously numerical results based on gradient-dependent plasticity.

关键词： stress- strain curve uniaxial tension uniaxial compression direct shear shear band rock concrete