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1
Thater, G., P. Chang, D. R. Schelling, and C. C. Fu. "Estimation of bridge static response and vehicle weights by frequency response analysis." Canadian Journal of Civil Engineering 25, no. 4 (August 1, 1998): 631–39. http://dx.doi.org/10.1139/l97-128.
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A methodology is developed to more accurately estimate the static response of bridges due to moving vehicles. The method can also be used to predict dynamic responses induced by moving vehicles using weigh-in-motion (WIM) techniques. Historically, WIM is a well-developed technology used in highway research, since it has the advantage of allowing for the stealthy automatic collection of weight data for heavy trucks. However, the lack of accuracy in determining the dynamic effect in bridges has limited the potential for its use in estimating the fatigue life of bridge structures and their components. The method developed herein amends the current WIM procedures by filtering the dynamic responses accurately using the Fast Fourier Transform (FFT). Example applications of the proposed method are shown by using computer-generated data. The method is fast and improves the predicted truck weight up to 5% of the actual weight, as compared to errors up to 10% using the current WIM methods.Key words: weigh-in-motion, digital filters, FFT, bridge dynamics, in-service testing.
2
Zhan, Qinjian, Xigui Zheng, Niaz Muhammad Shahani, Xiao Tan, Tao Li, and Jiping Du. "Analysis of Dynamic Response Mechanism of Roadway Bolt." Advances in Civil Engineering 2021 (July 5, 2021): 1–15. http://dx.doi.org/10.1155/2021/5560075.
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This work elucidates dynamic control equations of the anchoring system and the derivation of displacement equations and corresponding vibration modes. Furthermore, the anchoring system is found to be composed of three different vibration modes: (1) when ω < (k1/ρ1A1)1/2, the vibration mode of the anchoring section is an exponential function; (2) when ω = (k1/ρ1A1)1/2, the vibration mode of the anchoring section is a parabolic function; (3) when ω > (k1/ρ1A1)1/2, the vibration mode of the anchoring section is a trigonometric function, while all the free sections are trigonometric functions. With an increase of frequency, the amplitude of the bolt exhibits multipeak distribution characteristics and an intermittent amplification phenomenon. When the frequency reaches a certain value, the bolt of the free section exhibits only the amplified state. Under dynamic load, the amplitude of the bolt increases from end of bolt to the maximum in the root. On the other hand, when the frequency is low, the peak position of the roof bolt is stable, and the excitation wave component is the main influencing factor of the peak value of axial force at the root of the bolt, independent of frequency. When the frequency is relatively high, the peak value of the axial force is stable at the interface, and the higher the frequency, the greater the peak value of axial force. Axial force of the bolt has responded strongly to the frequency at the interface, and the farther away from the interface, the weaker the response.
3
Staszewski, W. J. "Analysis of non-linear systems using wavelets." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 11 (November 1, 2000): 1339–53. http://dx.doi.org/10.1243/0954406001523317.
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Analysis of non-linear systems is an essential part of engineering structural dynamics. A number of methods have been developed in recent years. Classical Fourier-based methods have been extended to the use of phase plane, combined time-frequency, time-scale approaches and multidimensional spectra. This paper is an attempt to collate in one place some of the recent advances in wavelet analysis for the study of non-linear systems. This includes methods related to system identification based on wavelet ridges and skeletons, damping estimation procedures, wavelet-based frequency response functions, cross-wavelet analysis, self-similar signals, coherent structures and chaos.
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Wang, Bai Sheng, Lie Sun, and Zhi Wei Chang. "Seismic Structural Damage Detection Based on Time Frequency Response Function." Advanced Materials Research 219-220 (March 2011): 243–49. http://dx.doi.org/10.4028/www.scientific.net/amr.219-220.243.
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Considering that Hilbert-Huang Transformation (HHT) can be used to analyze instantaneous frequency in structural dynamic analysis, this paper proposes the concept of HHT marginal spectrum based time frequency response function. It also defines “central frequency”, which is used to reflect the change of structural dynamic properties during earthquakes, and discloses time-varying development of seismic structural damage. Using a three-story shear frame model, which is subjected to the El Centro seismic wave, the HHT time frequency response analysis of its acceleration response has been made, results show that the adoption of central frequency can successfully indicate the damage inception instant and its development.
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Kodkin, Vladimir L., Aleksandr Sergeevich Anikin, and Aleksandr A. Baldenkov. "The dynamics identification of asynchronous electric drives via frequency response." International Journal of Power Electronics and Drive Systems (IJPEDS) 10, no. 1 (March 1, 2019): 66. http://dx.doi.org/10.11591/ijpeds.v10.i1.pp66-73.
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<span>The article substantiates the necessity of identifying the dynamics of asynchronous electric drives with frequency control. It is proposed to use nonlinear transfer functions and the formula of a family of frequency responses of an electric drive, depending on the frequency of the stator voltage and slip. Experiments and simulations confirming theoretical conclusions are presented. The frequency responses of the drive of the stand calculated by the proposed method allowed to explain those problems of frequency control that were not explained by traditional methods - analytical, vector diagrams, substitution schemes, etc. This same technique allowed us to formulate a structural correction of the asynchronous electric drives. In contrast to the previously published research materials of asynchronous electric drives, a detailed qualitative analysis of the obtained nonlinear frequency responses and the interrelation of these characteristics with experimental results is shown for the first time in the article.</span>
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Zhang, Xing Wu, Xue Feng Chen, Shang Qin You, Xiao He, Yi Jie Wang, and Zheng Jia He. "Study on Active Control of Structural Frequency Response." Advanced Materials Research 199-200 (February 2011): 1036–40. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.1036.
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As the requirements for industrial operation and military work, the frequency characteristics should be changed artificially sometimes. Active control is a good choice, but the current active control mainly focuses on time domain for vibration control. In this paper, the structural active control on frequency domain is studied through theory and experiment. Firstly, multivariable wavelet finite element method with two kinds of variables (TWFEM) which is suitable for modeling of great and complex structures with high efficiency and precision is used to construct the mathematical model for the controlled structure and do static and dynamic analysis. Then the control algorithm based on neural network including two parts, identification implement and controller is constructed. The present study takes frequency response as control objective, and can not only do vibration control but also change the vibration frequency characteristics, providing a new perspective for active control.
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Wang, Kai Song, and Guo Qing Liu. "Derrick Spectrum Analysis Based on ANSYS." Advanced Materials Research 791-793 (September 2013): 1529–32. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.1529.
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The existing mine derrick design only includes the guiding principles and the empirical formula, but has no the mechanism of structural dynamics characteristics under an earthquake conditions. Then the modal analysis and spectral response analysis of the derrick have been finished for gaining the derrick natural frequency, mode shapes, and time response curve based on ANSYS in the thesis. The analysis results provides important basis for the anti-seismic design, optimization design and avoiding resonance.
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Wang, Xian Rong, Jia Qi Jin, and Ya Zhou Li. "The Harmonic Response Analysis of Workover Rig Platorm Base on ANSYS Workbench." Advanced Materials Research 945-949 (June 2014): 766–69. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.766.
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Normally, the workover rig platform is obtained only low order natural frequency by modal analysis. In order to understand the frequency response of structure dynamic load, we well carry out harmonic response analysis on the operation platform in this paper. On this basis, determine the modal frequency that is greatest effect on dynamic behaviour of the workover rig operation platform structural system. To extract the modal frequency as dynamic optimization goal or state variables.Finally, achieve forecast the possibility of dynamic interference between operation platform and other components.
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Jeong, TG, SS Lee, and Chang-Wan Kim. "Frequency response computation of structures including non-proportional damping in a shared memory environment." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, no. 2 (May 29, 2012): 288–98. http://dx.doi.org/10.1177/0954406212447514.
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With the increased size of the finite element model for improved accuracy, the modal frequency response analysis has been one of the common practices of evaluating the performance of vehicle dynamics. However, there is difficulty in predicting the vehicle dynamics response with non-proportional damping regarding performance. The fast frequency response analysis algorithm (FFRA) has been proved to be very effective for partially damped structural system in the modal frequency response analysis. In the fast frequency response analysis algorithm, performance depends mainly on the complex symmetric matrix eigenvalue problem. Therefore, an efficient complex symmetric matrix eigenvalue problem solver is developed in this article. This approach also uses parallel processing in a shared memory machine for more efficient analysis. Numerical examples show that the new complex symmetric matrix eigensolver provides good accuracy and high performance. Then, the fast frequency response analysis algorithm is applied to a full scale vehicle system that includes only a few viscous damping finite elements. The fast frequency response analysis algorithm significantly improves the performance of the modal frequency response analysis compared to conventional method. In addition, parallel processing improves the efficiency of the overall simulation.
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Dziedziech, Kajetan, Alexander Nowak, Alexander Hasse, Tadeusz Uhl, and Wiesław J. Staszewski. "Wavelet-based analysis of time-variant adaptive structures." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2126 (July 9, 2018): 20170245. http://dx.doi.org/10.1098/rsta.2017.0245.
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Wavelet analysis is applied to identify the time-variant dynamics of adaptive structures. The wavelet-based power spectrum of the structural response, wavelet-based frequency response function (FRF) and wavelet-based coherence are used to identify continuously and abruptly varying natural frequencies. A cantilever plate with surface-bonded macro fibre composite—which alters the structural stiffness—is used to demonstrate the application of the methods. The results show that the wavelet-based input–output characteristics—i.e. the FRF and coherence—can identify correctly the dynamics of the analysed time-variant system and reveal the varying natural frequency. The wavelet-based coherence can be used not only for the assessment of the quality of the wavelet-based FRF but also for the identification. This article is part of the theme issue ‘Redundancy rules: the continuous wavelet transform comes of age’.
11
Zentner, Irmela. "Use of RVT for Computation of In-Structure Response Spectra and Peak Responses and Comparison to Time History and Response Spectrum Analysis." Earthquake Spectra 34, no. 4 (November 2018): 1913–30. http://dx.doi.org/10.1193/051417eqs090m.
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The random vibration theory offers a framework for the conversion of response spectra into power spectral densities (PSDs) and vice versa. The PSD is a mathematically more suitable quantity for structural dynamics analysis and can be straightforwardly used to compute structural response in the frequency domain. This allows for the computation of in-structure floor response spectra and peak responses by conducting only one structural analysis. In particular, there is no need to select or generate spectrum-compatible time histories to conduct the analysis. Peak response quantities and confidence intervals can be computed without any further simplifications such as currently used in the response spectrum method, where modal combination rules have to be derived. In contrast to many former studies, the Arias intensity-based definition of strong-motion duration is adopted here. This paper shows that, if the same definitions of strong-motion duration and modeling assumptions are used for time history and RVT computations, then the same result can be expected. This is illustrated by application to a simplified model of a reactor building.
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Uyulan, Caglar, and Ersen Arslan. "Simulation and time-frequency analysis of the longitudinal train dynamics coupled with a nonlinear friction draft gear." Nonlinear Engineering 9, no. 1 (February 7, 2020): 124–44. http://dx.doi.org/10.1515/nleng-2020-0003.
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AbstractTrain safety and operational efficiency can be improved by investigating the dynamics of the train under varying conditions. Longitudinal train dynamics (LTD) simulations performed for such purposes, usually by utilising a nonlinear time-domain model. This paper covers two modes of LTD results corresponding to the time domain and frequency domain analysis. Time-domain solutions are essential to evaluate the full response used for parameter optimisation and controller design studies while frequency domain solutions can provide significant but straightforward clues regarding system dynamics. An advanced draft gear model, which works under a four-stage process is constructed considering all structural components, geometric relationships, friction modelling and dynamic characteristics such as hysteresis, stiffening, state transition, locked unloading, softening. Then, this model is parametrically reduced and implemented into an LTD simulation. The simulation in the time domain is conducted assuming a locomotive connected with a nine wagon via “ode3” fixed-step solver. The transfer function among the first wagon acceleration (output) and the locomotive force (input) estimated through system identification methodology. Then, the identification results interpreted by investigating step-response characteristic and best response giving parameter set is selected. Next, the modal and spectral analysis performed to reveal the behaviour of the in-train forces and the effects of vibration. This paper discusses a reliable methodology for the longitudinal dynamic analysis of the multi-bodied train in time and frequency domain and clarifies in-train vibration behaviour under the existence of sophisticated draft gear.
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Zhao, Guang Yao, Peng Fu, Shu Wen Zhou, and Shan Ge Tong. "Dynamic Mechanical Analysis of Automotive Gearbox Casing." Advanced Materials Research 230-232 (May 2011): 539–43. http://dx.doi.org/10.4028/www.scientific.net/amr.230-232.539.
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After the three-dimensional solid modeling of the SG135 automobile gearbox, finite element analysis models of static, transient and harmonic response load are built based on correlation theory. On the basis of ADAMS dynamic simulation of different gearbox gears, transient load of the gearbox casing at different working gears is found out. With frequency response characteristic of gearbox casing analyzed at typical working conditions of first gear and reverse gear, the evaluation of some factors such as strength and stiffness are given out, which provides theory basis for further improvement of gearbox casing structure and strengthening weak links. Based on harmonic response analysis, the impact on gearbox casing structural vibration by harmonic excitation of the engine is imitated, and the match relation of frequency response between the gearbox and the engine is analyzed. Improvements about engine operational limits matching and gearbox structural design are proposed.
14
Choi, Kyung K., and Jae Hwan Lee. "Sizing Design Sensitivity Analysis of Dynamic Frequency Response of Vibrating Structures." Journal of Mechanical Design 114, no. 1 (March 1, 1992): 166–73. http://dx.doi.org/10.1115/1.2916911.
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A continuum design sensitivity analysis method of dynamic frequency response of structural systems is developed using the adjoint variable and direct differentiation methods. A variational approach with a non-selfadjoint operator for complex variable is used to retain the continuum elasticity formulation throughout derivation of design sensitivity results. Sizing design variables such as thickness and cross-sectional area of structural components are considered for the design sensitivity analysis. A numerical implementation method of continuum design sensitivity analysis results is developed using postprocessing analysis data of COSMIC/NASTRAN finite element code to get the design sensitivity information of displacement and stress performance measures of the structures. The numerical method is tested using basic structural component such as a plate supported by shock absorbers and a vehicle chassis frame structure for sizing design variables. Accurate design sensitivity results are obtained even in the vicinity of resonance.
15
Timorian, S., G. Petrone, S. De Rosa, F. Franco, M. Ouisse, and N. Bouhaddi. "Spectral analysis and structural response of periodic and quasi-periodic beams." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 23-24 (November 28, 2019): 7498–512. http://dx.doi.org/10.1177/0954406219888948.
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Periodic structures have found a big interest in engineering applications because they introduce frequency band effects, due to the impedance mismatch generated by periodic discontinuities in the geometry, material, or boundary conditions, which can improve the vibroacoustic performances. However, the presence of defects or irregularity in the structure leads to a partial lost of regular periodicity (called quasi-periodic structure) that can have a noticeable impact on the vibrational and/or acoustic behavior of the elastic structure. The irregularity can be tailored to have impact on dynamical behavior. In the present paper, numerical studies on the vibrational analysis of one-dimensional finite, periodic, and quasi-periodic structures are presented. The contents deal with the finite element models of beams focused on the spectral analysis and the damped forced responses. The quasi-periodicity is defined by invoking the Fibonacci sequence for building the assigned variations (geometry and material) along the span of finite element model. Similarly, the same span is used as a super unit cell with Floquet–Bloch conditions waves for analyzing the infinite periodic systems. Considering both longitudinal and flexural elastic waves, the frequency ranges corresponding to band gaps are investigated. The wave characteristics in quasi-periodic beams, present some elements of novelty and could be considered for designing structural filters and controlling the properties of elastic waves.
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Li, Baohui, Zhengzhong Wang, and Lina Jing. "Dynamic Response of Pipe Conveying Fluid with Lateral Moving Supports." Shock and Vibration 2018 (November 4, 2018): 1–17. http://dx.doi.org/10.1155/2018/3295787.
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The Galerkin method is proposed to reveal the dynamic response of pipe conveying fluid (PCF), with lateral moving supports on both ends of the pipe. Firstly, the dynamic equation is derived by the Newtonian method after calculating the acceleration of the fluid element via the dynamics approach. Secondly, the discrete form of the dynamic equation is formulated by the Galerkin method. Thirdly, the numerical analysis of the system is carried out through the fourth-order Runge–Kutta method, and the effectiveness of the proposed method is validated by comparison with the analytical results obtained by the mode superposition method. In the example analysis, the responses of the lateral deflection and bending moment are investigated for the pinned-pinned, clamped-pinned, and clamped-clamped PCF. The effects of fluid velocity and the moving frequencies of supports are discussed. Especially, the deflection responses are analyzed under extreme condition; i.e., the moving frequency of a support is identical to the natural frequency of PCF.
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Qiao, Zizhen, Jianxing Zhou, Wenlei Sun, and Xiangfeng Zhang. "A Coupling Dynamics Analysis Method for Two-Stage Spur Gear under Multisource Time-Varying Excitation." Shock and Vibration 2019 (November 7, 2019): 1–18. http://dx.doi.org/10.1155/2019/7350701.
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A new modeling method is proposed to simulate the dynamic response of a two-stage gear transmission system using the finite element method (FEM). The continuous system is divided into four modules: shaft-shaft element, shaft-gear element, shaft-bearing element, and gear-gear element. According to the FEM, the model is built with each element assembled. Meanwhile, the model considers the time-varying mesh stiffness (TVMS), bearing time-varying stiffness (BTVS), and the shaft flexibility. The Newmark integration method (NIM) is used to obtain the dynamic response of the spur gear system. Results show that vibration amplitude and the number of frequency components decrease after considering shaft flexibility through comparing the gear dynamic response under the condition of flexible shaft and rigid shaft. When the effect of bearing stiffness is considered, there will be a bearing passing frequency component in the frequency spectrum. In addition, the result shows that the simulation and experimental test of the frequency component are basically consistent. Furthermore, the theoretical model is validated against an experimental platform of the two-stage gear transmission system and the dynamic responses are compared under the condition of increasing speed. Additionally, the increase of shaft stiffness not only changes some of the dominant mode shapes (torsional mode shapes) but also makes the number of primary resonance speeds added. The method can be used to guide the design of gear systems.
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Meruane, V., Sergio De Rosa, and Francesco Franco. "Numerical and experimental results for the frequency response of plates in similitude." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, no. 18 (August 9, 2016): 3212–21. http://dx.doi.org/10.1177/0954406215610148.
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The concept of structural similitude provides a powerful tool for engineers and scientists to predict the behaviour of a structure using an appropriate scaled model. Even tough theoretical and numerical investigations of similarity conditions or scaling laws have shown to be feasible, their accuracy is not necessarily guaranteed when these laws are applied to real (experimental) structures. Herein, structural scaling laws are investigated for the analysis of the dynamic response of simple flexural plates. Specifically, the possibility to define exact and distorted similitudes is discussed through numerical and experimental data. This paper focuses on exact and distorted similitudes in the analysis of the dynamic response of flexural plates. The similitude laws are defined by invoking the classical modal approach and looking for (in)equalities in the structural dynamic response. A total of seven aluminium rectangular plates with one clamped edge are modelled in finite elements and tested experimentally to study the effect of distorted similitudes and experimental variations in the performance of the predicted dynamic response.
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Li, Jie, Li Li Hu, Li Qin, Jun Liu, Rui Ping Tao, and Xi Ning Yu. "Dynamic Analysis of Piezoelectric Smart Structures." Advanced Materials Research 295-297 (July 2011): 1353–56. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1353.
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In order to solve the active vibration control of piezoelectric smart structures, focus problems on the structural analysis of the dynamic characteristics. To piezoelectric smart structure for the research object, finite element modal analysis, solving the natural frequency and response characteristics. Firstly, analyzed the problems of structural eigenvalues and eigenvectors problems, then prepared dynamic response analysis program of FEM based on MATLAB, and complete the theoretical model calculations. At the same time, using ANSYS software to simulate and analyze, theresults show that, ANSYS simulation result is consistent with the theoretical value, so as to study the piezoelectric active vibration control of smart structures and lay a good foundation.
20
Elosegui, P. "Measurement of the Dynamic Model of a PUMA 560 Robot Using Experimental Modal Analysis." Journal of Mechanical Design 116, no. 1 (March 1, 1994): 75–79. http://dx.doi.org/10.1115/1.2919380.
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This paper presents two different models of the structural dynamics of a PUMA 560 robot: a frequency response, and a modal model. The first consists of a set of frequency response functions measured from the structure. The eigenvalues and the mode-shape, which comprise the modal model, are extracted from the response model. In addition to these linear models, the paper describes the nonlinear characteristics of the structure. How the non-linearities affect the measurement technique and the model accuracy is also described.
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Jameel, Mohammed, Suhail Ahmad, A. B. M. Saiful Islam, and Mohd Zamin Zummat. "NON-LINEAR DYNAMIC ANALYSIS OF COUPLED SPAR PLATFORM." Journal of Civil Engineering and Management 19, no. 4 (September 2, 2013): 476–91. http://dx.doi.org/10.3846/13923730.2013.768546.
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Spar platforms are treated as cost-effective and resourceful type of offshore structure in deep water. With increasing depth there are significant changes in its structural behaviour due to coupling of spar hull-mooring line along with radical influence of mooring line damping. So these phenomena should be precisely counted for accurate motion analysis of spar mooring system. In present study, spar platform are configured as a single fully coupled integrated model in ABAQUS/AQUA. Non-linear dynamic analysis in time domain is performed adopting Newmark-β automatic time incrementation technique. Non-linearities due to geometric, loading and boundary conditions are duly considered. Displacement and rotational responses of spar and mooring tensions are obtained during long-duration storm. spar responses get significantly modified and mean position of oscillations gets shifted after longer wave loading. The surge, heave and pitch responses are predominantly excited respectively. The energy contents of PSDs of these responses reduce considerably after long wave loading. Mooring tension responses are significantly different reflecting the damping effect of mooring lines. The pitch response is fairly sensitive to the wave loading duration. After long duration of storm the wave frequency response increases. However, low frequency and wave frequency responses may simultaneously occur due to synchronising sea states.
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Mankour, A., A. Boudjemai, R. Amri, and H. Salem. "Analysis of Design Parameter Influence on the Dynamic Frequency Response of CFFF Honeycomb Sandwich Plate." Advanced Materials Research 682 (April 2013): 57–64. http://dx.doi.org/10.4028/www.scientific.net/amr.682.57.
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In the aerospace domain, sandwich plates represent an efficient structural element, providing a high stiffness/weight ratio characteristic. Moreover, when using this structural element, different design parameters and materials of the core can be adopted in order to obtain desired properties. When the dynamic analysis of the spacecraft structure made up of the honeycomb sandwich plates is performed in MSC Patran/Nastran. In this study a three dimensional finite elements of a clamped-free (CFFF) honeycomb plate under dynamic vibrations loading had been analysed. Geometric parameters of hexagonal plate is specific to absorb vibrations, hence the effect of each parameters is crucial to determine the rigidity of plates under a single-point cyclic loading. The effect of honeycomb core thickness, unit cell size, and the materials contribute to determine the rigidity of honeycomb plate. Therefore, all of the analysis results can accommodate bases for structural design and optimum design of the spacecraft structure.
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Si, Jia Jun, Kuan Jun Zhu, Bin Liu, and Yao Ding. "Dynamic Analysis on Steel Tower of Vertical Axis Wind Turbine." Advanced Materials Research 291-294 (July 2011): 2529–36. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.2529.
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The dynamic analysis has been adopted for the calculation of the low-order natural frequency and harmonic response data of the steel tower of vertical axis wind turbine, as well as the dynamic relation between the wind turbine and the tower. When the wheel rotates at 160rpm, the harmonic load has a very serious destructive damage to the tower. In order to avoid the system failure caused by the system resonance in the engineering design, some optimizations have been taken on satisfying the security and reliability of the tower. This study provides the scientific basis for the dynamic design and the optimization. The conclusion shows that the most effective method of raising the natural frequency is to reduce the weight of the structure when the material and the structural style are determined. As a result, the difference between harmonic response and resonance frequency of the structure rises to 21.3％ from 0.3％ after reducing the weight of the tower by 21.3％.
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Yang, Jianjin, Shengyang Zhu, and Wanming Zhai. "Modeling Slab Track for Vehicle –Track-Coupled Dynamics Analysis Using Spline Function Method." International Journal of Structural Stability and Dynamics 20, no. 02 (January 7, 2020): 2050026. http://dx.doi.org/10.1142/s0219455420500261.
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This paper presents a new approach for modeling the slab tracks by using the spline function to derive an element that is capable of describing the vertical motions of the entire slab. The accuracy and advantages of the method are verified through comparison with the finite element method (FEM) by the frequency response analysis for the CRTS-III slab track system. With this, a three-dimensional train–slab track-coupled dynamic (TSTCD) model is developed and solved by a hybrid explicit–implicit time integration method. Finally, the characteristics and feasibility of the developed TSTCD model are demonstrated through two typical case studies together with the comparison made for verifications. The results indicate that the proposed method provides an alternative approach for modeling the slabs, by simplifying the modeling process and decreasing the computational time without losing accuracy, with respect to the FEM. Besides, the modes of the slab appear many dips and peaks above the first resonant frequency, leading to complicated frequency responses of the CRTS-III slab. Moreover, the developed TSTCD model is not only feasible, but also capable of describing the slab vibrations at medium-high frequencies.
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Hu, Chao, Chenxuan Tang, Chenyang Yuwen, and Yong Ma. "Coupled Interactions Analysis of a Floating Tidal Current Power Station in Uniform Flow." Journal of Marine Science and Engineering 9, no. 9 (September 3, 2021): 958. http://dx.doi.org/10.3390/jmse9090958.
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For a floating tidal current power station moored in the sea, the mutual interactions between the carrier and the turbine are pretty complex. Current simulation methods based on potential flow theory could not consider the complicated viscous effects between the carrier motion and rotor rotation. To accurately account for the viscous effect, developing a different numerical simulation method based on computational fluid dynamics is necessary. This paper deals with a moored FTCPS (floating tidal current power station) with 6-degree-of-freedom motion in uniform flow based on dynamic fluid body interactions (DFBI) method. Results showed that the blockage effect caused by the columns would increase the average power output of the turbine, while the power output fluctuation also increased. When the carrier is individually moored in the sea, the motion response of the carrier is pretty small, and the carrier is obviously trimming by the bow. However, when the turbine is mounted on the carrier, the carrier motion response is simple harmonic. The motion response frequency of the carrier is in relation to the rotation frequency of the turbine.
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Zhou, Xiaojie, Qinghua Liang, Zhongxian Liu, and Ying He. "IBIEM Analysis of Dynamic Response of a Shallowly Buried Lined Tunnel Based on Viscous-Slip Interface Model." Advances in Civil Engineering 2019 (March 6, 2019): 1–14. http://dx.doi.org/10.1155/2019/1025483.
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A viscous-slip interface model is proposed to simulate the contact state between a tunnel lining structure and the surrounding rock. The boundary integral equation method is adopted to solve the scattering of the plane SV wave by a tunnel lining in an elastic half-space. We place special emphasis on the dynamic stress concentration of the lining and the amplification effect on the surface displacement near the tunnel. Scattered waves in the lining and half-space are constructed using the fictitious wave sources close to the lining surfaces based on Green’s functions of cylindrical expansion and the shear wave source. The magnitudes of the fictitious wave sources are determined by viscous-slip boundary conditions, and then the total response is obtained by superposition of the free and scattered fields. The slip stiffness and viscosity coefficients at the lining-surrounding rock interface have a significant influence on the dynamic stress distribution and the nearby surface displacement response in the tunnel lining. Their influence is controlled by the incident wave frequency and angle. The hoop stress increases gradually in the inner wall of the lining as sliding stiffness increases under a low-frequency incident wave. In the high-frequency resonance frequency band, where incident wave frequency is consistent with the natural frequency of the soil column above the tunnel, the dynamic stress concentration effect is more significant when it is smaller. The dynamic stress concentration factor inside the lining decreases gradually as the viscosity coefficient increases. The spatial distribution and the displacement amplitudes of surface displacement near the tunnel change as incident wave frequency and angle increase. The effective dynamic analysis of the underground structure under an actual strong dynamic load should consider the slip effect at the lining-surrounding rock interface.
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Huang, Zhi, Chaochen Ma, and Hong Zhang. "Investigation of Flow Distortion Generated Forced Response of a Radial Turbine with Vaneless Volute." International Journal of Turbo & Jet-Engines 37, no. 2 (September 25, 2020): 141–51. http://dx.doi.org/10.1515/tjj-2017-0016.
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AbstractFor a radial turbine with vaneless volute, the inflow of turbine rotor usually has a circumferential flow distortion due to the influence of the volute tongue. The rotating blades of the rotor are exposed to harmonic aerodynamic loads caused by the distortion, which may induce rotor resonance and lead to high cycle failures (HCF). To understand the forced response mechanism clearly, a numerical analysis was carried out based on a fluid structure interaction (FSI) method. The pressure functions were extracted from the results of a computational fluid dynamics (CFD) analysis by Fourier decomposition. The first three harmonic pressures were identified as the primary engine order (EO) excitations and imposed on the structural model for computational structural dynamics (CSD) simulation. The quantification and assessment of the rotor response were attained by mode superposition method. The simulation results are shown to be consistent with the predictions of Singh’s advanced frequency evaluation (SAFE) diagram.
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Zhou, Shenglin, Fengming Li, and Chuanzeng Zhang. "Vibration characteristics analysis of disordered two-span beams with numerical and experimental methods." Journal of Vibration and Control 24, no. 16 (May 11, 2017): 3641–57. http://dx.doi.org/10.1177/1077546317708696.
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Numerical and experimental investigations on the vibration behaviors of the disordered two-span beams have been conducted. The dynamics model of the two-span beam is established and solved by means of the modal superposition method. According to the boundary conditions, the frequency equation of the two-span beam is obtained, and the natural frequencies, vibration modes, frequency response curves, and time-history responses of the structure are also obtained consequently. Considering the structural size disorder due to the two different sub-span lengths of the two-span beam, a disorder ratio is introduced in terms of the two sub-span lengths and its influences on the vibration characteristics of the structure are analyzed. By comparing the results from numerical calculation with those from the finite element method (FEM) and experiments, good agreement is observed, which verifies the validity of the present investigations.
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Alzahabi, Basem, and Michael M. Bernitsas. "Redesign of Cylindrical Shells by Large Admissible Perturbations." Journal of Ship Research 45, no. 03 (September 1, 2001): 177–86. http://dx.doi.org/10.5957/jsr.2001.45.3.177.
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Structural redesign is the process of finding a new design that satisfies a set of performance requirements starting from a poorly performing design. Structural redesign is formulated as a two-state problem where the baseline design exhibits undesirable response characteristics and the objective design satisfies the design requirements. A LargE Admissible Perturbations (LEAP) methodology is developed to formulate and solve the problem of structural redesign of cylindrical shells for modal dynamics. First, the nonlinear perturbation equations of cylindrical shells for modal dynamics are derived relating the baseline to the unknown objective design. The redesign problem is formulated as an optimization problem. Next, an algorithm is developed to solve the nonlinear problem and to identify a locally optimal design that satisfies the given modal dynamics specifications. The developed LEAP algorithm calculates incrementally without trial and error or the repetitive finite-element analyses the structural design variables of the objective design. Numerical applications of cylindrical shell redesign for modal requirements are used to verify the methodology and test the algorithm. The developed methodology identifies incompatible frequency requirements where solutions cannot be achieved. Further, systematic redesign applications show that even for strip uniform shells, modes are linked, making satisfaction of multiple frequency objectives impossible.
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Rogge, Timo, Ricarda Berger, Linus Pohle, Raimund Rolfes, and Jörg Wallaschek. "Efficient structural analysis of gas turbine blades." Aircraft Engineering and Aerospace Technology 90, no. 9 (November 14, 2018): 1305–16. http://dx.doi.org/10.1108/aeat-05-2016-0085.
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Purpose The purpose of this study a fast procedure for the structural analysis of gas turbine blades in aircraft engines. In this connection, investigations on the behavior of gas turbine blades concentrate on the analysis and evaluation of starting dynamics and fatigue strength. Besides, the influence of structural mistuning on the vibration characteristics of the single blade is analyzed and discussed. Design/methodology/approach A basic computation cycle is generated from a flight profile to describe the operating history of the gas turbine blade properly. Within an approximation approach for high-frequency vibrations, maximum vibration amplitudes are computed by superposition of stationary frequency responses by means of weighting functions. In addition, a two-way coupling approach determines the influence of structural mistuning on the vibration of a single blade. Fatigue strength of gas turbine blades is analyzed with a semi-analytical approach. The progressive damage analysis is based on MINER’s damage accumulation assuming a quasi-stable behavior of the structure. Findings The application to a gas turbine blade shows the computational capabilities of the approach presented. Structural characteristics are obtained by robust and stable computations using a detailed finite element model considering different load conditions. A high quality of results is realized while reducing the numerical costs significantly. Research limitations/implications The method used for analyzing the starting dynamics is based on the assumption of a quasi-static state. For structures with a sufficiently high stiffness, such as the gas turbine blades in the present work, this procedure is justified. The fatigue damage approach relies on the existence of a quasi-stable cyclic stress condition, which in general occurs for isotropic materials, as is the case for gas turbine blades. Practical implications Owing to the use of efficient analysis methods, a fast evaluation of the gas turbine blade within a stochastic analysis is feasible. Originality/value The fast numerical methods and the use of the full finite element model enable performing a structural analysis of any blade structure with a high quality of results.
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Naess, Arvid. "Statistical Analysis of Second-Order Response of Marine Structures." Journal of Ship Research 29, no. 04 (December 1, 1985): 270–84. http://dx.doi.org/10.5957/jsr.1985.29.4.270.
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A theoretical method is presented for estimating the response statistics of a marine structure that can be modeled as a second-order dynamic system subjected to a stationary, Gaussian sea. The method is particularly suitable for predicting extreme responses. The problem formulation expresses the response in terms of a second-order Volterra series, that is, including a linear and a quadratic term. For this response process the mean upcrossing frequency is found and asymptotic expressions are established that can be used to obtain closed-form solutions to the extreme-value problem.
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Devaraj, Deepa, R. Ramkrishnan, T. Prabu, Sreevalsa Kolathayar, and T. G. Sitharam. "Synthesis of Linear JTFA-Based Response Spectra for Structural Response and Seismic Reduction Measures for North-East India." Journal of Earthquake and Tsunami 14, no. 06 (August 8, 2020): 2050023. http://dx.doi.org/10.1142/s1793431120500232.
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North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0–480[Formula: see text]km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended.
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He, Fengxia, Zhong Luo, Lei Li, and Yongqiang Zhang. "A similitude for the middle-frequency vibration response of satellite solar array based on the wave coupling hybrid finite element–statistical energy analysis method." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 18 (April 8, 2020): 3560–70. http://dx.doi.org/10.1177/0954406220916491.
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A similitude is proposed for the dynamic response analysis of a satellite solar array. It is defined by invoking the wave coupling hybrid finite element–statistical energy analysis method which is considered as an effective way to solve the wide frequency (especially middle-frequency) vibration response of complex structures. The scaling laws are then derived by looking for equalities in the structural responses. A numerical case involving an assembly of two plates is discussed to verify the proposed scaling laws. Moreover, the new similitude is applied to a simplified satellite solar array model. If the analysis frequency step is selected appropriately, it is shown that a complete similitude can be defined: it allows predicting the vibration response of satellite solar array and provides the possibility for the model test of complex structures.
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Song, Jie, Zhi Gang Song, and Yi Jie Shen. "Analysis of RMS Acceleration Response Spectrum for Random Pedestrian Loads." Advanced Materials Research 261-263 (May 2011): 292–98. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.292.
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Pedestrian loads are affected by such uncertain parameters as walking step frequency, step length, dynamic load factors and phases of harmonic components, which lead to the uncertainties of structural response. A new method for calculation random response spectrum based on uniform design is introduced to reduce calculation work. A few representative samples of loads time histories are simulated using uniform design, and then the RMS acceleration response spectrums are obtained by dynamic time-history analysis of beam structures with different spans and damping ratios. The RMS acceleration response spectrums which have certain percentiles are obtained by reliability analysis based on response surface. Ultimately the general forms of RMS acceleration response spectrums are deduced from the analyses of sensitivities for damping ratio and span.
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Song, Danqing, Zhuo Chen, Lihu Dong, and Wencheng Zhu. "Numerical Investigation on Dynamic Response Characteristics and Deformation Mechanism of a Bedded Rock Mass Slope Subject to Earthquake Excitation." Applied Sciences 11, no. 15 (July 30, 2021): 7068. http://dx.doi.org/10.3390/app11157068.
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In order to systematically reveal the dynamic response characteristics of rock mass slopes subject to seismic excitation, time-domain and frequency-domain analyses are used to investigate the dynamic response of a bedded rock slope from multiple perspectives, using the two-dimensional numerical dynamic analyses. Based on the numerical simulation results, the influence of the weak bedded structural planes on the propagation characteristics of seismic waves in the slope is analyzed. The time-domain analysis suggests that the topographic and geological conditions have an influence on the dynamic response of the slope. The effects of ground motion direction on the dynamic response characteristics of the slope are identified. In addition, according to the frequency-domain analysis, the impacts of slope surface, elevation, and structural plane on the seismic response characteristics of the slope are also clarified. The intrinsic characteristics of the slope are investigated by using Fourier spectral analysis and modal analysis, and the deformation response characteristics of the slope are clarified. The relationship between different natural frequencies of the slope, the predominant frequency of the seismic wave, and the dynamic response characteristics of the slope is discussed. Moreover, the dynamic failure mechanism of the slope is analyzed. This work provides a reference for the seismic analysis of this type of slope.
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Zhang, Xiaolong, Bingchuan Duan, Chengzhi Wang, and Duoyin Wang. "Dynamic Response Analysis of Lateral Impact Force of Frame Wharf with Rock-Socketed Piles in Inland River Steel Sheath." Advances in Civil Engineering 2019 (December 6, 2019): 1–15. http://dx.doi.org/10.1155/2019/6918376.
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In this study, a three-dimensional finite element model was established to simulate the dynamic response of a large-scale steel-reinforced concrete composite high-pile wharf with a rock-socketed steel sheath. The model is based on the second phase of the Chongqing Orchard Harbor structure project in conjunction with the project “Research on the mechanism of interface damage and energy dissipation of the structure of the large-scale steel-reinforced concrete composite high-pile wharf in inland waters.” The stiffness of frame wharf is studied from the perspective of modal and transient dynamic analysis of structural dynamics. The distribution of the low-order modal frequency is more uniform. With the increase of the order, the modal frequency of the structure shows a periodical jump. The overall stiffness of the frame structure is larger with the steel sheath, and the longitudinal stiffness is less than the transverse stiffness. Under the action of transverse impact load, the members and joints of the steel-concrete structure exhibit synchronous mechanical response characteristics in the time domain. The peak values of displacement and stress of the structural joints occur 0.05 s after the peak value of the load-time history, and the peak value of reverse response of force occurs at 2.3 s, which is markedly smaller than the peak value of the response of load direction. Reducing the local positional stiffness of the load point is beneficial to improve the stress of the entire structure. The weak links of the frame structure appear at the joints of the members. Because of the hoop action of the steel sheath, the stress of the reinforced concrete pile core is more uniform. The peak value of the equivalent stress of the steel sheath member is generally larger than that of the reinforced concrete pile core, and the stress is highly concentrated at the joints of the steel tube longitudinal and transverse braces.
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Serafini, J., L. Greco, and M. Gennaretti. "Rotorcraft-pilot coupling analysis through state-space aerodynamic modelling." Aeronautical Journal 119, no. 1219 (September 2015): 1105–22. http://dx.doi.org/10.1017/s0001924000011155.
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AbstractThe terminology ‘rotorcraft-pilot coupling’ denotes phenomena arising from interaction between pilot and rotorcraft. Among these, the present work deals with ‘pilot-assisted oscillations’ that derive from unintentional pilot actions on controls due to seat vibrations, and are strictly related to rotor-aeroelasticity/airframe-structural-dynamics coupling, with involvement of blade control actuator dynamics. Focusing the attention on helicopters, a comprehensive rotorcraft model is developed and applied, with main rotor unsteady aerodynamics described in state-space form. This makes it particularly suited for stability and frequency-response analysis, as well as control applications. Numerical investigations address two critical rotorcraft-pilot coupling aeroelastic issues: stability of vertical bouncing and gust response in hovering. Results from main rotor unsteady aerodynamics modelling are compared with widely-used quasi-steady aerodynamics predictions. These suggest that, for accurate RPC/PAO phenomena predictions, mathematical modelling should include the three-dimensional, unsteady-flow effects, and that the pilot-in-the-loop passive behaviour produces a beneficial effect on the load factor generated by gust encountering.
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Wen, Ke Jie, Gui Lin Wang, and Fan Yang. "Model Identification and Dynamic Performance Analysis of Fast Tool Servo System with High Frequency Response." Advanced Materials Research 669 (March 2013): 273–78. http://dx.doi.org/10.4028/www.scientific.net/amr.669.273.
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Fast tool servo system could achieve precise and efficient processing of fine micro-structure for its fast and accuracy response to input control signal, which will directly affect the processing quality of the workpiece surface. Different structural forms of fast tool servo system have been designed and presented in China and overseas, with which generally low the stiffness and natural frequency, only can be used for the rule and the characteristic scale of the larger surface processing. A fast tool servo system whose thrust was up to 12500N, stiffness was 280N/μm, the natural frequency was more than 3kHz , was developed in this paper, as well as the analytical expression of time domain and frequency domain output，which were presented by the modeling analysis; The unknown parameters of the system model were identified by frequency response test. The theoretical and experimental results indicated that the system has good dynamic performance to meet the fine micro-structure of highly efficient, high-precision processing needs.
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Huang, Ziyuan, Jiancheng Fang, and Kun Wang. "Dynamics of flexible rotor-shaft assembly with consideration of contact behaviors." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 5 (June 12, 2014): 859–68. http://dx.doi.org/10.1177/0954406214539470.
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An approach is presented for large error problems of modal analysis of shaft assembly by considering contact behaviors of shaft components. The interference of shaft assembly is firstly calculated analytically through contact theory. The modal analysis of the finite element (FE) model of rotor-shaft assembly is executed by optimizing the normal contact stiffness factor (FKN). The accuracy of simulation results is verified in good agreement with experimental modal testing. The percentage errors of the first two bending natural frequencies are 1.3% and 2.8%, respectively. It is demonstrated that accurate mode of rotor-shaft assembly can be achieved. Then critical speeds of forward and backward are obtained by Campbell diagram. In particular, the amplitude-frequency response of rotor different element node under unbalanced vibration force is obtained by unbalance response analysis. It is important to improve the assembly’s structural integrity in order to minimize operational failure.
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Kim, Hyeung-Yun. "Structural Dynamic System Reconstruction Method for Vibrating Structures." Journal of Dynamic Systems, Measurement, and Control 125, no. 4 (December 1, 2003): 646–53. http://dx.doi.org/10.1115/1.1605992.
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To determine the natural frequencies and damping ratios of composite laminated plates, we present an efficient modal parameter estimation technique by developing a residual spectrum based structural dynamic system reconstruction. The modal parameters can be estimated from poles and residues of the system transfer functions derived from the state space system matrices. However, for modal parameter estimation of multivariable and higher order structural systems over broad frequency bands, this noniterative algorithm gives high accuracy in determining the natural frequencies and damping ratios. It is numerically well-behaved unlike iterative frequency-response-function (FRF) curve-fitting methods. We also discuss necessary conditions for convergence in Hankel norm and the error bounds of the approximated transfer function for the IDFT-based reconstruction system. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be identified from the eigenvalues of the structural dynamic system matrix derived by the reconstruction method from the experimental frequency response functions. These results are compared with those of finite-element analysis and single-degree-of-freedom curve-fitting.
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Liu, Zhihao, and Qinhe Gao. "In-plane vibration response of time and frequency domain with rigid-elastic coupled tire model with continuous sidewall." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 232, no. 4 (December 5, 2017): 429–45. http://dx.doi.org/10.1177/1464419317744681.
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The in-plane vibration characteristic of time and frequency domain for heavy-loaded radial tire with a larger flat ratio (close to 1) is researched by utilizing the rigid-elastic coupled tire model with continuous sidewall. The sidewall bending stiffness is considered and the flexible beam on the elastic continuous beam tire model is proposed and investigated analytically to simulate the in-plane vibration of the heavy-loaded radial tire within more wider frequency band. The rigid-elastic coupled tire model is derived with finite difference method and the analytical stiffness matrix; mass matrix is formed based on the geometrical and structural parameters of heavy-loaded radial tire. Structural parameters are identified utilizing genetic algorithm based on the error between the analytical and experimental modal frequency. In-plane frequency domain transfer function and time domain dynamics response of heavy-loaded radial tire is investigated and compared with the experimental result. Experimental and theoretical results show that in-plane rigid-elastic coupled tire model with sidewall bending stiffness can be used to precisely predict the transfer function and vibration feature within the frequency band of 300 Hz, compared with the tire model with the distributed independent sidewall element. The flexible beam on the elastic continuous beam tire model and rigid-elastic coupled tire model with continuous sidewall can be extended to the dynamic analysis of the tire with larger flat ratio or the tire under the impulsive loading conditions.
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Sparling, B. F., and L. D. Wegner. "Comparison of frequency- and time-domain analyses for guyed masts in turbulent winds." Canadian Journal of Civil Engineering 33, no. 2 (February 1, 2006): 169–82. http://dx.doi.org/10.1139/l05-101.
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Both frequency- and time-domain methods have been employed in the dynamic analysis of guyed telecommunication masts subjected to turbulent winds. Although the probabilistic frequency-domain approach offers some advantages in terms of its relative ease of implementation and in the statistical reliability of wind load descriptions, the deterministic time-domain method permits a more realistic treatment of system nonlinearities. In this study, a numerical investigation was undertaken to compare frequency- and time-domain dynamic response predictions for a selected guyed mast in gusty winds. Two different analysis techniques were employed, with the frequency-domain calculations performed using response influence lines and the time-domain analyses carried out using a stiffness-based finite element model. Good agreement was observed in root-mean-square and peak dynamic response estimates after compensation was included for differences in turbulence intensity levels assumed in the two models. In general, natural frequencies and mode shapes were also similar.Key words: guyed mast, dynamic analysis, wind, turbulence, nonlinear behaviour, finite element analysis, cables, frequency domain, time domain.
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Yang, Xiao-Mei, Chun-Xu Qu, Ting-Hua Yi, Hong-Nan Li, and Hua Liu. "Modal Analysis of a Bridge During High-Speed Train Passages by Enhanced Variational Mode Decomposition." International Journal of Structural Stability and Dynamics 20, no. 13 (July 6, 2020): 2041002. http://dx.doi.org/10.1142/s0219455420410023.
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Modal analysis of bridge under high-speed trains is essential to the design and health monitoring of bridge, but it is difficult to be implemented since the vehicle–bridge interaction (VBI) effect is involved. In this paper, the time–frequency analysis technique is performed on the non-stationary train-induced bridge responses to estimate the frequency variations. To suppress the interference terms in time–frequency analysis but preserve the time-variant characteristics of responses, the enhanced variational mode decomposition (VMD) is proposed, which is used to decompose the train-induced dynamic response into many of envelope-normalized intrinsic mode functions (IMFs). Then the short-time Fourier transform is applied to observe the time–frequency energy distribution of each IMF. The train-induced bridge signals measured from a large-scale high-speed railway bridge are analyzed in this paper. The IMFs associated with the pseudo-frequencies caused by train or the resonant frequencies of bridge are distinguished. And, frequency variations are captured from the time–frequency energy distributions of envelope-normalized IMFs. The results show the proposed method can extract the frequency variations of low-energy IMFs effectively, which are hard to be observed from the time–frequency energy distribution of train-induced bridge response. The instantaneous frequency characteristics extracted from the train-induced bridge response could be the important support for investigating the VBI effect of train–bridge system.
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Li, Xue-Qin, Guang-Chen Bai, Lu-Kai Song, and Wei Zhang. "Nonlinear Vibration Analysis for Stiffened Cylindrical Shells Subjected to Electromagnetic Environment." Shock and Vibration 2021 (July 19, 2021): 1–26. http://dx.doi.org/10.1155/2021/9983459.
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The nonlinear vibration behaviors of stiffened cylindrical shells under electromagnetic excitations, transverse excitations, and in-plane excitations are studied for the first time in this paper. Given the first-order shear deformation theory and Hamilton principle, the nonlinear partial differential governing equations of motion are derived with considering the von Karman geometric nonlinearity. By employing the Galerkin discretization procedure, the partial differential equations are diverted to a set of coupled nonlinear ordinary differential equations of motion. Based on the case of 1 : 2 internal resonance and principal resonance-1/2 subharmonic parametric resonance, the multiscale method of perturbation analysis is employed to precisely acquire the four-dimensional nonlinear averaged equations. From the resonant response analysis and nonlinear dynamic simulation, we discovered that the unstable regions of stiffened cylindrical shells can be narrowed by decreasing the external excitation or increasing the magnetic intensity, and their working frequency range can be expanded by reducing the in-plane excitation. Moreover, the different nonlinear dynamic responses of the stiffened cylindrical shell are acquired by controlling stiffener number, stiffener size, and aspect ratio. The presented approach in this paper can provide an efficient analytical framework for nonlinear dynamics theories of stiffened cylindrical shells and will shed light on complex structure design in vibration test engineering.
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Yao, Shou Wen, Jian Li Lv, and Qing Dong Peng. "Structural Dynamic Topology Optimization of the Transmission Housing." Advanced Materials Research 308-310 (August 2011): 368–72. http://dx.doi.org/10.4028/www.scientific.net/amr.308-310.368.
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Dynamic performance is one of the most important factors in the product’s life. Transmission housing is one of the important components in vehicle, which has direct influence on the vehicle’s powertrain performance. Dynamic topology optimization can improve the product’s performance. The dynamic topology model is built, in which the density of elements are the design variables, the displacement of frequency response and volume are the constraints, and the objective is to maximize the first natural frequency of the housing. According to the result of optimization, the CAD model of housing is rebuilt and the finite element analysis of the new housing is done.The results show that both the static and dynamic performance are improved besides the mass reduction, namely, dynamic topology optimization can significantly improve the product’s performance.
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Pong Sing, Chun, P. E. D. Love, and P. R. Davis. "Experimental study on condition assessment of reinforced concrete structure using a dynamics response approach." Structural Survey 32, no. 2 (May 6, 2014): 89–101. http://dx.doi.org/10.1108/ss-02-2013-0017.
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Purpose – Condition assessment on reinforced concrete (RC) structures is one of the critical issues as a result of structure degradation due to aging in many developed countries. The purpose of this paper is to examine the sensitivity and reliability of the conventional dynamic response approaches, which are currently applied in the RC structures. The key indicators include: natural frequency and damping ratio. To deal with the non-linear characteristics of RC, the concept of random decrement is applied to analyze time domain data and a non-linear damping curve could be constructed to reflect the condition of RC structure. Design/methodology/approach – A full-scale RC structure was tested under ambient vibration and the impact from a rubber hammer. Time history data were collected to analyze dynamics parameters such as natural frequency and damping ratio. Findings – The research demonstrated that the measured natural frequency is not a good indicator for integrity assessment. Similarly, it was revealed that the traditional theory of viscous damping performed poorly for the RC with non-linear characteristics. To address this problem, a non-linear curve is constructed using random decrement and it can be used to retrieve the condition of the RC structure in a scientific manner. Originality/value – The time domain analysis using random decrement can be used to construct a non-linear damping curve. The results from this study revealed that the damage of structure can be reflected from the changes in the damping curves. The non-linear damping curve is a powerful tool for assessing the health condition of RC structures in terms of sensitivity and reliability.
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Wu, Yimeng, Rui Zhu, Zhifu Cao, Ying Liu, and Dong Jiang. "Model Updating Using Frequency Response Functions Based on Sherman–Morrison Formula." Applied Sciences 10, no. 14 (July 20, 2020): 4985. http://dx.doi.org/10.3390/app10144985.
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Model updating plays an important role in dynamics modeling with high accuracy, which is widely used in mechanical engineering. In this paper, a model updating method using frequency response function (FRF) is proposed based on Sherman–Morrison formula, in which only the initial FRFs and parameter perturbations are employed to calculate the sensitivity avoiding repeated finite element (FE) analyses and improving the computational efficiency. Firstly, the sensitivity of FRFs to the design parameters is calculated by Sherman–Morrison formula based on the QR decomposition of the system dynamic stiffness matrix variation after parameter perturbations, then the influence of damping on the amplitude of FRFs is considered to select an appropriate frequency range, and finally conduct the model updating according to the sensitivity of the FRFs. By employing simulation examples of a truss and a solar wing and the experiment of an aluminum frame, the updating error is still within ±1.00% in the condition of 5% random white noise, which shows the proposed method has high accuracy and a certain anti-noise capability. When only a few numbers of frequency points are selected near the resonance peak of the FRFs, the result shows that selecting the appropriate frequency range and points can reduce the computational cost. The results of the experiment study show that the proposed method can effectively identify the structural parameters. The above results verify the feasibility and effectiveness of proposed model updating method using FRFs.
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Yuan, Xiaoming, Yue Tang, Weiqi Wang, and Lijie Zhang. "Parametric Vibration Analysis of a Six-Degree-of-Freedom Electro-Hydraulic Stewart Platform." Shock and Vibration 2021 (August 10, 2021): 1–27. http://dx.doi.org/10.1155/2021/9994786.
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Electro-hydraulic Stewart 6-DOF platform is a 6-DOF parallel mechanism combined with the electro-hydraulic servo control system, which is widely used in the field of construction machinery. In actual working conditions, the flow and pressure pulsation of the hydraulic oil output from the hydraulic leg of the electro-hydraulic Stewart platform are inevitable, so the equivalent stiffness of the platform leg will change, and the stiffness parameters of the transmission system will change, resulting in vibration, which will affect the accuracy of the platform. This paper considering the fluid unit equivalent stiffness cyclical fluctuations and leg, on the basis of the relationship between hydraulic stiffness, constructs the electric hydraulic Stewart platform machine vibration dynamics equation, fluid coupling parameters of vibration parameters using the method of the multiscale approximate analytic formula of the main resonance and combination resonance are derived, and the system parameters vibration time-domain response and frequency response under two different poses are discussed. Results show that the system first to six order natural frequency and the first to the sixth order natural frequency and frequency of hydraulic oil equivalent stiffness of the combination of frequency will have an effect on the parameters of the system vibration. In the main resonance, the dominant frequency is mainly the first to sixth order natural frequency of the system; in the combined resonance, the dominant frequency is the combined frequency. Through the parameter vibration analysis of two different positions of the platform, it is concluded that when the platform is in an asymmetric position, each leg of the system is more involved in vibration. This study can provide the reference for the subsequent dynamic optimization and reliability analysis of the electro-hydraulic Stewart platform.
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Dong, Hao, Libang Wang, Haoqin Zhang, and Xiao-long Zhao. "Nonlinear Frequency Response Analysis of Double-helical Gear Pair Based on the Incremental Harmonic Balance Method." Shock and Vibration 2021 (April 15, 2021): 1–20. http://dx.doi.org/10.1155/2021/6687467.
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The torsional dynamic model of double-helical gear pair considering time-varying meshing stiffness, constant backlash, dynamic backlash, static transmission error, and external dynamic excitation was established. The frequency response characteristics of the system under constant and dynamic backlashes were solved by the incremental harmonic balance method, and the results were further verified by the numerical integration method. At the same time, the influence of time-varying meshing stiffness, damping, static transmission error, and external load excitation on the amplitude frequency characteristics of the system was analyzed. The results show that there is not only main harmonic response but also superharmonic response in the system. The time-varying meshing stiffness and static transmission error can stimulate the amplitude frequency response of the system, while the damping can restrain the amplitude frequency response of the system. Changing the external load excitation has little effect on the amplitude frequency response state change of the system. Compared with the constant backlash, increasing the dynamic backlash amplitude can further control the nonlinear vibration of the gear system.
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Xu, Weizhi, Dongsheng Du, Shuguang Wang, and Weiwei Li. "A New Method to Calculate Additional Damping Ratio considering the Effect of Excitation Frequency." Advances in Civil Engineering 2020 (August 24, 2020): 1–15. http://dx.doi.org/10.1155/2020/3172982.
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The additional damping ratio (ADR) is an important indicator for evaluating the damping effect of structures with energy-dissipation devices. Most existing methods for determining the ADR require an analysis of the structural dynamic response and complex iterative calculations. An innovative simplified calculation method for determining the ADR of a structure supplemented by nonlinear viscous dampers is proposed. This method does not require the dynamic response of the structure to be calculated and only requires the structural characteristics, excitation frequency, and damper parameters. In this study, several typical calculation methods for the ADR were analysed. Then, a calculation formula for the ADR was derived with consideration of harmonic excitation under the condition where the excitation frequency is equal to the structural natural frequency, without calculation of the structural dynamic response or an iterative process. The effect of the excitation frequency on the calculated value of the ADR with different damping exponents was studied. Accordingly, the response spectrum average period (RSAP) was considered as the excitation period of ground motion to evaluate the excitation frequency, and a simplified calculation method for the ADR considering the effect of the excitation frequency characterised by the RSAP of the ground motion was established. Finally, the accuracy and effectiveness of the proposed method were verified by comparison with ADRs calculated using other methods.