超声珩磨加工技术中振动系统的试验研究

论述了超声波振动珩磨振动系统的原理,从变幅杆、弯曲振动圆盘、振子系统等方面进行了详细的介绍.作者采用试验的方法,分析研究了他们对谐振频率影响的变化规律,并通过振动试验分析了振动系统中的变幅杆、弯曲振动圆盘、振动子系统的振动效果,为今后研制、开发和推广超声珩磨装置提供了依据.     

珩磨参数对Al2O3工程陶瓷材料去除率的影响

分别研究了珩磨工艺参数和工具参数对陶瓷材料95Al2O3去除率的影响，增大往复速度和圆周速度，可提高工程陶瓷的珩磨材料去除率。应用金属结合剂金刚石油石，选择较大的珩磨压力，可提高陶瓷材料去除率。电镀金刚石油石适于工程陶瓷的高效珩磨。研究结果给出工程陶瓷材料珩磨参数的选择方法。     

应用于螺旋锥齿轮热后精加工的珩齿技术研究

分析了基于交错轴传动的珩齿原理，导出珩磨轮与被珩齿轮在啮合点处的相对滑动速度的数学模型，根据该数学模型可以判定珩磨轮的节锥面是由珩磨轮齿数、公法线和与珩磨轮轴线平行的平面夹角所确定．在建立的珩磨轮齿面准均布网格点上，采用法线投影法计算各点的极限拨模导程，并通过比较凸齿面上最小拔模导程的最大值和凹齿面上最大拔模导程的最小值来判定是否存在拔模干涉．针对出现的拨模干涉，提出了拨模导程的优化方法，以及干涉的修正方案和齿面光顺过程．给出的珩磨轮设计的部分计算实例表明，珩齿技术可以在工业精加工方面得到广泛应用．     

螺旋锥齿轮珩齿技术的研究与珩磨轮的优化设计

提出了用于珩磨螺旋锥齿轮的非正交珩磨轮节锥面的设计方法，通过调整节锥面切点到珩磨轮轴线的距离，保证了节锥面之间的相对速度恰好沿着齿长方向，通过对诱导法曲率和珩磨轮上与齿面有效工作区对应点到珩磨轮面锥的距离的计算，保证了齿面上的有效工作区域全部落在啮合界限以内．构造了珩磨轮优化设计的目标函数，提出了基于珩磨轮齿数以及节锥面公法线和与珩磨轮及被珩磨齿轮的轴线平行的平面的夹角的珩磨轮双参数优化方法，并给出了计算实例，计算实例表明，本文给出的珩磨轮优化设计方法可以满足工业需求.     

国产珩磨机技术改造的新途径：超声波振动珩磨

随着机动车辆的日益增加,对缸体或缸套的珩磨质量提出了更高的要求,目前国内大中型企业多数是引进国外生产线及珩磨机来提高其珩磨质量,对于有些中小企业无力购买昂贵的国外珩磨设备,普遍存在着在国产珩磨机上用碳化硅等普通油石珩磨效率低、精度不稳定等问题,达不到技术要求。如用金刚石、立方氮化阴等超硬磨料油石,又很难解决油石堵塞及划缸现象。采用超声波振动珩磨能很好地解决这些问题,它与普通仅磨相比具有珩磨力小、珩磨温度低、精度高、表面质量高及油石磨损小、效益高等特点。1超声珩磨概述超声振动珩磨是超声振动切削在珩…     

外圆珩磨头设计及不同工况的有限元分析

设计一种自动外圆精密加工的珩磨头,通过控制工件自动回转、油石往复运动实现对阀芯外圆自动珩磨.通过仿真建模,分析匀速运动和换向阶段两种工况条件下珩磨头应力及变形分布,并找出珩磨头内刚度变形较大从而影响珩磨加工质量的因素,以及两种工况条件对珩磨头静态分析和加工精度的影响,旨在为珩磨头优化设计提供可靠依据.     

超声珩磨区考虑煤油蒸气冷凝与蒸发的空化泡动力学分析

为了更深入地探究超声珩磨区空化泡的动力学特性,以煤油为磨削液介质,考虑煤油蒸气的冷凝与蒸发建立了功率超声珩磨下的单空化泡动力学模型。利用4阶龙格库塔法对不同工作条件(珩磨压力、珩磨头回转速度和往复速度、磨削液黏性、超声频率)下的空化泡泡壁运动规律进行了数值模拟与分析。研究表明:较高的珩磨压力、珩磨液黏性以及超声频率会抑制珩磨区空化效应的产生,而珩磨头回转速度与往复速度的变化对空化效果影响极其有限。     

珩磨油石的磨削性能和磨削机理

珩磨加工过程中珩磨油石对加工效率和表面质量的影响至关重要.通过试验对比了国产与进口的氧化铝油石在粗珩阶段的磨削性能,利用扫描电镜观察了油石在加工前后的表面微观形貌,指出油石中磨粒及气孔等因素对油石的磨削能力有较大影响.在揭示珩磨油石的磨削性能和磨损机理的基础上,为优化珩磨油石的加工性能提供了理论与实验的依据.     

超声珩磨区考虑煤油蒸汽冷凝与蒸发的空化泡动力学分析

为了更深入地探究超声珩磨区空化泡的动力学特性,以煤油为磨削液介质,考虑煤油蒸汽的冷凝与蒸发建立了功率超声珩磨下的单空化泡动力学模型。利用4阶龙格库塔法对不同工作条件(珩磨压力、珩磨头回转速度和往复速度、磨削液粘性、超声频率)下的空化泡泡壁运动规律进行了数值模拟与分析。研究表明：较高的珩磨压力、珩磨液粘性以及超声频率会抑制珩磨区空化效应的产生,而珩磨头回转速度与往复速度的变化对空化效果影响极其有限。     

蜗轮高效珩磨的研究

通过我们与重庆机床厂共同进行的试验研究,在比较各种蜗轮轮齿终加工工艺路线以及研究珩磨速度与制动力矩对蜗轮珩磨效果影响的基础上,本文提出了蜗轮珩磨的新工艺——蜗轮高效珩磨工艺。这种工艺采用较大的珩磨速度和较大的制动力矩,既提高了生产率,又保证了高精度。同时,对某些实验结果作了理论分析与探讨。     

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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