Shock and Vibration http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Optimum Tuning of a Gyroscopic Vibration Absorber Using Coupled Gyroscopes for Vibration Control of a Vertical Cantilever Beam Thu, 11 Feb 2016 12:08:25 +0000 http://www.hindawi.com/journals/sv/2016/1496727/ This paper deals with the investigation of optimum values of the stiffness and damping which connect two gyroscopic systems formed by two rotors mounted in gimbal assuming negligible masses for the spring, damper, and gimbal support. These coupled gyroscopes use two gyroscopic flywheels, spinning in opposing directions to have reverse precessions to eliminate the forces due to the torque existing in the torsional spring and the damper between gyroscopes. The system is mounted on a vertical cantilever with the purpose of studying the horizontal and vertical vibrations. The equation of motion of the compound system (gyro-beam system) is introduced and solved to find the response measured on the primary system. This is fundamental to design, in some way, the dynamic absorber or neutralizer. On the other hand, the effect of the angular velocities of the gyroscopes are studied, and it is shown that the angular velocity (spin velocity) of a gyroscope has a significant effect on the behavior of the dynamic motion. Correctness of the analytical results is verified by numerical simulations. The comparison with the results from the derivation of the corresponding frequency equations shows that the optimized stiffness and damping values are very accurate. F. Ünker and O. Çuvalcı Copyright © 2016 F. Ünker and O. Çuvalcı. All rights reserved. Fault Diagnosis of Rotating Machinery Based on Adaptive Stochastic Resonance and AMD-EEMD Tue, 09 Feb 2016 12:33:05 +0000 http://www.hindawi.com/journals/sv/2016/9278581/ An adaptive stochastic resonance and analytical mode decomposition-ensemble empirical mode decomposition (AMD-EEMD) method is proposed for fault diagnosis of rotating machinery in this paper. Firstly, the stochastic resonance system is optimized by particle swarm optimization (PSO), and the best structure parameters are obtained. Then, the signal with noise is put into the stochastic resonance system and denoising and enhancing the signal. Secondly, the signal output from the stochastic resonance system is extracted by analytical mode decomposition (AMD) method. Finally, the signal is decomposed by ensemble empirical mode decomposition (EEMD) method. The simulation results show that the optimal stochastic resonance system can effectively improve the signal-to-noise ratio, and the number of effective components of EEMD decomposition is significantly reduced after using AMD, thus improving the decomposition results of EEMD and enhancing the amplitude of components frequency. Through the extraction of the rolling bearing fault signal feature proved that the method has a good effect. Peiming Shi, Cuijiao Su, and Dongying Han Copyright © 2016 Peiming Shi et al. All rights reserved. Torsional Oscillations in Automotive Transmissions: Experimental Analysis and Modelling Mon, 08 Feb 2016 10:04:33 +0000 http://www.hindawi.com/journals/sv/2016/5721960/ The paper investigates the torsional oscillations of an automotive transmission system by means of an experimental test bench used to validate the proposed lumped parameter model. The rig consists of a Dual Clutch Transmission (DCT) and a Manual Transmission (MT) connected through the respective output shafts, while the excitation is provided by two electric motors, which are controlled in speed or torque. The experimental analysis includes the measurement of the external torques, applied by the two electric motors to the mechanical system, and the measurement of the system response in terms of angular speeds at different positions along the transmission line. The frequency response of the system is estimated from the experimental data and compared with the results of a 5-degree-of-freedom lumped parameter model, which proves to be adequate to describe the dynamic behaviour of the system up to a frequency of 200 Hz. The comparison between simulated results and experimental data shows good agreement, so the model can be used to predict the torsional vibrations of the transmission system in the linear field. Moreover, the effects of the nonlinearities associated with the mean value of the excitations are shown. Finally the influence of the selected gear ratio on the experimental frequency response is discussed. Enrico Galvagno, Mauro Velardocchia, and Alessandro Vigliani Copyright © 2016 Enrico Galvagno et al. All rights reserved. Vibration Analysis of Partially Damaged Rotor Bar in Induction Motor under Different Load Condition Using DWT Wed, 03 Feb 2016 13:24:09 +0000 http://www.hindawi.com/journals/sv/2016/3530464/ The relevance of the development of monitoring systems for rotating machines is not only the ability to detect failures but also how early these failures can be detected. The purpose of this paper is to present an experimental study of partially damaged rotor bar in induction motor under different load conditions based on discrete wavelet transform analysis. The approach is based on the extraction of features from vibration signals at different level of damage and three mechanical load conditions. The proposed analysis is reliable for tracking the damage in rotor bar. The paper presents an analysis and extraction of vibration features for partially damaged rotor bar in induction motors. The experimental analysis shows the change in behavior of vibration due to load condition and progressive damage. Jose Rangel-Magdaleno, Hayde Peregrina-Barreto, Juan Ramirez-Cortes, Roberto Morales-Caporal, and Israel Cruz-Vega Copyright © 2016 Jose Rangel-Magdaleno et al. All rights reserved. Vibration Effects of Nonclassically Damped Building-Piping Systems Subjected to Extreme Loads Mon, 01 Feb 2016 11:52:59 +0000 http://www.hindawi.com/journals/sv/2016/6189326/ Piping leakage can occur at T-joint, elbows, valves, or nozzles in nuclear power plants and nonnuclear power plants such as petrochemical plants when subjected to extreme loads and such leakage of piping systems can also lead to fire or explosion. For example, leakage of sodium, toxic gases, or nitrogen in hospitals can cause man-made hazards. The primary objective of this research is to understand the vibration effects due to classical/nonclassical damping with building-piping systems under extreme loads. The current evaluation employed finite-element analysis to calculate the effects of the responses of classically and nonclassically damped building-piping systems. Classical and nonclassical damping matrices for a coupled primary-secondary system were developed based on the Rayleigh equation. A total of 10 selected ground motions were applied to single degree of freedom (SDOF) primary-SDOF secondary (2-DOF coupled) systems in which the ratios of the natural frequencies between the primary and secondary systems ranged between 0.9 and 1.1. It revealed that the vibration effect of nonclassical damping was significant where the natural frequencies of the two systems were nearly tuned. For piping-material nonlinearity, the effects of nonclassical damping on the result forces of piping systems were not significantly different from those of classical damping. YongHee Ryu, WooYoung Jung, and BuSeog Ju Copyright © 2016 YongHee Ryu et al. All rights reserved. Performance of Used Tire Cushion Layer under Rockfall Impact Sun, 31 Jan 2016 14:13:12 +0000 http://www.hindawi.com/journals/sv/2016/8760592/ Rock shed is widely used in traffic lines against rockfall. In order to cushion rockfall impact and dissipate impact energy, cushion layer is usually adopted in rock shed. Used tire cushion layer is proposed in this paper and it can cushion rockfall impact utilizing large radial deformation of tire. Reinforced concrete structure model is built with used tire cushion layer and artificial rockfall test is carried out. Twelve tests are divided into 4 sets with different rockfall mass, rockfall height, and tire filling material. Simplified calculation model with spring-damper is derived from radial repeated compression test of used tire, which improves the calculation efficiency. Test and numerical simulation show that application of used tire cushion layer in rock shed can cushion rockfall impact and effectively reduce peak acceleration and the maximum impact force. Filling sand and gravel in tire can improve tire stiffness and energy absorption capacity but will decrease cushion effect due to its large density. With the same impact energy, light rockfall is more destructive than weight rockfall for used tire cushion layer. Jianhu Sun, Zhaojun Chu, Yingfang Liu, Weiming Luo, and Min Wang Copyright © 2016 Jianhu Sun et al. All rights reserved. Fractal Dimension Based on Morphological Covering for Ground Target Classification Wed, 27 Jan 2016 12:53:29 +0000 http://www.hindawi.com/journals/sv/2016/4548365/ Seismic waves are widely used in ground target classification due to its inherent characteristics. However, they are often affected by extraneous factors and have been found to demonstrate a complicated nonlinear characteristic. The traditional signal analysis methods cannot effectively extract the nonlinear features. Motivated by this fact, this paper applies the fractal dimension (FD) based on morphological covering (MC) method to extract features of the seismic signals for ground targets classification. With the data measured from test field, three different schemes based on MC method are employed to classify tracked vehicle and wheeled vehicle in different operation conditions. Experiment results demonstrate that the three proposed methods achieve more than 90% accuracy for vehicle classification. Kai Du, Xiang Fang, Wei-ping Zhang, and Kai Ding Copyright © 2016 Kai Du et al. All rights reserved. Dynamic Analysis of Impact Model of Slipping Tramcar Prevention Equipment Based on an Energy Absorber Wed, 27 Jan 2016 07:53:32 +0000 http://www.hindawi.com/journals/sv/2016/6961272/ The protection equipment of slipping tramcar in inclined shaft is the important safety equipment to ensure safety production in mine transportation and equipment. The Slipping Tramcar Prevention Equipment is mainly composed of an intercepting door and a buffering system, in which an energy absorber is the key component. The braking dynamic model of the energy absorber is studied by establishing a Lagrange equation and simulating the braking progress by the software of Simulink. The braking simulation distances curves of the energy absorber are obtained under the different initial conditions of tramcar mass and velocity, which shows that the tramcar velocity and mass both have a significant influence on the braking distance. The analysis on variance and range is developed for further comparison on the two key factors implying that tramcar mass is of the most great importance. Moreover, a braking distance formula is built based on the analysis results. On the other hand, field experiments are conducted in Qishan Mine, and experiment results show that the maximum error between the braking distance formula value and the experiment value is 11.98%, and the minimum error is 2.72%. The experimental results are consistent with the theoretical results. Guiyun Xu, Shuo Hu, Xiaoguang Zhang, Jiazhou Zhu, Huipeng Zheng, and Hongxin Wang Copyright © 2016 Guiyun Xu et al. All rights reserved. Vibration Control of Systems in Presence of Hard Nonlinearities Wed, 27 Jan 2016 07:36:21 +0000 http://www.hindawi.com/journals/sv/2016/1923574/ Mario Terzo, Chia-Ming Chang, Zi-Qiang Lang, and Salvatore Strano Copyright © 2016 Mario Terzo et al. All rights reserved. Design on a Composite Mobile System for Exploration Robot Sun, 24 Jan 2016 10:07:07 +0000 http://www.hindawi.com/journals/sv/2016/6363071/ In order to accomplish exploration missions in complex environments, a new type of robot has been designed. By analyzing the characteristics of typical moving systems, a new mobile system which is named wheel-tracked moving system (WTMS) has been presented. Then by virtual prototype simulation, the new system’s ability to adapt complex environments has been verified. As the curve of centroid acceleration changes in large amplitude in this simulation, ride performance of this robot has been studied. Firstly, a simplified dynamic model has been established, and then by affecting factors analysis on ride performance, an optimization model for suspension parameters has been presented. Using NSGA-II method, a set of nondominated solutions for suspension parameters has been gotten, and by weighing the importance of the objective function, an optimal solution has been selected to be applied on suspension design. As the wheel-tracked exploration robot has been designed and manufactured, the property test has been conducted. By testing on physical prototype, the robot’s ability to surmount complex terrain has been verified. Design of the wheel-tracked robot will provide a stable platform for field exploration tasks, and in addition, the certain configuration and suspension parameters optimization method will provide reference to other robot designs. Weiyan Shang, Canjun Yang, Yunping Liu, and Junming Wang Copyright © 2016 Weiyan Shang et al. All rights reserved. Vortex-Induced Vibration of a Cable-Stayed Bridge Thu, 21 Jan 2016 09:56:32 +0000 http://www.hindawi.com/journals/sv/2016/1928086/ The dynamic response of a cable-stayed bridge that consists of a simply supported four-cable-stayed deck beam and two rigid towers, subjected to a distributed vortex shedding force on the deck beam with a uniform rectangular cross section, is studied in this work. The cable-stayed bridge is modeled as a continuous system, and the distributed vortex shedding force on the deck beam is modeled using Ehsan-Scanlan’s model. Orthogonality conditions of exact mode shapes of the linearized undamped cable-stayed bridge model are employed to convert coupled governing partial differential equations of the original cable-stayed bridge model with damping to a set of ordinary differential equations by using Galerkin method. The dynamic response of the cable-stayed bridge is calculated using Runge-Kutta-Felhberg method in MATLAB for two cases with and without geometric nonlinear terms. Convergence of the dynamic response from Galerkin method is investigated. Numerical results show that the geometric nonlinearities of stay cables have significant influence on vortex-induced vibration of the cable-stayed bridge. There are different limit cycles in the case of neglecting the geometric nonlinear terms, and there are only one limit cycle and chaotic responses in the case of considering the geometric nonlinear terms. M. T. Song, D. Q. Cao, and W. D. Zhu Copyright © 2016 M. T. Song et al. All rights reserved. Chaotic Dynamics-Based Analysis of Broadband Piezoelectric Vibration Energy Harvesting Enhanced by Using Nonlinearity Thu, 21 Jan 2016 07:25:46 +0000 http://www.hindawi.com/journals/sv/2016/3584740/ Nonlinear magnetic forces are always used to enlarge resonant bandwidth of vibration energy harvesting systems with piezoelectric cantilever beams. However, how to determine properly the distance between two magnets is one of the key engineering problems. In this paper, the Melnikov theory is introduced to overcome it. Firstly, the Melnikov state-space model of the nonlinear piezoelectric vibration energy harvesting (PVEH) system is built. Based on it, chaotic dynamics mechanisms of achieving broadband PVEH by nonlinearity are exposed by potential function of the unperturbed nonlinear PVEH system. Then the corresponding Melnikov function of the nonlinear PVEH system is defined, based on which two Melnikov necessary conditions of determining the distance are obtained. Finally, numerical simulations are done to testify the theoretic results. The results demonstrate that the distance is closely related to the excitation amplitude and frequency once geometric and material parameters are fixed. Under a single-frequency excitation, the nonlinear PVEH system can generate a periodic vibration around a stable point, a large-amplitude vibration around two stable points, or a chaotic vibration. The proposed method is very valuable for optimally designing and utilizing nonlinear broadband PVEH devices in engineering applications. Zhongsheng Chen, Bin Guo, Congcong Cheng, Hongwu Shi, and Yongmin Yang Copyright © 2016 Zhongsheng Chen et al. All rights reserved. A Method for Aileron Actuator Fault Diagnosis Based on PCA and PGC-SVM Wed, 20 Jan 2016 09:19:39 +0000 http://www.hindawi.com/journals/sv/2016/4807250/ Aileron actuators are pivotal components for aircraft flight control system. Thus, the fault diagnosis of aileron actuators is vital in the enhancement of the reliability and fault tolerant capability. This paper presents an aileron actuator fault diagnosis approach combining principal component analysis (PCA), grid search (GS), 10-fold cross validation (CV), and one-versus-one support vector machine (SVM). This method is referred to as PGC-SVM and utilizes the direct drive valve input, force motor current, and displacement feedback signal to realize fault detection and location. First, several common faults of aileron actuators, which include force motor coil break, sensor coil break, cylinder leakage, and amplifier gain reduction, are extracted from the fault quadrantal diagram; the corresponding fault mechanisms are analyzed. Second, the data feature extraction is performed with dimension reduction using PCA. Finally, the GS and CV algorithms are employed to train a one-versus-one SVM for fault classification, thus obtaining the optimal model parameters and assuring the generalization of the trained SVM, respectively. To verify the effectiveness of the proposed approach, four types of faults are introduced into the simulation model established by AMESim and Simulink. The results demonstrate its desirable diagnostic performance which outperforms that of the traditional SVM by comparison. Wei-Li Qin, Wen-Jin Zhang, and Chen Lu Copyright © 2016 Wei-Li Qin et al. All rights reserved. Effects of Interface Damage Resulting from the Separation of Layered Strata on Bolt Anchoring Systems Mon, 18 Jan 2016 06:43:46 +0000 http://www.hindawi.com/journals/sv/2016/2590816/ Layered strata occurrence is frequently seen in underground constructions, the man-made excavation is thus easy to cause separation between neighboring strata. The sudden and unexpected occurrence of separation will induce significant shock wave and vibration to relative bolting system that initially holds the normal working space for underground production. The bolting system is extremely sensitive to this shock and is easily weakened or damaged. By examining the locations of strata separation and the extent of damage along an anchoring interface, this paper investigates the factors that influence the support strength of anchoring system. The results show that the support strength of a bolt is independent of the separation location if the resin-rock interface is intact. The opposite is the case if the separation width between the neighboring strata exceeds the ultimate critical value, which induces damage along the interface. In this case, the support strength increases exponentially as the separation increases. Separation at the free loading end dramatically decreases the support strength. However, this decrease is mitigated if the separation is located in the middle of the anchoring body or at the loading end. These results are then calibrated and verified in a laboratory test. Xiaowei Feng, Nong Zhang, and Chuangxin Lv Copyright © 2016 Xiaowei Feng et al. All rights reserved. Oscillations Control of Rocking-Block-Type Buildings by the Addition of a Tuned Pendulum Sun, 17 Jan 2016 13:49:04 +0000 http://www.hindawi.com/journals/sv/2016/8570538/ This study deals with the dynamical evolutions exhibited by a simple mechanical model of building, comprising a parallelepiped standing on a horizontal plane. The main goal is the introduction of a pendulum in order to reduce oscillations. The theoretical part of the work consists of a Lagrange formulation and Galerkin approximation method, and dry friction has also been considered. From the analytical/numerical simulations, we derive some important conclusions, providing us with the tools suitable for the design of absorbers in practical cases. Luca Collini, Rinaldo Garziera, Kseniia Riabova, Mariya Munitsyna, and Alessandro Tasora Copyright © 2016 Luca Collini et al. All rights reserved. Numerical Study on Pounding between Two Adjacent Buildings under Earthquake Excitation Sun, 17 Jan 2016 11:54:11 +0000 http://www.hindawi.com/journals/sv/2016/1504783/ Seismic excitation, which results in large horizontal relative displacements, may cause collisions between two adjacent structures due to insufficient separation distance between them. Such collisions, known as earthquake-induced structural pounding, may induce severe damage. In this paper, the case of pounding between two adjacent buildings is studied by the application of single degree-of-freedom structural models. Impact is numerically simulated with the use of a nonlinear viscoelastic model. Special attention is focused on calculating values of impact forces during collisions which have significant influence of pounding-involved response under ground motions. The results of the study indicate that the impact force time history is much dependent on the earthquake excitation analyzed. Moreover, the peak impact forces during collision depend substantially on such parameters as gap size, coefficient of restitution, impact velocity, and stiffness of impact spring element. The nonlinear viscoelastic model of impact force with the considered relation between the damping coefficient and the coefficient of restitution has also been found to be effective in simulating earthquake-induced structural pounding. H. Naderpour, R. C. Barros, S. M. Khatami, and R. Jankowski Copyright © 2016 H. Naderpour et al. All rights reserved. Experimental Study on the Dynamic Performance of a New High-Speed Spindle Supported by Water-Lubricated Hybrid Bearings Sun, 17 Jan 2016 08:02:07 +0000 http://www.hindawi.com/journals/sv/2016/8297834/ The dynamic performance of a new high-speed spindle supported by water-lubricated hybrid bearings is experimentally studied on a test rig. The present design allows the speed of the spindle up to 30,000 rpm, with a bearing internal diameter of 40 mm, which makes it possible to simulate many actual machining processes. Some experiments have been presented to study the mechanical and thermal behaviors of the spindle and its supporting hybrid bearings. The maximum temperature rise is less than 15°C with a speed of 30,000 rpm and a water supply pressure of 2.5 MPa. The spindle radial run-out of the rotational frequency is about 1 µm. Stability of the spindle system has been improved. The experimental results indicate that water-lubricated hybrid bearings are valuable choices to replace ceramic bearings and air bearings as support for spindles under high-speed, high-precision, and heavy-load machining conditions. Lin Wang and Hua Xu Copyright © 2016 Lin Wang and Hua Xu. All rights reserved. Vibration Control on Multilayer Cable Moving through the Crossover Zones on Mine Hoist Thu, 14 Jan 2016 14:01:43 +0000 http://www.hindawi.com/journals/sv/2016/6878021/ Mine hoist is an important piece of equipment in mine hoist systems, and we achieve deep mine hoist through the multilayer winding, but the cable always undergoes severe shock and vibration during the winding process, and the dynamic load and wear would greatly reduce the lifetime of the cable and cause potential safety hazard. In this paper, we start from the course of crossing over of winding cable, use the methods of differential geometry, mechanics, and mathematical analysis, study the movements of the crossover, and derive the important formula that can reduce the vibration of cable during the course of crossover: the formula about central angle of the crossover arc. The results display that four factors contribute to central angle of the crossover arc, that is, the gap of the rope grooves, friction coefficient of the cable, and diameter of the drum and the cable. The result can provide valuable information for designing multilayer winding mine hoist. Xia Peng, Xian-sheng Gong, and Jin-jun Liu Copyright © 2016 Xia Peng et al. All rights reserved. Investigation of Influence Factors of Wind-Induced Buffeting Response of a Six-Tower Cable-Stayed Bridge Thu, 14 Jan 2016 13:11:37 +0000 http://www.hindawi.com/journals/sv/2016/6274985/ This paper presents an investigation of the wind-induced buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A three-dimensional finite element model for the Jiashao Bridge is established using the commercial software package ANSYS and a 3D fluctuating wind field is simulated for both bridge deck and towers. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects including the difference in the longitudinal stiffness between the side towers and central towers, partially longitudinal constraints between the bridge deck and part of bridge towers, self-excited aerodynamic forces, and the rigid hinge installed in the middle of the bridge deck. The analytical results can provide valuable references for wind-resistant design of multispan cable-stayed bridges in the future. Zhi-Qiang Zhang, You-Liang Ding, and Fang-Fang Geng Copyright © 2016 Zhi-Qiang Zhang et al. All rights reserved. Novel Distributed PZT Active Vibration Control Based on Characteristic Model for the Space Frame Structure Thu, 14 Jan 2016 12:42:50 +0000 http://www.hindawi.com/journals/sv/2016/5928270/ A novel distributed PZT control strategy based on characteristic model is presented for space frame structure in this paper. It is a challenge to obtain the exact mechanical model for space structure, since it is a coupling MIMO plant with unknown parameters and disturbances. Thus the characteristic modeling theory is adopted to establish the needed model, which can accurately describe the dynamic characteristics of the space frame structure in real time. On basis of this model, a keep tracking controller is designed to suppress the vibration actively. It is shown that the proposed model-free method is very robust and easy to implement. To solve the complex and difficulty problem on PZT location optimization, an efficient method with modal strain energy and maximum vibration amplitude is proposed. Finally, a simulation study is conducted to investigate the effectiveness of the proposed active vibration control scheme. Hua Zhong, Yong Wang, Hanzheng Ran, Qing Wang, and Changxing Shao Copyright © 2016 Hua Zhong et al. All rights reserved. Identification of Dynamic Loads Based on Second-Order Taylor-Series Expansion Method Thu, 14 Jan 2016 08:14:44 +0000 http://www.hindawi.com/journals/sv/2016/6461427/ A new method based on the second-order Taylor-series expansion is presented to identify the structural dynamic loads in the time domain. This algorithm expresses the response vectors as Taylor-series approximation and then a series of formulas are deduced. As a result, an explicit discrete equation which associates system response, system characteristic, and input excitation together is set up. In a multi-input-multi-output (MIMO) numerical simulation study, sinusoidal excitation and white noise excitation are applied on a cantilever beam, respectively, to illustrate the effectiveness of this algorithm. One also makes a comparison between the new method and conventional state space method. The results show that the proposed method can obtain a more accurate identified force time history whether the responses are polluted by noise or not. Xiaowang Li and Zhongmin Deng Copyright © 2016 Xiaowang Li and Zhongmin Deng. All rights reserved. Nonlinear Model and Qualitative Analysis for Coupled Axial/Torsional Vibrations of Drill String Wed, 13 Jan 2016 08:00:14 +0000 http://www.hindawi.com/journals/sv/2016/1646814/ A nonlinear dynamics model and qualitative analysis are presented to study the key effective factors for coupled axial/torsional vibrations of a drill string, which is described as a simplified, equivalent, flexible shell under axial rotation. Here, after dimensionless processing, the mathematical models are obtained accounting for the coupling of axial and torsional vibrations using the nonlinear dynamics qualitative method, in which excitation loads and boundary conditions of the drill string are simplified to a rotating, flexible shell. The analysis of dynamics responses is performed by means of the Runge-Kutta-Fehlberg method, in which the rules that govern the changing of the torsional and axial excitation are revealed, and suggestions for engineering applications are also given. The simulation analysis shows that when the drill string is in a lower-speed rotation zone, the torsional excitation is the key factor in the coupling vibration, and increasing the torsional stress of the drill string more easily leads to the coupling vibration; however, when the drill string is in a higher-speed rotating zone, the axial excitation is a key factor in the coupling vibration, and the axial stress in a particular interval more easily leads to the coupling vibration of the drill string. Fushen Ren, Baojin Wang, Suli Chen, Zhigang Yao, and Baojun Bai Copyright © 2016 Fushen Ren et al. All rights reserved. A Damage Detection Algorithm Utilizing Dynamic Displacement of Bridge under Moving Vehicle Wed, 13 Jan 2016 06:53:55 +0000 http://www.hindawi.com/journals/sv/2016/8454567/ A damage detection method is proposed, which utilizes dynamic displacement of bridge structures under moving vehicle. The problem is first elaborated with closed-form solution of dynamic displacement, which is decomposed into quasi-static component and dynamic component. Dynamic curvature is defined as second derivative of the dynamic displacement for detecting damage location and estimating damage extent. Damage is modeled by local reduction of stiffness in this paper. Numerical study was conducted on a simply supported beam to verify the proposed method. Vehicle model is analyzed with Newmark’s method using Matlab to obtain the contact force acting on the bridge. Beam model is established in commercial finite element software ABAQUS. The effects of road surface roughness and vehicle-bridge interaction are both considered in the analysis. In order to identify damage location and extent, dynamic curvature was calculated with midspan displacement. Parametric study on measurement noise level, damage location, damage extent, and multiple damage cases is performed, and the analysis results show both reliability and efficacy of this method in damage detection of bridge structures. At last, conclusions are drawn for its application to bridges in engineering practice. Zhen Sun, Tomonori Nagayama, Di Su, and Yozo Fujino Copyright © 2016 Zhen Sun et al. All rights reserved. Structural Performance Assessment Based on Statistical and Wavelet Analysis of Acceleration Measurements of a Building during an Earthquake Tue, 12 Jan 2016 12:54:04 +0000 http://www.hindawi.com/journals/sv/2016/8902727/ This study introduces the analysis of structural health monitoring (SHM) system based on acceleration measurements during an earthquake. The SHM system is applied to assess the performance investigation of the administration building in Seoul National University of Education, South Korea. The statistical and wavelet analysis methods are applied to investigate and assess the performance of the building during an earthquake shaking which took place on March 31, 2014. The results indicate that (1) the acceleration, displacement, and torsional responses of the roof recording point on the top floor of the building are more dominant in the X direction; (2) the rotation of the building has occurred at the base recording point; (3) 95% of the energy content of the building response is shown in the dominant frequency range (6.25–25 Hz); (4) the wavelet spectrum illustrates that the roof vibration is more obvious and dominant during the shaking; and (5) the wavelet spectrum reveals the elasticity responses of the structure during the earthquake shaking. Mosbeh R. Kaloop, Jong Wan Hu, Mohamed A. Sayed, and Jiyoung Seong Copyright © 2016 Mosbeh R. Kaloop et al. All rights reserved. Time Delay Effect on Regenerative Chatter in Tandem Rolling Mills Tue, 12 Jan 2016 11:46:48 +0000 http://www.hindawi.com/journals/sv/2016/4025650/ The interstand tension coupling effect and strip gauge variation passed on to next stand with time delay are the main causes for regenerative chatter in tandem rolling mills. To study the effect of different factors on the stability of tandem rolling mills, different models considering different interstand factors were built. Through stability analysis of these models by employing the Lyapunov indirect method and integral criterion, more detailed and quantitative explanation is put forward to regenerative chatter mechanism in rolling. To study the time delay effect as a single factor on the stability of tandem rolling mills, stability charts of the chatter model including the time delay effect and model neglecting the delay time were compared. The results show that the time delay effect reduces the critical velocity of multistand mills slightly in the big picture. But it alters the relationship between two adjacent stands by worsening the downstream stand stability. To get preferable rolling process parameter configuration for the tandem rolling mills, the time delay effect in rolling must be involved. Xiaochan Liu, Yong Zang, Zhiying Gao, and Lingqiang Zeng Copyright © 2016 Xiaochan Liu et al. All rights reserved. A Unified Spectro-Geometric-Ritz Method for Vibration Analysis of Open and Closed Shells with Arbitrary Boundary Conditions Tue, 12 Jan 2016 11:38:35 +0000 http://www.hindawi.com/journals/sv/2016/4097123/ This paper presents free vibration analysis of open and closed shells with arbitrary boundary conditions using a spectro-geometric-Ritz method. In this method, regardless of the boundary conditions, each of the displacement components of open and closed shells is represented simultaneously as a standard Fourier cosine series and several auxiliary functions. The auxiliary functions are introduced to accelerate the convergence of the series expansion and eliminate all the relevant discontinuities with the displacement and its derivatives at the boundaries. The boundary conditions are modeled using the spring stiffness technique. All the expansion coefficients are treated equally and independently as the generalized coordinates and determined using Rayleigh-Ritz method. By using this method, a unified vibration analysis model for the open and closed shells with arbitrary boundary conditions can be established without the need of changing either the equations of motion or the expression of the displacement components. The reliability and accuracy of the proposed method are validated with the FEM results and those from the literature. Dongyan Shi, Yunke Zhao, Qingshan Wang, Xiaoyan Teng, and Fuzhen Pang Copyright © 2016 Dongyan Shi et al. All rights reserved. Design, Analysis, and Experimental Evaluation of a Double Coil Magnetorheological Fluid Damper Tue, 12 Jan 2016 11:34:16 +0000 http://www.hindawi.com/journals/sv/2016/4184726/ A magnetorheological (MR) damper is one of the most advanced devices used in a semiactive control system to mitigate unwanted vibration because the damping force can be controlled by changing the viscosity of the internal magnetorheological (MR) fluids. This study proposes a typical double coil MR damper where the damping force and dynamic range were derived from a quasistatic model based on the Bingham model of MR fluid. A finite element model was built to study the performance of this double coil MR damper by investigating seven different piston configurations, including the numbers and shapes of their chamfered ends. The objective function of an optimization problem was proposed and then an optimization procedure was constructed using the ANSYS parametric design language (APDL) to obtain the optimal damping performance of a double coil MR damper. Furthermore, experimental tests were also carried out, and the effects of the same direction and reverse direction of the currents on the damping forces were also analyzed. The relevant results of this analysis can easily be extended to the design of other types of MR dampers. Guoliang Hu, Fengshuo Liu, Zheng Xie, and Ming Xu Copyright © 2016 Guoliang Hu et al. All rights reserved. Damage Models and Assessment Methods Tue, 12 Jan 2016 06:01:32 +0000 http://www.hindawi.com/journals/sv/2016/1748712/ Gilbert-Rainer Gillich, Magd Abdel Wahab, Ruqiang Yan, and José V. Araújo dos Santos Copyright © 2016 Gilbert-Rainer Gillich et al. All rights reserved. Gear Fault Diagnosis Based on Empirical Mode Decomposition and 1.5 Dimension Spectrum Mon, 11 Jan 2016 13:27:40 +0000 http://www.hindawi.com/journals/sv/2016/5915762/ Aiming at the nonlinear and nonstationary feature of mechanical fault vibration signal, a new fault diagnosis method, which is based on a combination of empirical mode decomposition (EMD) and 1.5 dimension spectrum, is proposed. Firstly, the vibration signal is decomposed by EMD and the correlation coefficient between each intrinsic mode function and original signal is calculated. Then these intrinsic mode function components, which have a big correlation coefficient, are selected to estimate its 1.5 dimension spectrum. And this method uses 1.5 dimension spectrum of each intrinsic mode function to reconstruct its power spectrum. And these power spectrums are summed to obtain the primary power spectrum of gear fault signal. Finally, the information feature of fault is extracted from the reconstructed 1.5 dimension spectrum. A model to reconstruct 1.5 dimension spectrum is established, and the principle and steps of the method are presented. Some simulated and measured gear fault signals have been processed to demonstrate the effectiveness of new method. The result shows that this method can greatly inhibit the interference of Gauss noise to raise the SNR and recognize the secondary phase coupling feature of the signal. The proposed method has a good real-time performance and provides an effective method to determine the early crack fault of gear root. Jianhua Cai and Xiaoqin Li Copyright © 2016 Jianhua Cai and Xiaoqin Li. All rights reserved. Active Control of Contact Force for a Pantograph-Catenary System Mon, 11 Jan 2016 12:20:10 +0000 http://www.hindawi.com/journals/sv/2016/2735297/ The performance of the high speed trains depends critically on the quality of the contact in the pantograph-catenary interaction. Maintaining a constant contact force needs taking special measures and one of the methods is to utilize active control to optimize the contact force. A number of active control methods have been proposed in the past decade. However, the primary objective of these methods has been to reduce the variation of the contact force in the pantograph-catenary system, ignoring the effects of locomotive vibrations on pantograph-catenary dynamics. Motivated by the problems in active control of vibration in large scale structures, the author has developed a geometric framework specifically targeting the remote vibration suppression problem based only on local control action. It is the intention of the paper to demonstrate its potential in the active control of the pantograph-catenary interaction, aiming to minimize the variation of the contact force while simultaneously suppressing the vibration disturbance from the train. A numerical study is provided through the application to a simplified pantograph-catenary model. Jiqiang Wang Copyright © 2016 Jiqiang Wang. All rights reserved.