几何不对称试件启裂前应力变化的激光实验研究

从裂纹技术的需要出发 ,对几何不对称试件进行了启裂前应力状态变化的激光实验力学研究 ,观察有切口试件的应力场变化情况 .结果表明 ,试件在启裂前的应力状态基本上是对称的 ,应力无大的变化 .     

非几何对称试件启裂前应力状态的实验研究

从裂纹技术的需要出发,对几何不对称试件进行了启裂前应力状态变化的光弹性实验力学研究,观察有切口试件的应力场变化情况,结果表明,试件在受力后启裂前的应力状态基本上是对称的     

应力对混凝土断裂参数测定有效性的影响

对于线弹性材料,裂缝尖端平行于裂缝方向的T应力会影响裂缝的扩展方向和起裂断裂韧度,然而在混凝土类准脆性材料的断裂韧度测试中,无论是起裂断裂韧度还是失稳断裂韧度,T应力的影响却少有研究.以混凝土Ⅰ型断裂韧度测试常用的三点弯曲梁、楔入劈拉试件为对象,计算了裂缝尖端的T应力大小,并分析了其对裂缝扩展方向和断裂韧度的影响.分析计算结果表明:这些常用试件裂缝尖端的T应力相比于裂缝尖端控制因素应力强度因子K很小,不会影响裂缝扩展方向,保证了混凝土断裂失稳前一直处于Ⅰ型裂缝状态;另外,T应力对起裂断裂韧度和失稳断裂韧度的数值也不会产生影响,说明常用试件进行的混凝土断裂韧度确定方法是可靠有效的.     

钢筋混凝土圆杆中的应力波传播及层裂研究

利用Φ74 mm的Hopkinson压杆对圆柱型钢筋混凝土试件进行了波传播实验和层裂实验研究,利用应变片记录杆中应力波信号,使用高速摄影机拍摄试件的拉伸破坏过程.实验结果表明：在较低的加载速率下,应力波在钢筋混凝土试件传播过程中呈现弹性波特性,不弥散不衰减;在较高的加载速率下,钢筋混凝土试件出现层裂现象,层裂强度在7 MPa左右;断裂试件中的裂纹在拉压应力波交替作用下反复张开闭合,随着应力波在杆中的衰减而趋于稳定.     

用声发射及断口分析法研究高强钢插销试件氢致裂纹的产生及扩展

用声发射法对高强钢插销试件的氢致裂纹的启裂，扩展以及断裂过程进行了试验研究。发现在环形缺口的插销试件中延迟裂纹的启裂位置是有规律性的，根据Ａ．Ｅ波形可将整个过程划分为启裂、延迟扩展、快速扩展、瞬时断裂四个时期，在断口上也可看到相应的分区，二者之间的对应关系取决于应力、氢．组织诸条件。 此外，还探讨了含氢量、Ｈ ＡＺ组织与性能对断口微观形貌的影响。     

水力耦合作用下三维中空裂隙扩展模式与材料破坏强度的试验研究

采用透明树脂类岩石材料制作含三维中空单裂隙试件,开展水力耦合破裂试验,研究三维裂隙起裂扩展模式,分析裂隙倾角和水压对裂隙起裂应力及试件破坏强度的影响规律。研究结果表明:三维中空裂隙的起裂和扩展模式与闭合裂隙相比差异显著,水力耦合下三维裂隙起裂扩展模式呈现低水压与高水压2种类型,水压升高对裂隙起裂、扩展具有显著的促进作用,并改变试件的破坏模式;随裂隙倾角增大,翼裂纹临界扩展长度逐渐减小,鱼鳍状裂纹的萌生时间呈后延趋势;水压对裂隙起裂应力和试件破坏强度的影响分别存在阈值,在达到阈值前,水压升高使起裂应力小幅度增大,而破坏强度逐渐降低;当水压超过阈值后,起裂应力与破坏强度均迅速降低;裂隙起裂应力和试件破坏强度均随裂隙倾角增大而呈先降低后升高的趋势,但起裂应力的变化幅度比破坏强度的变化幅度更大。     

小缺口疲劳启裂门槛值的平面应力与平面应变效应

文章报告了两组 Q2 3 5钢小缺口试件在平面应力与平面应变条件下的疲劳启裂门槛值的测定结果。实验表明 :不论平面应力还是平面应变状况 ,当ρ→ 0时 ,Δσ∞th均有截止性。但对平面应力状况 ,Δσ∞th截止后持平 ,而对平面应变状况 ,Δσ∞th截止后反有小幅上升。该文从缺口顶端应力场和循环塑性区的展开出发对试件结果作了分析和讨论。     

有/无填充介质对裂纹动态断裂特性影响的实验研究

为了研究有/无填充介质对裂纹动态断裂特性的影响,利用动态焦散线实验方法结合高速相机对含预制缺陷的试件进行了三点弯冲击断裂实验。研究结果表明:冲击载荷作用下运动主裂纹与预制缺陷贯通后,预制裂纹中有/无填充介质影响次生裂纹的起裂位置、数量、起裂模式、起裂所需时间。在预制裂纹中无填充介质的情况下,沿预制裂纹左右两侧对称产生2条次生裂纹,次生裂纹起裂时是Ⅰ+Ⅱ混合模式断裂;在填充环氧树脂介质情况下,沿预制裂纹中心处产生1条次生裂纹,次生裂纹起裂时是Ⅰ型断裂;同时无填充介质试件次生裂纹起裂所需时间大于填充了环氧树脂的试件。     

极限净截面应力与弹塑性断裂参数J_(1c)关系的探讨

从现有的弹塑性断裂理论和结果出发,研究了韧性材料在全面屈服下裂纹启裂参数J_(1c)与相应的极限净截面应力σ_c之间的关系,提出用净截面应力法来分析构件上裂纹启裂行为,使工程断裂力学分析变成易于接受的工程计算。得出:如果给定试样高度和材料,则存在一个与启裂参数相对应的极限净截面应力。     

大骨料混凝土在不连续点处应力和变形研究

通过试验研究大骨料三级配混凝土与其湿筛二级配混凝土在双轴受力状态下的特性,比较了二者于双轴拉压受力情况下在不连续点处的强度和变形特性,并给出了破坏准则.三级配混凝土的最大骨料尺寸为80 mm,试件最小横向尺寸为250 mm;湿筛混凝土的最大骨料尺寸为40 mm,试件最小横向尺寸为150 mm.描述了试件设计、材料配比、加载设备、减摩措施.通过对试验结果的分析看出,不论混凝土试件的骨料和尺寸大小如何,其不连续点处的两轴应力包络线都是相似的,并都可近似于一直线.混凝土在不连续点处的拉应变值与其平均应力具有较高的相关性.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

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     

Journal of Donghua University ( English Edition) Contents of Volume 31

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