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超高韧性水泥基复合材料的层裂试验研究 认领 被引量:4
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作者 李庆华 舒程岚青 徐世烺 《工程力学》 EI CSCD 北大核心 2020年第4期51-59,共9页
层裂是材料遭受冲击、爆炸等高速荷载时的一种常见破坏方式。该文利用直径80 mm的霍普金森杆实验装置,研究了超高韧性水泥基复合材料UHTCC(Ultra High Toughness Cementitious Composites)中应力波的传播特性和材料的层裂强度。通过在... 层裂是材料遭受冲击、爆炸等高速荷载时的一种常见破坏方式。该文利用直径80 mm的霍普金森杆实验装置,研究了超高韧性水泥基复合材料UHTCC(Ultra High Toughness Cementitious Composites)中应力波的传播特性和材料的层裂强度。通过在试件表面粘贴5组应变片,获得了在0.2 MPa、0.3 MPa、0.4 MPa、0.5 MPa打击气压下,UHTCC中应力波的传播曲线。利用高速摄影机记录层裂试验,观测了UHTCC的层裂破坏过程。由试件表面应变片测得的应力波曲线,计算了材料中的应力波波速、动态弹性模量,分析了应力波在该材料中传播的衰减规律,并计算出不同打击气压下材料的层裂强度及应变率。试验结果显示:UHTCC的层裂过程相比混凝土具有更多的韧性特征;UHTCC中的应力波峰值在0 mm~500 mm范围内衰减迅速;在同等应变率下,UHTCC与静态抗拉强度相近的混凝土相比,层裂强度高出10 MPa左右,且UHTCC的层裂强度具有明显的应变率敏感性。 展开更多
关键词 层裂 UHTCC 应力波 HOPKINSON 动态拉伸
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身管材料性能及射击过程多物理场载荷环境研究 认领
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作者 杨雕 刘朋科 +2 位作者 宁变芳 第五思杰 朱文芳 《火炮发射与控制学报》 北大核心 2020年第4期1-5,共5页
火炮射击过程中身管内膛多物理场载荷环境是研究身管寿命的前提。为准确获得射击过程身管内膛载荷环境,基于静态拉伸及Hopkinson压杆试验,研究身管材料在不同应变率及温度下力学性能参数的变化规律。以此为基础,建立射击过程内膛燃烧与... 火炮射击过程中身管内膛多物理场载荷环境是研究身管寿命的前提。为准确获得射击过程身管内膛载荷环境,基于静态拉伸及Hopkinson压杆试验,研究身管材料在不同应变率及温度下力学性能参数的变化规律。以此为基础,建立射击过程内膛燃烧与传热的数学模型及弹丸身管耦合非线性动力学模型,获得身管内膛温度及应力场。结果表明:身管材料性能随着温度的升高急剧下降,在800℃时屈服极限约100~200 MPa左右。在挤进过程中身管起始部的最高温度为1405.7K,应力幅值接近470 MPa,摩擦速度小于50 m/s.分析结果加深了对身管材料性能及射击过程内膛多物理场载荷环境的认识,可为身管寿命的研究提供载荷输入。 展开更多
关键词 身管 材料性能 Hopkinson 温度场 应力场
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Experimental and numerical study of failure behavior and mechanism of coal under dynamic compressive loads 认领
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作者 Junjun Feng Enyuan Wang +2 位作者 Qisong Huang Houcheng Ding Xiangyang Zhang 《矿业科学技术学报:英文版》 SCIE EI CSCD 2020年第5期613-621,共9页
A comprehensive understanding of the failure behavior and mechanism of coal is a prerequisite for dealing with dynamic problems in mining space.In this study,the failure behavior and mechanism of coal under uniaxial d... A comprehensive understanding of the failure behavior and mechanism of coal is a prerequisite for dealing with dynamic problems in mining space.In this study,the failure behavior and mechanism of coal under uniaxial dynamic compressive loads were experimentally and numerically investigated.The experiments were conducted using a split Hopkinson pressure bar(SHPB)system.The results indicated that the typical failure of coal is lateral and axial at lower loading rates and totally smashed at higher loading rates.The further fractography analysis of lateral and axial fracture fragments indicated that the coal failure under dynamic compressive load is caused by tensile brittle fracture.In addition,the typical failure modes of coal under dynamic load were numerically reproduced.The numerical results indicated that the axial fracture is caused directly by the incident compressive stress wave and the lateral fracture is caused by the tensile stress wave reflected from the interface between coal specimen and transmitted bar.Potential application was further conducted to interpret dynamic problems in underground coal mine and it manifested that the lateral and axial fractures of coal constitute the parallel cracks in the coal mass under roof fall and blasting in mining space. 展开更多
关键词 Split Hopkinson pressure bar Stress wave Failure mode Fracture mechanism FRACTOGRAPHY
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Dynamic Compression Behavior of Ultra-high Performance Cement-based Composite with Hybrid Steel Fiber Reinforcements 认领
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作者 戎志丹 WANG Yali WU Shenping 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2020年第5期900-907,共8页
Ultra-high performance cement-based composites (UHPCC) is promising in construction of concrete structures that suffer impact and explosive loads.In this study,a reference UHPCC mixture with no fiber reinforcement and... Ultra-high performance cement-based composites (UHPCC) is promising in construction of concrete structures that suffer impact and explosive loads.In this study,a reference UHPCC mixture with no fiber reinforcement and four mixtures with a single type of fiber reinforcement or hybrid fiber reinforcements of straight smooth and end hook type of steel fibers were prepared.Split Hopkinson pressure bar (SHPB) was performed to investigate the dynamic compression behavior of UHPCC and X-CT test and 3D reconstruction technology were used to indicate the failure process of UHPCC under impact loading.Results show that UHPCC with 1% straight smooth fiber and 2% end hook fiber reinforcements demonstrated the best static and dynamic mechanical properties.When the hybrid steel fiber reinforcements are added in the concrete,it may need more impact energy to break the matrix and to pull out the fiber reinforcements,thus,the mixture with hybrid steel fiber reinforcements demonstrates excellent dynamic compressive performance. 展开更多
关键词 ultra-high performance cement-based composite dynamic compression behavior hybrid fiber reinforcements split Hopkinson pressure bar
选区激光熔化Ti-6Al-4V合金在高应变速率下力学性能的有限元模拟 认领 被引量:1
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作者 李颖 王少辉 +3 位作者 张婷 刘传欣 伍海辉 柴象海 《机械工程材料》 CAS CSCD 北大核心 2020年第3期68-72,共5页
采用选区激光熔化(SLM)技术制备Ti-6Al-4V合金,经真空退火热处理和热等静压处理后,研究了合金准静态和高应变速率(500~3000s^-1)下的力学性能;对双线性材料模型进行标定,将所得到的材料参数应用于霍普金森压缩试验的有限元模拟中,并将... 采用选区激光熔化(SLM)技术制备Ti-6Al-4V合金,经真空退火热处理和热等静压处理后,研究了合金准静态和高应变速率(500~3000s^-1)下的力学性能;对双线性材料模型进行标定,将所得到的材料参数应用于霍普金森压缩试验的有限元模拟中,并将模拟结果与试验结果进行对比。结果表明:经真空退火和热等静压处理后,SLM成形合金的组织为α相和β相,呈网篮组织形貌;与准静态条件下的相比,在高应变速率下SLM成形合金的断后伸长率得到明显提高;模拟得到的归一化真应力-真应变曲线与试验得到的相吻合,平均相对误差为2.5%,其材料参数可用于后续的瞬态冲击仿真分析中。 展开更多
关键词 选区激光熔化 TI-6AL-4V合金 高应变速率 霍普金森杆 动态性能
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高应变率条件下38CrMoAl钢的动态力学行为及失效模型 认领
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作者 陈跃良 张柱柱 +2 位作者 卞贵学 张勇 黄海亮 《航空学报》 EI CAS CSCD 北大核心 2020年第10期404-414,共11页
38CrMoAl钢是飞机某频繁经受冲击载荷结构的主要材料,为了获得该钢在冲击载荷下的力学行为和失效参数,本文对38CrMoAl钢开展了准静态试验、应变率从650s-1至5500s-1的动态力学试验以及应力三轴度试验,对材料的金相组织和断口形貌进行了... 38CrMoAl钢是飞机某频繁经受冲击载荷结构的主要材料,为了获得该钢在冲击载荷下的力学行为和失效参数,本文对38CrMoAl钢开展了准静态试验、应变率从650s-1至5500s-1的动态力学试验以及应力三轴度试验,对材料的金相组织和断口形貌进行了微观观察分析,最后基于试验结果确定了材料的修正强度模型和失效模型参数。试验结果表明,38CrMoAl钢具有较强的应变率敏感性,材料屈服强度随着应变率的增加具有正应变率强化效应,应变率在10-3~5500s-1的范围变化时,屈服应力从450MPa上升到了1085MPa,应变率为5500s-1时材料的屈服应力达到了准静态条件下的2.41倍。对材料组织的微观观察分析发现材料主要由呈现颗粒状的回火索氏体组成,材料在高应变速率加载下其塑性发生了下降,断口由韧窝型塑性断口向局部解理断面发生转变,韧窝尺寸也随着应变率的升高而变小。对Johnson-Cook(J-C)强度模型中的应变率强化项进行了修正,使修正后的本构模型可以更有效地描述38CrMoAl钢的动态力学行为,最后结合数值模拟方法确定了材料的J-C失效准则参数。 展开更多
关键词 38CrMoAl 动态力学性能 高应变率 霍普金森杆 修正J-C本构 失效参数
Microstructural softening induced adiabatic shear banding in Ti-23Nb-0.7Ta-2Zr-O gum metal 认领
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作者 Silu Liu Y.Z.Guo +5 位作者 Z.L.Pan X.Z.Liao E.J.Lavernia Y.T.Zhu Q,M,Wei Yonghao Zhao 《材料科学技术:英文版》 SCIE EI CAS CSCD 2020年第19期31-39,共9页
Ti-23Nb-0.7Ta-2Zr-O gum metal(GM)is an attractive candidate material for applications that require superior mechanical properties.In our earlier investigation of the GM[1],geometrical softening and the generation of a... Ti-23Nb-0.7Ta-2Zr-O gum metal(GM)is an attractive candidate material for applications that require superior mechanical properties.In our earlier investigation of the GM[1],geometrical softening and the generation of adiabatic shear bands(ASBs)were proposed as primary reasons for the documented anisotropic impact response.In the present study,electron backscattered diffraction(EBSD)analysis reveals two different deformed microstructures,i.e.,deformed ultrafine grains(UFGs)and dynamically recrystallized UFGs,formed in the ASBs of GM samples processed by extrusion equal channel angular pressing(ECAP),respectively.Additional calculation of temperature rise during dynamic compression suggests that the above microstructure differences in the ASBs was originated from their different maximum ASB temperatures(608 K for extruded GM and 1159 K for ECAP-processed GM).Moreover,our calculation on the temperature at the onset of ASBs indicates that microstructural softening is the primary cause for the development of ASBs in both extruded GM(321 K)and ECAP-processed GM(331 K). 展开更多
关键词 Gum metal Split hopkinson bar Adiabatic shear band MICROSTRUCTURES
Experimental methods for determination of mechanical behaviors of materials at high temperatures via the split Hopkinson bars 认领
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作者 Q.B.Dou K.R.Wu +5 位作者 T.Suo C.Zhang X.Guo Y.Z.Guo W.G.Guo Y.L.Li 《力学学报:英文版》 SCIE EI CAS CSCD 2020年第6期1275-1293,I0003,共20页
Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure d... Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety assessment.Great efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar systems.The principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature testing.Techniques such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as possible.Moreover,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also proposed.The technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as well.The paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenges for future research. 展开更多
关键词 Mechanical behaviors Split Hopkinson bar High strain rate High temperature
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Dynamic experiment and numerical simulation of frozen soil under confining pressure 认领
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作者 W.R.Tang Z.W.Zhu +2 位作者 T.T.Fu Z.W.Zhou Z.H.Shanggua 《力学学报:英文版》 SCIE EI CAS CSCD 2020年第6期1302-1318,I0004,共18页
With the development of cold region engineering,it is crucial to study the mechanical properties of frozen soil.In practice,frozen soil is inevitably subject to impact loading,making the study of frozen soil under imp... With the development of cold region engineering,it is crucial to study the mechanical properties of frozen soil.In practice,frozen soil is inevitably subject to impact loading,making the study of frozen soil under impact loading necessary for engineering in cold regions.The split–Hopkinson pressure bar(SHPB)is an important experimental means for obtaining the dynamic performance of materials.In this study,an SHPB experiment was conducted on frozen soil under confining pressure.The frozen soil exhibited an evident strain rate effect and temperature effect under confining pressure.The SHPB experiment on frozen soil under confining pressure was simulated numerically using LS-DYNA software and the Holmquist–Johnson–Cook(HJC)material model.A loading simulation with passive confining pressure and active confining pressure was completed by adding an aluminum sleeve and applying a constant load.The simulation results obtained using the above methods were in good agreement with the experimental results.The strength of the frozen soil under confining pressure was greater than that of the uniaxial impact,and there was an evident confining pressure effect.Furthermore,the confining pressure provided by passive confinement was larger than that provided by active confinement.The passive confining pressure energy absorption efficiency was higher than for the active confining pressure due to the need to absorb more energy under the same damage conditions.The frozen soil exhibited viscoplastic failure characteristics under confining pressure. 展开更多
关键词 Frozen soil-Dynamic experiment Confining pressure Split-Hopkinson pressure bar Numerical simulation
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Dynamic compression characteristics of layered rock mass of significant strength changes in adjacent layers 认领
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作者 Sen Wen Chunshun Zhang +1 位作者 Yulin Chang Ping Hu 《岩石力学与岩土工程学报:英文版》 SCIE CSCD 2020年第2期353-365,共13页
Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation,and dynamic loading is a prevalent scenario generated during excavation.In order to improve the dr... Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation,and dynamic loading is a prevalent scenario generated during excavation.In order to improve the driving efficiency and reduce engineering accidents,dynamic compression characteristics of this kind of rock mass should be understood.The dynamic properties of a layered composite rock mass are investigated through a series of rock tests and numerical simulations.The rock mass is artificially made of various proportions of sand,cement and water to control the distinct strength variations at various composite layers separated by parallel bedding planes.All rock specimens are prefabricated in a specially designed mould and then cut into 50 mm in diameter and 50 mm in height for split Hopkinson pressure bar(SHPB)dynamic compression testing.The test results reveal that increasing strain rate causes the increases of peak strength,σ_p,and the corresponding failure strain,ε_p,while the dynamic elastic modulus,E_d,remains almost unchanged.Interestingly,under the same strain rates,Ed of the composite rock specimen is found to decline first and then increase as the dip angle of bedding plane increases.The obtained rock failure patterns due to various dip angles lead to failure modes that could be classified into four categories from our dynamic tests.Also,a series of counterpart numerical simulations has been undertaken,showing that dynamic responses are in good agreement with those obtained from the SHPB tests.The numerical analysis enables us to Iook into the dynamic characteristics of the composite rock mass subjected to a broader range of strain rates and dip angles than these being tested. 展开更多
关键词 ROCK dynamics Split hopkinson pressure bar(SHPB) Layered composite ROCK specimen DIP angle of BEDDING plane Strain rate Numerical simulation
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高瞬态冲击下陶瓷电容损伤过程中的参数漂移特性 认领
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作者 程向群 李晓峰 +2 位作者 王亚斌 富玉 王钢 《兵工学报》 EI CAS CSCD 北大核心 2020年第S02期234-240,共7页
触发引信随弹体碰击和侵彻目标过程中经历的大瞬态高过载可能导致电容承受的应力急剧增加,严重情况将造成结构损伤,应力的瞬变带来电容参数的漂移,进而影响到与电容相关的电路单元。针对高瞬态冲击环境下带电电容参数漂移问题,基于高速... 触发引信随弹体碰击和侵彻目标过程中经历的大瞬态高过载可能导致电容承受的应力急剧增加,严重情况将造成结构损伤,应力的瞬变带来电容参数的漂移,进而影响到与电容相关的电路单元。针对高瞬态冲击环境下带电电容参数漂移问题,基于高速充放电原理提出一种高重复频率的电容参数测试方法。利用分离式霍普金森杆试验装置作为加载途径,设计高瞬态加载过程中测试电容参数漂移的系统,进行多组高动态加载试验,峰值过载由1.8×10^(4) g提高至16.8×10^(4) g.观测到未开裂电容和开裂电容在冲击过程中的充放电现象,通过数据分析获得电容应变、冲击过载和电学参数变化历程。数据曲线显示:在应力波首次通过电容时,电容容值减小,容值减小幅度因冲击强度而有所区别;该参数漂移现象可能导致带电电容极板的电压升高。 展开更多
关键词 多层陶瓷电容 高瞬态冲击 参数漂移 电容容值测试 霍普金森杆
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Long-term mechanical behavior and characteristics of cemented tailings backfill through impact loading 认领 被引量:1
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作者 Yu-ye Tan Elmo Davide +2 位作者 Yu-cheng Zhou Wei-dong Song Xiang Meng 《矿物冶金与材料学报:英文版》 SCIE EI CAS CSCD 2020年第2期140-151,共12页
Cemented tailings backfill(CTB)structures are important components of underground mine stopes.It is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to di... Cemented tailings backfill(CTB)structures are important components of underground mine stopes.It is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to disturbance by dynamic loading,such as excavation and blasting.In this study,the authors present the results of a series of Split-Hopkinson pressure bar(SHPB)single and cyclic impact loading tests on CTB specimens to investigate the long-term dynamic mechanical properties of CTB.The stress-strain relationship,dynamic strength,and dynamic failure characteristics of CTB specimens are analyzed and discussed to provide valuable conclusions that will improve our knowledge of CTB long-term mechanical behavior and characteristics.For instance,the dynamic peak stress under cyclic impact loading is approximately twice that under single impact loading,and the CTB specimens are less prone to fracture when cyclically loaded.These findings and conclusions can provide a new set of references for the stability analysis of CTB materials and help guide mine designers in reducing the amount of binding agents and the associated mining cost. 展开更多
关键词 cyclic impact loading CEMENTED TAILINGS BACKFILL DYNAMIC mechanical properties Split-Hopkinson pressure bar DYNAMIC PEAK
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Relation between Loading Rate and Fracture Velocity on Limestone 认领
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作者 Ajay Kumar Jha 《地质资源与工程:英文版》 2020年第4期114-120,共7页
The relation between loading rate and fracture velocity is the key to determining the fracture toughness of rock mass under dynamic loading.While designing an optimal blast design for any limestone mines,understanding... The relation between loading rate and fracture velocity is the key to determining the fracture toughness of rock mass under dynamic loading.While designing an optimal blast design for any limestone mines,understanding the relationship between blast detonation pressure and rock fragmentation can increase the energy utilisation in any limestone mine blast.The detonation pressure is directly related to dynamic loading rate and fracture velocity is directly related to stress wave propagation speed during blasting.This paper discusses the relationship between dynamic loading rate and fracture velocity for limestone samples.It was observed that crack propagation velocity increases with fracture toughness of rock samples.It may be concluded that as the dynamic loading increases,the fracture velocity increases. 展开更多
关键词 Fracture velocity split Hopkinson pressure bar(SHPB) loading rate
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双剪切爆破阀机械组件可靠性研究 认领
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作者 张拙 顾剑峰 +3 位作者 刘强 詹乐昌 马静娴 宿希慧 《机电产品开发与创新》 2020年第6期99-102,共4页
对爆破阀剪切盖材料在常温、155℃和350℃三种温度下进行了不同应变率的拉伸试验。试验结果表明,材料应变率与抗拉极限是正相关的,温度与抗拉极限是负相关的,温度与材料断后延伸率的相关性很低,抗拉强度和断后延伸率在不同的应变率下呈... 对爆破阀剪切盖材料在常温、155℃和350℃三种温度下进行了不同应变率的拉伸试验。试验结果表明,材料应变率与抗拉极限是正相关的,温度与抗拉极限是负相关的,温度与材料断后延伸率的相关性很低,抗拉强度和断后延伸率在不同的应变率下呈正态分布。采用ABAQUS+NESSUS联合仿真计算得到爆破阀机械组件的可靠度,计算结果表明,对爆破阀机械可靠性影响最大的是剪切盖材料力学性能,爆破阀机械可靠性与活塞冲击速度呈正相关。 展开更多
关键词 爆破阀 可靠性 镍基合金 霍普金森杆 ABAQUS NESSUS
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Dynamic response characteristics of dry and watersaturated schist under impact loading 认领
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作者 ZHOU Yang SU Sheng-rui CHEN Jian-xun 《山地科学学报:英文版》 SCIE CSCD 2020年第12期3123-3136,共14页
Many geological engineering hazards are closely related to the dynamic mechanical properties of rock materials.However,most existing studies on the dynamic mechanical properties of rock materials were conducted on the... Many geological engineering hazards are closely related to the dynamic mechanical properties of rock materials.However,most existing studies on the dynamic mechanical properties of rock materials were conducted on the hard rocks such as sandstone,granite,limestone,and marble,whereas soft rocks,such as schist,are less studied.Therefore,in this study,a series of triaxial impact tests were conducted on dry and saturated schist by employing a modified triaxial split Hopkinson pressure bar system to reveal the coupling effects of water,strain rate,and triaxial confining pressure on the mechanical properties of schist.The results show that schist is a type of watersensitive rock and the stress-strain curve of saturated schist has apparent ductility.The effects of strain rate on dynamic strain,deformation modulus and peak stress were analyzed.The results also show that the dynamic peak stress is affected by the combined softening effect and viscous effect of water under impact loading.Finally,it was found that the failure mode of schist belongs to typical axial tensile failure under uniaxial impact tests,and shear failure is the main failure mode under triaxial impact tests.With the increase in confining pressure,the failure modes of schist change from tensile failure to shear failure.This research can provide useful parameters for geological engineering hazard prevention in mountain areas. 展开更多
关键词 Dry and water-saturated schist Triaxial stress constraint Modified triaxial split Hopkinson pressure bar Dynamic mechanical behavior Impact loading
Effects of Craddition on Charpy impact energy in austenitic 0.45C-24Mn-(0,3,6)Cr steels 认领
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作者 Seok Gyu Lee Bohee Kim +6 位作者 Min Cheol Jo Kyeong-Min Kim Junghoon Lee Jinho Bae Byeong-Joo Lee Seok Su Sohn Sunghak Lee 《材料科学技术:英文版》 SCIE EI CAS CSCD 2020年第15期21-30,共10页
Effects of Cr addition(0,3,and 6 wt%) on Charpy impact properties of Fe-C-Mn-Cr-based steels were studied by conducting dynamic compression tests at room and cryogenic temperatures.At room temperature,deformation mech... Effects of Cr addition(0,3,and 6 wt%) on Charpy impact properties of Fe-C-Mn-Cr-based steels were studied by conducting dynamic compression tests at room and cryogenic temperatures.At room temperature,deformation mechanisms of Charpy impacted specimens were observed as twinning induced plasticity(TWIP) without any transfo rmation induced plasticity(TRIP) in all the steels.At cryogenic temperature,many twins were populated in the Cr-added steels,but,interestingly,fine ε-martensite was found in the OCr steel,satisfying the Shoji-Nishiyama(S-N) orientation relationship,{111}γ//{0002}ε and <101>γ//<1120>ε.Even though the cryogenic-temperature staking fault energies(SFEs) of the three steel were situated in the TWIP regime,the martensitic transformation was induced by Mn-and Cr-segregated bands.In the OCr steel,SFEs of low-(Mn,Cr) bands lay between the TWIP and TRIP regimes which were sensitively affected by a small change of SFE.The dynamic compressive test results well showed the relation between segregation bands and the SFEs.Effects of Cr were known as not only increasing the SFE but also promoting the carbide precipitation.In order to identify the possibility of carbide formation,a precipitation kinetics simulation was conducted,and the predicted fractions of precipitated M23C6 were negligible,0.4-1.1×10-5,even at the low cooling rate of 10℃/s. 展开更多
关键词 Austenitic high-Mn steels Charpy impact energy Split Hopkinson pressure bar Twinning induced plasticity(TWIP) Transformation induced plasticity(TRIP) Stacking fault energy(SFE)
SHPB系统在岩体力学实验教学的应用和课程改革探索 认领
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作者 王述红 张晓德 +2 位作者 陈猛 王斐笠 蔡运生 《实验技术与管理》 CAS 北大核心 2020年第2期182-185,共4页
冲击荷载下岩体的动态力学强度劣化构成了岩爆、滑坡、落石等众多地质灾害发生的成因,借助霍普金森杆(SHPB)进行岩体动态力学特性的实验教学是土木工程学科教学必不可少的环节。文章对霍普金森杆的装置构造、实验原理、实验过程进行了叙... 冲击荷载下岩体的动态力学强度劣化构成了岩爆、滑坡、落石等众多地质灾害发生的成因,借助霍普金森杆(SHPB)进行岩体动态力学特性的实验教学是土木工程学科教学必不可少的环节。文章对霍普金森杆的装置构造、实验原理、实验过程进行了叙述,指出目前实验教学中存在的问题,并提出调动学生上课积极性、促进和增强其实验参与性、理论的实践应用性及思维创新性等课程改革思路。 展开更多
关键词 岩体力学 动载荷 霍普金森杆 实验教学 课程改革
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Further numerical investigation on concrete dynamic behaviors with considering stress non-equilibrium in SHPB test based on the waveform features 认领
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作者 T.H.Lv X.W.Chen +1 位作者 Y.J.Deng G.Chen 《力学学报:英文版》 SCIE EI CAS CSCD 2020年第4期873-886,共14页
In this study,with the meso-scale model reliably validated in our previous work(Construction and Building Materials,2018),the waveform features of plain concrete under various loading conditions and especially with co... In this study,with the meso-scale model reliably validated in our previous work(Construction and Building Materials,2018),the waveform features of plain concrete under various loading conditions and especially with considering stress non-equilibrium are reliably reproduced and predicted.Associating with waveform features,the violation indicator of the specimen stress equilibrium in the split Hopkinson pressure bar test is identified for concrete-like damage softening materi-als.The concrete material behaviors for stress non-equilibrium are further analyzed,e.g.the dynamic increase factor(DIF)and damage development,etc.The conception of“damage failure volume”is introduced,and a new method of defining the development of concrete dynamic damage is given in the nimierical study.What’s more,the“compression wave”and“double peak”phenomena observed in the experiment are further interpreted based on the means of numerical simulation.Waveform features how to reflect the concrete material properties is also concluded.The results show that,the disappearance of the“double peak” phenomenon of reflection curve under high strain rate can be regarded as the indicator of the violation of stress equilibrium.After the violation of the stress equilibrium,the relevant DIFs of the concrete specimen will not change significantly.Especially,the concrete specimen will turn into structural response from material response.The conception of“damage failure volume”can well explain the generation of the“double peak”phenomenon of the reflection curve.The “compression wave” phenomenon of reflection curve under lower strain rates is derived from the unloading expansion recovery of the concrete specimen.Furthermore,under the same loading condition,the amplitude of the first peak of the reflection curve can be used as the evaluation standard of the bonding quality between mortar and aggregates. 展开更多
关键词 Concrete material Split Hopkinson pressure bar test Numerical investigation Waveform feature Stress non-equilibrium Damage failure volume
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基于Hopkinson杆的加速度传感器测试系统仿真与测试研究 认领
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作者 刘波 程祥利 +3 位作者 杨荷 叶海福 焦敏 韩萌萌 《实验力学》 CSCD 北大核心 2019年第6期1027-1034,共8页
针对加速度传感器的Hopkinson杆动态试验装置.采用有限元工具对Hopkinson杆测试系统进行了仿真研究。仿真结果说明整形垫的加入和入射子弹形状的改变提高了应力历史的上升时间和加速度历史的脉宽。动态加载的试验测试与仿真结果表明:当... 针对加速度传感器的Hopkinson杆动态试验装置.采用有限元工具对Hopkinson杆测试系统进行了仿真研究。仿真结果说明整形垫的加入和入射子弹形状的改变提高了应力历史的上升时间和加速度历史的脉宽。动态加载的试验测试与仿真结果表明:当由平头子弹改为尖头子弹并添加铝制整形垫后,入射杆应力脉冲持续时间与对加速度传感器加载的加速度冲击均得到了大幅提升。Hopkinson杆动态测试系统的测试与仿真研究为传感器的冲击试验设计奠定了基础。 展开更多
关键词 HOPKINSON 加速度传感器 动态加载 整形垫 子弹形状
单轴压缩下U75V钢动态力学行为及其修正J-C本构模型 认领 被引量:2
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作者 汪振兴 田晓耕 +1 位作者 干聪 魏兵辉 《材料热处理学报》 EI CAS CSCD 北大核心 2019年第7期156-164,共9页
采用材料试验机(MTS-880/25T)和温度控制的霍普金森压杆装置研究了U75V钢在25~700℃和0.0003~8000 s-1应变率下的力学行为进行了单轴压缩实验研究,获得了U75V钢在高温、高应变率动态压缩条件下的应力-应变曲线。利用Johnson-Cook模型对U... 采用材料试验机(MTS-880/25T)和温度控制的霍普金森压杆装置研究了U75V钢在25~700℃和0.0003~8000 s-1应变率下的力学行为进行了单轴压缩实验研究,获得了U75V钢在高温、高应变率动态压缩条件下的应力-应变曲线。利用Johnson-Cook模型对U75V钢动态塑性本构进行拟合,获得了其本构模型参数,发现U75V钢在500~700℃温度范围具有动态应变时效现象。对在2500 s-1应变率及不同温度下霍普金森杆撞击实验的试样组织进行观察,并对其发生动态应变时效的原因进行了分析和讨论。通过引入动态应变时效临界温度Tc和强化系数λ,对经典J-C模型进行了修正。结果表明,修正后的J-C模型参数可以在25~700℃和2500~8000 s-1应变率范围内准确描述U75V钢的动态力学行为。 展开更多
关键词 U75V钢 霍普金森杆 Johnson-Cook本构模型 动态应变时效 修正Johnson-Cook模型
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