Shock and Vibration The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Vibration Control of the Boom System of Truck-Mounted Concrete Pump Based on Constant-Position Commandless Input Shaping Technique Thu, 02 Jul 2015 11:38:22 +0000 Vibration of the boom system is inevitably caused by periodic disturbances, which are induced by pumping concrete. In this paper, an active control strategy of constant-position commandless input shaping technique is developed to suppress vibration. Based on a set of independent modal equations obtained by adopting modal approach, the double-impulse control with reverse direction is proposed, which is aiming at not only suppressing vibration, but also avoiding the variation of the equilibrium position of the boom system after active control action. And the characteristic of time-lag existing in real system is also taken into account for optimizing the control action. Experiments of vibration control were implemented on a 52-meter-long five-boom system to verify the proposed control strategy. Rongsheng Liu, Yingjie Gao, Sen Yang, and Yulin Yang Copyright © 2015 Rongsheng Liu et al. All rights reserved. Distributed Sensor Networks for Health Monitoring of Civil Infrastructures Mon, 29 Jun 2015 06:10:50 +0000 Ting-Hua Yi, Gangbing Song, Stathis C. Stiros, and Bo Chen Copyright © 2015 Ting-Hua Yi et al. All rights reserved. Fault Diagnosis of Bearing Based on Cauchy Kernel Relevance Vector Machine Classifier with SIWPSO Sun, 28 Jun 2015 10:14:09 +0000 Bearing is an important component of mechanical system; any defects of bearing will lead to serious damage for the entire mechanical system. In this paper, Cauchy kernel relevance vector machine with stochastic inertia weight particle swarm optimization algorithm (SIWPSO-CauchyRVM) is proposed to fault diagnosis for bearing. As the selection of the Cauchy kernel parameter has a certain influence on the diagnosis result of relevance vector machine, stochastic inertia weight PSO is used to select the Cauchy kernel parameter. The relative energies of 16 wavelet coefficients of the forth layer of vibration signal of bearing can be used as the diagnosis features of bearing. The experimental results indicate that fault diagnosis method of bearing based on SIWPSO-CauchyRVM has excellent diagnosis ability. Sheng-wei Fei and Yong He Copyright © 2015 Sheng-wei Fei and Yong He. All rights reserved. Dynamic Finite Element Analysis of Bending-Torsion Coupled Beams Subjected to Combined Axial Load and End Moment Thu, 25 Jun 2015 10:30:31 +0000 The dynamic analysis of prestressed, bending-torsion coupled beams is revisited. The axially loaded beam is assumed to be slender, isotropic, homogeneous, and linearly elastic, exhibiting coupled flexural-torsional displacement caused by the end moment. Based on the Euler-Bernoulli bending and St. Venant torsion beam theories, the vibration and stability of such beams are explored. Using the closed-form solutions of the uncoupled portions of the governing equations as the basis functions of approximation space, the dynamic, frequency-dependent, interpolation functions are developed, which are then used in conjunction with the weighted residual method to develop the Dynamic Finite Element (DFE) of the system. Having implemented the DFE in a MATLAB-based code, the resulting nonlinear eigenvalue problem is then solved to determine the coupled natural frequencies of illustrative beam examples, subjected to various boundary and load conditions. The proposed method is validated against limited available experimental and analytical data, those obtained from an in-house conventional Finite Element Method (FEM) code and FEM-based commercial software (ANSYS). In comparison with FEM, the DFE exhibits higher convergence rates and in the absence of end moment it produces exact results. Buckling analysis is also carried out to determine the critical end moment and compressive force for various load combinations. Mir Tahmaseb Kashani, Supun Jayasinghe, and Seyed M. Hashemi Copyright © 2015 Mir Tahmaseb Kashani et al. All rights reserved. Transmission of Impact Vibration on Concrete and Mortar Sheets Thu, 25 Jun 2015 09:16:13 +0000 The present work exposes an alternative system for detecting vibrations generated by impact on concrete and mortar sheets. In order to carry out the tests it is necessary to implement a system of measurement different than the one proposed by the current UNE EN 140-7. This system consists of an amplifier and a striking device that is also able to measure the deformation of the material once the impact has been produced. This system is able to detect variations in transmission of vibration at the same frequency between the various building materials employed, after establishing a relationship between the theoretical predictions and the experimental results. Thus, this system could be used as a vibration detection system and as an alternative method of standardization of materials against their acoustic characteristics. Carlos Morón, Alfonso García, Daniel Ferrández, and Víctor Blanco Copyright © 2015 Carlos Morón et al. All rights reserved. A New Approach for Symmetry Preserving Partial Eigenstructure Assignment of Undamped Vibrating Systems Wed, 24 Jun 2015 08:25:27 +0000 A new approach for the partial eigenvalue and eigenstructure assignment of undamped vibrating systems is developed. This approach deals with the constant output feedback control with the collocated actuator and sensor configuration, and the output matrix is also considered as a design parameter. It only needs those few eigenpairs to be assigned as well as mass and stiffness matrices of the open-loop vibration system and is easy to implement. In addition, this approach preserves symmetry of the systems. Numerical example demonstrates the effectiveness and accuracy of the proposed approach. Zhigang Hu, Jiafan Zhang, Hongjun Yang, and Guoquan Wang Copyright © 2015 Zhigang Hu et al. All rights reserved. Optimization of Vibration Reduction Ability of Ladder Tracks by FEM Coupled with ACO Tue, 23 Jun 2015 09:48:23 +0000 Ladder track, which has drawn increased attention in scientific communities, is an effective method for reducing vibrations from underground railways. In order to optimize the vibration reduction ability of ladder track, a new method, that is, the finite element method (FEM) coupled with ant colony optimization (ACO), has been proposed in this paper. We describe how to build the FEM model verified by the vibration tests in the Track Vibration Abatement and Control Laboratory and how to couple the FEM with ACO. The density and elasticity modulus of the sleeper pad are optimized using this method. After optimization, the vibration acceleration level of the supporting platform in the 1–200 Hz range was reduced from 102.8 dB to 94.4 dB. The optimized density of the sleeper pad is 620 kg/m3, and the optimized elasticity modulus of the sleeper pad is 6.25 × 106 N/m2. Hao Jin, Weining Liu, and Shunhua Zhou Copyright © 2015 Hao Jin et al. All rights reserved. Ultimate Strength of Fixed Offshore Platforms Subjected to Near-Fault Earthquake Ground Vibration Mon, 22 Jun 2015 06:10:50 +0000 The pile foundation nonlinearity and its influence on the ultimate capacity of fixed platforms have not comprehensively been covered by previous researchers. In this study, the seismic behavior and capacity of a newly designed and installed Jacket Type Offshore Platform (JTOP) located in the Persian Gulf is investigated by conducting Incremental Dynamic Analysis (IDA) using a suit of near-fault ground motions. Additionally, two modified models of the original platform are created by slightly increasing the diameter of the pile foundation and also softening the jacket part for evaluating the importance of the pile foundation and seismic soil-pile structure interaction on the dynamic characteristics of the JTOPs. Valuable discussions are provided to explore various aspects of the dynamic behavior of JTOPs by presenting individual and multirecords IDA curves using effective Engineering Demand Parameters (EDPs). Comparing the results of the three platform collapse fragility curves, it is concluded that the pile foundation plays a very important role in the dynamic response of offshore platforms and can drastically alter the ultimate strength of the platform together with its collapse capacity. It is observed that the proportional distribution of nonlinear behavior in the pile foundation and jacket part is the key factor in the enhancement of the ultimate strength of JTOPs. On the basis of the results derived from this paper, it is recommended that some basic requirements should be developed in order to ensure that the coupling ductility of pile foundation and jacket part is optimized during the design process. Furthermore, according to the findings from this study, some practice recommendations are presented to be devised within the design step. Hesam Sharifian, Khosro Bargi, and Mohamad Zarrin Copyright © 2015 Hesam Sharifian et al. All rights reserved. Experimental and Simulation Analysis for the Impact of a Two-Link Chain with Granular Matter Sun, 21 Jun 2015 07:28:18 +0000 The resistance force of the granular matter is modeled as a linear superposition of a static (quadratic depth-dependent) resistance force and a dynamic (quadratic velocity-dependent) frictional force. The impact is defined from the moment the end point of the system comes in contact with the granular matter surface until the vertical linear velocity of the end point is zero. The variables of interest are the final depth at the end of the penetration phase and the stopping time. The results for a two-link kinematic chain with two points of contact were compared to the results obtained by applying the resistance force formulation developed to corresponding CAD simulation models. The results revealed that the final displacement increases with initial velocity, while the stopping time decreases. The sensitivity to the initial velocity was studied and an improvement to the resistance force formulated as a result. A series of expressions are proposed for the resistance force coefficients. Eliza A. Banu and Dan B. Marghitu Copyright © 2015 Eliza A. Banu and Dan B. Marghitu. All rights reserved. Application of Self-Adaptive Wavelet Ridge Demodulation Method Based on LCD to Incipient Fault Diagnosis Sun, 21 Jun 2015 07:03:38 +0000 When a local defect occurs in gearbox, the vibration signals present as the form of multicomponent amplitude modulation and frequency modulation (AM-FM). Demodulation analysis is an effective way for this kind of signal. A self-adaptive wavelet ridge demodulation method based on LCD is proposed in this paper. Firstly, multicomponent AM-FM signal is decomposed into series of intrinsic scale components (ISCs) and the special intrinsic scale component is selected in order to decrease the lower frequency background noise. Secondly, the genetic algorithm is employed to optimize wavelet parameters according to the inherent characteristics of signal; thirdly, self-adaptive wavelet ridge demodulation wavelet for the selected ISC component is performed to get instantaneous amplitude (IA) or instantaneous frequency (IF). Lastly, the characteristics frequency can be obtained to identify the working state or failure information from its spectrum. By two simulation signals, the proposed method was compared with various existing demodulation methods; the simulation results show that it has higher accuracy and higher noise tolerant performance than others. Furthermore, the proposed method was applied to incipient fault diagnosis for gearbox and the results show that it is simple and effective. Songrong Luo, Junsheng Cheng, and Jianping Fu Copyright © 2015 Songrong Luo et al. All rights reserved. Three-Dimensional Vibration Analysis of Isotropic and Orthotropic Open Shells and Plates with Arbitrary Boundary Conditions Thu, 18 Jun 2015 12:23:15 +0000 This paper presents elasticity solutions for the vibration analysis of isotropic and orthotropic open shells and plates with arbitrary boundary conditions, including spherical and cylindrical shells and rectangular plates. Vibration characteristics of the shells and plates have been obtained via a unified three-dimensional displacement-based energy formulation represented in the general shell coordinates, in which the displacement in each direction is expanded as a triplicate product of the cosine Fourier series with the addition of certain supplementary terms introduced to eliminate any possible jumps with the original displacement function and its relevant derivatives at the boundaries. All the expansion coefficients are then treated equally as independent generalized coordinates and determined by the Rayleigh-Ritz procedure. To validate the accuracy of the present method and the corresponding theoretical formulations, numerical cases have been compared against the results in the literature and those of 3D FE analysis, with excellent agreements obtained. The effects of boundary conditions, material parameters, and geometric dimensions on the frequencies are discussed as well. Finally, several 3D vibration results of isotropic and orthotropic open spherical and cylindrical shells and plates with different geometry dimensions are presented for various boundary conditions, which may be served as benchmark solutions for future researchers as well as structure designers in this field. Guoyong Jin, Tiangui Ye, and Shuangxia Shi Copyright © 2015 Guoyong Jin et al. All rights reserved. Payload Mass Identification of a Single-Link Flexible Arm Moving under Gravity: An Algebraic Identification Approach Thu, 18 Jun 2015 06:42:53 +0000 We deal with the online identification of the payload mass carried by a single-link flexible arm that moves on a vertical plane and therefore is affected by the gravity force. Specifically, we follow a frequency domain design methodology to develop an algebraic identifier. This identifier is capable of achieving robust and efficient mass estimates even in the presence of sensor noise. In order to highlight its performance, the proposed estimator is experimentally tested and compared with other classical methods in several situations that resemble the most typical operation of a manipulator. Juan Carlos Cambera, Andres San-Millan, and Vicente Feliu-Batlle Copyright © 2015 Juan Carlos Cambera et al. All rights reserved. Failure Mechanism Analysis and Support Design for Deep Composite Soft Rock Roadway: A Case Study of the Yangcheng Coal Mine in China Wed, 17 Jun 2015 11:57:00 +0000 This paper presented a case study of the failure mechanisms and support design for deep composite soft rock roadway in the Yangcheng Coal Mine of China. Many experiments and field tests were performed to reveal the failure mechanisms of the roadway. It was found that the surrounding rock of the roadway was HJS complex soft rock that was characterized by poor rock quality, widespread development of joint fissures, and an unstable creep property. The major horizontal stress, which was almost perpendicular to the roadway, was 1.59 times larger than the vertical stress. The weak surrounding rock and high tectonic stress were the main internal causes of roadway instabilities, and the inadequate support was the external cause. Based on the failure mechanism, a new support design was proposed that consisted of bolting, cable, metal mesh, shotcrete, and grouting. A field experiment using the new design was performed in a roadway section approximately 100 m long. Detailed deformation monitoring was conducted in the experimental roadway sections and sections of the previous roadway. The monitoring results showed that deformations of the roadway with the new support design were reduced by 85–90% compared with those of the old design. This successful case provides an important reference for similar soft rock roadway projects. Bangyou Jiang, Lianguo Wang, Yinlong Lu, Shitan Gu, and Xiaokang Sun Copyright © 2015 Bangyou Jiang et al. All rights reserved. Early-Warning Method of Train Running Safety of a High-Speed Railway Bridge Based on Transverse Vibration Monitoring Wed, 17 Jun 2015 06:44:24 +0000 Making use of long-term transverse vibration monitoring data of DaShengGuan Bridge, the early-warning method of train running safety of the high-speed railway bridge is established by adopting principal component analysis (PCA) method. Firstly, the root mean square (RMS) of the transverse acceleration of the main girder is used as the monitoring parameter for the train running safety. The correlation model between the RMS values measured from different positions is further adopted as the evaluating model for the train running safety. Finally, the effects of the environmental changes on the evaluating model are eliminated using the PCA method and the warning index for the train running safety is further constructed. The analysis results show that the correlation between the RMS values of the accelerations from different measuring positions on the main girder can be analyzed by a quadratic polynomial fitting model. The PCA method can effectively remove the environmental effects on the quadratic polynomial fitting model. The proposed warning method provides a good capability for detecting the abnormal changes of the measured transverse accelerations and hence it is suitable for early-warning of the train running safety. You-Liang Ding, Peng Sun, Gao-Xin Wang, Yong-Sheng Song, Lai-Yi Wu, Qing Yue, and Ai-Qun Li Copyright © 2015 You-Liang Ding et al. All rights reserved. Similarity Analysis between Scale Model and Prototype of Large Vibrating Screen Mon, 15 Jun 2015 07:02:27 +0000 In order to predict the physical characteristics of the large vibrating screen from its scale-down model, the similarity ratios of the frequency response functions, mode shapes, and dynamic stresses between the prototype and the scale model screen are built according to the similarity theory. The natural frequencies and modal shapes are extracted from the frequency response function by means of modal tests, in which the relative error of the natural frequencies is less than 9% and the modal shapes are consistent between the prototype and the model. The operating condition parameters including dynamic stress, displacement, velocity, and acceleration were also measured and conform to the similarity criteria. The results show that the inherent and operating condition parameters of the large vibrating screen can be obtained from the scale-down model conveniently, which provides an effective method for structural optimization and substructure coupling analysis of the large vibrating screen. Zerong Zhang, Yongyan Wang, and Zhimin Fan Copyright © 2015 Zerong Zhang et al. All rights reserved. Seismic Response Reduction of Structures Equipped with a Voided Biaxial Slab-Based Tuned Rolling Mass Damper Sun, 14 Jun 2015 07:36:01 +0000 This paper proposes a novel tuned mass damper (TMD) embedded in hollow slabs of civil structures. The hollow slabs in this context, also referred to as “voided biaxial reinforced concrete slabs,” feature a large interior space of prefabricated voided modules that are necessary in the construction of this special structural system. In this regard, a tuned rolling mass damper system (“TRoMaDaS”) is newly proposed, in combination with hollow slabs, to act as an ensemble passive damping device mitigating structural responses. The main advantage of this TMD configuration lies in its capacity to maintain architectural integrity. To further investigate the potential application of the proposed TRoMaDaS in seismic response mitigation, theoretical and numerical studies, including deterministic and stochastic analyses, were performed. They were achieved by deterministic dynamic modeling using Lagrange’s equation and the statistical linearization method. Finally, the promising control efficacy obtained from the deterministic/stochastic analysis confirmed the potential application of this newly proposed control device. Shujin Li, Liming Fu, and Fan Kong Copyright © 2015 Shujin Li et al. All rights reserved. A Comparative Study of Genetic and Firefly Algorithms for Sensor Placement in Structural Health Monitoring Tue, 09 Jun 2015 13:10:08 +0000 Optimal sensor placement (OSP) is an important task during the implementation of sophisticated structural health monitoring (SHM) systems for large-scale structures. In this paper, a comparative study between the genetic algorithm (GA) and the firefly algorithm (FA) in solving the OSP problem is conducted. To overcome the drawback related to the inapplicability of the FA in optimization problems with discrete variables, some improvements are proposed, including the one-dimensional binary coding system, the Hamming distance between any two fireflies, and the semioriented movement scheme; also, a simple discrete firefly algorithm (SDFA) is developed. The capabilities of the SDFA and the GA in finding the optimal sensor locations are evaluated using two disparate objective functions in a numerical example with a long-span benchmark cable-stayed bridge. The results show that the developed SDFA can find the optimal sensor configuration with high reliability. The comparative study indicates that the SDFA outperforms the GA in terms of algorithm complexity, computational efficiency, and result quality. The optimization mechanism of the FA has the potential to be extended to a wide range of optimization problems. Guang-Dong Zhou, Ting-Hua Yi, Huan Zhang, and Hong-Nan Li Copyright © 2015 Guang-Dong Zhou et al. All rights reserved. Elliptical Leaf Spring Shock and Vibration Mounts with Enhanced Damping and Energy Dissipation Capabilities Using Lead Spring Tue, 09 Jun 2015 07:57:14 +0000 We present an enhancement to the existing elliptical leaf spring (ELS) for improved damping and energy dissipation capabilities. The ELS consists of a high tensile stainless steel elliptical leaf spring with polymer or rubber compound. This device is conceived as a shock and vibration isolator for equipment and lightweight structures. The enhancement to the ELS consists of a lead spring plugged vertically between the leaves (referred to as lead-rubber elliptical leaf spring (LRELS)). The lead is shown to produce hysteretic damping under plastic deformations. The LRELS isolator is shown to exhibit nonlinear hysteretic behavior. In both horizontal directions, the LRELS showed symmetrical rate independent behavior but undergoes stiffening behavior under large displacements. However, in the vertical direction, the LRELS behavior is asymmetric, exhibiting softening behavior in compression and stiffening behavior in tension. Mathematical models based on the Bouc-Wen model, describing the hysteretic behavior of the proposed isolator, are developed and numerically calibrated using a series of finite element analyses. The LRELS is found to be effective in the in-plane and vertical directions. The improved damping and energy dissipation of the LRELS is provided from the hysteretic damping of the lead spring. Moussa Leblouba, Salah Altoubat, Muhammad Ekhlasur Rahman, and Balaji Palani Selvaraj Copyright © 2015 Moussa Leblouba et al. All rights reserved. Effect of the Location of the Detonation Initiation Point for Bench Blasting Thu, 04 Jun 2015 11:07:40 +0000 Uneven floor and fragmentation play an important role in blasting operations due to the direct effects on the efficiency of hauling and loading. This paper focuses on the influences of initiation position on bench blasting in order to improve blasting effects. The numerical simulations of bench blasting at different initiation points (top, middle, and bottom) are implemented based on secondary development of LS-DYNA with a tensile-compressive damage model. The damage spatial distribution characteristics of different initiation points are compared. The outlines of rock foundation and boulder areas are analyzed with the damage threshold of critical breakage that is ascertained by acoustic characteristic of damage rock mass. Results of the numerical simulations demonstrate that different initiation points make a great influence on the stress and energy distribution in blasting process and induce different blasting effects. Middle initiation turns out to be the best initiation to increase the flatness of the floor and decrease the oversize boulder ratio simultaneously, which will increase the damage areas of the bottom and top regions and give a better blasting effect. Field experiment in Baihetan Station was carried out to validate conclusions of numerical simulation. Research could provide a good reference for the improvement of rock blasting. Liang Liu, Ming Chen, Wenbo Lu, Yingguo Hu, and Zhendong Leng Copyright © 2015 Liang Liu et al. All rights reserved. Determination of the Strain-Free Configuration of Multispan Cable Thu, 04 Jun 2015 07:10:50 +0000 For building a reasonable finite element geometric model, a method is proposed to determine the strain-free configuration of the multispan cable. The geometric conditions (the end conditions and the unstretched length conditions) as constraints for the configuration of multispan cable are given. Additionally, asymptotic static equilibrium conditions are given for determining the asymptotic shape of the multispan cable. By solving these constraint equations, a set of parameters are determined and then the strain-free configuration of multispan cable is determined. The method reported in this paper provides a technique for building reasonable FEA geometric model of multispan cables. Finally, a three-span cable is taken as example to illustrate the effectiveness of the method, and the computed results are validated via the software ADINA. Chuancai Zhang, Qiang Guo, and Xinhua Zhang Copyright © 2015 Chuancai Zhang et al. All rights reserved. Control Mechanism of Rock Burst in the Floor of Roadway Driven along Next Goaf in Thick Coal Seam with Large Obliquity Angle in Deep Well Wed, 03 Jun 2015 12:17:47 +0000 This paper deals with the theoretical aspects combined with stress analysis over the floor strata of coal seam and the calculation model for the stress on the coal floor. Basically, this research presents the relevant results obtained for the rock burst prevention in the floor of roadway driven along next goaf in the exploitation of thick coal seam with large obliquity in deep well and rock burst tendency. The control mechanism of rock burst in the roadway driven along next goaf is revealed in the present work. That is, the danger of rock burst can be removed by changing the stress environment for the energy accumulation of the floor and by reducing the impact on the roadway floor from the strong dynamic pressure. This result can be profitable being used at the design stage of appropriate position of roadway undergoing rock burst tendency in similar conditions. Based on the analysis regarding the control mechanism, this paper presents a novel approach to the prevention of rock burst in roadway floor under the above conditions. That is, the return airway is placed within the goaf of the upper working face that can prevent the rock burst effectively. And in this way, mining without coal pillar in the thick coal seam with large obliquity and large burial depth (over a thousand meters) is realized. Practice also proves that the rock burst in the floor of roadway driven along next goaf is controlled and solved. Yunhai Cheng, Jinchao Bai, Yankun Ma, Jian Sun, Yunpei Liang, and Fuxing Jiang Copyright © 2015 Yunhai Cheng et al. All rights reserved. Integrated Topology Optimization of Structure/Vibration Control for Piezoelectric Cylindrical Shell Based on the Genetic Algorithm Mon, 01 Jun 2015 13:57:15 +0000 A hybrid optimization strategy for integrated topological optimization design of piezoelectric cylindrical flat shell structure is proposed. The method combines the genetic algorithm (GA) and linear-quadratic-regulator (LQR) theory to optimize the performance of coupling structure/control system. The GA is used to choose the optimal structure topology and number and placements of actuators and control parameters; meanwhile, the LQR is used to design control system to suppress vibration of optimal structure under sinusoidal excitation, which is based on the couple-mode space control. In addition, the mathematical morphology operators are used for repairs of disconnected structure topology. The results of numerical simulation and computations show that the proposed method is effective and feasible, with good performance for the optimal and coupling piezoelectric cylindrical shell structure/control system. Jianjun He and Xiangzi Chen Copyright © 2015 Jianjun He and Xiangzi Chen. All rights reserved. Unbalance Identification of Speed-Variant Rotary Machinery without Phase Angle Measurement Sun, 31 May 2015 11:57:23 +0000 As rotary mechanical structure becomes more complicated, difficulty arises in receiving prime correction mass and optimum balancing plane efficiently. An innovative modal balancing process for estimating the residual unbalance from different equilibrium plane of complex flexible rotor system is presented. The method is based on a numerical approach with modal ratio among measurement points (MRMP) coefficient and triple phase method (TPM). The veracity of calculation result is verified by an academic rotor model. The latter study in this paper is subsequently put forward through a power turbine rotor modeled by finite element method. Simulation results show that proper equilibrium plane performs commendably in recognizing residual unbalance and reducing the vibration effect through the critical region. Moreover, the inherent unbalance recognized by experimental data from a turbine rotor with slender shaft is found to be in certain difference under different counterweight combination. Choosing suitable balancing planes will improve the accuracy of unbalance identification. Cong Yue, Xingmin Ren, Yongfeng Yang, and Wangqun Deng Copyright © 2015 Cong Yue et al. All rights reserved. A Spatial Euler-Bernoulli Beam Element for Rigid-Flexible Coupling Dynamic Analysis of Flexible Structures Sun, 31 May 2015 06:50:03 +0000 A two-node spatial beam element with the Euler-Bernoulli assumption is developed for the nonlinear dynamic analysis of slender beams undergoing arbitrary rigid motions and large deformations. During the analysis, the global displacement and rotation vectors with six degrees of freedom are selected as the nodal coordinates. In addition, the “shear locking” problem is avoided successfully since the beam cross-sections are always perpendicular to the current neutral axes by employing a special coupled interpolation of the centroid position and the cross-section orientation. Then a scheme is presented where the original transient strains representing the nodal forces are replaced by proposed average strains over a small time interval. Thus all the high frequencies can be filtered out and a corresponding equivalent internal damping will be produced in this new formulation, which can improve the computation performance of the proposed element for solving the stiff problem and evaluate the governing equations even by using the nonstiff ordinary differential equation solver. Finally, several numerical examples are carried out to verify the validation and efficiency of this proposed formulation by comparison with the analytical solutions and other research works. Zhigang Zhang, Zhaohui Qi, Zhigang Wu, and Huiqing Fang Copyright © 2015 Zhigang Zhang et al. All rights reserved. GPC-Based Gust Response Alleviation for Aircraft Model Adapting to Various Flow Velocities in the Wind Tunnel Sun, 31 May 2015 06:35:01 +0000 A unified autoregressive (AR) model is identified, based on the wind tunnel test data of open-loop gust response for an aircraft model. The identified AR model can be adapted to various flow velocities in the wind tunnel test. Due to the lack of discrete gust input measurement, a second-order polynomial function is used to approximate the gust input amplitude by flow velocity. Afterwards, with the identified online aeroelastic model, the modified generalized predictive control (GPC) theory is applied to alleviate wing tip acceleration induced by sinusoidal gust. Finally, the alleviation effects of gust response at different flow velocities are estimated based on the comparison of simulated closed-loop acceleration with experimental open-loop one. The comparison indicates that, after gust response alleviation, the wing tip acceleration can be reduced up to 20% at the tested velocities ranging from 12 m/s to 24 m/s. Demonstratively, the unified control law can be adapted to varying wind tunnel velocities and gust frequencies. It does not need to be altered at different test conditions, which will save the idle time. Yuting Dai and Chao Yang Copyright © 2015 Yuting Dai and Chao Yang. All rights reserved. Dynamic Response of Rub Caused by a Shedding Annular Component Happening in a Steam Turbine Thu, 28 May 2015 11:40:17 +0000 Rub caused by a shedding annular component is a severe fault happening in a steam turbine, which could result in a long-term wearing effect on the shaft. The shafting abrasion defects shortened the service life and damaged the unit. To identify the fault in time, the dynamic response of rub caused by a shedding annular component was studied as follows: (I) a rotor-bearing model was established based on the structural features of certain steam turbines; node-to-node contact constraint and penalty method were utilized to analyze the impact and friction; (II) dynamic response of the rotor-bearing system and the shedding component was simulated with the development of rub after the component was dropping; (III) fault features were extracted from the vibration near the bearing position by time-domain and frequency-domain analysis. The results indicate that the shedding annular component would not only rotate pivoting its axis but also revolve around the shaft after a period of time. Under the excitation of the contact force, the peak-peak vibration fluctuates greatly. The frequency spectrum contains two main components, that is, the working rotating frequency and revolving frequency. The same phenomenon was observed from the historical data in the field. J. M. Chen, D. X. Jiang, N. F. Wang, and S. P. An Copyright © 2015 J. M. Chen et al. All rights reserved. Shock and Vibration Induced by Mining Extraction Thu, 28 May 2015 08:03:40 +0000 Caiping Lu, Linming Dou, Nong Zhang, Marcin Aleksander Lutyński, and Shimin Liu Copyright © 2015 Caiping Lu et al. All rights reserved. Adaptive Hybrid Control of Vehicle Semiactive Suspension Based on Road Profile Estimation Wed, 27 May 2015 13:12:36 +0000 A new road estimation based suspension hybrid control strategy is proposed. Its aim is to adaptively change control gains to improve both ride comfort and road handling with the constraint of rattle space. To achieve this, analytical expressions for ride comfort, road handling, and rattle space with respect to road input are derived based on the hybrid control, and the problem is transformed into a MOOP (Multiobjective Optimization Problem) and has been solved by NSGA-II (Nondominated Sorting Genetic Algorithm-II). A new road estimation and classification method, which is based on ANFIS (Adaptive Neurofuzzy Inference System) and wavelet transforms, is then presented as a means of detecting the road profile level, and a Kalman filter is designed for observing unknown states. The results of simulations conducted with random road excitation show that the efficiency of the proposed control strategy compares favourably to that of a passive system. Yechen Qin, Mingming Dong, Reza Langari, Liang Gu, and Jifu Guan Copyright © 2015 Yechen Qin et al. All rights reserved. Experimental Study on the Shock Absorption Performance of Combined Aluminium Honeycombs under Impact Loading Wed, 27 May 2015 06:50:46 +0000 Shock absorption characteristics of combined aluminium honeycomb structures were studied experimentally. In the experiments, a testing platform was design to compare the shock absorption level of different honeycomb specimens quantitatively. The shock response curves of six test points mounted on the platform were recorded with acceleration sensors when the buffer was impacted by a bullet driven by high pressure gas. The maximum acceleration values in time domain and in specifically spectral domain were obtained based on spectral analysis. Comparing the data of combined aluminium honeycomb buffer and single aluminium honeycomb buffer, conclusion can be obtained that shock absorbing characteristic of combined aluminium honeycomb buffer is better. Furthermore, compression properties of three kinds of buffers were tested under quasi-static state. The energy absorption parameters were calculated. The results show suitable combined aluminium honeycomb buffer can smooth the stress and lower the energy applied to the testing platform. Lei Cao, Yuliang Lin, Fangyun Lu, Rong Chen, Zhifeng Zhang, and Yan Li Copyright © 2015 Lei Cao et al. All rights reserved. Impulse Force Balance for Ultrashort Duration Hypersonic Test Facilities Sun, 24 May 2015 11:31:46 +0000 This paper presents the measurement of side force, pitching, and yawing moments on a model, using an accelerometer force balance, in a short duration hypersonic shock tunnel. The test model is a blunt-nosed, flapped delta wing, mounted on a support sting through a force balance. The flexible rubber bushes constituting the balance allow the model to float freely on the sting during the test. The accelerometers were located in the model to record accelerations in the directions of interest. The model was tested in shock tunnel at Mach 8 at different angles of incidence with the freestream. Dynamic calibration of the test assembly was carried out for the acquisition of impulse response functions for the above components of force and moments, using an impulse hammer. The convolution technique was applied to derive the impulse response functions. The accelerometer outputs from the model in the hypersonic freestream were processed using the respective impulse response functions to derive the unknown aerodynamic force and moments. The newly adopted convolution technique has been found very effective for data reduction from accelerometer force balances developed for shock tunnel applications. P. Singh, V. Menezes, K. J. Irimpan, and H. Hosseini Copyright © 2015 P. Singh et al. All rights reserved.