圆柱直齿轮超塑挤压成形中金属流动的模拟试验

针对圆柱直齿轮冷挤成形时材料变形抗力大、金属流动性差等不足，用Pb-Sn共晶合金对圆柱直齿轮超塑性挤压进行了模拟试验研究。试验表明用超塑挤压的方法加工圆柱直齿轮是可行的，且能降低成形载荷、改善金属的流动性与型腔尖角填充能力。     

基于DEFORM的汽车半轴套管模具结构优化

采用体积成形有限元分析软件DEFORM对半轴套管的一次热挤压成形过程进行了模拟,分析了成形过程中金属的流动情况,得出了凹模开裂的原因为圆角结构过小导致应力开裂的结论,对凹模结构进行了优化,优化后的结构不仅能有效地避免凹模开裂,而且更利于坯料成形和减小挤压力.     

基于响应面法的直齿轮冷挤压工艺多目标优化

针对某型大模数行星直齿轮在精锻成形工艺中成形载荷大、齿形塌角大及弹性回复影响齿形精度等问题,提出一种新型约束分流正冷挤压工艺.以降低成形载荷、减小轴向塌角长度及取得弹性回复量较小的齿轮为优化目标,以凹模入模角、毛坯直径系数、摩擦系数和模具挤压速度为优化变量,借助正交实验设计与Design-Expert V8软件进行响应面拟合建模分析,得到成形载荷及塌角长度的二阶响应面模型和弹性回复的线性模型,同时借助该软件进行多目标优化,得到最佳工艺参数组合,即入模角为67°,直径系数为1.15,摩擦系数为0.06,模具下压速度为52mm/s.有限元模拟和生产实践结果表明:优化后的工艺参数组合能生产得到弹性回复较小、表面质量好的行星直齿轮冷挤压件,并能有效减小塌角、降低成形载荷.     

提高汽车轮胎螺母冷挤模具寿命的研究

本文采用有限元法对正挤压凹模的应力状况进行了分析计算,根据计算结果,对BJ130汽车轮胎螺母终成形凹模进行了改进设计.实践证明,使用改进后的凹模结构,可使模具寿命提高五倍以上.     

圆柱直齿轮冷锻成形工艺研究

本文针对直齿轮冷锻过程中齿腔充填困难、成形载荷大、模具寿命低的特点,采用轴分流和浮动凹模耦合工艺成形。利用有限元软件DEFORM-3D对该工艺进行数值模拟。对工艺成形过程中等效应力,等效应变、速度场、成形载荷等规律进行了分析。结果表明：该成形工艺可以有效的成形出齿形良好的齿轮,为此类齿轮冷锻工艺的应用与生产实践提供了理论依据。     

圆柱直齿轮精密塑性成形数值模拟研究

利用三维造型软件Unigraphics NX对圆柱直齿轮进行参数化建模,采用分流孔分流和浮动凹模耦合工艺成形,使用有限元数值模拟软件Deform-3D对冷锻成形过程进行三维刚塑性有限元数值模拟,确定最佳匹配的工艺参数组合.以此优化成形工艺,为成形研究提供了参考.     

圆柱斜齿轮闭式温锻数值模拟

采用闭式温锻成形工艺方案成形圆柱斜齿轮,相对于传统切削工艺,可以降低能耗提高工效.依据圆柱斜齿轮几何结构,设计出合理模具工装;将凹模设计成轴承式凹模,当锻件顶出时,凹模自动沿轴向自转,锻件被旋出凹模;采用三维刚粘塑性有限元法对其成形进行数值模拟分析,得到成形过程中的等效应力、应变分布图以及载荷-行程曲线图;模拟结果表明,坯料向齿腔充填时,齿根处等效应力、等效应变值较大;最后充填阶段,齿顶处等效应力、等效应变值较大,载荷也出现陡增现象.     

分流挤压直齿轮成形工艺研究

分析了直齿轮在冷挤压精密成形过程中成形压力过大的特点,采用分流挤压二次成形工艺以降低成形力。运用UG建立直齿轮挤压几何模型,Qform2D/3D锻造模拟软件对齿轮冷挤压分流成形工艺进行模拟分析。通过模拟分析结果,确定了合理的成形方案,实践证明该工艺能有效地降低成形压力,保证轮齿填充饱满,提高模具寿命。     

直齿轮的精密挤压成形工艺研究

金属塑性成形技术是一种先进的制造技术。其优势较传统的制造技术十分明显。在本文中，对直齿轮的塑性成形技术进行了研究。重点分析了直齿圆柱齿轮的精密塑性挤压新工艺，即分流成形原理及精密成形加工方法。     

弧齿锥齿轮成形工艺及模具设计

针对弧齿锥齿轮开式模具存在的问题,提出了弧齿锥齿轮闭式挤压新工艺及其模具结构。该模具采用浮动凹模和浮动凸模结构,工件在2个凹模和2个凸模形成的封闭模腔中成形,生产的工件无飞边。工艺试验表明,新工艺可显著降低挤压变形力、材料消耗和生产成本,提高模具寿命和生产效率。     

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     

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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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has