国产结构用铝合金高温力学性能试验研究

为了研究铝合金材料在高温下的力学性能,完成了国产结构用铝合金6082-T6、6N01-T6、6061-T4和6061-T6的高温下恒温加载试验.试验测得了4种牌号铝合金在不同温度下(20~300℃)的力学性能,包括名义屈服强度、极限强度和延伸率等力学性能指标.然而在试验中发现高温下材料应变难以准确测量,因此未能获得各牌号铝合金高温下的弹性模量.将试验数据进行拟合,得到了4种牌号铝合金力学性能指标高温折减系数的计算式,为铝合金结构的抗火性能研究打下基础.此外,还将所得到的折减系数计算式与欧洲规范和美国规范中的建议值进行对比,结果表明规范建议值均偏安全,其中美国规范最为保守.     

双层铝合金板式节点力学性能与设计方法

板式节点是铝合金空间网格结构中应用最为广泛的节点形式,其力学性能会对铝合金空间网格结构的承载性能产生显著影响.目前,针对铝合金板式节点力学性能的研究主要集中在单层板式节点,双层板式节点作为一种新型节点形式,其力学性能及设计方法尚待研究.本文在试验的基础上,分别对单层和双层板式节点的力学性能进行了数值分析和理论分析,并运用ABAQUS软件建立了大量节点模型进行参数化分析,考虑了腹板厚度、腹板高度、节点板厚度、翼缘板厚度、翼缘板宽度及螺栓布置形式对单层和双层板式节点力学性能的影响.基于破坏线理论和螺栓破坏理论,引入材料等效强度破坏系数和双层铝合金板式节点极限承载力增强系数,提出了节点极限承载力的计算方法.研究结果表明:单层和双层板式节点的极限承载力随着节点板厚度的增加,先增大后减小;腹板越厚越高、翼缘板越厚越宽,单层和双层板式节点的极限承载力越高;双层板式节点极限承载力高于单层板式节点,根据计算分析建议双层板式节点极限承载力增强系数取2.3;螺栓布置对节点力学性能影响显著;理论计算结果与数值计算结果吻合程度较好,验证了理论计算方法的准确性,可为实际工程应用提供依据.     

国产结构用铝合金低温力学性能试验研究

为弥补目前国内外对结构用铝合金低温力学性能试验研究的不足,完成了国产结构用铝合金6082-T6、6N01-T6、6061-T6和6061-T4的低温恒温加载试验.试验测得4种牌号铝合金在-120～20℃下的抗拉极限强度、名义屈服强度、延伸率和断面收缩率等力学性能指标.试验结果表明,低温下铝合金会出现加工硬化现象,其抗拉极限强度和名义屈服强度均有所增加,但断后延伸率以及断面收缩率的变化规律不明显.通过试验数据拟合,得到4种牌号铝合金力学性能指标的低温提高系数的计算式.最后,将提高系数计算式与美国规范建议值进行比较,结果表明美国规范较为保守.     

节点刚度对铝合金板式节点网壳稳定性能的影响

本文提出了考虑铝合金板式节点半刚性的杆件单元力学模型,建立了考虑铝合金板式节点试验弯矩-转角曲线关系的网壳结构数值模型,并通过数值算例进行验证.数值计算结果表明,铝合金板式节点半刚性特性显著降低了网壳结构的承载力.进一步的参数分析表明,结构跨度对网壳稳定承载力的影响最大,荷载分布模式和支撑条件对网壳稳定承载力的影响较小.     

国产6061-T6铝合金的修正塑性本构模型

铝合金材料已广泛地应用于各种工程结构中。能准确描述铝合金在复杂应力状态下的塑性本构关系,对铝合金结构在复杂工况下的分析和设计具有重要意义。传统的von Mises屈服准则忽略了应力状态对金属塑性的影响,并不适用于复杂应力状态下的铝合金材料。通过试验证明了应力三轴度和Lode角均会对6061-T6铝合金的塑性行为产生影响,并在此基础上提出了适用于国产6061-T6铝合金在复杂应力状态下的塑性本构模型,并校准了全过程硬化规律和新屈服准则。通过试验和数值结果对比可知,该塑性本构模型可以精确地模拟国产6061-T6铝合金在复杂应力状态下的弹塑性行为。     

铝合金板式节点承载力设计方法及构造要求

对铝合金板式节点的承载力进行理论分析,提出了节点板块状拉剪破坏的承载力计算公式以及节点板局部屈曲承载力的计算公式.在试验的基础上,利用ABAQUS软件对铝合金板式节点进行数值模拟研究,数值分析结果和试验结果吻合较好.根据试验结果拟合得到了节点承载力公式中的系数.将承载力计算公式和试验结果进行了对比,验证了公式的实用性.最后提出铝合金板式节点的实用构造要求,并通过试验结果验证了其正确性.     

点支式玻璃建筑中铸铝支承件承载性能

为了研究点支式玻璃建筑中铸铝支承件的承载性能,对3种典型铸铝支承件进行了足尺模型试验研究。按照实际工程中支承件的形式与尺寸制造模具,采用ZL105-T1和ZL111-T6这种铝合金材料铸造成足尺模型试件,借助万能试验机对试件进行加载试验,得出了试件的屈服荷载与极限荷载。根据试件的实际几何尺寸与材料属性,建立有限元模型对试验过程进行数值模拟。有限元分析结果与试验数据吻合良好,验证了有限元模型的可靠性。试验研究与有限元分析表明铸铝支承件的承载力较高,可以在实际工程中应用。     

7075-T6高强铝合金轴心受压构件局部稳定试验研究

为研究结构工程中高强铝合金轴心受力构件的局部稳定性能,对7个7075-T6铝合金H型截面短柱开展了轴心受压试验,测量了7075-T6铝合金的材料力学性能和试件的局部几何初始缺陷,分析了试件的破坏形态、局部屈曲承载力、极限承载力.试验结果表明,7075-T6铝合金材料平均名义屈服强度达到536 MPa;试件翼缘与腹板的平...     

国产结构用铝合金断裂韧性参数校准

为了将空穴增长模型(VGM)和应力修正临界应变模型(SMCS)应用于国产结构用铝合金的韧性断裂预测,完成了国产6061-T6、6082-T6和7020-T6 3种牌号的铝合金标准圆棒试件和缺口圆棒试件的单轴拉伸试验,并结合有限元分析,校准了3种牌号铝合金的VGM和SMCS模型断裂韧性参数.研究结果表明:槽口半径大小对各牌号铝合金试件的断裂韧性参数校准值影响较小,离散系数均在20%以内;断裂韧性参数是铝合金材料固有属性,可用于国产结构用铝合金在不同应力状态下的韧性断裂预测;与SMCS模型相比,VGM模型能够更为精确地预测铝合金材料的韧性断裂.     

铝合金板式节点受弯承载力试验研究

从理论上提出了铝合金板式节点在面外弯矩作用下的抗弯承载力计算公式.进行了4个铝合金板式节点试件试验,其中3个试件只承受面外弯矩,一个试件同时承受面外弯矩和剪力,得到了板式节点的受力性能,归纳了板式节点在面外弯矩作用下和弯剪联合作用下的破坏模式主要为:杆件受弯破坏、节点板块状拉剪破坏和节点板的屈曲破坏.通过试验数据分析,得出了反应撬力对其极限承载力影响的折减系数k1的取值范围,并验证了承载力计算公式的准确性.针对4个板式节点试件的试验,采用ABAQUS有限元软件建立了有限元数值分析模型,分析了其极限承载力,补充和完善了试验研究.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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