Stabilization of high frequency chatter vibration in fine boring by friction damper

Friction damper has been found successful to prevent high frequency chatter occurring at more than 10,000Hz, and causing problem of reduced tool life in fine boring operation. The new damper is characterized by simple structure that consists of an additional mass attached to the main vibrating structure with small piece of permanent magnet. The principle is straightforward in which Coulomb and viscous frictions dissipate vibration energy at the interface between the damper and main vibrating structure. The damper needs no tuning, and is effective at high frequency. The paper first introduces a typical design of the friction damper with experimental proof by cutting tests of its effectiveness in eliminating the high frequency chatter in fine boring, and assuring normal tool life of the cutting edge. Theoretical and experimental analyses are introduced for understanding the fundamental principle and characteristics of the new damper. The new damper is effective for boring tools, which vibrate at frequency more than 5,000Hz.     

高频群脉冲电源在微细孔电化学加工中的应用

针对电化学加工的特殊需要所设计的一种新型电源———高频群脉冲电源的设计原理和特征,从理论上分析其对 于传统的直流电源和脉冲电源在微小型零件加工中的优越性;通过微细孔加工对这种新型的电源进行了分析和说明。 结果表明,在微小型加工领域,采用高频群脉冲电源在改善加工精度,提高加工质量方面优于直流电源和脉冲电源。     

一种基于振动信号处理的颤振预报方案研究

针对切削过程中产生的颤振现象,通过对机床的在线监测,将采样出的振动加速度信号进行数据处理,提出一种以方差和互相关系数作为综合判据的方法来判别颤振是否发生,并在MATLAB环境下仿真证明该方法的可行性。     

Simultaneous double-sided milling of flexible plates with high accuracy and high efficiency—Suppression of forced chatter vibration with synchronized single-tooth cutters

This paper presents a new method to finish flexible plates with high accuracy and high productivity. Precision steel plates are finished conventionally by face milling with electro-magnetic chucks. It is difficult to improve flatness of the flexible plates, because they deform to fit the chuck surfaces while clamped. The authors have applied simultaneous double-sided milling to solve this problem, but it causes forced chatter vibration which is not allowed in precision finishing. Thus, the new method is proposed and verified to suppress the forced chatter vibration, in which the both surfaces are finished simultaneously with single tooth milling cutters with synchronization so that the thrust forces are cancelled out on the both sides.     

制动摩擦高频振动及其防治

在低速制动工况下一些机车车辆转向架有高频振动现象出现,有的还非常大。制动高频振动对车体、转向架和系统产生较大的破坏作用,恶化了车辆的运行平稳性,对铁道沿线的噪音污染加重。制动高频振动是一种自激振动,如何避免对制动系统十分重要。对制动工况下一些机车车辆转向架发生的高频振动现象的机理进行了分析,并提出了解决方法。仿真结果表明制动高频振动与转向架构架结构和悬挂系统有关,可通过改进构架设计或调整转向架参数予以避免。     

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.     

一种新型高低频复合振动装置的研究

针对金属材料疲劳断裂研究的现状以及实际应用中应力比r的变化情况,分析了应力比r对金属疲劳裂纹萌生和扩展的影响.运用Pro/E设计了一种新型高低频复合振动装置,对其空载运动状态下的动力学特性做了理论分析.建立了振动装置加栽金属材料时的动力学模型,以加载7A09高强度铝合金为算例,运用ANSYS对模型进行谐波分析,得到了此种情况下的幅频特性曲线图,并由此获得了在该状态下最易发生疲劳断裂的变频区间.     

Rotary ultrasonic machining: effects of tool natural frequency on ultrasonic vibration amplitude

Rotary ultrasonic machining (RUM) is a hybrid machining process that combines the material removal mechanisms of grinding and ultrasonic machining. RUM has been applied to hole-making for a wide range of materials. It is known that ultrasonic vibration amplitude has significant effects on cutting force, torque, and surface finish in RUM. One experimental observation that has been reported in the literature multiple times states that different tools show different vibration amplitudes on the same ultrasonic power level. However, no analyses can be found in the literature to explain this observation. The existence of this knowledge gap makes it difficult to explain some experimentally obtained trends or to conduct more realistic physics-based modeling work. The objectives of this research are to understand the effects of tool natural frequency on ultrasonic vibration amplitude in RUM, to provide an explanation to the observation and verification of measurement methods, and also to guide tool design and selection in RUM. Ultrasonic vibration amplitudes of tools are measured by three methods and compared. It is found that tool natural frequency significantly affects ultrasonic vibration amplitude. The tool with its natural frequency closest to that of the ultrasonic power supply (20?kHz) generates the highest ultrasonic vibration amplitude on every ultrasonic power level tested.     

高频群脉冲电化学加工中频率对极间间隙的影响

给出了脉冲电化学加工极间平衡间隙的数学模型,并据此讨论了高频群脉冲电化学加工中,电源主脉冲频率与平衡加工间隙的关系.在模拟结果中,极间平衡间隙与主脉冲频率则呈严格的线性关系,即随频率增加平衡间隙线性减小.并根据设计的硬币花纹工艺试验表明,选择较高的主脉冲频率,可获得较小的加工间隙,进而获得良好的表面质量.由此可得出结论：良好的加工质量来源于高频所带来的较小极间间隙.     

Improvement of chatter stability in boring operations with passive vibration absorbers

This paper is focused on the behavior of boring bars with a passive dynamic vibration absorber (DVA) for chatter suppression. The boring bar was modeled as a cantilever Euler-Bernoulli beam and only its first mode of vibration was considered. The stability of the two-degree-of-freedom model was analyzed constructing the stability diagram, dependent on the bar characteristics and on the absorber parameters (mass, stiffness, damping, and position). Two analytical approaches for tuning the absorber parameters were compared. The selection criterion consisted on the maximization of the minimum values of the stability-lobes diagram. Subsequent analysis performed in this work, allowed formulating of new analytical expressions for the tuning frequency improving the behavior of the system against chatter.     

枪钻低频振动钻削振动问题的研究

概述了枪钻低频振动钻削的加工原理,介绍了国内外的研究和发展状况,指出了该项技术研究所存在的问题,并对今后的研究方向作了展望。     

高频热合机电磁辐射抑制技术的研究

根据国家电磁兼容标准(GB4824-2004-2A),针对传统高热合机在主频、二倍频和三倍频处的辐射强度严重超标的问题,结合高频热合机的工作原理对其电磁兼容性进行深入的研究,通过采取三种措施:1)在热合机机头部位设计制作谐振电路衰减器,通过建立陷波槽和反作用场的方法,削弱和吸收热合机机头强辐射电磁场,使电磁泄漏辐射场强得到衰减;2)采用电磁辐射屏蔽衰减技术,对高频功率的铜片馈线进行屏蔽;3)重新设计高频振荡电路,减少振荡输出的谐波分量.试验结果证明:采取对电磁辐射抑制措施后高频热合机的输出频率符合国家规定的频率标准,解决了目前高频热合机工作时的电磁泄露辐射污染问题,带来了很好的社会、环境和经济效益.     

Decomposition of process damping ratios and verification of process damping model for chatter vibration

In the previous study, by the same authors, titled “A new process damping model (PDM) for chatter vibration (Measurement, 44 (8) (2011) 1342–1348)”, a new approach has been presented for obtaining process damping ratios (PDRs). This PDM has been constituted on the basis of the shear angle (φ)$(\phi )$ oscillations of the cutting tool and the alteration of the penetration forces when they penetrate into the wavy surface. Variation and quantity of PDR are predicted by reverse running analytical calculation procedure of traditional Stability Lobe Diagrams (SLDs). In this study, firstly, how the PDM in previous study results with different materials such as AISI-1050 and Al-7075 are examined. Then, two problems are solved: how much of the total PDR of cutting system is caused by the tool penetration and how much is caused by (φ)$(\phi )$ oscillation? Finally, verification of PDR values and PDM are performed by energy equations.     

高锰钢切削刀具的设计

高锰钢切削极易产生硬化层,很难加工。在生产实践中,通过合理地选择刀具材料、刀具结构、切削用量等,可以很好解决高锰钢难加工的问题,保证了高锰钢的加工质量。     

高速加工技术在模具制造中的应用

阐述了在模具加工中实现高速加工所必需的一些关键技术,及高速加工技术在模具制造中的意义,并通过与常规的加工方式EDM的对比,描述了高速加工的优越性和局限性。同时以加工实例说明高速切削是现代模具加工的发展方向之一。     

High frequency testing of rubber mounts

Rubber and fluid-filled rubber engine mounts are commonly used in automotive and aerospace applications to provide reduced cabin noise and vibration, and/or motion accommodations. In certain applications, the rubber mount may operate at frequencies as high as 5000 Hz. Therefore, dynamic stiffness of the mount needs to be known in this frequency range. Commercial high frequency test machines are practically nonexistent, and the best high frequency test machine on the market is only capable of frequencies as high as 1000 Hz. In this paper, a high frequency test machine is described that allows test engineers to study the high frequency performance of rubber mounts at frequencies up to 5000 Hz.     

Realization and dissemination of high frequency power standard at INRIM

In the High Frequency (HF) field, the primary power standard is maintained through reference sensors calibrated in terms of effective efficiency η_e. These devices are in turn used to transfer the power standard by means of direct comparison on the same matched generator. For this kind of operation, the only knowledge of the effective efficiency of the device is not enough and additional parameters of the reference sensor are necessary.The paper describes the methods and techniques used at INRIM to disseminate the “HF power standard”, with emphasis to all the technical aspects involved, in order to provide a thorough explanation of the procedures implemented.     

Uncertainty analysis of high frequency image-based vibration measurements

Image-based vibration measurement techniques allow to remotely measuring the displacement of multiple targets in the field of view, without the need to mount anything on the measurand. In this paper the uncertainty budget of vision systems has been performed in order to both optimize the measurement procedure and identify the potential application fields. Two different types of camera are used in this work, both of them equipped with a 1280 × 1024 px sensor but with two different maximum frame rates at full resolution: 25fps and 2000fps respectively. The uncertainty analysis proposed here is based on a careful identification of the uncertainty sources and on experimental tests on an electro-magnetic shaker, where the displacement measured with the cameras are calibrated by means of the reference measurements provided by state-of-the-art traditional techniques.     

振动系统动力学模型修正方法比较研究

振动系统的动态特性主要取决于其模态参数.修正动力学模型可以提高分析模型与实际系统二者模态参数的一致性或其频响函数曲线间的相似度.这对于准确、可靠预测振动系统的动态特性或动态响应非常重要.文中概述了模型修正基本理论,并对不同模型修正方法进行比较分析.     

Modeling of a hydraulic engine mount for active pneumatic engine vibration control using the extended Kalman filter

The attenuation of engine vibration transmitted to a chassis has been a major focus in the automotive community for the increase of comfort for the driver and passengers. A hydro-mount system is designed to reduce the transmission of engine vibration to the chassis. It is also used for supporting the static load by an engine weight. In this paper, we present a modeling and parameter estimation of hydro-mount systems. Nonlinear model aspects are developed and used with experimental data to validate the model response characteristics. These parameters will be modeled as a variable vector and its value is estimated via linearized and extended Kalman filter. This approach can help engineers reduce design time by providing insight into the effects of various parameters within the hydro-mount. Based on the estimated parameters, the simulation result confirmed that the derived passive model describes the dynamic behavior of the hydro-mount system accurately. This paper was recommended for publication in revised form by Associate Editor Shuzhi Sam Ge Arjon Turnip received his B.S. and M.S. degrees in Engineering Physics from the Institute of Technology Bandung, Indonesia, in 1998 and 2003, respectively. He is currently a Ph.D. program student in the School of Mechanical Engineering, Pusan National University, Korea. His research areas are integrated vehicle control, adaptive control, and estimation theory. Keum-Shik Hong received the B.S. degree in mechanical design and production engineering from Seoul National University in 1979, the M.S. degree in ME from Columbia University in 1987, and both the M.S. degree in applied mathematics and the Ph.D. degree in ME from the University of Illinois at Urbana-Champaign in 1991. He served as an Associate Editor for Automatica (2000–2006) and as an Editor for the International Journal of Control, Automation, and Systems (2003–2005). Dr. Hong received Fumio Harashima Mechatronics Award in 2003 and the Korean Government Presidential Award in 2007. Dr. Hong’s research interests include nonlinear systems theory, adaptive control, distributed parameter system control, robotics, and vehicle controls. Seonghun Park received his B.S. and M.S. degrees in mechanical engineering from KAIST in 1994 and 1996, respectively, and his Ph.D. degree from Columbia University in 2005. Dr. Park is currently a professor of mechanical engineering at Pusan National University, Korea. His research interests are in the areas of control, tribology, and biomechanics.