Shock and Vibration The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Adaptive Multiscale Noise Control Enhanced Stochastic Resonance Method Based on Modified EEMD with Its Application in Bearing Fault Diagnosis Wed, 26 Oct 2016 12:35:52 +0000 The structure of mechanical equipment becomes increasingly complex, and tough environments under which it works often make bearings and gears subject to failure. However, effective extraction of useful feature information submerged in strong noise that is indicative of structural defects has remained a major challenge. Therefore, an adaptive multiscale noise control enhanced stochastic resonance (SR) method based on modified ensemble empirical mode decomposition (EEMD) for mechanical fault diagnosis is proposed in the paper. According to the oscillation characteristics of signal itself, the algorithm of modified EEMD can adaptively decompose the fault signals into different scales and it reduces the decomposition levels to improve calculation efficiency of the proposed method. Through filter processing with the constructed filters, the orthogonality of adjacent intrinsic mode functions (IMFs) can be improved, which is conducive to enhancing the extraction of weak features from strong noise. The constructed signal obtained by using IMFs is inputted into the SR system, and the noise control parameter of different scales is optimized and selected with the help of the genetic algorithm, thus achieving the enhancement extraction of weak features. Finally, simulation experiments and engineering application of bearing fault diagnosis demonstrate the effectiveness and feasibility of the proposed method. Jimeng Li and Jinfeng Zhang Copyright © 2016 Jimeng Li and Jinfeng Zhang. All rights reserved. Active Vibration Control and Coupled Vibration Analysis of a Parallel Manipulator with Multiple Flexible Links Wed, 26 Oct 2016 10:25:07 +0000 This paper addresses the active vibration control and coupled vibration analysis of a planar parallel manipulator (PPM) with three flexible links. Multiple piezoelectric ceramic transducers are integrated with the flexible links to constitute the smart beam structures, and hence the vibration of the flexible link can be self-sensed and self-controlled. To prevent the spillover phenomena and improve the vibration control efficiency, the independent modal space control combined with an input shaper is developed to suppress both the structural and the residual vibration of the flexible links. The coupled vibration features between rigid and elastic motions and the interaction effects among three flexible links are theoretically analyzed based on the one-pass rigid-flexible dynamic models. Numerical simulation and experiment results show that the vibration of the three flexible links is coupled through the moving platform and the vibration suppression efficiency is getting improved with the number of controlled flexible links increased. Quan Zhang, Chaodong Li, Jiantao Zhang, and Jiamei Jin Copyright © 2016 Quan Zhang et al. All rights reserved. A Comparative Study of Ground and Underground Vibrations Induced by Bench Blasting Wed, 26 Oct 2016 08:39:17 +0000 Ground vibrations originating from bench blasting may cause damage to slopes, structures, and underground workings in close proximity to an operating open-pit mine. It is important to monitor and predict ground vibration levels induced by blasting and to take measures to reduce their hazardous effects. The aims of this paper are to determine the weaker protection objects by comparatively studying bench blasting induced vibrations obtained at surface and in an underground tunnel in an open-pit mine and thus to seek vibration control methods to protect engineering objects at the site. Vibrations arising from measurement devices at surface and in an underground tunnel at the Zijinshan Open-Pit Mine were obtained. Comparative analysis of the peak particle velocities shows that, in the greatest majority of cases, surface values are higher than underground values for the same vibration distance. The transmission laws of surface and underground vibrations were established depending on the type of rock mass, the explosive charge, and the distance. Compared with the Chinese Safety Regulations for Blasting (GB6722-2014), the bench blasting induced vibrations would not currently cause damage to the underground tunnel. According to the maximum allowable peak particle velocities for different objects, the permitted maximum charges per delay are obtained to reduce damage to these objects at different distances. Xiuzhi Shi, Xianyang Qiu, Jian Zhou, Dan Huang, Xin Chen, and Yonggang Gou Copyright © 2016 Xiuzhi Shi et al. All rights reserved. Order Spectrum Analysis for Bearing Fault Detection via Joint Application of Synchrosqueezing Transform and Multiscale Chirplet Path Pursuit Tue, 25 Oct 2016 14:52:02 +0000 Order tracking has become one of the most effective methods for fault detection of rotating machinery under the time-varying shaft speed conditions. The transient phase estimation is very important for order tracking, especially when the tachometer installation is not convenient. The transient phase is usually obtained by integrating the instantaneous frequency (IF), so the IF estimation has attracted a great deal of concerns. This article describes a new IF estimation method based on the joint application of the synchrosqueezing transform (SST) and the multiscale chirplet path pursuit (MSCPP) method. The SST method as its high frequency resolution merits is used to estimate the frequency parameters for the parameter settings of the MSCPP method, that will resolve the high computation problem of the MSCPP method to a certain degree, so as to extensively use the high accuracy of the MSCPP method in IF estimation. The order spectrum based on the estimated IF can provide the demodulation information for the bearing fault diagnosis. The performance of the proposed method has been validated by both simulation and experimental data. Jiesi Luo, Shaohui Zhang, Mingen Zhong, and Zusheng Lin Copyright © 2016 Jiesi Luo et al. All rights reserved. Fluid-Elastic Instability Tests on Parallel Triangular Tube Bundles with Different Mass Ratio Values under Increasing and Decreasing Flow Velocities Tue, 25 Oct 2016 07:41:37 +0000 To study the effects of increasing and decreasing flow velocities on the fluid-elastic instability of tube bundles, the responses of an elastically mounted tube in a rigid parallel triangular tube bundle with a pitch-to-diameter ratio of 1.67 were tested in a water tunnel subjected to crossflow. Aluminum and stainless steel tubes were tested, respectively. In the in-line and transverse directions, the amplitudes, power spectrum density functions, response frequencies, added mass coefficients, and other results were obtained and compared. Results show that the nonlinear hysteresis phenomenon occurred in both tube bundle vibrations. When the flow velocity is decreasing, the tubes which have been in the state of fluid-elastic instability can keep on this state for a certain flow velocity range. During this process, the response frequencies of the tubes will decrease. Furthermore, the response frequencies of the aluminum tube can decrease much more than those of the stainless steel tube. The fluid-elastic instability constants fitted for these experiments were obtained from experimental data. A deeper insight into the fluid-elastic instability of tube bundles was also obtained by synthesizing the results. This study is beneficial for designing and operating equipment with tube bundles inside, as well as for further research on the fluid-elastic instability of tube bundles. Xu Zhang, Bin Jiang, Luhong Zhang, and Xiaoming Xiao Copyright © 2016 Xu Zhang et al. All rights reserved. Vibration-Based Adaptive Novelty Detection Method for Monitoring Faults in a Kinematic Chain Mon, 24 Oct 2016 13:31:22 +0000 This paper presents an adaptive novelty detection methodology applied to a kinematic chain for the monitoring of faults. The proposed approach has the premise that only information of the healthy operation of the machine is initially available and fault scenarios will eventually develop. This approach aims to cover some of the challenges presented when condition monitoring is applied under a continuous learning framework. The structure of the method is divided into two recursive stages: first, an offline stage for initialization and retraining of the feature reduction and novelty detection modules and, second, an online monitoring stage to continuously assess the condition of the machine. Contrary to classical static feature reduction approaches, the proposed method reformulates the features by employing first a Laplacian Score ranking and then the Fisher Score ranking for retraining. The proposed methodology is validated experimentally by monitoring the vibration measurements of a kinematic chain driven by an induction motor. Two faults are induced in the motor to validate the method performance to detect anomalies and adapt the feature reduction and novelty detection modules to the new information. The obtained results show the advantages of employing an adaptive approach for novelty detection and feature reduction making the proposed method suitable for industrial machinery diagnosis applications. Jesus Adolfo Cariño-Corrales, Juan Jose Saucedo-Dorantes, Daniel Zurita-Millán, Miguel Delgado-Prieto, Juan Antonio Ortega-Redondo, Roque Alfredo Osornio-Rios, and Rene de Jesus Romero-Troncoso Copyright © 2016 Jesus Adolfo Cariño-Corrales et al. All rights reserved. Bearing Performance Degradation Assessment Using Lifting Wavelet Packet Symbolic Entropy and SVDD Mon, 24 Oct 2016 11:22:50 +0000 Bearing performance degradation assessment is of great significance for proactive maintenance and near-zero downtime. For this purpose, a novel assessment method is proposed based on lifting wavelet packet symbolic entropy (LWPSE) and support vector data description (SVDD). LWPSE is presented for feature extraction by jointing use of lifting wavelet packet transform and symbolic entropy. Firstly, the LWPSEs of bearing signals from normal bearing condition are extracted to train an SVDD model by fitting a tight hypersphere around normal samples. Then, the relative distance from the LWPSEs of testing signals to the hypersphere boundary is calculated as a quantitative index for bearing performance degradation assessment. The feasibility and efficiency of the proposed method were validated by the life-cycle data obtained from NASA’s prognostics data repository and the comparison with Hidden Markov Model (HMM). Finally, the assessment results were verified by the envelope spectrum analysis method based on empirical mode decomposition and Hilbert envelope demodulation. Jianmin Zhou, Huijuan Guo, Long Zhang, Qingyao Xu, and Hui Li Copyright © 2016 Jianmin Zhou et al. All rights reserved. Performance of Seismic Restrainer with SMA Springs for Sliding Isolation of Single-Layer Spherical Lattice Shells Sun, 23 Oct 2016 07:29:10 +0000 The seismic response of a single-layer spherical lattice shell controlled by restorable sliding isolator is studied under different seismic excitations. The isolation system consists of flat steel-Teflon sliding isolators and superelastic SMA spring restrainers. The NiTi-SMA is used to fabricate helical spring for recentering control of the isolation system. In the first step of this investigation, the configuration scheme and functioning mechanism of a novel SMA spring restrainer are introduced briefly. Then, realistic mechanical behavior of large-scale superelastic NiTi helical spring is studied through a set of cyclic experimental tests. According to the obtained hysteresis loops, a mechanical model combining multilinear model and hysteresis model is developed to simulate the overall response of the SMA-based seismic restrainer. Besides, the sliding isolator is evaluated using a bilinear force-displacement hysteresis model. Finally, a 60 m span single-layer spherical lattice shell with substructure is modeled with finite element program. Nonlinear time history analyses of the controlled and uncontrolled lattice shell are performed considering multidimensional seismic inputs. The study shows that the seismic response of the controlled lattice shell can be effectively reduced by using isolation and control devices. Furthermore, the seismic response of the isolation system such as peak displacement and residual displacement can be effectively controlled by using the developed SMA spring restrainers. Peng Zhuang and Wenting Wang Copyright © 2016 Peng Zhuang and Wenting Wang. All rights reserved. A Review of the Evaluation, Control, and Application Technologies for Drill String Vibrations and Shocks in Oil and Gas Well Thu, 20 Oct 2016 14:01:34 +0000 Drill string vibrations and shocks (V&S) can limit the optimization of drilling performance, which is a key problem for trajectory optimizing, wellbore design, increasing drill tools life, rate of penetration, and intelligent drilling. The directional wells and other special trajectory drilling technologies are often used in deep water, deep well, hard rock, and brittle shale formations. In drilling these complex wells, the cost caused by V&S increases. According to past theories, indoor experiments, and field studies, the relations among ten kinds of V&S, which contain basic forms, response frequency, and amplitude, are summarized and discussed. Two evaluation methods are compared systematically, such as theoretical and measurement methods. Typical vibration measurement tools are investigated and discussed. The control technologies for drill string V&S are divided into passive control, active control, and semiactive control. Key methods for and critical equipment of three control types are compared. Based on the past development, a controlling program of drill string V&S is devised. Application technologies of the drill string V&S are discussed, such as improving the rate of penetration, controlling borehole trajectory, finding source of seismic while drilling, and reducing the friction of drill string. Related discussions and recommendations for evaluating, controlling, and applying the drill string V&S are made. Guangjian Dong and Ping Chen Copyright © 2016 Guangjian Dong and Ping Chen. All rights reserved. Vibration Control of Double-Beam System with Multiple Smart Damping Members Wed, 19 Oct 2016 12:08:58 +0000 A control method to stabilize vibration of a double cantilever system with a set of smart damping blocks is designed and numerically evaluated. The externally controlled magnetorheological sheared elastomer damping block is considered, but other smart materials can be used as well. The robust bang-bang control law for stabilization the bilinear system is elaborated. The key feature of the closed loop controller is the efficiency for different types of initial excitement. By employing the finite element model, the performance of the controller is validated for strong wind blow load and concentrated impact excitement of the particular point of one of the beams. For each of the excitations, the closed loop control outperforms the optimal passive damping case by over 27% for the considered energy metric. Dominik Pisarski, Tomasz Szmidt, Czesław I. Bajer, Bartłomiej Dyniewicz, and Jacek M. Bajkowski Copyright © 2016 Dominik Pisarski et al. All rights reserved. Dynamical Analysis and Simulation Validation of Incompletely Restrained Cable-Suspended Swinging System Driven by Two Cables Sun, 16 Oct 2016 14:20:01 +0000 The flexibility of the suspension multicables and driven length difference between two cables cause the translation and rotation of the platform in the incompletely restrained cable-suspended system driven by two cables (IRCSWs2), which are theoretically investigated in this paper. The suspension cables are spatially discretized using the assumed modes method (AMM) and the equations of motion are derived from Lagrange equations of the first kind. Considering all the geometric matching conditions are approximately linear with external actuator, the differential algebraic equations (DAEs) are transformed to a system of ordinary differential equations (ODEs). Using linear boundary conditions of the suspension cable, the current method can obtain not only the accurate longitudinal displacements of cable and posture of the platform, but also the tension between the platform and cables, and the current method is verified by ADAMS simulation. Naige Wang, Guohua Cao, Zhencai Zhu, and Weihong Peng Copyright © 2016 Naige Wang et al. All rights reserved. Fractal Model for Acoustic Absorbing of Porous Fibrous Metal Materials Sun, 16 Oct 2016 13:08:52 +0000 To investigate the changing rules between sound absorbing performance and geometrical parameters of porous fibrous metal materials (PFMMs), this paper presents a fractal acoustic model by incorporating the static flow resistivity based on Biot-Allard model. Static flow resistivity is essential for an accurate assessment of the acoustic performance of the PFMM. However, it is quite difficult to evaluate the static flow resistivity from the microstructure of the PFMM because of a large number of disordered pores. In order to overcome this difficulty, we firstly established a static flow resistivity formula for the PFMM based on fractal theory. Secondly, a fractal acoustic model was derived on the basis of the static flow resistivity formula. The sound absorption coefficients calculated by the presented acoustic model were validated by the values of Biot-Allard model and experimental data. Finally, the variation of the surface acoustic impedance, the complex wave number, and the sound absorption coefficient with the fractal dimensions were discussed. The research results can reveal the relationship between sound absorption and geometrical parameters and provide a basis for improving the sound absorption capability of the PFMMs. Weihua Chen, Tianning Chen, Xiaopeng Wang, Jiuhui Wu, and Suobin Li Copyright © 2016 Weihua Chen et al. All rights reserved. Stator Vibration Characteristic Identification of Turbogenerator among Single and Composite Faults Composed of Static Air-Gap Eccentricity and Rotor Interturn Short Circuit Sun, 16 Oct 2016 08:11:42 +0000 This paper investigates the radial stator vibration characteristics of turbogenerator under the static air-gap eccentricity (SAGE) fault, the rotor interturn short circuit (RISC) fault, and the composite faults (CFs) composed of SAGE and RISC, respectively. Firstly, the impact of the faulty types on the magnetic flux density (MFD) is analyzed, based on which the detailed expressions of the magnetic pull per unit area (MPPUA) on the stator under different performing conditions are deduced. Then, numerical FEM simulations based on Ansoft and an experimental study are carried out, taking the SDF-9 type fault simulating generator as the study object. It is shown that SAGE will increase the stator vibration at 2f (f is the electrical frequency) which already exists even in normal condition, while RISC and CF will bring in stator vibrations at f, 2f, 3f, and 4f at the same time. The vibration amplitudes under CF are larger than those under RISC. As SAGE increases, the vibration amplitudes of each harmonic component under CF will all be increased, while the development of RISC will decrease the 2nd harmonic vibration but meanwhile increase the 4th harmonic vibration. The achievements of this paper are beneficial for fault identification and condition monitoring of the turbogenerator. Yu-Ling He, Wei-Qi Deng, Bo Peng, Meng-Qiang Ke, Gui-Ji Tang, Shu-Ting Wan, and Xiang-Yu Liu Copyright © 2016 Yu-Ling He et al. All rights reserved. Modelling and Composite Control of Single Flexible Manipulators with Piezoelectric Actuators Sun, 09 Oct 2016 13:23:09 +0000 The piezoelectric actuators are used to investigate the active vibration control of flexible manipulators in this paper. Based on the assumed mode method, piezoelectric coupling model, and Hamilton’s principle, the dynamic equation of the single flexible manipulator (SFM) with surface bonded actuators is established. Then, a singular perturbation model consisted of a slow subsystem and a fast subsystem is formulated and used for designing the composite controller. The slow subsystem controller is designed by fuzzy sliding mode control method, and the linear quadratic regulator (LQR) optimal control method is used to design fast subsystem controller. Furthermore, the changing trends of natural frequencies along with the changes in the position of piezoelectric actuators are obtained through the ANSYS Workbench software, by which the optimal placement of actuators is determined. Finally, numerical simulations and experiments are presented. The results demonstrate that the method of optimal placement is feasible based on the maximal natural frequency, and the composite controller presented in this paper can not only realize the trajectory tracking of the SFM and has a good result on the vibration suppression. En Lu, Wei Li, Xuefeng Yang, Mengbao Fan, and Yufei Liu Copyright © 2016 En Lu et al. All rights reserved. Innovative Technologies for Reducing Structural Vibrations due to Natural Events and Human Activities Sun, 09 Oct 2016 07:43:59 +0000 Nicola Caterino, Christos T. Georgakis, Ningsu Luo, and Julian Londono Monsalve Copyright © 2016 Nicola Caterino et al. All rights reserved. Application of Volterra Integral Equations in Dynamics of Multispan Uniform Continuous Beams Subjected to a Moving Load Tue, 04 Oct 2016 11:27:00 +0000 The dynamic behavior of multispan uniform continuous beam arbitrarily supported on its edges subjected to various types of moving noninertial loads is studied. Problem is solved by replacing a multispan structure with a single-span beam loaded with a given moving load and redundant forces situated in the positions of the intermediate supports. Redundant forces are obtained by solving Volterra integral equations of the first or the second order (depending on the stiffness of the intermediate supports) which are consistent deformation equations corresponding to each redundant. Solutions for the beam arbitrarily supported on its edges (pinned or fixed) due to a moving concentrated force and moving distributed load are given. The difficulty of solving Volterra integral equations analytically is bypassed by proposing a simple numerical procedure. Numerical examples of two- and three-span beam have been included in order to show the efficiency of the presented method. Filip Zakęś and Paweł Śniady Copyright © 2016 Filip Zakęś and Paweł Śniady. All rights reserved. Synchronization and Stability of Elasticity Coupling Two Homodromy Rotors in a Vibration System Tue, 04 Oct 2016 09:38:17 +0000 The mechanical model of an elasticity coupling 1-DOF system is proposed to implement synchronization; the simplified model is composed of a rigid body, two induction motors, and a connecting spring. Based on the Lagrange equations, the dynamic equation of the system is established. Moreover, a typical analysis method, the Poincare method, is applied to study the synchronization characteristics, and the balanced equations and stability criterion of the system are obtained. Obviously, it can be seen that many parameters affect the synchronous state of the system, especially the stiffness of the support spring, the stiffness of the connecting spring, and the installation location of the motors. Meanwhile, choose a suitable stiffness of the connecting spring (k), which would play a significant role in engineering. Finally, computer simulations are used to verify the correctness of the theoretical analysis. Yongjun Hou, Mingjun Du, Pan Fang, Yuwen Wang, and Liping Zhang Copyright © 2016 Yongjun Hou et al. All rights reserved. Research on Aerodynamic Noise Reduction for High-Speed Trains Mon, 03 Oct 2016 06:51:25 +0000 A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H) acoustic analogy. An analysis of noise reduction methods based on the main noise sources was performed. An aerodynamic noise model for a full-scale high-speed train, including three coaches with six bogies, two inter-coach spacings, two windscreen wipers, and two pantographs, was established. Several low-noise design improvements for the high-speed train were identified, based primarily on the main noise sources; these improvements included the choice of the knuckle-downstream or knuckle-upstream pantograph orientation as well as different pantograph fairing structures, pantograph fairing installation positions, pantograph lifting configurations, inter-coach spacings, and bogie skirt boards. Based on the analysis, we designed a low-noise structure for a full-scale high-speed train with an average sound pressure level (SPL) 3.2 dB(A) lower than that of the original train. Thus, the noise reduction design goal was achieved. In addition, the accuracy of the aerodynamic noise calculation method was demonstrated via experimental wind tunnel tests. Yadong Zhang, Jiye Zhang, Tian Li, Liang Zhang, and Weihua Zhang Copyright © 2016 Yadong Zhang et al. All rights reserved. Multicrack Localization in Rotors Based on Proper Orthogonal Decomposition Using Fractal Dimension and Gapped Smoothing Method Thu, 29 Sep 2016 14:23:55 +0000 Multicrack localization in operating rotor systems is still a challenge today. Focusing on this challenge, a new approach based on proper orthogonal decomposition (POD) is proposed for multicrack localization in rotors. A two-disc rotor-bearing system with breathing cracks is established by the finite element method and simulated sensors are distributed along the rotor to obtain the steady-state transverse responses required by POD. Based on the discontinuities introduced in the proper orthogonal modes (POMs) at the locations of cracks, the characteristic POM (CPOM), which is sensitive to crack locations and robust to noise, is selected for cracks localization. Instead of using the CPOM directly, due to its difficulty to localize incipient cracks, damage indexes using fractal dimension (FD) and gapped smoothing method (GSM) are adopted, in order to extract the locations more efficiently. The method proposed in this work is validated to be effective for multicrack localization in rotors by numerical experiments on rotors in different crack configuration cases considering the effects of noise. In addition, the feasibility of using fewer sensors is also investigated. Zhiwen Lu, Dawei Dong, Shancheng Cao, Huajiang Ouyang, and Chunrong Hua Copyright © 2016 Zhiwen Lu et al. All rights reserved. Modal and Dynamic Analysis of a Vehicle with Kinetic Dynamic Suspension System Thu, 29 Sep 2016 11:30:02 +0000 A novel kinetic dynamic suspension (KDS) system is presented for the cooperative control of the roll and warp motion modes of off-road vehicles. The proposed KDS system consists of two hydraulic cylinders acting on the antiroll bars. Hence, the antiroll bars are not completely replaced by the hydraulic system, but both systems are installed. In this paper, the vibration analysis in terms of natural frequencies of different motion modes in frequency domain for an off-road vehicle equipped with different configurable suspension systems is studied by using the modal analysis method. The dynamic responses of the vehicle with different configurable suspension systems are investigated under different road excitations and maneuvers. The results of the modal and dynamic analysis prove that the KDS system can reduce the roll and articulation motions of the off-road vehicle without adding extra bounce stiffness and deteriorating the ride comfort. Furthermore, the roll stiffness is increased and the warp stiffness is decreased by the KDS system, which could significantly enhance handing performance and off-road capability. Bangji Zhang, Jie Zhang, Jinhua Yi, Nong Zhang, and Qiutan Jin Copyright © 2016 Bangji Zhang et al. All rights reserved. Seismic Strengthening Effects Based on Pseudodynamic Testing of a Reinforced Concrete Building Retrofitted with a Wire-Woven Bulk Kagome Truss Damper Wed, 28 Sep 2016 14:09:17 +0000 A passive damper with a wire-woven bulk Kagome truss design was recently developed; its applicability as a passive damper to improve the seismic performance of building systems, including shear hysteresis behavior, energy dissipation capacity, and fatigue, was confirmed by material tests. The Kagome truss, a periodic cellular metal type, is composed of evenly distributed helical wires with a constant pitch and helical radius in six directions. The purpose of this study was to develop a new passive damper system for seismic strengthening of existing reinforced concrete (RC) frames. The proposed external connection methodology uses a wire-woven bulk Kagome truss (i.e., a Kagome damper external connection (KDEC) system), to dissipate earthquake energy using the dynamic interaction among an existing building, a support structure, and the Kagome damper installed between them. Four test specimens were designed and then strengthened with the KDEC system. Cyclic loading and pseudodynamic tests were conducted; lateral load-carrying capacity, deformation, and hysteresis characteristics were investigated, as well as the maximum response strength, response ductility, and earthquake damage degree, and compared to a control sample. Test results revealed that the KDEC system effectively dissipated the earthquake energy, showing considerable resilience under large-scale earthquake conditions. Jae-Sung Hwang and Kang Seok Lee Copyright © 2016 Jae-Sung Hwang and Kang Seok Lee. All rights reserved. Behavior of a Flat Solid in a Container with Liquid Subject to Large Amplitude Vibration Tue, 27 Sep 2016 07:09:00 +0000 We experimentally study the behavior of a flat body in the oscillating container with liquid. The body density is much more than the density of liquid. The body oscillates with large amplitude under the action of inertia forces. It is found that under the vibration the body lifts up and goes to quasi-steady suspended state at some distance from the container bottom. The lift force is measured by a method of dynamic suspension of a body in the gravity field. It is found that the dimensionless repulsion lift force depends on the dimensionless amplitude of the body oscillations; it reduces with the amplitude and is in agreement with the theoretical model in the limit of small amplitude. Qualitatively new regimes of body behavior are found in the supercritical region. With an increase of the vibration intensity, the body gets a stable state in the middle of the container height and then moves on to the container ceiling. Victor Kozlov and Olga Vlasova Copyright © 2016 Victor Kozlov and Olga Vlasova. All rights reserved. Research on Mechanical Fault Diagnosis Scheme Based on Improved Wavelet Total Variation Denoising Mon, 26 Sep 2016 16:36:57 +0000 Wavelet analysis is a powerful tool for signal processing and mechanical equipment fault diagnosis due to the advantages of multiresolution analysis and excellent local characteristics in time-frequency domain. Wavelet total variation (WATV) was recently developed based on the traditional wavelet analysis method, which combines the advantages of wavelet-domain sparsity and total variation (TV) regularization. In order to guarantee the sparsity and the convexity of the total objective function, nonconvex penalty function is chosen as a new wavelet penalty function in WATV. The actual noise reduction effect of WATV method largely depends on the estimation of the noise signal variance. In this paper, an improved wavelet total variation (IWATV) denoising method was introduced. The local variance analysis on wavelet coefficients obtained from the wavelet decomposition of noisy signals is employed to estimate the noise variance so as to provide a scientific evaluation index. Through the analysis of the numerical simulation signal and real-word failure data, the results demonstrated that the IWATV method has obvious advantages over the traditional wavelet threshold denoising and total variation denoising method in the mechanical fault diagnose. Wentao He, Cancan Yi, Yourong Li, and Han Xiao Copyright © 2016 Wentao He et al. All rights reserved. Fault Diagnosis of a Hydraulic Pump Based on the CEEMD-STFT Time-Frequency Entropy Method and Multiclass SVM Classifier Mon, 26 Sep 2016 13:05:24 +0000 The fault diagnosis of hydraulic pumps is currently important and significant to ensure the normal operation of the entire hydraulic system. Considering the nonlinear characteristics of hydraulic-pump vibration signals and the mode mixing problem of the original Empirical Mode Decomposition (EMD) method, first, we use the Complete Ensemble EMD (CEEMD) method to decompose the signals. Second, the time-frequency analysis methods, which include the Short-Time Fourier Transform (STFT) and time-frequency entropy calculation, are applied to realize the robust feature extraction. Third, the multiclass Support Vector Machine (SVM) classifier is introduced to automatically classify the fault mode in this paper. An actual hydraulic-pump experiment demonstrates the procedure with a complete feature extraction and accurate mode classification. Wanlin Zhao, Zili Wang, Jian Ma, and Lianfeng Li Copyright © 2016 Wanlin Zhao et al. All rights reserved. The Use of Vibration Signals for Structural Health Monitoring, System Identification, Test Planning/Optimization, and Dynamic Model Validation/Updating Mon, 26 Sep 2016 08:16:27 +0000 Samuel da Silva, Michael Todd, John S. Sakellariou, and Maryam Ghandchi-Tehrani Copyright © 2016 Samuel da Silva et al. All rights reserved. Multiple Moving Targets Detection and Parameters Estimation in Strong Reverberation Environments Thu, 22 Sep 2016 06:19:14 +0000 This paper considers the problem of multiple moving targets detection and parameters estimation (direction of arrival and range) in strong reverberation environments. As reverberation has a strong correlation with target echo, the performance of target detection and parameters estimation is significantly degraded in practical underwater environments. In this paper, we utilize two uniform circular arrays to receive plane wave of the linear frequency modulation signal reflected from far-field targets. On the basis of received signal, we build a variance matrix of multiple beams by using modal decomposition, conventional beamforming, and fractional Fourier transform (FrFT). We then propose a novel detection method and an estimation method of parameters based on the constructed image. A significant feature of the proposed methods is that our design does not involve any a priori knowledge about targets number and parameters of marine environments. Finally, we demonstrate via numerical simulation examples that the detection probability and the accuracy of estimated parameters of the proposed method are higher than the existing methods in both low signal-to-reverberation ratio and signal-to-noise ratio environment. Ge Yu and Shengchun Piao Copyright © 2016 Ge Yu and Shengchun Piao. All rights reserved. Hybrid Vibration Control under Broadband Excitation and Variable Temperature Using Viscoelastic Neutralizer and Adaptive Feedforward Approach Wed, 21 Sep 2016 12:19:56 +0000 Vibratory phenomena have always surrounded human life. The need for more knowledge and domain of such phenomena increases more and more, especially in the modern society where the human-machine integration becomes closer day after day. In that context, this work deals with the development and practical implementation of a hybrid (passive-active/adaptive) vibration control system over a metallic beam excited by a broadband signal and under variable temperature, between 5 and 35°C. Since temperature variations affect directly and considerably the performance of the passive control system, composed of a viscoelastic dynamic vibration neutralizer (also called a viscoelastic dynamic vibration absorber), the associative strategy of using an active-adaptive vibration control system (based on a feedforward approach with the use of the FXLMS algorithm) working together with the passive one has shown to be a good option to compensate the neutralizer loss of performance and generally maintain the extended overall level of vibration control. As an additional gain, the association of both vibration control systems (passive and active-adaptive) has improved the attenuation of vibration levels. Some key steps matured over years of research on this experimental setup are presented in this paper. João C. O. Marra, Eduardo M. O. Lopes, José João de Espíndola, and Walter Antônio Gontijo Copyright © 2016 João C. O. Marra et al. All rights reserved. Vibration Analysis of Aeroengine Blisk Structure Based on a Prestressed CMS Super-Element Method Tue, 20 Sep 2016 12:32:16 +0000 For vibration analysis of aeroengine blisk structure, a prestressed component modal synthesis (CMS) super-element method is put forward with the fixed interface prestressing and free interface super-element approach. Based on this method, natural vibration characteristics of blisk structure are calculated at different modal truncation numbers. Comparing with the accurate result of global method, the selection principle of modal truncation number is obtained which affects the accuracy of prestressed CMS super-element method. Vibration response of two-stage blisk structure is calculated by this method, and the effects of different blade aspect ratios have been discussed on vibration characteristics. The results show that prestressed CMS super-element method is in the high accuracy and efficiency on blisk vibration analysis. Resonant frequencies in vibration response are nearly the same between the first-stage blisk and the second-stage blisk, and they are both approximately located in the range 588 Hz–599 Hz. The maximum displacement and dynamic stress are at blade tip and root of the first-stage blisk, respectively. Blade aspect ratio is a key factor of blisk vibration; the effects of blade aspect ratio on natural frequencies are different in the conditions of fixed width and fixed length. This research provides the theoretical basis for dynamic design of aeroengine compressor rotor system. Zhijun Li, Wenjun Yang, and Huiqun Yuan Copyright © 2016 Zhijun Li et al. All rights reserved. An Approach to Fault Diagnosis for Gearbox Based on Image Processing Tue, 20 Sep 2016 11:16:13 +0000 The gearbox is one of the most important parts of mechanical equipment and plays a significant role in many industrial applications. A fault diagnostic of rotating machinery has attracted attention for its significance in preventing catastrophic accidents and beneficially guaranteeing sufficient maintenance. In recent years, fault diagnosis has developed in the direction of multidisciplinary integration. This work addresses a fault diagnosis method based on an image processing method for a gearbox, which overcomes the limitations of manual feature selection. Differing from the analysis method in a one-dimensional space, the computing method in the field of image processing in a 2-dimensional space is applied to accomplish autoextraction and fault diagnosis of a gearbox. The image-processing-based diagnostic flow consists of the following steps: first, the vibration signal after noise reduction by wavelet denoising and signal demodulation by Hilbert transform is transformed into an image by bispectrum analysis. Then, speeded up robustness feature (SURF) is applied to automatically extract the image feature points of the bispectrum contour map, and the feature dimension is reduced by principal component analysis (PCA). Finally, an extreme learning machine (ELM) is introduced to identify the fault types of the gearbox. From the experimental results, the proposed method appears to be able to accurately diagnose and identify different types of faults of the gearbox. Yang Wang and Yujie Cheng Copyright © 2016 Yang Wang and Yujie Cheng. All rights reserved. Algorithm Indicating Moment of P-Wave Arrival Based on Second-Moment Characteristic Tue, 20 Sep 2016 10:57:44 +0000 The moment of P-wave arrival can provide us with many information about the nature of a seismic event. Without adequate knowledge regarding the onset moment, many properties of the events related to location, polarization of P-wave, and so forth are impossible to receive. In order to save time required to indicate P-wave arrival moment manually, one can benefit from automatic picking algorithms. In this paper two algorithms based on a method finding a regime switch point are applied to seismic event data in order to find P-wave arrival time. The algorithms are based on signals transformed via a basic transform rather than on raw recordings. They involve partitioning the transformed signal into two separate series and fitting logarithm function to the first subset (which corresponds to pure noise and therefore it is considered stationary), exponent or power function to the second subset (which corresponds to nonstationary seismic event), and finding the point at which these functions best fit the statistic in terms of sum of squared errors. Effectiveness of the algorithms is tested on seismic data acquired from O/ZG “Rudna” underground copper ore mine with moments of P-wave arrival initially picked by broadly known STA/LTA algorithm and then corrected by seismic station specialists. The results of proposed algorithms are compared to those obtained using STA/LTA. Jakub Sokolowski, Jakub Obuchowski, Radoslaw Zimroz, Agnieszka Wylomanska, and Eugeniusz Koziarz Copyright © 2016 Jakub Sokolowski et al. All rights reserved.