bluuebunny/crossref_metadata_2025 huggingface dataset:
A Unified method for vibration analysis of moderately thick annular, circular plates and their sector counterparts subjected to arbitrary boundary conditions
Authors: Ahad Fazl e , Shi Dongyan , Rehman Anees Ur , Waqas Hafiz M.
Published: January 2017

The vibrations of circular, annular and sector plates are different boundary value problems due to different edge conditions and thus have been treated separately using different solution algorithms and procedures. In this paper, a unified method is proposed for vibration analysis of moderately thick annular, circular plates and their sector counterparts with arbitrary boundary conditions. The unification of these plates is physically achieved by applying the coupling spring’s technique at the radial edges to ensure appropriate continuity conditions. Irrespective of the shape of the plate and the type of boundary conditions, each of the displacement function is expressed as a new form of trigonometric expansion with high convergence rate. Unlike most of the previous studies the current method can be universally applied to a wide range of vibration problems involving different shapes, boundary conditions, varying materials and geometric properties without modifying the solution algorithms and procedure. Furthermore, the current method can easily be applied to sector plates with an arbitrary inclusion angle of 2π. The accuracy, reliability and versatility of the proposed method are fully demonstrated with several numerical examples for different shapes of plates and under different boundary conditions.
Study on a novel fault diagnosis method based on information fusion method
Authors: Zhao Huimin , Deng Wu , Yang Xinhua , Li Xiumei , Li Zhengguang
Published: January 2017

For the low accuracy and calculation speed of traditional fault diagnosis methods, the chaos optimization algorithm (COA), quantum particle swarm optimization (QPSO) algorithm and support vector machine (SVM) are introduced into the fault diagnosis to propose a novel fault diagnosis (CQPSMFD) method in this paper. In the proposed CQPSMFD method, the COA is used to initialize the parameters of the QPSO algorithm in order to obtain the CQPSO algorithm with the better convergence speed. Then the CQPSO algorithm is used to optimize the parameters of the SVM model to construct a high-precision SVM model (CQPSM) with the higher accuracy and stronger generalization ability. Next, the CQPSMFD method based on CQPSM method is proposed for motor. Finally, the experiment data from Case Western bearing dataset and actual motor are selected to verify the CQPSMFD method. The results show that the CQPSO algorithm can obtain the optimal parameter combination and the CQPSMFD method can effectively improve the fault diagnosis accuracy and speed.
An equivalent linear model for shear pin fractures and its experimental verification
Authors: Peng Tianbo , Guo Ning
Published: January 2017

For bridges in seismically active areas, lower horizontal bearing stiffnesses are usually designed to reduce structural seismic responses and protect the piers and foundations against earthquake damage. But lower horizontal bearing stiffnesses are not preferred under normal service conditions. In the seismic designs of Chinese bridges, shear pins are extensively integrated into bearings to resist horizontal force and restrict the relative longitudinal displacement between the superstructure and the substructure under normal service conditions. Shear pins are designed to be sheared off in a certain earthquake to activate the seismic isolation mechanism. For lack of a proper constitutive model for shear pin fractures, effects of shear pin fractures have not been considered in current bridge seismic isolation designs yet. In order to establish a constitutive model of seismic isolation bearings considering shear pin fracture effects, shear fracture tests of shear pins were conducted and an equivalent linear model was established. Ultimate deformation and equivalent stiffness of the equivalent linear model are approximately proportional to the diameter of the shear pin, and load capacity is approximately proportional to the square of the diameter of the shear pin. A series of shaking table tests were conducted, and then test results were compared with numerical results calculated with the equivalent linear model. It was found the equivalent linear model was accurate enough and suggested to simulate the effects of shear pin fractures in bridge seismic designs.
Design on the fairwater shape and its influence on the radiation noise of submarines
Authors: Huo Lin , Fei Si-miao
Published: January 2017

Firstly, a numerical computation model of submarine radiation noise was established to obtain the radiation noise of the submarine, which was compared with the experimental results, thus verifying the validity of the model. As indicated by the computational result, the submarine fairwater played a significant impact on radiation noise at the front section, whose structure was therefore necessary to be studied. In the paper, there were several different type submarine fairwaters. Large eddy simulation (LES) and boundary element method (BEM) were applied to conduct the numerical computation for the vortex flow field and acoustic characteristics of the original fairwater, the fairwater with fillet and the streamline fairwater. Furthermore, the impact and suppression effect of the fairwater’s type on wall pressure fluctuations and flow-induced noise were analyzed. As shown from the research, the vertical fairwater with fillet or the streamline fairwater can significantly improve the flow quality, thus considerably reducing the pressure fluctuations and flow-induced noise. The paper is conductive to the academic research of flow noise of submarine as well as the new submarine design in the future.
Research on vibration characteristics and its key influencing factors of new mechanical elastic wheel
Authors: Wang Qiang , Zhao Youqun , Lin Fen , Fu Hongxun , Du Xianbin
Published: January 2017

This paper presents the vibration characteristics and its key influencing factors of a new mechanical elastic wheel (MEW). The MEW was modeled as a ring on elastic foundations (REF) with distributed spring stiffness in the radial and tangential directions. The general forced solutions of inextensible vibration were derived by the use of a modal expansion technique and Arnoldi method, and the accuracy of the solutions had been validated by FEM simulation and modal test under free suspension and various loading situations. The natural frequencies and mode shapes of the rotating MEW could be obtained under free suspension and various loading situations. Moreover, the effects of various rotational speed, loading and different number of hinges on natural frequencies were investigated. Finally, the effect of different number of hinges on the damping ratio of the MEW radial modes was also analyzed. The analysis results reflect the objective law of the actual vibration characteristics of the MEW, and provide a reference for the MEW structure optimization and the vibration characteristics of the whole vehicle.
Numerical simulation of dynamic response characteristics for launch and recovery system under random irregular wave
Authors: Jin Yongping , Wan Buyan , Liu Deshun , Peng Youduo , Cai Zhihua , Dong Jianghui
Published: January 2017

Based on the rain-flow counting method, a new random numerical simulation method for evaluating dynamic response characteristics of a launch and recovery system is presented in this study. It takes a random irregular wave as an input, and the random distribution characteristics of the dynamic responses of the launch and recovery system of a seafloor drill is analyzed by using the rain-flow counting method. The nonlinear coupling mechanisms among the movements of the ship, the umbilical cable, and the seafloor drill caused by random irregular wave are investigated. A dynamic model that considers the influence of the seawater resistance on the launch and recovery system of seafloor drill is established. Then, significant wave heights are used to produce excitation of the random irregular wave, and the corresponding dynamic random responses of the launch and recovery system are calculated and analyzed. At the same time, the movement of the seafloor drill and the tension of the umbilical cable are calculated and analyzed for the cases of seafloor drill at different water depths. This method provides a new tool for evaluating the dynamic response characteristics of launch and recovery system of other seafloor equipment under random irregular wave.
Free vibration analysis of truncated circular conical shells with variable thickness using the Haar wavelet method
Authors: Dai Qiyi , Cao Qingjie , Chen Yushu
Published: January 2017

This paper investigates the free vibration characteristics of truncated conical shells with variable thickness using the Haar wavelet method. Based on the Love first-approximation theory, the governing partial differential equations are formulated, which are transformed into ordinary differential equations using the separation of variables. The Haar wavelet discretization method is introduced to predict the dynamic characteristics of truncated circular conical shells with linearly and parabolically varying thickness. The present analysis is validated by comparing the numerical results with those available in the literature and very good agreement is achieved. The effects of geometrical parameters and boundary conditions on the vibration characteristics of conical shells with variable thickness are presented. The advantages of this method consist in its simplicity, fast convergence and high precision.
Improved algorithm of three-dimensional beamforming based on spatial cross-array
Authors: Song Shaoyu , Xu Zhongming , Li Shu , Chen Si , Zhang Zhifei , He Yansong
Published: January 2017

Three-dimensional beamforming based on microphone array signal processing is the expansion of traditional 2D beamforming. However, its identification accuracy is often badly reduced by the effect of grating lobes and side lobes. To overcome this problem, a method called the hybrid method beamforming (HMB) combining functional generalized inverse beamforming with multiplicative filter of spatial cross-array is proposed. In this method, the statistically optimal processing and iterated generalized inverse beamforming with regularized matrix function are utilized to obtain initial result. Then the high order function is applied to filter the output. Subsequently, a novel non-uniform spatial cross-array optimized by genetic algorithm is used to obtain sound pressure distribution. The array consists of three orthogonal sub-arrays. Mutual cancellation is realized by computing respectively with data of sub-arrays and multiplying together. With fewer microphones, the result of the improved method can be obtained with a higher spatial resolution. The proposed method is verified by the simulation and the source localization test in a room. Compared with the conventional frequency domain beamforming (FDBF) algorithm and statistically optimal array processing (SOAP) beamforming, the performance of the proposed method is significantly improved in terms of resolution of the acoustic source.
A novel tension monitoring device of multi-rope friction hoister by using acoustic filtering sensor
Authors: Xu Guiyun , Da Jianpu , Zhang Xiaoguang , Han Mengfang , Xia TingTing
Published: January 2017

Wire rope tension is one of the vital monitoring parameters for the hoister system, which seriously influence mine coal safety production. However, wire ropes endure vibration and shock in lifting process of multi-rope friction hoisters in coal mine, which interferes with measurement of wire rope tension and lifting load seriously. Aimed to the difficulty of monitoring wire rope tension, this paper put forward a new measurement method of wire rope tension by transferring wire rope tension measurement to pressure measurement, which improves the measurement safety and avoids the safety hazards of adopting pull sensor in series with wire rope, and this paper also designed an acoustic filtering sensor which uses the filtering characteristic of acoustic cavity to eliminate the effect of vibration and shock in wire rope tension measurement. Meanwhile, a novel wire rope tension monitoring device of multi-rope friction hoister is presented based on the proposed measurement method and sensor, which can measure each wire rope tension in the lifting process, display the cage load and monitor the fault of wire rope tension unbalance. Real-time and accurate wire rope tension measurement is realized. By comparing the signals measured by the common sensor and the acoustic filtering sensor, the influence of vibration and shock on the multi-ropes tension measurement is eliminated, and the fault of wire rope tension unbalance can be monitored. This advanced tension monitoring device is of great significance to the safety of coal mine production.
Multiple damage detection and localization in beam-like and complex structures using co-ordinate modal assurance criterion combined with firefly and genetic algorithms
Authors: Khatir Abdelwahhab , Tehami Mohamed , Khatir Samir , Abdel Wahab Magd
Published: January 2017

Damage detection and localization in civil engineering constructions using dynamic analysis has become an important topic in recent years. This paper presents a methodology based on non-destructive detection, localization and quantification of multiple damages in simple and continuous beams, and a more complex structure, namely two-dimensional frame structure. The proposed methodology makes used of Firefly Algorithm and Genetic Algorithm as optimization tools and the Coordinate Modal Assurance Criterion as an objective function. The results show that the proposed combination of Coordinate Modal Assurance Criterion and Firefly Algorithm or Genetic Algorithm can be easily used to identify multiple local structural damages in complex structures. However, the convergence rate becomes slower for the case of multiple damages compared to the case of single damage. The effect of noise on the algorithm is further investigated. It is found that the proposed technique is able to detect the damage location and its severity with high accuracy in the presence of noise, although the convergence rate became slower than in the case when no noise is present. It is also found that the convergence rate of Firefly Algorithm is much faster than that of Genetic Algorithm.
Pedestal looseness extent recognition method for rotating machinery based on vibration sensitive time-frequency feature and manifold learning
Authors: Chen Renxiang , Mu Zhiyan , Yang Lixia , Xu Xiangyang , Zhang Xia
Published: January 2017

To realize automation and high accuracy of pedestal looseness extent recognition for rotating machinery, a novel pedestal looseness extent recognition method for rotating machinery based on vibration sensitive time-frequency feature and manifold learning dimension reduction is proposed. Firstly, the pedestal looseness extent of rotating machinery is characterized by vibration signal of rotating machinery and its spectrum, then the time-frequency features are extracted from vibration signal to construct the origin looseness extent feature set. Secondly, the algorithm of looseness sensitivity index is designed to filter out the non-sensitive feature and poor sensitivity feature from the origin looseness extent feature set, avoiding the interference of non-sensitive and poor sensitivity feature. The sensitive features are selected to construct the looseness extent sensitive feature set, which has stronger characterization capabilities than the origin looseness extent feature set. Moreover, an effective manifold learning method called linear local tangent space alignment (LLTSA) is introduced to compress the looseness extent sensitive feature set into the low-dimensional looseness extent sensitive feature set. Finally, the low-dimensional looseness extent sensitive feature set is inputted into weight K nearest neighbor classifier (WKNNC) to recognize the different pedestal looseness extents of rotating machinery, the WKNNC’s recognition accuracy is more stable compared with that of a k nearest neighbor classification (KNNC). At the same time, the pedestal looseness extent recognition of rotating machinery is realized. The feasibility and validity of the present method are verified by successful pedestal looseness extent recognition application in a rotating machinery.
Nonlinear vibration characteristic of strip mill under the coupling effect of roll-rolled piece
Authors: Liu Bin , Jiang Jiahao , Liu Fei , Liu Haoran , Li Peng
Published: January 2017

In the existing friction coefficient models, the influence of relatively horizontal vibration of rolled piece is always overlooked, this makes the friction coefficient model error and ultimately affects the accuracy of vibration model of rolling mill. In order to be more close to the actual situation, the vertical vibration model of strip mill is established by considering the effect of horizontal vibration of rolled piece. The approximate analytic solutions are obtained by multiple scales method. Then, bifurcation characteristics of system are analyzed by means of Singularity theory. Finally, frequency responses of system are investigated with the change of external excitation amplitudes and internal nonlinear parameters. Results show that vibration behavior of system changes with the external excitation amplitudes and frequencies, internal nonlinear parameters and coupling parameters. Moreover, the unstable frequency region of system can be obtained by amplitude-frequency curve.
A high-energy liquid-jet hammer with specially designed backward stroke end buffer structure
Authors: Zhang Xinxin , Peng Jianming , Yin Kun , Yin Qilei , Wu Dongyu
Published: January 2017

A high-energy liquid-jet hammer with specially designed backward stroke end buffer structure was investigated computationally. Computational Fluid Dynamics (CFD) with the technique of dynamic and sliding meshes method was employed in this study. Results indicated that each of the geometric parameter of the buffer structure had a significant effect on the backward impacting energy of the impact body and brought a maximum of 49.8 % of backward impacting energy reduction. Experimental tests based on the non-contact measuring method were conducted to verify the simulation results, by which the accuracy and reliability of this CFD simulation method was proved. In addition, the high-energy liquid-jet hammer worked well with the optimal parameters of the buffer structure in bench testing and reached high penetration rate in a drilled borehole.
Design of mission adaptive landing gear for near space travel lander
Authors: Huang Mingyang , Nie Hong , Zhang Ming , Wei Xiaohui , Yue Shuai
Published: January 2017

The ability to perform vertical takeoff and landing reliably and safely is of great concern for a near space travel lander carrying passengers. Oblique and uneven terrains can severely limit the degree of landing safety, so mission adaptive landing gear is designed and analyzed for its function of automatic adjustment before touchdown. The legs of mission adaptive landing gear are composed of shock absorbers and actuating cylinders, which can adjust angles of the main struts relative to the capsule under control, ensuring all feet touch the irregular surface together. Compared with a conventional landing gear, scaled test and dynamic simulation in three typical conditions verify that the new design can reduce the rotation angle and the translational motion of the capsule to less than 3 degrees and 1 meter, respectively. For buffer process, the overall design reduces peak load of the lander by more than 24 %, enhances efficiency of the shock absorber to more than 85 % and optimizes stroke lengths of shock absorbers. While landing on a slope with an angle of less than 31 degrees, mission adaptive landing gear can ensure the capsule’s maximum overload less than 5 and the capsule’s attitude angle less than 20 degrees, respectively. Landing performance shows that mission adaptive landing gear is robust to uncertain conditions of the landing surface.
Time variant natural frequencies of a roadway bridge under stochastic vehicle flow
Authors: Ye Mao , Chen Xiangxiang , Ren Min , Cao Baoxing , Huang Shifan
Published: January 2017

A general framework for investigating the on-load frequencies of roadway bridges under stochastic traffic flows was developed. The cellular automaton (CA) model was adopted to develop the stochastic traffic flow. The on-load natural frequencies of the bridge are analyzed statistically. The results show that the on-load frequencies of bridge are less than the corresponding natural frequencies of the bridge. For higher or lower traffic occupancies, the fluctuation of on-load natural frequencies of the bridge becomes smaller than that under the middle range of traffic flow densities. A linear relationship exists between the mean frequency difference and the traffic flow density, with the mean slope of regression lines for the first four natural frequencies being 0.0844. There is a stronger linear relationship between the mean frequency difference and the total traffic weight, with the mean slope being 0.482. Based on traffic flow density or total traffic weight on the bridge, it is possible to make an estimate of the effect of traffic flows on the on-load frequency of a reinforced concrete continuous beam bridge using the regression relationships.
Optimum microgeometry modifications of herringbone gear by means of fitness predicted genetic algorithm
Authors: Qiu Pengyuan , Zhao Ning , Wang Feng
Published: January 2017

This paper presents a systematic methodology focused on herringbone gear microgeometry modifications toward vibration reduction. The dynamic model considering the unique characteristics of aviation herringbone gear is developed to study the vibration behavior. The optimal ease-off shape can be defined as the outcome of a multi-objective optimization process, the objective functions are loaded transmission error, meshing impact excitation and root mean square (RMS) of vibration acceleration. With special attention given to computational efficiency, a novel fitness predicted genetic algorithm is developed. An application to herringbone gear are presented, the results show the proposed method can obtain optimal modifications that significantly improve the gear performance over a wide range of operating conditions. Furthermore, the reduction of the vibration also leads to a reduction of bending stresses. Finally, a test on herringbone gear is executed under various combinations of torque and speed to demonstrate the accuracy of the proposed model.
Research on numerical simulation and noise reduction of aerodynamic noise in connection section of the high-speed train
Authors: Wu Jin-mei
Published: January 2017

The flow field distribution characteristics of side windshields and full windshields installed in the connection section of a high-speed train were numerically computed to reduce the aerodynamic noise and improve operating environment of the high-speed train. As shown from the result, the maximum pressure was at the nose tip of the high-speed train; and the greatest flow velocity of fluid was centered in the middle section of the body, while the flow velocity at both ends of the body was relatively small. After installing a side windshield, the fluid pressure of the side was significantly lower than the upper and lower surfaces, and the pressure and turbulence intensity were greater at the corner of the connection section steps. The fluid flowed to the steps from the roof of the train, and then spread gradually down along the side, with the decreasing flow rate. Therefore, the airflow was effectively prohibited from flowing into the train through installing side windshields. However, after further installing full windshields, the pressure, flow velocity and turbulence intensity in the connection section of the high-speed train were further improved. Then, the boundary element method was applied to compute the radiation noises of two kinds of windshields installed in the connection section of the high-speed train. As shown from the result, broadband radiation noise was in the upper connection section, the maximum sound pressure level (SPL) value was between 50-100 Hz and some directivity of sound pressure was shown in the high-frequency range. A certain periodicity of sound pressure distribution was presented in the longitudinal symmetrical plane of the high-speed train. At the same observation point, the sound pressure level of full windshield was slightly reduced at most frequency points, and the maximum reduction value was 23.6 dB. Finally, the wind tunnel test was conducted on the high-speed train, and the connection section of the high-speed train was the obvious noise source, thus indicating that the research in the paper was very meaningful. Besides, from SPL comparisons of the observation point, experiments and simulations were consistent with each other whether side windshields or full windshields were installed in the connection section. As a result, the reliability of the numerical computational model and the effectiveness of the results and analysis were verified.
Numerical computation of aerodynamic noise of two tandem circular cylinders and flapping wing motion based on immersed boundary method
Authors: Meng Zhi-jun , Zhou Yao-ming , Li Dao-chun
Published: January 2017

With the continuous development of theories, numerical computations and computational conditions, computational aero-acoustics presents huge advantages when they are used to solve the aerodynamic noise. Under low Mach number, objects with complex geometric profiles were selected as the research objects to research their aerodynamic noises at stationary and motion conditions by means of hybrid flow and sound separation algorithm for aerodynamic noise based on immersed boundary method (IBM). Firstly, the incompressible flow field was solved based on immersed boundary method, in order to obtain the flow field parameters as the input values, and solve the linearized acoustic perturbation compressible equation under non-uniform Cartesian meshes. As a result, the generation and diffusion of acoustic waves can be simulated. The circumferential flow field of two tandem circular cylinders was firstly completed and compared with the published test results to verify its reliability of the method proposed in this paper. And at different observation points, the noise distribution characteristics of two tandem circular cylinders were studied, showing that the noise in the vertical plane was distributed symmetrically and its noise intensity was greater than that in the horizontal plane. Moreover, the effect of different cylindrical diameters on radiation noise distribution was also studied, showing that the larger the cylindrical diameter was, the radiation noise close to the cylinder was smaller. Sound radiation problems of flapping wing motion were further studied by IBM, and this model was featured with obvious directivity in terms of its acoustic radiation, similar to the dipole sound source, and obvious periodicity regarding its acoustic pressure distribution. With good generality and practicability, this method can be also used for solving aerodynamic noise problems of other machines.
Analytical solution for nonlinear vertical vibration model of mill roll system based on improved complexification averaging method
Authors: Zhu Yong , Jiang Wan-lu , Kong Xiang-dong , Wang Hao-nan
Published: January 2017

Rolling mill is the core equipment in modern iron and steel industry, and the reliability of its mill roll system (MRS) is the key to ensure the rolling process with high precision, high speed, continuity and stability. However, the MRS possesses some features such as high nonlinearity, time variability and strong coupling. The vertical vibration easily happens in its working process. Nevertheless, the mathematical model of MRS is difficult to be established and hard to be solved. In this paper, the nonlinear dynamics theory and modern signal processing method were introduced to solve this difficult problem. A two degree of freedom (DOF) nonlinear vertical vibration model of MRS was established. And the model was analytically solved by using complexification averaging (CA) method. The solution error of CA method was thoroughly analyzed. Moreover, the CA method was improved by combining the fast empirical mode decomposition (FEMD) method. Research results indicate that the improved CA method presents a significant advantage in improving the solution precision, and can be used to solve strong nonlinear vibration system (NVS) with two DOF.
Numerical computation of aerodynamic noises of the high speed train with considering pantographs
Authors: Wang Ya-hui , Wang Jian-ting , Fu Liu-qiang
Published: January 2017

With the improvement of the speed, aerodynamic noises of trains also become more obvious. Reducing the aerodynamic noise has become a key factor to control noises of the high speed train. This paper uses large eddy simulation and boundary element method to compute the flow field and aerodynamic noises of pantographs and trains. The result presents that there are obvious eddies at the head, push rod, and base. Two obvious separation eddies can be found around the guide rod of the head and the push rod of pantographs. The front part of the base has a layer of shear flow, which leads to a separation eddy in the back of the base while the flow moves backward. Noises of pantographs mainly concentrate around the head, base and pushrod. With the increase of the analyzed frequency, the strength of pantograph noise source is weaker and weaker. When the analyzed frequency is 500 Hz, the noise source of pantographs is mainly around joints of several structures. By comparing the computational and the experimental result of aerodynamic noises of pantographs, this result presents that they are consistent with each other in the change tendency and value within the whole analyzed frequency. This indicates that the computational model of aerodynamic noises of pantographs is effective. Pantographs have an obvious influence on the distribution of the flow field around high speed trains, especially at the end of high speed trains. High speed trains with pantographs only have an eddy at the end, but high speed trains without pantographs have two eddies at the end. When this paper conducts on numerical computation for high speed trains, pantographs should not be ignored. In the low frequency, radiation noises of high speed trains can be found mainly around pantographs and at the end of trains. At the longitudinal symmetric plane of high speed trains, the sound pressure level at the end of trains is the highest. The radiation noise around pantographs mainly concentrates around the pushrod, then base, and the last is the head.
Backstepping integral control for hydraulic servo system based on LuGre friction model
Authors: Tang Hongyu , Tian Pan
Published: January 2017

A hydraulic shaking table has obvious frictional characteristics that will result in the deterioration of test waveforms and affect test accuracy. In this study, the influence of nonlinear friction for a hydraulic shaking table test system is analyzed briefly. For dynamic friction parameters and unknown system load characteristics, a mathematical model is developed based on the LuGre friction model, and double nonlinear observers are constructed to estimate average deflection. A backstepping integral control method is proposed to compensate the nonlinear friction and estimate the unknown load disturbances. The stability of the closed-loop system is proved by the Lyapunov function. In the test, an iterative control algorithm is utilized to obtain the system inverse transfer function. The experimental results show that the proposed method can reduce the nonlinear friction of the hydraulic servo system, and improve the control accuracy of the hydraulic shaking table. In addition, high identification accuracy for system impedance is also achieved. Compared to no friction compensating method, the acceleration waveform distortion is reduced from 19 % to 5 % and the peak error is reduced from 14 % to 4.2 % by the proposed method, and the deviation of power spectral density is also reduced effectively.
Energy harvesting characteristics of PVDF layers on thin-walled structures with curved surface
Authors: Zhang Yahong , Zhang Meng , Luo Yajun , Zhang Xinong
Published: January 2017

Energy harvesting properties of PVDF layers partially covered on double-curved shallow shells are studied. Firstly, the analytical expressions of voltage on the PVDF layers induced by shell vibration are derived; then the contribution to the voltage from vibrations in different directions is explored and also the effect of geometric parameters is analyzed. The results obtained theoretically indicate that: (1) The PVDF layers used on curved surface possess higher energy harvesting capabilities than those used on planar surface. (2) With the decreasing of radius of the shell, the energy harvesting capability of the PVDF layers is improved. (3) The energy harvesting ability of the laminated PVDF layers is better than that of single layer when laminated layers are connected in series mode. To validate the analytical results, energy harvesting experiments of PVDF layers on a straight beam and a curved beam are carried out comparatively. The voltage induced by vibration of the curved beam is much higher than that produced by the straight beam and the energy harvesting rate of PVDF layers on the curved beam is more rapidly than that on the straight beam. Furthermore, the voltage on the laminated PVDF layers in series connection is almost the summation of the voltages of PVDF layers which work separately. The results obtained experimentally are in agreement with those obtained analytically.
A novel servo control method based on feedforward control – Fuzzy-grey predictive controller for stabilized and tracking platform system
Authors: Wang Meng , Zhang He , Wang Xiaofeng , He Yunfeng , Lu Jianshan
Published: January 2017

Through analysis of the time-delay characteristics of stabilized and tracking platform position tracking loop and of attitude disturbance exciting in stabilization and tracking platform systems, a compound control method based on adaptive fuzzy-grey prediction control (CAGPC) is proposed to improve the disturbance suppression performance and system response of stabilized and tracking platform system. Firstly, the feedforward controller which is to improve disturbance suppression performance of stabilized and tracking platform servo system and aiming at the external disturbances is introduced. Secondly, aiming at the disadvantages of conventional fixed step size of Fuzzy-grey prediction and the prediction error forecast model has, an adaptive adjustment module adjusting the prediction step and comprehensive error weight at the same time is proposed, according to the actual control system error and the prediction error, the Fuzzy-grey prediction step and the prediction error weights are regulated while to improve the control precision and the adaptability of the system prediction model; At last, Numerical simulation results and the stabilized and tracking platform experimental verification illustrate that the compound control method can improve the stable platform servo system response and the ability of suppress external disturbances and the CAGPC control method has better performance in the stabilized and tracking platform system.
On the role of surface permeability for the control of flow around a circular cylinder
Authors: Liu Hanru , Wei Jinjia
Published: January 2017

The circular cylinder with porous materials coating (PMC) is studied in detail to reveal the sensitivity of surface permeability to the flow control and noise reduction. Two-dimensional simulations were firstly used to identify the critical values of permeability and thickness. Parametric study results show that, there is a critical permeability value which produces the minimum force fluctuation and maximum noise reduction. Additionally, the porous coating can work more efficient for noise reduction with larger thickness. The further three-dimensional simulation is employed to understand the underlying physical mechanisms of flow control. The results show that the spanwise vorticity is modified more than that of other directions and behaves more synergistically. The pressure field adjacent to the cylinder surface indicates that the adverse pressure gradient is changed to the favorable pressure gradient around the porous surface which contributes partly to the vortex shedding suppression.
Experimental investigation of the transverse nonlinear vibration of an axially travelling belt
Authors: Chen En-Wei , Lin Hui-Hui , Ferguson Neil
Published: January 2017

From an experimental perspective, this paper investigates the transverse vibration present in an axially travelling belt undergoing uniform motion with constant travelling speed. Application of a control of the belt speed, using Matlab, a Code Composer Studio (CCS) and the available complementary embedded tools, a stepper motor DSP control was obtained automatically by using a graphical method to establish the stepper motor movement models within a Simulink environment. By changing the tension of the belt and the rotational speed of the stepper motor, the natural frequency of the travelling belt was studied. The response waveforms, spectral content and phase diagrams were obtained by measuring the transverse vibration displacement under different conditions. A nonlinear model for the experimental moving belt system was developed and numerical solutions calculated. Subsequently, the nonlinear response behavior of this model were validated by the results of the experiment. It was shown that there were many scenarios for which the system can exhibit periodic motion, chaotic motion and beat frequency phenomena to be present and measured in the vibration of the axially travelling belt.
Optimization of the control scheme for human extremity exoskeleton
Authors: Li Yang , Xu Cheng , Guan Xiaorong , Li Zhong
Published: January 2017

One kind traditional PI (Proportion Integration) control scheme was proposed to be applied to human extremity exoskeleton (HEE, for short) in our previous works, and the simulation study and experimental study was also carried out. By analyzing the simulation calculation results, it was shown that the traditional PI controller is not very appropriate for human body in every movement speed condition. So, at last the fuzzy self-adaptive PI controller was proposed to solve this problem. Eventually, the superiority and feasibility of the fuzzy self-adaptive PI controller was proved by the simulation results and experimental results.
Free vibration solution of thick plate by using three-dimensional coupled thermoelastic theory
Authors: He Huan , He Cheng , Chen Weimin , Chen Guoping
Published: January 2017

This paper reports on the free vibration solution of a thick plate by using three dimensional coupled thermoelastic theory. Many previously works reveal that the mechanical and thermal are coupled together, which mean that the deformation of the solid will produce temperature variation inside the solid. First, based on the three dimensional coupled thermoelastic theory, the governing equations of the thick rectangular plate for free vibration analysis are derived. Unlike the traditional first order or third order shear deformation theory with which the deformations along the thick direction are described by the deformations of the middle surface, a new form which use functions to describe the deformations along plate thick direction (the z direction) is presented in this paper. Galerkin method and Laplace transform are applied to convert the governing equations into a series of first order ordinary differential equations as well as the boundary conditions to obtain the closed solution of the coupled thermoelastic rectangular plate. The Newton iterative method is applied to solve the eigenfunction. Finally, a thick plate with four edges simply supported has been investigated by using the proposed method. Eigensolutions and the damping effects of the plate with thermoelastic coupling are investigated by numerical example.
Performance study of the aortic valves with abnormally thickened leaflets during systole
Authors: Hsu Cheung-Hwa , Ou Chao-Hui , Vu Ha-Hai
Published: January 2017

Utilizing numerical simulation, this study investigated the performance of aortic valves with abnormally thickened leaflets during the systolic phase of the cardiac cycle. The method used coupled computational fluid dynamics and finite element analysis simulations to solve flexible structures interaction with surrounding fluid flow in the valves. The valve model was developed with a valve height of 10 mm, a free edge angle of 0 degrees, a leaflet thickness of 0.2 mm and a valve radius of 23.5 mm. Different cases of valve diseases were considered, including cases involving one thickened leaflet and cases involving two thickened leaflets. In these studied cases, the thickness of the diseased leaflet or leaflets was thicker than that of a normal one by 50 %, 100 % and 150 %, respectively. High shear stresses were discovered during leaflets acceleration period along with big leaflets distortions for all six diseased valve models. The diseased valve with 150 % thicker leaflets experienced a shear stress of up to 98.6 Pa that could disrupt the functions of the valve and therefore lead to severe problems of the cardiovascular system.
Design of a bionic-inspired exoskeleton robot for lower limb assist
Authors: Sun Yun-Ping , Chen Shuo-Ching , Liang Yen-Chu , Wu Lung-Nan
Published: January 2017

The design of an intelligent exoskeleton robot with pneumatic artificial muscles for human lower limb motion assist using electromyography (EMG) is presented. There are four topics addressed in this paper. Decoding electromyography is the first topic. When muscles are active, they produce an electrical activity. EMG is a record of this electrical activity that reflects human’s movement. Through regression analysis a model is obtained to extract motion commands from EMG. It would be an advantage to employ EMG as a control signal for the exoskeleton control. Second, the pneumatic artificial muscle, air muscle for short, is a simple and powerful actuator. When actuated with compressed air, it contracts and provides a pulling force. As a result of its behavior in a similar way to a biological muscle, air muscle is adapted for a bionic actuator of the assist robot. The force models of air muscles are investigated by experiments in a workbench. Third, for the control of a bionic-inspired robot, the multimodal sensory feedback including EMG and inertial sensors is necessary. By using EMG as a force-proportional measurement between human and robot, a control system combined a sensor-fusion approach and a compliant mechanism enables exoskeleton to carry out human-robot collaboration. Finally, a prototype of power-assist exoskeleton robot for lower limb is completed and evaluated by experiments successfully.
Analytical model for nonlinear vibration of flexible rotor system
Authors: Wu Min , Yang Shengbo , Han Dongjiang , Yu Daren , Yang Jinfu
Published: January 2017

An analytical model is proposed to analyze a series of typical nonlinear behaviors of flexible rotor system, such as resonance, oscillation, whirl and whip. The model is constructed by introducing a defined nonlinear scale factor ε, nonlinear stiffness and nonlinear damping. Based on multi-scale method, the analytical solutions of steady-state and transient-state are derived, and the nonlinear natural frequency and Frequency Response Equation (FRE) are obtained. A transient time scale factor t1 is defined to reflect the transient-state influence on steady-state solution. The experimental result also verifies the rationality and validity of the analytical model and the analytical solutions.
Remaining life prediction of rolling bearing based on PCA and improved logistic regression model
Authors: Wang Fengtao , Wang Bei , Dun Bosen , Chen Xutao , Yan Dawen , Zhu Hong
Published: January 2017

Rolling bearing reliability assessment and remaining useful life (RUL) prediction are crucially important for improving the reliability of mechanical equipment, reducing the probability of sudden failure, and saving on maintenance costs. Novel prediction method is proposed based on PCA and Improved Logistic Regression Model (ILRM) to solve the problem that the model is difficult to establish and the remaining life of rolling bearing is difficult to estimate. Time domain, frequency domain, and time-frequency domain feature extraction methods are employed in this study to extract the original features from the vibration signals. Next, the relative feature value is used to reduce the influence of random vibration and individual differences between bearings. PCA is run based on the original extracted features and high dimensional and superfluous information to merge the original features and reduce the dimension, where typically sensitive features are extracted. The ILRM is then used to build a model that reflects the deterioration trend and eliminates the impact of fluctuations, ultimately yielding information regarding the rolling bearing’s reliability and the remaining life. The proposed method is shown to accurately predict the lifespan of rolling bearings, thus exhibiting practical value in the engineering field.
Biomechanical assessment of brain dynamic responses due to blast-induced wave propagation
Authors: Yang Bin , Wang Qun , Li Peng , Tang Yong , Wang Yu , Shi Zheng , Cao Li-Bo
Published: January 2017

Traumatic brain injuries (TBI) due to blast-induced wave propagation are not well studied owing to limited published literatures on the subject. This study demonstrates the utilization of a head-helmet model and investigates the effect of using a faceshield with different configurations of laminate composites of polycarbonate and aerogel materials. The model validation is performed against studies published in the literature. The processes of blast wave propagation in the air and blast interaction with the head are modeled by a Coupled Eulerian-Lagrangian (CEL) multi-material finite element method (FEM) formulation, together with a fluid-structure dynamic interaction algorithm. The effectiveness of the different faceshield configurations when exposed to a frontal blast wave with one atmosphere (atm) peak overpressure is evaluated. Results show that the helmet with faceshield can delay the transmission of blast waves to the face and lower the skull stresses and intracranial pressures (ICP) at the frontal and parietal lobes in the first 1.7 ms. Faceshields with a combination of polycarbonate and aerogel layers perform better than the fully polycarbonate ones. It is also revealed that the single 0.6 mm thick aerogel layer in the 3-layer configuration and two layers of 0.6 mm thick aerogel in the 5-layer configuration are the most effective. The paper provides insights into the interaction mechanics between the biological head model and the blast wave.
Study of vibrating drag reduction mechanism during horizontal drilling in slim borehole
Authors: Wang Yu , Xia Bairu , Wang Zhiqiao , Zou Jun , Liu Baolin
Published: January 2017

Resource reserves can be effectively controlled through slim borehole horizontal drilling, which can significantly reduce costs and enhance efficiency. Therefore, it has been widely used in petroleum, geothermal, shale gas and water resources exploration. But the large friction between the drilling string and borehole can cause downhole accidents. In this paper, a new method of vibrating drag reduction is proposed, with using turbine to drive the rotary valve to control flow. Axial vibration excitation produced by high-pressure water can greatly reduce the friction. Firstly, a rotary valve mathematical model with flow hydraulic oscillation and vibration is established, whose work characteristics are simulated using numerical methods. And then lab experiments are conducted to verify the design.