Shock and Vibration - Volume 18, issue 1-2

Article Type: Other

DOI: 10.3233/SAV-2010-0629

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 1-1, 2011

Authors: Jiang, Jing | Han, Qing-Kai | Li, Chao-Feng | Yao, Hong-Liang | Liu, Shu-Ying

Article Type: Research Article

Abstract: Based on the analysis on crushing process and hysteresis of material layers, a hysteretic model with symmetrical clearances is presented. The mechanical model of two-degree of freedom with bilinear hysteresis and its dynamical equations of system are proposed. In order to further investigate the dynamic characteristics of the novel vibratory cone crusher, the system is also simplified into a dynamical system of single degree of freedom with a bilinear hysteretic component together with clearances. According to …some nonlinear dynamic analysis tools such as bifurcation diagram, Lyapunov exponents, Poincare section, etc., different motion patterns of the system are discussed, including periodic, periodic doubling, chaos and other characteristics. These theoretical results will provide readers with deep understanding on the regular and complex dynamical behaviors of the vibratory cone crusher due to the hysteresis with clearances. Show more

Keywords: Vibratory cone crusher, bilinear hysteretic model with clearances, nonlinear vibration, chaos

DOI: 10.3233/SAV-2010-0568

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 3-12, 2011

Authors: Ma, Hui | Zhao, Xueyan | Teng, Yunnan | Wen, Bangchun

Article Type: Research Article

Abstract: This paper presents a finite element model of a rotor system with pedestal looseness stemming from a loosened bolt and analyzes the effects of the looseness parameters on its dynamic characteristics. When the displacement of the pedestal is less than or equal to the looseness clearance, the motion of the rotor varies from period-one through period-two and period-three to period-five with the decreasing of stiffness of the non-loosened bolts. The similar bifurcation phenomenon can be also …observed during the increasing process of the rotational speed. But the rotor motion is from period-six through period-three to period-four with the decreasing of the foundation stiffness. When the stiffness of the foundation is small and the displacement of pedestal is greater than the looseness clearance, the response of the rotor exhibits period-one and high order harmonic components with the decreasing of looseness clearance, such as 2X, 3X etc. However, when the stiffness of the foundation is great, the spectrum of the response of the rotor will be from combined frequency components to the continuous spectrum with the decreasing of the looseness clearance. Show more

Keywords: Nonlinear Vibration, rotor system, pedestal looseness, finite element method

DOI: 10.3233/SAV-2010-0588

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 13-27, 2011

Authors: Yu, Tao | Han, Qingkai

Article Type: Research Article

Abstract: With the analytic method and numerical method respectively, the asymptotic solutions and finite element model of rotor system with single slowly varying mass is obtained to investigate the time frequency features of such rotor system; furthermore, with given model of slowly varying mass, the rotor system with dual slowly varying mass is studied. For the first order approximate solution is used, there exists difference between the results with analytic method and numerical method. On the base …of common characteristics of rotor system with dual slowly varying mass, the general rules and formula describing the frequency distribution of rotor system with multiple slowly varying mass are proposed. Show more

Keywords: Rotor system, slowly varying mass, FEM, analytic method, reassigned Morlet scalograms

DOI: 10.3233/SAV-2010-0585

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 29-44, 2011

Authors: Ying, Jiayang | Jiao, Yinghou | Chen, Zhaobo

Article Type: Research Article

Abstract: The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, …cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range. Show more

Keywords: Tilting pad journal bearing, nonlinear dynamics, pad moment of inertia

DOI: 10.3233/SAV-2010-0584

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 45-52, 2011

Authors: Li, Xuejun | Shen, Yiping | Wang, Songlai

Article Type: Research Article

Abstract: The large-scale rotary machine with multi-supporting, such as rotary kiln and rope laying machine, is the key equipment in the architectural, chemistry, and agriculture industries. The body, rollers, wheels, and bearings constitute a chain multibody system. Axis line deflection is a vital parameter to determine mechanics state of rotary machine, thus body axial vibration needs to be studied for dynamic monitoring and adjusting of rotary machine. By using the Riccati transfer matrix method, the body system …of rotary machine is divided into many subsystems composed of three elements, namely, rigid disk, elastic shaft, and linear spring. Multiple wheel-bearing structures are simplified as springs. The transfer matrices of the body system and overall transfer equation are developed, as well as the response overall motion equation. Taken a rotary kiln as an instance, natural frequencies, modal shape, and response vibration with certain exciting axis line deflection are obtained by numerical computing. The body vibration modal curves illustrate the cause of dynamical errors in the common axis line measurement methods. The displacement response can be used for further measurement dynamical error analysis and compensation. The response overall motion equation could be applied to predict the body motion under abnormal mechanics condition, and provide theory guidance for machine failure diagnosis. Show more

Keywords: Multi-supporting, axis line, body vibration, anisotropy stiffness, Riccati transfer matrix method

DOI: 10.3233/SAV-2010-0573

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 53-62, 2011

Authors: Ren, Zhaohui | Zhao, Qinghua | Zhao, Chunyu | Wen, Bangchun

Article Type: Research Article

Abstract: We investigate synchronization of two asymmetric exciters in a vibrating system. Using the modified average method of small parameters, we deduce the non-dimensional coupling differential equations of the two exciters (NDDETE). By using the condition of existence for the zero solutions of the NDDETE, the condition of implementing synchronization is deduced: the torque of frequency capture is equal to or greater than the difference in the output electromagnetic torque between the two motors. Using the Routh-Hurwitz …criterion, we deduce the condition of stability of synchronization that the inertia coupling matrix of the two exciters is positive definite. A numeric result shows that the structural parameters can meet the need of synchronization stability. Show more

Keywords: Synchronization, asymmetric exciters, frequency capture, vibrating system

DOI: 10.3233/SAV-2010-0579

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 63-72, 2011

Authors: Zhao, Chunyu | Zhao, Qinghua | Gong, Zhaomin | Wen, Bangchun

Article Type: Research Article

Abstract: This paper investigates synchronization of two self-synchronous vibrating machines on an isolation rigid frame. Using the modified average method of small parameters, we deduce the non-dimensional coupling differential equations of the disturbance parameters for the angular velocities of the four unbalanced rotors. Then the stability problem of synchronization for the four unbalanced rotors is converted into the stability problems of two generalized systems. One is the generalized system of the angular velocity disturbance …parameters for the four unbalanced rotors, and the other is the generalized system of three phase disturbance parameters. The condition of implementing synchronization is that the torque of frequency capture between each pair of the unbalanced rotors on a vibrating machine is greater than the absolute values of the output electromagnetic torque difference between each pair of motors, and that the torque of frequency capture between the two vibrating machines is greater than the absolute value of the output electromagnetic torque difference between the two pairs of motors on the two vibrating machines. The stability condition of synchronization of the two vibrating machines is that the inertia coupling matrix is definite positive, and that all the eigenvalues for the generalized system of three phase disturbance parameters have negative real parts. Computer simulations are carried out to verify the results of the theoretical investigation. Show more

DOI: 10.3233/SAV-2010-0591

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 73-90, 2011

Authors: Peng, Z.K. | Lang, Z.Q. | Meng, G. | Chu, F.L.

Article Type: Research Article

Abstract: The dynamic behavior of rotor containing crack is a subject of particular interest and has been extensively investigated by researchers. The effects of crack on the natural frequencies and modal shapes and motion orbits of rotor systems have already been well explored by researchers. In the present study, the infl uence of crack on the transmission matrices of the rotor systems is investigated by using the FEM (finite element method) analysis and the HBM (harmonic balance …method) technique. It is for the first time revealed that there are differences between the transmission matrices for the fundamental frequency components and the transmission matrices for the super-harmonic components, and the differences are mainly determined by the crack location. The results are validated by numerical experiments where the system responses of a rotor system are obtained using {\it Runge-Kutta} method. The results are of significance for the development of effective crack detection methods in practice. Show more

Keywords: Crack detection, rotor systems, nonlinear vibration, harmonic balance method, transmission matrix

DOI: 10.3233/SAV-2010-0564

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 91-103, 2011

Authors: Cao, Dengqing | Gong, Xiaochun | Wei, Dong | Chu, Shiming | Wang, Ligang

Article Type: Research Article

Abstract: An approximate approach is proposed in this paper for analyzing the two-dimensional friction contact problem so as to compute the dynamic response of a structure constrained by friction interfaces due to tip-rub. The dynamical equation of motion for a rotational cantilever blade in a centrifugal force field is established. Flow-induced distributed periodic forces and the internal material damping in the blade are accounted for in the governing equation of motion. The Galerkin method is employed to …obtain a three-degree-of-freedom oscillator with friction damping due to tip-rub. The combined motion of impact and friction due to tip-rub produced a piecewise linear vibration which is actually nonlinear. Thus, a complete vibration cycle is divided into successive intervals. The system possesses linear vibration characteristic during each of these intervals, which can be determined using analytical solution forms. Numerical simulation shows that the parameters such as gap of the tip and the rotational speed of the blades have significant effects on the dynamical responses of the system. Finally, the nonlinear vibration characteristics of the blade are investigated in terms of the Poincare graph, and the frequency spectrum of the responses and the amplitude-frequency curves. Show more

Keywords: Nonlinear vibration, flexible blade, friction damping, tip-rub, impact

DOI: 10.3233/SAV-2010-0600

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 105-114, 2011

Authors: Lu, Wenxiu | Chu, Fulei

Article Type: Research Article

Abstract: The shaft crack is one of the main serious malfunctions that often occur in rotating machinery. However, it is difficult to locate the crack and determine the depth of the crack. In this paper, the acoustic emission (AE) signal and vibration response are used to diagnose the crack. The wavelet transform is applied to AE signal to decompose into a series of time-domain signals, each of which covers a specific octave frequency band. Then an improved …union method based on threshold and cross-correlation method is applied to detect the location of the shaft crack. The finite element method is used to build the model of the cracked rotor, and the crack depth is identified by comparing the vibration response of experiment and simulation. The experimental results show that the AE signal is effective and convenient to locate the shaft crack, and the vibration signal is feasible to determine the depth of shaft crack. Show more

Keywords: Shaft crack identification, acoustic emission, vibration, wavelet transform, cross-correlation, finite element method

DOI: 10.3233/SAV-2010-0580

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 115-126, 2011

Authors: Jiang, Lingli | Liu, Yilun | Li, Xuejun | Chen, Anhua

Article Type: Research Article

Abstract: This paper proposes a new approach combining autoregressive (AR) model and fuzzy cluster analysis for bearing fault diagnosis and degradation assessment. AR model is an effective approach to extract the fault feature, and is generally applied to stationary signals. However, the fault vibration signals of a roller bearing are non-stationary and non-Gaussian. Aiming at this problem, the set of parameters of the AR model is estimated based on higher-order cumulants. Consequently, the AR parameters are taken …as the feature vectors, and fuzzy cluster analysis is applied to perform classification and pattern recognition. Experiments analysis results show that the proposed method can be used to identify various types and severities of fault bearings. This study is significant for non-stationary and non-Gaussian signal analysis, fault diagnosis and degradation assessment. Show more

Keywords: Degradation assessment, Fault diagnosis, AR mode, Higher-order statistics, Fuzzy cluster analysis

DOI: 10.3233/SAV-2010-0572

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 127-137, 2011

Authors: Zhang, Nan | Liu, Ying | Chu, Fulei

Article Type: Research Article

Abstract: Flow induced vibration is an important factor affecting the performance of the rotor-seal system. From the point of view of flow induced vibration, the nonlinear models of the rotor-seal system are presented for the analysis of the fluid force, which is induced by the interaction between the unstable fluid flow in the seal and the vibrating rotor. The nonlinear characteristics of flow induced vibration in the rotor-seal system are analyzed, and the nonlinear phenomena in the …unbalanced rotor-seal system are investigated using the nonlinear models. Various nonlinear phenomena of flow induced vibration in the rotor-seal system, such as synchronization phenomenon and amplitude mutation, are reproduced. Show more

Keywords: Flow induced vibration, rotor-seal system, synchronization phenomenon, amplitude mutation

DOI: 10.3233/SAV-2010-0601

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 139-146, 2011

Authors: Hiwarkar, Vikrant R. | Babitsky, Vladimir I. | Silberschmidt, Vadim V.

Article Type: Research Article

Abstract: The presence of a crack in a structure affects its dynamic behaviour under working conditions. Cracks introduce nonlinearities into the system; the use of such nonlinearities for damage detection should be investigated. A model of a one-dimensional cracked cantilever bar subjected to longitudinal harmonic excitation is used to analyse a vibro-impact response as a way to monitor structural health. The effect of contact nonlinearity due to crack's faces interaction is considered. This nonlinear information is obtained …based on a combination of the analytical technique and the Matlab-Simulink computation. The procedure uses a numerical approximation for dynamic compliance operators and a nonlinear model of contact faces interaction implemented numerically as a nonlinear feedback. Nonlinear resonant phenomena due to vibro-impact interaction in the cracked bar are obtained and analysed. A distribution of the higher harmonics along the bar length, generated due to the nonlinear response of the crack, is revealed as a function of the distance from the crack. Recommendations on structural health monitoring of cracked bars due to contact nonlinearity are presented Show more

Keywords: Vibro-impact, nonlinear vibration, crack monitoring

DOI: 10.3233/SAV-2010-0590

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 147-156, 2011

Authors: Ashcroft, Ian A. | Silberschmidt, Vadim V. | Echard, Benjamin | Rodriguez, Juan Pablo Casas

Article Type: Research Article

Abstract: Adhesives are being increasingly used in structural applications, especially in aerospace, automotive and naval structures, making their structural integrity an important issue. In-service loading histories of such structures usually contain low-energy impacts, repetition of which can significantly affect their performance. This paper deals with the behaviour of the toughened epoxy adhesive FM73 under repeated impacts, known as impact fatigue. Izod impact fatigue tests were performed on FM73 specimens in order to study …the evolution of damage and to characterise this via measurable parameters, such as the maximum force and the contact time. A finite element model was developed to simulate the impact tests and this was used to calculate the dynamic strain energy release rate, which was compared with that determined using a simple analytical method. A relationship between the maximum dynamic strain energy release rate and impact fatigue crack growth rate was established that was used as the basis of an impact fatigue crack growth law. Show more

Keywords: Dynamic strain energy release rate, impact fatigue, crack propagation, adhesive, fracture mechanics, Izod test

DOI: 10.3233/SAV-2010-0607

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 157-170, 2011

Authors: Song, Hua | Wang, Peilong | Fu, Lihua | Chen, Ming | Wang, Zhongqiang | Sun, Huiyuan

Article Type: Research Article

Abstract: Residual stress is very important to the straightened quality of rail, this paper adopts explicit dynamics FEM to study on residual stress. We established compound roller model and calculated the residual value of heavy rail through 9 roller horizontal straightening and 8 roller vertical straightening. The reductions of straightening rollers are taken as the main effective factor to the residual stress in the straightening process. We adopt orthogonal calculation method to obtain the main effective factor …to residual stress. On the base of assurance of the straightness, we obtained the optimal regulation in which the residual stress is the smallest, so the paper makes the important theoretical and actual sense to formulate the rational straightening regulation and improve the straightening quality of rail. Show more

Keywords: Heavy rail, compound straightening, numerical simulation, residual stress

DOI: 10.3233/SAV-2010-0599

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 171-180, 2011

Authors: Azoulay, Michel | Veprik, Alexander | Babitsky, Vladimir | Halliwell, Neil

Article Type: Research Article

Abstract: An approach to a wide-band frequency passive vibration attenuation is introduced in this paper. This aims to suppress noise and vibration of extended multimode objects like plates, panels and shells. The absorber is arranged in the form of a single-layer assembly of small inertial bodies (balls) being distributed and moulded within the light visco-elastic media (e.g. silicone resin). The absorber as a whole is embedded into object face covering the critical patches of the system surface. …For the purpose of characterization, the authors introduced the complex frequency response function relating the volume velocity produced by the vibrating object surface (response) stimulated by a point-wise force (stimulus) applied to a particular point. The simulation and optimization of the main frequency characteristics has been performed using a full scale 3-dimensional Finite Element model. These revealed some new dynamic features of absorber's structures, which can contribute to vibration attenuation. A full-scale physical experimentation with synthesised absorber's structures confirmed the main results of simulation and has shown significant noise reduction over a staggering 0–20 kHz frequency band. This was achieved with a negligible weight and volume penalty due to the addition of the absorber. The results can find multiple applications in noise and vibration control of different structures. Some examples of such applications are presented. Show more

Keywords: Noise and vibration control, passive vibration attenuation, wide frequency band absorber

DOI: 10.3233/SAV-2010-0608

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 181-219, 2011

Authors: Ling, Zheng | Ronglu, Xie | Yi, Wang | El-Sabbagh, Adel

Article Type: Research Article

Abstract: Damping treatments have been extensively used as a powerful means to damp out structural resonant vibrations. Usually, damping materials are fully covered on the surface of plates. The drawbacks of this conventional treatment are also obvious due to an added mass and excess material consumption. Therefore, it is not always economical and effective from an optimization design view. In this paper, a topology optimization approach is presented to maximize the modal damping ratio of the plate …with constrained layer damping treatment. The governing equation of motion of the plate is derived on the basis of energy approach. A finite element model to describe dynamic performances of the plate is developed and used along with an optimization algorithm in order to determine the optimal topologies of constrained layer damping layout on the plate. The damping of visco-elastic layer is modeled by the complex modulus formula. Considering the vibration and energy dissipation mode of the plate with constrained layer damping treatment, damping material density and volume factor are considered as design variable and constraint respectively. Meantime, the modal damping ratio of the plate is assigned as the objective function in the topology optimization approach. The sensitivity of modal damping ratio to design variable is further derived and Method of Moving Asymptote (MMA) is adopted to search the optimized topologies of constrained layer damping layout on the plate. Numerical examples are used to demonstrate the effectiveness of the proposed topology optimization approach. The results show that vibration energy dissipation of the plates can be enhanced by the optimal constrained layer damping layout. This optimal technology can be further extended to vibration attenuation of sandwich cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles as an invaluable design tool. Show more

Keywords: Topology optimization, sensitivity, Method of Moving Asymptote

DOI: 10.3233/SAV-2010-0583

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 221-244, 2011

Authors: Inoue, Masanobu | Yokomichi, Isao | Hiraki, Koju

Article Type: Research Article

Abstract: A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF) structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. …To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF) system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range. Show more

Keywords: Vibration suppression, particle damper, multi degree of freedom system, modal analysis, periodic motion

DOI: 10.3233/SAV-2010-0611

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 245-256, 2011

Authors: Wang, Z. H. | Du, M. L.

Article Type: Research Article

Abstract: Fractional-order derivative has been shown an adequate tool to the study of so-called "anomalous" social and physical behaviors, in reflecting their non-local, frequency- and history-dependent properties, and it has been used to model practical systems in engineering successfully, including the famous Bagley-Torvik equation modeling forced motion of a rigid plate immersed in Newtonian fluid. The solutions of the initial value problems of linear fractional differential equations are usually expressed in terms of …Mittag-Leffler functions or some other kind of power series. Such forms of solutions are not good for engineers not only in understanding the solutions but also in investigation. This paper proves that for the linear SDOF oscillator with a damping described by fractional-order derivative whose order is between 1 and 2, the solution of its initial value problem free of external excitation consists of two parts, the first one is the 'eigenfunction expansion' that is similar to the case without fractional-order derivative, and the second one is a definite integral that is independent of the eigenvalues (or characteristic roots). The integral disappears in the classical linear oscillator and it can be neglected from the solution when stationary solution is addressed. Moreover, the response of the fractionally damped oscillator under harmonic excitation is calculated in a similar way, and it is found that the fractional damping with order between 1 and 2 can be used to produce oscillation with large amplitude as well as to suppress oscillation, depending on the ratio of the excitation frequency and the natural frequency. Show more

Keywords: Linear oscillator, fractional-order damping, characteristic root, eigenfunction expansion

DOI: 10.3233/SAV-2010-0566

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 257-268, 2011

Authors: You, Jin | Li, Hong-Guang | Meng, Guang

Article Type: Research Article

Abstract: The validity of the application of energy flow analysis for beam structures under random excitations is investigated in this paper. The approximate solutions of energy density and intensity in a beam subject to random loadings are obtained by solving the governing equation of random energy flow analysis using Fourier transform technique. The formulations of the exact energy density distribution and intensity in the beam are derived using the classical modal analysis method. For a simply supported …beam subject to distributed or concentrated random excitations, the validity of random energy flow analysis is investigated through comparisons between solutions obtained from the approximate and exact methods for energy response as well as intensity. The results indicate that, the mode count of the analysis frequency band, which means the number of modes involved in the band, is the key factor affecting the prediction accuracy of random energy flow analysis, and that if the mode count of the band is sufficiently large, random energy flow analysis can provide rather accurate estimates for both energy density and intensity in a wide frequency range. Show more

Keywords: Random energy flow analysis (random EFA), random excitation, energy density, intensity, beam structure

DOI: 10.3233/SAV-2010-0567

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 269-280, 2011

Authors: Ding, Hu | Chen, Li-Qun

Article Type: Research Article

Abstract: Nonlinear models of transverse vibration of axially moving viscoelastic beams subjected external transverse loads via steady-state periodical response are numerically investigated. An integro-partial-differential equation and a partial-differential equation of transverse motion can be derived respectively from a model of the coupled planar vibration for an axially moving beam. The finite difference scheme is developed to calculate steady-state response for the model of coupled planar and the two models of transverse motion under …the simple support boundary. Numerical results indicate that the amplitude of the steady-state response for the model of coupled vibration and two models of transverse vibration predict qualitatively the same tendencies with the changing parameters and the integro-partial-differential equation gives results more closely to the coupled planar vibration. Show more

Keywords: Vibration, nonlinearity, axially moving beam, viscoelasticity, finite difference

DOI: 10.3233/SAV-2010-0586

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 281-288, 2011

Authors: Yang, Ying | Zhao, Guangyao | Ma, Dongbo | Xu, Xiaobin

Article Type: Research Article

Abstract: The dynamic parameters of a car body in white (BIW) are important during a new car developing. Based on the finite element method, the model of a BIW is developed in which the welding points are treated specially as a new element type and the vibration modes of it are calculated. In modal testing, a fixed sine-sweeping exciter is used to conduct a single-point input force for the structure, whereas the output responses are picked up at different points …to identify modes. The obtained modes are coincided both with the FE results and the practical testing. Show more

Keywords: Vibration modes, finite element method, model testing

DOI: 10.3233/SAV-2010-0604

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 289-298, 2011

Authors: Peng, Z. K. | Meng, G. | Chu, F. L.

Article Type: Research Article

Abstract: The present work carries out a comprehensive investigation into the border distortion deficiency for the conventional scalogram and the reassigned scalogram. The reasons for this deficiency are analyzed, and a simple way is suggested to determine the border distortion ranges. New methods are proposed to reduce the border distortions in both the scalograms. The practical meanings of the border distortion improvement method are demonstrated by applying both the scalograms with and without border distortion improvements to …estimate the modal parameters for a 2-DOF linear system. The estimation results indicate that, in the presence of noise, which is inevitable in practice, for the mode with weak amplitude, the reassigned scalogram can perform better than the conventional scalogram in estimating the modal parameters. In addition, for the mode with short effective duration, its frequency components at the border distortion ranges are of great importance for the modal parameter estimation purpose, and the border distortion improvement method can greatly increase the estimation accuracy. Show more

Keywords: Wavelet transform, border distortion, edge effect, modal analysis, scalogram, reassigned scalogram

DOI: 10.3233/SAV-2010-0574

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 299-316, 2011

Authors: Si, Xiaohui | Lu, Wenxiu | Chu, Fulei

Article Type: Research Article

Abstract: The variations of the supporting condition, which change the stiffness of tilting pad thrust bearing, may alter the dynamic behavior of the rotor system. The effects of supporting condition of thrust pad on the lateral vibration of a hydroelectric generating set are investigated in this paper. The action of a thrust bearing is described as moments acting on the thrust collar, and the tilting stiffness coefficients of thrust bearing are calculated. A model based on typical …beam finite element method is established to calculate the dynamic response, and the effects of supporting conditions such as elastic oil tank support, different heights of the thrust pads with rigid support are discussed. The results reveal that the influence of thrust bearing is small when the elastic oil tanks work normally. When the supporting conditions turn to be rigid due to the oil leakage, the differences of thrust pad heights have evident influence on the load distribution of the thrust pads; while the effects on the tilting stiffness of the thrust bearing and the amplitude of the lateral shaft vibration is small when the maximum load on thrust pads is smaller than the allowable value. Show more

Keywords: Rotor dynamics, thrust bearing, lateral vibration, tilting stiffness

DOI: 10.3233/SAV-2010-0569

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 317-331, 2011

Authors: Volkov, G.A. | Bratov, V.A. | Gruzdkov, A.A. | Babitsky, V.I. | Petrov, Yu.V. | Silberschmidt, V.V.

Article Type: Research Article

Abstract: The process of ultrasonically-assisted turning (UAT) is a superposition of vibration of a cutting tool on its standard movement in conventional turning (CT). The former technique has several advantages compared with the latter, one of the main being a significant decrease in the level of cutting forces. In this paper the effects observed in UAT are analysed employing ideas of dynamic fracture mechanics. The active stage of loading duration depends heavily on ultrasonic frequency and the …cutting speed; he application of the fracture criterion based on the notion of incubation time makes it possible to calculate a dependence of this duration on its threshold amplitude. An estimation of energy, necessary to create a threshold pulse in the material, is made by solving the contact Hertz problem. The obtained time dependence of energy has a marked minimum. Thus, the existence of energy-efficient loading duration is demonstrated. This explains the decrease in the cutting force resulting from superimposed ultrasonic vibration. The obtained results are in agreement with experiments on ultrasonic assisted machining of aluminium and Inconel 718 alloy. Show more

Keywords: Ultrasonically-assisted turning, fracture energy, fracture criterion

DOI: 10.3233/SAV-2010-0606

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 333-341, 2011

Authors: Zhang, Zhiyi | Chen, Yong | Li, Hongguang | Hua, Hongxing

Article Type: Research Article

Abstract: FEM/BEM is adopted to model the interaction between the fluid and structures. In the modeling, modal truncation and inertial coupling are applied to sufficiently reduce the coupled model order. This approach is adopted for the purpose of constructing a modal model in the time domain. Active vibration control is realized with piezoelectric actuators and an adaptive method. In the control, the summation of vibration responses is used as the control error since the integral of acceleration …on the plate surface is approximately proportional to the far field sound pressure. A rigidly baffled plate connected with a mass through one piezoelectric actuator is simulated at first. In the experiment, the plate is excited by a rotating eccentric mass and controlled with four piezoelectric actuators. The results have shown that active vibration control with the piezoelectric actuators can lead to a noticeable attenuation in sound pressure. Show more

Keywords: Fluid-structure interaction, piezoelectric actuator, adaptive vibration control, sound radiation

DOI: 10.3233/SAV-2010-0565

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 343-354, 2011

Authors: Luo, Zhong | Yang, Shuxian | Sun, Yilan | Liu, Hongyi

Article Type: Research Article

Abstract: In this paper, the dynamical performance of polishing robot working in unstructured environment is investigated. Structure mechanism and operating principle of a polishing robot are introduced firstly, and its dynamical model is established. Then, a S-shaped acceleration-deceleration path planning method and a human-simulated intelligent control (HSIC) strategy are proposed. The S-shaped acceleration-deceleration path planning method is to switch the magnitude and direction of the abrupt velocities between motion sections in order to …improve the work efficiency, the smoothness of movement and the processing accuracy. The HSIC control strategy is built based on the unstructured environment information measured by ultrasonic sensors, in which the appropriate programs prepared in advance are determined according to the size and sign of both the control error and its change rate. Simulation results show that the intelligent control strategy combining with optimum path planning method are effective to reduce the structure vibration, to improve the stability and the control accuracy of the polishing robot system. Show more

Keywords: Polishing robot, unstructured environment, path planning, human-simulated intelligent control (HSIC)

DOI: 10.3233/SAV-2010-0603

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 355-364, 2011

Authors: Han, Qingkai | Zhao, Xueyan | Li, Xingxiu | Wen, Bangchun

Article Type: Research Article

Abstract: In this paper, we investigate the joint viscous friction effects on the motions of a two-bar linkage under controlling of OPCL. The dynamical model of the two-bar linkage with an OPCL controller is firstly set up with considering the two joints' viscous frictions. Thereafter, the motion bifurcations of the two-bar linkage along the values of joint viscous frictions are obtained using shooting method. Then, single-periodic, multiple-periodic, quasi-periodic and chaotic motions of link rotating angles are simulated …with given different viscous friction values, and they are illustrated in time domain waveforms, phase space portraits, amplitude spectra and Poincare mapping graphs, respectively. Additionally, for the chaotic case, Lyapunov exponents and hypothesis possibilities of the two joint motions are also estimated. Show more

Keywords: Two-bar linkage system, OPCL controller, viscous friction, motion bifurcation, chaos

DOI: 10.3233/SAV-2010-0571

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 365-375, 2011

Authors: Li, Xinye | Zhang, Huabiao | Zhang, Lijuan

Article Type: Research Article

Abstract: In this paper, the dynamics of Duffing-van der Pol oscillators under linear-plus-nonlinear position feedback control with two time delays is studied analytically and numerically. By the averaging method, together with truncation of Taylor expansions for those terms with time delay, the slow-flow equations are obtained from which the trivial and nontrivial solutions can be found. It is shown that the trivial solution can be stabilized by appropriate gain and time delay in linear feedback although it …loses its stability via Hopf bifurcation and results in periodic solution for uncontrolled systems. And the stability of the trivial solution is independent of nonlinear feedback. Different from the case of the trivial solution, the stability of nontrivial solutions is also associated with nonlinear feedback besides linear feedback. Non-trivial solutions may lose their stability via saddle-node or Hopf bifurcation and the resulting response of the system may be quasi-periodic or chaotic. The feedback gains and time delays have great effects on the amplitude of the periodic solutions and their bifurcation control. The simulations, obtained by numerically integrating the original system, are in good agreement with the analytical results. Show more

DOI: 10.3233/SAV-2010-0570

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 377-386, 2011

Authors: Zhang, Yimin

Article Type: Research Article

Abstract: On the basis of the Bouc-Wen hysteretic model, the effective numerical method for the response of nonlinear multi-degree-of-freedom (MDOF) stochastic hysteretic systems is presented using second moment method. Using this method, the mean values, variances and covariances are computed. The Monte Carlo simulation is applied to validate the method. The results obtained by the two methods are contrasted, and the solutions of the method in this paper agreed very well with the Monte Carlo simulation. It …has solved the random response of nonlinear stochastic vibration systems which is caused by the stochastic hysteretic loop itself. Show more

DOI: 10.3233/SAV-2010-0581

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 387-396, 2011

Authors: Zhang, Zhiwei | Singh, Rajendra | Crowther, Ashley R.

Article Type: Research Article

Abstract: Nonlinear torsional models are used to analyze automotive transmission rattle problems and find solutions to reduce noise, vibration and dynamic loads. The torsional stiffness and inertial distribution of such systems show that the underlying mathematical problem is numerically stiff. In addition, the clearance nonlinearities in the gear meshes introduce discontinuous functions. Both factors affect the efficacy of time domain integration and smoothening functions are widely used to overcome computational difficulties and improve …the simulation. In this paper, alternate smoothening functions are studied for their influence on the numerical solutions and their impact on global convergence and computation times. In particular, four smoothening functions (arctan, hyperbolic-cosine, hyperbolic-tan and quintic-spline) are applied to a five-degree-of-freedom generic torsional system with two backlash (clearance) elements. Each function is assessed via a global convergence metric across an excitation map (a design of experiment). Regions of the excitation map, along with multiple solutions, are studied and the implications to assessing convergence are critically examined.~ It is observed that smoothening functions do not lead to better convergence in many cases. The smoothening parameter needs to be carefully selected, or over-smoothened solutions may be found. The system studied is representative of a typical automotive rattle problem and it was found that benefits were limited from applying such smoothening functions. Show more

Keywords: Vibro-impact systems, non-smooth dynamics, computational issues, smoothening functions, automotive gear rattle

DOI: 10.3233/SAV-2010-0582

Citation: Shock and Vibration, vol. 18, no. 1-2, pp. 397-406, 2011