Shock and Vibration http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Analytical Study on Dynamic Response of Deep Foundation Pit Support Structure under the Action of Subway Train Vibration Load: A Case Study of Deep Foundation Pit of the New Museum Near Metro Line 2 in Chengdu, China Thu, 27 Aug 2015 07:58:33 +0000 http://www.hindawi.com/journals/sv/2015/535196/ Presently, foundation pit support structures are generally regarded as the temporary structures and the impact of vibration loads is often overlooked. As opposed to static and seismic loads, the vibration loads of subway trains are a type of cyclic load with a relatively long duration of action and a definite cycle; it is of great importance for the design of foundation pit support structures to correctly evaluate the impact of subway train vibrations on deep foundation pit and support works. In this paper, a dynamic three-dimensional numerical model is built that considers the vibration load of subway trains on the basis of the static numerical model for deep foundation pit support structures and simplified train loads to study the impact of train vibrations on deep foundation pit and permanent support structures. Studies have shown that the dynamic response of surface displacement mainly occurs in the early period of dynamic load, the vibration load of subway trains has little impact on ground subsidence, the support pile structure is in an elastic state during dynamic response under the action of subway train vibrations, and the action of train vibration loads is inimical to the safety of foundation pit support structures and should be closely studied. Zhu Dapeng, Qin Liangkai, and Lin Yundian Copyright © 2015 Zhu Dapeng et al. All rights reserved. Forced Transverse Vibration of a Closed Double Single-Walled Carbon Nanotube System Containing a Fluid with Effect of Compressive Axial Load Tue, 25 Aug 2015 14:19:18 +0000 http://www.hindawi.com/journals/sv/2015/435284/ Based on the Rayleigh beam theory, the forced transverse vibrations of a closed double single-walled carbon nanotube (SWCNT) system containing a fluid with a Pasternak layer in-between are investigated. It is assumed that the two single-walled carbon nanotubes of the system are continuously joined by a Pasternak layer and both sides of SWCNTs containing a fluid are closed. The dynamic responses of the system caused by arbitrarily distributed continuous loads are obtained. The effect of compressive axial load on the forced vibrations of the double single-walled carbon nanotube system is discussed for one case of particular excitation loading. The properties of the forced transverse vibrations of the system are found to be significantly dependent on the compressive axial load. The steady-state vibration amplitudes of the SWCNT decrease with increasing of length of SWCNT. Vibrations caused by the harmonic exciting forces are discussed, and conditions of resonance and dynamic vibration absorption are formulated. The SWCNT-type dynamic absorber is a new concept of a dynamic vibration absorber (DVA), which can be applied to suppress excessive vibrations of corresponding SWCNT systems. Mehrdad Nasirshoaibi, Nader Mohammadi, and Masih Nasirshoaibi Copyright © 2015 Mehrdad Nasirshoaibi et al. All rights reserved. An Enhanced Piezoelectric Vibration Energy Harvesting System with Macro Fiber Composite Tue, 25 Aug 2015 09:26:22 +0000 http://www.hindawi.com/journals/sv/2015/916870/ Self-power supply is a promising project in various applied conditions. Among this research area, piezoelectric material-based energy harvesting (EH) method has been researched in recent years due to its advantages. With the limitation of energy form acceptance range of EH circuit system, a sum of energy is not accessible to be obtained. To enlarge the EH quantity from the vibration, an enhanced piezoelectric vibration EH structure with piezoelectric film is developed in this work. Piezoelectric-based energy harvesting mechanism is primarily proposed in this work. The special-designed electric circuit for EH from macro fiber composite (MFC) is proposed and then analyzed. When the structure vibrates in its modes of frequencies, the experiments are developed to measure the EH effect. The energy harvested from the vibrating structure is analyzed and the enhanced effect is presented. The results indicate that, with the enhanced EH structure in this work, vibration energy from structure is obtained in a larger range, and the general EH quantity is enlarged. Shuwen Zhang, Bo Yan, Yajun Luo, Weikai Miao, and Minglong Xu Copyright © 2015 Shuwen Zhang et al. All rights reserved. Characterizing the Dynamic Response of a Chassis Frame in a Heavy-Duty Dump Vehicle Based on an Improved Stochastic System Identification Mon, 24 Aug 2015 12:12:28 +0000 http://www.hindawi.com/journals/sv/2015/374083/ This paper presents an online method for the assessment of the dynamic performance of the chassis frame in a heavy-duty dump truck based on a novel stochastic subspace identification (SSI) method. It introduces the use of an average correlation signal as the input data to conventional SSI methods in order to reduce the noisy and nonstationary contents in the vibration signals from the frame, allowing accurate modal properties to be attained for realistically assessing the dynamic behaviour of the frame when the vehicle travels on both bumped and unpaved roads under different operating conditions. The modal results show that the modal properties obtained online are significantly different from the offline ones in that the identifiable modes are less because of the integration of different vehicle systems onto the frame. Moreover, the modal shapes between 7 Hz and 40 Hz clearly indicate the weak section of the structure where earlier fatigues and unsafe operations may occur due to the high relative changes in the modal shapes. In addition, the loaded operations show more modes which cause high deformation on the weak section. These results have verified the performance of the proposed SSI method and provide reliable references for optimizing the construction of the frame. Zhi Chen, Tie Wang, Fengshou Gu, and Ruiliang Zhang Copyright © 2015 Zhi Chen et al. All rights reserved. Free-Form Optimization of Thin-Walled Structure for Frequency Response Problem Mon, 24 Aug 2015 06:18:41 +0000 http://www.hindawi.com/journals/sv/2015/471646/ We present a node-based free-form optimization method for designing forms of thin-walled structures in order to control vibration displacements or mode at a prescribed frequency. A squared displacement error norm is introduced at the prescribed surface as the objective functional to control the vibration displacements to target values in a frequency response problem. It is assumed that the thin-walled structure is varied in the normal direction to the surface and the thickness is constant. A nonparametric shape optimization problem is formulated, and the shape gradient function is theoretically derived using the material derivative method and the adjoint variable method. The shape gradient function obtained is applied to the surface of the thin-walled structure as a fictitious traction force to vary the form. With this free-form optimization method, an optimum thin-walled structure with a smooth free-form surface can be obtained without any shape parameterization. The calculated results show the effectiveness of the proposed method for the optimal free-form design of thin-walled structures with vibration mode control. Masatoshi Shimoda and Yang Liu Copyright © 2015 Masatoshi Shimoda and Yang Liu. All rights reserved. Dynamic Assessment of Vibration of Tooth Modification Gearbox Using Grey Bootstrap Method Thu, 20 Aug 2015 14:03:47 +0000 http://www.hindawi.com/journals/sv/2015/204609/ The correlation analysis between gear modification and vibration characteristics of transmission system was difficult to quantify; a novel small sample vibration of gearbox prediction method based on grey system theory and bootstrap theory was presented. The method characterized vibration base feature of tooth modification gearbox by developing dynamic uncertainty, estimated true value, and systematic error measure, and these parameters could indirectly dynamically evaluate the effect of tooth modification. The method can evaluate the vibration signal of gearbox with installation of no tooth modification gear and topological modification gear, respectively, considering that 100% reliability is the constraints condition and minimum average uncertainty is the target value. Computer simulation and experiment results showed that vibration amplitude of gearbox was decreased partly due to topological tooth modification, and each value of average dynamic uncertainty, mean true value, and systematic error measure was smaller than the no tooth modification value. The study provided an important guide for tooth modification, dynamic performance optimization. Hui-liang Wang, Xiao-zhong Deng, Ju-bo Li, and Jian-jun Yang Copyright © 2015 Hui-liang Wang et al. All rights reserved. Uncertainty Reduced Novelty Detection Approach Applied to Rotating Machinery for Condition Monitoring Thu, 20 Aug 2015 09:14:48 +0000 http://www.hindawi.com/journals/sv/2015/737213/ Novelty detection has been developed into a state-of-the-art technique to detect abnormal behavior and trigger alarm for in-field machine maintenance. With built-up models of normality, it has been widely applied to several situations with normal supervising dataset such as shaft rotating speed and component temperature available meanwhile in the absence of fault information. However, the research about vibration transmission based novelty detection remains unnoticed until recently. In this paper, vibration transmission measurement on rotor is performed; based on extreme value distributions, thresholds for novelty detection are calculated. In order to further decrease the false alarm rate, both measurement and segmentation uncertainty are considered, as they may affect threshold value and detection correctness heavily. Feasible reduction strategies are proposed and discussed. It is found that the associated multifractal coefficient and Kullback-Leibler Divergence operate well in the uncertainty reduction process. As shown by in situ applications to abnormal rotor with pedestal looseness, it is demonstrated that the abnormal states are detected. The higher specificity value proves the effectiveness of proposed uncertainty reduction method. This paper shows novel achievements of uncertainty reduced novelty detection applied to vibration signal in dynamical system and also sheds lights on its utilization in the field of health monitoring of rotating machinery. S. Ma, S. M. Li, and Y. P. Xiong Copyright © 2015 S. Ma et al. All rights reserved. Influence of Geostress Orientation on Fracture Response of Deep Underground Cavity Subjected to Dynamic Loading Wed, 19 Aug 2015 11:00:59 +0000 http://www.hindawi.com/journals/sv/2015/575879/ Deep underground cavity is often damaged under the combined actions of high excavating-induced local stresses and dynamic loading. The fracturing zone and failure type are much related to the initial geostress state. To investigate the influence of geostress orientation on fracture behaviours of underground cavity due to dynamic loading, implicit to explicit sequential solution method was performed in the numerical code to realize the calculation of geostress initialization and dynamic loading on deep underground cavity. The results indicate that when the geostress orientation is heterotropic to the roadway’s floor face (e.g., 30° or 60°), high stress and strain energy concentration are presented in the corner and the spandrel of the roadway, where V-shaped rock failure occurs with the release of massive energy in a very short time. When the geostress orientation is orthogonal to the roadway (e.g., 0° or 90°), the tangential stress and strain energy distribute symmetrically around the cavity. In this regard, the stored strain energy is released slowly under the dynamic loading, resulting in mainly parallel fracture along the roadway’s profile. Therefore, to minimize the damage extent of the surrounding rock, it is of great concern to design the best excavation location and direction of new-opened roadway based on the measuring data of in situ geostresses. Lei Weng, Xibing Li, and Ming Tao Copyright © 2015 Lei Weng et al. All rights reserved. Numerical Investigation of Flapwise-Torsional Vibration Model of a Smart Section Blade with Microtab Wed, 19 Aug 2015 10:00:09 +0000 http://www.hindawi.com/journals/sv/2015/136026/ This study presents a method to develop an aeroelastic model of a smart section blade equipped with microtab. The model is suitable for potential passive vibration control study of the blade section in classic flutter. Equations of the model are described by the nondimensional flapwise and torsional vibration modes coupled with the aerodynamic model based on the Theodorsen theory and aerodynamic effects of the microtab based on the wind tunnel experimental data. The aeroelastic model is validated using numerical data available in the literature and then utilized to analyze the microtab control capability on flutter instability case and divergence instability case. The effectiveness of the microtab is investigated with the scenarios of different output controllers and actuation deployments for both instability cases. The numerical results show that the microtab can effectively suppress both vibration modes with the appropriate choice of the output feedback controller. Nailu Li, Mark J. Balas, Hua Yang, Wei Jiang, and Kaman T. Magar Copyright © 2015 Nailu Li et al. All rights reserved. Semiactive Vibration Control for Horizontal Axis Washing Machine Mon, 17 Aug 2015 07:16:44 +0000 http://www.hindawi.com/journals/sv/2015/692570/ A semiactive vibration control method is developed to cope with the dynamic stability problem of a horizontal axis washing machine. This method is based on adjusting the maximum force values produced by the semiactive suspension elements considering a washing machine’s vibration data (three axis angular position and three axis angular acceleration values in time). Before actuation signals are received by the step motors of the friction dampers, vibration data are evaluated, and then, the step motors start to narrow or expand the radius of bracelets located on the dampers. This changes the damping properties of the damper in the suspension system, and thus, the semiactive suspension system absorbs unwanted vibrations and contributes to the dynamic stability of the washing machine. To evaluate the vibration data, the angular position and angular acceleration values in three axes are defined in a function, and the maximum forces produced by semiactive suspension elements are calculated according to the gradient of this function. The relation between the dynamic stability and the walking stability is also investigated. A motion (gyroscope and accelerometer) sensor is installed on the top-front panel of the washing machine because a mathematical model of a horizontal axis washing machine suggests that the walking behavior starts around this location under some assumptions, and therefore, calculating the vibrations occurring there is crucial. Semiactive damping elements are located under the left and right sides of the tub. The proposed method is tested during the spinning cycle of washing machine operation, increasing gradually from 200 rpm to 900 rpm, which produces the most challenging vibration patterns for dynamic stability. Moreover, the sound power levels produced by the washing machine are measured to evaluate the noise performance of the washing machine while the semiactive suspension system is controlled. The effectiveness of the proposed control method is shown through experimental results. Barış Can Yalçın and Haluk Erol Copyright © 2015 Barış Can Yalçın and Haluk Erol. All rights reserved. The Influence of an EPS Concrete Buffer Layer Thickness on Debris Dams Impacted by Massive Stones in the Debris Flow Thu, 13 Aug 2015 13:30:42 +0000 http://www.hindawi.com/journals/sv/2015/463640/ The failure of debris dams impacted by the massive stones in a debris flow represents a difficult design problem. Reasonable materials selection and structural design can effectively improve the resistance impact performance of debris dams. Based on the cushioning properties of expanded polystyrene (EPS) concrete, EPS concrete as a buffer layer poured on the surface of a rigid debris dam was proposed. A three-dimensional numerical calculation model of an EPS concrete buffer layer/rigid debris dam was established. The single-factor theory revealed change rules for the thickness of the buffer layer concerning the maximal impact force of the rigid debris dam surface through numerical simulation. Moreover, the impact force-time/history curves under different calculation conditions for the rigid debris dam surface were compared. Simulation results showed that the EPS concrete buffer layer can not only effectively extend the impact time of massive stones affecting the debris dam but also reduce the impact force of the rigid debris dam caused by massive stones in the debris flow. The research results provide theoretical guidance for transferring the energy of the massive stone impact, creating a structural design and optimizing debris dams. Xianbin Yu, Xiaoqing Chen, Wanyu Zhao, and Jiangang Chen Copyright © 2015 Xianbin Yu et al. All rights reserved. Experimental Nondestructive Test for Estimation of Buckling Load on Unstiffened Cylindrical Shells Using Vibration Correlation Technique Mon, 10 Aug 2015 07:57:32 +0000 http://www.hindawi.com/journals/sv/2015/729684/ Nondestructive methods, to calculate the buckling load of imperfection sensitive thin-walled structures, such as large-scale aerospace structures, are one of the most important techniques for the evaluation of new structures and validation of numerical models. The vibration correlation technique (VCT) allows determining the buckling load for several types of structures without reaching the instability point, but this technique is still under development for thin-walled plates and shells. This paper presents and discusses an experimental verification of a novel approach using vibration correlation technique for the prediction of realistic buckling loads of unstiffened cylindrical shells loaded under axial compression. Four different test structures were manufactured and loaded up to buckling: two composite laminated cylindrical shells and two stainless steel cylinders. In order to characterize a relationship with the applied load, the first natural frequency of vibration and mode shape is measured during testing using a 3D laser scanner. The proposed vibration correlation technique allows one to predict the experimental buckling load with a very good approximation without actually reaching the instability point. Additional experimental tests and numerical models are currently under development to further validate the proposed approach for composite and metallic conical structures. Kaspars Kalnins, Mariano A. Arbelo, Olgerts Ozolins, Eduards Skukis, Saullo G. P. Castro, and Richard Degenhardt Copyright © 2015 Kaspars Kalnins et al. All rights reserved. Tyre Volume and Pressure Effects on Impact Attenuation during Mountain Bike Riding Sun, 09 Aug 2015 12:29:05 +0000 http://www.hindawi.com/journals/sv/2015/191075/ Exposure to impacts and vibrations has been shown to be detrimental to cross country mountain bike performance and health. Therefore, any strategy aimed at attenuating such exposure is useful to participants and/or industry. The purpose of this study was to assess the influence of tyre size and tyre inflation pressure on exposure to impacts. Participants completed nine trials of a technical section (controlled for initial speed and route taken) including nine separate conditions involving three tyre sizes and three tyre inflation pressures normalised per tyre. Performance was determined by time to negotiate the technical section while triaxial accelerometers recorded accelerations (128 Hz) to quantify impact exposure and the subsequent effects on soft tissue response. Increases in tyre size within the range used improved performance while changes to tyre inflation pressure had no effect on performance. Larger tyre sizes and lower tyre inflation pressures significantly reduced exposure to impacts which could be augmented or negated due to an interaction between tyre size and inflation pressure . It is recommended that mountain bikers use larger tyres, inflated to the moderate pressures used within this study, in order to increase performance and reduce the risk of overuse injuries. Paul W. Macdermid, Matthew C. Miller, Fiona M. Macdermid, and Philip W. Fink Copyright © 2015 Paul W. Macdermid et al. All rights reserved. Virtual Constraints Based Control Design of an Inclined Translational Oscillator with Rotational Actuator System Mon, 03 Aug 2015 06:06:54 +0000 http://www.hindawi.com/journals/sv/2015/769151/ Translational oscillator with rotational actuator (TORA) system, whose translational and rotational movements occur in horizontal planes, is a benchmark of underactuated mechanical systems for studying of control techniques. Currently, the research work of the benchmark mainly focuses on stabilizing control of equilibrium points of the dynamical system. The problem of steering TORA to arbitrary points in its state space is rarely studied. In this paper, the movements of the TORA system are extended to inclined planes and dynamics of the inclined TORA system is presented firstly. Following that, a trajectory tracking control method based on virtual constraints is proposed to steer the oscillations of the inclined TORA system. A virtual constraints based method is presented to generate periodic trajectories which pass through desired point; and a Lyapunov based control design is proposed to track the generated trajectories. Finally, the performance and feasibility of the proposed control design methodology are illustrated and analyzed according to numerical simulations. Bingtuan Gao, Chuande Liu, and Hongtai Cheng Copyright © 2015 Bingtuan Gao et al. All rights reserved. Forced Responses of the Parametric Vibration System for the Electromechanical Integrated Magnetic Gear Thu, 30 Jul 2015 09:46:03 +0000 http://www.hindawi.com/journals/sv/2015/572937/ Considering the magnetic fields modulating in the electromechanical integrated magnetic gear (EIMG), the electromagnetic coupling stiffnesses vary periodically and the expressions are given by the finite element method. The parametric vibration model and the dynamic differential equations are founded. The expressions of forced responses of EIMG system are deduced when the main resonances and the combination resonances occur. And then, the time and frequency responses are figured out. The dynamic characteristics of EIMG system are discussed. The results show that the dominant frequencies in the resonances are always the natural frequency of EIMG system. The relative amplitudes of the components have great difference and the components amplitudes of the main resonances are much bigger than the components amplitudes of the combination resonances. The time-varying meshing stiffness wave between the inner stator and the inner ferromagnetic pole-pieces has little influence on EIMG system. Xiu-hong Hao and Xue-jun Zhu Copyright © 2015 Xiu-hong Hao and Xue-jun Zhu. All rights reserved. Classical Flutter and Active Control of Wind Turbine Blade Based on Piezoelectric Actuation Wed, 29 Jul 2015 16:09:34 +0000 http://www.hindawi.com/journals/sv/2015/292368/ The aim of this article is to analyze classical flutter and active control of single-cell thin-walled composite wind turbine blade beam based on piezoelectric actuation. Effects of piezoelectric actuation for classical flutter suppression on wind turbine blade beam subjected to combined transverse shear deformation, warping restraint effect, and secondary warping are investigated. The extended Hamilton’s principle is used to set up the equations of motion, and the Galerkin method is applied to reduce the aeroelastic coupled equations into a state-space form. Active control is developed to enhance the vibrational behavior and dynamic response to classical aerodynamic excitation and stabilize structures that might be damaged in the absence of control. Active optimal control scheme based on linear quadratic Gaussian (LQG) controller is implemented. The research provides a way for rare study of classical flutter suppression and active control of wind turbine blade based on piezoelectric actuation. Tingrui Liu Copyright © 2015 Tingrui Liu. All rights reserved. Identifying the Mechanical Parameters of Hard Coating with Strain Dependent Characteristic by an Inverse Method Wed, 29 Jul 2015 13:20:20 +0000 http://www.hindawi.com/journals/sv/2015/487457/ The mechanical parameters of hard coating, such as storage modulus and loss factor, are affected by preparation technology significantly and have the strain dependent characteristic. So the effective identification of these mechanical parameters becomes a challenge task. In this study, a hard-coating cantilever thin plate under base excitation was taken as the research object, and an inverse method was developed to identify these mechanical parameters. Firstly, the principles of identifying storage modulus and loss factor of hard coating were presented according to the inverse method. Then, from the need of parameters identification, the analytical model and calculation formula of equivalent strain for the hard-coating composite plate were derived. Next, also for parameter identification, the vibration experiments about the cantilever plate coated with NiCoCrAlY+ yttria-stabilised zirconia (YSZ) hard coating were performed. Finally, the mechanical parameters of NiCoCrAlY+YSZ hard coating with strain dependent characteristic were identified by the proposed method. The identification results show that the change rules of storage modulus and loss factor of hard coating with the strain amplitude are almost consistent with the results listed in the other similar references. However, the identification results herein can more directly serve for the dynamic modeling of hard-coating plate-shape composite structure. Wei Sun, Zhuo Wang, Mingwei Zhu, and Guangyu Du Copyright © 2015 Wei Sun et al. All rights reserved. Shock Analysis on a Packaged Washing Machine from Damage Boundary: Shock Response Spectrum to Component Failure Wed, 29 Jul 2015 13:15:20 +0000 http://www.hindawi.com/journals/sv/2015/462492/ Both analyses of the damage boundary and shock response spectrum (RSR) are the basis for the development of the protective packaging system. The shock analysis through lab test and numerical simulation found that the root cause of packaging failure was due to the stress of the critical component beyond the yield limit of the material. Lab shock test data showed that the packaging design based on the damage boundary is conservative, and the RSR could be helpful and provide support to develop more effective packaging system. Furthermore, numerical simulation can accurately analyze the component and the entire product packaging system in great detail. Jing Qian, Heping Cai, Weiwei Ma, and Zhiwei Hao Copyright © 2015 Jing Qian et al. All rights reserved. Experimental and Numerical Analysis of Hull Girder Vibrations and Bow Impact of a Large Ship Sailing in Waves Wed, 29 Jul 2015 09:45:08 +0000 http://www.hindawi.com/journals/sv/2015/706163/ It is of great importance to evaluate the hull structural vibrations response of large ships in extreme seas. Studies of hydroelastic response of an ultra large ship have been conducted with comparative verification between experimental and numerical methods in order to estimate the wave loads response considering hull vibration and water impact. A segmented self-propelling model with steel backbone system was elaborately designed and the experiments were performed in a tank. Time domain numerical simulations of the ship were carried out by using three-dimensional nonlinear hydroelasticity theory. The results from the computational analyses have been correlated with those from model tests. Jialong Jiao, Huilong Ren, and Christiaan Adika Adenya Copyright © 2015 Jialong Jiao et al. All rights reserved. The Time-Varying Characteristics of Overhead Electric Transmission Lines Considering the Induced-Ice-Shedding Effect Tue, 28 Jul 2015 11:55:12 +0000 http://www.hindawi.com/journals/sv/2015/635230/ More ice deposits accreted on conductors or ground wires may be shed off when an overhead electric transmission line is responding to shocks initiated by natural ice shedding. Ice shedding causes the global mass, stiffness, and damping of the tower-line system to vary with time, and the successive shedding effect beyond a trigger event has not been taken into account in previous studies due to the lack of an adequate ice detachment model. In this paper, the ice shedding effect induced by initial shocks was considered in finite element (FE) analysis. An ice detachment criterion, in the way of user-defined element rupture subroutine, was implemented into the main commercial nonlinear FE program ADINA, making it possible to consider the induced-ice-shedding effect numerically. The incremental FE form of the system’s governing equations of motion is presented where the variations in the mass and stiffness matrices of the system are taken into consideration. Taking a transmission line section following natural ice shedding as a case study, the results indicate that neglecting successive ice shedding underestimates the adverse influence of natural ice shedding. The proposed method can help to improve the design and evaluation of transmission lines in cold regions and to ensure their mechanical security. Kunpeng Ji, Xiaoming Rui, Lin Li, Chao Zhou, Chen Liu, and Ghyslaine McClure Copyright © 2015 Kunpeng Ji et al. All rights reserved. Nonlinear Dynamic Characteristics and Optimal Control of SMA Composite Wings Subjected to Stochastic Excitation Tue, 28 Jul 2015 07:44:38 +0000 http://www.hindawi.com/journals/sv/2015/523723/ A kind of high-aspect-ratio shape memory alloy (SMA) composite wing is proposed to reduce the wing’s fluttering. The nonlinear dynamic characteristics and optimal control of the SMA composite wings subjected to in-plane stochastic excitation are investigated where the great bending under the flight loads is considered. The stochastic stability of the system is analyzed, and the system’s response is obtained. The conditions of stochastic Hopf bifurcation are determined, and the probability density of the first-passage time is obtained. Finally, the optimal control strategy is proposed. Numerical simulation shows that the stability of the system varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the reliability of the system is improved through optimal control, and the first-passage time is delayed. Finally, the effects of the control strategy are proved by experiments. The results of this paper are helpful for engineering applications of SMA. Zhi-Wen Zhu, Xin-Miao Li, and Jia Xu Copyright © 2015 Zhi-Wen Zhu et al. All rights reserved. Hybrid Stochastic Finite Element Method for Mechanical Vibration Problems Mon, 27 Jul 2015 11:49:34 +0000 http://www.hindawi.com/journals/sv/2015/812069/ We present and analyze a new hybrid stochastic finite element method for solving eigenmodes of structures with random geometry and random elastic modulus. The fundamental assumption is that the smallest eigenpair is well defined over the whole stochastic parameter space. The geometric uncertainty is resolved using collocation and random material models using Galerkin method at each collocation point. The response statistics, expectation and variance of the smallest eigenmode, are computed in numerical experiments. The hybrid approach is superior to alternatives in practical cases where the number of random parameters used to describe geometric uncertainty is much smaller than that of the material models. Harri Hakula and Mikael Laaksonen Copyright © 2015 Harri Hakula and Mikael Laaksonen. All rights reserved. Applications of Magnetorheological Technology to Semiactive Vibration Control Systems Mon, 27 Jul 2015 09:53:28 +0000 http://www.hindawi.com/journals/sv/2015/424368/ Miao Yu, Seung-Bok Choi, Norman M. Wereley, Weihua Li, Jeong-Hoi Koo, and Xinchun Guan Copyright © 2015 Miao Yu et al. All rights reserved. Dropping Impact Characteristics Analysis of a Cubic Nonlinear Packaging System with a Cantilever Beam Type Elastic Critical Component with Concentrated Tip Mass Mon, 27 Jul 2015 08:23:04 +0000 http://www.hindawi.com/journals/sv/2015/602984/ A mathematical model for a cubic nonlinear packaging system with a cantilever beam type critical component with concentrated tip mass is proposed. The finite element method and the implicit finite difference method together with the Rung-Kutta method are applied to study the dropping impact dynamics of the critical component and the effect of system parameters, such as the value of the concentrated tip mass and the frequency of the main component, is discussed. The results show that the relative displacement and acceleration change remarkably with the length of the cantilever beam, and the maximum internal stress occurs at the joint end of the critical component. With the increase of the value of the concentrated tip mass and/or a higher frequency of the main component, the amplitudes of the responses increase obviously. Meng Hao and An-Jun Chen Copyright © 2014 Meng Hao and An-Jun Chen. All rights reserved. Indirect Inverse Substructuring Method for Multibody Product Transport System with Rigid and Flexible Coupling Mon, 27 Jul 2015 07:18:13 +0000 http://www.hindawi.com/journals/sv/2015/106416/ The aim of this paper is to develop a new frequency response function- (FRF-) based indirect inverse substructuring method without measuring system-level FRFs in the coupling DOFs for the analysis of the dynamic characteristics of a three-substructure coupled product transport system with rigid and flexible coupling. By enforcing the dynamic equilibrium conditions at the coupling coordinates and the displacement compatibility conditions, a closed-form analytical solution to inverse substructuring analysis of multisubstructure coupled product transport system is derived based on the relationship of easy-to-monitor component-level FRFs and the system-level FRFs at the coupling coordinates. The proposed method is validated by a lumped mass-spring-damper model, and the predicted coupling dynamic stiffness is compared with the direct computation, showing exact agreement. The method developed offers an approach to predict the unknown coupling dynamic stiffness from measured FRFs purely. The suggested method may help to obtain the main controlling factors and contributions from the various structure-borne paths for product transport system. Jun Wang, Li-xin Lu, Pengjiang Qian, Li-qiang Huang, Yan Hua, and Guang-yi Pu Copyright © 2015 Jun Wang et al. All rights reserved. Effect of Fatigue Damage on Energy Absorption Properties of Honeycomb Paperboard Mon, 27 Jul 2015 07:02:57 +0000 http://www.hindawi.com/journals/sv/2015/681671/ The effect of fatigue damage (FD) on the energy absorption properties of precompressed honeycomb paperboard is investigated by fatigue compression experiments. The constitutive relations of honeycomb paperboard have been changed after the fatigue damage. The results show that FD has effect on plateau stress and energy absorption capacity of honeycomb paperboard after fatigue cycles but has no significant effect on densification strain. Energy absorption diagram based on the effect of FD is constructed from the stress-strain curves obtained after fatigue compression experiments. FD is a significant consideration for honeycomb paperboard after transports. The results of this paper could be used for optimization design of packaging materials. Zhi-geng Fan, Li-xin Lu, and Jun Wang Copyright © 2015 Zhi-geng Fan et al. All rights reserved. Design of a Real-Time Adaptively Tuned Dynamic Vibration Absorber with a Variable Stiffness Property Using Magnetorheological Elastomer Sun, 26 Jul 2015 14:14:43 +0000 http://www.hindawi.com/journals/sv/2015/676508/ An elastomer composite with controllable stiffness, known as a magnetorheological elastomer (MRE), is used in a dynamic vibration absorber whose natural frequency is tuned adaptively to the disturbance frequency through the application of an external magnetic field. The field-dependent property test of the fabricated MRE sample shows that the stiffness changes by more than six times compared to the baseline property value at a 40% iron powder volume concentration. The MRE is then used to fabricate a frequency-tunable dynamic absorber for mitigating transient vibrations of a one-degree-of-freedom system. Investigations show that the proposed absorber outperforms a conventional passive-type absorber throughout the tunable frequency range. Toshihiko Komatsuzaki and Yoshio Iwata Copyright © 2015 Toshihiko Komatsuzaki and Yoshio Iwata. All rights reserved. Variational Iteration Method of Dropping Shock Response for the Suspension Spring Packaging System Sun, 26 Jul 2015 12:46:07 +0000 http://www.hindawi.com/journals/sv/2015/408674/ In accordance with dropping shock dimensionless cubic nonlinear dynamic equation of suspension spring system, by variational iteration method, a first-order approximate solution of the system was obtained. The nondimensional peak of displacement, the nondimensional peak of acceleration, and the dropping shock extended period were compared with the results of the Runge-Kutta method, at which relative errors were less than 4%. The influence of suspension angle on peaks of response were discussed. It shows that the maximum response nondimensional acceleration decreases with decrease of the suspension angle under condition of the same nondimensional dropping shock velocity. Conditions for resonance were obtained by applying the variational iteration method, which should be avoided in the packaging design. The results provide reference for suspension spring system design. Shuang Song and An-Jun Chen Copyright © 2015 Shuang Song and An-Jun Chen. All rights reserved. Wavelet Adaptive Algorithm and Its Application to MRE Noise Control System Sun, 26 Jul 2015 12:44:49 +0000 http://www.hindawi.com/journals/sv/2015/968082/ To address the limitation of conventional adaptive algorithm used for active noise control (ANC) system, this paper proposed and studied two adaptive algorithms based on Wavelet. The twos are applied to a noise control system including magnetorheological elastomers (MRE), which is a smart viscoelastic material characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Simulation results reveal that the Decomposition LMS algorithm (D-LMS) and Decomposition and Reconstruction LMS algorithm (DR-LMS) based on Wavelet can significantly improve the noise reduction performance of MRE control system compared with traditional LMS algorithm. Zhang Yulin and Zhao Xiuyang Copyright © 2015 Zhang Yulin and Zhao Xiuyang. All rights reserved. Magnetic Circuit Analyses and Turning Chatter Suppression Based on a Squeeze-Mode Magnetorheological Damping Turning Tool Sun, 26 Jul 2015 12:43:15 +0000 http://www.hindawi.com/journals/sv/2015/304698/ As a smart material, magnetorheological fluid (MRF) has been utilized in fields including civil engineering and automotive engineering, and so on. In this study, the MR damping turning tool based on the squeeze-mode was developed to improve the vibration resistance of the tool system on the lathe. The 3D magnetic circuit simulations of the damper were performed. The influences of damper structural parameters, such as coil positions, plate thicknesses, and others, on the magnetic induction strength were investigated. Orthogonal experiments were carried out and the optimal combination of damper parameters was determined. The chatter suppressive experiments were carried out to evaluate the performance of the MR damping turning tool. Yongliang Zhang, Norman M. Wereley, Wei Hu, Ming Hong, and Wei Zhang Copyright © 2015 Yongliang Zhang et al. All rights reserved.