岩石的弹塑性扰动状态本构模型

假定岩石的相对完整状态符合分级单屈服面(HISS)模型并考虑其各向同性硬化,岩石的完全调整状态对应于理想刚塑性,通过定义扰动函数,则岩石应力峰值后的软化行为可用HISS模型叠加扰动进行描述,从而建立基于扰动状态概念理论的岩石弹塑性本构模型.利用RMT-150B对焦作砂岩进行单轴、三轴压缩破坏试验,以确定本构模型中的材料参数.应用建立的弹塑性本构模型,对岩石在单轴应力状态下的力学响应进行了描述.研究结果表明,建立的弹塑性本构模型能描述单轴下岩石的应力-应变全过程.     

压缩荷载作用下脆性岩石弹塑性损伤耦合本构模型研究

在压应力作用下,岩石的塑性变形和损伤演化是相互耦合的。在热动力学基本框架下,建立了一个用于描述在压缩荷载作用下脆性岩石非线性力学行为的弹塑性损伤耦合模型。模型采用基于Drucker-Prager线性屈服准则,并同时考虑损伤软化效应的函数作为加载函数。此外,为反映岩石在压应力作用下体积变形从压缩到膨胀的转化过程,引入非关联的塑性流动方程。基于已有的损伤理论,建立含有塑性剪切应变的损伤准则。通过联立屈服准则和损伤准则的一致性条件,建立塑性和损伤发展的耦合关系。运用建立的模型对不同围压下大岗山辉绿岩的常规三轴压缩试验进行模拟。模拟结果和试验数据具有较好的一致性,表明了模型的合理性和有效性。     

考虑粗粒土应变软化特性和剪胀性的本构模型

在传统细粒土本构模型的基础上进行了改进,建立了一个能较好地描述粗粒土应变软化特性和剪胀性的弹塑性本构模型.该模型采用双屈服面形式,克服了单屈服面模型存在的一些不足,可同时反映剪切变形和压缩变形机理.模型在应变软化特性描述方面,提出了一个利用残余状态应力比和峰值应力比的应变软化公式,较为合理地反映了粗粒土的应变软化现象.在剪胀性描述方面,考虑了状态转换应力比与初始有效围压的相关性.数值模拟结果与试验结果较为接近,表明该模型描述粗粒土在低围压和相对中高围压下的应变软化特性和剪胀性方面具有一定的优越性.     

围压作用下岩石峰后应力-应变关系模型

假定峰后软化阶段任意一点皆满足摩尔库仑极限破坏条件,建立岩石峰后后继屈服面模型。利用岩石峰值处和残余阶段初始处应力状态绘制几组莫尔应力圆,获得不同围压下峰值处和残余阶段初始处的黏聚力c和内摩擦角φ,然后分别建立黏聚力c和内摩擦角φ同围压的函数关系。基于莫尔-库仑准则,以最大主应变ε作为软化参数,以分段线性函数形式演化黏聚力c和内摩擦角φ的正切,反求内摩擦角φ,从而建立岩石峰后应力-应变关系模型。数值算例研究Tennessee大理岩三轴试验的峰后应变软化过程,模拟结果与试验结果较吻合。研究结果表明:建立的峰后应力-应变关系模型合理而可靠,可以较好地描述不同围压下岩石的峰后力学行为。     

高应力泥质粉砂岩黏弹塑性蠕变模型

为揭示高应力作用下深埋硐室围岩的流变特性,采用分级增量加载方式对泥质粉砂岩进行三轴压缩蠕变实验,根据稳态蠕变速率与应力的关系,利用给定蠕变速率阈值确定岩石的长期强度;结合蠕变曲线特征,将瞬弹性、黏弹性、黏塑性应变分离,建立模型各参数与应力和时间的函数关系;根据损伤定义确定瞬弹性、黏弹性元件的损伤变量,并引入瞬弹性、黏弹性损伤变量和黏塑性修正系数对西原模型进行优化,提出一种可以描述高应力作用下岩石蠕变全过程的变参数模型。研究结果表明:稳态蠕变速率随应力增大呈指数增大,采用给定蠕变速率阈值求得岩石的长期强度为68.82 MPa,为单轴抗压强度的74.80%;基于黏弹塑性应变分离建立的蠕变模型能够很好地描述岩石蠕变全过程的非线性特征,且优化模型与实验数据拟合较好,证明了该蠕变模型的合理性。     

天然沉积连云港软黏土的屈服特性

为了研究天然沉积结构性软黏土的屈服特性,采用大直径PVC管取样器获取连云港地区地表下2.5 m处的不扰动样,进行一维固结和应力路径三轴试验.一维固结试验结果表明, 天然沉积连云港软黏土具有较强的结构性. GDS三轴的不同应力路径试验结果表明,无论以体积变形还是剪切变形为主的应力路径下,连云港软黏土的应力应变曲线都有明显的屈服特征.根据试验各应力路径得到的屈服点,可以得到连云港软黏土的初始屈服轨迹大致呈倾斜的椭圆形状,与Nakano等人模型的屈服面比较吻合.沿各应力路径屈服后塑性应变方向与该模型屈服面法线方向的夹角在-22°～33°范围之内变化,表明屈服后塑性流动方向可简单采用相关联流动法则来描述.     

砂土速率相关黏性特性的有限元分析

根据复杂加载条件下饱和砂土排水平面应变压缩试验,分析了砂土的速率相关的黏性特性.试验发现砂土存在显著的加载速率效应、蠕变变形和应力松弛,并且在应变速率突变、蠕变或应力松弛之后,以新的应变速率重新加载时呈现出高刚度行为.针对砂土的变形强度特性提出了一种非线性有限元计算方法,砂土本构关系采用了三要素弹黏塑性本构模型.将有限元计算结果与试验结果进行比较,表明建议的有限元计算方法不仅可以较为精确地模拟砂土的平均应力-应变关系,同时也可以模拟包含变应变速率加载、蠕变加载、应力松弛加载的全过程黏塑特性.     

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．     

闭孔泡沫铝压缩力学性能的实验和三维有限元模拟

基于X射线电子计算机断层扫描技术,建立了反映闭孔泡沫铝真实结构的三维有限元模型.对闭孔泡沫铝准静态和动态压缩力学性能进行了实验和数值模拟,分析了闭孔泡沫铝的变形特性及力学性能,验证了模型的可靠性.结果表明,准静态压缩下,试件主要沿加载轴45°方向产生塑性变形.压缩速率为低速时,其变形模式与准静态相同.闭孔泡沫铝试件截面上结构薄弱处首先出现应力集中,材料达到塑性屈服.在高速压缩下,试件加载端首先达到塑性屈服.比较闭孔泡沫铝不同应变率下的屈服强度,动态压缩下的屈服强度远高于准静态压缩下的.应变率280~700 s-1下,其屈服强度变化不明显,应变率继续升高至2 000 s-1,屈服强度略微提高.      

应力路径对粉土力学特性的影响试验

应力路径是影响土体强度和变形特性的重要因素,本文利用GDSTAS全自动三轴仪对苏北地区的粉土开展常规三轴压缩、减压三轴压缩、等压压缩3种应力路径的力学特性试验。结果表明:应力路径对粉土应力-应变特性影响显著,常规三轴压缩应力路径下应力-应变特性因围压大小而不同,等压压缩应力路径和减压压缩应力路径下粉土应力-应变特性都为应变软化型,但软化程度不同;不同应力路径下粉土的应力-应变特性可采用应变软化模型和双曲线模型进行拟合,拟合结果较好;相同围压下,常规三轴压缩应力路径下粉土强度最大,轴向应变的变化速率最快,等压压缩应力路径粉土强度次之,减压压缩应力路径强度最低,轴向应变的变化速率最慢。研究结果能为工程中不同应力路径下粉土地基设计计算提供较为可靠的力学指标。     

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     

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