Shock and Vibration http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Constant Cutting Force Control for CNC Machining Using Dynamic Characteristic-Based Fuzzy Controller Sun, 18 Jan 2015 07:17:32 +0000 http://www.hindawi.com/journals/sv/2015/406294/ This paper presents a dynamic characteristic-based fuzzy adaptive control algorithm (DCbFACA) to avoid the influence of cutting force changing rapidly on the machining stability and precision. The cutting force is indirectly obtained in real time by monitoring and extraction of the motorized spindle current, the feed speed is fuzzy adjusted online, and the current was used as a feedback to control cutting force and maintain the machining process stable. Different from the traditional fuzzy control methods using the experience-based control rules, and according to the complex nonlinear characteristics of CNC machining, the power bond graph method is implemented to describe the dynamic characteristics of process, and then the appropriate variation relations are achieved between current and feed speed, and the control rules are optimized and established based on it. The numerical results indicated that DCbFACA can make the CNC machining process more stable and improve the machining precision. Hengli Liu, Taiyong Wang, and Dong Wang Copyright © 2015 Hengli Liu et al. All rights reserved. Active Vibration Control of an Axially Translating Robot Arm with Rotating-Prismatic Joint Using Self-Sensing Actuator Thu, 15 Jan 2015 13:45:30 +0000 http://www.hindawi.com/journals/sv/2015/964139/ Active vibration control of an axially translating robot arm with rotating-prismatic joint using self-sensing actuator is investigated. The equations of the system are derived by Lagrange’s equation with the assumed mode method. The displacement and velocity control law is used to configure the self-sensing actuator, which provides the active damping and stiffness effect to the structure. The numerical simulations reveal that the tip deflection of the arm can be effectively reduced by the self-sensing actuator. The amplitude of sensor voltage is inversely proportional to the length of axially translating arm. And higher feedback control gain results in lower sensor voltages and vibration amplitudes. Liang Zhao and Zhen-Dong Hu Copyright © 2015 Liang Zhao and Zhen-Dong Hu. All rights reserved. A Coupling Vibration Test Bench and the Simulation Research of a Maglev Vehicle Thu, 15 Jan 2015 10:17:31 +0000 http://www.hindawi.com/journals/sv/2015/586910/ To study the characteristics of the coupling vibration between a maglev vehicle and its track beam system and to improve the performance of the levitation system, a new type of vibration test bench was developed. Take a single maglev frame as the study object; simulation of the coupling vibration of the maglev vehicle, levitation system, and track beam were achieved. In addition, all types of real track irregularity excitations can be simulated using hydraulic actuators of the test bench. To expand the research scope, a simulation model was developed that can conduct the simulation research synergistically with the test bench. Based on a dynamics model of the test bench, the dynamics simulation method determined the influence on the levitation control performance of three factors: the track beam support stiffness, the track beam mass, and the track irregularity. The vibration resonance phenomenon of the vehicle/track system was reproduced by the dynamics simulation, and a portion of the simulation results were validated by the test results. By combining the test bench and the dynamics model, experiments can be guided by the simulation results, and the experimental results can validate the dynamics simulation results. Weihua Ma, Rongrong Song, Junqi Xu, Yu Zang, and Shihui Luo Copyright © 2015 Weihua Ma et al. All rights reserved. Curvature Effects on the Vibration Characteristics of Doubly Curved Shallow Shells with General Elastic Edge Restraints Thu, 15 Jan 2015 06:41:46 +0000 http://www.hindawi.com/journals/sv/2015/435903/ Effects of curvature upon the vibration characteristics of doubly curved shallow shells are assessed in this paper. Boundary conditions of the shell are generally specified in terms of distributed elastic restraints along the edges. The classical homogeneous boundary supports can be easily simulated by setting the stiffnesses of restraining springs to either zero or infinite. Vibration problems of the shell are solved by a modified Fourier series method that each of the displacements is invariably expressed as a simple trigonometric series which converges uniformly and acceleratedly over the solution domain. All the unknown expansion coefficients are treated equally as a set of independent generalized coordinates and solved using the Rayleigh-Ritz technique. The current method provides a unified solution to the vibration problems of curved shallow shells involving different geometric properties and boundary conditions with no need of modifying the formulations and solution procedures. Extensive tabular and graphical results are presented to show the curvature effects on the natural frequencies of the shell with various boundary conditions. Hui Shi, Teijun Yang, Shiliang Jiang, W. L. Li, and Zhigang Liu Copyright © 2015 Hui Shi et al. All rights reserved. Theoretical Modelling and Effectiveness Study of Slotted Stand-Off Layer Damping Treatment for Rail Vibration and Noise Control Thu, 15 Jan 2015 06:38:56 +0000 http://www.hindawi.com/journals/sv/2015/716382/ A promising means of reducing railway noise is to increase the damping of the rail, which decreases the vibration of the rail to reduce noise. To achieve this goal, a slotted stand-off layer damping treatment has been developed, and a compound track model with this treatment is developed for investigating the effectiveness of this treatment in terms of the vibration reduction. Through the dynamic analysis of the track undergoing the slotted stand-off layer damping treatment, some guidelines are proposed on the selection of materials and structure parameters for this treatment. In addition, the prototype of the optimal slotted stand-off layer damping treatment has been built and tested in the laboratory. It is found that the slotted stand-off damping treatment shows significant effects in decreasing the amplitude of the accelerance of the rail and a significant reduction of sound emission reflected as the radiation sound pressure level decreases by 8.2 and 9.4 dB at vertical excitation and lateral excitation, respectively, in the frequency range of 0–4000 Hz. Caiyou Zhao and Ping Wang Copyright © 2015 Caiyou Zhao and Ping Wang. All rights reserved. Modeling and Application of Process Damping in Milling of Thin-Walled Workpiece Made of Titanium Alloy Thu, 15 Jan 2015 06:28:42 +0000 http://www.hindawi.com/journals/sv/2015/431476/ The modeling as well as application of process damping in milling of thin-walled workpiece made of titanium alloy is investigated. Titanium alloy used commonly in aviation industry is one typical difficult-to-machine material. Chatter usually occurs in cutting of titanium alloy, which results in poor surface quality and damaged tool. Thus, chatter is one important restriction for the quality and efficiency of titanium alloy manufacture, especially for the thin-walled workpiece made of titanium alloy due to poor structural stiffness. Process damping results from interference between flank face and machined surface, which is critical but usually ignored in chatter analysis for difficult-to-machine material. The paper presents one nonlinear dynamic model considering process damping for milling of thin-walled workpiece made of titanium alloy and designs antivibration clearance angle to suppress chatter based on the model. The experimental and computational results indicate that the presented methods for chatter stability analysis are reasonable, and the antivibration clearance angle designed is effective in suppressing chatter and improving machining quality. Xin Li, Wei Zhao, Liang Li, Ning He, and ShengWei Chi Copyright © 2015 Xin Li et al. All rights reserved. Vibration Response and Power Flow Characteristics of a Flexible Manipulator with a Moving Base Thu, 15 Jan 2015 06:11:42 +0000 http://www.hindawi.com/journals/sv/2015/589507/ Flexible manipulator generally can be modeled as a coupling system with a flexible beam and a rigid moving base. This paper investigates the vibration responses and power flow of a flexible manipulator with a moving base (FMMB). Considering the motion characteristics of the rigid base, the moving base is modeled to have a motion with disturbances, and the dynamic model of the FMMB is established. With the dynamic model, vibration responses of the FMMB for the rigid base having disturbance velocities and accelerations are specifically presented. Subsequently, to investigate the effect of the disturbances on the vibration energy distributions of the FMMB, power flow of the FMMB is exhibited. To verify the dynamic model, an ADAMS physical model of the FMMB is constructed. It reveals that the motion characteristics of the rigid base have a noticeable effect on the vibration responses and power flow of the FMMB and should be considered. The results are significant and contribute to the vibration control of flexible manipulators. Yufei Liu, Wei Li, Xuefeng Yang, Mengbao Fan, Yuqiao Wang, and En Lu Copyright © 2015 Yufei Liu et al. All rights reserved. Blade Crack Detection of Centrifugal Fan Using Adaptive Stochastic Resonance Wed, 14 Jan 2015 14:19:50 +0000 http://www.hindawi.com/journals/sv/2015/954932/ Centrifugal fans are widely used in various industries as a kind of turbo machinery. Among the components of the centrifugal fan, the impeller is a key part because it is used to transform kinetic energy into pressure energy. Crack in impeller’s blades is one of the serious hidden dangers. It is important to detect the cracks in the blades as early as possible. Based on blade vibration signals, this research applies an adaptive stochastic resonance (ASR) method to diagnose crack fault in centrifugal fan. The ASR method, which can utilize the optimization ability of the grid search method and adaptively realize the optimal stochastic resonance system matching input signals, may weaken the noise and highlight weak characteristic and thus can diagnose the fault accurately. A centrifugal fan test rig is established and experiments with three cases of blades are conducted. In comparison with the ensemble empirical mode decomposition (EEMD) analysis and the traditional Fourier transform method, the experiment verified the effectiveness of the current method in blade crack detection. Bingbing Hu and Bing Li Copyright © 2015 Bingbing Hu and Bing Li. All rights reserved. Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer Wed, 14 Jan 2015 13:54:18 +0000 http://www.hindawi.com/journals/sv/2015/476054/ The vibration-based damage identification method extracts the damage location and severity information from the change of modal properties, such as natural frequency and mode shape. Its performance and accuracy depends on the measurement precision. Laser Doppler vibrometer (LDV) provides a noncontact vibration measurement of high quality, but usually it can only do sampling on a single point. Scanning LDV is normally used to obtain the mode shape with a longer scanning time. In this paper, a damage detection technique is proposed using a self-synchronizing multipoint LDV. Multiple laser beams with various frequency shifts are projected on different points of the object, reflected and interfered with a common reference beam. The interference signal containing synchronized temporal vibration information of multiple spatial points is captured by a single photodetector and can be retrieved in a very short period. Experiments are conducted to measure the natural frequencies and mode shapes of pre- and postcrack cantilever beams. Mode shape curvature is calculated by numerical interpolation and windowed Fourier analysis. The results show that the artificial crack can be identified precisely from the change of natural frequencies and the difference of mode shape curvature squares. Chong Yang, Yu Fu, Jianmin Yuan, Min Guo, Keyu Yan, Huan Liu, Hong Miao, and Changchun Zhu Copyright © 2015 Chong Yang et al. All rights reserved. Active Magnetic Bearing Rotor Model Updating Using Resonance and MAC Error Wed, 14 Jan 2015 13:44:52 +0000 http://www.hindawi.com/journals/sv/2015/263062/ Modern control techniques can improve the performance and robustness of a rotor active magnetic bearing (AMB) system. Since those control methods usually rely on system models, it is important to obtain a precise rotor AMB analytical model. However, the interference fits and shrink effects of rotor AMB cause inaccuracy to the final system model. In this paper, an experiment based model updating method is proposed to improve the accuracy of the finite element (FE) model used in a rotor AMB system. Modelling error is minimized by applying a numerical optimization Nelder-Mead simplex algorithm to properly adjust FE model parameters. Both the error resonance frequencies and modal assurance criterion (MAC) values are minimized simultaneously to account for the rotor natural frequencies as well as for the mode shapes. Verification of the updated rotor model is performed by comparing the experimental and analytical frequency response. The close agreements demonstrate the effectiveness of the proposed model updating methodology. Yuanping Xu, Jin Zhou, Long Di, Chen Zhao, and Qintao Guo Copyright © 2015 Yuanping Xu et al. All rights reserved. Characteristics of Jerk Response Spectra for Elastic and Inelastic Systems Wed, 14 Jan 2015 13:40:37 +0000 http://www.hindawi.com/journals/sv/2015/782748/ Jerk is the time rate of acceleration and mainly represents the nonstationary component in high frequency band of the earthquake wave. The study on jerk and its response spectra can enhance the recognition of the nonstationary ground motion. The mechanical meaning and research value of jerk are described. Jerk is recommended to be solved by establishing state-space equations and Runge-Kutta method. The solution method of elastic and inelastic jerk response spectra under ground motion is established, and the accurate jerk spectrum should be calculated directly according to numerical computing instead of pseudo-acceleration spectrum. The characteristics of jerk response spectra are studied according to the influencing factors, such as site condition, amplification factor, ductility factor, and reduction factor. The concept of impact reduction factor is presented. The statistical results show that the jerk spectrum has similar rules as the acceleration spectrum, and the amplitude is relative to the predominant period, especially for structures with short or medium period. If the ductility is improved, the effective jerk will reduce obviously, and the impact reduction factor will be enhanced. Different from the strength reduction factor, the impact reduction factor is nearly not relevant to the period. Haoxiang He, Ruifeng Li, and Kui Chen Copyright © 2015 Haoxiang He et al. All rights reserved. The Health Monitoring Method of Concrete Dams Based on Ambient Vibration Testing and Kernel Principle Analysis Wed, 14 Jan 2015 13:38:36 +0000 http://www.hindawi.com/journals/sv/2015/342358/ The ambient vibration testing (AVT) measurement of concrete dams on full-scale can show the practical dynamic properties of structure in the operation state. For most current researches, the AVT data is generally analyzed to identify the structural vibration characteristics, that is, modal parameters. The identified modal parameters, which can provide the global damage information or the damage location information of structure, can be used as the basis of structure health monitoring. Therefore, in this paper, the health monitoring method of concrete dams based on the AVT is studied. The kernel principle analysis (KPCA) based method is adopted to eliminate the effect of environmental variables and monitor the health of dam under varying environments. By taking full advantage of the AVT data obtained from vibration observation system of dam, the identification capabilities and the warning capabilities of structural damage can be improved. With the simulated AVT data of the numerical model of a concrete gravity dam and the measured AVT data of a practical engineering, the performance of the dam health monitoring method proposed in this paper is verified. Lin Cheng, Jie Yang, Dongjian Zheng, Bo Li, and Jie Ren Copyright © 2015 Lin Cheng et al. All rights reserved. Operational Modal Identification of Time-Varying Structures via a Vector Multistage Recursive Approach in Hybrid Time and Frequency Domain Wed, 14 Jan 2015 13:38:03 +0000 http://www.hindawi.com/journals/sv/2015/397364/ Real-time estimation of modal parameters of time-varying structures can conduct an obvious contribution to some specific applications in structural dynamic area, such as health monitoring, damage detection, and vibration control; the recursive algorithm of modal parameter estimation supplies one of fundamentals for acquiring modal parameters in real-time. This paper presents a vector multistage recursive method of modal parameter estimation for time-varying structures in hybrid time and frequency domain, including stages of recursive estimation of time-dependent power spectra, frozen-time modal parameter estimation, recursive modal validation, and continuous-time estimation of modal parameters. An experimental example validates the proposed method finally. Si-Da Zhou, Li Liu, Wu Yang, and Zhi-Sai Ma Copyright © 2015 Si-Da Zhou et al. All rights reserved. Modal Appropriation for Use with In-Operation Modal Analysis Wed, 14 Jan 2015 13:27:34 +0000 http://www.hindawi.com/journals/sv/2015/537030/ We propose in this paper a numerical modal appropriation method for use with in-operation modal analysis (INOPMA). The key idea is to realize that the correlation sequence of the system output is the sum of decaying sinusoids with a certain phase shift and therefore it may be considered as an impulse response. The method is based on performing a numerical convolution of a single sine wave force with the system output correlation sequence. The steps are then similar to the classical modal appropriation method, although the characteristic frequencies are different. This approach is validated and compared to a subspace method on simulated data as well as on experimental data and it is shown that INOPMA outperforms the subspace method. M. Abdelghani and D. J. Inman Copyright © 2015 M. Abdelghani and D. J. Inman. All rights reserved. Decision Fusion System for Bolted Joint Monitoring Wed, 14 Jan 2015 07:46:33 +0000 http://www.hindawi.com/journals/sv/2015/592043/ Bolted joint is widely used in mechanical and architectural structures, such as machine tools, industrial robots, transport machines, power plants, aviation stiffened plate, bridges, and steel towers. The bolt loosening induced by flight load and environment factor can cause joint failure leading to a disastrous accident. Hence, structural health monitoring is critical for the bolted joint detection. In order to realize a real-time and convenient monitoring and satisfy the requirement of advanced maintenance of the structure, this paper proposes an intelligent bolted joint failure monitoring approach using a developed decision fusion system integrated with Lamb wave propagation based actuator-sensor monitoring method. Firstly, the basic knowledge of decision fusion and classifier selection techniques is briefly introduced. Then, a developed decision fusion system is presented. Finally, three fusion algorithms, which consist of majority voting, Bayesian belief, and multiagent method, are adopted for comparison in a real-world monitoring experiment for the large aviation aluminum plate. Based on the results shown in the experiment, a big potential in real-time application is presented that the method can accurately and rapidly identify the bolt loosening by analyzing the acquired strain signal using proposed decision fusion system. Dong Liang and Shen-fang Yuan Copyright © 2015 Dong Liang and Shen-fang Yuan. All rights reserved. Damage Identification of Bridge Based on Chebyshev Polynomial Fitting and Fuzzy Logic without Considering Baseline Model Parameters Thu, 08 Jan 2015 11:52:18 +0000 http://www.hindawi.com/journals/sv/2015/187956/ The paper presents an effective approach for damage identification of bridge based on Chebyshev polynomial fitting and fuzzy logic systems without considering baseline model data. The modal curvature of damaged bridge can be obtained through central difference approximation based on displacement modal shape. Depending on the modal curvature of damaged structure, Chebyshev polynomial fitting is applied to acquire the curvature of undamaged one without considering baseline parameters. Therefore, modal curvature difference can be derived and used for damage localizing. Subsequently, the normalized modal curvature difference is treated as input variable of fuzzy logic systems for damage condition assessment. Numerical simulation on a simply supported bridge was carried out to demonstrate the feasibility of the proposed method. Yu-Bo Jiao, Han-Bing Liu, Yong-Chun Cheng, and Ya-Feng Gong Copyright © 2015 Yu-Bo Jiao et al. All rights reserved. Vibration Characteristics Induced by Cavitation in a Centrifugal Pump with Slope Volute Thu, 08 Jan 2015 08:25:31 +0000 http://www.hindawi.com/journals/sv/2015/294980/ Cavitation is one of the instability sources in centrifugal pump, which would cause some unexpected results. The goal of this paper was to analyze the influence of cavitation process on different frequency bands in a centrifugal pump with slope volute. And special attention was paid to low frequency signals, which were often filtered in the reported researches. Results show that at noncavitation condition, vibration level is closely related to flow structure interior pump. At partial flow rates, especially low flow rates, vibration level increases rapidly with the onset of rotating stall. At cavitation condition, it is proved that cavitation process has a significant impact on low frequency signals. With cavitation number decreasing, vibration level first rises to a local maximum, then it drops to a local minimum, and finally it rises again. At different flow rates, vibration trends in variable frequency bands differ obviously. Critical point inferred from vibration level is much larger than that from 3% head drop, which indicates that cavitation occurs much earlier than that reflected in head curve. Also, it is noted that high frequency signals almost increase simultaneously with cavitation occurring, which can be used to detect cavitation in centrifugal pump. Ning Zhang, Minguan Yang, Bo Gao, and Zhong Li Copyright © 2015 Ning Zhang et al. All rights reserved. Research on Identification Method of Scour Depth for Bridge Based on ERA and SVM Thu, 01 Jan 2015 14:09:02 +0000 http://www.hindawi.com/journals/sv/2015/346820/ A new damage identification method for bridge scour was proposed, in the case that it was difficult to detect bridge scour depth applying testing equipment. Through integrative application of the eigensystem realization algorithm (ERA) and method of support vector machine (SVM), this method was used to identify the scour depths of bridge under conditions of ambient excitation. The following three steps are necessary for the application of this method to identify bridge scour. Firstly, a sample library about scour depth and upper structure vibration response was established using numerical methods and support vector machine method. Secondly, free response signal of bridge were extracted from random vibration signal of bridge upper structure using random decrement technique. Thirdly, based on above two steps, the bridge scour depth was identified using ERA and SVM. In the process of applying the method to identify bridge scour depth, the key is to find the sensitive points for scour depth of substructure using sample library and to gather the vibration response signal of accelerated velocity under conditions of ambient excitation. It was identified that the method has higher recognition accuracy and better robustness through experiments on a real bridge. The method provided a new way for identifying scour depth of bridges. Xiaozhong Zhang, Wenjuan Yao, Yimin Liu, and Bo Chen Copyright © 2015 Xiaozhong Zhang et al. All rights reserved. Traveling Wave Resonance and Simplified Analysis Method for Long-Span Symmetrical Cable-Stayed Bridges under Seismic Traveling Wave Excitation Wed, 31 Dec 2014 16:06:50 +0000 http://www.hindawi.com/journals/sv/2014/602825/ The seismic responses of a long-span cable-stayed bridge under uniform excitation and traveling wave excitation in the longitudinal direction are, respectively, computed. The numerical results show that the bridge’s peak seismic responses vary significantly as the apparent wave velocity decreases. Therefore, the traveling wave effect must be considered in the seismic design of long-span bridges. The bridge’s peak seismic responses do not vary monotonously with the apparent wave velocity due to the traveling wave resonance. A new traveling wave excitation method that can simplify the multisupport excitation process into a two-support excitation process is developed. Zhong-ye Tian and Meng-lin Lou Copyright © 2014 Zhong-ye Tian and Meng-lin Lou. All rights reserved. Multiple-Echo Suppression Modeling and Experimental Verification for Acoustic Transmission along Periodic Drillstring Using Dual Receivers Wed, 31 Dec 2014 15:25:40 +0000 http://www.hindawi.com/journals/sv/2014/295279/ In the oil industry, the accompanied reverberation is a major constraint in the transmission rate and distance because the drillstring is a heterogeneous assembly. Based on the transient impulse responses in uplink and downlink channels, an improved simplified echo suppression model with two acoustic receivers is presented in consideration of position optimization of single acoustic receiver. Then the acoustic receiving characteristics of transmitted signals in a length-limited periodic drillstring channel are obtained in single- and dual-receiver modes. An additive downward white Gaussian noise is also introduced in the channel. Moreover, an experimental rig is established by using a rotatable electromagnetic vibration exciter and two piezoelectric accelerometers, which are spaced one-quarter wavelength apart along a 6.3-meter simulated periodic drillstring. The ASK-, FSK-, and PSK-modulated square-wave pulse sequences at a transmission rate of 200 bit/s are applied to the simulated drillstring at a rotation speed of 0, 80, and 140 r/min, respectively. The experimental results show that the dual-receiver mode can exhibit a significantly improved average error bit ratio, which is approximately 2.5 to 3 times lower than that of the single-receiver mode, especially under the conditions of higher rotation speeds. Li Cheng, Chang Jinfeng, Liu Zhao, and Fan Shangchun Copyright © 2014 Li Cheng et al. All rights reserved. Model Reduction Technique Tailored to the Dynamic Analysis of a Beam Structure under a Moving Load Mon, 29 Dec 2014 09:34:51 +0000 http://www.hindawi.com/journals/sv/2014/406093/ This study presents a technique that uses a model reduction method for the dynamic response analysis of a beam structure to a moving load, which can be modeled either as a moving point force or as a moving body. The nature of the dedicated condensation method tailored to address the moving load case is that the master degrees of freedom are reselected, and the coefficient matrices of the condensed model are recalculated as the load travels from one element to another. Although this process increases computational burden, the overall computational time is still greatly reduced because of the small scale of motion equations. To illustrate and validate the methodology, the technique is initially applied to a simply supported beam subjected to a single-point load moving along the beam. Subsequently, the technique is applied to a practical model for wheel-rail interaction dynamic analysis in railway engineering. Numerical examples show that the condensation model can solve the moving load problem faster than an analytical model or its full finite element model. The proposed model also exhibits high computational accuracy. Yuanchang Chen, Bangji Zhang, and Shengzhao Chen Copyright © 2014 Yuanchang Chen et al. All rights reserved. The Combined Internal and Principal Parametric Resonances on Continuum Stator System of Asynchronous Machine Mon, 22 Dec 2014 00:10:22 +0000 http://www.hindawi.com/journals/sv/2014/835104/ With the increasing requirement of quiet electrical machines in the civil and defense industry, it is very significant and necessary to predict the vibration and noise characteristics of stator and rotor in the early conceptual phase. Therefore, the combined internal and principal parametric resonances of a stator system excited by radial electromagnetic force are presented in this paper. The stator structure is modeled as a continuum double-shell system which is loaded by a varying distributed electromagnetic load. The nonlinear dynamic equations are derived and solved by the method of multiple scales. The influences of mechanical and electromagnetic parameters on resonance characteristics are illustrated by the frequency-response curves. Furthermore, the Runge-Kutta method is adopted to numerically analyze steady-state response for the further understanding of the resonance characteristics with different parameters. Baizhou Li and Qichang Zhang Copyright © 2014 Baizhou Li and Qichang Zhang. All rights reserved. Certain Type Turbofan Engine Whole Vibration Model with Support Looseness Fault and Casing Response Characteristics Wed, 17 Dec 2014 09:09:16 +0000 http://www.hindawi.com/journals/sv/2014/683469/ Support looseness fault is a type of common fault in aeroengine. Serious looseness fault would emerge under larger unbalanced force, which would cause excessive vibration and even lead to rubbing fault, so it is important to analyze and recognize looseness fault effectively. In this paper, based on certain type turbofan engine structural features, a rotor-support-casing whole model for certain type turbofan aeroengine is established. The rotor and casing systems are modeled by means of the finite element beam method; the support systems are modeled by lumped-mass model; the support looseness fault model is also introduced. The coupled system response is obtained by numerical integral method. In this paper, based on the casing acceleration signals, the impact characteristics of symmetrical stiffness and asymmetric stiffness models are analyzed, finding that the looseness fault would lead to the longitudinal asymmetrical characteristics of acceleration time domain wave and the multiple frequency characteristics, which is consistent with the real trial running vibration signals. Asymmetric stiffness looseness model is verified to be fit for aeroengine looseness fault model. H. F. Wang and G. Chen Copyright © 2014 H. F. Wang and G. Chen. All rights reserved. Analysis of Nonlinear Vibration of Hard Coating Thin Plate by Finite Element Iteration Method Mon, 08 Dec 2014 00:10:27 +0000 http://www.hindawi.com/journals/sv/2014/941709/ This paper studies nonlinear vibration mechanism of hard coating thin plate based on macroscopic vibration theory and proposes finite element iteration method (FEIM) to theoretically calculate its nature frequency and vibration response. First of all, strain dependent mechanical property of hard coating is briefly introduced and polynomial method is adopted to characterize the storage and loss modulus of coating material. Then, the principle formulas of inherent and dynamic response characteristics of the hard coating composite plate are derived. And consequently specific analysis procedure is proposed by combining ANSYS APDL and self-designed MATLAB program. Finally, a composite plate coated with MgO + Al2O3 is taken as a study object and both nonlinear vibration test and analysis are conducted on the plate specimen with considering strain dependent mechanical parameters of hard coating. Through comparing the resulting frequency and response results, the practicability and reliability of FEIM have been verified and the corresponding analysis results can provide an important reference for further study on nonlinear vibration mechanism of hard coating composite structure. Hui Li, Liu Ying, and Wei Sun Copyright © 2014 Hui Li et al. All rights reserved. The Pore Collapse “Hot-Spots” Model Coupled with Brittle Damage for Solid Explosives Thu, 04 Dec 2014 13:42:07 +0000 http://www.hindawi.com/journals/sv/2014/972414/ This paper is devoted to the building of a numerical pore collapse model with “hot-spots” formation for the impacted damage explosives. According to damage mechanical evolution of brittle material, the one-dimensional elastic-viscoplastic collapse model was improved to incorporate the impact damage during the dynamic collapse of pores. The damage of explosives was studied using the statistical crack mechanics (SCRAM). The effects of the heat conduction and the chemical reaction were taken into account in the formation of “hot-spots.” To verify the improved model, numerical simulations were carried out for different pressure states and used to model a multiple-impact experiment. The results show that repeated weak impacts can lead to the collapse of pores and the “hot-spots” may occur due to the accumulation of internal defects accompanied by the softening of explosives. L. R. Cheng, R. Chen, H. J. Shi, and F. Y. Lu Copyright © 2014 L. R. Cheng et al. All rights reserved. New Equivalent Linear Impact Model for Simulation of Seismic Isolated Structure Pounding against Moat Wall Mon, 24 Nov 2014 08:09:29 +0000 http://www.hindawi.com/journals/sv/2014/151237/ Base-isolated buildings subjected to extreme earthquakes or near-fault pulse-like earthquakes can exceed their design gap distance and impact against the surrounding moat wall. Based on equating energy dissipation and maximum collision compression deformation of isolated structure with the Hertz-damp model and Kevin-Voigt model in the process of collision, an equivalent linear impact model (ELIM) is proposed to better predict impact response of seismic isolated structure. The formula of the equivalent linear stiffness of ELIM is theoretically derived. The effectiveness of ELIM is verified by comparing the results of numerical analyses with the results of pounding experiments. Four near-fault earthquakes are selected to validate rationality and accuracy of the proposed model using numerical analysis. The results indicate that the proposed linear model can nearly capture impact behavior of isolated structure in simulating the pounding-involved structural response. Yang Liu, Wen-Guang Liu, Xin Wang, Wen-Fu He, and Qiao-Rong Yang Copyright © 2014 Yang Liu et al. All rights reserved. A Study on the Impact Coefficient of Traffic Flows on a Large Cable-Stayed Bridge in a Windy Environment Mon, 17 Nov 2014 12:42:27 +0000 http://www.hindawi.com/journals/sv/2014/124536/ By developing a wind-vehicle-bridge coupling dynamic analysis system, the impact coefficient of traffic flows on a cable-stayed bridge and its probabilistic distribution are studied in the paper. Some important influence factors of the impact coefficient, such as the vehicle-bridge coupling effect, traveling velocity, and traffic density, are analyzed. The influence of the coupling effect between a bridge deck’s buffeting and vehicles’ vibration on the impact coefficient of traffic flows on a cable-stayed bridge is paid due attention to. The results show that vehicle-bridge coupling effect and surface roughness exert important influence on the impact effect of a cable-stayed bridge. Considering that impact coefficient of traffic flows on a bridge bears the characteristics of randomness, the paper, on the basis of a large number of samples, interprets the influence of traveling velocity and traffic density in view of its probabilistic distribution. In view of results derived from the coupling dynamic analysis, it is suggested that the impact coefficient be 25% for all spans of a long cable-stayed bridge like the Sutong Yangtze Bridge. L. Ma, D. J. Zhou, and W. S. Han Copyright © 2014 L. Ma et al. All rights reserved. Subdomain Precise Integration Method for Periodic Structures Sun, 09 Nov 2014 12:34:08 +0000 http://www.hindawi.com/journals/sv/2014/657589/ A subdomain precise integration method is developed for the dynamical responses of periodic structures comprising many identical structural cells. The proposed method is based on the precise integration method, the subdomain scheme, and the repeatability of the periodic structures. In the proposed method, each structural cell is seen as a super element that is solved using the precise integration method, considering the repeatability of the structural cells. The computational efforts and the memory size of the proposed method are reduced, while high computational accuracy is achieved. Therefore, the proposed method is particularly suitable to solve the dynamical responses of periodic structures. Two numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method through comparison with the Newmark and Runge-Kutta methods. F. Wu, Q. Gao, and W. X. Zhong Copyright © 2014 F. Wu et al. All rights reserved. Intelligent Diagnosis Method for Centrifugal Pump System Using Vibration Signal and Support Vector Machine Tue, 04 Nov 2014 00:00:00 +0000 http://www.hindawi.com/journals/sv/2014/407570/ This paper proposed an intelligent diagnosis method for a centrifugal pump system using statistic filter, support vector machine (SVM), possibility theory, and Dempster-Shafer theory (DST) on the basis of the vibration signals, to diagnose frequent faults in the centrifugal pump at an early stage, such as cavitation, impeller unbalance, and shaft misalignment. Firstly, statistic filter is used to extract the feature signals of pump faults from the measured vibration signals across an optimum frequency region, and nondimensional symptom parameters (NSPs) are defined to represent the feature signals for distinguishing fault types. Secondly, the optimal classification hyperplane for distinguishing two states is obtained by SVM and NSPs, and its function is defined as synthetic symptom parameter (SSP) in order to increase the diagnosis’ sensitivity. Finally, the possibility functions of the SSP are used to construct a sequential fuzzy diagnosis for fault detection and fault-type identification by possibility theory and DST. The proposed method has been applied to detect the faults of the centrifugal pump, and the efficiency of the method has been verified using practical examples. Hongtao Xue, Zhongxing Li, Huaqing Wang, and Peng Chen Copyright © 2014 Hongtao Xue et al. All rights reserved. Numerical Analysis of Dynamic Response of Corrugated Core Sandwich Panels Subjected to Near-Field Air Blast Loading Mon, 27 Oct 2014 13:28:47 +0000 http://www.hindawi.com/journals/sv/2014/180674/ Three-dimensional fully coupled simulation is conducted to analyze the dynamic response of sandwich panels comprising equal thicknesses face sheets sandwiching a corrugated core when subjected to localized impulse created by the detonation of cylindrical explosive. A large number of computational cases have been calculated to comprehensively investigate the performance of sandwich panels under near-field air blast loading. Results show that the deformation/failure modes of panels depend strongly on stand-off distance. The beneficial FSI effect can be enhanced by decreasing the thickness of front face sheet. The core configuration has a negligible influence on the peak reflected pressure, but it has an effect on the deflection of a panel. It is found that the benefits of a sandwich panel over an equivalent weight solid plate to withstand near-field air blast loading are more evident at lower stand-off distance. Pan Zhang, Yuansheng Cheng, and Jun Liu Copyright © 2014 Pan Zhang et al. All rights reserved.