Applied Mechanics and Materials Vols. 105-107

Abstract: A system of cantilever beam coupled with moving mass is investigated in this paper. Based on the time varying feature of multibody system, a dynamic model of the mass moving along the cantilever beam is established. The time varying motion equation including time varying mass and stiffness is derived by using the generalized Hamiltion’s principle, which results to a partial differential equation with variable coefficients. The nonlinearity of the equation is featured by those variable coefficients. To deal with the nonlinearity, methods of assumed modal shapes, Runge-Kutta are occupied. Then, a time varying system of a cantilever beam with stepwise sections coupled with a moving mass is given as an example. Numerical solutions of the dynamic responses of the system are achieved and certain analyses are made in the form of graphs.

Abstract: Piezoelectric materials generate electricity when they are subjected to mechanical strain. This paper presents an innovative design platform of piezoelectric energy harvester with variable curvatures and sections. Firstly, the effects of the proof mass position on the spiral laminated beam with PZT-5H bonded on the surface are analyzed. Secondly, the dynamical performances of the piezoelectric harvester with different shape are investigated. The results, which are gotten through ANSYS software, show that the first three order natural frequencies increase linearly while the distance from the free end increases. The voltage distribution variates acutely because of the coupling of the bending and twisting actions in the beam. The simulation data will provide a theory analysis foundation for the engineering, design and application of harvester.

Abstract: The target of the paper is modeling of the influence of small amount of free gas on pressure wave propagation in a cylindrical elastic shell, filled with viscous liquid. Heterogeneity of the bubble population and the basic sources of wave attenuation (wall friction, heat exchange between gas in microbubbles and surrounding liquid, viscous and acoustic losses) are taken into account. The dispersion equation for the waveguide is studied numerically and effect of the bubble size distribution on the longitudinal wave propagation is discussed.

Abstract: This paper discusses the method of vibration spectral analysis to get characters of wire bonder, based on the work principle and character of wire bonder. Vibration signals are acquired by vibration sensors, and Dewetron data-acquisition system has been used for the data analysis to get spectrum. From the spectrum of vibration signal, the main frequency and corresponding amplitude have been acquired. Amplitude of main frequency at different working condition on the same machine is compared by figures. The results show that machine 1&2 has almost the same vibration at the workbench, although machine 2 has bigger local vibration than machine 1. It can be concluded that the much bigger local vibration has less effect on the quality of parts in this case.

Abstract: Tire noise is classified by pattern noise and road noise in a vehicle. Especially pattern noise has impulsive characteristics since it is generated by impacting of tire’s block on the road. Therefore, a special signal process is needed other than traditional Fourier Transform, because the characteristic of signal is varying with time. On the other hand, the pattern noise is a kind of non-stationary signal and is related to the impulsive train of pitch sequence of a block. In this paper, Wavelet Transform is applied to verify the impulse signal caused by impact of block and groove and to verify the relationship between the pattern noise and the train of pitch sequence.

Abstract: The frequency–amplitude relationship of coupled anharmonic oscillators is an important problem. Many powerful methods for solving this problem have been proposed. He’s parameter-expanding method is an important one. It holds the advantages of modified Lindstedt–Poincare parameter method and bookkeeping parameter method. The first iteration is enough. It is very effective and convenient and quite accurate to both linear and nonlinear problems. In this paper, He’s parameter-expanding method is applied to coupled anharmonic oscillators. The frequency-amplitude relationship and the first-order approximate solution of the oscillators are obtained respectively. The solution procedure shows that the method is very powerful and convenient to nonlinear oscillator. This method has great potential and can be applied to other types of nonlinear oscillator problems.

Abstract: A certain type of Remote Control Weapon Station is a complex structural system. The main reason of affecting the firing accuracy of weapons of the RCWS is the structural vibration. If there are several components with the similar natural frequency, they will influence each other and there is a possibility of resonance. For the poor firing accuracy of the Remote Control Weapon Station, the mode simulation and mode match analysis is done with the application of the complex structural system mode match analysis theory and by using the advanced finite element analysis software -Workbench, to get the conclusion that the kickstand design which is used to stabilify the weapon barrel need to be improved. That can provide theoretical guidance and technical support for the remote weapon station firing accuracy and stability improvement.

Abstract: Phononic Crystals (PCs) have important potential application in engineering by the properties of bandgaps. In the paper, the bandgap characteristic of one-dimensional PCs is attributed to the results of Single-Negative (SN) properties, e.g. negative modulus or negative density. The effective parameters of the 1D PCs were predicted by the equivalent layer concept with considering viscous damping, and the results showed that during the frequency regions of the bandgaps, the negative parameters appeared. This will be a reference for the design of acoustic negative refraction metamaterials.

Abstract: This study is trying to find kinematics differences between on-water rowing and its simulation on Concept2 ergometer, and explain biomechanical differences between on-water rowing and its simulation on Concept2 ergometer, which can affect the rowers motor control pattern and their on-water rowing technique. Positions of the handle, seat and trunk, shell acceleration were measured in single scull on both machines and on-water in four female rowers. It was found there is about 60-80% similarity between on-ergo and on-water rowing, the drive length on Concept2 ergometer is 10%-12% shorter than on-water, the stroke rate on-water is 10-15% higher than on Concept2 ergometer, legs drive was 4-6% longer on Concept2 ergometer than on-water. Significant differences were found in the handle velocity and shell acceleration profiles. Machines should be considered as a cross-training for rowers and can’t replace on-water rowing.

Abstract: The hydraulic long-straight pipeline system of the shield machine is to be studied in this paper. Modal parameters of the hydraulic long-straight pipeline whose length is 8m under three kinds of spans (single span, double spans and four spans) were measured and analyzed. Considering the inherent vibration characteristics of the shield machine, we limited the natural frequency of the multi-span long straight pipeline studied within the range of 0~ 200Hz.What the experiment shows is as follows: Firstly, the natural frequency of the hydraulic long-straight pipeline is densely distributed mainly in the low frequency; Secondly, the natural frequencies of vibration in the horizontal plane are slightly higher than those of corresponding orders in the vertical plane, although the difference is little; In addition, by increasing the number of supports, pipeline span can be reduced and the natural frequencies of pipeline can be significantly increased, but this will make the vibration mode change irregularly.