滚动轴承外圈局部缺陷的有限元动力学分析

以滚动轴承为研究对象,应用ABAQUS/Explicit建立外圈表面线剥落缺陷轴承和无缺陷轴承的有限元动力学分析模型.考虑载荷、转速、接触及摩擦等影响因素,研究了轴承外圈表面存在线剥落缺陷和无缺陷时的动力学响应;分析了滚动体与外圈间的接触力变化、滚动体进入和退出缺陷时的等效应力情况,根据滚道与滚动体间接触力的变化情况描述了滚动体滚过缺陷的多事件情景.结果表明:对于外圈表面存在局部缺陷的轴承和无缺陷轴承,滚动体与外圈的接触力幅值相等;缺陷轴承在缺陷进入点和退出点处,等效应力大小相等,约为无缺陷轴承等效应力值的两倍.通过分析径向载荷和转速共同作用下内圈耦合点在竖直方向上位移的变化趋势,验证了仿真模型的有效性.     

电-力耦合场下导电弹性介质的表面失稳

文章利用线性摄动理论,对扩散调控的弹性固体表面在受到单向均匀远场应力和电场的作用下进行了研究;采用线性稳定性分析得到了临界失稳波长,得出了摄动增长率随扰动波数的变化曲线;在分析过程中,考虑了弹性应变能、表面能和静电能的共同作用.分析结果表明,表面能总是抑制表面失稳,弹性应变能促进表面失稳,而静电能有利于表面失稳.表面形态的演化是由于几种能量相互竞争导致的结果,最终趋于总自由能最小.通过机械应力和电应力调控的表面自组装可以生成周期性纳米结构,从而为纳电设备的制造提供模板.     

卡套式管接头塑性松动机理分析

文章考虑棘轮效应定义的材料本构模型,采用频域积分方法得到位移载荷,对管接头塑性松动阶段的行为进行了数值模拟,并探讨了初始预紧力、侧向载荷、摩擦系数对松动的影响规律。结果表明:在轴向预紧力作用下,侧向循环载荷引起的材料棘轮效应导致结构塑性应变不断发展,引起张紧力的下降;第1圈工作螺纹承担载荷较多,等效应力和塑性应变集中于牙根部位;侧向循环载荷下,连接结构的等效应力、接触应力、塑性应变逐渐增大,同一圈螺纹不同位置的材料受拉压程度不同,应力和应变呈非线性变化;较大的侧向载荷幅值、初始预紧力、摩擦系数会加快塑性松动。     

基于累积塑性应变的表面裂纹板CTOD疲劳分析

结合Dugdale模型,以表面裂纹尖端累积塑性应变为控制参量,提出一个低周疲劳载荷下含半椭圆形表面裂纹船体板的裂纹尖端张开位移(CTOD)分析模型.利用有限元法模拟了表面裂纹尖端累积塑性变形、表面裂纹几何特性、应力均值以及材料应变硬化系数等相关因素的影响,结合最小二乘法拟合出基于表面裂纹尖端累积塑性应变的考虑表面裂纹几何特性、应力均值以及材料应变硬化系数影响的CTOD二阶多项式.     

加温过程中缺陷花岗岩的耦合损伤

为了能够正确评价温度作用下缺陷花岗岩的损伤机理,应用热力学、Maxwell应力理论,建立关于集中应力的非线性齐次微分方程,求解出花岗岩缺陷内部集中应力的表达式。采用应变等效原理,把缺陷花岗岩的受热状态分解成两种状态,即宏观缺陷的花岗岩受热状态和随机微观缺陷的花岗岩受热状态。全面分析了宏观裂纹花岗岩的受热过程中的损伤。细致研究内部微观随机性缺陷在受热作用下的损伤的耦合。推导了考虑宏、细观缺陷耦合的花岗岩复合损伤模量的计算公式。该理论推导公式可以为地热开发提供参考。     

薄壁轴向微沟槽铜管高速旋压成形数值模拟

本文利用有限元分析软件MARC对薄壁轴向微沟槽铜管钢球高速旋压成形过程进行模拟,建立了简化的1/4旋转对称模型,并采用了更新拉格朗日算法和全局网格重划分技术,成功解决了模拟过程中的网格穿透和收敛问题.对薄壁微沟槽铜管的成形特征和残余应力、等效应力应变的分布规律进行了分析.结果表明,成形过程中,金属会出现回弹效应并由此产生凹口等缺陷;等效应力应变及三向应力应变沿轴向呈层状分布,表层应力超过材料应力极限导致铜屑产生,且易出现断管现象;沟槽底部的等效应力应变和残余应力大于齿顶与外表面.过大的残余应力容易造成材料脆化,进而产生粗糙形貌.该研究对优化成形工艺参数,抑制缺陷产生有着重要意义.     

基于Oyane损伤和断裂模型的厚板精冲过程数值模拟和缺陷预测

将考虑静水应力和应变历史对材料损伤影响的Oyane损伤模型用于断裂的预测,将局部网格自适应和单元删除技术用于模拟裂纹的产生和扩展,在DEFORM-2D有限元模拟软件中建立了精冲轴对称模型,进行了弹塑性大变形有限元数值模拟.分析了成形过程中静水应力、等效应力、等效应变和损伤的分布以及发展趋势,分析了工艺参数对缺陷的影响规律,试验结果验证了模型的准确性.     

基于宏观和细观缺陷耦合的节理岩体损伤本构模型

提出考虑宏观和细观缺陷耦合的节理岩体损伤本构模型。首先介绍仅考虑微裂纹等细观缺陷影响的岩石损伤本构模型及仅考虑节理等宏观缺陷影响的岩体损伤本构模型,其次基于Lemaitre应变等效假设,推导考虑宏观和细观缺陷耦合的复合损伤变量,从而建立基于宏观和细观缺陷耦合的节理岩体损伤本构模型,最后通过引用岩石单轴压缩试验资料对模型合理性进行验证。研究结果表明:该模型能够较好地同时反映宏观和细观缺陷对岩体应力应变曲线的影响。同时采用该模型对含不同倾角的单节理岩体和含多条平行节理的岩体在单轴压缩荷载下的应力应变曲线进行分析,所得结果与相关文献中的试验及理论结果具有很好的一致性,说明了该模型的合理性。     

复合材料层合板的一种高阶理论

本文提出了一种关于复合材料层合板弯曲的高阶理论，将层合板的位移分层假设为三次函数，考虑了层间界面位移和应力的连续条件以及各层的横向剪切效应，根据内力等效建立平衡方程，导出该高阶理论的控制微分方程式。通过实验计算说明，文中提出的高阶理论具有收敛快、精度高等优点。     

自增强厚壁园筒的应力分析与优化设计

本文采用连续应力——应变折线来考虑材料的应变硬化效应,推导了厚壁园筒的弹塑性应力解和位移解,并按自增强处理压力卸除后不出现反向屈服,在工作压力作用下最大等效应力不超过许用应力的原则,对自增强厚壁园筒进行了优化设计。     

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