沥青路面Top-Down裂缝的断裂力学分析

采用移动荷载模式,在有限元方法中利用动态模量主曲线和时间-温度位移因子来表征沥青混合料的力学性质,利用断裂力学的方法分析了温度、车速、裂缝长度和基层类型等对沥青路面Top-Down裂缝裂尖应力强度因子的影响.研究表明随着裂缝长度增加和温度降低,张开型应力强度因子(KⅠ)和剪切型应力强度因子(KⅡ)的峰值增加.行车速度对应力强度因子的作用频率有显著影响,较慢的行车速度会加速Top-Down裂缝的扩展.与采用粒料基层相比,采用半刚性基层可降低裂尖应力强度因子.随着温度升高和裂缝长度增加,KⅠ对裂缝扩展的贡献减小,而KⅡ的贡献逐渐增加.     

交通荷载作用下沥青路面裂缝尖端的应力强度因子分析

考虑沥青混合料粘弹性断裂力学行为,对于沥青路面的开裂或反射性裂缝的扩展行为研究具有重要意义.基于粘弹性断裂理论,采用非线性有限元软件ABAQUS,分析交通动荷载作用下不同车速、不同基层模量对含有裂缝路面结构体系的位移场和应力场的影响.计算结果表明:裂缝尖端应力强度因子变化曲线随着车速的增加发生移动,且峰值几乎不变;随着基层模量的增加,应力强度因子增大.在偏荷载作用下裂缝尖端应力强度因子由KⅠ、KⅡ组成,当基层模量较小时裂缝尖端应力强度因子主要表现为KⅡ,随着弹性模量的增加KⅠ增大,KⅡ几乎保持不变.     

基于权函数法的沥青路面基-面层裂缝的扩展行为

为了研究半刚性基层沥青混凝土路面在行车荷载作用下出现的基层反射裂缝及其扩展规律,基于黏弹性断裂力学理论和权函数法,对反射裂缝的应力强度因子进行了分析,推导了Ⅰ-Ⅱ复合型裂纹断裂判据理论.采用数值模拟方法分析了结构层厚度及荷载位置对基层反射裂缝的影响,并通过单边切口小梁试验研究了面层裂缝扩展模式.研究结果表明:Ⅰ型(K_Ⅰ)和Ⅱ型(K_Ⅱ)应力强度因子受路面结构层厚度的影响较大,在行车荷载作用下Ⅰ型裂纹扩展模式起主导作用,增加基层厚度对防止反射裂纹的产生有一定的效果;在考虑水平荷载作用时,Ⅰ型和Ⅱ型应力强度因子均随荷载位置的变化而变化,随着荷载与裂纹距离的不断增加,K_Ⅰ逐渐减小,K_Ⅱ逐渐增加,反射裂缝逐渐偏向Ⅱ型裂纹扩展模式;在不考虑水平作用时,基层反射裂纹以Ⅰ-Ⅱ复合型形式出现,并在应力集中下向面层扩展,扩展模式表现为Ⅰ-Ⅱ复合型.     

Ⅰ型裂纹的高强混凝土梁断裂性能试验研究

为了研究Ⅰ型裂纹高强混凝土梁在静荷载作用下裂缝尖端微裂区扩展规律,采用三点弯曲梁试验方法。结合双K、双G理论模型分析不同初始缝高比对高强混凝土起裂荷载、失稳荷载、断裂韧度及应力强度因子的影响。试验结果表明:缝高比对起裂荷载与失稳荷载有较大的影响;双K、双G模型得出的起裂韧度理论值很接近且初始缝高比对断裂韧度无明显影响。     

交叉裂纹各裂尖应力强度因子同时快速求解的Williams单元

为了研究交叉裂纹各裂尖应力强度因子之间的相互影响,建立了交叉裂纹各裂尖应力强度因子同时快速求解的Williams单元,以十字交叉裂纹为例,分别对正交十字裂纹或斜十字裂纹各裂尖应力强度因子相关参数进行研究,分析了薄板尺寸、裂纹夹角与奇异区尺寸等相关参数对十字交叉裂纹各裂尖应力强度因子的影响,其中K_Ⅰ、K_(Ⅱ)为裂尖Ⅰ、Ⅱ型应力强度因子。算例分析表明,当板宽与裂纹长度满足W/a≥13时,能够忽略板的尺寸对正交十字裂纹裂尖应力强度因子的影响,可视为无限大板;对于斜十字裂纹情况,当水平裂纹长度不变时,随着斜裂纹长度参数d的增大,K_(Ⅰ,A)、K_(Ⅱ,C)和K_(Ⅰ,D)逐渐递减,而K_(Ⅱ,A)、K_(Ⅰ,B)、K_(Ⅱ,B)和K_(Ⅰ,C)逐渐递增,对于K_(Ⅱ,D)则出现先减后增的趋势;当斜裂纹长度参数d=0时,随着裂纹夹角γ的变化,K_(Ⅰ,A)、K_(Ⅰ,B)大小相等,符号相同,K_(II,A)、K_(Ⅱ,B)则大小相等,符号相反,且各裂尖应力强度因子对裂尖奇异区尺寸不敏感。证明了Williams单元能够同时快速求解交叉裂纹各裂尖应力强度因子,且具有较高的计算精度。     

Ⅰ型裂纹尖端圆弧对应力强度因子的影响

应力强度因子表征了裂纹尖端奇异应力场的强度,它是研究裂纹扩展规律和带裂纹构件强度的基础。本文采用有限元法,对受均布荷载作用存在边缘Ｉ型裂纹的平面板进行了数值分析。研究了裂纹尖端圆弧对应力强度因子的影响,分别计算了具有不同裂尖圆弧 的Ｉ型裂纹的应力强度因子。采用应力法计算不同半径处的表观应力强度因子,插值到裂尖圆弧而得。根据计算结果,绘制KⅠ-r0曲线,利用最小二乘法拟合至尖裂纹（r0=0）即得理想尖裂纹的应力强度因子,与解析解相差仅0.7%。该曲线为带圆弧裂纹的应力强度因子测试和带圆弧裂纹构件强度计算提供了依据     

Ⅰ型裂纹尖端圆弧对应力强度因子影响的数值研究

应力强度因子表征了裂纹尖端奇异应力场的强度,它是研究裂纹扩展规律和带裂纹构件强度的基础。采用有限元法,对受均布荷载作用存在边缘Ⅰ型裂纹的平面板进行了数值分析。研究了裂纹尖端圆弧对应力强度因子的影响,分别计算了具有不同裂尖圆弧r_0的Ⅰ型裂纹的应力强度因子。采用应力法计算不同半径处的表观应力强度因子,插值到裂尖圆弧而得。根据计算结果,绘制K_Ⅰ-r_0曲线,利用最小二乘法拟合至尖裂纹(r_0=0)即得理想尖裂纹的应力强度因子,与解析解相差仅0.7%。该曲线为带圆弧裂纹的应力强度因子测试和带圆弧裂纹构件强度计算提供了依据。     

水力压裂中多裂缝间相互干扰力学分析

将复变函数理论与位错理论相结合 ,在考虑了裂缝表面有流体压力作用且裂缝间存在相互干扰的情况下 ,建立了无限大介质中裂尖应力强度因子的数学模型 ,利用该模型可对水力压裂中多裂缝间的相互干扰进行力学分析。假设裂缝沿着垂直于局部最大周向拉应力方向扩展 ,应用数值方法对所建立的数学模型求解 ,得到裂尖的应力强度因子及转角。数值计算结果表明 ,裂缝间存在相互干扰时所产生的剪切应力强度因子远远小于法向应力强度因子。当两个裂缝尖端垂向距离为零时 ,法向应力强度因子达到最大值。两个裂缝尖端没交叠之前裂缝基本沿着轴线扩展 ;当尖端交叠面积较小时 ,两裂尖偏离自己的轴线向避开对方的方向扩展 ;当尖端交叠面积较大时 ,两裂缝向靠拢对方的方向扩展 ,最终将贯通在一起     

水力压裂中多裂缝间相互干扰力学分析

将复变函数理论与位错理论相结合，在考虑了裂缝表面有流体压力作用且裂缝间存在相互干扰的情况下，建立了无限大介质中裂尖应力强度因子的数学模型，利用该模型可对水力压裂中多裂缝间的相互干扰进行力学分析。假设裂缝沿着垂直于局部最大周向拉应力方向扩展，应用数值方法对所建立的数学模型求解，得到裂尖的应力强度因子及转角。数值计算结果表明，裂缝间存在相互干扰时所产生的剪切应力强度因子远远小于法向应力强度因子。当两个裂缝尖端垂向距离为零时，法向应力强度因子达到最大值。两个裂缝尖端没交叠之前裂缝基本沿着轴线扩展；当尖端交叠面积较小时，两裂尖偏离自己的轴线向避开对方的方向扩展；当尖端交叠面积较大时，两裂缝向靠拢对方的方向扩展，最终将贯通在一起。     

加宽工程路面开裂影响因素的数值分析

基于线弹性断裂力学,使用大型有限元软件ABAQUS对加宽工程路面在2种荷载作用模式下开裂的影响因素进行了分析.对沥青面层厚度和模量的分析结果表明,偏荷载对面层裂缝扩展的影响比正荷载大,增加面层厚度和减小面层模量能降低面层反射裂缝应力强度因子.对老路基层和新路基层模量的分析结果表明新老路基层模量相同时,应力强度因子K2数值最小,几乎为零,并随裂缝扩展长度变化不大,面层反射裂缝扩展的可能性最小,因此,选择合适的新路面结构使其模量与老路基层模量相同是非常重要的.此外,随差异沉降增加,应力强度因子K2略有增大,并且差异沉降越大,K2增大得越明显.这表明除合理选择路面结构外,进行地基处理降低差异沉降也非常重要.     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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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