树脂基复合材料裂尖损伤的直接观察与分析

用扫描电镜对ＥＮＦ试样在加载及保持过程中裂尖损伤的萌生、演化过程进行了原位观察研究．结果表明石墨／环氧复合材料ＡＳ４／３５０２裂尖损伤的微观机制是微裂纹的萌生、长大及合并．裂尖损伤区内经历的微损伤过程增加了材料的裂纹扩展抗力而使材料得到韧化．     

岩石单轴压缩下破坏失稳过程SEM即时研究

通过在扫描电镜下进行单轴加载实验,即时观察分析岩石受力过程中微裂纹的萌生、扩展和贯通破坏的全过程,得到各试样的应力 应变曲线及其所对应的微结构变化的电镜照片·实验结果表明,岩石试件的变形与破坏过程可以分为裂纹压密、微裂纹萌生和扩展以及断裂破坏３个阶段;微裂缝首先在预裂缝周围的拉应力集中区产生,随着外载荷的增加不断扩展,最后形成与最大主应力方向平行的宏观断裂带·     

循环加载下砂岩断裂特性试验及模拟

利用WHY-200/10微机控制万能试验机,对红砂岩人字形切槽圆盘试样(CCNBD)进行静态与循环加卸载试验,研究在循环加卸载下红砂岩的Ⅰ型断裂力学特性及变形特征;并基于红砂岩的宏观力学参数进行PFC3D数值模拟试验,探究微裂纹扩展规律.试验结果表明:循环荷载的作用会使砂岩的Ⅰ型断裂韧度值KⅠC减小;且随着循环次数的增加,砂岩的Ⅰ型断裂韧度逐渐减小,直至达到某一下限值;砂岩CCNBD循环加载曲线受到其静态加载曲线的严格控制,循环加载破坏点变形量与静载曲线中同荷载水平下峰后变形量相近;循环加载下试样的径向位移变形过程和微裂纹扩展规律与上限荷载比相关,主要有3个阶段:初期加载阶段、中期稳定阶段、后期加速阶段;当上限比为0.95时,试样的径向位移变形过程和微裂纹扩展只有初期和加速阶段;当上限比为0.75时,其位移变形和微裂纹扩展只有初期和稳定阶段,且不发生断裂破坏;循环加载下试样韧带两端断裂过程区(FPZ)的微裂纹发生充分衍生和扩展,最终的微裂纹数目明显多于静态加载.     

16MnR钢中疲劳裂纹扩展的细观研究

采用显微疲劳试验方法和显微疲劳试验装置对低合金钢１６ＭｎＲ单边缺口试样进行了疲劳试验,研究了短裂纹萌生和扩展的特征。结果表明,短裂纹萌生及扩展分三个阶段,每一阶段的形貌都有其特点,在裂纹扩展后期,短裂纹的发展以裂纹密度不断增加并形成损伤区为主要特征,然后在损伤区选择一条主裂纹扩展。     

损伤跨尺度演化导致的混凝土强度尺寸效应

基于直接从混凝土破坏机理出发建立的混凝土材料微裂纹模型,对不同尺寸的混凝土三点弯梁试样进行了多尺度建模,对损伤演化导致的试样破坏进行了数值仿真分析,探讨了混凝土尺寸效应的发生机理.研究结果表明:混凝土材料微裂纹模型能成功模拟混凝土中微裂纹分布式生长、聚合、宏观裂纹形成与扩展、试样破坏的全过程;随着混凝土梁试样尺寸的增大,试样中的微裂纹数目及其分布的随机性也随之增加;这些裂纹在微细观尺度上的无序效应在损伤跨尺度演化过程中被放大,导致混凝土试样的宏观力学行为随之变化,即强度减小,断裂能增大,宏观性能的离散度减小;损伤跨尺度的非线性串级发展是导致混凝土强度尺寸效应的根源;相较于Bazant尺寸效应,模拟结果更符合Carpinteri多重分形尺寸效应律.     

双孔洞裂隙砂岩裂纹扩展特征试验与颗粒流模拟

基于尺寸为80mm×160mm×30mm的双孔洞裂隙长方体砂岩试样单轴压缩试验结果,分析了双孔洞裂隙砂岩裂纹扩展特征,建立了双孔洞裂隙砂岩宏观应力-应变曲线与裂纹扩展过程的关系.利用颗粒流模拟程序,基于试验结果进行细观参数校准,进一步研究了裂隙倾角对双孔洞裂隙试样力学参数及裂纹扩展特征的影响.与完整砂岩试样相比,双孔洞裂隙试样力学参数显著降低,但降低程度与裂隙倾角密切相关.随着裂隙倾角的增大,双孔洞裂隙试样峰值强度先减小后增大,弹性模量呈逐渐增加的趋势,而峰值应变呈非线性变化.完整试样呈轴向劈裂脆性破坏,而双孔洞裂隙试样首先在孔洞上下边缘及裂隙的尖端附近萌生初始裂纹,裂纹的扩展与贯通导致了试样最终失稳破坏.最后探讨了双孔洞裂隙试样裂纹扩展细观机制:首先在裂隙尖端附近和孔洞边缘形成应力集中区,应力提高导致颗粒间黏结断裂,产生微裂纹;在应力集中区转移过程中不断产生新的微裂纹,微裂纹的汇集形成宏观裂纹.     

高温环境2A12–T4铝合金多轴疲劳失效规律研究

许多工程结构在服役过程中往往承受着复杂的多轴疲劳载荷和热力耦合作用,仅靠常温情况下的单周载荷来简化复杂多轴载荷状态的失效预测方法将不再适用。为研究2A12–T4铝合金的高温多轴疲劳失效规律,本实验在175℃环境温度下,选取等效Von-Mise应力幅值,通过间断式加载记录不同拉扭加载循环下的裂纹萌生与扩展情况,研究特定加载路径对裂纹萌生与扩展的影响。实验结果表明,相位差为0时,裂纹萌生方向沿MSSA平面;在相位差为45°时,裂纹萌生传播方向与最大切应力平面方向相近,最大切应力在裂纹萌生过程中起到主要作用;在λ=0.5、φ=0和λ=1.0、φ=0两种情况下,裂纹萌生初期沿着最大切应力平面方向传播,传播过程中存在第I阶段向第II阶段转变的过程;在λ=0.5、φ=45°和λ=1.0、φ=45°两种情况下,不存在明显的第I阶段向第II阶段转变的过程;对比4种加载方式下的疲劳裂纹萌生期与疲劳寿命比,发现切应力比重的增大加速裂纹的萌生过程,相位差的存在阻碍了裂纹的萌生过程。     

基于声发射监测的巴西盘试样破裂过程

应用声发射及盖格尔定位算法,实验研究了不同巴西盘岩样加载破裂失稳过程.结果表明:声发射事件主要由于裂纹扩展产生,在初始加载阶段直至裂纹萌生之前,其声发射活动不是很明显;一旦岩样出现初始裂纹,在相应的应力点声发射事件明显增多;在微裂纹扩展的非稳定阶段至岩石破坏瞬间,声发射活动变得异常活跃,声发射事件变化率最大.由此直观反映了巴西盘试验过程初始裂纹的产生、扩展空间位置及扩展方向,即大部分试样的破坏是从一加载端开始,而少数试样的初始裂纹是在岩样的内部产生.同时,声发射事件定位也是岩样内部应力场演化过程的宏观表现,这对于深入研究岩石破裂失稳机制很有意义.     

管道高周腐蚀疲劳损伤模型与数值模拟研究

根据疲劳与应力腐蚀损伤的耦合效应,利用非线性累积原理,构建了金属材料的高周疲劳损伤演化模型。以API X65管道钢为研究对象,结合实验确定了腐蚀疲劳损伤演化参数。利用ABAQUS软件二次开发模拟了含不同腐蚀坑形状的管材试样腐蚀的疲劳损伤演化与裂纹萌生过程,探讨了腐蚀疲劳裂纹萌生对腐蚀坑形貌的敏感性。结果表明：腐蚀坑宽度与深度相同时,半椭球型腐蚀坑试样腐蚀疲劳裂纹萌生寿命最长,圆台型与圆锥型次之,矩形体腐蚀坑试样裂纹最先萌生;半椭球体腐蚀坑试样应力腐蚀损伤对总损伤的贡献量始终大于疲劳损伤,而对于其他类型腐蚀坑,腐蚀疲劳裂纹萌生主要源于疲劳损伤的累积。     

固态金属致脆裂纹的萌生与致脆原子输运机制

提出了利用锥形试样,以离子束增强沉积银实现银与试样表面接触,并通过慢应变速率拉伸加载,确定了Ｔｉ６Ａ１４Ｖ合金固体银致脆裂纹萌生应力,萌生应变、萌生寿命和裂纹扩展临界应力强度因子的方法。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with