T225NG合金的高温单轴棘轮行为研究

在200、300、350、450℃等温度下对T225NG合金进行了单轴棘轮行为试验研究,分析了温度、应力幅值、低峰值应力棘轮历史对T225NG合金棘轮行为的影响.研究表明,在高温下峰值真应力具有对T225NG合金饱和棘轮应变控制的一元特性,饱和棘轮应变与幅值和先前的低峰值应力棘轮历史无关;在相同峰值应力下,温度越高则塑性应变累积越迅速,饱和棘轮应变越大;高温下T225NG合金出现异化的棘轮应变演化关系,现有本构理论难以描述.基于单试样多级加载试验方法,建立了一个用于预测T225NG合金单轴高温饱和棘轮应变的本构模型,该模型对试验数据有较好的相关性,可以较好地描述单轴棘轮应力与饱和棘轮应变之间的关系.     

Abdel-Karim-Ohno模型改进及Z2CDN18.12N不锈钢棘轮效应预测

为更好地描述Z2CDN18.12N奥氏体不锈钢的单轴棘轮行为，在统一黏塑性循环本构理论框架下，改进了Abdel-Karim-Ohno模型.将塑性应变记忆面引进各向硬化率中，之后进行模型参数确定，进而用Abdel-Karim-Ohno模型和改进Abdel-Karim-Ohno模型对Z2CDN18.12N奥氏体不锈钢在室温下的单轴棘轮效应进行研究.利用两种模型分别研究了平均应力、应力幅值、应力率及加载历史等对Z2CDN18.12N奥氏体不锈钢单轴棘轮行为的影响.结果表明：在恒定的加载率条件下，单轴棘轮应变水平随平均应力和应力幅值的增大而提高；随应力率的增大而降低，而且对较低的应力率更为敏感；单轴棘轮行为受加载历史影响显著.通过对比两种模型对材料的单轴棘轮行为的预测结果与试验数据，证明了本文改进模型的有效性.     

基于反双曲正弦函数的循环本构模型

为改善本构模型对循环变形应力-应变滞回环的预测能力，基于反双曲正弦函数提出了一个新的随动硬化律。在该硬化律中，背应力分为长程、中程和短程3部分，并且每部分都符合“A-F”硬化律的演化形式（即包含线性项和动态恢复项）。在长程和中程背应力中，动态恢复系数逐渐演化以描述大变形瞬态包辛格效应，并且系数中引入了棘轮系数以描述材料的棘轮行为；在短程背应力中，线性项和动态恢复项分别由两部分组成，其中一部分只在反向屈服发生时起作用以描述小变形下反向屈服塑性模量降低的行为。在单调加载时，该随动硬化律可以积分为一个反双曲正弦函数，并且调控单调加载响应、棘轮变形演化和滞回环形状的参数互不耦合。基于该随动硬化律，在次弹性大变形框架下建立了循环本构模型，并考察了其对棘轮变形和应力-应变滞回环的预测能力。     

基于A-V模型的改进模型及单轴棘轮效应预测

针对A-V模型预测材料棘轮效应初始阶段不理想的缺点，对其参数γ₂进行了修正，同时引入Ramberg-Osgood(R-O)模型和各向同性硬化来计算应力-应变曲线，并确定了A-V模型的材料参数，建立了一种用来描述材料循环塑性行为的改进A-V模型.通过采用改进的A-V模型对Z2CND18.12N奥氏体不锈钢和SS316L钢的单轴棘轮效应进行了预测，并研究了平均应力、应力幅值、应力比和加载历史对单轴棘轮效应的影响.结果表明，改进的A-V模型对材料的棘轮应变预测值与试验值较为一致.     

描述T225NG钛合金高温单轴棘轮行为的黏塑性本构模型

在350℃下对T225NG钛合金进行了单轴棘轮试验研究，提出了一种新的带有记忆面的黏塑性本构模型．引入了能记忆最大应变的记忆面，在记忆面内和面上采用不同形式的塑性流动律，将单调拉伸响应和循环响应独立开来，简化了模型参数的确定方法．在背应力随动硬化演化方程中引入了等效应变门槛值，可较好地描述T225NG钛合金应力一应变曲线的屈服平台及其后的强化效应．加入黏性指数修正，可描述棘轮应变率随循环次数迅速衰减的试验现象．将模型应用于T225NG钛合金350℃单轴棘轮行为描述中，对饱和棘轮应变的预测结果与试验结果吻合较好．     

高铁齿轮钢18CrNiMo7-6循环变形行为 实验和本构模型

采用RPL100电子式蠕变疲劳试验机,对高铁齿轮钢18CrNiMo7-6开展了不同应变幅值下的对称应变循环实验,研究了齿轮钢在对称应变循环下的循环软硬化行为;对齿轮钢18CrNiMo7-6在不同应力工况下开展了非对称应力循环下单轴棘轮行为实验,研究了齿轮钢棘轮变形的演化规律.结果显示,在实验研究循环周次内齿轮钢18CrNiMo7-6在对称应变控制循环下表现出循环软化的特征,在非对称应力控制循环下呈现出衰减的棘轮应变率和常棘轮应变率两阶段.通过在Ohno-Abdel-Karim非线性随动硬化律中引入与累积塑性应变相关的棘轮参数的演化方程,建立了修正的循环弹塑性本构模型.模拟结果显示,该模型能够合理预测齿轮钢18CrNiMo7-6的循环软化特征和棘轮行为的演化规律.     

高应力幅循环历史对U78CrV钢棘轮行为的影响

U78CrV钢轨广泛应用于我国重载铁路,在服役过程中承受具有不同循环历史的滚动接触疲劳载荷,由此诱发的棘轮行为将加剧钢轨的疲劳失效。首先开展低应力幅和高应力幅下的非对称应力控制循环实验,随后进行具有不同循环周次高应力幅循环历史的低应力幅值循环实验,揭示应力幅和应力循环历史对U78CrV钢棘轮行为的影响。实验结果显示,U78CrV钢在非对称应力循环载荷作用下表现出显著的棘轮行为,应力幅的增加会提高棘轮应变和棘轮应变演化率;预加载的高应力幅循环周次越高,随后的低应力幅下的棘轮行为越明显;不同循环周次的高应力幅循环历史降低了低应力幅循环的棘轮应变率,但增加了耗散能密度;不同高应力幅循环历史下的低应力循环疲劳寿命与失效棘轮应变和稳定耗散能密度密切相关,随着失效棘轮应变和稳定耗散能密度的增加而降低。基于稳定耗散能密度建立了幂律函数,可以合理预测高应力幅循环历史的低应力循环疲劳寿命。研究结果对U78CrV钢轨的疲劳失效评估具有重要的参考价值。     

热轧和热处理U75V钢单轴棘轮-疲劳交互作用实验研究

钢轨服役过程中,由循环滚动载荷诱发的棘轮效应是其疲劳失效的主要原因之一。针对现役的热轧和热处理U75V钢开展单调拉伸、应变和应力控制疲劳实验,揭示热处理工艺对材料基本力学性能、循环特性和棘轮行为的影响,进而讨论棘轮效应与疲劳失效行为之间的交互作用。实验结果表明:热处理U75V钢的屈服强度和抗拉强度较热轧态有显著提升,二者均表现出循环软化特性。在相同载荷水平下热处理U75V钢抗棘轮变形能力和疲劳性能明显优于热轧态,当应力幅与屈服应力之比恒定时,相同平均应力下热轧U75V钢棘轮效应更显著。加载的平均应力和应力幅对U75V钢疲劳寿命的影响存在竞争作用,较强的棘轮行为使两种U75V钢疲劳寿命均降低。     

不同应变率下的盐岩损伤声发射时空演化

利用RMT-150B岩石力学多功能系统和声发射监测系统,对不同应变率下盐岩损伤的声发射时空演化规律进行试验,同时分析不同加载应变率对盐岩单轴压缩过程的极限强度和变形的影响.研究表明:盐岩在2种不同应变率下的损伤声发射时空演化趋势大致相同,压密和弹性阶段都经历很短时间;弹性阶段定位点数量呈线性增长,塑性阶段初期定位点快速增加,塑性阶段中后期,定位点增加速度逐步减小;在破坏阶段,应力虽然降低,但仍有相当数量定位点出现.应变率对盐岩的损伤有较大影响,应变率越大,定位点数量越少;应变率越小,定位点数量越大.应变率对单轴压缩盐岩的极限强度影响不大,对变形影响较大,盐岩塑性变形在低加载应变率时较大,在高加载应变率时较小;在峰值强度前后,加载应变率越小,塑性变形特征越明显.     

一种适用于高强度炮钢的塑性理论

该文提出了一种适用于高强度炮钢的塑性理论。该理论充分考虑了Ｂａｕｓｃｈｉｎｇｅｒ效应。及材料正向与反向加载时不同的塑性模量。与现有的理论相比，更加细致的抛述了材料塑性变形的力学行为；便于数学处理及在数值计算中应用。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with