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Comparison of Acoustic Emission Characteristics for C/SiC Composite Component Under Combination of Heating and Mechanical Loading
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作者 Zhi-Yong Tan Chang-Wan Min +2 位作者 Hong-Wei Wu Yu-Hai Qian Mei-Shuan Li 《金属学报:英文版》 SCIE EI CAS CSCD 2017年第10期992-998,共7页
The acoustic emission(AE) characteristics of C/SiC composite component under various conditions were compared, with the purpose of identifying the possible damage and failure mechanism. During the process of the singl... The acoustic emission(AE) characteristics of C/SiC composite component under various conditions were compared, with the purpose of identifying the possible damage and failure mechanism. During the process of the single mechanical loading, the highest amplitude of the AE signal was less than 85 dB and the main damage forms of matrix cracking and interface debonding were involved. For the heating process, high-energy AE signals with an amplitude more than 85 dB were detected and fiber fracture mechanism was determined as well due to the thermal stress caused by the mismatch of the thermal expansion coefficient between the reinforced fiber and matrix. During the combination process of the heating and mechanical loading, it was concluded that the degree of damage was much severer than the simple superposition of damage produced by the individual mechanical loading and the individual heating process. 展开更多
关键词 C/SIC复合材料 声发射特性 机械载荷 加载过程 热载荷 加热过程 损伤程度 基体开裂
Experimental study of seepage characteristics of single rock fracture based on stress states and stress history 预览 被引量:2
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作者 ZHANG Chi ZHANG Yanjun +3 位作者 LI Zhengwei ZHANG Tong LIU Tong XIE Yangyang 《世界地质:英文版》 2016年第3期177-181,共5页
Through seepage tests under different loading and unloading confining pressures and different hydraulic gradients,the authors studied the effects of stress states and stress history on fracture permeability evolution ... Through seepage tests under different loading and unloading confining pressures and different hydraulic gradients,the authors studied the effects of stress states and stress history on fracture permeability evolution for single granite fracture and sandstone fracture. The results show that there exists a linear relationship between the seepage discharge and osmotic pressure in sandstone fissure under each level of confining pressure. With the increasing in the confining pressure,the permeability of the fracture decreases,but the decreasing rate is changeing. During the unloading process,the fracture seepage velocity cannot be fully recovered to the size of the loading process. Therefore,in the unloading process of the confining pressure,the recovery of fracture permeability shows obvious hysteresis effects. The flow rate of the fracture remains unchanged during five cycles of loading and unloading processes of the confining pressure. In each cycle,the evolution character of the flow rate with the confining pressure remains unchanged. These experiments show that the seepage characteristics of sandstone and granite fractures are not the same under the same stress state. 展开更多
关键词 裂隙渗流 应力状态 特性试验 应力历史 裂缝渗透率 裂隙砂岩 卸载过程 加载过程
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Method of Prototyping Sensitive Dynamic Engineering Structures Supporting Automatic Information Identification Regarding a Structure's Condition 预览
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作者 Tomasz Owerko 《土木工程与建筑:英文版》 2016年第8期912-918,共7页
关键词 工程结构 信息识别 结构条件 敏感 算法分析 原型 希尔伯特变换 加载过程
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自然和饱水煤样受载破坏声发射特征实验研究 被引量:1
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作者 王笑然 刘晓斐 +1 位作者 沈荣喜 邓晓谦 《煤矿安全》 CAS 北大核心 2016年第1期28-32,共5页
开展了单轴压缩自然和饱水煤样受载破坏实验,测试了煤样在整个加载过程中声发射信号脉冲、能量及主频等各参数的变化规律,对比分析了这2种煤样破坏声发射各参数随加载应力变化的差异性,总结了煤样失稳过程中声发射信号的前兆特征。... 开展了单轴压缩自然和饱水煤样受载破坏实验,测试了煤样在整个加载过程中声发射信号脉冲、能量及主频等各参数的变化规律,对比分析了这2种煤样破坏声发射各参数随加载应力变化的差异性,总结了煤样失稳过程中声发射信号的前兆特征。结果表明:在压密阶段,2种煤样脉冲数和能量值较小,频带范围较宽,主频不突出;在线弹性阶段,自然煤样声发射脉冲数、能量值及主频波动上升,而饱水煤样在该阶段中后期声发射现象才开始明显出现;随着加载的进行,2种煤样声发射都出现了平静期,饱水煤样平静期出现较晚,持续时间也较短;煤样主频逐渐向低频移动,主频振幅却呈现出快速增高后下降趋势。 展开更多
关键词 自然煤样 饱水煤样 加载过程 声发射特征 前兆信息 单轴压缩
Effects of particle size and confining pressure on breakage factor of rockfill materials using medium triaxial test 预览
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作者 Ashok Kumar Gupta 《岩石力学与岩土工程学报:英文版》 CSCD 2016年第3期378-388,共11页
Rockfill dams are mostly constructed using blasted rockfill materials obtained by blasting rocks or alluvial rockfill materials collected from the riverbeds.Behaviors of rockfill materials and their characterization s... Rockfill dams are mostly constructed using blasted rockfill materials obtained by blasting rocks or alluvial rockfill materials collected from the riverbeds.Behaviors of rockfill materials and their characterization significantly depend on breakage factor observed during triaxial loading.In this paper,two modeled rockfill materials are investigated by using medium triaxial cell.Drained triaxial tests are conducted on various sizes of modeled rockfill materials used in the two dams,and test data are analyzed accordingly.Breakage factor of rockfill material is studied and the effects of particle size and confining pressure on breakage factor are investigated using medium triaxial cell as many researchers have already conducted investigation using large triaxial cell. 展开更多
关键词 三轴试验 堆石料 破碎 颗粒大小 围压 颗粒尺寸 加载过程 破坏因素
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考虑加载过程及桩体固结变形的碎石桩复合地基固结解析解 预览
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作者 郭彪 龚晓南 李亚军 《工程地质学报》 CSCD 北大核心 2016年第3期409-417,共9页
为了完善碎石桩复合地基固结理论,通过假设从桩体排出的水量等于流入桩体的水量与桩体体积变化之和以及地基扰动区土体水平渗透系数呈线性变化,并考虑上部荷载逐渐施加,推导了考虑桩体体积变化的碎石桩复合地基超静孔压及固结度解析解... 为了完善碎石桩复合地基固结理论,通过假设从桩体排出的水量等于流入桩体的水量与桩体体积变化之和以及地基扰动区土体水平渗透系数呈线性变化,并考虑上部荷载逐渐施加,推导了考虑桩体体积变化的碎石桩复合地基超静孔压及固结度解析解。当加载时间趋于零时,本文解可退化为瞬时加载情况下的解;当加载时间及桩径同时趋于零时,本文解可进一步退化为Terzaghi一维固结解,这证明了本文解的正确性。通过与已有解的比较,对地基固结性状进行了分析。结果表明,加载过程对地基固结度影响显著,加载历时越长,固结越慢;在各种条件下,不考虑桩体固结变形时地基固结始终比考虑桩体变形时快,并且其影响随着加载历时变小、桩径比变小、桩土模量比变小、桩土渗透系数变小而逐渐增大,这说明在实际工程固结计算中不考虑桩体固结变形是偏于不安全的。 展开更多
关键词 碎石桩复合地基 固结 加载过程 桩体固结变形 解析解
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Experimental research on acoustic wave velocity of frozen soils during the uniaxial loading process 预览
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作者 DongQing Li Xing Huang +2 位作者 Feng Ming Yu Zhang Hui Bing 《寒旱区科学:英文版》 CSCD 2015年第4期323-328,共6页
Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM?-SY5(T) nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental r... Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM?-SY5(T) nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental results indicate that the P-wave velocity is affected by soil materials, temperature, and external loads, so the P-wave velocity is different in frozen silt and frozen sand, but all decrease with an increase of temperature and increase at first and then decrease with strain during the loading process. There is an exponential relationship between uniaxial compressive strength and P-wave velocity, and the correlation between them is very good. The characteristic parameters of acoustic waves can, to some extent, reflect the development of internal cracks in frozen soils during loading. 展开更多
关键词 声波速度 加载过程 单轴加载 实验 冻土 纵波速度 单轴抗压强度 超声检测仪
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Optical attenuator based on phase modulation of a spatial light modulator
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作者 刘超 王迪 +2 位作者 姚黎晓 李磊 王琼华 《中国光学快报:英文版》 SCIE EI CAS CSCD 2015年第8期105-108,共4页
In this Letter, we propose an optical attenuator based on the phase modulation of a spatial light modulator(SLM). In this system, we use two polarized beam splitters(PBSs) to control the polarized light and one SLM to... In this Letter, we propose an optical attenuator based on the phase modulation of a spatial light modulator(SLM). In this system, we use two polarized beam splitters(PBSs) to control the polarized light and one SLM to modulate the phase of the polarized light. In the initial state, the light beam is divided into p-light and s-light when it passes through the first PBS. When the light passes through the second PBS, s-light is reflected and p-light is detected by the CCD camera. By loading different grayscales on the SLM, p-light changes its polarized state to s-light. The light power can be attenuated during the loading process. Our experiment shows that the system can obtain a wide optical attenuation from 1–27.2 d B. When loading two grayscales,the SLM has a fast switching time of 25 ms under a low actuated voltage of 5.5 V. The response time of the optical attenuator depends on the switching time of the SLM. Therefore, the system can also have a fast response time. By using the method of spatial multiplexing and adding two mirrors in the system, it can also be extended into a 1 × 2 optical switch. The results verify its feasibility. The optical attenuator has wide applications in photonic signal processing and fiber-optic communication. 展开更多
关键词 空间光调制器 光衰减器 相位调制 加载过程 灰度变化 开关时间 响应时间 偏振分束器
Study on law of raw coal seepage during loading process at different gas pressures 预览 被引量:1
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作者 Meng Junqing Nie Baisheng +1 位作者 Zhao Bi Ma Yechao 《矿业科学技术学报:英文版》 CSCD 2015年第1期31-35,共5页
In order to reveal the law of raw coal seepage at different gas pressures, the gravity constant load seepage experimental system was developed and used. The law of raw coal seepage at different gas pressures with He, ... In order to reveal the law of raw coal seepage at different gas pressures, the gravity constant load seepage experimental system was developed and used. The law of raw coal seepage at different gas pressures with He, N2 and CO2was investigated. The results show that, in a given state of stress during the experiment, with the increase of gas pressure, the permeability of raw coal sample prone to outburst exhibits a significantly decrease, and then exhibits an increasing trend when reaching the extreme point.The law of Klingberg coefficient related to the stress state and the gas adsorption properties was also obtained. Under the same experimental conditions, the Klingberg coefficient of He is greater than that of N2; and the Klingberg coefficient of CO2 has minimum value; so the stronger the gas adsorption is,the smaller the Klingberg coefficient of gas goes. Klinkenberg coefficient decreases with the increase of effective stress. Under the same conditions, the permeability of He is greater than that of N2; the permeability of CO2 has minimum value; so the stronger the gas adsorption is, the lower the permeability of the coal sample goes. The results have important significance in revealing the mechanism of gas seepage, predicting coal mine gas disaster, and gas drainage and safety production. 展开更多
关键词 气压带 渗流规律 原煤 加载过程 气体压力 应力状态 气体吸附 渗透率
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大型风电叶片单点疲劳加载过程振动特性研究 预览
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作者 李忠祥 刘卫生 +1 位作者 张欣 张磊安 《风能》 2015年第12期78-80,共3页
风能已经成为世界上增长最快的新能源,随着风电机组单机容量的不断增大,叶片的尺度也在相应增加。叶片作为风电机组最基础、最关键的部件之一,其制造成本约占风电机组总成本的20%-30%。众所周知,疲劳损伤是导致叶片损坏的主要原因之一,... 风能已经成为世界上增长最快的新能源,随着风电机组单机容量的不断增大,叶片的尺度也在相应增加。叶片作为风电机组最基础、最关键的部件之一,其制造成本约占风电机组总成本的20%-30%。众所周知,疲劳损伤是导致叶片损坏的主要原因之一,严重影响着叶片的使用寿命和安全运行, 展开更多
关键词 叶片损坏 风电机组 疲劳损伤 振动特性 加载过程 单点 单机容量 制造成本
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Direct Laser-Driven Quasi-Isentropic Compression on HEAVEN-I Laser
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作者 张品亮 汤秀章 +9 位作者 李业军 王钊 田宝贤 殷倩 陆泽 向益淮 高智星 李静 胡凤鸣 龚自正 《中国物理快报:英文版》 SCIE CAS CSCD 2015年第7期95-98,共4页
关键词 激光直接驱动 准等熵压缩 上升时间 流体力学模拟 典型剖面 脉冲形状 单调增加 加载过程
Efficient loading of a single neutral atom into an optical microscopic tweezer
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作者 何军 刘贝 +3 位作者 刁文婷 王杰英 靳刚 王军民 《中国物理B:英文版》 SCIE EI CAS CSCD 2015年第4期180-183,共4页
A single atom in a magneto–optical trap(MOT) with trap size(hundreds of micrometers) can be transferred into an optical microscopic tweezer with a probability of ~100%. The ability to transfer a single atom into two... A single atom in a magneto–optical trap(MOT) with trap size(hundreds of micrometers) can be transferred into an optical microscopic tweezer with a probability of ~100%. The ability to transfer a single atom into two traps back and forth allows us to study the loading process. The loading probability is found to be insensitive to the geometric overlap of the MOT and the tweezer. It is therefore possible to perform simultaneously loading of a single atom into all sites of the tweezer array for many qubits. In particular, we present a simulation of the one-dimensional and two-dimensional arrays of an optical microscopic tweezer. We find the same qualitative behavior for all of the trap parameters. 展开更多
关键词 光学显微镜 中性原子 装载 陷阱参数 加载过程 原子转移 定性行为 MOT
煤样加载过程声发射响应特征试验研究 预览 被引量:3
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作者 贾炳 倪小明 苏承东 《煤炭科学技术》 CAS 北大核心 2014年第7期33-36,共4页
为了探究不同裂隙发育程度、分布非均匀程度的煤样在加载过程中声发射响应规律,利用RMT-150B岩石力学伺服试验系统和声发射监测系统对寺河矿不同裂隙发育程度、分布非均匀程度的煤样进行原始渗透率和加载过程中声发射参数测试。结果表明... 为了探究不同裂隙发育程度、分布非均匀程度的煤样在加载过程中声发射响应规律,利用RMT-150B岩石力学伺服试验系统和声发射监测系统对寺河矿不同裂隙发育程度、分布非均匀程度的煤样进行原始渗透率和加载过程中声发射参数测试。结果表明:裂隙分布较均匀的煤样加载时,声发射能量在塑性变形阶段前期或弹性变形阶段后期快速增至最大值,后略有减小并维持在一定水平;裂隙分布非均匀性强且裂隙发育的煤样加载时,声发射能量在弹性变形初期就达较高值,后逐渐增加至最大值,随后稳定在一定值。试验结果对采煤过程中煤岩变形规律具有较好的预测作用。 展开更多
关键词 岩石力学 渗透率 声发射 加载过程
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通过资源优化打造一流应用软件 预览
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作者 曾晨曦 白岩 +2 位作者 李隽 姚金冶 孟祥娇 《世界电信》 2014年第12期73-76,共4页
如今,移动互联网已成为绝大多数应用软件的重要业务支撑。基于网络交互的资源优化对应用开发者至关重要,甚至成为判定网络型应用是否可存活的试金石。开发者应从网络交互的三大基本元素信源、信道、信宿的角度出发,参考内容优化、网络... 如今,移动互联网已成为绝大多数应用软件的重要业务支撑。基于网络交互的资源优化对应用开发者至关重要,甚至成为判定网络型应用是否可存活的试金石。开发者应从网络交互的三大基本元素信源、信道、信宿的角度出发,参考内容优化、网络连接、本地加载三个分析模型,可分别对交互内容在云端的优化、在网络端的传输,以及在终端的本地加载过程实现资源优化。 展开更多
关键词 应用软件 资源优化 应用开发者 网络端 网络交互 业务支撑 加载过程 分析模型 用户体验 客户端请求
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Dislocation-mediated creep process in nanocrystalline Cu 被引量:1
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作者 穆君伟 孙世成 +2 位作者 江忠浩 连建设 蒋青 《中国物理B:英文版》 SCIE EI CAS CSCD 2013年第3期457-465,共9页
Nanocrystalline Cu with average grain sizes ranging from ~ 24.4 to 131.3 nm were prepared by the electric brushplating technique.Nanoindentation tests were performed within a wide strain rate range,and the creep proc... Nanocrystalline Cu with average grain sizes ranging from ~ 24.4 to 131.3 nm were prepared by the electric brushplating technique.Nanoindentation tests were performed within a wide strain rate range,and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined.It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates,and are far higher than those predicted by the models of Cobble creep and grain boundary sliding.The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime.Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity. 展开更多
关键词 蠕变过程 纳米铜 位错 介导 平均晶粒尺寸 加载过程 纳米压痕 颗粒尺寸
溪洛渡拱坝基础置换块浇筑方式研究 预览 被引量:1
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作者 杨志刚 《人民长江》 北大核心 2013年第1期57-60,93共5页
拱坝的基础置换处理加固对高拱坝应力的影响和作用非常敏感,在施工期内,高拱坝的整体结构是随大坝不断浇筑增高、封拱和蓄水而逐渐形成的,坝体结构形式在施工过程中承受的自重荷载与温度荷载也不断变化。采用三维有限元软件对溪洛渡... 拱坝的基础置换处理加固对高拱坝应力的影响和作用非常敏感,在施工期内,高拱坝的整体结构是随大坝不断浇筑增高、封拱和蓄水而逐渐形成的,坝体结构形式在施工过程中承受的自重荷载与温度荷载也不断变化。采用三维有限元软件对溪洛渡拱坝施工期进行了全过程仿真分析,比较了基础置换混凝土的两种浇筑方案对拱坝整个施工期的温度场及温度应力的影响,得到了整个施工过程中拱坝温度场及温度应力变化的一般规律,为控制混凝土拱坝的温度应力和进一步研究拱坝施工期的力学性质提供了理论依据。 展开更多
关键词 施工期 加载过程 温度场 有限元仿真 拱坝 溪洛渡电站中图法
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基于试验数据的滑动摩擦温度场仿真方法研究 预览 被引量:2
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作者 魏巍 俞建卫 +2 位作者 沈持正 尤涛 余晓芬 《中国机械工程》 CAS CSCD 北大核心 2013年第18期2426-2430,2436共6页
建立摩擦温度场的理论计算模型,根据实时变化的摩擦因数,采用三种不同的加载过程对摩擦温度场进行仿真计算,探讨了摩擦热的产生及传导过程。试验及仿真结果表明,热流率平均加载不能体现摩擦过程中摩擦因数的变化对摩擦温度的影响,... 建立摩擦温度场的理论计算模型,根据实时变化的摩擦因数,采用三种不同的加载过程对摩擦温度场进行仿真计算,探讨了摩擦热的产生及传导过程。试验及仿真结果表明,热流率平均加载不能体现摩擦过程中摩擦因数的变化对摩擦温度的影响,仿真时考虑接触位置的旋转半径及摩擦因数的实时变化能更准确地反映实际的摩擦温度变化。热量产生后由接触区域向四周扩散,下试样的温度梯度在接触区域正下方达到最大;同样的试验条件下,由于下试样材料热物理性质具有差异性,从而使得热传导率越高的下试样分配的热量越多,且其温度分布越均匀。 展开更多
关键词 滑动摩擦 温度场 试验 加载过程 仿真
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固体炸药的磁驱动准等熵压缩特性研究 预览
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《中国工程物理研究院科技年报》 2012年第1期52-54,共3页
传统的冲击压缩加载使得炸药在很短时间、很低压力范围就会发生强烈的化学反应,这使得验证和校核爆轰理论模型和本构关系时,缺乏较宽压力范围内未反应炸药的动态压缩力学特性的实验数据支持。而磁驱动准等熵压缩加载可改善这种状况,... 传统的冲击压缩加载使得炸药在很短时间、很低压力范围就会发生强烈的化学反应,这使得验证和校核爆轰理论模型和本构关系时,缺乏较宽压力范围内未反应炸药的动态压缩力学特性的实验数据支持。而磁驱动准等熵压缩加载可改善这种状况,其加载压力平滑上升,加载过程时间达数百纳秒甚至微秒,样品熵增和温升较低,对热点形成抑制作用,拓宽了炸药未发生明显反应的压力上限,可为爆轰理论研究提供更为精确的实验数据。 展开更多
关键词 准等熵压缩 固体炸药 磁驱动 压缩特性 压力范围 加载过程 化学反应 爆轰理论
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体内张拉成形空间网格结构静力试验研究
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作者 王磊 张毅刚 张其林 《土木工程学报》 EI CSCD 北大核心 2011年第4期1-7,共7页
与传统桁架结构不同,体内张拉成形空间网格结构通过张拉下弦管内钢索使结构成形,成形后结构上弦弯曲,呈现自平衡状态。完成了体内张拉成形空间网格结构1∶10缩尺模型的成形及静载试验,研究结构在受荷过程中杆件应力和节点位移的变化规律... 与传统桁架结构不同,体内张拉成形空间网格结构通过张拉下弦管内钢索使结构成形,成形后结构上弦弯曲,呈现自平衡状态。完成了体内张拉成形空间网格结构1∶10缩尺模型的成形及静载试验,研究结构在受荷过程中杆件应力和节点位移的变化规律,结构成形阶段以弯曲应变为主,受荷阶段以轴向压应变的增加为主。结果表明分次分批张拉方案切实可行,面向工程实际的张拉方法可为该类结构的设计施工提供指导。荷载作用下结构整体竖向位移很小,预应力的施加提高了结构的刚度。确定上弦截面最不利杆件位置,建议在设计中采取加强措施。 展开更多
关键词 体内张拉 加载过程 试验研究
大型复杂截面型材拉弯成形数值模拟 预览 被引量:2
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作者 孟鹏飞 李晓星 +2 位作者 金朝海 高宏志 尹萍 《航天制造技术》 2010年第6期50-54,共5页
对一种复杂截面型材的拉弯成形过程进行了有限元数值模拟分析。通过模拟试验得到最佳的模具与型材间隙;通过分析预拉量和补拉量对截面畸变和回弹的影响,得出最佳加载过程参数。对大尺寸异型截面型材的模拟过程进行了优化,解决了拉弯成... 对一种复杂截面型材的拉弯成形过程进行了有限元数值模拟分析。通过模拟试验得到最佳的模具与型材间隙;通过分析预拉量和补拉量对截面畸变和回弹的影响,得出最佳加载过程参数。对大尺寸异型截面型材的模拟过程进行了优化,解决了拉弯成形模拟中动态效应明显、计算量过大等问题。 展开更多
关键词 型材拉弯 数值模拟 模具与型材间隙 复杂截面型材 加载过程
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