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.     

用电子计算机编制超声变幅杆设计用表

变幅杆是超声波振动装置的关键元件之一,其设计计算比较复杂,特别是要解一系列超越方程,使计算更显困难。但定义三个新系数并经适当变换后,可使其计算公式和方程变成只含一个自变量,因而可用电子计算机编制设计用表,使设计计算十分简便准确。本文第(一)部分介绍最常用的简单指数型、圆锥型、悬链线型和等长圆柱的阶梯型半波谐振变幅杆公式和方程的变换方法、利用电子计算机计算的顺序方框图和设计用表的使用举例。含指数型、圆锥型、悬链线型过渡段的阶梯型半波谐振复合型变幅杆的设计计算比简单型变幅杆更复杂和困难些,但其可扩大变幅杆使用的适应范围。本文第(二)部分是对经过与第(一)部分类似变换后的这三种复合型变幅杆进行计算的方法简述、计算结果概述和使用设计用表进行变幅杆类型的对比选择和设计计算的例子。     

单端输入多端输出的纵振动转换体的研究

传统的超声振动系统一般为一个换能器连接一套变幅杆(或还有工具头),产生沿长度方向上的伸缩振动,这就意味着一套超声振动系统只能加工、处理一个对象,不利于生产效率的提高.本文提出单端输入多端输出的纵振动转换体,由一个输入杆、纵振动变换器、多个输出杆组成.利用振动转换体输入杆、输出各杆两端面的自由边界条件,以及输入杆与变换器、变换器与输出杆连接处振动质元的纵向力、横向力、弯矩与转角连续条件,推导出了设计振动转换体的频率方程,对转换体的纵振动谐振频率进行了计算,与有限元法和实验测试值基本吻合.将振动转换体与纵振频率为19.80 k Hz的换能器相连接,激光测振仪测试了复合振动系统的纵振谐振频率和谐振频率处各输出杆的振型.结果表明,各输出杆端面为活塞振动.换能器若连接本文提出的纵振动转换体,可以实现纵振动的多端输出,处理多个工作对象.文中分析了实现纵振动的转换原理,并通过计算得到了纵振动转换体的谐振频率与各振动部件的几何参数、角度的关系.     

具有夹角结构纵振动变幅杆的设计方法

变幅杆是功率超声纵振系统中的关键部件之一,常见的是沿直线方向传播的变幅杆.有的应用场合需要变换纵振动传输方向.本文研究了具有夹角结构的超声纵振动变幅杆的设计方法.利用两端自由边界条件和夹角连接处的位移、力、弯矩及转角连续条件建立了设计变幅杆的频率方程,给出了计算变幅杆振幅放大系数的方法.利用本文中提出的设计方法,计算了若干个由两段杆组成的不同夹角的变幅杆的谐振频率,与有限元计算结果及Vib Pilot系统测试的变幅杆频率基本一致;后与谐振频率为19.8k Hz的压电换能器相连接,激光测振仪测试了系统的谐振频率、变幅杆的放大系数及变幅杆输出端面的振型.测试得到的变幅杆的放大倍数、振型与计算结果吻合.测试的端面振型呈活塞振动,说明在谐振频率上将换能器激励的沿水平方向的纵向振动,经过变幅杆成功地变换到了其输出端上.最后,对该型变幅杆作了大量计算,得出了放大倍数随几何尺寸变化的规律.     

夹角型超声变幅杆的矩阵解析法

对新型的夹角型超声变幅杆的设计方法进行研究,借鉴传输矩阵法的思想利用一维振动理论推导了均匀杆两端界面各矢量间关系的特性矩阵,结合变幅杆连接处位移、力、转角和力矩的连续条件得到了夹角型超声变幅杆谐振频率的矩阵解析法.计算了不同尺寸变幅杆的谐振频率,计算结果与实验测试结果相一致.     

数控刀具磨损智能检测及其切削试验研究

在数控机床切削加工过程中,对刀具磨损导致的振动及切削温度的变化特征进行了理论分析,得到刀具的磨损与振动及其切削温度的关系.利用这些关系,设计并研制了基于STC89S52的数控刀具磨损智能检测与报警装置.试验验证表明该装置能够有效地实现对数控刀具磨损情况的在线检测.     

超声波加工工具对复合变幅杆谐振性能影响

基于变截面杆纵振动的波动方程，推导出安装简单工具双曲过渡形复合变幅杆频率方程和放大系数的一般公式，并讨论了超声波加工工具对复合变幅杆谐振性能的影响．随着工具长度和直径的增加，变幅杆谐振频率下降，应根据工具尺寸相应调整复合变幅杆末端长度，才能保证更好的谐振．推导出的一般公式为超声变幅杆及其工具的设计和使用提供了理论依据。     

新型压电行走机构的行走特性

压电行走机构是利用压电陶瓷逆压电效应和谐振特性,将电能转化为机械能的一种新型驱动装置。为避免惯性、摆动、两足移动式压电行走机构运动形式单一问题,研制了一种新型的压电行走机构振动测试系统。通过实验获得了驱动电压、谐振频率、负载载荷、振动角等诸多因素对机构行走速度和在沿行走方向上的驱动力的影响规律。分析显示,行走机构在滑移状态下,行走速度出现最大值,运行平稳;行走装置的后足设置行走轮时,行走状态最好。实验结果为压电行走机构驱动控制系统的设计提供了必要的数据依据。     

超声磨削杯形工具变幅器的设计与试验分析

为得到更为有效的设计理论,将杯形工具变幅器分为圆锥形变幅杆、圆盘和圆管三部分,利用Mindlin中厚板理论求得圆盘的位移、转角、弯矩和剪力的解析表达式,并建立了圆锥变幅杆和圆管的位移与应力函数关系。通过振动单元之间的连续条件以及振动单元的边界条件,建立了杯形工具变幅器整体的频率方程。基于此理论设计了杯型工具变幅器,通过有限元模态分析、阻抗分析试验和超声谐振试验对设计理论进行了验证。仿真结果表明,变幅器的谐振频率与设计频率相符合;试验结果表明,谐振系统的实测频率与设计频率相符合。试验结果验证了杯形工具变幅器设计方法的正确性,为超声磨削系统的设计提供了理论依据。     

变幅杆斜槽参数对纵弯振动系统的影响

为了实现超精密切削,设计了二维纵弯超声振动系统中变幅杆的结构。通过分析开斜槽变幅杆的结构,理论上揭示了斜槽位置d、斜槽倾斜角α、斜槽长度l和斜槽间距h对变幅杆的谐振频率和纵弯两个方向振幅的影响规律。采用有限元动态数值模拟分析,得到不同斜槽参数情况下的谐振频率、振幅。发现随着α、l逐渐增大,模态频率呈现整体下降趋势,当α=45°时,弯曲振幅最大。在d=15mm附近,振幅值最小,并且随h变大,振幅变小。利用正交参数的极差分析法得到斜槽各参数对谐振频率和振幅影响力度的主次。进一步通过实验,发现了随着α、h逐渐增大,谐振频率整体下降,且振幅随h的增大而减小。实验结果表明α通过对振幅的影响进而实现对切削力的控制,这与理论分析结果一致。     

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