基于虚拟样机的数控铣床结构动态特性分析

为了对数控铣床结构进行优化设计,运用系统建模与仿真以及虚拟样机技术,分别在Pro/E、ADAMS和ANSYS平台上建立数控铣床的三维模型和立柱有限元模型,进行了数控铣床的运动仿真和立柱的模态分析,得到立柱前20阶频率.通过对变形云图的分析,确定电机主轴的转速不宜大于12000r/min.     

数控机床仿真环境的建立及应用

利用VERICUT软件,在PC机上建立了XKA714B/E数控床身铣床的几何模型和控制系统模型,并进行了机床参数设置,在计算机上得到了XKA714B/E数控铣床的虚拟加工环境,建立了数控铣床常用刀具库。用户通过设置毛坯,调用加工程序,即可在计算机上观看到和真实机床完全一致的加工过程,系统可以纪录仿真加工中出现的问题,检查过切、欠切、干涉等问题,并能对加工后的零件与设计实体进行比照,以便用户对数控程序进行修改和对刀具轨迹进行优化。该仿真系统既可以用于初学者有针对性地进行编程训练,也可以用于实际加工中代替试切进行程序校验。     

一种数控滚齿机工作台动态特性建模方法及实验分析

为了研究数控滚齿加工中滚刀轴转速波动引起的工件轴速度波动的动态响应特性,对数控滚齿机旋转工作台即工件轴的伺服控制问题进行了分析。首先根据电机学原理和机械动力学原理对伺服控制系统组成的各个环节进行了建模和分析,推导出旋转工作台的整体伺服控制系统模型,并考虑到伺服控制环节在动态响应过程中的摩擦因素,引入了非线性Stribeck黏性摩擦结构;然后利用Simulink建立了滚齿机旋转工作台的伺服系统仿真模型,并研究了不同的位置和速度指令频率变化对工件轴伺服动态响应影响效果;最后通过数控滚齿机工作台控制实验来验证工件轴的动态响应特性。仿真结果表明:旋转工作台伺服系统在低速运行时,位置跟踪存在"平顶"现象,速度跟踪存在"死区"现象;旋转工作台伺服系统位置和速度的跟随率随着指令频率的增大而减小,当指令频率增大到31Hz时,速度跟随率不足10%。在和仿真相同的指令频率变化条件下,进行滚齿机工件轴的转速控制实验,工件轴的响应曲线与仿真响应曲线基本吻合,验证了模型的有效性和可靠性。该模型可为数控回转工作台伺服进给系统设计、伺服控制方法研究及故障诊断等工作提供理论依据。     

数控钻铣床控制系统分析

文中介绍了一种基于PLC(可编程控制器)的数控钻铣床控制系统,该系统利用PLC丰富的脉冲控制指令实现对数控钻铣床各轴的步进电机的速度和位置控制,数控加工指令由PC机经串口通信传送给PLC,控制PLC的脉冲控制指令参数,实现加工控制.PLC应用在数控铣床后,使电气控制系统的硬件电路得到了简化,便于安装调试和维护,提高了电气控制系统的可靠性.     

TDZ110A自动镗铣床控制系统研究

目的结合PLC与触摸屏,对TDZ110A普通镗铣床进行控制改进,实现镗铣床数控化.方法利用PPI协议实现了两个PLC之间的通讯、触摸屏与PLC之间的通讯,并采用自由口通讯实现STM32F103VX微处理器控制板与PLC之间的通讯,从而完成整个镗铣床控制系统的通讯.结果采用PPI协议与自由口通讯实现比较复杂的网络之间的通讯,大大简化了控制系统,使镗铣床控制系统更加先进可靠,镗铣床的控制精度达到0.001 mm,加工精度达到30~40μm.结论 PLC、交流伺服驱动系统以及触摸屏构成TDZ110A镗铣床控制系统,保证了网络之间通讯的可靠性.改进设计后的自动镗铣床提高了镗铣床加工的可靠性、加工效率和自动化能力,使该设备的性价比大幅度提高.     

微型三坐标数控铣床的设计

为了提高高校及职业技术学校中相关专业的数控教学和工人的数控培训水平,解决使用大型数控机床价格昂贵问题,设计了教学实验型微型数控铣床.借助于Solidworks和Protel等软件对数控铣床的整体结构和控制系统进行了设计,此设计满足了普通数控教学和培训的需求.     

基于LabVIEW的数控铣床螺旋插补算法

采用螺旋插补算法控制刀具的运动轨迹以实现加工工件的螺旋形状,并运用LabVIEW软件对算法进行了仿真.结果表明,该插补算法能够在数控铣床中实现,并能够插补出高精度的螺旋线,满足数控铣床插补实时性的要求.     

基于XNA的虚拟数控铣床仿真系统

为解决数控铣床加工过程的仿真实现问题, 基于虚拟制造和计算机仿真的基本思想, 以Microsoft Visual Studio 2008为开发平台, 利用C#、 XNA(Windows Xbox Next Generation Architecture)和3ds MAX为开发工具, 实现了虚拟数控铣床仿真系统。通过实验证明, 该系统能准确模拟真实数控铣床在不同转速、NC(Numerical Control)代码等条件下的各种操作与运动。用户能通过使用本系统, 达到对数控铣床操作与编程的学习、 训练等初步体验, 有助于节省使用真正数控铣床的时间, 降低学习、 培训费用。     

PCB数控钻床工作台部分的动力学仿真与分析

以六钻头龙门式PCB数控钻床工作台部分为研究对象,应用SolidWorks软件建立其三维模型,通过ADAMS软件建立工作台部分的刚柔混合模型并进行仿真分析,发现了工作台支撑板对系统的动态特性影响较大.因此,要提高工作台部分运动过程中的定位精度,有效的方法是对支撑板进行拓扑优化,利用ANSYS软件的拓扑优化模块,在保证刚度的基础上,尽可能减少其质量,改进原有的支撑板结构,提高工作台进给系统的动态特性.     

基于VB数控铣削仿真系统的实现

以VB语言为开发平台,利用计算机的高速度、大存储、较强的图形功能,开发了数控铣削仿真系统,并对其数控程序进行了图形仿真验证,检验了数控程序和加工方法的正确性.调试结果表明,该系统能采用仿真的图形检查铣削刀具路径,动态模拟数控加工的全过程,不仅避免了干涉碰撞的发生,而且能节约数控加工仿真过程中大量的财力和时间,产生较好的经济效益;该系统界面友好,使用方便,交互性好,实现了数控铣床编程与仿真加工.     

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.     

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