共查询到16条相似文献,搜索用时 125 毫秒
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传统超声加工用工具或者很短,或者按半波长整数倍叠加.加工中工具长度的大量磨损会明显降低加工效率,因而必须经常更换工具.本文提出一种新型的超声加工深小孔的工具系统,能以特殊的方式工作.工具长度任意,加工中工具长度变化允许达80%;仅仅需要适当调节电发生器频率就能良好工作.本工具系统已成功地用在超声加工玻璃深小孔(圆形和异形孔),在玫璃上加工出直径6mm、深达280mm的孔.加工效率至少可以与常规方法相比. 观测了具有等截面细长杆的复合振动系统的频率特性和工具系统的振动模式,得出了工具杆“局部共振”的结论.初步探讨了产生这种共振的条件及其形成机理. 局部共振现象,应当还可用在高功率超声的其它场合. 相似文献
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本文从耦合振动的角度出发,对超声加工系统中出现的“局部共振”现象进行了研究,通过对振动系统的分析用计算,指出“局部共振”流言是耦合振动的一种表现。 相似文献
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对超声复合振动系统中的“局部共振”现象,基于熟知的棒或管中声波产生和传播的理论,提出一种机理解释。 相似文献
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A novel metamaterial multi-span beam with periodic simple supports and local resonators is designed and investigated. The frequency responses of the proposed metamaterial multi-span beam are computed by the spectral element method (SEM). The accuracy and feasibility of the SEM are verified by the finite element method (FEM) and the vibration experiments. The results show that the metamaterial multi-span beam could generate both the local resonance band-gaps in the low-frequency ranges and the Bragg band-gaps in the medium and high frequency regions. By adjusting the natural frequencies of the local resonators, the thickness of the base beam and the length of the unit-cell, the local resonance and the Bragg band-gaps can be controlled, respectively. The coupling effects of these two kinds of band-gaps are investigated by the parametrical design, which broadens the band-gaps and consequently improves the vibration reduction performance. 相似文献
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S. Hirsekorn U. Rabe W. Arnold 《Applied Physics A: Materials Science & Processing》2001,72(7):S87-S92
In dynamic force microscopy the cantilever of an atomic force microscope is vibrated at ultrasonic frequencies in the range of several 10 kHz up to several MHz while scanning a sample surface. The amplitude and phase of the cantilever vibration as well as the shift of the cantilever resonance frequencies provide information about local sample surface properties. In several operation modes of dynamic force microscopy, for example force modulation microscopy, tapping mode or atomic force acoustic microscopy, the sensor tip is in contact with the sample at least during a fraction of its vibration cycle. The periodic indentation of the tip with the sample surface generates ultrasonic waves. In this paper, the ultrasonic radiation of a vibrating cantilever into a sample and its contribution to the damping of the cantilever vibration are calculated. The theoretical results are compared to experiments. 相似文献
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Based on the Rayleigh energy theory combining with Timoshenko beam model, the flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators are investigated. Additionally, the simplified formulae are derived to study the fundamental flexural resonance frequencies of the piezoelectric tubes with free-free ends and cantilevers. By changing the sizes of the tubes and the mass loads at the free ends, the variations of the flexural resonance frequencies of the piezoelectric tubes and cantilevers are calculated theoretically. To verify accuracy of the simplified formulae, by changing the lengths of the tubes and the mass loads the flexural resonance frequencies of the piezoelectric tube with free-free ends are measured experimentally. The theoretical results agree well with the experimental measurements, which demonstrate that the simplified formulae are accurate and effective for analyzing the flexural vibration characteristics of the piezoelectric tubes in the ultrasonic micro-actuators. 相似文献
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Modulated angle beam ultrasonic spectroscopy for evaluation of imperfect interfaces and adhesive bonds 总被引:2,自引:0,他引:2
An experimental method incorporating high frequency pulsed angle beam ultrasonic measurements modulated by low frequency vibrations of a bonded structure is described. This method uses parametric/nonlinear mixing between high and low frequencies to characterize adhesive degradation. It is demonstrated that good quality (undamaged) bonds exhibit little dependence of ultrasonic signature on the overlay of low frequency vibration loads; however, environmentally degraded or imperfect bonds exhibit strong modulation of the resonance frequency of the ultrasonic signal reflected from the bond. The results are interpreted using a model for normal and oblique wave interaction with two nonlinear interfaces separated by an adhesive layer under quasi-static stress modulation. 相似文献
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This paper presents a general theory of the forced response under convected loading of mono-coupled periodic systems with a single disorder. The general expressions derived have been used to study the response of an infinite periodic beam on simple supports with one of the support spacings different from all the others. Convected harmonic pressure fields and frozen random pressure fields have been considered. Computer studies are presented showing the moment response at supports and the space-time-averaged responses in the disorder and in the nearby periodic beam elements. High response levels can occur due to (i) resonances of the beam length disorder against the stiffness of the attached periodic systems and (ii) hydrodynamic coincidence vibration occurring in the periodic beam. The frequency zones in which these high responses may occur are identified. The high response due to the resonance (ii) is restricted to the vicinity of the disorder, whereas that due to coincidence occurs throughout the system. Computed results show that the highest response levels do not necessarily occur in the beam length disorder, but may occur in one of the nearby periodic beam elements. The dependence of the maximum response levels on the magnitude of the disorder has been investigated. The conditions under which small disorders may be neglected have been pointed out. 相似文献
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该文将周期局域共振梁结构中的基体结构由单一材料发展成多相材料,建立了周期复合局域共振梁结构。由共振单元在单胞中的排列位置,考虑了三种构型,并利用传递矩阵方法计算了在弹性基底作用下这些结构产生的局域共振带隙性质。结果表明,与局域共振梁结构相比,复合局域共振梁结构产生的局域共振带隙对应的频率范围更宽,禁带范围内弹性波的衰减峰值和衰减均值更高。除此之外,该文还分析了局域共振结构、单胞尺寸、基体材料和局域共振结构中的阻尼对弹性波在空间中传播和衰减特性的影响,为满足特定的隔声隔振要求的结构设计提供了依据。 相似文献