Applied Mechanics and Materials Vols. 275-277

Abstract: Reducing noise and vibration is an increasingly important objective for designers and users of a wide range of mechanical system. Lubricant can contribute to reduction of overall noise and vibration generated by machines, both by reducing generation of acoustic energy in lubricated contacts and by modulating the transmission of vibration through the lubricant. This paper outlines various mechanisms by which the lubricant may affect the generation and transmission of acoustic vibration. Examples from the area of refrigeration compressor lubrication are presented, demonstrating that correct design and selection of lubricant can have a significant impact on noise and vibration.

Abstract: In this paper, the continuation technique is used to investigate the non-linear response of a suspended cable under harmonic excitation. A modified iteration procedure is applied to the nonlinear oscillator containing a quadratic term. From the formulated mathematical model of the suspended cable, the solution for the cable is obtained by means of the mixed averaging method. Also we can give the frequency simple with the modified iteration procedure. Moreover, the results obtained by this method and the numerical integration are compared. Also the offset is studied. Finally, the effects of the amplitude of the harmonic excitation on the suspended cable and the stability of the system are investigated.

Abstract: Based on the previous study, the coupling analysis for a submerged active constrained layer damping (i.e. ACLD) cylindrical shell with ring ribs is developed in this paper. Firstly, the governing equation for this kind of shell is proposed. Then, a multi-virtual-point-sound-source wave function superposition method combing the transfer matrix method is proposed to obtain the acoustic pressure level. Later, numerical results are given to verify the developed method. Finally, the damping effect for the ACLD treatment on the ring-stiffened cylindrical shell is discussed.

Abstract: Elastomeric damper is a very important component for helicopter rotor system; its dynamic property has strong nonlinear behavior characterized by complex hysteresis loops, and dependence on excitation frequency, amplitude and temperature. Based on internal variables theory, combined with the nonlinear spring model, a time domain nonlinear dynamic model of elastomeric damper used for helicopter rotor load prediction is presented. The model was characterized by using the genetic algorithm, the hysteresis loop of elastomeric dampers made of different elastomeric materials under several excitation frequencies and strain amplitudes was calculated with this model and compared with experimental data. It is shown that the presented model can predict the hysteresis loop of the elastomeric dampers with little relative errors, and the model is able to catch the variation of dynamic stiffness. Therefore, the presented method can be used for helicopter rotor load prediction and aeroelastic analysis.

Abstract: According to bent position and size on two HP-IP bent rotor,and combined with maintenance schedule,this paper puts forward two vibration control methods of low speed dynamic balance on site and high speed dynamic balance after turning.For the bent position in the turbine middle,on the basis of mode decomposition in bent rotor,the research show that balance weight according to a scale in the both ends and middle mainly of the turbine can achieve good results.

Abstract: For the study of response of ultra-precision machine under environment vibration and its influences on machining precision, the numerical simulation method is adopted in this paper, the equipment modes are analyzed for the rationality of established model compared to the test results; and the frequency response of the machine excited by the measured ambient vibration acceleration power spectral shows that the table displacement reaches up to 0.396μm, exceeding the value allowed. Therefore, it’s significant to consider the micro environment vibration in ultra-precision processing.

Abstract: To reduce the multi-dimensional vibration which exist in some vibrating machines or equipments such as running ambulances, a parallel mechanism with 3-translation DOFs was presented and introduced into the ambulance stretcher, then a three-translation vibration reduction platform was developed. The kinematics and dynamics equations of the presented vibration reduction platform were deduced. And then the workspace, tuning principles and dynamics characteristics were studied. The simulations show that the presented parallel mechanism or vibration reduction platform is valid for reducing vibration and the system has different natural frequencies in case that the upper platform of the mechanism works on some specific positions, so it can be used to achieve tunable vibration control.

Abstract: Microperforated panel (MPP) absorbers have been developed rapidly and used in many fields in recent years. First, based on the Maa’s theory, the theoretical development of MPP is reviewed in this paper. Furthermore, structure design and processing technology of MPP are introduced. Finally, the further development of MPP is discussed.

Abstract: A coupled actuator-flap-circuit system model and its online identification are presented. The coupled system consists of a piezoelectric tube actuator, a trailing-edge flap, and a series R-L-C circuit. The properties of the coupled system are examined using a Mach-scaled rotor simulation on hovering state. According to the high nonlinear hysteretic characteristics of the coupled system, the generalized dynamic fuzzy neural networks (GD-FNN) implementing Takagi-Sugeno-Kang (TSK) fuzzy systems based on extended ellipsoidal radial basis function (EBF) neural network is used to identify the coupled system. The structures and parameters are adaptive adjusted during the learning process, and don’t need too much expert experiences. Simulation studies show that the piezoelectric tube actuator has high authority with a broad frequency bandwidth, satisfies the requirements for helicopter vibration reduction; GD-FNN has a high learning speed, the final networks have a parsimonious network structure and generalize well, possessing broad application prospects in the helicopter vibration reduction.

Abstract: Vibration of a tube with the fluid and axial load is focused. In a heat exchanger, the tubes are frequently affected by external force and fluid shock waves. Thus, tubes are often found to be vibrated. This vibration may alter the performance of the tubes and global heat exchanger. That a heat exchanger system is weakly coupled as the each tube is coupled to the adjacent one through the fluid is found. To understand the global system dynamics, the dynamics of a tube must be investigated first. In this work, the dynamic properties of a tube with the axial loads are investigated. The Galerkin method employed, the equation of a tube with the fluid effect can be to derive. Numerical results reveal that the axial load and fluid effects may affect the dynamic properties of a tube with fluid significantly.