等离子熔射成形模拟系统设计与研究

设计并开发了一种等离子熔射成形过程的数值模拟系统.系统描述了从射流至基体的整个熔射成形过程以及各对象的状态和行为,并生成熔射成形过程的三维动画.在分析中同时考虑射流、熔射粒子、皮膜的影响因子对熔射结果的影响,找出部分主要工艺参数对熔射的影响规律.由等离子熔射铁片模拟所得到的计算结果与实验观测现象基本符合,表明了此系统用于系统地模拟和分析等离子熔射成形过程是可行的.     

等离子熔射快速制模中皮膜形成过程的模拟

等离子熔射性速制模法可以由快速原型或天然素材原型快速复制硬质合金模具，而控制等离子熔射成形工艺，保证熔射皮膜的质量是该技术的关键，建立了包括等离子发生过程，粒子在射流中飞行及加热，熔射层的生长及孔隙形成三阶段的熔射皮膜生长过程的数学模型，进行了数值模拟计算，并通过实验验证了有关数学模型与模拟计算方法的正确性，熔射皮膜形成过程模拟软件的开发将为等离子熔射快速制模工艺的合理设计提供科学工具。     

均匀化分析扫描路径对熔射皮膜热应力的影响

基于均匀化方法，建立了宏细观连成热应力场计算数学模型，用有限元法计算模拟了等离子熔射快速成膜过程皮膜热应力场，对四种不同喷枪扫描路径下熔射成形皮膜冷却过程热应力场进行了分析。结果表明：采用回形向外扫描模式，皮膜中的等效热应力峰值最小；线性扫描情况下长折线处的应力比短折线处的应力高。在实际喷枪扫描路径的设计和选择中，应尽可能地选择回形向外的扫描模式，同时使组成扫描折线的线段应尽量取短些，以利于降低涂层中的峰值应力。     

喷枪运动速率对熔射皮膜温度影响的分析

采用基于匀质化理论的宏细观连成温度场计算数学模型，模拟了等离子熔射过程中皮膜生长过程及其温度场，并采用不同的喷枪运动速率研究其对熔射中皮膜生长过程温度场的影响，以期得到合理的喷枪运动速率和改善皮膜质量．     

精细饰纹件等离子熔射快速制造技术研究

提出了精细饰纹件等离子熔射快速制造技术．在大量实验基础上，着重研究精细饰纹熔射成形及后处理过程中的关键技术问题，详细分析和评价了基模特性、射流特性、粉末特性、熔射枪结构、熔射工艺参数等重要因素对熔射成形件质量的影响，给出了射流图像采集方法、粉末飞行速度和温度的数值模拟模型及测量技术方案，最后进行了典型精细饰纹件的熔射成形实验．研究结果表明：等离子熔射成形技术可以快速制造精细饰纹件，实现成形与加工一体化，且工艺简单、成本低，是极具发展潜力的制造方法．     

金属三维塑性成形过程无网格伽辽金法数值模拟技术

将无网格伽辽金法(EFGM)与三维刚(粘)塑性流动理论相结合,对EFGM在金属三维塑性成形过程数值模拟中的应用技术进行了研究.分别采用边界奇异权法和修正的罚函数法处理速度边界条件和体积不可压缩条件,采用反正切摩擦模型处理摩擦边界条件,推导了金属三维塑性成形过程EFGM法数值模拟的刚度方程,给出了关键算法.对长方体金属镦粗过程进行了数值模拟,并将数值结果与三维刚塑性有限元体积成形商品软件Deform3D计算结果作了比较.发现两者吻合良好,表明了本文方法的正确性和有效性.     

基于熔滴多维统计的熔射涂层孔隙率模拟

熔射成形涂层的微观结构,如孔隙的大小、形状、分布和涂层的表面粗糙度等,影响涂层的机械性能和物理性能,进而影响成形零件的使用性能.为方便研究熔射涂层成形过程以及成形工艺参数对涂层孔隙率的影响,本文以镍铝合金为例,依据熔滴薄片照片反映的形状特点生成数字化熔滴薄片,并结合熔滴时间和空间的多维统计特征模拟了熔射成形涂层的孔隙率.模拟涂层孔隙率为6.13％,与参考文献中相同条件下的实验结果5.7％比较接近.研究结果对熔射成形模具和零件的涂层质量控制具有参考意义.     

中厚板分段多点成形及其数值模拟

为了解决分段多点成形过程中的技术难题,利用数值模拟软件对其成形过程进行数值模拟.以显式算法模拟加载成形过程,隐式算法模拟卸载回弹过程,从而实现分段多点成形的数值模拟.采用非均匀有理B(NURBS)样条曲线设计过渡区形状,探讨了过渡区大小对成形品质的影响.结果表明,在合理设计过渡区的情况下,分段成形品质好于一次成形.     

不锈钢模具快速制造技术

为了解决低熔点材料电弧熔射成形模具使用性能差、寿命低等问题,提出电弧熔射成形制作不锈钢模具的方法.以不锈钢材料为研究对象,研究电弧熔射过程中输入参数对飞行熔滴温度和速度的影响,分析熔滴的扁平化过程,并对熔射层的硬度和孔隙率进行测试.实验结果分析表明,雾化气体压力直接影响熔滴的雾化状态,熔滴飞行温度、速度,以及成形质量.随着空气压力的增大,熔滴飞行速度提高,熔射层致密且氧化物质量分数减少,气孔率降低,显微硬度也大大提高.熔射模的预热温度直接影响着熔滴的扁平化状态,从而影响熔射成形质量.     

增量法在金属塑性成形有限元分析中的应用

有限元法是一种有效的数值计算方法，已经被广泛应用于金属成形过程的数值模拟中，由于金属塑性成形多是大变形且一般都是非线性的，所以需要运用增量理论来进行分析。本文论述了增量法在金属塑性成形有限元分析中应用的原理及方法，以Marc软件为平台，介绍了增量法在金属塑性成形有限元数值模拟中的应用。     

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

正~~     

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