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Journal articles on the topic 'Mode vibration cycle'
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1
Mroz, A., A. Orlowska, and J. Holnicki-Szulc. "Semi-Active Damping of Vibrations. Prestress Accumulation-Release Strategy Development." Shock and Vibration 17, no. 2 (2010): 123–36. http://dx.doi.org/10.1155/2010/126402.
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New method for semi-active control of vibrating structures is introduced. So-called Prestress Accumulation-Release (PAR) strategy aims at releasing of the strain energy accumulated in the structure during its deformation process. The strain energy is converted into kinetic energy of higher modes of vibration which is suppressed with structural damping or by means of a damping device. The adaptation process essentially affects the first mode vibrations by introducing an elastic force that opposes the movement. Numerical simulations as well as experimental results prove that the strategy can be very effective in mitigating of the fundamental mode of a free – vibrating structure. In a numerical example 95% of the vibration amplitude was mitigated after two cycles. An experimental demonstrator shows 85% reduction of the amplitude in a cantilever free- vibrations. In much more complex practical problems smaller portion of total energy can be released from the system in each cycle, nevertheless the strategy could be applied to mitigate the vibrations of, for example, pipeline systems or pedestrian walkways.
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Sun, Ying, and Yan Hong. "Analysis of Dynamic Performance of Air-Cooled Condenser Structure System." Applied Mechanics and Materials 170-173 (May 2012): 2675–80. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2675.
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In situ measurements on two power plants designed air-cooled condenser structure were described in this paper. Operating condition was divided into three types to test the structure system, and then obtaining the data of time-domain waveform and spectrum analysis in each condition. Cycle, frequency and vibration mode of the structure system were obtained by analyzing the data. Meanwhile, the structure was theoretically calculated using finite element program, gaining the cycle, frequency and vibration mode of the structure system. It was concluded that basic vibration mode of the structure system was space torsional vibration by comparison between theoretical values and measured values.
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Feng, Yang, Xiao Diao Huang, Jie Chen, and Rong Jing Hong. "A Novel Denoising Method Based on Ensemble Empirical Mode Decomposition – Principle Component Analysis." Applied Mechanics and Materials 668-669 (October 2014): 1157–61. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.1157.
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Equipment performance degradation model is a key component in its diagnosis and prognosis models. As to slewing bearing, vibration signals are usually non-stationary and with strong white noise, which makes it very difficult to extract useful information from the signals. Therefore, an Ensemble Empirical Mode Decomposition – Principle Component Analysis (EEMD - PCA) based method was proposed to denoise the vibration signals and performance degradation model was established by PCA. To verify the proposed method, an experiment was conducted and the life cycle vibration signals were acquired. After denoising, performance degradation model was established to explain the denoising performance. Results show that the proposed method acquired a better denoising performance than EEMD-MSPCA, which provides a potential for further research.
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Gordon Kirk, R., and Ali A. Alsaeed. "Induced Unbalance as a Method for Improving the Dynamic Stability of High-Speed Turbochargers." International Journal of Rotating Machinery 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/952869.
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The high-speed diesel engine turbocharger is known to have subsynchronous vibrations for a wide speed range. The bearing fluid-film instability is the main source of the vibration. The nonlinear forces inside the bearings are causing the rotor to whirl in a limit cycle. This study presents a new method for improving the dynamic stability by inducing the turbocharger rotor unbalance in order to suppress the subsynchronous vibration. The finite-element model of the turbocharger with floating-ring bearings is numerically solved for the nonlinear time-transient response. Both compressor and turbine added unbalance are induced and the dynamic stability is computed. The turbocharger model with linearized floating-ring bearings is also solved for eigenvalues to predict the modes of instability. The linear analysis demonstrates that the forward whirling mode of the floating-ring at the compressor end also becomes unstable at the higher turbocharger speeds, in addition to the unstable forward conical and cylindrical modes. The numerical predictions are also compared to the former experimental results of a similar turbocharger. The results of the study show that the subsynchronous frequency amplitude of the dominant first mode is reduced when inducing either the compressor or the turbine unbalance at a certain level.
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Reeves, M., N. Taylor, C. Edwards, D. Williams, and C. H. Buckberry. "A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 214, no. 3 (March 1, 2000): 285–96. http://dx.doi.org/10.1243/0954407001527420.
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The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.
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Fraas, Arthur P. "Using Vibrations in Fluidized Beds." Mechanical Engineering 120, no. 01 (January 1, 1998): 76–79. http://dx.doi.org/10.1115/1.1998-jan-7.
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This article focuses on processes that do not require a high flow rate of sweep gas; the complex-mode vibration-fluidized bed offers lower power needs, attrition rates, and elutriation rates than gas-fluidized beds or rotary kilns. The fluidized solids are induced to flow horizontally by inclining the trough and/or axis of vibration downward in the direction of solids flow. When viewing the operating region through a window in the side wall, the particles in the bed move in unison, like a column of marching soldiers. In light of the complexities and uncertainties in the interaction of adjacent particles in the fluidized bed, the dynamics of a single particle falling on a horizontal plate vibrating along a vertical axis should be considered first. Because the complex-mode vibration-fluidized bed can be tailored for certain applications, a number of projects are currently in the early stages of development. Promising uses include coal pyrolysis to produce fuel for gas turbines in combined-cycle power plants, the manufacture of char for superior activated carbon, recycled synthetic fiber in carpeting, and counterflow heat exchangers.
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Datta, Nabanita. "Vortex-induced vibration of a tension leg platform tendon: Multi-mode limit cycle oscillations." Journal of Marine Science and Application 16, no. 4 (November 20, 2017): 458–64. http://dx.doi.org/10.1007/s11804-017-1440-8.
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Basaran, C., and R. Chandaroy. "Nonlinear Dynamic Analysis of Surface Mount Interconnects: Part I—Theory." Journal of Electronic Packaging 121, no. 1 (March 1, 1999): 8–11. http://dx.doi.org/10.1115/1.2792663.
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Solder joints are commonly used in surface mount technology microelectronics packaging. It is well known that the dominant failure mode for solder joints is thermal fatigue. When semiconductor devices are used in a vibrating environment, such as in automotive and military applications, dynamic stresses contribute to the failure mechanism and in certain circumstances they can become the dominant failure cause. In this paper a unified constitutive model for Pb40/Sn60 solder joints is developed and then implemented in a finite element dynamic analysis procedure. The purpose of the material model and the implementation is to study the contribution of vibration induced strains to the fatigue life of solder interconnects in low cycle and high cycle fatigue. The proposed material model, which is based on the disturbed state concept (DSC), is used for a dynamic analysis of a solder joint in the following paper, Part II, Basaran and Chandaroy (1998).
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Mathison, R. M., M. G. Dunn, M. M. Weaver, and A. Dushko. "Measurement of Air Film Damping Effectiveness." Journal of Turbomachinery 127, no. 3 (March 1, 2004): 557–63. http://dx.doi.org/10.1115/1.1928288.
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Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.
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Witek, Lucjan. "Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance Conditions." Fatigue of Aircraft Structures 2011, no. 3 (August 1, 2011): 134–53. http://dx.doi.org/10.2478/v10164-010-0045-3.
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Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance ConditionsThis paper presents the results of a complex experimental and numerical crack initiation analysis of the helicopter turbo-engine compressor blades subjected to vibrations. A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects as well as those with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. The obtained results were next used as an input data into crack initiation (ε-N) analyses performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis, the different methods such as: Neuber elastic-plastic strain correction, linear damage summation and Palmgreen-Miner rule were utilized. As a result of ε-N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material were calculated using the Baumel-Seeger and Muralidharan methods. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of the work, the finite element results were compared with the results of experimental vibration HCF tests performed for the compressor blades.
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Song, M. T., D. Q. Cao, and W. D. Zhu. "Vortex-Induced Vibration of a Cable-Stayed Bridge." Shock and Vibration 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/1928086.
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The dynamic response of a cable-stayed bridge that consists of a simply supported four-cable-stayed deck beam and two rigid towers, subjected to a distributed vortex shedding force on the deck beam with a uniform rectangular cross section, is studied in this work. The cable-stayed bridge is modeled as a continuous system, and the distributed vortex shedding force on the deck beam is modeled using Ehsan-Scanlan’s model. Orthogonality conditions of exact mode shapes of the linearized undamped cable-stayed bridge model are employed to convert coupled governing partial differential equations of the original cable-stayed bridge model with damping to a set of ordinary differential equations by using Galerkin method. The dynamic response of the cable-stayed bridge is calculated using Runge-Kutta-Felhberg method in MATLAB for two cases with and without geometric nonlinear terms. Convergence of the dynamic response from Galerkin method is investigated. Numerical results show that the geometric nonlinearities of stay cables have significant influence on vortex-induced vibration of the cable-stayed bridge. There are different limit cycles in the case of neglecting the geometric nonlinear terms, and there are only one limit cycle and chaotic responses in the case of considering the geometric nonlinear terms.
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Wang, Zhu Lin, Yan Bo Zhu, and Qi Chang Li. "Equipment State New Indicators and Forecasting ARMA Mode." Advanced Materials Research 753-755 (August 2013): 2277–81. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.2277.
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The equipment storage condition monitoring technology research equipment equipment full life cycle environmental temperature and humidity, vibration impact stress and location information such as the attitude of the real-time data acquisition and processing analysis of equipment equipment maintenance and management is the effective supplement. Based on the equipment storage state information definition warning rate new indicators, and establish the ARMA forecasting model. performance is not the same as the state of the difference between the equipment equipment change maintenance and quality management plan.
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Zhang, Da Zhi, and Ling Qi Meng. "Research on Main Drive System Vibration of Six-Roller Wide Strip Aluminum Cold Rolling Mill." Applied Mechanics and Materials 644-650 (September 2014): 259–64. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.259.
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Vibration appears in the main drive system of the six-roller cold rolling mill of one plant. The oscillation frequency is 2.5 Hz. The oscillation cycle is 0.4 second. The oscillation period has nothing to do with the speed. Using the finite element software ANSYS, the low natural frequency is got through the modal analysis and harmonic response analysis based on the measured vibration data from the field. Horizontal vibration is the main vibration mode and it is the electromechanical coupling vibration. Main motor is controlled by IEGT inverter of TEMIC and the low frequency harmonic component is difficult to eliminate. AC drive trap filter is designed to dodge the 2.5 Hz frequency. The solution has achieved the recognition by the TEMIC company. The problem was solved and good results were obtained.
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Senthil Kumar, M., C. D. Naiju, S. J. Chethan Kumar, and Joseph Kurian. "Vibration Analysis and Improvement of a Vehicle Chassis Structure." Applied Mechanics and Materials 372 (August 2013): 528–32. http://dx.doi.org/10.4028/www.scientific.net/amm.372.528.
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Product development cycle time is very important in automotive industry which is very competitive nowerdays. New products are introduced into the market with better designs in short period of time by carrying out different engineering analysis. This study is focused on analyzing the existing chassis design and the noise, vibration and harshness(NVH) characteristics are studied. Modeling of chassis structure is carried out using 3D modelling package CATIA V5 and finite element model is created by meshing using Hypermesh software. The main objective is to find the natural frequency and analyse the mode shape of the automotive chassis structure. Results of the analysis will help to study the dynamic behavior of the chassis structure with load application/real road condition and to improvise the car chassis structure assembly.
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Du, Wenliao, Zhiyang Wang, Xiaoyun Gong, Liangwen Wang, and Guofu Luo. "Optimum IMFs Selection Based Envelope Analysis of Bearing Fault Diagnosis in Plunger Pump." Shock and Vibration 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/1248626.
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As the plunger pump always works in a complicated environment and the hydraulic cycle has an intrinsic fluid-structure interaction character, the fault information is submerged in the noise and the disturbance impact signals. For the fault diagnosis of the bearings in plunger pump, an optimum intrinsic mode functions (IMFs) selection based envelope analysis was proposed. Firstly, the Wigner-Ville distribution was calculated for the acquired vibration signals, and the resonance frequency brought on by fault was obtained. Secondly, the empirical mode decomposition (EMD) was employed for the vibration signal, and the optimum IMFs and the filter bandwidth were selected according to the Wigner-Ville distribution. Finally, the envelope analysis was utilized for the selected IMFs filtered by the band pass filter, and the fault type was recognized by compared with the bearing character frequencies. For the two modes, inner race fault and compound fault in the inner race and roller of rolling element bearing in plunger pump, the experiments show that a promising result is achieved.
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Eisinger, Frantisek L., and Robert E. Sullivan. "Vibration Fatigue of Centrifugal Fan Impeller Due to Structural-Acoustic Coupling and Its Prevention: A Case Study." Journal of Pressure Vessel Technology 129, no. 4 (October 25, 2006): 771–74. http://dx.doi.org/10.1115/1.2767371.
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Fatigue cracks from high cycle vibratory loading have developed in a centrifugal fan impeller after a relatively short period of operation. Based on vibration tests of the impeller and acoustic analysis of the internal spaces of the fan, structural-acoustic coupling with matching frequencies involving two-nodal diameter modes (structural and acoustic) was identified as the cause of the vibration problem. This paper gives a description of the problem and identifies available remedies for its elimination. Special attention is given in Case 1 to the acoustics of the system, where changes to the fan casing utilizing a decoupling acoustic chamber attached to the casing was investigated, and in Case 2, where changes needed to the structural characteristics of the impeller by utilizing a modified impeller with a substantially increased natural frequency (by 44%) of the two-nodal diameter vibratory mode shape were studied. Experimental tests confirmed that the structural-acoustic coupling and vibration were significantly reduced in Case 1 and were fully eliminated in Case 2.
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Xu, Fei, Chuanri Li, and Tongmin Jiang. "On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration." Shock and Vibration 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/5450865.
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Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR) mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF). A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD), probability density function (PDF), and loading cycle distribution (LCD) as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS) and the extreme response spectrum (ERS) and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response.
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Colding-Jorgensen, J. "Limit Cycle Vibration Analysis of a Long Rotating Cylinder Partially Filled With Liquid." Journal of Engineering for Gas Turbines and Power 113, no. 4 (October 1, 1991): 563–67. http://dx.doi.org/10.1115/1.2906278.
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The dynamics of a long, stiff cylinder, flexibly suspended at the ends, partially filled with liquid, is analyzed for varying rotating speed. It appears from the analysis that in the absence of external damping, two distinct speed ranges with unstable whirl are present, as opposed to one instability region for the short cylinder, which has been analyzed by a number of authors (Kuipers, 1964; Wolf, 1968). This is in agreement with field experience with centrifuges, where several regions of instability are often encountered, each corresponding to a particular vibration mode. The results should also apply to a jet engine with oil accidentally trapped in the rotor, or any hollow rotor with liquid trapped in the cavity. When external damping is applied the linear theory predicts the rotor to be unstable at all speeds (Kuipers, 1964). This is clearly not in accordance with field experience, and other authors have suggested different types of nonlinear analysis that can give finite amplitude stable whirl or pulsating whirl (Berman et al., 1985). In the present analysis a simplified nonlinear analysis known as the hydraulic jump approximation is applied in the two unstable speed ranges predicted by the linear theory, and a stable whirl finite amplitude, dependent on the external damping, follows. It is argued that the amplitudes found this way should always be higher than those predicted by a more sophisticated analysis, and also higher than the amplitudes measured by other authors, so that the procedure described should give a safe worst case prediction of rotor whirl amplitudes for a given external damping. Finally, an experimental setup intended to verify the analysis in a quantitative way is presented.
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Zhou, L., Y. H. Li, W. F. He, X. D. Wang, and Q. P. Li. "Laser Shock Processing of Ni-Base Superalloy and High Cycle Fatigue Properties." Materials Science Forum 697-698 (September 2011): 235–38. http://dx.doi.org/10.4028/www.scientific.net/msf.697-698.235.
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A plasma sound wave detection method of laser shock processing (LSP) technology is proposed. Speciments of Ni-base superalloy are used in this paper. A convergent lens is used to deliver 1.2 J, 10 ns laser pulses by a Q-switch Nd:YAG laser, operating at 1 Hz. The influence of the laser density to the shock wave is investigated in detail for two different wavelength lasers. Constant amplitude fatigue data are generated in room environment using notch specimens tested at an amplitude of vibration 2.8 mm and first-order flextensional mode. The results show that LSP is an effective surface treatment technique for improving the high cycle fatigue performance of Ni-base superalloys having a factor of 1.62 improvement in fatigue life.
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Prakash, Ravi, and Yogesh Mishra. "Analysis of Automobile Shaft for Optimizing Weight by Using Fem." SMART MOVES JOURNAL IJOSCIENCE 5, no. 10 (October 18, 2019): 24–35. http://dx.doi.org/10.24113/ijoscience.v5i10.229.
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Composites have been increasingly used in many engineering fields. Polymer composites are now widely used to build automotive components due to their exceptional rigidity and strength properties. Composite shafts for automotive applications are among the most recent research areas. A weight reduction can be achieved mainly with the introduction of a better material. The conventional system uses a metal shaft and has inherent limitations such as weight, corrosion, elasticity, vibration, storage and manufacturing problems increase with increasing shaft diameter. Advanced composites offer the opportunity to improve the transmission shaft by reducing weight, bearing load, misalignment and life cycle costs through the use of strategic materials, increasing the properties of resistance to fatigue, flexibility and vibration damping. The objective is the design and analysis of composite hollow shafts made of low density carbon fiber reinforced plastic (CFRP) for motor vehicles. And To investigate the vibrational effect of propeller shaft at different mode condition using FEA by ANSYS 18.2. In this result are the total weight of carbon fiber shaft is reduce. The total weight of the carbon fiber shaft is 2.6 kg is less then to previous material. And the previous study material of weight is 3.2kg.
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Ghaderi, Davood, Maryam Pourmahdavi, Vahid Samavatian, Omid Mir, and Majid Samavatian. "Combination of thermal cycling and vibration loading effects on the fatigue life of solder joints in a power module." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 9 (June 29, 2018): 1753–63. http://dx.doi.org/10.1177/1464420718780525.
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In this work, the combination of vibration loading and thermal cycle effects on the fatigue properties of a solder joint in a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) discrete was investigated. The fatigue mechanism under each loading mode was individually analyzed, and then according to the incremental damage superposition approach, the simultaneous effects were thoroughly studied. Under thermal cycling, the creep behavior of the solder is linked to the fatigue life. In fact, the creep accumulated strain in each thermal cycle has a straight relation to the failure time of solder joint. The origin of stress/strain in the assembly is owing to the sharp difference between coefficients of thermal expansions of the components in the electronic package. Regarding the vibration loading, the root mean square of peeling stress as a widely acceptable failure indicator was used to evaluate the vibration effects on the fatigue life. It is determined that the maximum stress is concentrated at the corner of solder layer. This result was similar to the outcomes of thermal cycling. The results also indicated that the combination of thermal and mechanical loadings accelerates the failure of the solder joint of the power MOSFET. Furthermore, the experimental and simulation studies showed similar results and approved the crack initiation at the corner of solder layer.
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Liu, C. H., C. Zang, F. Li, and E. P. Petrov. "High Frequency Modal Testing of the Multiblade Packets Using a Noncontact Measurement and Excitation System." Shock and Vibration 2020 (February 27, 2020): 1–12. http://dx.doi.org/10.1155/2020/8740941.
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High cycle failure of blades and vanes caused by the vibration is one of the major causes reducing the lifetime of turbomachines. For multiblade packets, the failure may occur at vibrations with high frequencies that can reach up to tens of kHz. The experimental modal testing of blades is crucial for the validation of numerical models and for the optimization of turbomachine design. In this paper, the test rig and procedure for measurements of dynamic characteristics of lightweight multiblade packets in wide and high frequency ranges are developed. The measurements are based on a noncontact excitation and noncontact measurement method, which allows the determination of the modal characteristics of the packets with high accuracy in wide frequency ranges. The responses of the multiblade packets are measured using a Scanning Laser Doppler Vibrometry (SLDV), while vibrations are excited by the acoustic excitation technique. Modal tests of the blade packet comprising 18 vane blades connected by shrouds are performed. The measurements are performed within the high frequency range of 0–30 kHz, and the natural frequencies and mode shapes are obtained for first 97 modes. To capture the complex high frequency blade mode shapes, each blade in the packet is scanned over 25 reference points uniformly distributed over the blade concave surface. In order to obtain the high frequency resolution, the frequency range used for the measurements is split into several frequency intervals accordingly to the number of spectral lines available in the used data acquisition system, and for each such interval, the test is performed separately. The finite model of the packet is created, and the numerical modal analysis is performed to compare the calculated natural frequencies and mode shapes with the experimental measurements. The comparison shows the satisfactory with those from finite element analysis. It illustrates the measurement method described in this work is effective and reliable.
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Xia, Huakang, Renwen Chen, Long Ren, and Qinbang Zhou. "Direct calculation of source impedance to adaptive maximum power point tracking for broadband vibration energy harvesting." Journal of Intelligent Material Systems and Structures 28, no. 9 (September 13, 2016): 1105–14. http://dx.doi.org/10.1177/1045389x16666178.
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This article presents an adaptive maximum power point tracking technique for broadband vibration energy harvesting. The presented technique employs a discontinuous conduction mode buck–boost converter to emulate a matched resistor for a vibration energy harvester. Instead of traversal search, the optimal duty cycle can be tuned in one step based on direct calculation of source impedance, which is realized by active pulse width modulation perturbation strategy; based on it, the circuit can work well in impedance match adaptively without any prior knowledge of a harvester. The prototype circuit is implemented by an ultra-low-power consumption MSP430 microcontroller with a stable external power supply. It produces 1.32 mW (0.4 g and 88.2 Hz acceleration) from a piezoelectric vibration energy harvester and 1.16 mW (0.12 g and 19.3 Hz acceleration) from an electromagnetic vibration energy harvester. According to the definition of power–bandwidth product, the experimental results achieve 75.2% and 39.9% of the theoretical optimal capacity of the piezoelectric vibration energy harvester and electromagnetic vibration energy harvester, respectively. The detailed experimental data indicate that the proposed approach achieves a large improvement than employing a fixed load resistance in a wide frequency band. Furthermore, the possibility of self-powered is confirmed based on a brief estimation of power losses on the proposed circuit.
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Zhao, Xiu Ting, and Jin Meng. "Three-Dimensional Finite Element Analysis Shelves." Applied Mechanics and Materials 117-119 (October 2011): 639–42. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.639.
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The use of Pro/E features a powerful solid modeling and ANSYS finite element analysis a powerful, integrated analysis of the two methods on the shelf for static analysis and modal analysis, obtained the stress, strain and natural frequency and the cloud vibration mode, the correct design of the shelf provides a reasonable theoretical basis. Checking the strength of the shelf structure can shorten the shelf of the production cycle, reduce costs and improve shelf quality, has a certain value engineering practice.
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Zhang, Mingming, Anping Hou, and Yadong Han. "Investigation on the Mechanism and Parametric Description of Non-Synchronous Blade Vibration." Entropy 23, no. 4 (March 24, 2021): 383. http://dx.doi.org/10.3390/e23040383.
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In order to explore the mechanism during the process of the non-synchronous vibration (NSV), the flow field formation development is investigated in this paper. Based on the fluid–structure interaction method, the vibration of rotor blades is found to be in the first bending mode with a non-integral order (4.6) of the rotation speed. Referring to the constant inter blade phase angle (IBPA), the appearances of frequency-locking and phase-locking can be identified for the NSV. A periodical instability flow emerges in the tip region with the mixture of separation vortex and tip leakage flow. Due to the nonlinearities of fluid and structure, the blade vibration exhibits a limit cycle oscillation (LCO) response. The separation vortex presenting a spiral structure propagates in the annulus, indicating a pattern as modal oscillation. A flow induced vibration is initiated by the spiral vortex in the tip. The large pressure oscillation caused by the movement of the spiral vortex is regarded as a main factor for the presented NSV. As the oscillation of blade loading occurs with blade rotating pass the disturbances, the intensity of the reverse leakage flow in adjacent channels also plays a crucial role in the blade vibration.
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Javanmardi, Ahad, Rouzbeh Abadi, Abdul Kadir Marsono, Masine Md Tap, Zulkepli Ibrahim, and Azhar Ahmad. "Correlation of Stiffness and Natural Frequency of Precast Frame System." Applied Mechanics and Materials 735 (February 2015): 141–44. http://dx.doi.org/10.4028/www.scientific.net/amm.735.141.
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The main objective of this study was to obtain the correlation between the severity of damage to the stiffness of the frame in the format of its intrinsic dynamic properties, the natural frequency of the structural system at damaged and undamaged state. In this research, a laboratory test was performed on the precast post-tension frame of a similar dimension and strength specification to Jabatan Kerja Raya (JKR) school buildings. The modal frame is a reduced in scale of 1 to 5 and subjected to cyclic lateral loadings and monitored its frequency through vibration test. The vibration test was performed at each end of the cycle of a lateral pushover test. The vibration data was recorded by accelerometers due to external forced vibration to assess its natural frequency, mode shapes and damping values of the system. This research found that there is a physical tangible relationship between natural frequency changes and stiffness in the frame. The results showed that as the severity of damage increases, the natural frequency of the frame decreases significantly, indicating that softening of the system that lead to a favorable ductility for earthquakes.
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Wanjara, P., J. Gholipour, E. Watanabe, K. Watanabe, T. Sugino, P. Patnaik, F. Sikan, and M. Brochu. "High Frequency Vibration Fatigue Behavior of Ti6Al4V Fabricated by Wire-Fed Electron Beam Additive Manufacturing Technology." Advances in Materials Science and Engineering 2020 (June 8, 2020): 1–14. http://dx.doi.org/10.1155/2020/1902567.
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Following foreign object damage (FOD), a decision to repair components using novel additive manufacturing (AM) technologies has good potential to enable cost-effective and efficient solutions for aircraft gas turbine engine maintenance. To implement any new technology in the gas turbine remanufacturing world, the performance of the repair must be developed and understood through careful consideration of the impact of service life-limiting factors on the structural integrity of the component. In modern gas turbine engines, high cycle fatigue (HCF) is one of the greatest causes of component failure. However, conventional uniaxial fatigue data is inadequate in representing the predominant HCF failure mode of gas turbine components that is caused by vibration. In this study, the vibratory fatigue behavior of Ti6Al4V deposited using wire-fed electron beam additive manufacturing (EBAM) was examined with the motivation of developing an advanced repair solution for fatigue critical cold-section parts, such as blades and vanes, in gas turbine engine applications. High cycle fatigue data, generated using a combination of step-testing procedure and vibration (resonance) fatigue testing, was analyzed through Dixon–Mood statistics to calculate the endurance limits and standard deviations of the EBAM and wrought Ti6Al4V materials. Also plots of stress (S) against the number of cycles to failure (N) were obtained for both materials. The average fatigue endurance limit of the EBAM Ti6Al4V was determined to be greater than the wrought counterpart. But the lower limit (95% reliability) of 426 MPa for the EBAM Ti6Al4V was lower than the value of 497 MPa determined for wrought Ti6Al4V and was attributed to the slightly higher data scatter–as reflected by the higher standard deviation–of the former material.
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Leng, Qiao Juan, Jiang Qian, and Yi Bin He. "Study on Damping of Reinforced Concrete Materials and Members." Key Engineering Materials 400-402 (October 2008): 257–62. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.257.
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According to the spatial distribution theory of damping energy dissipation, the calculation formula of damping energy dissipation and damping ratio of a cantilever beam in one cycle are derived. It is shown that the damping characteristic of a member is affected by the material damping characteristic, stiffness distribution, mode of vibration and the sectional shape of the member, etc. The damping energy dissipation coefficient J for reinforced concrete materials is calculated by using the proposed formula considering different concrete strength, elastic modulus and reinforcement ratios based on test data available.
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Li, Wenjie, and Shujin Laima. "Experimental Investigations on Nonlinear Flutter Behaviors of a Bridge Deck with Different Leading and Trailing Edges." Applied Sciences 10, no. 21 (November 3, 2020): 7781. http://dx.doi.org/10.3390/app10217781.
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Recently, the nonlinear flutter behavior of long-span suspension bridges has attracted attention. Unlike the classical theory of bridge flutter, the stable limit cycle oscillations (LCO) have occurred for some bluff aerodynamic configurations when the inflow velocity exceeded a specific critical value. To explore the influence of aerodynamic configurations on flutter behaviors a series of flutter tests for spring-suspended sectional models were conducted. When the leading edges and trailing edges with various shapes were installed at the sectional models, different flutter types occurred. In the test, the self-excited forces and flutter responses were measured. Then, the characteristics of coupling vibration and aerodynamic hysteresis of the two kinds of flutter were analyzed and compared. Finally, the role of the phase difference between self-excited forces and displacements was discussed in the mechanism difference of the classical flutter and the postflutter LCO. As the leading edge became the bluffer, the results showed that the type of flutter gradually transformed from classical divergent flutter to postcritical LCO and the torsional mode played a more important role in the flutter than in the vertical mode. For the postflutter LCO, there was a negative feedback pattern, i.e., as the vibration amplitude increased, the phase difference gradually decreased, and the energy input to the dynamic system did not grow rapidly, which limited the further vibration divergence and resulted in a stable LCO.
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Kang, J. "Dynamic surface characteristics during disc brake squeal: non-linear modelling and simulation." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 6 (April 20, 2011): 1341–48. http://dx.doi.org/10.1177/0954406211399332.
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This article studies the non-linear dynamic behaviour of a disc brake system during squealing induced by a disc doublet mode. The disc brake system is modelled as a rotating annular plate in contact with annular sector-friction material. In order to investigate the possibility of detachment over the contact area between the disc surface and friction material during squealing, the lift-off condition is applied to this model. Also, the non-linearity arising from the contact stiffness is considered on the basis of the load–deflection test for the friction material. Numerical results show that the vibration after the onset of squeal reaches the limit cycle. In the steady-squealing response, several interesting phenomena are observed: the stick-slip and lift-off over the specific regime of the contact area. It is shown that the dynamic surface pattern rotates due to the forward travelling wave of the squealing surface. However, the mark of the surface pattern does not seem to move because the speed of the travelling wave fluctuates at a double frequency of squeal vibration.
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Miyanawala, T. P., and R. K. Jaiman. "Decomposition of wake dynamics in fluid–structure interaction via low-dimensional models." Journal of Fluid Mechanics 867 (March 28, 2019): 723–64. http://dx.doi.org/10.1017/jfm.2019.140.
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We present a dynamic decomposition analysis of the wake flow in fluid–structure interaction (FSI) systems under both laminar and turbulent flow conditions. Of particular interest is to provide the significance of low-dimensional wake flow features and their interaction dynamics to sustain the free vibration of a square cylinder at a relatively low mass ratio. To obtain the high-dimensional data, we employ a body-conforming variational FSI solver based on the recently developed partitioned iterative scheme and the dynamic subgrid-scale turbulence model for a moderate Reynolds number ($Re$). The snapshot data from high-dimensional FSI simulations are projected to a low-dimensional subspace using the proper orthogonal decomposition (POD). We utilize each corresponding POD mode to detect features of the organized motions, namely, the vortex street, the shear layer and the near-wake bubble. We find that the vortex shedding modes contribute solely to the lift force, while the near-wake and shear layer modes play a dominant role in the drag force. We further examine the fundamental mechanism of this dynamical behaviour and propose a force decomposition technique via low-dimensional approximation. To elucidate the frequency lock-in, we systematically analyse the decomposed modes and their dynamical contributions to the force fluctuations for a range of reduced velocity at low Reynolds number laminar flow. These quantitative mode energy contributions demonstrate that the shear layer feeds the vorticity flux to the wake vortices and the near-wake bubble during the wake–body synchronization. Based on the decomposition of wake dynamics, we suggest an interaction cycle for the frequency lock-in during the wake–body interaction, which provides the interrelationship between the high-amplitude motion and the dominating wake features. Through our investigation of wake–body synchronization below critical $Re$ range, we discover that the bluff body can undergo a synchronized high-amplitude vibration due to flexibility-induced unsteadiness. Owing to the wake turbulence at a moderate Reynolds number of $Re=22\,000$, a distorted set of POD modes and the broadband energy distribution are observed, while the interaction cycle for the wake synchronization is found to be valid for the turbulent wake flow.
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Inalpolat, Murat, Enes Timur Ozdemir, Bahadir Sarikaya, and Hyun Ku Lee. "A multibody dynamic model for predicting operational load spectra of dual clutch transmissions." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 2 (August 1, 2021): 4132–43. http://dx.doi.org/10.3397/in-2021-2609.
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In this paper, a generalized nonlinear time-varying multibody dynamic model of dual clutch transmissions (DCT) is presented. The model consists of clutches, shafts, gears and synchronizers, and can be used to model any DCT architecture. A nonlinear clutch model is used to determine the transmitted power to the transmission at any speed and clutch temperature. The clutch can be a single- or multi-plate clutch and can operate in a wet or dry-clutch configuration. A combined kinematic and powerflow simulation enables calculation of gear, shaft, bearing and clutch quasi-static loads as well as gear mesh frequencies following a duty cycle as the input. For the corresponding Linear-Time-Invariant (LTI) system model, natural frequencies and mode shapes are obtained by solving the eigenvalue problem. The modal summation technique is used to determine the steady state forced vibration response of the system. For the corresponding NTV system, Newmark's time-step marching based integration is used to determine both the steady state and transient forced vibration response of the system. The DCT model is exercised using a common transmission architecture operating at several different operating conditions. The resulting impact of changing operational conditions on gear and bearing loads as well as dynamic transmission error spectra are demonstrated.
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Wu, Wei, and Jing Ji. "Simulation Analysis on Mechanics of Large-Span Enclosure Steel Structure Used in the Subway Station." Applied Mechanics and Materials 351-352 (August 2013): 38–41. http://dx.doi.org/10.4028/www.scientific.net/amm.351-352.38.
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This paper has carried out mechanics analysis of plane structure made of steel tube columns and the steel truss girder. Inner force analysis of steel tube column is gotten under vertical and horizontal load by adopting the theoretical calculation method. Using ANSYS software static and modal analysis of the truss girder is performed, and three order natural frequencies and vibration mode are obtained. It is verified for the rationality of the structure. At last the construction of node is given. The structure system has the advantages of simple construction and short cycle, so it can provide valuable reference for similar engineering.
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Nabatian, N., and N. W. Mureithi. "Lock-On Vortex Shedding Patterns and Bifurcation Analysis of the Forced Streamwise Oscillation of the Cylinder Wake." International Journal of Bifurcation and Chaos 25, no. 09 (August 2015): 1530022. http://dx.doi.org/10.1142/s0218127415300220.
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The two-dimensional numerical simulation of the flow over a cylinder forced to oscillate in the streamwise direction for Re = 200 is performed in CFX ANSYS. The controlled-vibration comprises of prescribed inline vibration from displacement amplitude-to-cylinder diameter A/D = 0.05 up to 0.5 with the excitation frequency ratios of 1, 1.5 and 2 including the harmonic and superharmonic excitation regions. The immersed boundary method is used to model the cylinder oscillation. Modal decomposition of the transverse velocity field via the proper orthogonal decomposition (POD) method is applied to uncover the interaction of symmetric and antisymmetric modes of the near wake. A model using the first two POD modes is developed based on symmetry group equivariance. The model predicts the mode interactions and bifurcated solution branches for all cases, and is shown to be in good agreement with numerical as well as previous experimental results. Lock-on is determined for a range of values of the oscillation amplitudes and frequency ratios. It is shown that the lock-on range widens with increasing nondimensional oscillation amplitude. The asymmetric 2S, P + S and symmetric pattern S with symbol S for a single vortex and P for a vortex pair shed per cycle, as well as a regime in which vortex formation is not synchronized with cylinder motion are observed in the cylinder wake depending on the combination of oscillation amplitude and frequency ratio. The frequency ratio variation from 1 to 2 leads to the switching from asymmetric to symmetric modes. The symmetric flow pattern corresponds to a near zero lift coefficient on the cylinder.
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Zhu, Shi Xing, Jian Li, and Bo Wang. "Research on Fuzzy Control of MR (Magneto-Rheological) Damper for Landing Gear Based on FuzzyTECH." Applied Mechanics and Materials 779 (July 2015): 212–19. http://dx.doi.org/10.4028/www.scientific.net/amm.779.212.
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The semi-active control of MR damper is established, using a simplified model of landing gear system and DSP2812 as the code control board. The fuzzy control system is created based on software fuzzyTECH and simulation mode was established in matlab\simulink. Compared with passive control, the fuzzy control damping effect of the aircraft body vertical acceleration, body relative displacement and wheel dynamic load at different moments in the process of plane's taking off and landing. Software fuzzyTECH platform can generate the corresponding code for the DSP controller, applied directly to the fuzzy control system design and debugging, and shorten the development cycle of fuzzy algorithm control. Passive control and fuzzy control test are carried out on the landing gear vibration test platform. The results show that the application of fuzzy algorithm controller has higher adaptability and more real-time control effect, fuzzy control is better than passive control.
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Xu, Kai Yan, De Min Wei, and Can Liu. "Nonlinear Earthquake-Response Analysis of Wuhan Junshan Yangtze River under Uniform and Non-Uniform Excitations." Applied Mechanics and Materials 105-107 (September 2011): 1220–24. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1220.
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Wuhan Junshan Yangtze River Bridge is an important traffic hinge on Jing-Zhu freeway, it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, the FEM model of it was established; the dynamic characteristic and nonlinear seismic responses under uniform and non-uniform excitations of it were systematic studied. The results show that: 1) the basic cycle of Wuhan Junshan Yangtze River Bridge is about 8.881s. Its first mode of vibration is longitudinal floating mode, which is favorable to the earthquake- response of structures. 2) Its former 40 rank frequency are located between 0.1~2Hz which is avail to the condition of traffic condition.3) the geometric nonlinearity has much influence on the response of this kind of bridge.4) the seismic responses are sensitive to the frequency spectra of the input earthquake wave. 5) The traveling wave excitations are unfavorable to the design of tower and the main girder when considering the three orthogonal seismic wave input. In order to get correct results, artificial seismic wave of the bridge address is necessary to the time-history analysis.
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HOROWITZ, M., and C. H. K. WILLIAMSON. "The effect of Reynolds number on the dynamics and wakes of freely rising and falling spheres." Journal of Fluid Mechanics 651 (March 29, 2010): 251–94. http://dx.doi.org/10.1017/s0022112009993934.
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In this paper, we study the effect of the Reynolds number (Re) on the dynamics and vortex formation modes of spheres rising or falling freely through a fluid (where Re = 100–15000). Since the oscillation of freely falling spheres was first reported by Newton (University of California Press, 3rd edn, 1726, translated in 1999), the fundamental question of whether a sphere will vibrate, as it rises or falls, has been the subject of a number of investigations, and it is clear that the mass ratio m* (defined as the relative density of the sphere compared to the fluid) is an important parameter to define when vibration occurs. Although all rising spheres (m* < 1) were previously found to oscillate, either chaotically or in a periodic zigzag motion or even to follow helical trajectories, there is no consensus regarding precise values of the mass ratio (m*crit) separating vibrating and rectilinear regimes. There is also a large scatter in measurements of sphere drag in both the vibrating and rectilinear regimes.In our experiments, we employ spheres with 133 combinations of m* and Re, to provide a comprehensive study of the sphere dynamics and vortex wakes occurring over a wide range of Reynolds numbers. We find that falling spheres (m* > 1) always move without vibration. However, in contrast with previous studies, we discover that a whole regime of buoyant spheres rise through a fluid without vibration. It is only when one passes below a critical value of the mass ratio, that the sphere suddenly begins to vibrate periodically and vigorously in a zigzag trajectory within a vertical plane. The critical mass is nearly constant over two ranges of Reynolds number (m*crit ≈ 0.4 for Re = 260–1550 and m*crit ≈ 0.6 for Re > 1550). We do not observe helical or spiral trajectories, or indeed chaotic types of trajectory, unless the experiments are conducted in disturbed background fluid. The wakes for spheres moving rectilinearly are comparable with wakes of non-vibrating spheres. We find that these wakes comprise single-sided and double-sided periodic sequences of vortex rings, which we define as the ‘R’ and ‘2R’ modes. However, in the zigzag regime, we discover a new ‘4R’ mode, in which four vortex rings are created per cycle of oscillation. We find a number of changes to occur at a Reynolds number of 1550, and we suggest the possibility of a resonance between the shear layer instability and the vortex shedding (loop) instability. From this study, ensuring minimal background disturbances, we have been able to present a new regime map of dynamics and vortex wake modes as a function of the mass ratio and Reynolds number {m*, Re}, as well as a reasonable collapse of the drag measurements, as a function of Re, onto principally two curves, one for the vibrating regime and one for the rectilinear trajectories.
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Wang, Gang, and Jinwei Shen. "Flutter instabilities of cantilevered piezoelectric pipe conveying fluid." Journal of Intelligent Material Systems and Structures 30, no. 4 (January 11, 2019): 606–17. http://dx.doi.org/10.1177/1045389x18818774.
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In this article, a nonlinear model was developed for a cantilevered piezoelectric pipe conveying fluid that included geometric nonlinearity and electromechanical coupling. The Galerkin method discretized the system in order to characterize its behavior. Critical flutter velocity and its associated unstable mode can be determined based on linear analysis. Due to the presence of piezoelectric materials, the critical flutter velocity depends on the resistive piezoelectric damping and electromechanical coupling. This added resistive piezoelectric damping tends to decrease the flutter velocity. Comprehensive simulations were also conducted to characterize the post-flutter behaviors. System parameters including amplitude, deformed pipe shape, and collected voltage in piezoelectric materials were calculated. The system will undergo limited cycle oscillation when the fluid velocity passes the flutter velocity. Parametric studies were conducted as well to investigate the system responses under different flow velocities. Physical insights can be collected from these simulation results to conduct piezoelectric pipe design and performance predictions for future pipe vibration control and energy harvesting applications.
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Nakamura, Izumi, Akihito Otani, and Masaki Shiratori. "Failure Behavior of Piping Systems With Wall Thinning Under Seismic Loading." Journal of Pressure Vessel Technology 126, no. 1 (February 1, 2004): 85–90. http://dx.doi.org/10.1115/1.1638787.
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Shaking table tests of three-dimensional piping models with degradation were conducted in order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems. The degradation condition induced in the piping models was about 50 percent full circumferential wall thinning at elbows. Four types of models were made for the shaking table tests by varying the location of wall thinning in the piping models. These models were excited under the same input acceleration until the models failed and a leak of pressurized internal water occurred. Through these tests, the change of the vibration characteristics and processes to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and the damage was concentrated on the weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.
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Elahi, Hassan, Marco Eugeni, Federico Fune, Luca Lampani, Franco Mastroddi, Giovanni Paolo Romano, and Paolo Gaudenzi. "Performance Evaluation of a Piezoelectric Energy Harvester Based on Flag-Flutter." Micromachines 11, no. 10 (October 14, 2020): 933. http://dx.doi.org/10.3390/mi11100933.
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In the last few decades, piezoelectric (PZT) materials have played a vital role in the aerospace industry because of their energy harvesting capability. PZT energy harvesters (PEH) absorb the energy from an operational environment and can transform it into useful energy to drive nano/micro-electronic components. In this research work, a PEH based on the flag-flutter mechanism is presented. This mechanism is based on fluid-structure interaction (FSI). The flag is subjected to the axial airflow in the subsonic wind tunnel. The performance evaluation of the harvester and aeroelastic analysis is investigated numerically and experimentally. A novel solution is presented to extract energy from Limit Cycle Oscillations (LCOs) phenomenon by means of PZT transduction. The PZT patch absorbs the flow-induced structural vibrations and transforms it into electrical energy. Furthermore, the optimal resistance and length of the flag is predicted to maximize the energy harvesting. Different configurations of flag i.e., with Aluminium (Al) patch and PZT patch for flutter mode vibration mode are studied numerically and experimentally. The bifurcation diagram is constructed for the experimental campaign for the flutter instability of a cantilevered flag in subsonic wind-tunnel. Moreover, the flutter boundary conditions are analysed for reduced critical velocity and frequency. The designed PZT energy harvester via flag-flutter mechanism is suitable for energy harvesting in aerospace engineering applications to drive wireless sensors. The maximum output power that can be generated from the designed harvester is 6.72 mW and the optimal resistance is predicted to be 0.33 MΩ.
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Yao, Rong Qing. "Research on an Algorithm and System for Estimation of Instantaneous Frequency of Rotating Machinery." Advanced Materials Research 452-453 (January 2012): 153–59. http://dx.doi.org/10.4028/www.scientific.net/amr.452-453.153.
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Instantaneous frequency is an import parameter to diagnose faults of rotating machinery. This paper puts forward an algorithm based Hilbert-Huang Transformation (HHT) to estimate the instantaneous frequency of rotating machinery and develops an instantaneous cymometer based embedded system technology. In order to estimate instantaneous frequency of rotating machinery, the vibration signal is decomposed into a series of intrinsic mode functions (IMF) first by the method of empirical mode decomposition (EMD), then one of the intrinsic mode functions is analyzed with the Hilbert transformation to acquire an estimate value of instantaneous frequency. An instantaneous cymometer is also described in this paper, which is designed to measure the average frequency and instantaneous frequency of rotating machinery in real time. The average frequency is acquired from measuring the cycle of key-phase signal, and the instantaneous frequency is from the above-mentioned method based HHT. The instantaneous cymometer is consisted of an embedded system, which is connected to a PC with an Ethernet. The embedded system is based on an ARM chip (Samsung S3C4510) A/D conversion, EMD and Hilbert transform are completed on the embedded system, and then the results are compressed and sent to the PC by TCP/IP.
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Ouakad, Hassen M., Fehmi Najar, and Oussama Hattab. "Nonlinear Analysis of Electrically Actuated Carbon Nanotube Resonator Using a Novel Discretization Technique." Mathematical Problems in Engineering 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/517695.
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Static as well as dynamic analyses have been performed on clamped-clamped carbon nanotube (CNT) resonator. The nonlinear CNT model is investigated with a novel discretization technique: a differential quadrature method (DQM) to discretize the spatial variables and a finite difference method (FDM) for limit-cycle solutions. Parametric study is performed by varying the electric load, as well as the initial curvature (due to fabrication). It is found that the pull-in voltage decreases nonlinearly with initial curvature and linearly with residual stresses. The eigenvalue problem is also solved to obtain the bending natural frequencies of the system as function of the DC voltage as well as the initial curvature of the CNT. Frequency-response curves near some selected resonant frequencies are plotted to better understand the nanotubes' dynamic behavior. Different linear and nonlinear phenomena are depicted such as dynamic pull-in, hardening, and softening behavior and veering of the odd modes. We have found that even when exciting the CNT near its first natural frequency, the vibration mode located at the veering process significantly alters the CNT's motion and hence may decrease its overall quality factor.
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Gai, Jingbo, Yifan Hu, and Junxian Shen. "A Bearing Performance Degradation Modeling Method Based on EMD-SVD and Fuzzy Neural Network." Shock and Vibration 2019 (March 7, 2019): 1–10. http://dx.doi.org/10.1155/2019/5738465.
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Bearing performance degradation assessment has great significance to condition-based maintenance (CBM). A novel degradation modeling method based on EMD-SVD and fuzzy neural network (FNN) was proposed to identify and evaluate the degradation process of bearings in the whole life cycle accurately. Firstly, the vibration signals of bearings in known states were decomposed by empirical mode decomposition (EMD) to obtain the intrinsic mode functions (IMFs) containing feature information. Then, the selected key IMFs which contain the main features were decomposed by singular value decomposition (SVD). And the decomposed results were used as the training samples of FNN. At last, the output results of the tested data were normalized to the health index (HI) through learning and training of FNN, and then the performance degradation degree could be described by the distance between the test sample and the normal one. According to the case study, this modeling method could evaluate the performance degradation of bearings effectively and identify the early fault features accurately. This method also provided an important maintenance strategy for the CBM of bearings.
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Xu, Kai Yan. "Earthquake-Response Analysis of Long-Span Cable-Stayed Bridge under Uniform and Non-Uniform Excitations." Applied Mechanics and Materials 574 (July 2014): 36–40. http://dx.doi.org/10.4028/www.scientific.net/amm.574.36.
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Earthquake is a kind of natural disaster which is difficult to predict and the damage degree is very great, occurrence of the strong motion often leads to the tremendous life and property loss. Bridge is very important lifeline engineering and it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, the FEM model of a long-span cable-bridge was established; the dynamic characteristic and nonlinear seismic responses under uniform and non-uniform excitations of it were systematic studied. The results show that: 1) the basic cycle of it is about 8.881s. Its first mode of vibration is longitudinal floating mode, which is favorable to the earthquake-response of structures. 2) Its former 40 rank frequency are located between 0.1~2Hz which is avail to the condition of traffic condition.3) the geometric nonlinearity has much influence on the response of this kind of bridge.4) the seismic responses are sensitive to the frequency spectra of the input earthquake wave. 5) The traveling wave excitations are unfavorable to the design of tower and the main girder when considering the three orthogonal seismic wave input. In order to get correct results, artificial seismic wave of the bridge address is necessary to the time-history analysis.
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Huang, Bo Wun, Jung Ge Tseng, and Y. L. Ke. "Dynamic Response of a Viscoelastic Damping Isolator under High Cyclic Loading." Applied Mechanics and Materials 479-480 (December 2013): 244–48. http://dx.doi.org/10.4028/www.scientific.net/amm.479-480.244.
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Viscoelastic damping isolator (VDI) is a new way to reduce the vibration of punch press in automobiles, motorcycles, IT, aerospace, mold and other industries. It not only reduces the vibration of large punching machine and equipment, but also decreases its maintenance costs and avoids endangering the surrounding environment. VDI is composed of partitions, damping fluid, steel springs and level adjusters. Different number of the partitions are welded on upper and lower rectangular steel plates, respectively. Steel springs are placed at the edges between the plates to support up to 150 tons of weight of the punch press. Screw level adjusters are place between lower and thick bottom plates to adjust the horizontal level of the isolator. The damping fluid is filled in the space between interlacing partitions approximate 60% of the height of the composed isolator. The impact energy produced by the presser is dissipated by shear deformation between the damping fluid and partitions. This article used 3D graphing software and finite element method (FEM) to investigate the dynamic characteristic of the damping isolator after impacted by the puncher. The normal mode analysis of the VDI is obtained. The isolator is settled within 0.3 seconds after 300,000 N shock impact and satisfies industrial specification of large punchers with loading frequency of 100 cycle/min.
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Ren, Xiu Hong, and Ying Ying Tan. "Research Progress of Diffusion Absorption Refrigeration Technology." Applied Mechanics and Materials 238 (November 2012): 209–13. http://dx.doi.org/10.4028/www.scientific.net/amm.238.209.
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Compared with the gas-compressed refrigeration system, the diffusion absorption refrigeration cycle has no moving part and the associated noise and vibration. It can be operated without any electric input and driven by various energy sources, has no the problem of the substitute of CFC, furthermore it has positive significance in energy conservation, off peak, environmental protection, and promoting the use of gas. So it has broad application prospects as a kind of absorption refrigeration mode. In the development of diffusion absorption refrigeration technology, the performance of diffusion absorption refrigeration system has been improved and enhanced continuously. The paper presents and discusses the recent research progress of diffusion absorption refrigeration which contains design of bubble pump, adjustment and optimization of operation parameters, utilization of low-grade thermal energy and selection of working medium. The research direction of diffusion absorption refrigeration in the future is suggested.
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Juan Du, Juan Du, and Takayoshi Kobayashi Takayoshi Kobayashi. "Real-time vibrational mode-coupling observed using a few-cycle pulse laser." Chinese Optics Letters 9, s1 (2011): s10601–310603. http://dx.doi.org/10.3788/col201109.s10601.
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Rajamuni, Methma M., Mark C. Thompson, and Kerry Hourigan. "Transverse flow-induced vibrations of a sphere." Journal of Fluid Mechanics 837 (January 5, 2018): 931–66. http://dx.doi.org/10.1017/jfm.2017.881.
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Flow-induced vibration of an elastically mounted sphere was investigated computationally for the classic case where the sphere motion was constrained to move in a direction transverse to the free stream. This study, therefore, provides additional insight into, and comparison with, corresponding experimental studies of transverse motion, and distinction from numerical and experimental studies with specific constraints such as tethering (Williamson & Govardhan, J. Fluids Struct., vol. 11, 1997, pp. 293–305) or motion in all three directions (Behara et al., J. Fluid Mech., vol. 686, 2011, pp. 426–450). Two sets of simulations were conducted by fixing the Reynolds number at $Re=300$ or 800 over the reduced velocity ranges $3.5\leqslant U^{\ast }\leqslant 100$ and $3\leqslant U^{\ast }\leqslant 50$ respectively. The reduced mass of the sphere was kept constant at $m_{r}=1.5$ for both sets. The flow satisfied the incompressible Navier–Stokes equations, while the coupled sphere motion was modelled by a spring–mass–damper system, with damping set to zero. The sphere showed a highly periodic large-amplitude vortex-induced vibration response over a lower reduced velocity range at both Reynolds numbers considered. This response was designated as branch A, rather than the initial/upper or mode I/II branch, in order to allow it to be discussed independently from the observed experimental response at higher Reynolds numbers which shows both similarities and differences. At $Re=300$, it occurred over the range $5.5\leqslant U^{\ast }\leqslant 10$, with a maximum oscillation amplitude of ${\approx}0.4D$. On increasing the Reynolds number to 800, this branch widened to cover the range $4.5\leqslant U^{\ast }\leqslant 13$ and the oscillation amplitude increased (maximum amplitude ${\approx}0.6D$). In terms of wake dynamics, within this response branch, two streets of interlaced hairpin-type vortex loops were formed behind the sphere. The upper and lower sets of vortex loops were disconnected, as were their accompanying tails. The wake maintained symmetry relative to the plane defined by the streamwise and sphere motion directions. The topology of this wake structure was analogous to that seen experimentally at higher Reynolds numbers by Govardhan & Williamson (J. Fluid Mech., vol. 531, 2005, pp. 11–47). At even higher reduced velocities, the sphere showed distinct oscillatory behaviour at both Reynolds numbers examined. At $Re=300$, small but non-negligible oscillations were found to occur (amplitude of ${\approx}0.05D$) within the reduced velocity ranges $13\leqslant U^{\ast }\leqslant 16$ and $26\leqslant U^{\ast }\leqslant 100$, named branch B and branch C respectively. Moreover, within these reduced velocity ranges, the centre of motion of the sphere shifted from its static position. In contrast, at $Re=800$, the sphere showed an aperiodic intermittent mode IV vibration state immediately beyond branch A, for $U^{\ast }\geqslant 14$. This vibration state was designated as the intermittent branch. Interestingly, the dominant frequency of the sphere vibration was close to the natural frequency of the system, as observed by Jauvtis et al. (J. Fluids Struct., vol. 15(3), 2001, pp. 555–563) in higher-mass-ratio higher-Reynolds-number experiments. The oscillation amplitude increased as the reduced velocity increased and reached a value of ${\approx}0.9D$ at $U^{\ast }=50$. The wake was irregular, with multiple vortex shedding cycles during each cycle of sphere oscillation.
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Brassitos, Elias, and Nader Jalili. "Dynamics of integrated planetary geared bearings." Journal of Vibration and Control 26, no. 7-8 (January 14, 2020): 565–80. http://dx.doi.org/10.1177/1077546319889848.
Full textAbstract:
The gear bearing drive is a new robotic transmission that was developed by NASA for compact and lightweight robotic applications. Compared to conventional simple and compounded planetary gear trains, the mechanical assembly of the gear bearing drive does not require a planetary carrier and individual planet needle bearings to maintain the gearset alignment. Instead, the design integrates the gearing and bearing functions together such that a constant pressure angle is maintained throughout the mesh cycle by the use of cylindrical rollers that are mounted parallel to the gear mesh. This paper examines the vibration characteristics of this planetary architecture and extracts its natural frequencies and mode shapes using both analytic and finite element methods. The design is compared against a conventional system with a floating carrier for comparative analysis. A simple and systematic approach to analytically and numerically solve the dynamics of complex, multi degree of freedom gear train systems using MATLAB is presented that can be easily applied to study other complex non-linear dynamic systems.
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Cranfield, R. R. "Studies of Power Station Feed Pump Loss of Suction Pressure Incidents." Journal of Fluids Engineering 110, no. 4 (December 1, 1988): 453–61. http://dx.doi.org/10.1115/1.3243577.
Full textAbstract:
Open cycle feed systems featuring a deaerator followed by the boiler feed pumps have been subject to unexpected loss in net positive suction head during transient operation. This has been traced to separation at the deaerator storage tank drain and the formation of a steam/water interface in the downcomer to the pumps. The outflow at separation when the storage tank water is subcooled is generally much greater than the maximum suction flow corresponding to the unit rating, but when the tank water boils, as during transients, it may be very much less. Thus with a high suction flow in the boiling mode, the new interface may descend in the downcomer to result in feed pump cavitation, pressure imbalance, vapor locking, severe vibration, damage to the pump and an inability to maintain forward flow. Model tests have been conducted to establish the criterion for the separation in terms of the critical outflow for specific operating conditions as a function of geometric ratios involving tank-water depth and tank/downcomer dimensions. The data obtained although scattered are in general agreement with the data from actual plant and may be used to assess safe operating parameters.