International audienceThe friction damper has been widely used to reduce the resonant vibration of blades. The most commonly used methods for studying the dynamic behavior of a blade with a friction damper are direct integration methods. Although the harmonic balance method (HBM) is a well-known method for studying nonlinear vibration problems, generally only a one-term approximation has been proposed to study the nonlinear vibration of a frictionally damped blade. In this work, a HMB procedure with a multiterm approximation is proposed. The results show that the steady-state response and other related behavior of a frictionally damped blade can be predicted accurately and quickly by an HBM with a multiterm approximation

The dynamic behavior of a mechanical system generally are strongly affected by the properties of mechanical joints. An identification method which directly used the measured frequency response functions (FRFs) to identify the joint properties was introduced in this work. Because the measurement noise in the frequency response functions is unavoidable in practice and may lead to very faulty results, the proposed method has been developed especially to overcome this problem. The accuracy and feasibility of the proposed method were verified and demonstrated by theoretical simulation and experiments. The results show that the joint properties can be identified accurately from the FRFs even with noise effect.

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Cu nanotubes have been synthesized using silicon oxide nanowires as templates. The silicon oxide nanowires were then coated with a thin, uniform copper layer by metallorganic chemical vapor deposition ͑MOCVD͒. Hollow Cu nanotubes were then produced by etching away the inner silicon oxide templates with dilute HF solution. The synthesis process was simple and of low cost. A large quantity of the Cu nanotubes can be readily grown.Nanotechnology has now been recognized to have the potential to revolutionize a host of industries. 1 One-dimensional hollow nanostructures, also called nanotubes or nanotubules, have attracted much attention owing to their potential applications in optoelectronics, biosensors, catalysis, and the separation of chiral compounds. [2][3][4] Because of their unique structural characteristics, the preparation of nanotubes is relatively difficult, and fewer synthetic technology have been developed compared to those for other one-dimensional ͑1D͒ nanostructures, such as nanorods and nanowires. [5][6][7][8] Metal nanotubes and nanorods display a wide range of applications in optical and electronic devices. In particular, among all metal 1D nanostructures, Cu nanorods and nanotubes are attracting most widespread attention, as Cu is well-known as an outstanding interconnect for future generations of electronic nanodevices because of its good electrical conductivity and high electromigration resistance. 9 The preparation of tubelike structure might be important in the design of nanotransistors since junctions could be formed by filling the core of the tube with a desirable material. 10 For example, filling some semiconductor materials into the Cu nanotubes should result in a junction on the interface between Cu shell and inner semiconductor materials. Filling some luminescent materials into the Cu nanotubes might also result in different optical properties.Various techniques including electrical arc evaporation, 1 supercritical fluid preparation, 10,11 and chemical solution method 9 have been developed for synthesizing Cu and Cu oxide nanowires and nanotubes. However, the reports on pure Cu nanotubes have been scarce owing to the ease of oxidation of Cu in the synthesis process. In addition, Cu nanowires and nanotubes would coexist in the products using most of these synthesizing methods.In all template synthesis, a silicon oxide template is easy to remove but relatively difficult to process. The silicon oxide nanowires are of the amorphous structure with a low density of nucleation centers. As a result, the surfaces of silicon oxide nanowires are usually not amenable for the formation of a continuous metal layer by most of synthesizing methods. In the present study, Cu atoms generated by metallorganic chemical vapor deposition ͑MOCVD͒ could be adsorbed onto the surfaces of silicon oxide nanowires and diffuse to form continuous Cu layers. Pure Cu nanotubes were formed readily by etching the silicon oxide nanowires as a template. In addition, large-scale production of Cu nanotubes could be realized wi...

The friction damper has been widely used to reduce the resonant vibration of blades. The most commonly used methods for studying the dynamic behavior of a blade with a friction damper are direct integration methods. Although the harmonic balance method (HBM) is a well known method for studying nonlinear vibration problems, generally only a one–term approximation has been proposed to study the nonlinear vibration of a frictionally damped blade. In this work; a procedure of the HBM with a multi–term approximation is proposed. The results show that the steady state response and other related behavior of a frictionally damped blade can be predicted accurately and quickly by the HBM with a multi–term approximation.