微细钻头超声轴向振动钻入横向偏移的有限元分析

利用有限元技术对微细钻头超声轴向振动钻入横向偏移过程进行深入分析。结果表明,超声轴向振动钻削从根本上改变了普通钻削的钻入机理,减小了横向偏移量,提高了钻入定心精度,特别适合硬脆材料上的微小孔的精密和超精密加工。     

超声振动切割细胞系统的设计

根据细胞微切割实验对超声振动切割系统的要求,对夹心式超声换能器和超声变幅杆组成的振动系统进行了设计,超声换能器采用夹心式压电换能器,变幅杆是一种将等截面圆柱形阶梯变幅杆的一端替换成圆锥形变幅杆构成的新型复合圆锥阶梯形变幅杆,设计了超声换能器和变幅杆的基本结构,并给出其制造尺寸.     

声振动修整砂轮系统的阻抗分析

通过合理划分超声振动修整系统,计算出超声振动修整砂轮系统的各个子系统机械阻抗,运用机械阻抗综合法求出系统的共振频率,为实验中寻求系统的谐振点提供了理论依据.并且提出修整瓦的尺寸对系统的谐振频率影响不大,从而简化修整瓦的设计.     

Effect of geometrical parameters in micro-grooved crosshatch pattern under lubricated sliding friction

Tribological test was carried out using a pin-on-disc geometry with textured SKD11 pin on bearing steel disc, under sliding in paraffin oil. Micro-grooved crosshatch pattern has been fabricated with various angles and widths. The effects of geometrical parameters on friction were mainly examined in mixed and elastohydrodynamic lubrication. The results show that friction control can be achieved by fabricating the micro-grooved crosshatch pattern on a contact surface. It is observed that each geometrical parameter of texture influence on friction, especially decrease of groove aspect ratio and increases of groove sliding length show friction reduction performance. Crucial parameter G_l was proposed for micro-grooved crosshatch texture. The friction mechanism is explained by micro fluid flow with limited theoretical approach.     

考虑齿间滑动摩擦的齿轮接触疲劳强度计算

齿轮啮合中轮齿间除了滚动接触外还存在相应的滑动接触,使轮齿间具有较大的摩擦力,针对传统赫兹理论形成的齿面接触疲劳强度计算没有考虑齿间摩擦,将摩擦系数引入计算公式,并给出相应摩擦系数的计算.     

微超声振动机器人系统的设计与分析

设计一套微超声振动机器人系统用于细胞切割.超声振动单元安装在并联机器人的动平台上,压电陶瓷驱动器控制操作针做高频振动,直到刺破细胞的壁膜,减少穿刺过程中细胞的变形,从而减小对细胞的损伤.该系统用于牛卵细胞微切割试验,取得很好的效果.     

The evolution of the surface layers on metals in sliding friction

The methods of speckle-interferometry, electron, optic, and atom-force microscopy were used to study the structure and regularities of deformation of surface layers on metals and alloys in friction. The causes of deformation localization are analyzed. An explanation of the strong wear resistance of Hadfield steel is proposed using data on the evolution of the surface layer structure.     

超声振动精密深孔镗削试验研究

通过超声振动深孔镗削试验,研究了超声振动镗削时切削速度、进给量和背吃刀量对加工精度和表面粗糙度的影响规律,分析了精密深孔超声振动镗削时的切削机制.     

Analysis of the nonlinear behavior of gear pairs considering hydrodynamic lubrication and sliding friction

This paper describes an analysis of the nonlinear behavior of gear pairs according to the direct contact elastic deformation model over a wide range of speeds, considering the hydrodynamic effects and friction force. The inclusion of the hydrodynamic effect facilitates nonlinearity by increasing the overlap range (i.e., multiple solution regimes) and damping, as well as decreasing elastic deformation and tooth reaction forces. The effects of various lubrication parameters, such as viscosity and film width, on the nonlinear dynamic behavior were analyzed. While the viscosity has a strong effect on the behavior of gear pair systems, friction has very little effect on torsional behavior. Although the model of direct contact without friction has overall nonlinear behavior similar to the model including hydrodynamic effects with friction, the time data of these models are different due to the squeeze effect. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Cheon Gill-Jeong received his B.S. in Mechanical Engineering from Seoul National University (SNU), Korea, in 1981. He then received his M.S. and Ph.D. degrees from SNU in 1983 and 1988, respectively. He served as a senior research engineer at Seoul National University Hospital and Daewoo Heavy Industry for several years. Dr. Cheon is currently a Professor at the Division of Mechanical Engineering at Wonkwang University in Iksan, Korea. His research interests include dynamics, tribology, and design engineering.     

超声波扭转振动铰孔装置

基于分离型振动切削原理,设计了一种振动频率为20.7KHz、振幅为15μm的扭转振动装置。该装置由两个纵向换能器、两个纵向变幅杆、一个扭转变幅杆和支座组成,使用时将其安装在车床上,可完成对精密小深孔的超声振动铰削。     

Characteristics of chip generation by ultrasonic vibration cutting with extremely low cutting velocity

Recently, mirror-surface machining of brittle materials such as ferrite, glass, and optical plastics has become more important, as these materials are used in optical communications and precision devices. Non-ferrous metals such as aluminium and copper were readily turned with diamond tools, but as the need for both infra-red and reflective optics escalated, the need to machine brittle materials arose. In this paper, ultrasonic vibration cutting at 20 kHz at extremely low cutting velocity for the precision machining of brittle plastics used for optical lenses is suggested and tested. The mechanism of chip generation, and characteristics of surfaces in the ductile mode, machined by ultrasonic vibration cutting are investigated. As a result, when micro cutting by ultrasonic vibration, it was confirmed that the chips generated by ductile mode cutting are obtained at 1/40 of the critical cutting velocity of the ultrasonic vibration cutting system, which is an extremely low cutting velocity.     

Explaining the mechanics of metallic sliding friction and wear in terms of slipline field models of asperity deformation

It is shown that the force which opposes the sliding of a hard relatively smooth surface over a softer surface can be explained as the force needed to push waves of plastically deformed material along the soft surface ahead of asperities on the hard surface. For rougher surfaces and/or poorer lubrication it is shown how the wave can be torn off or material removed by a chip formation process and wear particles formed. Coefficients of friction predicted from the corresponding asperity deformation models are shown to give good agreement with experimental results. For smooth well lubricated surfaces the wear of the softer surface is shown to occur as a result of the progressive damage to this surface brought about by the repeated passage of waves across it. Equations for predicting wear are derived from the asperity deformation models and a comparison made between predicted and experimental wear results. The paper ends by considering possible future trends in research into the mechanics of friction and wear.     

超声振动车削光整技术的试验研究

利用超声振动进行车削光整加工试验,对影响光整表面粗糙度的因素进行了大量的试验研究,通过对比试验和正交试验确定了合理的切削参数.分析了影响加工表面质量的一些因素,为推广使用超声振动车削光整工艺做出了试验上的分析和论证,分析了超声车削光整工艺的优越性和规律性。     

A comparison of the relative friction and wear responses of PTFE and a PTFE-based composite when tested using three different types of sliding wear machines

In this work, the tribological behavior of a commercially available polytetrafluoroethylene-based composite material filled with polyimide microparticles has been thoroughly investigated using different approaches. Specifically, two standard tribological tests, i.e., pin-on-disc and thrust washer measurements, have been compared with sliding tests performed on real components using a specially designed lab bench. The obtained results demonstrated that, despite the different testing methods (continuous rotation vs. reciprocating linear movement for the pin-on-disc/thrust washer and sliding tests, respectively), the different techniques provide highly comparable data within the adopted experimental conditions and can be successfully combined to assess the overall tribological features of this PTFE-based polymer composite.     

Some considerations of slideway friction characteristics by observing stick-slip vibration

It is important to clarify the frictional characteristics of a slideway and to prevent unstable vibration, such as stick-slip vibration, for the improvement of kinematic performance and for precise positioning. In this research, the relations among the dynamic friction characteristics, the pitching motion or the floating up of the slider, the surface roughness of a slideway, and the lubricant property are investigated experimentally. As a result, some points necessary for the kinematic performance improvement of the slider are clarified.     

超声振动切削超薄壁精密零件的圆度误差试验研究

试验研究了超声振动车削直径为47.75mm壁厚为0.8-1.5mm的照相机导向筒超薄壁精密零件的圆度形成规律及切削参数对圆度误差的影响。研究表明:超声车削精密超薄壁零件,圆度误差最小是普通精密切削的1/3。     

High-temperature sliding wear of metals

Temperature can have a considerable effect on the extent of wear damage to metallic components. During reciprocating sliding, under conditions where frictional heating has little impact on surface temperatures, there is generally a transition from severe wear to mild wear after a time of sliding that decreases with increase in ambient temperature. This is due to the generation and retention of oxide and partially-oxidized metal debris particles on the contacting load-bearing surfaces; these are compacted and agglomerated by the sliding action, giving protective layers on such surfaces. At low temperatures, from 20 to 200°C, the layers generally consist of loosely-compacted particles; at higher temperatures, there is an increase in the rates of generation and retention of particles while compaction, sintering and oxidation of the particles in the layers are facilitated, leading to development of hard, very protective oxide ‘glaze’ surfaces. This paper reviews some of the main findings of extensive research programmes into the development of such wear-protective layers, including a model that accounts closely for the observed effects of temperature on wear rates during like-on-like sliding.     

Analysis of regenerative chatter suppression with adding the ultrasonic elliptical vibration on the cutting tool

A method is proposed to suppress regenerative chatter in turning operation, in which the ultrasonic elliptical vibration is added on the cutting tool. It results in the fact that the cutting tool is separated periodically from the chip and the workpiece, and the direction of the frictional force between the rake face of the cutting tool and the chip is reversed in each cycle of the ultrasonic elliptical vibration. The experimental investigations show that the regenerative chatter occurring in ordinary turning operation can be suppressed effectively by applying the ultrasonic elliptical vibration on the cutting tool. In order to clearify the reason of the regenerative chatter suppression, theoretical analysis and computer simulation are performed on turning with ultrasonic vibration. There is a good agreement among the experimental investigations, theoretical analysis and the computer simulation.     

Pre-sliding friction control using the sliding mode controller with hysteresis friction compensator

Friction phenomenon can be described as two parts, which are the pre-sliding and sliding regions. In the motion of the sliding region, the friction force depends on the velocity of the system and consists of the Coulomb, stick-slip, Streibeck effect and viscous frictions. The friction force in the pre-sliding region, which occurs before the breakaway, depends on the position of the system. In the case of the motion of the friction in the sliding region, the LuGre model describes well the friction phenomenon and is used widely to identify the friction model, but the motion of the friction in the pre-sliding such as hysteresis phenomenon cannot be expressed well. In this paper, a modified friction model for the motion of the friction in the pre-sliding region is suggested which can consider the hysteresis phenomenon as the Preisach model. In order to show the effectiveness of the proposed friction model, the sliding mode controller (SMC) with hysteresis friction compensator is synthesized for a ball-screw servo system.     

弯曲振动圆盘振动特性试验研究

对超声振动系统中弯曲振动圆盘的振动特性进行了试验研究,结果表明,减小圆盘厚度,谐振频率减小;减小圆盘直径,谐振频率增大。在振动系统设计中,将变幅杆与弯曲振动圆盘设计成一体,克服了原来由于螺纹连接所造成的缺陷。通过试验得知,弯曲振动圆盘是以弯曲振动为主,存在一定反射波的干扰,并且圆盘具有增幅特性,圆盘的最大振幅约为18μm。所获得的结论对振动系统结构设计以及在超声深孔珩磨中的应用有一定的参考价值。