Shock and Vibration The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Influences of the Cloud Shape of Fuel-Air Mixtures on the Overpressure Field Wed, 27 Apr 2016 09:59:27 +0000 This paper presents an experiment system in the open field, which comprises a charge structure (approximately 166.2 kg), a high-speed camera subsystem, and a pressure measurement subsystem. Through a series of experiments under the cylindrical clouds with different diameters, heights, and diameter-to-height ratios ( : ), the influences of various cloud shapes on the overpressure field were analyzed and discussed. Based on the experimental results, the overpressure field was divided into two zones: detonation wave zone and shock wave zone. It is found that the overpressure of shock waves at the same distance from the explosion center increased with the diameters, but the variations of heights had little impact on the overpressure. Therefore, the pancake-shaped cloud of fuel-air mixtures is the optimal shape for obtaining the wider overpressure field. Moreover, it is found that the overpressure field gets the maximum under the diameter-to-height ratios of 5.7 in the same distance within the studied range. Chunhua Bai, Ye Wang, Jianping Li, and Mingsheng Chen Copyright © 2016 Chunhua Bai et al. All rights reserved. Phase Space Similarity as a Signature for Rolling Bearing Fault Diagnosis and Remaining Useful Life Estimation Tue, 26 Apr 2016 16:35:10 +0000 Feature extraction from vibration signal is still a challenge in the area of fault diagnosis and remaining useful life (RUL) estimation of rotary machine. In this paper, a novel feature called phase space similarity (PSS) is introduced for health condition monitoring of bearings. Firstly, the acquired signal is transformed to the phase space through the phase space reconstruction (PSR). The similar vibration always exists in the phase space due to the comparable evolution of the dynamics that are characteristic of the system state. Secondly, the normalized cross-correlation (NCC) is employed to calculate the PSS between bearing data with different states. Based on the PSS, a fault pattern recognition algorithm, a bearing fault size prediction algorithm, and a RUL estimation algorithm are introduced to analyze the experimental signal. Results have shown the effectiveness of the PSS as it can better grasp the nature and regularity of the signals. Fang Liu, Bing He, Yongbin Liu, Siliang Lu, Yilei Zhao, and Jiwen Zhao Copyright © 2016 Fang Liu et al. All rights reserved. An Effective Fault Feature Extraction Method for Gas Turbine Generator System Diagnosis Tue, 26 Apr 2016 13:47:13 +0000 Fault diagnosis is very important to maintain the operation of a gas turbine generator system (GTGS) in power plants, where any abnormal situations will interrupt the electricity supply. The fault diagnosis of the GTGS faces the main challenge that the acquired data, vibration or sound signals, contain a great deal of redundant information which extends the fault identification time and degrades the diagnostic accuracy. To improve the diagnostic performance in the GTGS, an effective fault feature extraction framework is proposed to solve the problem of the signal disorder and redundant information in the acquired signal. The proposed framework combines feature extraction with a general machine learning method, support vector machine (SVM), to implement an intelligent fault diagnosis. The feature extraction method adopts wavelet packet transform and time-domain statistical features to extract the features of faults from the vibration signal. To further reduce the redundant information in extracted features, kernel principal component analysis is applied in this study. Experimental results indicate that the proposed feature extracted technique is an effective method to extract the useful features of faults, resulting in improvement of the performance of fault diagnosis for the GTGS. Jian-Hua Zhong, JieJunYi Liang, Zhi-Xin Yang, Pak Kin Wong, and Xian-Bo Wang Copyright © 2016 Jian-Hua Zhong et al. All rights reserved. Online Identification and Verification of the Elastic Coupling Torsional Stiffness Tue, 26 Apr 2016 12:52:16 +0000 To analyze the torsional vibration of a diesel engine shaft, the torsional stiffness of the flexible coupling is a key kinetic parameter. Since the material properties of the elastic element of the coupling might change after a long-time operation due to the severe working environment or improper use and the variation of such properties will change dynamic feature of the coupling, it will cause a relative large calculation error of torsional vibration to the shaft system. Moreover, the torsional stiffness of the elastic coupling is difficult to be determined, and it is inappropriate to measure this parameter by disassembling the power unit while it is under normal operation. To solve these problems, this paper comes up with a method which combines the torsional vibration test with the calculation of the diesel shafting and uses the inherent characteristics of shaft torsional vibration to identify the dynamic stiffness of the elastic coupling without disassembling the unit. Analysis results show that it is reasonable and feasible to identify the elastic coupling dynamic torsional stiffness with this method and the identified stiffness is accurate. Besides, this method provides a convenient and practical approach to examine the dynamic behavior of the long running elastic coupling. Wanyou Li, Zhuoye Chai, Mengqi Wang, Xinhuan Hu, and Yibin Guo Copyright © 2016 Wanyou Li et al. All rights reserved. Deformation and Failure Mechanism of Roadway Sensitive to Stress Disturbance and Its Zonal Support Technology Tue, 26 Apr 2016 09:01:01 +0000 The 6163 haulage roadway in the Qidong coal mine passes through a fault zone, which causes severe deformation in the surrounding rock, requiring repeated roadway repairs. Based on geological features in the fault area, we analyze the factors affecting roadway deformation and failure and propose the concept of roadway sensitive to stress disturbance (RSSD). We investigate the deformation and failure mechanism of the surrounding rocks of RSSD using field monitoring, theoretical analysis, and numerical simulation. The deformation of the surrounding rocks involves dilatation of shallow rocks and separation of deep rocks. Horizontal and longitudinal fissures evolve to bed separation and fracture zones; alternatively, fissures can evolve into fracture zones with new fissures extending to deeper rock. The fault affects the stress field of the surrounding rock to ~27 m radius. Its maximum impact is on the vertical stress of the rib rock mass and its minimum impact is on the vertical stress of the floor rock mass. Based on our results, we propose a zonal support system for a roadway passing through a fault. Engineering practice shows that the deformation of the surrounding rocks of the roadway can be effectively controlled to ensure normal and safe production in the mine. Qiangling Yao, Xuehua Li, Fan Pan, Teng Wang, and Guang Wang Copyright © 2016 Qiangling Yao et al. All rights reserved. A Study of Rockburst Hazard Evaluation Method in Coal Mine Sun, 24 Apr 2016 12:48:13 +0000 With the increasing of coal mining depth, the mining conditions are deteriorating, and dynamic hazard is becoming more likely to happen. This paper analyzes the relations and differences between rockburst in the coal mine and rockburst in the metal mine. It divides coal mine rockburst into two types including static loading type during roadway excavation process and dynamic loading type during mining face advancing. It proposes the correlation between the formation process of rockburst and the evolution of overlying strata spatial structure of the stope, criterion of rockburst occurrence, new classification, and predictive evaluation method for rockburst hazard that rockburst damage evaluation (RDE) = released energy capacity (REC)/absorbed energy capacity (AEC). Based on the relationship between RDE value and its corresponding level of rockburst hazard, the rockburst hazard can be divided into five types and evaluation index of each type can be achieved. Then the ongoing rockburst damage level can be classified in one of the five types, and the relative parameters, such as hazard extent, controlling measures also can be achieved. This new quantitative method could not only assess the impacting direction of rockburst occurrence, but also verify the effect of preventive measures for rockburst. Zhijie Wen, Xiao Wang, Yunliang Tan, Hualei Zhang, Wanpeng Huang, and Qinghai Li Copyright © 2016 Zhijie Wen et al. All rights reserved. Study on the Rollover Characteristic of In-Wheel-Motor-Driven Electric Vehicles Considering Road and Electromagnetic Excitation Thu, 21 Apr 2016 14:28:36 +0000 For in-wheel-motor-driven electric vehicles, the motor is installed in the wheel directly. Tyre runout and uneven load can cause magnet gap deformation in the motor, which will produce electromagnetic forces that further influence the vehicle rollover characteristics. To study the rollover characteristics, a verified 16-degree-of-freedom rollover dynamic model is introduced. Next, the vehicle rollover characteristics both with and without electromagnetic force are analyzed under conditions of the Fixed Timing Fishhook steering and grade B road excitation. The results show that the electromagnetic force has a certain effect on the load transfer and can reduce the antirollover performance of the vehicle. Therefore, the effect of the electromagnetic force on the rollover characteristic should be considered in the vehicle design. To this end, extensive analysis was conducted on the effect of the road level, vehicle speed, and the road adhesion coefficient on the vehicle rollover stability. The results indicate that vehicle rollover stability worsens when the above-mentioned factors increase, the most influential factor being the road adhesion coefficient followed by vehicle speed and road level. This paper can offer certain theory basis for the design of the in-wheel-motor-driven electric vehicles. Di Tan, Haitao Wang, and Qiang Wang Copyright © 2016 Di Tan et al. All rights reserved. Feature Extraction and Selection Scheme for Intelligent Engine Fault Diagnosis Based on 2DNMF, Mutual Information, and NSGA-II Thu, 21 Apr 2016 07:48:29 +0000 A novel feature extraction and selection scheme is presented for intelligent engine fault diagnosis by utilizing two-dimensional nonnegative matrix factorization (2DNMF), mutual information, and nondominated sorting genetic algorithms II (NSGA-II). Experiments are conducted on an engine test rig, in which eight different engine operating conditions including one normal condition and seven fault conditions are simulated, to evaluate the presented feature extraction and selection scheme. In the phase of feature extraction, the transform technique is firstly utilized to convert the engine vibration signals to time-frequency domain, which can provide richer information on engine operating conditions. Then a novel feature extraction technique, named two-dimensional nonnegative matrix factorization, is employed for characterizing the time-frequency representations. In the feature selection phase, a hybrid filter and wrapper scheme based on mutual information and NSGA-II is utilized to acquire a compact feature subset for engine fault diagnosis. Experimental results by adopted three different classifiers have demonstrated that the proposed feature extraction and selection scheme can achieve a very satisfying classification performance with fewer features for engine fault diagnosis. Peng-yuan Liu, Bing Li, Cui-e Han, and Feng Wang Copyright © 2016 Peng-yuan Liu et al. All rights reserved. Waveform-Based Condition Assessments in Civil Engineering Tue, 19 Apr 2016 13:58:24 +0000 Sang-Youl Lee, Guillermo Rus, and Abdollah Shafieezadeh Copyright © 2016 Sang-Youl Lee et al. All rights reserved. Fault Diagnosis and Prognosis of Critical Components Tue, 19 Apr 2016 06:47:59 +0000 Dong Wang, Chuan Li, Achmad Widodo, Pavan Kumar Kankar, and Wahyu Caesarendra Copyright © 2016 Dong Wang et al. All rights reserved. High Response Performance of a Tuned-Mass Damper for Vibration Suppression of Offshore Platform under Earthquake Loads Sun, 17 Apr 2016 11:06:43 +0000 Currently, tuned-mass dampers (TMDs) are widely applied to maintain the stability of offshore platforms in hostile environments; however, the stability system of offshore platforms faces considerable challenges under critical earthquake loads of the initial period. Therefore, this study concentrated on the high response performance of a simple passive TMD system, and numerical and experimental investigations were performed using a 1 : 200-scale prototype. The obtained results indicated that the displacement, acceleration, and their power spectral density all decreased significantly for the offshore platform with the TMD system. By further analyses of its high response characteristics, it was validated that the TMD reactions can commence within the first 3 s of earthquake excitation, while the fundamental natural frequency was consistently tuned for the TMD system dependent on the dynamic magnification factor. The evaluation indices also confirmed that this method is effective in reducing the overall vibration level and the maximum peak values of the offshore platform exposed to earthquake excitations, mainly because of its high response characteristics. Qiong Wu, Xilu Zhao, Rencheng Zheng, and Keisuke Minagawa Copyright © 2016 Qiong Wu et al. All rights reserved. A Hybrid Prognostic Approach for Remaining Useful Life Prediction of Lithium-Ion Batteries Mon, 11 Apr 2016 11:11:46 +0000 Lithium-ion battery is a core component of many systems such as satellite, spacecraft, and electric vehicles and its failure can lead to reduced capability, downtime, and even catastrophic breakdowns. Remaining useful life (RUL) prediction of lithium-ion batteries before the future failure event is extremely crucial for proactive maintenance/safety actions. This study proposes a hybrid prognostic approach that can predict the RUL of degraded lithium-ion batteries using physical laws and data-driven modeling simultaneously. In this hybrid prognostic approach, the relevant vectors obtained with the selective kernel ensemble-based relevance vector machine (RVM) learning algorithm are fitted to the physical degradation model, which is then extrapolated to failure threshold for estimating the RUL of the lithium-ion battery of interest. The experimental results indicated that the proposed hybrid prognostic approach can accurately predict the RUL of degraded lithium-ion batteries. Empirical comparisons show that the proposed hybrid prognostic approach using the selective kernel ensemble-based RVM learning algorithm performs better than the hybrid prognostic approaches using the popular learning algorithms of feedforward artificial neural networks (ANNs) like the conventional backpropagation (BP) algorithm and support vector machines (SVMs). In addition, an investigation is also conducted to identify the effects of RVM learning algorithm on the proposed hybrid prognostic approach. Wen-An Yang, Maohua Xiao, Wei Zhou, Yu Guo, and Wenhe Liao Copyright © 2016 Wen-An Yang et al. All rights reserved. Research on the Rockburst Tendency and AE Characteristics of Inhomogeneous Coal-Rock Combination Bodies Sun, 10 Apr 2016 13:40:04 +0000 In order to research the influence of homogeneity on the rockburst tendency and on AE characteristics of coal-rock combination body, uniaxial compressive tests of inhomogeneous coal-rock combination bodies obeyed by the Weibull distribution were simulated using particle flow code (). Macromechanical properties, energy evolution law, and AE characteristics were analyzed. The results show that (1) the elastic modulus homogeneity has an exponential relation with macroscopic modulus , and the bonding strength homogeneity has an exponential relation with uniaxial compressive strength ; (2) the rockburst tendency of the coal-rock combination body will increase with the increase of or , and is the leading factor influencing this tendency; and (3) both the change law of AE hits and lasting time in different periods of AE characteristics are influenced by , but just influences the lasting time. The more inhomogeneous the coal-rock combination body is, the shorter the lasting time in booming period of AE characteristics will be. This phenomenon can be used to predict the rockburst tendency of the coal-rock combination body. Yun-liang Tan, Wei-yao Guo, Qing-heng Gu, Tong-bin Zhao, Feng-hai Yu, Shan-chao Hu, and Yan-chun Yin Copyright © 2016 Yun-liang Tan et al. All rights reserved. Dissipation of Impact Stress Waves within the Artificial Blasting Damage Zone in the Surrounding Rocks of Deep Roadway Sun, 10 Apr 2016 13:26:15 +0000 Artificial explosions are commonly used to prevent rockburst in deep roadways. However, the dissipation of the impact stress wave within the artificial blasting damage zone (ABDZ) of the rocks surrounding a deep roadway has not yet been clarified. The surrounding rocks were divided into the elastic zone, blasting damage zone, plastic zone, and anchorage zone in this research. Meanwhile, the ABDZ was divided into the pulverizing area, fractured area, and cracked area from the inside out. Besides, the model of the normal incidence of the impact stress waves in the ABDZ was established; the attenuation coefficient of the amplitude of the impact stress waves was obtained after it passed through the intact rock mass, and ABDZ, to the anchorage zone. In addition, a numerical simulation was used to study the dynamic response of the vertical stress and impact-induced vibration energy in the surrounding rocks. By doing so, the dissipation of the impact stress waves within the ABDZ of the surrounding rocks was revealed. As demonstrated in the field application, the establishment of the ABDZ in the surrounding rocks reduced the effect of the impact-induced vibration energy on the anchorage support system of the roadway. Jianguo Ning, Jun Wang, Yunliang Tan, and Xinshuai Shi Copyright © 2016 Jianguo Ning et al. All rights reserved. The Effect of Rail Fastening System Modifications on Tram Traffic Noise and Vibration Sun, 10 Apr 2016 11:21:22 +0000 Tram system is a backbone of public transportation in the City of Zagreb. In the last decade, its fleet has been renewed by 142 new low-floor trams. Shortly after their introduction, it was observed that they have a negative impact on the exploitation behavior of tram infrastructure, primarily on the durability of rail fastening systems. Because of that, it was decided to modify existing rail fastening systems to the new track exploitation conditions. When the (re)construction of tram infrastructure is carried out by applying new systems and technologies, it is necessary to take into account their impact on the future propagation of noise and vibration in the environment. This paper gives a short overview of the characteristics of the two newly developed rail fastening systems for Zagreb tram tracks, their application in construction of experimental track section, and performance and comparison of noise and vibration measurements results. Measured data on track vibrations and noise occurring during passage of the tram vehicles is analyzed in terms of track decay rates and equivalent noise levels of passing referent vehicle. Vibroacoustic performance of new fastening systems is evaluated and compared to referent fastening system, in order to investigate their ability to absorb vibration energy induced by tram operation and to reduce noise emission. Stjepan Lakušić, Ivo Haladin, and Maja Ahac Copyright © 2016 Stjepan Lakušić et al. All rights reserved. Seismic Behavior of Posttensioned Concrete Bridge Piers with External Viscoelastic Dampers Thu, 07 Apr 2016 13:34:42 +0000 This paper investigates the seismic performance of posttensioned concrete piers with external viscoelastic dampers to improve the energy dissipation capacity of this type of structure. An installation scheme for viscoelastic dampers on bridge piers is proposed, and the mechanical models of the damper are analyzed according to the installation scheme. By attaching the viscoelastic dampers to the posttensioned bridge piers, the analytical model of the hybrid system is established using the OpenSees finite element analysis package. Cyclic behavior and time history analyses are conducted on a posttensioned bridge with and without viscoelastic dampers using the established finite element model. The analysis results indicate that the viscoelastic dampers can effectively improve the seismic performance of the bridge structures with posttensioned piers. Anxin Guo and Huixing Gao Copyright © 2016 Anxin Guo and Huixing Gao. All rights reserved. Railway Wheel Flat Detection Based on Improved Empirical Mode Decomposition Wed, 06 Apr 2016 12:32:05 +0000 This study explores the capacity of the improved empirical mode decomposition (EMD) in railway wheel flat detection. Aiming at the mode mixing problem of EMD, an EMD energy conservation theory and an intrinsic mode function (IMF) superposition theory are presented and derived, respectively. Based on the above two theories, an improved EMD method is further proposed. The advantage of the improved EMD is evaluated by a simulated vibration signal. Then this method is applied to study the axle box vibration response caused by wheel flats, considering the influence of both track irregularity and vehicle running speed on diagnosis results. Finally, the effectiveness of the proposed method is verified by a test rig experiment. Research results demonstrate that the improved EMD can inhibit mode mixing phenomenon and extract the wheel fault characteristic effectively. Yifan Li, Jianxin Liu, and Yan Wang Copyright © 2016 Yifan Li et al. All rights reserved. Applicability of a Simplified SDOF Method in Longitudinal Deck-Pier Poundings of Simply Supported Girder Bridges Wed, 06 Apr 2016 12:27:59 +0000 The pounding issue between decks in the earthquake has been a great concern of many researchers, but the research on the deck-pier pounding issue was inadequate. In this paper, a simplified SDOF method was proposed to study the issue for simply supported girder bridges. Theoretical analysis, shaking table test, and finite element analysis were conducted to study the applicability of the simplified SDOF method in longitudinal deck-pier poundings. A whole structural model and a SDOF model for the longitudinal pounding issue were also established to study influences of the pier stiffness and the pier mass on longitudinal pounding responses. It is shown that the simplified SDOF method can estimate the pounding force and deck displacement fairly accurately for almost all cases. The pier mass has little effect on pounding responses except for bridges with very rigid piers, but the pier stiffness has a great influence. The larger the pier stiffness is, the higher the peak pounding force is. Tianbo Peng and Ning Guo Copyright © 2016 Tianbo Peng and Ning Guo. All rights reserved. Free Transverse Vibration Analysis of Axially Functionally Graded Tapered Euler-Bernoulli Beams through Spline Finite Point Method Tue, 05 Apr 2016 06:14:52 +0000 A new model for the free transverse vibration of axially functionally graded (FG) tapered Euler-Bernoulli beams is developed through the spline finite point method (SFPM) by investigating the effects of the variation of cross-sectional and material properties along the longitudinal directions. In the proposed method, the beam is discretized with a set of uniformly scattered spline nodes along the beam axis instead of meshes, and the displacement field is approximated by the particularly constructed cubic B-spline interpolation functions with good adaptability for various boundary conditions. Unlike traditional discretization and modeling methods, the global structural stiffness and mass matrices for beams of the proposed model are directly generated after spline discretization without needing element meshes, generation, and assembling. The proposed method shows the distinguished features of high modeling efficiency, low computational cost, and convenience for boundary condition treatment. The performance of the proposed method is verified through numerical examples available in the published literature. All results demonstrate that the proposed method can analyze the free vibration of axially FG tapered Euler-Bernoulli beams with various boundary conditions. Moreover, high accuracy and efficiency can be achieved. Peng Liu, Kun Lin, Hongjun Liu, and Rong Qin Copyright © 2016 Peng Liu et al. All rights reserved. Fatigue Strain and Damage Analysis of Concrete in Reinforced Concrete Beams under Constant Amplitude Fatigue Loading Mon, 04 Apr 2016 16:43:45 +0000 Concrete fatigue strain evolution plays a very important role in the evaluation of the material properties of concrete. To study fatigue strain and fatigue damage of concrete in reinforced concrete beams under constant amplitude bending fatigue loading, constant amplitude bending fatigue experiments with reinforced concrete beams with rectangular sections were first carried out in the laboratory. Then, by analyzing the shortcomings and limitations of existing fatigue strain evolution equations, the level-S nonlinear evolution model of fatigue strain was constructed, and the physical meaning of the parameters was discussed. Finally, the evolution of fatigue strain and fatigue damage of concrete in the compression zone of the experimental beam was analyzed based on the level-S nonlinear evolution model. The results show that, initially, fatigue strain grows rapidly. In the middle stages, fatigue strain is nearly a linear change. Because the experimental data for the third stage are relatively scarce, the evolution of the strain therefore degenerated into two phases. The model has strong adaptability and high accuracy and can reflect the evolution of fatigue strain. The fatigue damage evolution expression based on fatigue strain shows that fatigue strain and fatigue damage have similar variations, and, with the same load cycles, the greater the load level, the larger the damage, in line with the general rules of damage. Fangping Liu and Jianting Zhou Copyright © 2016 Fangping Liu and Jianting Zhou. All rights reserved. The Fault Feature Extraction of Rolling Bearing Based on EMD and Difference Spectrum of Singular Value Thu, 31 Mar 2016 17:55:57 +0000 Nowadays, the fault diagnosis of rolling bearing in aeroengines is based on the vibration signal measured on casing, instead of bearing block. However, the vibration signal of the bearing is often covered by a series of complex components caused by other structures (rotor, gears). Therefore, when bearings cause failure, it is still not certain that the fault feature can be extracted from the vibration signal on casing. In order to solve this problem, a novel fault feature extraction method for rolling bearing based on empirical mode decomposition (EMD) and the difference spectrum of singular value is proposed in this paper. Firstly, the vibration signal is decomposed by EMD. Next, the difference spectrum of singular value method is applied. The study finds that each peak on the difference spectrum corresponds to each component in the original signal. According to the peaks on the difference spectrum, the component signal of the bearing fault can be reconstructed. To validate the proposed method, the bearing fault data collected on the casing are analyzed. The results indicate that the proposed rolling bearing diagnosis method can accurately extract the fault feature that is submerged in other component signals and noise. Te Han, Dongxiang Jiang, and Nanfei Wang Copyright © 2016 Te Han et al. All rights reserved. An Influence of Gas Explosions on Dynamic Responses of a Single Degree of Freedom Model Wed, 30 Mar 2016 14:25:28 +0000 Explosion risk analysis (ERA) is widely used to derive the dimensioning of accidental loads for design purposes. Computational fluid dynamics (CFD) simulations contribute a key part of an ERA and predict possible blast consequences in a hazardous area. Explosion pressures can vary based on the model geometry, the explosion intensity, and explosion scenarios. Dynamic responses of structures under these explosion loads are dependent on a blast wave profile with respect to the magnitude of pressure, duration, and impulse in both positive and negative phases. Understanding the relationship between explosion load profiles and dynamic responses of the target area is important to mitigate the risk of explosion and perform structural design optimization. In the present study, the results of more than 3,000 CFD simulations were considered, and 1.6 million output files were analyzed using a visual basic for applications (VBA) tool developed to characterize representative loading shapes. Dynamic response of a structure was investigated in both time and frequency domains using the Fast Fourier Transform (FFT) algorithm. In addition, the effects of the residual wave and loading velocity were studied in this paper. Ki-Yeob Kang, Kwang-Ho Choi, Jae Woong Choi, Yong Hee Ryu, and Jae-Myung Lee Copyright © 2016 Ki-Yeob Kang et al. All rights reserved. Crash-Induced Vibration and Safety Assessment of Breakaway-Type Post Structures Made of High Anticorrosion Steels Wed, 30 Mar 2016 11:58:18 +0000 This study deals with car crash effects and passenger safety assessment of post structures with breakaway types using high performance steel materials. To disperse the impact force when a car crashes into a post, the post could be designed with a breakaway feature. In this study, we used a new high anticorrosion steel for the development of advanced breakaways. Based on the improved Cowper-Symonds model, specific physical properties to the high anticorrosion steel were determined. In particular, the complex mechanism of breakaways was studied using various parameters. The parametric studies are focused on the various effects of car crash on the structural performance and passenger safety of breakaway-type posts. The combined effects of using different steel materials on the dynamic behavers are also investigated. Sang-Youl Lee Copyright © 2016 Sang-Youl Lee. All rights reserved. Vibration Suppression for Improving the Estimation of Kinematic Parameters on Industrial Robots Wed, 30 Mar 2016 08:57:20 +0000 Vibration is a phenomenon that is present on every industrial system such as CNC machines and industrial robots. Moreover, sensors used to estimate angular position of a joint in an industrial robot are severely affected by vibrations and lead to wrong estimations. This paper proposes a methodology for improving the estimation of kinematic parameters on industrial robots through a proper suppression of the vibration components present on signals acquired from two primary sensors: accelerometer and gyroscope. A Kalman filter is responsible for the filtering of spurious vibration. Additionally, a sensor fusion technique is used to merge information from both sensors and improve the results obtained using each sensor separately. The methodology is implemented in a proprietary hardware signal processor and tested in an ABB IRB 140 industrial robot, first by analyzing the motion profile of only one joint and then by estimating the path tracking of two welding tasks: one rectangular and another one circular. Results from this work prove that the sensor fusion technique accompanied by proper suppression of vibrations delivers better estimation than other proposed techniques. David Alejandro Elvira-Ortiz, Rene de Jesus Romero-Troncoso, Arturo Yosimar Jaen-Cuellar, Luis Morales-Velazquez, and Roque Alfredo Osornio-Rios Copyright © 2016 David Alejandro Elvira-Ortiz et al. All rights reserved. A Fault Feature Extraction Method for Rolling Bearing Based on Pulse Adaptive Time-Frequency Transform Wed, 30 Mar 2016 06:29:18 +0000 Shock pulse method is a widely used technique for condition monitoring of rolling bearing. However, it may cause erroneous diagnosis in the presence of strong background noise or other shock sources. Aiming at overcoming the shortcoming, a pulse adaptive time-frequency transform method is proposed to extract the fault features of the damaged rolling bearing. The method arranges the rolling bearing shock pulses extracted by shock pulse method in the order of time and takes the reciprocal of the time interval between the pulse at any moment and the other pulse as all instantaneous frequency components in the moment. And then it visually displays the changing rule of each instantaneous frequency after plane transformation of the instantaneous frequency components, realizes the time-frequency transform of shock pulse sequence through time-frequency domain amplitude relevancy processing, and highlights the fault feature frequencies by effective instantaneous frequency extraction, so as to extract the fault features of the damaged rolling bearing. The results of simulation and application show that the proposed method can suppress the noises well, highlight the fault feature frequencies, and avoid erroneous diagnosis, so it is an effective fault feature extraction method for the rolling bearing with high time-frequency resolution. Jinbao Yao, Baoping Tang, and Jie Zhao Copyright © 2016 Jinbao Yao et al. All rights reserved. Mathematical Modeling and Analysis of Drill String Longitudinal Vibration with Lateral Inertia Effect Mon, 28 Mar 2016 09:05:36 +0000 Comparative analysis whether considering the lateral inertia or not, aiming at the longitudinal vibration of the drill string in drilling progress, is proposed. In the light of the actual condition, the mechanical model of the drill string about vibration is established on the basis of the theoretical analysis. Longitudinal vibration equation of the drill string is derived from the Rayleigh-Love model and one-dimensional viscoelastic model. According to the Laplace transform method and the relationships among parameters of the model, the solutions to complex impedance at the bottom of the drill string are obtained, and then the comparison results are analyzed, which is the lateral inertia effect on longitudinal vibration characteristics. The researches show that the smaller the length of the drill string, the greater the cross-sectional area of the drill string, the greater the damping coefficient of bottom hole on the bottom of the drill string, and the more evident the effect on the dynamic stiffness of the drill string with lateral inertia effect. The Poisson ratio of the drill string only has some effects on it taking account of the lateral inertia effect, and the influence is relatively small compared with the former three conditions. Jialin Tian, Chunming Wu, Lin Yang, Zhi Yang, Gang Liu, and Changfu Yuan Copyright © 2016 Jialin Tian et al. All rights reserved. Improved Element Erosion Function for Concrete-Like Materials with the SPH Method Sun, 27 Mar 2016 06:55:44 +0000 The subject of the paper is a description of a simple test from the field of terminal ballistics and the handling of issues arising during its simulation using the numerical techniques of the finite element method. With regard to the possible excessive reshaping of the finite element mesh there is a danger that problems will arise such as the locking of elements or the appearance of negative volumes. It is often necessary to introduce numerical extensions so that the simulations can be carried out at all. When examining local damage to structures, such as the penetration of the outer shell or its perforation, it is almost essential to introduce the numerical erosion of elements into the simulations. However, when using numerical erosion, the dissipation of matter and energy from the computational model occurs in the mathematical background to the calculation. It is a phenomenon which can reveal itself in the final result when a discrepancy appears between the simulations and the experiments. This issue can be solved by transforming the eroded elements into smoothed particle hydrodynamics particles. These newly created particles can then assume the characteristics of the original elements and preserve the matter and energy of the numerical model. Jiří Kala and Martin Hušek Copyright © 2016 Jiří Kala and Martin Hušek. All rights reserved. Free Vibration and Hardening Behavior of Truss Core Sandwich Beam Thu, 24 Mar 2016 15:51:09 +0000 The dynamic characteristics of simply supported pyramidal truss core sandwich beam are investigated. The nonlinear governing equation of motion for the beam is obtained by using a Zig-Zag theory. The averaged equations of the beam with primary, subharmonic, and superharmonic resonances are derived by using the method of multiple scales and then the corresponding frequency response equations are obtained. The influences of strut radius and core height on the linear natural frequencies and hardening behaviors of the beam are studied. It is illustrated that the first-order natural frequency decreases continuously and the second-order and third-order natural frequencies initially increase and then decrease with the increase of strut radius, and the first three natural frequencies all increase with the rise of the core height. Furthermore, the results indicate that the hardening behaviors of the beam become weaker with the increase of the rise of strut radius and core height. The mechanisms of variations in hardening behavior of the sandwich beam with the three types of resonances are detailed and discussed. J. E. Chen, W. Zhang, M. Sun, and M. H. Yao Copyright © 2016 J. E. Chen et al. All rights reserved. Damage Detection of Structures for Ambient Loading Based on Cross Correlation Function Amplitude and SVM Wed, 23 Mar 2016 09:51:02 +0000 An effective method for the damage detection of skeletal structures which combines the cross correlation function amplitude (CCFA) with the support vector machine (SVM) is presented in this paper. The proposed method consists of two stages. Firstly, the data features are extracted from the CCFA, which, calculated from dynamic responses and as a representation of the modal shapes of the structure, changes when damage occurs on the structure. The data features are then input into the SVM with the one-against-one (OAO) algorithm to classify the damage status of the structure. The simulation data of IASC-ASCE benchmark model and a vibration experiment of truss structure are adopted to verify the feasibility of proposed method. The results show that the proposed method is suitable for the damage identification of skeletal structures with the limited sensors subjected to ambient excitation. As the CCFA based data features are sensitive to damage, the proposed method demonstrates its reliability in the diagnosis of structures with damage, especially for those with minor damage. In addition, the proposed method shows better noise robustness and is more suitable for noisy environments. Lin-sheng Huo, Xu Li, Yeong-Bin Yang, and Hong-Nan Li Copyright © 2016 Lin-sheng Huo et al. All rights reserved. Parameters Identification of Moving Load Using ANN and Dynamic Strain Tue, 22 Mar 2016 06:35:18 +0000 Moving load identification is an important part of bridge structure health monitoring; accurate and reliable load data can be used to check the load of bridge design, and the load spectrum can provide a more practical basis for structural fatigue analysis. The method of the BP neural network is used in bridge moving loads identification. The numerical examples of identification of the axle loads of a two-axle vehicle moving on a simply supported bridge under various speeds and weights are carried out. The sensitivity of the bridge deflection and strain to moving loads is analyzed, and the influences of different activation function combinations and algorithm on network are discussed. The identification results of different load conditions are analyzed and the effect of noise is considered. Finally the rationality of the method is verified by experiments. It is shown that the indirect estimation of vehicle weight by BP neural network from dynamic responses is feasible. Hui Yang, Weiming Yan, and Haoxiang He Copyright © 2016 Hui Yang et al. All rights reserved.