基于弧长法的南瓜型超压气球非线性后屈曲分析

稳定性研究是南瓜型超压气球设计面临的重要课题。针对南瓜球非线性屈曲过程,对含初始缺陷南瓜球的稳定性进行研究。首先,对南瓜球进行特征值屈曲分析,得到前8阶屈曲模态及线性屈曲临界载荷。然后,基于特征值分析的模态构型给出初始缺陷分布,进一步利用非线性有限元中的弧长法分别计算临界缺陷模态和组合缺陷模态下对应的屈曲临界载荷。结果表明,南瓜球对初始缺陷较敏感,缺陷的幅值和分布形式对承压能力和失稳形态均有影响,承压能力随缺陷幅值增大而降低,说明提高南瓜球稳定性需要提高气球的加工精度。同时,对已失稳南瓜球的应力分布进行分析,发现失稳状态下南瓜球高应力区的应力水平远高于相同载荷下未失稳南瓜球的应力水平。可见,失稳现象极大降低了气球的承压能力。     

基于流体力学方法的液化后砂土流滑推桩效应

采用计算流体动力学(CFD)中的流体体积(VOF)方法和固体力学中的有限元法,对液化后砂土流滑的推桩效应进行研究.将液化后砂土分别视为牛顿流体和剪切稀化非牛顿流体,将单桩视为线弹性结构,分析了牛顿流体黏度、非牛顿流体稠度系数和流动指数对推桩效应的影响.研究结果表明:将液化后砂土视为牛顿流体,则距离桩顶越近,桩身位移越大,距离桩底越近,桩身应力就越大;随着液化后砂土黏度的增大,桩身位移和应力也越大,曲线间差距则越来越小;将液化后砂土视为剪切稀化流体,沿桩身的响应规律与牛顿流体一致;稠度系数和流动指数的变化只会影响桩身位移和应力数值的变化,对变形方式不会产生影响.     

桅杆天线基座整体提升施工风稳定性分析

对桅杆结构风载作用下静力整体稳定进行非线性分析,研究桅杆天线基座整体提升施工的风稳定性.基于桅杆结构的非线性平衡方程,应用ANSYS软件进行结构分析.采用特征值屈曲方法求得桅杆失稳载荷的数值解上限后,以此作为非线性屈曲分析的给定载荷,在渐进加载达到此载荷前,求得非线性失稳临界解,即该基座整体提升时的稳定安全系数,及其后屈曲路径.     

冷轧带钢板形屈曲变形失稳限的有限元分析

采用ANSYS有限元仿真分析方法研究冷轧宽带钢板形屈曲失稳特性。利用ANSYS的几何非线性求解模块,建立宽薄带钢二维有限元模型,分析不同形式载荷、厚宽比和张应变下的屈曲失稳过程,计算板形屈曲变形失稳限。分析结果表明:边中复合浪的临界失稳载荷最大,中浪的较大,边浪的最小;边中复合浪的屈曲半波长为板宽的50%～60%,中浪与单边浪为80%左右,对称双边浪约为70%;在同样载荷下,随着厚宽比或张应变的增加,临界失稳限呈增长趋势,并且复杂浪形的临界失稳限增长速度明显大于简单浪形的增长速度。     

风载作用下高空贝雷架支撑系统的稳定性分析

风载荷对超高大跨重荷混凝土支撑体系安全施工的影响不容忽视,以三峡升船机为例,研究升船机塔柱顶部横梁施工过程中风载对贝雷架支撑系统结构稳定性的影响.通过有限元数值方法对贝雷架支撑系统进行屈曲分析,得到贝雷架支撑系统的失稳模态和临界载荷,并对比线性屈曲和非线性屈曲的计算结果,研究几何非线性对贝雷架支撑系统稳定性的影响.计算结果表明:在风载作用下,下层贝雷架支座附近背风侧腹杆容易发生局部杆件失稳,且考虑初始缺陷的几何非线性对贝雷架支撑体系稳定性的影响比较明显.     

板架屈曲临界应力的敏感性系数

采用有限元法计算平面板架屈曲的临界应力和失稳波形，推导出临界应力对结构几何参数和物理参数的敏感性系数计算的一般公式．临界应力及其敏感性系数计算均考虑金属材料的物理非线性．采用切线模数理论对受压构件的弹性模数进行修正．本文结果主要用于板架结构稳定的可靠性分析     

特大型起重桅杆吊装过程的稳定性数值模拟分析

高度为64m和80m的特大型起重桅杆在直立吊装过程中承载较大的轴向载荷,在正式投入使用前,必须分析、校核桅杆在立态起吊时的整体强度和稳定性,以确保吊装过程安全。采用有限元数值模拟方法,分别计算了这两种特大型起重桅杆在顶端钢丝绳斜拉条件下桅杆吊重的线弹性屈曲临界载荷。同时考虑该大型桅杆在起吊时具有较大位移,用非线性有限元法计算了桅杆处于几何非线性状态的最大载荷及最大应力。结果表明,有限元大变形解的桅杆主肢最大工作应力值小于桅杆主肢材料的许用应力,桅杆即使处于几何非线性状态仍满足强度设计条件。设计桅杆的限定最大吊重载荷小于按有限元线性解与非线性解两种状态计算得出的桅杆结构的临界载荷,该桅杆结构满足强度与稳定设计要求,吊装过程中不会发生失稳破坏。     

特大型起重桅杆吊装过程的稳定性数值模拟分析

高度为64m和80m的特大型起重桅杆在直立吊装过程中承载较大的轴向载荷，在正式投入使用前，必须分析、校核桅杆在立态起吊时的整体强度和稳定性，以确保吊装过程安全。采用有限元数值模拟方法，分别计算了这两种特大型起重桅杆在顶端钢丝绳斜拉条件下桅杆吊重的线弹性屈曲临界载荷。同时考虑该大型桅杆在起吊时具有较大位移，用非线性有限元法计算了桅杆处于几何非线性状态的最大载荷及最大应力。结果表明，有限元大变形解的桅杆主肢最大工作应力值小于桅杆主肢材料的许用应力，桅杆即使处于几何非线性状态仍满足强度设计条件。设计桅杆的限定最大吊重载荷小于按有限元线性解与非线性解两种状态计算得出的桅杆结构的临界载荷，该桅杆结构满足强度与稳定设计要求，吊装过程中不会发生失稳破坏。     

卧式埋地储罐稳定性研究

埋地卧式储罐受力条件复杂,其应力和变形较难计算。根据储罐实际受力特点,建立储罐稳定性的有限元计算模型。采用非线性径向力和切向力描述给定埋深储罐的覆土压力,利用ANSYS软件对储罐模型进行屈曲分析。将屈曲特征值作为储罐埋深迭代系数,计算新的储罐埋深,重新进行屈曲分析。结果表明:新储罐失稳临界埋深计算方法可用于对储罐模型进行屈曲分析,多次迭代后屈曲特征值接近1,此时对应的埋深即储罐失稳临界埋深。在储罐结构上设置加强圈可大幅提升埋地储罐的稳定性,为储罐埋深设计提供充足的安全裕量。     

用非线性方法校核供料线塔柱的稳定性

利用Ansys5.5软件,先用特征值屈曲方法求得供线塔柱失稳载荷的数值解上限,然后以该上限作为非线性屈曲分析的给定载荷施加给供料线塔柱,在渐进加载达到此载荷前,求得截柱非线性失稳临界解,同时给出载荷位移曲线。     

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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