检索结果-南通市图书馆

Constitutive modelling of concrete material subjected to low-velocity projectile impact:insights into damage mechanism and target resistance

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第2期25卷 161-182页

作者： Shen LIU Xieping HUANG Xiangzhen KONG Qin FANG Center for Hypergravity Experiment and Interdisciplinary Research Zhejiang UniversityHangzhou310058China Institute of Geotechnical Engineering Zhejiang UniversityHangzhou310058China State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact Army Engineering University of PLANanjing210007China

This paper presents a numerical study to improve the understanding of the complex subject of penetration and perforation of concrete targets impacted by low-velocity projectiles.The main focus is on the damage mechanisms and the major factors that account for the target resistance of the concrete.An improved continuous surface cap model recently proposed was employed.The model was first equipped with element erosion criteria and was adequately validated by comparisons with ballistic experiments.Comprehensive numerical simulations were carried out where the individual influence of tensile,shear,and volumetric behaviors(pore collapse)of a concrete target on its ballistic performance was investigated.Results demonstrated that cratering on the front face and scabbing on the rear face of the concrete target were mainly dominated by its tensile behavior.The major target resistance came from the second tunneling stage which was primarily governed by the shear and volumetric behaviors of the concrete.Particularly,this study captured the pore collapse-induced damage phenomenon during the high-pressure tunneling stage,which has been extensively reported in experiments but has usually been neglected in previous numerical investigations.

关键词： Penetration Perforation damage mechanism Target resistance Projectile impact Pore collapse

Impact wear properties of dissimilar joints between bainitic frogs and pearlite rails

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2024年第1期31卷 275-287页

作者： Pin-yong Zeng Chun-guang Zuo Xiao-yu Zhang Wei Li Tribology Research Institute Southwest Jiaotong UniversityChengdu610031SichuanChina

The impact wear behavior and damage mechanism of dissimilar welded joints between U26Mn frog and U75 V rail before and after normalizing treatment were studied by cyclic impact tests.The experiment indicated that the impact wear volume of the joints increased with the increasing number of impact cycles.The main wear mechanisms include pitting wear,mild fatigue wear,delamination wear,and fatigue wear,and plastic deformation was the primary impact wear mechanism.Among them,fatigue wear had the greatest influence on wear volume,while other wear mechanisms had limited effect.The impact wear resistance of the base material was better than that of the heat-affected zone.Normalizing treatment was beneficial to improving the impact wear resistance of welded joints owing to its effect to promote pearlite recovery,grain refinement,and uniform distribution of grains.The martensite generated in the rail welded joints aggravated the impact wear damage to the materials,which should be avoided.

关键词： Dissimilar welded joint Impact wear Bainitic steel damage mechanism Wear rate

Mechanical properties and energy evolution of Beishan shallow-layer granite under different unloading paths

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2024年第5期21卷 1728-1744页

作者： WANG Chuanle LI Erbing ZHANG Dengke HAN Yang LU Hui HE Kang DU Guangyin School of Transportation Southeast UniversityNanjing 211189China College of Defense Engineering Army Engineering University of PLANanjing 210007China Nanjing Urban Construction Management Group Co. Ltd.Nanjing 210006China College of Field Engineering Army Engineering University of PLANanjing 210007China

Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ.

关键词： Beishan granite Unloading test Mechanical properties damage mechanism Acoustic emission Strain energy

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

在线全文

学校读者我要写书评

暂无评论

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

damage mechanism and evaluation model of compressor impeller remanufacturing blanks:A review

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2019年第4期14卷 402-411页

作者： Haiyang LU Yanle LI Fangyi LI Xingyi ZHANG Chuanwei ZHANG Jiyu DU Zhen LI Xueju RAN Jianfeng LI Weiqiang WANG School of Mechanical Engineering Shandong UniversityJinan 250061China National Demonstration Center for Experimental Mechanical Engineering Education Shandong UniversityJinan 250061China Key Laboratory of High Efficiency and Clean Mechanical Manufacture Ministry of EducationShandong UniversityJinan 250061China Engineering Training Center Shandong UniversityJinan 250002China

The theoretical and technological achievements in the damage mechanism and evaluation model obtained through the national basic research program“Key Fundamental Scientific Problems on Mechanical Equipment Remanufacturing”are reviewed in this work.Large centrifugal compressor impeller blanks were used as the study object.The materials of the blanks were FV520B and KMN.The mechanism and evaluation model of ultra-high cycle fatigue,erosion wear,and corrosion damage were studied via theoretical calculation,finite element simulation,and experimentation.For ultra-high cycle fatigue damage,the characteristics of ultra-high cycle fatigue of the impeller material were clarified,and prediction models of ultra-high cycle fatigue strength were established.A residual life evaluation technique based on the“b-HV-N”(where b was the nonlinear parameter,HV was the Vickers hardness,and N was the fatigue life)double criterion method was proposed.For erosion wear,the flow field of gas-solid two-phase flow inside the impeller was simulated,and the erosion wear law was clarified.Two models for erosion rate and erosion depth calculation were established.For corrosion damage,the electrochemical and stress corrosion behaviors of the impeller material and welded joints in H2S/CO2 environment were investigated.KISCC(critical stress intensity factor)and da/dt(crack growth rate,where a is the total crack length and t is time)varied with H2S concentration and temperature,and their variation laws were revealed.Through this research,the key scientific problems of the damage behavior and mechanism of remanufacturing objects in the multi-strength field and cross-scale were solved.The findings provide theoretical and evaluation model support for the analysis and evaluation of large centrifugal compressor impellers before remanufacturing.

关键词： remanufacturing centrifugal compressor impeller remanufacturing blank damage mechanism evaluation model

Thermal stress damage mechanism in single-crystal germanium caused by 1080 nm laser irradiation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国物理B:英文版 2023年第10期32卷 572-578页

作者：沙银川李泽文贾志超韩冰倪晓武 School of Science Nanjing University of Science and TechnologyNanjing 210094China School of Materials Engineering Jinling Institute of TechnologyNanjing 211169China School of Electronic Engineering and Optical Engineering Nanjing University of Science and TechnologyNanjing 210094China

The process of thermal stress damage during 1080 nm laser ablation of single-crystal germanium was recorded in real time using a high-speed charge-coupled device.A three-dimensional finite element numerical model based on Fourier's heat conduction equation,Hooke's law and the Alexander–Hasson equation was developed to analyze the thermal stress damage mechanism involved.The damage morphology of the ablated samples was observed using an optical microscope.The results show that the cooling process has an important influence on fracture in the laser-irradiated region of single-crystal germanium.Fracture is the result of a combination of thermal stress and reduction in local yield strength.

关键词： thermal stress single-crystal germanium fracture damage mechanism

Microscopic damage mechanism of SA508 Gr3 steel in ultra-high temperature creep

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2018年第4期25卷 453-459页

作者： Zhi-gang Xie Yan-ming He Jian-guo Yang Xiang-qing Li Chuan-yang Lu Zeng-liang Gao Institute of Process Equipment and Control Engineering Zhejiang University of Technology Hangzhou 310014 Zhejiang China Mechanical and Electrical Department Shantou Polytechnic College Shantou 515078 Guangdong China

The lower head of reactor pressure vessel （RPV） will endure a great temperature gradient above the phase transition temperature, and the creep and fracture will be the primary failure mode for the RPV material in such a situation. The interrupted creep tests were performed on a typical RPV material, SA508 Gr3 steel, at 800 ℃. The microstructure of different creep stages was examined by scanning electron microscopy and transmission electron microscopy. The results showed that the microscopic damage is mainly induced by creep cavities and coarse second-phase particles. Furthermore, the volume fractions of creep cavities and coarse second-phase particles show a linear relationship with the extended creep time. The second-phase particles are determined to be MoC in the second creep stage and Mo2C in the third creep stage, according to the results of selected-area electron diffraction pattern. Combined with energy-dispersive spectrum analysis, the segregation of precipitates caused by the migration of atoms is finally unveiled, which leads to the coarsening of the particles.

关键词： Reactor pressure vessel SA508 Gr3 steel In-vessel retention. Second-phase particle damage mechanism Ultra-high temperature creep

damage and fracture mechanism of 6063 aluminum alloy under three kinds of stress states

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2008年第1期27卷 64-69页

作者： ZHU Hao ZHU Liang CHEN Jianhong Key Laboratory of the Ministry of Education of China for Nonferrous Metal Alloys Lanzhou University of Technology Lanzhou 730050 China

To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.

关键词： 6063 aluminum alloy damage mechanism fracture mechanism G-T-N model Johnson-Cook model

Study on Carbonation damage Constitutive Curve and Microscopic damage mechanism of Tailing Recycled Concrete

在线全文

学校读者我要写书评

暂无评论

Journal of Renewable Materials 2021年第8期9卷 1413-1432页

作者： Tao Li Sheliang Wang Fan Xu Binbin Li Bin Dang Meng Zhan Zhiqi Wang College of Urban Rural Planning and Architectural EngineeringShangluo UniversityShangluo726000China School of Civil Engineering Xi’an University of Architecture and TechnologyXi’an710055China Key Laboratory of Structure Engineering and Earthquake Resistance Ministry of Education(XAUAT)Xi’an University of Architecture and TechnologyXi’an710055China College of Architecture Engineering Huanghuai UniversityZhumadian463000China China Construction Third Engineering Bureau Green Industry Investment Co. Ltd.Wuhan430070China

To improve the resource utilization of recycled aggregate concrete(RAC)and make use of the unique pozzolanic activation characteristics of iron ore tailing(IOT),the constitutive curves of tailing recycled concrete(TRC)before and after carbonization were analyzed theoretically,experimentally and microscopically.Firstly,according to the experimental data,the damage constitutive and related damage parameters of TRC were theoretically established by Weibull probability distribution function.Secondly,the comprehensive damage parameter b under different working conditions was studied.Finally,the damage mechanism was formed by EDS and SEM.The results showed that the damage constitutive model based on Weibull probability distribution function was in good agreement with the experimental results.Under each carbonization period,the b first decreased and then rose with the increase of tailings content.When its content was 30%,the b values of TRC were minimized,which were 22.14%,20.99%,25.39%lower than those of NAC,and 41.09%,34.89%,35.44%lower than those of RAC,indicating that IOT had a relatively good optimization effect on the constitutive curve of RAC.The microscopic analysis results also proved that the IOT addition with a proper amount would improve the matrix structure of RAC and increased its compactness,but when the content was higher,it would also cause harmful cracks in its matrix structure and reduced its density.Therefore,the optimal tailing content was about 30%.This paper provided a new method for damage constitutive calculation and analysis of TRC before and after carbonization.

关键词： Tailings recycled concrete carbonation damage constitution damage mechanism