Response Characteristics of a Linear Rotorcraft Vibration Model
NASA Technical Reports Server (NTRS)
Kunz, Donald L.
1982-01-01
A fully coupled vibration model, consisting of a rotor with only flapping degrees of freedom plus pylon and fuselage pitching motion, was used in a parametric study undertaken to investigate the response characteristics of a simplified helicopter. Among the parameters studied were uncoupled body frequency, blade stiffness, hinge offset, advance ratio, and mast height. Results from the harmonic balance solution of the equations of motion show how each of these quantities affects the response of the model. The results also indicate that there is a potential for reducing vibration response through the judicious definition of the design parameters.
Significant characteristics of social response to noise and vibration
NASA Technical Reports Server (NTRS)
Nishinomiya, G.
1979-01-01
Several surveys made since 1971 to investigate annoyance resulting from noise and vibration, from various sources were studied in order to quantify the relation between annoyance response to noise or vibration and properties of the respondent including factors such as noise exposure, etc. Samples collected by the social surveys and physical measurements were analyzed by multi-dimensional analysis.
Vibration Response of Airplane Structures
NASA Technical Reports Server (NTRS)
Theodorsen, Theodore; Gelalles, A G
1935-01-01
This report presents test results of experiments on the vibration-response characteristics of airplane structures on the ground and in flight. It also gives details regarding the construction and operation of vibration instruments developed by the National Advisory Committee for Aeronautics.
Vibration Characteristics of Thermoplastic Composite
NASA Astrophysics Data System (ADS)
Haldar, Amit Kumar; Singh, Satnam; Prince
2011-12-01
Unreinforced, Long fiber and Short fiber polypropylene composites are being used in many antivibration applications, due to their time and temperature dependent specific mechanical properties. Their good damping behavior accounts for many engineering applications. For utilization of these materials in specific engineering applications, there is a need to understand the damping behavior of composites under dynamic load. For this work, unreinforced and 20% long and short reinforced glass fiber polypropylene composite materials were tested for forced transverse vibration damping characteristics under static as well as fatigue loading conditions. The damping characteristics are quantified by forced frequency response of the test material. Presence of reinforced fibers increases the damping capacity. Among reinforcements, short fiber reinforced polypropylene shows increased damping capacity then long glass fiber reinforced. The Publisher is retracting this article from the scientific record due to the verbatim use of content without proper crediting.
NASA Technical Reports Server (NTRS)
Bowman, L. M.
1986-01-01
Dynamic behaviors of structures analyzed interactively. Interactive steadystate vibration-response program, VIBRA, developed. Frequency-response analyses commonly used in evaluating dynamic behaviors of structures subjected to cyclic external forces. VIBRA calculates frequency response using modalsuperposition approach. Method applicable to single or multiple forces applied to linear, proportionally damped structure in which damping is viscous or structural. VIBRA written in FORTRAN 77 for interactive execution.
NASA Astrophysics Data System (ADS)
Ainalis, Daniel; Rouillard, Vincent; Sek, Michael
2016-06-01
This paper describes the application of a practical analytical technique based on the random decrement method to estimate the rigid sprung mass dynamic characteristics (frequency response function) of road vehicles using only vibration response data during constant-speed operation. A brief history and development of the random decrement technique is presented, along with a summary of work undertaken on optimal parameter selection to establish the random decrement signature. Two approaches to estimate the dynamic characteristics from the random decrement signature are described and evaluated. A custom, single-wheeled vehicle (physical quarter car) was commissioned to undertake a series of on-the-road experiments at various nominally constant operating speeds. The vehicle, also instrumented as an inertial profilometer, simultaneously measured the longitudinal pavement profile to establish the vehicle's actual dynamic characteristics during operation. The main outcome of the paper is that the random decrement technique can be used to provide accurate estimates of the sprung mass mode of the vehicle's dynamic characteristics for both linear and nonlinear suspension systems of an idealised vehicle.
NASA Technical Reports Server (NTRS)
August, Richard; Kaza, Krishna Rao V.
1988-01-01
An investigation of the vibration, performance, flutter, and forced response of the large-scale propfan, SR7L, and its aeroelastic model, SR7A, has been performed by applying available structural and aeroelastic analytical codes and then correlating measured and calculated results. Finite element models of the blades were used to obtain modal frequencies, displacements, stresses and strains. These values were then used in conjunction with a 3-D, unsteady, lifting surface aerodynamic theory for the subsequent aeroelastic analyses of the blades. The agreement between measured and calculated frequencies and mode shapes for both models is very good. Calculated power coefficients correlate well with those measured for low advance ratios. Flutter results show that both propfans are stable at their respective design points. There is also good agreement between calculated and measured blade vibratory strains due to excitation resulting from yawed flow for the SR7A propfan. The similarity of structural and aeroelastic results show that the SR7A propfan simulates the SR7L characteristics.
Vibration response of misaligned rotors
NASA Astrophysics Data System (ADS)
Patel, Tejas H.; Darpe, Ashish K.
2009-08-01
Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.
Non-Linear Vibration Characteristics of Clamped Laminated Shallow Shells
NASA Astrophysics Data System (ADS)
ABE, A.; KOBAYASHI, Y.; YAMADA, G.
2000-07-01
This paper examines non-linear free vibration characteristics of first and second vibration modes of laminated shallow shells with rigidly clamped edges. Non-linear equations of motion for the shells based on the first order shear deformation and classical shell theories are derived by means of Hamilton's principle. We apply Galerkin's procedure to the equations of motion in which eigenvectors for first and second modes of linear vibration obtained by the Ritz method are employed as trial functions. Then simultaneous non-linear ordinary differential equations are derived in terms of amplitudes of the first and second vibration modes. Backbone curves for the first and second vibration modes are solved numerically by the Gauss-Legendre integration method and the shooting method respectively. The effects of lamination sequences and transverse shear deformation on the behavior are discussed. It is also shown that the motion of the first vibration mode affects the response for the second vibration mode.
Vibrational characteristics of harp soundboards.
Waltham, Chris; Kotlicki, Andrzej
2008-09-01
Harps exist in different forms, from large factory-made concert harps to small hand-made folk harps. This variety presents both a challenge and an opportunity for acousticians. The musical quality of a harp depends on many factors, but key among these is the soundboard. This work sets out to define some general desirable qualities of a harp soundboard. First, in order to understand the relationship between the vibrational behavior of a bare soundboard and that of a completed instrument, a 36-string harp was built from scratch. Measurements were made at each stage of construction, and the results showed how the bare soundboard properties affect those of the finished harp. Second, the soundboards of several harps of different sizes were assessed by measuring the admittances along the string bar. These data showed that one relationship crucial to the quality of the soundboard is that between the modal shapes and modal frequencies of the soundboard, and the position and fundamental frequencies of the strings attached to it. A general statement is made about this relationship, one which should be of use to harp makers. PMID:19045667
Frequency characteristics of electro-hydraulic vibrator.
Satoh, Noriaki
2002-12-01
Frequency characteristics of an electro-hydraulic vibrator were measured using two kinds of test signals. First, sine signals had theoretically 1.0 m/s2 (root-mean-square) in the frequency range from 1 to 16 Hz at single axis. The frequency characteristics were flat from 1 to 12 Hz, but 14, 16 Hz was considerably poor. Second, the vibrator was excited when using a complex signal consisting of 12 components in the frequency range from 1 to 12 Hz at single axis. The overall acceleration was 3 and 1 m/s2. Flat characteristics were seen in the tested frequency range. Acceleration distortion was recognized in a higher frequency than the target frequency. This second method is effective for the efficiency of experimental procedure. PMID:12506857
Impact-absorbing characteristics by applying ultrasonic vibration
NASA Astrophysics Data System (ADS)
Suzuki, Atsuyuki; Ueki, Eiichiro; Tsujino, Jiromaru
2012-05-01
An impact-absorbing device that facilitates the application of ultrasonic vibrations was devised. Vibration distributions, springback characteristics, and impact-absorption characteristics were measured. We confirm that the springback amount decreases and the impact is absorbed upon the application of ultrasonic vibrations. When an aluminum alloy plate is crumpled, the maximum output voltage of the attached shock sensor decreases to 65% upon the application of ultrasonic vibrations as compared to when the ultrasonic vibrations are not applied.
Effect of Vibration on Retention Characteristics of Screen Acquisition Systems
NASA Technical Reports Server (NTRS)
Tegart, J. R.; Park, A. C.
1977-01-01
An analytical and experimental investigation of the effect of vibration on the retention characteristics of screen acquisition systems was performed. The functioning of surface tension devices using fine-mesh screens requires that the pressure differential acting on the screen be less than its pressure retention capability. When exceeded, screen breakdown will occur and gas-free expulsion of propellant will no longer be possible. An analytical approach to predicting the effect of vibration was developed. This approach considers the transmission of the vibration to the screens of the device and the coupling of the liquid and the screen in establishing the screen response. A method of evaluating the transient response of the gas/liquid interface within the screen was also developed.
Vibration characteristic of high power CO2 laser
NASA Astrophysics Data System (ADS)
Zhang, Kuo
2015-02-01
High power CO2 laser is widely used in various scientific, industrial and military applications. Vibration is a common phenomenon during laser working process, it will affect the working performance of high power CO2 laser, vibration must be strictly controlled in the condition where the laser pointing is required. This paper proposed a method to investigate the vibration characteristic of high power CO2 laser. An experiment device with vibration acceleration sensor was established to measure vibration signal of CO2 laser, the measured vibration signal was mathematically treated using space-frequency conversion, and then the vibration characteristic of high power CO2 laser can be obtained.
Vibration characteristics of ultrasonic complex vibration for hole machining
NASA Astrophysics Data System (ADS)
Asami, Takuya; Miura, Hikaru
2012-05-01
Complex vibration sources that use diagonal slits as a longitudinal-torsional vibration converter have been applied to ultrasonic motors, ultrasonic rock drilling, and ultrasonic welding. However, there are few examples of the application of these sources to ultrasonic machining in combination with an abrasive. Accordingly, a new method has been developed for machining of holes in brittle materials by using the ultrasonic longitudinal and torsional vibration of a hollow-type stepped horn with a diagonal slit vibration converter. In this paper, we compared vibration of a uniform rod and a hollow-type stepped horn, both with diagonal slits, when the conditions of the diagonal slits are constant.
Human response to vibration in residential environments.
Waddington, David C; Woodcock, James; Peris, Eulalia; Condie, Jenna; Sica, Gennaro; Moorhouse, Andrew T; Steele, Andy
2014-01-01
This paper presents the main findings of a field survey conducted in the United Kingdom into the human response to vibration in residential environments. The main aim of this study was to derive exposure-response relationships for annoyance due to vibration from environmental sources. The sources of vibration considered in this paper are railway and construction activity. Annoyance data were collected using questionnaires conducted face-to-face with residents in their own homes. Questionnaires were completed with residents exposed to railway induced vibration (N = 931) and vibration from the construction of a light rail system (N = 350). Measurements of vibration were conducted at internal and external positions from which estimates of 24-h vibration exposure were derived for 1073 of the case studies. Sixty different vibration exposure descriptors along with 6 different frequency weightings were assessed as potential predictors of annoyance. Of the exposure descriptors considered, none were found to be a better predictor of annoyance than any other. However, use of relevant frequency weightings was found to improve correlation between vibration exposure and annoyance. A unified exposure-response relationship could not be derived due to differences in response to the two sources so separate relationships are presented for each source. PMID:24437758
Vibration characteristics of floating slab track
NASA Astrophysics Data System (ADS)
Kuo, Chen-Ming; Huang, Cheng-Hao; Chen, Yi-Yi
2008-11-01
Coupled equilibrium equations of suspended wheels and floating slab track system were solved with the fourth-order Runge-Kutta method to obtain the deflections, vibration velocities, and wheel-rail contact forces. The program was validated through several aspects. Cases with various vehicle speed, slab mass, and stiffness of slab bearing were analyzed to reveal the effects of slab bearing on track responses. The correlation between wheel-rail resonance and train speed was also discussed. It was found that rail deflections increase significantly as train speed increases. Although large slab mass may lower tuning frequency, it could also result in higher wheel-rail contact force and rail deflections. The floating slab track is effective in isolating loading above 10 Hz, which might present in some railway sections with irregularities. Adopting floating slab track for vibration control for environment along the railway may cause concerns about ride quality and track damages.
Characteristic molecular vibrations of adenosine receptor ligands.
Chee, Hyun Keun; Yang, Jin-San; Joung, Je-Gun; Zhang, Byoung-Tak; Oh, S June
2015-02-13
Although the regulation of membrane receptor activation is known to be crucial for molecular signal transduction, the molecular mechanism underlying receptor activation is not fully elucidated. Here we study the physicochemical nature of membrane receptor behavior by investigating the characteristic molecular vibrations of receptor ligands using computational chemistry and informatics methods. By using information gain, t-tests, and support vector machines, we have identified highly informative features of adenosine receptor (AdoR) ligand and corresponding functional amino acid residues such as Asn (6.55) of AdoR that has informative significance and is indispensable for ligand recognition of AdoRs. These findings may provide new perspectives and insights into the fundamental mechanism of class A G protein-coupled receptor activation. PMID:25622891
Physiology responses of Rhesus monkeys to vibration
NASA Astrophysics Data System (ADS)
Hajebrahimi, Zahra; Ebrahimi, Mohammad; Alidoust, Leila; Arabian Hosseinabadi, Maedeh
Vibration is one of the important environmental factors in space vehicles that it can induce severe physiological responses in most of the body systems such as cardiovascular, respiratory, skeletal, endocrine, and etc. This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV), electrocardiograms (ECG) and respiratory rate in Rhesus monkeys. Methods: two groups of rhesus monkey (n=16 in each group) was selected as control and intervention groups. Monkeys were held in a sitting position within a specific fixture. The animals of this experiment were vibrated on a table which oscillated right and left with sinusoidal motion. Frequency and acceleration for intervention group were between the range of 1 to 2000 Hz and +0.5 to +3 G during 36 weeks (one per week for 15 min), respectively. All of the animals passed the clinical evaluation (echocardiography, sonography, radiography and blood analysis test) before vibration test and were considered healthy and these tests repeated during and at the end of experiments. Results and discussions: Our results showed that heart and respiratory rates increased significantly in response to increased frequency from 1 to 60 Hz (p <0.05) directly with the +G level reaching a maximum (3G) within a seconds compare to controls. There were no significant differences in heart and respiratory rate from 60 t0 2000 Hz among studied groups. All monkeys passed vibration experiment successfully without any arrhythmic symptoms due to electrocardiography analysis. Conclusion: Our results indicate that vibration in low frequency can effect respiratory and cardiovascular function in rhesus monkey. Keywords: Vibration, rhesus monkey, heart rate, respiratory rate
Natural vibration characteristics of gravity structures
NASA Astrophysics Data System (ADS)
Chugh, Ashok K.
2007-04-01
A forced vibration procedure is presented to estimate fundamental and higher frequencies of vibrations and associated mode shapes of gravity structures. The gravity structures considered are retaining walls and gravity dams. The validity of the proposed procedure is tested on three test problems of varying complexity for which the natural vibration frequencies and mode shapes either have known analytical solutions or have been determined via numerical means/field tests by others. Also included are the results of natural vibration frequencies and associated mode shapes for a spillway control structure located near the abutment end of an embankment dam obtained using the proposed procedure. For all problems considered, fundamental frequency and mode shape results using the proposed procedure are compared with the results obtained using an alternative procedure in which static deflections due to the structure's own weight are used as the starting point for free vibrations by setting the gravity vector to zero. All results compare well. The merits of the proposed procedure are discussed. Published in 2006 by John Wiley & Sons, Ltd.
Effects of vibration characteristics on the walking discomfort of floating floors on concrete slabs.
Kim, Jae Ho; Jeon, Jin Yong
2014-10-01
In the present study, the vibration characteristics of floating floor systems and the discomfort in walking upon them have been studied in concrete slab structures through mock-up floors experiments. Seven types of floor systems, with panels of various sizes and supporting beams with different joist spacings, were constructed based on actual conditions. For the vibration measurement, an ISO rubber ball dropped from a height of 20 cm was used as an impact source to reproduce human walking. The vibration characteristics were evaluated by calculating the vibration acceleration values and the autocorrelation function parameters for the floor structures. Finally, a human walking experiment was conducted to investigate subjective responses to the vibration characteristics of floating floors. From the results, it was found that the vibration acceleration values and walking discomfort varied with the supporting conditions of the floors and that these were highly correlated with each other. It was also found that more than 75% of subjects accepted the floors when the vibration value of the floor in terms of vibration does value (VDV) is below 4.8 ms(-1.75). In addition, a practical regression of the VDV was obtained and design guidelines for floating floors were suggested. PMID:25324073
Vibration characteristics analysis of rotating shrouded blades with impacts
NASA Astrophysics Data System (ADS)
Ma, Hui; Xie, Fangtao; Nai, Haiqiang; Wen, Bangchun
2016-09-01
A dynamic model of rotating shrouded blades with impacts among adjacent shrouded blades is established considering the effects of the centrifugal stiffening, spin softening and Coriolis force, and the model is validated using finite element method. In the proposed model, the shrouded blade is simplified as a cantilever Euler-Bernoulli beam with a mass point at the free end, and the flexural dynamic stiffness of shrouded blade is selected as contact stiffness during collision. Based on the developed model, the effects of symmetric and asymmetric shroud gaps, rotational speeds, and aerodynamic force amplitudes on the dynamic characteristics of shrouded blades are analyzed through Newmark-β numerical method. The results indicate that (1) the vibro-impact responses of shrouded blades under some asymmetric gaps are more complicated than that under symmetric gap. (2) With the increase of rotational speed from 6000 to 10,000 rev/min, the system vibration experiences from period-three motion, through chaotic motion, finally to period-one motion during collision process because the increasing rotational speed changes the flexural dynamic stiffness of rotating blade. (3) The vibration displacements of shrouded blades increase linearly, and impact force increases linearly with the increase of aerodynamic force amplitude.
Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness
NASA Technical Reports Server (NTRS)
Townsend, John S.
1987-01-01
A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. Using a perturbation expansion technique the free vibration solution is obtained in a closed-form, and the effects of system parameters on beam response are explored. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.
Mechanical characteristics of strained vibrating strings and a vibration-induced electric field
NASA Astrophysics Data System (ADS)
Bivin, Yu. K.
2012-11-01
The mechanical characteristics of vibrating strings strained between rigid supports and a vibration-induced electric field are studied. Experiments are conducted with nylon, rubber, and metallic strings. Vibrations are excited by a pinch at different sites along the string. The motion of the string is filmed, and the attendant electric field is detected. Experimental data are analyzed under the assumption that the field is induced by unlike charges generated by the moving string. It is found that the field allows one to determine the time characteristics of the motion of the string and discriminate the types of its deformations. Young moduli observed under the static extension of thin nylon strings are compared with those calculated from the natural frequencies of vibration measured for differently strained strings. The mathematical pattern of the motion of the string is compared with the real situation.
Thermal weights for semiclassical vibrational response functions
Moberg, Daniel R.; Alemi, Mallory; Loring, Roger F.
2015-08-28
Semiclassical approximations to response functions can allow the calculation of linear and nonlinear spectroscopic observables from classical dynamics. Evaluating a canonical response function requires the related tasks of determining thermal weights for initial states and computing the dynamics of these states. A class of approximations for vibrational response functions employs classical trajectories at quantized values of action variables and represents the effects of the radiation-matter interaction by discontinuous transitions. Here, we evaluate choices for a thermal weight function which are consistent with this dynamical approximation. Weight functions associated with different semiclassical approximations are compared, and two forms are constructed which yield the correct linear response function for a harmonic potential at any temperature and are also correct for anharmonic potentials in the classical mechanical limit of high temperature. Approximations to the vibrational linear response function with quantized classical trajectories and proposed thermal weight functions are assessed for ensembles of one-dimensional anharmonic oscillators. This approach is shown to perform well for an anharmonic potential that is not locally harmonic over a temperature range encompassing the quantum limit of a two-level system and the limit of classical dynamics.
Mounting method improves electrical and vibrational characteristics of screen electrodes
NASA Technical Reports Server (NTRS)
Nelson, R. E.
1969-01-01
Electrical characteristics of the mesh or screen electrodes used in electron tubes are improved by decreasing the shunt capacitance of the tube while retaining the close spacing needed for the required resolution. Vibrational characteristics are enhanced by raising the natural resonant frequency.
Peculiarities of Vibration Characteristics of Amorphous Ices
NASA Astrophysics Data System (ADS)
Gets, Kirill V.; Subbotin, Oleg S.; Belosludov, Vladimir R.
2012-03-01
Dynamic properties of low (LDA), high (HDA) and very high (VHDA) density amorphous ices were investigated within the approach based on Lattice Dynamics simulations. In this approach, we assume that the short-range molecular order mainly determines the dynamic and thermodynamic properties of amorphous ices. Simulation cell of 512 water molecules with periodical boundary conditions and disordering allows us to study dynamical properties and dispersion curves in the Brillouin zone of pseudo-crystal. Existence of collective phenomena in amorphous ices which is usual for crystals but anomalous for disordered phase was confirmed in our simulations. Molecule amplitudes of delocalized (collective) as well as localized vibrations have been considered.
Vertical Vibration Characteristics of a High-Temperature Superconducting Maglev Vehicle System
NASA Astrophysics Data System (ADS)
Jiang, Jing; Li, Ke Cai; Zhao, Li Feng; Ma, Jia Qing; Zhang, Yong; Zhao, Yong
2013-06-01
The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0-100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.
NASA Astrophysics Data System (ADS)
Zai, Behzad Ahmed; Sami, Saad; Khan, M. Amir; Ahmad, Furqan; Park, Myung Kyun
2015-09-01
Geometric or sub-scale modeling techniques are used for the evaluation of large and complex dynamic structures to ensure accurate reproduction of load path and thus leading to true dynamic characteristics of such structures. The sub-scale modeling technique is very effective in the prediction of vibration characteristics of original large structure when the experimental testing is not feasible due to the absence of a large testing facility. Previous researches were more focused on free and harmonic vibration case with little or no consideration for readily encountered random vibration. A sub-scale modeling technique is proposed for estimating the vibration characteristics of any large scale structure such as Launch vehicles, Mega structures, etc., under various vibration load cases by utilizing precise scaled-down model of that dynamic structure. In order to establish an analytical correlation between the original structure and its scaled models, different scale models of isotropic cantilever beam are selected and analyzed under various vibration conditions( i.e. free, harmonic and random) using finite element package ANSYS. The developed correlations are also validated through experimental testing. The prediction made from the vibratory response of the scaled-down beam through the established sets of correlation are found similar to the response measured from the testing of original beam structure. The established correlations are equally applicable in the prediction of dynamic characteristics of any complex structure through its scaled-down models. This paper presents modified sub-scale modeling technique that enables accurate prediction of vibration characteristics of large and complex structure under not only sinusoidal but also for random vibrations.
Scale-model characterization of flow-induced vibrational response of FFTF reactor internals
Ryan, J. A.; Mahoney, J. J.
1980-10-01
Fast Test Reactor core internal and peripheral components were assessed for flow-induced vibrational characteristics under scaled and simulated prototype flow conditions in the Hydraulic Core Mockup as an integral part of the Fast Test Reactor Vibration Program. The Hydraulic Core Mockup was an 0.285 geometric scale model of the Fast Test Reactor internals designed to simulate prototype vibrational and hydraulic characteristics. Using water to simulate sodium coolant, vibrational characteristics were measured and determined for selected model components over the scaled flow range of 36 to 110%. Additionally, in-situ shaker tests were conducted on selected Hydraulic Core Mockup outlet plenum components to establish modal characteristics. Most components exhibited resonant response at all test flow rates; however, the measured dynamic response was neither abnormal nor anomalously flow-rate dependent, and the predicted prototype components' response were deemed acceptable.
Vibration characteristics of a steadily rotating slender ring
NASA Technical Reports Server (NTRS)
Lallman, F. J.
1980-01-01
Partial differential equations are derived to describe the structural vibrations of a uniform homogeneous ring which is very flexible because the radius is very large compared with the cross sectional dimensions. Elementary beam theory is used and small deflections are assumed in the derivation. Four sets of structural modes are examined: bending and compression modes in the plane of the ring; bending modes perpendicular to the plane of the ring; and twisting modes about the centroid of the ring cross section. Spatial and temporal characteristics of these modes, presented in terms of vibration frequencies and ratios between vibration amplitudes, are demonstrated in several figures. Given a sufficiently high rotational rate, the dynamics of the ring approach those of a vibrating string. In this case, the velocity of traveling wave in the material of the ring approaches in velocity of the material relative to inertial space, resulting in structural modes which are almost stationary in space.
Human Response to Aircraft-Noise-Induced Building Vibration
NASA Technical Reports Server (NTRS)
Cawthorn, J. M.; Dempsey, T. K.; DeLoach, R.
1978-01-01
The effects of noise induced building structure vibration and the rattle of objects on human response to aircraft flyover noise were investigated in a series of studies conducted in both the field and the laboratory. The subjective detection thresholds for vibration and rattle were determined as well as the effect of vibration and rattle upon aircraft noise annoyance.
Longitudinal Vibration Characteristics Required to Cut a Circle by Ultrasonic Vibration
NASA Astrophysics Data System (ADS)
Takuya Asami,; Hikaru Miura,
2010-07-01
Currently, lasers and water jets are used to cut circles in brittle materials such as ceramics. However, a disadvantage of these methods is that the conventional equipment is large and complex. To resolve this issue, a method using the ultrasonic vibration of a hollow-type stepped horn for cutting is developed. We consider that this equipment can be simplified and miniaturized. The shape of the hollow-type stepped horn and the characteristics of the longitudinal vibration required to obtain excellent cutting properties were examined. As a result, the most appropriate depth of the hollow part is one-quarter of the wavelength for a hollow-type stepped horn that vibrates longitudinally. The amplification factor is proportional to the cross-sectional ratio providing the cross-sectional ratio does not exceed 4.6. The characteristics of the longitudinal vibration of the hollow-type stepped horn when the static pressing force at the tip of the horn is varied were also examined. It was clarified that the ultrasonic vibration of a hollow-type stepped horn can be used to cut brittle materials.
Characteristic infrared intensities of carbonyl stretching vibrations.
Richter, Wagner E; Silva, Arnaldo F; Vidal, Luciano N; Bruns, Roy E
2016-07-14
The experimental infrared fundamental intensities of gas phase carbonyl compounds obtained by the integration of spectral bands in the Pacific Northwest National Laboratory (PNNL) spectral database are in good agreement with the intensities reported by other laboratories having a root mean square error of 27 km mol(-1) or about 13% of the average intensity value. The Quantum Theory of Atoms in Molecules/Charge-Charge Transfer-Counterpolarization (QTAIM/CCTCP) model indicates that the large intensity variation from 61.7 to 415.4 km mol(-1) is largely due to static atomic charge contributions, whereas charge transfer and counterpolarization effects essentially cancel one another leaving only a small net effect. The Characteristic Substituent Shift Model estimates the atomic charge contributions to the carbonyl stretching intensities within 30 km mol(-1) or 10% of the average contribution. However, owing to the size of the 2 × C × CTCP interaction contribution, the total intensities cannot be estimated with this degree of accuracy. The dynamic intensity contributions of the carbon and oxygen atoms account for almost all of the total stretching intensities. These contributions vary over large ranges with the dynamic contributions of carbon being about twice the size of the oxygen ones for a large majority of carbonyls. Although the carbon monoxide molecule has an almost null dipole moment contrary to the very polar bond of the characteristic carbonyl group, its QTAIM/CCTCP model is very similar to those found for the carbonyl compounds. PMID:27306140
Characteristics of Vibration that Alter Cardiovascular Parameters in Mice
Li, Yao; Rabey, Karyne N; Schmitt, Daniel; Norton, John N; Reynolds, Randall P
2015-01-01
We hypothesized that short-term exposure of mice to vibration within a frequency range thought to be near the resonant frequency range of mouse tissue and at an acceleration of 0 to 1 m/s2 would alter heart rate (HR) and mean arterial pressure (MAP). We used radiotelemetry to evaluate the cardiovascular response to vibration in C57BL/6 and CD1 male mice exposed to vertical vibration of various frequencies and accelerations. MAP was consistently increased above baseline values at an acceleration near 1 m/s2 and a frequency of 90 Hz in both strains, and HR was increased also in C57BL/6 mice. In addition, MAP increased at 80 Hz in individual mice of both strains. When both strains were analyzed together, mean MAP and HR were increased at 90 Hz at 1 m/s2, and HR was increased at 80 Hz at 1 m/s2. No consistent change in MAP or HR occurred when mice were exposed to frequencies below 80 Hz or above 90 Hz. The increase in MAP and HR occurred only when the mice had conscious awareness of the vibration, given that these changes did not occur when anesthetized mice were exposed to vibration. Tested vibration acceleration levels lower than 0.75 m/s2 did not increase MAP or HR at 80 or 90 Hz, suggesting that a relatively high level of vibration is necessary to increase these parameters. These data are important to establish the harmful frequencies and accelerations of environmental vibration that should be minimized or avoided in mouse facilities. PMID:26224436
A direct evidence of vibrationally delocalized response at ice surface
Ishiyama, Tatsuya; Morita, Akihiro
2014-11-14
Surface-specific vibrational spectroscopic responses at isotope diluted ice and amorphous ice are investigated by molecular dynamics (MD) simulations combined with quantum mechanics/molecular mechanics calculations. The intense response specific to the ordinary crystal ice surface is predicted to be significantly suppressed in the isotopically diluted and amorphous ices, demonstrating the vibrational delocalization at the ordinary ice surface. The collective vibration at the ice surface is also analyzed with varying temperature by the MD simulation.
Nuclear shell structure and response with quasiparticle-vibration coupling
NASA Astrophysics Data System (ADS)
Litvinova, Elena; Ring, Peter
Extensions of the covariant density functional theory by quasiparticle-vibration coupling (QVC) are discussed. The formalism for one-body and two-body propagators in the nuclear medium allows calculations of single-particle energies and spectroscopic factors as well as the response to various types of excitations. In both cases QVC leads to a fragmentation of states, in agreement with experimental observations. Peculiarities of various 2p2h coupling schemes in the nuclear response function are discussed. The theory of the spin-isospin response includes both QVC and pion exchange and provides a framework for calculations of beta-decay, electron capture and charge-exchange reaction characteristics. The presented approaches are illustrated by realistic calculations for medium-mass and heavy nuclei.
Sound and structural vibration: Radiation, transmission and response
NASA Astrophysics Data System (ADS)
Fahy, F.
The physical process of vibrational interaction between fluids and solid structures, and models and analyses of the behavior of coupled fluid-structure systems are described. The temporal and spatial distributions of wave field variables, the characteristics of waves in beam, plate, and shell structures, the dispersion relationships between wave speed and frequency forms, the natural frequencies and modes of bounded elastic systems, and the functions of outgoing and returning waves are discussed. The mechanics of sound radiation from vibratory surfaces and the use of far-field evaluation of the Rayleigh integral and traveling wave Fourier component synthesis for analysis of sound radiation for planar surfaces are studied. Fluid loading or vibrating structures, the wave impediance or structures and fluids, and the effects of fluid loading on the radiation of plates are investigated. Sound transmission through various plane partitions, flexural wave propagation in a circular cylindrical shell, and the coupling between shell modes and acoustic duct modes are considered. The analysis of the vibrational response of thin-plate and shell structures to incident sound, acoustic-coupling between structures and enclosed volumes of fluid, and analyses of fluid-structure interaction are examined.
Analysis of Vibrational Harmonic Response for Printing Double-Sheet Detecting System via ANSYS
NASA Astrophysics Data System (ADS)
Guo, Qiang; Cai, Ji-Fei; Wang, Yan; Zhang, Yang
In order to explore the influence of the harmonic response of system vibration upon the stability of the double-sheet detector system, the mathematical model of vibrational system is established via the mechanical dynamic theory. Vibrational system of double-sheet detector is studied by theoretical modeling, and the dynamic simulation to obtain the amplitude/phase frequency response curve of the system based on ANSYS is completed to make a comparison with the theoretical results. It is shown that the theoretical value is basically consistent with that calculated through ANSYS. Conclusion vibrational characteristics of double-sheet detection system is obtained quickly and accurately, and propound solving measures by some crucial factors, such as the harmonic load, mass and stiffness, which will affect the vibration of the system, contribute to the finite element method is applied to the complex multiple-degree-of-freedom system.
Torsional vibration transmissibility characteristics of reinforced viscoelastic flexible pipes
NASA Astrophysics Data System (ADS)
Kennedy, I.; Tomlinson, G. R.
1988-04-01
The dynamic complex shear moduli of fibre and steel reinforced viscoelastic flexible pipes are determined by using a torsional non-resonance method. Material property master curves as a function of frequency and temperature are obtained by using reduced modulus methods. In situations where the loss factor data is difficult to measure directly it is shown that these data can be obtained from the modulus data by using a stepwise Hilbert transform technique. Predictions of the torsional vibration transmissibility of reinforced pipes, by using a simple theory in conjunction with the material properties, results in a close comparison with experimental measurements of the torsional vibration transmissibility characteristics of the pipes over a wide frequency range.
Human discomfort response to noise combined with vertical vibration
NASA Technical Reports Server (NTRS)
Leatherwood, J. D.
1979-01-01
An experimental investigation was conducted (1) to determine the effects of combined environmental noise and vertical vibration upon human subjective discomfort response, (2) to develop a model for the prediction of passenger discomfort response to the combined environment, and (3) to develop a set of noise-vibration curves for use as criteria in ride quality design. Subjects were exposed to parametric combinations of noise and vibrations through the use of a realistic laboratory simulator. Results indicated that accurate prediction of passenger ride comfort requires knowledge of both the level and frequency content of the noise and vibration components of a ride environment as well as knowledge of the interactive effects of combined noise and vibration. A design tool in the form of an empirical model of passenger discomfort response to combined noise and vertical vibration was developed and illustrated by several computational examples. Finally, a set of noise-vibration criteria curves were generated to illustrate the fundamental design trade-off possible between passenger discomfort and the noise-vibration levels that produce the discomfort.
Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness
NASA Technical Reports Server (NTRS)
Townsend, John S.
1987-01-01
A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. The effects of system parameters on beam response are explored with a perturbation expansion technique. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.
Vibration and formability characteristics of aluminum-polymer sandwich materials
NASA Astrophysics Data System (ADS)
Somayajulu, Thamma S. V.
Metal/polymer/metal sandwich materials are finding increasing use in the automotive industry primarily as lightweight alternatives to steel and aluminum alloys. In addition to low density they also offer other functional benefits e.g. improved vibration damping. In order to exploit such beneficial characteristics it is necessary to examine the manufacturability of these materials. In this work the vibration characteristics and formability were examined in selected materials, chosen from a group of aluminum/polypropylene/aluminum sandwich materials. First, a systematic study was carried out on vibration characteristics of square sandwich plates using 3D finite element models and usefulness of such a 3D displacement field in understanding the damping mechanisms as well as their contributions toward the modal damping were discussed. Second, a study of stretch formability of several sandwich materials was conducted. Since the knowledge of tensile properties is essential for understanding the formability, those properties were determined by performing uniaxial tensile tests on several aluminum/polypropylene/aluminum (HyliteRTM) sandwich materials and their constituent materials. The phenomena of diffused necking and deformation of material up to and beyond the point of necking were systematically investigated. Furthermore, the formability of sandwich materials was assessed by comparing the experimentally determined forming limit diagrams (FLDs) of monolithic 5182 aluminum and several sandwich materials. In addition to the experimental research, theoretical modeling was carried out to predict formability based on the concept of growth of pre-existing defects. One such model, known as M-K analysis, was utilized on the basis of defects existing in (i) the aluminum skins and (ii) the overall thickness of the sandwich. The experimental and theoretical results suggest that the levels of forming limit in sandwich materials are far less than those for monolithic materials of
NASA Astrophysics Data System (ADS)
Adewusi, S. A.; Rakheja, S.; Marcotte, P.; Boutin, J.
2010-07-01
Biodynamic responses of the hand-arm system have been mostly characterized in terms of driving-point force-motion relationships, which have also served as the primary basis for developing the mechanical-equivalent models. The knowledge of localized vibration responses of the hand-arm segments could help derive more effective biodynamic models. In this study, the transmission of z h-axis handle vibration to the wrist, elbow and the shoulder of the human hand and arm are characterized in the laboratory for the bent-arm and extended arm postures. The experiments involved six subjects grasping a handle subject to two different magnitudes of broad-band random vibration, and nine different combinations of hand grip and push forces. The vibration transmissibility data were acquired in the z h- and y h-axis at the wrist and shoulder, and along all the three axes around the elbow joint. The results show that the human hand-arm system in an extended arm posture amplifies the vibration transmitted to the upper-arm and the whole-body at frequencies below 25 Hz, but attenuates the vibration above 25 Hz more effectively than the bent-arm posture, except at the shoulder. The magnitudes of transmitted vibration under an extended arm posture along the y h-axis were observed to be nearly twice those for the bent-arm posture in the low frequency region. The results further showed that variations in the grip force mostly affect vibration transmissibility and characteristic frequencies of the forearm, while changes in the push force influenced the dynamic characteristics of the entire hand-arm system. The magnitudes of transmitted vibration in the vicinity of the characteristic frequencies were influenced by the handle vibration magnitude.
NASA Technical Reports Server (NTRS)
Genkin, M. D.; Yelezov, V. G.; Yablonskiy, V. V.
1973-01-01
The efficiency and resistance of an active vibration isolation system (AVI) are analyzed for the case of unidirectional vibrations of a mass on a spring, with a damper, resting on a rigid base. The effect of certain vibroacoustical characteristics of real objects on AVI resistance and synthesis of AVI, which are effective over a wide frequency band are considered. A numerical analysis of the response of a mechanical system with AVI features is presented.
Zhou, Zhen; Griffin, Michael J
2014-01-01
The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1-1.6 ms(-2) r.m.s.) and with random vibration (1-16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation. PMID:24730687
Thermoregulatory responses to heat and vibration in men
NASA Technical Reports Server (NTRS)
Spaul, W. A.; Spear, R. C.; Greenleaf, J. E.
1986-01-01
The effect of vibration on thermoregulatory responses was studied in heat-acclimated men exposed suddenly to simultaneous heat and whole body vibrations (WBVs) at two intensity levels, each at graded frequencies between 5 and 80 Hz. The mean rectal temperature (Tre) became elevated more quickly in the WBV exposures than in the controls (heat exposure alone). Both intensity- and frequency-dependent WBV relationships were recorded in localized blood flows and in sweat rates. Thus, vibration appears to reduce the efficiency of the cooling mechanisms during a heat exposure.
Vibration response mechanism of faulty outer race rolling element bearings for quantitative analysis
NASA Astrophysics Data System (ADS)
Cui, Lingli; Zhang, Yu; Zhang, Feibin; Zhang, Jianyu; Lee, Seungchul
2016-03-01
For the quantitative fault diagnosis of rolling element bearings, a nonlinear vibration model for fault severity assessment of rolling element bearings is established in this study. The outer race defect size parameter is introduced into the dynamic model, and vibration response signals of rolling element bearings under different fault sizes are simulated. The signals are analyzed quantitatively to observe the relationship between vibration responses and fault sizes. The impact points when the ball rolls onto and away from the defect are identified from the vibration response signals. Next, the impact characteristic that reflects the fault severity in rolling element bearings is obtained from the time interval between two impact points. When the width of the bearing fault is small, the signals are presented as clear single impact. The signals gradually become double impacts with increasing size of defects. The vibration signals of a rolling element bearings test rig are measured for different outer race fault sizes. The experimental results agree well with the results from simulations. These results are useful for understanding the vibration response mechanism of rolling element bearings under various degrees of fault severity.
The flaminio obelisk in Rome: vibrational characteristics as part of preservation efforts
Bongiovanni, G.; Celebi, M.; Clemente, P.
1990-01-01
The purpose of the paper is to study the vibrational characteristics of the Flaminio Obelisk in Rome as part of general studies being performed for preservation purposes. The state of preservation of the monument is described as well as the sonic method used to evaluate the integrity of the sections. The results of the sonic tests are used to determine reductions in the cross-sectional properties. A stick model including two rotational frequency independent soil springs at the basement level of the obelisk is developed. A response spectrum and stress analysis according to the Italian Seismic Code is performed considering and evaluating the degraded characteristics of sections. -from Authors
Vibration characteristics of rectangular plate in compressible inviscid fluid
NASA Astrophysics Data System (ADS)
Liao, Chan-Yi; Ma, Chien-Ching
2016-02-01
This paper presents a mathematical derivation of the vibration characteristics of an elastic thin plate placed at the bottom of a three dimensional rectangular container filled with compressible inviscid fluid. A set of beam functions is used as the admissible functions of the plate in a fluid-plate system, and the motion of the fluid induced by the deformation of the plate is obtained from a three-dimensional acoustic equation. Pressure from the fluid over the fluid-plate interface is integrated to form a virtual mass matrix. The frequency equation of the fluid-plate system is derived by combining mass, stiffness, and the virtual mass matrix. Solving the frequency equation makes it possible to obtain the dynamic characteristic of the fluid-plate system, such as resonant frequencies, corresponding mode shapes, and velocity of the fluid. Numerical calculations were performed for plates coupled with fluids with various degrees of compressibility to illustrate the difference between compressible and incompressible fluids in a fluid-plate system. The proposed method could be used to predict resonant frequencies and mode shapes with accuracy compared to that of incompressible fluid theory (IFT). The proposed method can be used to analyze cases involving high value of sound velocity, such as incompressible fluids. When the sound velocity approaches infinity, the results obtained for compressible fluids are similar to those of incompressible fluids. We also examined the influence of fluid compressibility on vibration characteristics in which a decrease in sound velocity was shown to correspond to a decrease in resonant frequency. Additional modes, not observed in incompressible fluids, were obtained in cases of low sound velocity, particularly at higher resonant frequencies. Fluid velocity plots clearly reveal that the additional resonant modes can be attributed to the compressible behavior of the fluid.
Tsujino, J; Ihara, S; Harada, Y; Kasahara, K; Sakamaki, N
2004-04-01
Welding characteristic of thin coated copper wires were studied using 40, 60, 100 kHz ultrasonic complex vibration welding equipments with elliptical to circular vibration locus. The complex vibration systems consisted of a longitudinal-torsional vibration converter and a driving longitudinal vibration system. Polyurethane coated copper wires of 0.036 mm outer diameter and copper plates of 0.3 mm thickness and the other dimension wires were used as welding specimens. The copper wire part is completely welded on the copper substrate and the insulated coating material is driven from welded area to outsides of the wire specimens by high frequency complex vibration. PMID:15047272
Damage Identification of Piles Based on Vibration Characteristics
Zhang, Xiaozhong; Yao, Wenjuan; Chen, Bo; Liu, Dewen
2014-01-01
A method of damage identification of piles was established by using vibration characteristics. The approach focused on the application of the element strain energy and sensitive modals. A damage identification equation of piles was deduced using the structural vibration equation. The equation contained three major factors: change rate of element modal strain energy, damage factor of pile, and sensitivity factor of modal damage. The sensitive modals of damage identification were selected by using sensitivity factor of modal damage firstly. Subsequently, the indexes for early-warning of pile damage were established by applying the change rate of strain energy. Then the technology of computational analysis of wavelet transform was used to damage identification for pile. The identification of small damage of pile was completely achieved, including the location of damage and the extent of damage. In the process of identifying the extent of damage of pile, the equation of damage identification was used in many times. Finally, a stadium project was used as an example to demonstrate the effectiveness of the proposed method of damage identification for piles. The correctness and practicability of the proposed method were verified by comparing the results of damage identification with that of low strain test. The research provided a new way for damage identification of piles. PMID:25506062
Tsujino, J; Ueoka, T
2004-04-01
Configurations of large capacity ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. The ultrasonic complex vibration systems are effective and essential for new applications in various industries. The complex vibration source of 27 kHz consists of a complex transverse rod with a welding tip (aluminum alloy, stainless steel and titanium alloy), a complex vibration rod with a flange and stepped part for holding the system, a circular longitudinal vibration disk (aluminum alloy) and six bolt-clamped Langevin type PLT transducers. Three transducer pairs are driven simultaneously using three driving systems at phase difference 120 degrees, and almost circular vibration locus is obtained. PMID:15047267
Investigation of vibrational characteristics in BBO crystals by femtosecond CARS
NASA Astrophysics Data System (ADS)
Xia, Yuanqin; Zhao, Yang; Wang, Zi; Zhang, Sheng; Dong, Zhiwei; Chen, Deying; Zhang, Zhonghua
2012-10-01
Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) is utilized to study the ultrafast vibrational dynamics in BBO crystals at room temperature. Time-resolved two-beam and three-beam CARS are detected. The vibrational dephasing time is analyzed and the changes of vibrational mode intensities with the polarization of pump pulses are observed.
NASA Astrophysics Data System (ADS)
Hansen, Mikkel Bo; Christiansen, Ove; Hättig, Christof
2009-10-01
Quadratic response functions are derived and implemented for a vibrational configuration interaction state. Combined electronic and vibrational quadratic response functions are derived using Born-Oppenheimer vibronic product wave functions. Computational tractable expressions are derived for determining the total quadratic response contribution as a sum of contributions involving both electronic and vibrational linear and quadratic response functions. In the general frequency-dependent case this includes a new and more troublesome type of electronic linear response function. Pilot calculations for the FH, H2O, CH2O, and pyrrole molecules demonstrate the importance of vibrational contributions for accurate comparison to experiment and that the vibrational contributions in some cases can be very large. The calculation of transition properties between vibrational states is combined with sum-over-states expressions for analysis purposes. On the basis of this some simple analysis methods are suggested. Also, a preliminary study of the effect of finite lifetimes on quadratic response functions is presented.
An optimized semiclassical approximation for vibrational response functions
NASA Astrophysics Data System (ADS)
Gerace, Mallory; Loring, Roger F.
2013-03-01
The observables of multidimensional infrared spectroscopy may be calculated from nonlinear vibrational response functions. Fully quantum dynamical calculations of vibrational response functions are generally impractical, while completely classical calculations are qualitatively incorrect at long times. These challenges motivate the development of semiclassical approximations to quantum mechanics, which use classical mechanical information to reconstruct quantum effects. The mean-trajectory (MT) approximation is a semiclassical approach to quantum vibrational response functions employing classical trajectories linked by deterministic transitions representing the effects of the radiation-matter interaction. Previous application of the MT approximation to the third-order response function R(3)(t3, t2, t1) demonstrated that the method quantitatively describes the coherence dynamics of the t3 and t1 evolution times, but is qualitatively incorrect for the waiting-time t2 period. Here we develop an optimized version of the MT approximation by elucidating the connection between this semiclassical approach and the double-sided Feynman diagrams (2FD) that represent the quantum response. Establishing the direct connection between 2FD and semiclassical paths motivates a systematic derivation of an optimized MT approximation (OMT). The OMT uses classical mechanical inputs to accurately reproduce quantum dynamics associated with all three propagation times of the third-order vibrational response function.
An optimized semiclassical approximation for vibrational response functions
Gerace, Mallory; Loring, Roger F.
2013-01-01
The observables of multidimensional infrared spectroscopy may be calculated from nonlinear vibrational response functions. Fully quantum dynamical calculations of vibrational response functions are generally impractical, while completely classical calculations are qualitatively incorrect at long times. These challenges motivate the development of semiclassical approximations to quantum mechanics, which use classical mechanical information to reconstruct quantum effects. The mean-trajectory (MT) approximation is a semiclassical approach to quantum vibrational response functions employing classical trajectories linked by deterministic transitions representing the effects of the radiation-matter interaction. Previous application of the MT approximation to the third-order response function R(3)(t3, t2, t1) demonstrated that the method quantitatively describes the coherence dynamics of the t3 and t1 evolution times, but is qualitatively incorrect for the waiting-time t2 period. Here we develop an optimized version of the MT approximation by elucidating the connection between this semiclassical approach and the double-sided Feynman diagrams (2FD) that represent the quantum response. Establishing the direct connection between 2FD and semiclassical paths motivates a systematic derivation of an optimized MT approximation (OMT). The OMT uses classical mechanical inputs to accurately reproduce quantum dynamics associated with all three propagation times of the third-order vibrational response function. PMID:23556706
Vibration Response of Multi Storey Building Using Finite Element Modelling
NASA Astrophysics Data System (ADS)
Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.
2016-07-01
Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.
NASA Astrophysics Data System (ADS)
Liu, Chao; Jiang, Dongxiang; Chu, Fulei
2015-09-01
As important causes of fatigue and crack failure, alternating loads also affect vibration characteristics of cracked blades in rotor system and probably influence formulation of diagnostic rule. This work carried out analysis of nonlinear vibration of cracked blade in rotor system with crack breathing effects and alternating loads taken into account. Firstly, equations of motion are formed with Finite Element Method (FEM), and breathing crack is modeled with cracked hexahedral element (CHE) where the breathing behavior is load-dependent. Secondly, displacement responses of cracked blade are obtained, and the results with CHE and contact element are identical. The stiffness of the cracked blade is obtained with CHE and proved to be time-varying and dependent on the alternating loads. Thirdly, natural frequencies of cracked blade in stationary condition are analyzed including normal model, linear model (open crack) and nonlinear model (breathing crack), and the requirement of the inclusion of breathing effects in blades with fatigue crack is proved. Finally, influence of alternating loads on critical frequency of cracked blade in rotating condition is compared. The results show that the critical frequency is significantly affected due to the co-effects of the rotating speed and alternating loads. The proposed method can estimate nonlinear vibration characteristics of crack blade which is beneficial for the formulation of the diagnostic rule.
Rocket Launch-Induced Vibration and Ignition Overpressure Response
NASA Technical Reports Server (NTRS)
Caimi, Raoul E.; Margashayam, Ravi N.; Nayfeh, Jamal F.; Thompson, Karen (Technical Monitor)
2001-01-01
Rocket-induced vibration and ignition overpressure response environments are predicted in the low-frequency (5 to 200 hertz) range. The predictions are necessary to evaluate their impact on critical components, structures, and facilities in the immediate vicinity of the rocket launch pad.
NASA Astrophysics Data System (ADS)
Sun, W.; Liu, Y.
2016-08-01
The strain dependent characteristics of hard coatings make the vibration analysis of hard-coated composite structure become a challenging task. In this study, the modeling and the analysis method of a hard-coated composite beam was developed considering the strain dependent characteristics of coating material. Firstly, based on analyzing the properties of hard-coating material, a high order polynomial was adopted to characterize the strain dependent characteristics of coating materials. Then, the analytical model of a hard-coated composite beam was created by the energy method. Next, using the numerical method to solve the vibration response and the resonance frequencies of the composite beam, a specific calculation flow was also proposed. Finally, a cantilever beam coated with MgO + Al2O3 hard coating was chosen as the study case; under different excitation levels, the resonance region responses and the resonance frequencies of the composite beam were calculated using the proposed method. The calculation results were compared with the experiment and the linear calculation, and the correctness of the created model was verified. The study shows that compared with the general linear calculation, the proposed method can still maintain an acceptable precision when the excitation level is larger.
NASA Astrophysics Data System (ADS)
Sun, W.; Liu, Y.
2016-05-01
The strain dependent characteristics of hard coatings make the vibration analysis of hard-coated composite structure become a challenging task. In this study, the modeling and the analysis method of a hard-coated composite beam was developed considering the strain dependent characteristics of coating material. Firstly, based on analyzing the properties of hard-coating material, a high order polynomial was adopted to characterize the strain dependent characteristics of coating materials. Then, the analytical model of a hard-coated composite beam was created by the energy method. Next, using the numerical method to solve the vibration response and the resonance frequencies of the composite beam, a specific calculation flow was also proposed. Finally, a cantilever beam coated with MgO + Al2 O3 hard coating was chosen as the study case; under different excitation levels, the resonance region responses and the resonance frequencies of the composite beam were calculated using the proposed method. The calculation results were compared with the experiment and the linear calculation, and the correctness of the created model was verified. The study shows that compared with the general linear calculation, the proposed method can still maintain an acceptable precision when the excitation level is larger.
Nonlinear characteristics analysis of vortex-induced vibration for a three-dimensional flexible tube
NASA Astrophysics Data System (ADS)
Feng, Zhipeng; Jiang, Naibin; Zang, Fenggang; Zhang, Yixiong; Huang, Xuan; Wu, Wanjun
2016-05-01
Vortex-induced vibration of a three-dimensional flexible tube is one of the key problems to be considered in many engineering situations. This paper aims to investigate the nonlinear dynamic behaviors and response characteristics of a three-dimensional tube under turbulent flow. The three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model are solved with the finite volume approach, and the dynamic equilibrium equations are discretized by the finite element theory. A three-dimensional fully coupled numerical model for vortex-induced vibration of flexible tube is proposed. The model realized the fluid-structure interaction with solving the fluid flow and the structure vibration simultaneously. Based on this model, Response regimes, trajectory, phase difference, fluid force coefficient and vortex shedding frequency are obtained. The nonlinear phenomena of lock-in, phase-switch are captured successfully. Meanwhile, the limit cycle, bifurcation of lift coefficient and displacement are analyzed using phase portrait and Poincare section. The results reveal that, a quasi-upper branch occurs in the present fluid-flexible tube coupling system with high mass-damping and low mass ratio. There is no bifurcation of lift coefficient and lateral displacement occurred in the three-dimensional flexible tube submitted to uniform turbulent flow.
Vibrational characteristics of FRP-bonded concrete interfacial defects in a low frequency regime
NASA Astrophysics Data System (ADS)
Cheng, Tin Kei; Lau, Denvid
2014-04-01
As externally bonded fiber-reinforced polymer (FRP) is a critical load-bearing component of strengthened or retrofitted civil infrastructures, the betterment of structural health monitoring (SHM) methodology for such composites is imperative. Henceforth the vibrational characteristics of near surface interfacial defects involving delamination and trapped air pockets at the FRP-concrete interface are investigated in this study using a finite element approach. Intuitively, due to its lower interfacial stiffness compared with an intact interface, a damaged region is expected to have a set of resonance frequencies different from an intact region when excited by acoustic waves. It has been observed that, when excited acoustically, both the vibrational amplitudes and frequency peaks in the response spectrum of the defects demonstrate a significant deviation from an intact FRP-bonded region. For a thin sheet of FRP bonded to concrete with sizable interfacial defects, the fundamental mode under free vibration is shown to be relatively low, in the order of kHz. Due to the low resonance frequencies of the defects, the use of low-cost equipment for interfacial defect detection via response spectrum analysis is highly feasible.
Vibration characteristics of an APS lab facility in Building 401
Royston, T.J.
1998-01-01
The vibratory behavior of a lab facility located in Building 401 of the Advanced Photon Source site at Argonne National Laboratory is summarized. Measurements of ambient vibration indicate that acceptable displacement levels are usually maintained (rms value below 0.1 microns) for the measured frequency range, above 0.2 Hz. An exception occurs when strong wind conditions excite a horizontal building resonance near 1.85 Hz to rms levels as high as 0.3 microns. Measurements of the laboratory floor`s dynamic response to directly applied force excitation agree with theoretical predictions. The primary component of the floor construction is a reinforced concrete slab. The slab has a transverse fundamental resonant frequency of 18.5 Hz and an associated damping level of roughly 8.5% of critical. It is also shown via experimental measurements that the linoleum surface adhered to the concrete slab is far more compliant than the slab itself and can significantly influence the floor`s dynamic response to local excitations.
NASA Technical Reports Server (NTRS)
Taylor, R. B.; Zwicke, P. E.; Gold, P.; Miao, W.
1980-01-01
An analytical study was conducted to define the basic configuration of an active control system for helicopter vibration and gust response alleviation. The study culminated in a control system design which has two separate systems: narrow band loop for vibration reduction and wider band loop for gust response alleviation. The narrow band vibration loop utilizes the standard swashplate control configuration to input controller for the vibration loop is based on adaptive optimal control theory and is designed to adapt to any flight condition including maneuvers and transients. The prime characteristics of the vibration control system is its real time capability. The gust alleviation control system studied consists of optimal sampled data feedback gains together with an optimal one-step-ahead prediction. The prediction permits the estimation of the gust disturbance which can then be used to minimize the gust effects on the helicopter.
Semiclassical nonlinear response functions for coupled anharmonic vibrations
Gruenbaum, Scott M.; Loring, Roger F.
2009-11-28
Observables in linear and nonlinear infrared spectroscopy may be computed from vibrational response functions describing nuclear dynamics on a single electronic surface. We demonstrate that the Herman-Kluk (HK) semiclassical approximation to the quantum propagator yields an accurate representation of quantum coherence effects in linear and nonlinear response functions for coupled anharmonic oscillators. A considerable numerical price is paid for this accuracy; the calculation requires a multidimensional integral over a highly oscillatory integrand that also grows without bound as a function of evolution times. The interference among classical trajectories in the HK approximation produces quantization of good action variables. By treating this interference analytically, we develop a mean-trajectory (MT) approximation that requires only the propagation of classical trajectories linked by transitions in action. The MT approximation accurately reproduces coherence effects in response functions of coupled anharmonic oscillators in a regime in which the observables are strongly influenced by these interactions among vibrations.
The response of rotating machinery to external random vibration
NASA Technical Reports Server (NTRS)
Tessarzik, J. M.; Chiang, T.; Badgley, R. H.
1974-01-01
A high-speed turbogenerator employing gas-lubricated hydrodynamic journal and thrust bearings was subjected to external random vibrations for the purpose of assessing bearing performance in a dynamic environment. The pivoted-pad type journal bearings and the step-sector thrust bearing supported a turbine-driven rotor weighing approximately twenty-one pounds at a nominal operating speed of 36,000 rpm. The response amplitudes of both the rigid-supported and flexible-supported bearing pads, the gimballed thrust bearing, and the rotor relative to the machine casing were measured with capacitance type displacement probes. Random vibrations were applied by means of a large electrodynamic shaker at input levels ranging between 0.5 g (rms) and 1.5 g (rms). Vibrations were applied both along and perpendicular to the rotor axis. Response measurements were analyzed for amplitude distribution and power spectral density. Experimental results compare well with calculations of amplitude power spectral density made for the case where the vibrations were applied along the rotor axis. In this case, the rotor-bearing system was treated as a linear, three-mass model.
Vibration characteristics of hexagonal radial rib and hoop platforms
NASA Technical Reports Server (NTRS)
Belvin, W. K.
1983-01-01
Experiment and analysis have been used to characterize the modes of vibration of planar radial rib and hoop hexagonal platforms. Finite element analysis correlated very well with experimental results. The sensitivity of mode shapes and frequencies to cable stiffness and initial tension is presented. Threshold values have been identified, above which changes in cable stiffness do not affect the first few platform vibration modes. Primary vibration modes of the radial rib platform involve beam bending. Vibration modes of the hoop platform exhibit both beam bending and frame bending and torsion. Results indicate for low order polygonal structures, the radial rib concept produced a higher fundamental frequency. For high order polygonal structures, the hoop concept has the potential to achieve a higher fundamental frequency than the radial rib concept.
Vibration characteristics and damage detection in a suspension bridge
NASA Astrophysics Data System (ADS)
Wickramasinghe, Wasanthi R.; Thambiratnam, David P.; Chan, Tommy H. T.; Nguyen, Theanh
2016-08-01
Suspension bridges are flexible and vibration sensitive structures that exhibit complex and multi-modal vibration. Due to this, the usual vibration based methods could face a challenge when used for damage detection in these structures. This paper develops and applies a mode shape component specific damage index (DI) to detect and locate damage in a suspension bridge with pre-tensioned cables. This is important as suspension bridges are large structures and damage in them during their long service lives could easily go un-noticed. The capability of the proposed vibration based DI is demonstrated through its application to detect and locate single and multiple damages with varied locations and severity in the cables of the suspension bridge. The outcome of this research will enhance the safety and performance of these bridges which play an important role in the transport network.
Certain characteristics and capture regions of nonlinear vibrating systems
NASA Technical Reports Server (NTRS)
Ragulskene, V. L.
1973-01-01
Free vibrations of a system and vibrations which are multiples of them in frequency are discussed. The corresponding periodic forced vibrations of the type n/m (n is the number of periods of disturbance between periods of movement and m is the number of periods of movement in one period of disturbance), generated by a harmonic or close to harmonic disturbance, are propagated close to the corresponding curves of the free vibrations and their frequency multiples. It has been proposed that investigation of transitional modes of motion and capture regions be carried out by precise methods in phase space, with the least number of coordinates. Thus, for example, for nonautonomous second order equations (for example, the Duffing equations), in place of three variables (coordinates, velocity, phases), it is proposed to use two: velocity during transition of the coordinate through zero and phase.
NASA Technical Reports Server (NTRS)
On, F. J.
1983-01-01
A comparative evaluation of the Space Transportation System (STS)-3 flight and acoustic test random vibration response of the Office of Space Science-1 (OSS-1) payload is presented. The results provide insight into the characteristics of vibroacoustic response of pallet payload components in the payload bay during STS flights.
Tissue response to mechanical vibrations for "sonoelasticity imaging".
Parker, K J; Huang, S R; Musulin, R A; Lerner, R M
1990-01-01
The goal of "sonoelasticity imaging" is to differentiate between normal soft tissues and hard lesions. This is done by measuring and then displaying the ultrasound Doppler spectrum of regions within tissues which are mechanically forced with low frequency (20-1000 Hz) vibrations. The resolution and sensitivity of the technique ultimately rest on the spatial resolution of ultrasound Doppler detection, the low frequency mechanical properties of tissues, and the vibration response of layered, inhomogeneous regions with hard tumor inclusions and complicated boundary conditions set by the presence of skin, bones and other regions. An initial investigation has measured some tissue stiffness parameters, and applied these in a NASTRAN finite element analysis to simulate a prostate tumor in the pelvic cavity. The measurements show a wide separation between the elastic modulus of tumors and soft tissues such as muscle and prostate. NASTRAN analyses show the ability to delineate regions of different elasticity based on the pattern of vibration amplitudes. The ability to change vibration frequency within the 100-300 Hz band seems particularly helpful in simulations and experiments which visualize small stiff inclusions in tissues. Preliminary results support the postulate that sonoelasticity imaging can provide useful information concerning tissue properties that are not otherwise obtainable. PMID:2194336
Non-linear dual-axis biodynamic response to vertical whole-body vibration
NASA Astrophysics Data System (ADS)
Nawayseh, N.; Griffin, M. J.
2003-11-01
Seated human subjects have been exposed to vertical whole-body vibration so as to investigate the non-linearity in their biodynamic responses and quantify the response in directions other than the direction of excitation. Twelve males were exposed to random vertical vibration in the frequency range 0.25-25 Hz at four vibration magnitudes (0.125, 0.25, 0.625, and 1.25 m s -2 r.m.s.). The subjects sat in four sitting postures having varying foot heights so as to produce differing thigh contact with the seat (feet hanging, feet supported with maximum thigh contact, feet supported with average thigh contact, and feet supported with minimum thigh contact). Forces were measured in the vertical, fore-and-aft, and lateral directions on the seat and in the vertical direction at the footrest. The characteristic non-linear response of the human body with reducing resonance frequency at increasing vibration magnitudes was seen in all postures, but to a lesser extent with minimum thigh contact. Appreciable forces in the fore-and-aft direction also showed non-linearity, while forces in the lateral direction were low and showed no consistent trend. Forces at the feet were non-linear with a multi-resonant behaviour and were affected by the position of the legs. The decreased non-linearity with the minimum thigh contact posture suggests the tissues of the buttocks affect the non-linearity of the body more than the tissues of the thighs. The forces in the fore-and-aft direction are consistent with the body moving in two directions when exposed to vertical vibration. The non-linear behaviour of the body, and the considerable forces in the fore-aft direction should be taken into account when optimizing vibration isolation devices.
Vibration characteristics of composite fan blades and comparison with measured data
NASA Technical Reports Server (NTRS)
Chamis, C. C.
1976-01-01
The vibration characteristics of a composite fan blade for high-tip-speed applications were determined theoretically and the results compared with measured data. The theoretical results were obtained using a computerized capability consisting of NASTRAN coupled with composite mechanics by way of pre- and postprocessors. The predicted vibration frequencies and mode shapes were in reasonable agreement with the measured data. Theoretical results showed that different laminate configurations from the same composite system had only small effects on the blade frequency. However, the use of adhesively bonded titanium/beryllium laminar composites may improve considerably the blade vibration characteristics.
Seated Occupant Apparent Mass Characteristics Under Automotive Postures and Vertical Vibration
NASA Astrophysics Data System (ADS)
RAKHEJA, S.; HARU, I.; BOILEAU, P.-É.
2002-05-01
The biodynamic apparent mass response characteristics of 24 human subjects (12 males and 12 females) seated under representative automotive postures with hands-in-lap (passengers) and hands-on-steering wheel (drivers) are reported. The measurements were carried out under white noise vertical excitations of 0·25, 0·5 and 1·0m/s2r.m.s. acceleration magnitudes in the 0·5-40Hz frequency range and a track measured input (1·07m/s2). The measured data have been analyzed to study the effects of hands position, body mass, magnitude and type of vibration excitation, and feet position, on the biodynamic response expressed in terms of apparent mass. A comparison of the measured response of subjects assuming typical automotive postures involving inclined cushion, inclined backrest and full use of backrest support with data determined under different postural conditions and excitation levels revealed considerable differences. The biodynamic response of automobile occupants seated with hands in lap, peaks in the 6·5-8·6Hz frequency range, which is considerably higher than the reported range of fundamental frequencies (4·5-5Hz) in most other studies involving different experimental conditions. The peak magnitude tends to decrease considerably for the driving posture with hands-on-steering wheel, while a second peak in the 8-12 Hz range becomes more apparent for this posture. The results suggest that biodynamic response of occupants seated in automotive seats and subject to vertical vibration need to be characterized, as a minimum, by two distinct functions for passenger and driving postures. A higher body mass, in general, yields higher peak magnitude response and lower corresponding frequency for both postures. The strong dependence of the response on the body mass is further demonstrated by grouping the measured data into four different mass ranges: less than 60 kg, between 60·5 and 70 kg, between 70·5 and 80 kg, and above 80 kg. From the results, it is concluded that
Zhao, Xin; Geng, Qian; Li, Yueming
2013-03-01
This paper is a study of the vibration and acoustic response characteristics of orthotropic laminated composite plate with simple supported boundary conditions excited by a harmonic concentrated force in a hygroscopic environment. First the natural vibration of the plate with the in-plane forces induced by hygroscopic stress is obtained analytically. Secondly, the sound pressure distribution of the plate at the far field is obtained using the Rayleigh integral. Furthermore, the sound radiation efficiency is deduced. Third, different ratios of elastic modulus in material principal directions are set to research the effects of increasing stiffness of the orthotropic plate on the vibration and acoustic radiation characteristics. Finally, to verify the theoretical solution, numerical simulations are also carried out with commercial finite software. It is found that the natural frequencies decrease with the increase of the moisture content and the first two order modes interconvert at high moisture content. The dynamic response and sound pressure level float to lower frequencies with elevated moisture content. Acoustic radiation efficiency generally floats to the low frequencies and decreases with an increase of moisture content. The dynamic and acoustic responses reduce and the coincidence frequency decreases with the enhanced stiffness. PMID:23464015
Zhou, Zhen; Griffin, Michael J
2014-01-01
Frequency weightings for predicting vibration discomfort assume the same frequency-dependence at all magnitudes of vibration, whereas biodynamic studies show that the frequency-dependence of the human body depends on the magnitude of vibration. This study investigated how the frequency-dependence of vibration discomfort depends on the acceleration and the force at the subject-seat interface. Using magnitude estimation, 20 males and 20 females judged their discomfort caused by sinusoidal vertical acceleration at 13 frequencies (1-16 Hz) at magnitudes from 0.1 to 4.0 ms(-2) r.m.s. The frequency-dependence of their equivalent comfort contours depended on the magnitude of vibration, but was less dependent on the magnitude of dynamic force than the magnitude of acceleration, consistent with the biodynamic non-linearity of the body causing some of the magnitude-dependence of equivalent comfort contours. There were significant associations between the biodynamic responses and subjective responses at all frequencies in the range 1-16 Hz. Practitioner Summary: Vertical seat vibration causes discomfort in many forms of transport. This study provides the frequency-dependence of vibration discomfort over a range of vibration magnitudes and shows how the frequency weightings in the current standards can be improved. PMID:24730710
Dynamic characteristics analysis and vibration experiment of Upper-time of Flight Counter (U-ToFC)
NASA Astrophysics Data System (ADS)
Wu, Qiong; Zhang, Yidu; Song, Sunguang
2012-09-01
The dynamic characteristic parameters of Up-time of Flight Counter (U-ToFC) are important for research of structure optimization and reliability. However, the current simulation is performed based on homogenous material and simplified constraint model, the correct and reliability of results are difficult to be guaranteed. The finite element method based on identification of material parameters is proposed for this investigation on dynamic analysis, simulation and vibration experiment of the U-ToFC. The structure of the U-ToFC is complicated. Its' outside is made of aluminum alloy and inside contains electronic components such as capacitors, resistors, inductors, and integrated circuits. The accurate material parameters of model are identified difficultly. Hence, the parameters identification tests are performed to obtain the material parameters of this structure. On the basis of the above parameters, the experiment and FEA are conducted to the U-ToFC. In terms of the flight acceptance test level, and two kinds of joints condition between the U-ToFC and fixture are considered. The natural frequencies, vibration shapes and the response of the power spectral density of the U-ToFC are obtained. The results show simulation which is based on parameters identification is similar with vibration experiment in natural frequencies and responses. The errors are less than 10%. The vibration modes of simulation and experiment are consistent. The paper provides a more reliable computing method for the dynamic characteristic analysis of large complicated structure.
Analysis of proposed criteria for human response to vibration
NASA Technical Reports Server (NTRS)
Janeway, R. N.
1975-01-01
The development of criteria for human vibration response is reviewed, including the evolution of the ISO standard 2631. The document is analyzed to show why its application to vehicle ride evaluation is strongly opposed. Alternative vertical horizontal limits for comfort are recommended in the ground vehicle ride frequency range above 1 Hz. These values are derived by correlating the absorbed power findings of Pradko and Lee with other established criteria. Special emphasis is placed on working limits in the frequency range of 1 to 10 Hz since this is the most significant area in ground vehicle ride evaluation.
Modeling vibration response and damping of cables and cabled structures
NASA Astrophysics Data System (ADS)
Spak, Kaitlin S.; Agnes, Gregory S.; Inman, Daniel J.
2015-02-01
In an effort to model the vibration response of cabled structures, the distributed transfer function method is developed to model cables and a simple cabled structure. The model includes shear effects, tension, and hysteretic damping for modeling of helical stranded cables, and includes a method for modeling cable attachment points using both linear and rotational damping and stiffness. The damped cable model shows agreement with experimental data for four types of stranded cables, and the damped cabled beam model shows agreement with experimental data for the cables attached to a beam structure, as well as improvement over the distributed mass method for cabled structure modeling.
Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly
NASA Astrophysics Data System (ADS)
Huang, Ying; Yang, Shouping; Zhang, Fujun; Zhao, Changlu; Ling, Qiang; Wang, Haiyan
2012-07-01
Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines. The linear lumped mass method, which has been universally applied to the dynamic modeling of engine crankshaft assembly, reveals obvious simulation errors. The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness. In this paper, a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method. The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments. The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method. The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method. The simulation results are compared with a lumped mass model and a detailed model using the system matrix method. Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration, and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor. The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia. This research project is aimed at improving nonlinear dynamics theory, and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.
NASA Astrophysics Data System (ADS)
Ma, Chien-Ching; Lin, Hsien-Yang
2005-09-01
This study provides two non-contact optical techniques to investigate the transverse vibration characteristics of piezoceramic rectangular plates in resonance. These methods, including the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are full-field measurement for AF-ESPI and point-wise displacement measurement for LDV, respectively. The edges of these piezoceramic rectangular plates may either be fixed or free. Both resonant frequencies and mode shapes of vibrating piezoceramic plates can be obtained simultaneously by AF-ESPI. Excellent quality of the interferometric fringe patterns for the mode shapes is obtained. In the LDV system, a built-in dynamic signal analyzer (DSA) composed of DSA software and a plug-in waveform generator board can provide the piezoceramic plates with the swept-sine excitation signal, whose gain at corresponding frequencies is analyzed by the DSA software. The peaks appeared in the frequency response curve are resonant frequencies. In addition to these optical methods, the numerical computation based on the finite element analysis is used to verify the experimental results. Good agreements of the mode shapes and resonant frequencies are obtained for experimental and numerical results.
NASA Technical Reports Server (NTRS)
Decker, Arthur J.
2001-01-01
Artificial neural networks have been used for a number of years to process holography-generated characteristic patterns of vibrating structures. This technology depends critically on the selection and the conditioning of the training sets. A scaling operation called folding is discussed for conditioning training sets optimally for training feed-forward neural networks to process characteristic fringe patterns. Folding allows feed-forward nets to be trained easily to detect damage-induced vibration-displacement-distribution changes as small as 10 nm. A specific application to aerospace of neural-net processing of characteristic patterns is presented to motivate the conditioning and optimization effort.
NASA Astrophysics Data System (ADS)
Gurova, E. G.; Panchenko, Y. V.; Gurov, M. G.
2016-04-01
In this paper the method of calculation of neodymium magnets was presented. The calculation of the neodymium magnets characteristics and stiffness correctors of the vibration isolator according to the requirements for vibration isolation devices with stiffness compensators was performed. This research has been performed with the support of the President scholarship for young scientists, order No. 184 of Ministry of education and science of the Russian Federation of the 10th of March 2015.
NASA Technical Reports Server (NTRS)
Decker, Arthur J.
2001-01-01
At the NASA Glenn Research Center, we have been training artificial neural networks to interpret the characteristic patterns (see the leftmost image) generated from electronic holograms of vibrating structures. These patterns not only visualize the vibration properties of structures, but small changes in the patterns can indicate structural changes, cracking, or damage. Neural networks detect these small changes well. Our objective has been to adapt the neural-network, electronic-holography combination for inspecting components in Glenn's Spin Rig.
Vibration and Noise Characteristics of Elliptical Gears due to Non-Uniform Rotation
NASA Astrophysics Data System (ADS)
Liu, Xing; Nagamura, Kazuteru; Ikejo, Kiyotaka
Elliptical gear is a typical non-circular gear, which transmits a variable-ratio rotation and power simultaneously. Due to the non-uniform rotation, the vibration and noise of elliptical gears demonstrate particular characteristics which should be paid attention to in practical application. In this paper, two elliptical gears, which are a single elliptical gear and a double elliptical gear, have been investigated to analyze the vibration and noise characteristics of elliptical gears. The corresponding circular gears for comparison are also investigated. General factors including the torque, the rotation speed, the gear vibration acceleration and the gear noise of the four test gears are measured by running test. The root mean square of the Circumferential Vibration Acceleration (CVA) and the sound pressure level of the noise of elliptical gears are obtained from the measured results and compared with those of circular gears to clarify the vibration and noise characteristics of elliptical gears. Furthermore, the frequency analysis of the CVA of elliptical gears is conducted by Fast Fourier Transform Algorithm (FFT) and compared with that of circular gears. The main vibration component of elliptical gear is uncovered according to the obtained frequency spectra. In addition, the Critical Rotation Speeds of Tooth Separation (CRSTS) of elliptical gear is obtained and its relation with load torque is unveiled.
Thermal vibration characteristics of armchair boron-nitride nanotubes
Chandra, Anirban; Patra, Puneet Kumar; Bhattacharya, Baidurya
2015-12-21
A nanomechanical resonator based sensor works by detecting small changes in the natural frequency of the device in presence of external agents. In this study, we address the length and the temperature-dependent sensitivity of precompressed armchair Boron-Nitride nanotubes towards their use as sensors. The vibrational data, obtained using molecular dynamics simulations, are analyzed for frequency content through the fast Fourier transformation. As the temperature of the system rises, the vibrational spectrum becomes noisy, and the modal frequencies show a red-shift irrespective of the length of the nanotube, suggesting that the nanotube based sensors calibrated at a particular temperature may not function desirably at other temperatures. Temperature-induced noise becomes increasingly pronounced with the decrease in the length of the nanotube. For the shorter nanotube at higher temperatures, we observe multiple closely spaced peaks near the natural frequency, that create a masking effect and reduce the sensitivity of detection. However, longer nanotubes do not show these spurious frequencies, and are considerably more sensitive than the shorter ones.
Vibration Characteristics of Partially Covered Double-Sandwich Cantilever Beam
NASA Technical Reports Server (NTRS)
Chen, Qinghua; Levy, Cesar
1996-01-01
The differential equations of motion together with the boundary conditions for a partially covered, double-sandwich cantilever beam are derived. Bending and extension, rotational and longitudinal inertia of damping layers, and shear deformation and rotational and longitudinal inertia of the constraining layers and the primary beam are included in the equations. The theory is applicable for long as well as short, soft, or stiff damping layer, double-sandwich beams. Also, the effects of different parameters on the system loss factor and resonance frequency are discussed. Differences are found to exist with the previous beam model (called the Euler beam model) when the damping layers are stiff, when the thickness of the damping layer is large compared to the primary-beam thickness, and in the case of higher modes of vibration.
NASA Technical Reports Server (NTRS)
Bratanow, T.; Ecer, A.
1974-01-01
A theoretical investigation of structural vibration characteristics of rotor blades was carried out. Coupled equations of motion for flapwise bending and torsion were formulated for rotor blades with noncollinear elastic and mass axes. The finite element method was applied for a detailed representation of blade structural properties. Coupled structural mass and stiffness coefficients were evaluated. The range of validity of a set of coupled equations of motion linearized with respect to eccentricity between elastic and mass axes was investigated. The sensitivity of blade vibration characteristics to torsion were evaluated by varying blade geometric properties, boundary conditions, and eccentricities between mass and elastic axes.
NASA Astrophysics Data System (ADS)
Chandra, Ramesh; Chopra, Inderjit
1992-08-01
The objective of the study was to predict the effect of elastic couplings on the free vibration characteristics of thin-walled composite box beams and to correlate the results with experimental data. The free vibration characteristics of coupled thin-walled composite beams under rotation were determined using the Galerkin method. The theoretical results were found to be in satisfactory agreement with experimental data obtained for graphite/epoxy, kevlar/epoxy, and glass/epoxy composite beams in an in-vacuo test facility at different rotational speeds.
Novotný, Tomáš; Belzig, Wolfgang
2015-01-01
We study analytically the Full Counting Statistics of the charge transport through a nanosystem consisting of a few electronic levels weakly coupled to a discrete vibrational mode. In the limit of large transport voltage bias the cumulant generating function can be evaluated explicitly based solely on the intuitive physical arguments and classical master equation description of the vibration mode. We find that for the undamped vibrational modes mutual dynamical interplay between electronic and vibronic degrees of freedom leads to strongly nonlinear (in voltage) transport characteristics of the nanosystem. In particular, we find that for large voltages the k-th cumulant of the current grows as V (2k) to be contrasted with the linear dependence in case of more strongly externally damped and thus thermalized vibrational modes. PMID:26425436
Belzig, Wolfgang
2015-01-01
Summary We study analytically the Full Counting Statistics of the charge transport through a nanosystem consisting of a few electronic levels weakly coupled to a discrete vibrational mode. In the limit of large transport voltage bias the cumulant generating function can be evaluated explicitly based solely on the intuitive physical arguments and classical master equation description of the vibration mode. We find that for the undamped vibrational modes mutual dynamical interplay between electronic and vibronic degrees of freedom leads to strongly nonlinear (in voltage) transport characteristics of the nanosystem. In particular, we find that for large voltages the k-th cumulant of the current grows as V 2k to be contrasted with the linear dependence in case of more strongly externally damped and thus thermalized vibrational modes. PMID:26425436
Evaluation of human response to structural vibrations induced by sonic booms
NASA Technical Reports Server (NTRS)
Sutherland, Louis C.; Czech, J.
1992-01-01
The topic is addressed of building vibration response to sonic boom and the evaluation of the associated human response to this vibration. An attempt is made to reexamine some of the issues addressed previously and to offer fresh insight that may assist in reassessing the potential impact of sonic boom over populated areas. Human response to vibration is reviewed first and a new human vibration response criterion curve is developed as a function of frequency. The difference between response to steady state versus impulsive vibration is addressed and a 'vibration exposure' or 'vibration energy' descriptor is suggested as one possible way to evaluate duration effects on response to transient vibration from sonic booms. New data on the acoustic signature of rattling objects are presented along with a review of existing data on the occurrence of rattle. Structural response to sonic boom is reviewed and a new descriptor, 'Acceleration Exposure Level' is suggested which can be easily determined from the Fourier Spectrum of a sonic boom. A preliminary assessment of potential impact from sonic booms is provided in terms of human response to vibration and detection of rattle based on a synthesis of the preceding material.
A study of vibration characteristics on a luxury wheelchair and a new prototype wheelchair
NASA Astrophysics Data System (ADS)
Hostens, I.; Papaioannou, Y.; Spaepen, A.; Ramon, H.
2003-09-01
The transmission of wheelchair vibrations to the body will influence comfort, performance and the long-term health of the user. Improved knowledge of vibration transmissibility and its variability enhances our understanding of various human responses to vibration. In this study, an outdoor experiment and an experiment with vibration simulation using two wheelchairs (high-quality models of a new prototype wheelchair taken from two different stages of the iterative production procedure) were performed. The study confirms that the human body is very sensitive to the frequency range of 0.5- 10 Hz, as found in the literature. Both wheelchairs equipped with passive suspension system did not perform adequately in this frequency range and even amplified the input signal at the resonance frequency (3- 4.5 Hz). As the risk of physical damage is not likely to improve with these wheelchair suspension systems, the future depends on new designs with higher low-frequency comfort and affordable additional costs.
Li, Junying; Zhu, Yong Wang, Ning; Zhang, Jie; Wang, Xin
2014-07-14
In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 μm, 20.90 μm, 30.19 μm, and 39.98 μm respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ∼ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.
NASA Astrophysics Data System (ADS)
Li, Junying; Zhu, Yong; Wang, Xin; Wang, Ning; Zhang, Jie
2014-07-01
In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 μm, 20.90 μm, 30.19 μm, and 39.98 μm respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ˜ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.
The responses of human muscle spindle endings to vibration of non-contracting muscles.
Burke, D; Hagbarth, K E; Löfstedt, L; Wallin, B G
1976-01-01
1. In micro-electrode recordings from the human peroneal and tibial nerves, the responses of thirty-two primary spindle endings, thirteen secondary spindle endings and three Golgi tendon organs were studied during vibration of the tendons of the receptor-bearing muscles in the leg. The amplitude of the applied vibration was 1-5 mm and the frequency was varied from 20 to 220 Hz. As checked with e.m.g. and torque measurements, the muscles of the leg were relaxed during the sequences analysed. 2. Providing that the vibrator was accurately applied, all endings responded with discharges phase-locked to the vibration cycles, the discharge rates being at the vibration frequency or at subharmonics of that frequency. The response to vibration was of abrupt onset and offset, was maintained for the duration of vibration, and was not subject to fluctuation with changes in attention or with remote muscle contraction. 3. The maximal discharge rate that could be achieved varied from one ending to the next, and increased with the length of the receptor-bearing muscle. For endings driven at their maximal rate an increase in vibration frequency produced a decrease in discharge rates as the ending changed to a subharmonic pattern of response. The converse occurred on decreasing vibration frequency. 4. For any given muscle length, primary endings could generally be driven to higher rates than secondary endings but there was a wide range of responsiveness within each group and a significant overlap between the groups. At medium muscle length, the most responsive primary endings could be driven up to 220 Hz but secondary endings did not reach discharge rates higher than 100 Hz. 5. With combined vibration and passive movements, primary endings exhibited maximal vibration responsiveness during the stretching phases, sometimes firing twice per vibration cycle. During the shortening phases, however, they usually ceased responding to the vibratory stimulus. The vibration responsiveness of
Acceleration response spectrum for predicting floor vibration due to occupant walking
NASA Astrophysics Data System (ADS)
Chen, Jun; Xu, Ruotian; Zhang, Mengshi
2014-07-01
Annoying vibrations caused by occupant walking is an important serviceability problem for long-span floors. At the design stage the floor's structural arrangement may frequently change to cater for the owner's varying requirements. An efficient and accurate approach for predicting a floor's acceleration response is thus of great significance. This paper presents a design-oriented acceleration response spectrum for calculating a floor's response given the floor's modal characteristics and a specified confidence level. 2204 measured footfall traces from 61 test subjects were used to generate 10 s peak root-mean-square acceleration response spectra, on which a piecewise mathematical representation is based. The proposed response spectrum consists of three main parts: the first harmonic plateau ranging from 1.5 to 2.5 Hz, the second harmonic plateau ranging from 3.0 to 5.0 Hz and the descending part going with frequencies from 5.0 to 10.0 Hz. The representative value of each plateau and the mathematical representation for the descending curve were determined statistically for different confidence levels. Furthermore, the effects of factors, such as floor span, occupant stride length, higher modes of vibration, boundary conditions and peak acceleration response, on the proposed spectrum have been investigated and a modification measure for each factor is suggested. A detailed application procedure for the proposed spectrum approach is presented and has been applied to four existing floors to predict their acceleration responses. Comparison between predicted and field measured responses shows that the measured accelerations of the four floors are generally close to or slightly higher than the predicted values for the 75 percent confidence level, but are all lower than the predicted values for the 95 percent confidence level. Therefore the suggested spectrum-based approach can be used for predicting a floor's response subject to a single person walking.
Neural-Net Processing of Characteristic Patterns From Electronic Holograms of Vibrating Blades
NASA Technical Reports Server (NTRS)
Decker, Arthur J.
1999-01-01
Finite-element-model-trained artificial neural networks can be used to process efficiently the characteristic patterns or mode shapes from electronic holograms of vibrating blades. The models used for routine design may not yet be sufficiently accurate for this application. This document discusses the creation of characteristic patterns; compares model generated and experimental characteristic patterns; and discusses the neural networks that transform the characteristic patterns into strain or damage information. The current potential to adapt electronic holography to spin rigs, wind tunnels and engines provides an incentive to have accurate finite element models lor training neural networks.
NASA Technical Reports Server (NTRS)
Decker, Arthur J. (Inventor)
2006-01-01
An artificial neural network is disclosed that processes holography generated characteristic pattern of vibrating structures along with finite-element models. The present invention provides for a folding operation for conditioning training sets for optimally training forward-neural networks to process characteristic fringe pattern. The folding pattern increases the sensitivity of the feed-forward network for detecting changes in the characteristic pattern The folding routine manipulates input pixels so as to be scaled according to the location in an intensity range rather than the position in the characteristic pattern.
Free vibration and dynamic response analysis of spinning structures
NASA Technical Reports Server (NTRS)
1986-01-01
The proposed effort involved development of numerical procedures for efficient solution of free vibration problems of spinning structures. An eigenproblem solution procedure, based on a Lanczos method employing complex arithmetic, was successfully developed. This task involved formulation of the numerical procedure, FORTRAN coding of the algorithm, checking and debugging of software, and implementation of the routine in the STARS program. A graphics package for the E/S PS 300 as well as for the Tektronix terminals was successfully generated and consists of the following special capabilities: (1) a dynamic response plot for the stresses and displacements as functions of time; and (2) a menu driven command module enabling input of data on an interactive basis. Finally, the STARS analysis capability was further improved by implementing the dynamic response analysis package that provides information on nodal deformations and element stresses as a function of time. A number of test cases were run utilizing the currently developed algorithm implemented in the STARS program and such results indicate that the newly generated solution technique is significantly more efficient than other existing similar procedures.
NASA Technical Reports Server (NTRS)
Gohlka, Werner
1943-01-01
The exploration of the processes accompanying engine combustion demands quick-responding pressure-recording instruments, among which the piezoelectric type has found widespread use because of its especially propitious properties as vibration-recording instruments for high frequencies. Lacking appropriate test methods, the potential errors of piezoelectric recorders in dynamic measurements could only be estimated up to now. In the present report a test method is described by means of which the resonance curves of the piezoelectric pickup can be determined; hence an instrumental appraisal of the vibration characteristics of piezoelectric recorders is obtainable.
Dynamic characteristics of vibration isolation platforms considering the joints of the struts
NASA Astrophysics Data System (ADS)
Zhang, Jingrui; Guo, Zixi; Zhang, Yao
2016-09-01
This paper discusses the dynamic characteristics of the impacts and corresponding frictions generated by the clearances of joints of vibration isolation platforms for control moment gyroscopes (CMGs) on spacecraft. A contact force model is applied using a nonlinear contact force model, and the frictions in the joints are considered in the dynamic analysis. First, the dynamic characteristics of a single isolation strut with spherical joints were studied, and joints with different initial clearance sizes were separately analyzed. Then, dynamic models of the vibration isolation platform for a CMG cluster with both perfect joints and joints with clearances were established. During the numeral simulation, joints with different elastic moduli were used to study the nonlinear characteristics. Finally, the distributions of the collision points, which can serve as a reference for the reliability and lifetime of a platform, were given.
Human response to house vibrations caused by sonic booms or air blasts.
Schomer, P D
1978-07-01
Descriptions of the effects of sonic booms of air blasts by observers in buildings have included such statements as "noticeable vibrations" in addition to phrases such as "the house rattles," "the windows rattle," or "bric-à-brac rattles." Analysis of studies of human response to vibrations, vibration complaints in the Toronto area, special tests by Kryter at Edwards Air Force Base, and laboratory studies of human response to sonic booms show that perceived vibration is not normally a factor that contributes significantly to human response to airborne, large-amplitude impulse noise. Rather, human response is solely the result of the impulse noise itself and of audible noise due to induced radiation from vibrating surfaces. PMID:711997
NASA Astrophysics Data System (ADS)
Toward, Martin G. R.; Griffin, Michael J.
2011-12-01
The transmission of vibration through a seat depends on the impedance of the seat and the apparent mass of the seat occupant. This study was designed to determine how factors affecting the apparent mass of the body (age, gender, physical characteristics, backrest contact, and magnitude of vibration) affect seat transmissibility. The transmission of vertical vibration through a car seat was measured with 80 adults (41 males and 39 females aged 18-65) at frequencies between 0.6 and 20 Hz with two backrest conditions (no backrest and backrest), and with three magnitudes of random vibration (0.5, 1.0, and 1.5 m s -2 rms). Linear regression models were used to study the effects of subject physical characteristics (age, gender, and anthropometry) and features of their apparent mass (resonance frequency, apparent mass at resonance and at 12 Hz) on the measured seat transmissibility. The strongest predictor of both the frequency of the principal resonance in seat transmissibility and the seat transmissibility at resonance was subject age, with other factors having only marginal effects. The transmissibility of the seat at 12 Hz depended on subject age, body mass index, and gender. Although subject weight was strongly associated with apparent mass, weight was not strongly associated with seat transmissibility. The resonance frequency of the seat decreased with increases in the magnitude of the vibration excitation and increased when subjects made contact with the backrest. Inter-subject variability in the resonance frequency and transmissibility at resonance was less with greater vibration excitation, but was largely unaffected by backrest contact. A lumped parameter seat-person model showed that changes in seat transmissibility with age can be predicted from changes in apparent mass with age, and that the dynamic stiffness of the seat appeared to increase with increased loading so as to compensate for increases in subject apparent mass associated with increased sitting
Kim, Heon-Jeong; Martin, Bernard J
2013-02-01
Simulation of human movements is an essential component for proactive ergonomic analysis and biomechanical model development (Chaffin, 2001). Most studies on reach kinematics have described human movements in a static environment, however the models derived from these studies cannot be applied to the analysis of human reach movements in vibratory environments such as in-vehicle operations. This study analyzes three-dimensional joint kinematics of the upper extremity in reach movements performed in static and specific vibratory conditions and investigates vibration transmission to shoulder, elbow, and hand along the body path during pointing tasks. Thirteen seated subjects performed reach movements to five target directions distributed in their right hemisphere. The results show similarities in the characteristics of movement patterns and reach trajectories of upper body segments for static and dynamic environments. In addition, vibration transmission through upper body segments is affected by vibration frequency, direction, and location of the target to be reached. Similarities in the pattern of movement trajectories revealed by filtering vibration-induced oscillations indicate that coordination strategy may not be drastically different in static and vibratory environments. This finding may facilitate the development of active biodynamic models to predict human performance and behavior under whole body vibration exposure. PMID:22814094
Transcriptional Pathways Altered in Response to Vibration in a Model of Hand-Arm Vibration Syndrome
Waugh, Stacey; Kashon, Michael L.; Li, Shengqiao; Miller, Gerome R.; Johnson, Claud; Krajnak, Kristine
2016-01-01
Objective The aim of this study was to use an established model of vibration-induced injury to assess frequency-dependent changes in transcript expression in skin, artery, and nerve tissues. Methods Transcript expression in tissues from control and vibration-exposed rats (4 h/day for 10 days at 62.5, 125, or 250 Hz; 49 m/s2, rms) was measured. Transcripts affected by vibration were used in bioinformatics analyses to identify molecular- and disease-related pathways associated with exposure to vibration. Results Analyses revealed that cancer-related pathways showed frequency-dependent changes in activation or inhibition. Most notably, the breast-related cancer-1 pathway was affected. Other pathways associated with breast cancer type 1 susceptibility protein related signaling, or associated with cancer and cell cycle/cell survivability were also affected. Conclusion Occupational exposure to vibration may result in DNA damage and alterations in cell signaling pathways that have significant effects on cellular division. PMID:27058473
Characteristic of torsional vibration of mill main drive excited by electromechanical coupling
NASA Astrophysics Data System (ADS)
Zhang, Yifang; Yan, Xiaoqiang; Lin, Qihui
2016-01-01
In the study of electromechanical coupling vibration of mill main drive system, the influence of electrical system on the mechanical transmission is considered generally, however the research for the mechanism of electromechanical interaction is lacked. In order to research the electromechanical coupling resonance of main drive system on the F3 mill in a plant, the cycloconverter and synchronous motor are modeled and simulated by the MTLAB/SIMULINK firstly, simulation result show that the current harmonic of the cycloconverter can lead to the pulsating torque of motor output. Then the natural characteristics of the mechanical drive system are calculated by ANSYS, the result show that the modal frequency contains the component which is close to the coupling vibration frequency of 42Hz. According to the simulation result of the mechanical and electrical system, the closed loop feedback model including the two systems are built, and the mechanism analysis of electromechanical coupling presents that there is the interaction between the current harmonic of electrical system and the speed of the mechanical drive system. At last, by building and computing the equivalent nonlinear dynamics model of the mechanical drive system, the dynamic characteristics of system changing with the stiffness, damping coefficient and the electromagnetic torque are obtained. Such electromechanical interaction process is suggested to consider in research of mill vibration, which can induce strong coupling vibration behavior in the rolling mill drive system.
NASA Technical Reports Server (NTRS)
Zeveleanu, C.
1974-01-01
The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.
Pedersen, Eja
2015-01-01
Urban densification increases exposure to noise, light, odour, and vibration in urban dwellings. Exposure from combined environmental stressors intruding into the home could increase the risk of adverse effects on wellbeing, even when the exposure is at a relatively low level. This study assesses the prevalence of annoyance with a combination of potential environmental stressors common in urban areas and the association with wellbeing. A questionnaire was sent by mail to residents in five areas in Halmstad (Sweden) with similar socioeconomic and housing characteristics but different exposure (response rate 56%; n = 385). Of the respondents, 50% were annoyed to some degree by at least one of the suggested stressors, most commonly by noise and vibration from local traffic. Structural equation modelling showed that annoyance led to lowered quality of life via the mediating construct residential satisfaction, which in turn was influenced by place attachment and perceived restoration possibilities in the dwelling. Stress had a negative impact on quality of life, but was not directly correlated to annoyance. Stress was however correlated with sensitivity. The findings suggest that dose-response relationships for environmental stressors should be studied in a broader context of environmental and individual factors. Also relatively low levels of exposure should be mitigated, especially if several stressors are present. PMID:25794188
The bio-response of osteocytes and its regulation on osteoblasts under vibration.
Wu, Xin-Tong; Sun, Lian-Wen; Qi, Hong-Yu; Shi, Hao; Fan, Yu-Bo
2016-04-01
Vibration, especially at low magnitude and high frequency (LMHF), was demonstrated to be anabolic for bone, but how the LMHF vibration signal is perceived by osteocytes is not fully studied. On the other hand, the mechanotransduction of osteocytes under shear stress has been scientists' primary focus for years. Due to the small strain caused by low-magnitude vibration, whether the previous explanation for shear stress will still work for LMHF vibration is unknown. In this study, a finite element method (FEM) model based on the real geometrical shape of an osteocyte was built to compare the mechanical behaviors of osteocytes under LMHF vibration and shear stress. The bio-response of osteocytes to vibration under different frequencies, including the secretion of soluble factors and the concentration of intracellular calcium, were studied. The regulating effect of the conditioned medium (CM) from vibrated osteocytes on osteoblasts was also studied. The FEM analysis result showed the cell membrane deformation under LMHF vibration was very small (with a peak value of 1.09%) as compared to the deformation caused by shear stress (with a peak value of 6.65%). The F-actin stress fibers of osteocytes were reorganized, especially on the nucleus periphery after LMHF vibration. The vibration at 30 Hz has a promoting effect on osteocytes and the osteogenesis of osteoblasts, whereas vibration at 90 Hz was suppressive. These results lead to a conclusion that the bio-response of osteocytes to LMHF vibration is frequency-dependent and is more related to the cytoskeleton on nuclear periphery rather than the membrane deformation. PMID:26715381
Estimations of the smoothing operator response characteristics
NASA Technical Reports Server (NTRS)
Yatskiv, Y. S.
1974-01-01
The mean response characteristic of the graphical smoothing method is discussed. The method is illustrated by analysis of latitude observations at Washington from 1915.9 to 1941.0. Spectral density, frequency distribution, and distribution functions are also discussed.
Cocroft, R B; Tieu, T D; Hoy, R R; Miles, R N
2000-01-01
The use of substrate vibrations in communication and predator-prey interactions is widespread in arthropods. In many contexts, localization of the vibration source plays an important role. For small species on solid substrates, time and amplitude differences between receptors in different legs may be extremely small, and the mechanisms of vibration localization are unclear. Here we ask whether directional information is contained in the mechanical response of an insect's body to substrate vibration. Our study species was a membracid treehopper (Umbonia crassicornis) that communicates using bending waves in plant stems. We used a bending-wave simulator that allows precise control of the frequency, intensity and direction of the vibrational stimulus. With laser-Doppler vibrometry, we measured points on the substrate and on the insect's thorax and middle leg. Transfer functions showing the response of the body relative to the substrate revealed resonance at lower frequencies and attenuation at higher frequencies. There were two modes of vibration along the body's long axis, a translational and a rotational mode. Furthermore, the transfer functions measured on the body differed substantially depending on whether the stimulus originated in front of or behind the insect. Directional information is thus available in the mechanical response of the body of these insects to substrate vibration. These results suggest a vibration localization mechanism that could function at very small spatial scales. PMID:11016785
NASA Astrophysics Data System (ADS)
Wang, Jie; Zhao, Shougen; Wu, Dafang; Jing, Xingjian
2016-01-01
Micro-vibration isolation is a hot topic in spacecraft vibration control, and fluid based vibration isolators alternatively provide a good and reliable solution to this challenging issue. In this paper, a novel fluid based micro-vibration isolator (FBMVI) is investigated. According to its inherent working principle and deformation pattern, the generation mechanisms of the damping and stiffness characteristics are derived, which are nonlinear functions of the environmental temperature. Then a lumped parameter model which is expressed by the physical design parameters (PDPs) is constructed, and the corresponding performance objective indices (POIs) are also obtained by applying the equivalence of mechanical impedance. Based on the finite element analysis of the internal damping component, a single variable method is further adopted to carry out the parametric study, and the influences of each PDP on the POIs are analyzed in details. Finally, experiments are conducted to identify the variation of fluid bulk modulus with the outside environmental temperature, and to validate the performance of the isolator under different temperature environments. The tested results show great consistence compared with the predicted tendencies of the parametric study. The results of this study can provide a very useful insight into and/or an important guidance for the design and application of this type of FBMVIs in engineering practice.
NASA Technical Reports Server (NTRS)
Green, C.
1971-01-01
Guidelines of the methods and applications used in vibration technology at the MSFC are presented. The purpose of the guidelines is to provide a practical tool for coordination and understanding between industry and government groups concerned with vibration of systems and equipments. Topics covered include measuring, reducing, analyzing, and methods for obtaining simulated environments and formulating vibration specifications. Methods for vibration and shock testing, theoretical aspects of data processing, vibration response analysis, and techniques of designing for vibration are also presented.
Flight and Analytical Methods for Determining the Coupled Vibration Response of Tandem Helicopters
NASA Technical Reports Server (NTRS)
Yeates, John E , Jr; Brooks, George W; Houbolt, John C
1957-01-01
Chapter one presents a discussion of flight-test and analysis methods for some selected helicopter vibration studies. The use of a mechanical shaker in flight to determine the structural response is reported. A method for the analytical determination of the natural coupled frequencies and mode shapes of vibrations in the vertical plane of tandem helicopters is presented in Chapter two. The coupled mode shapes and frequencies are then used to calculate the response of the helicopter to applied oscillating forces.
Teacher Characteristics for Culturally Responsive Pedagogy
ERIC Educational Resources Information Center
Rychly, Laura; Graves, Emily
2012-01-01
Culturally responsive pedagogy, as defined by one of the most prominent authors in the field, Geneva Gay (2002), is "using the cultural characteristics, experiences, and perspectives of ethnically diverse students as conduits for teaching them more effectively". Culturally responsive pedagogy can be thought of, then, as teaching practices that…
NASA Astrophysics Data System (ADS)
Abbas, Laith K.; Zhou, Qinbo; Hendy, Hossam; Rui, Xiaoting
2015-08-01
The analysis of natural vibration characteristics has become one of important steps of the manufacture and dynamic design in the aerospace industry. This paper presents a new scenario called virtual cutting in the context of the transfer matrix method of linear multibody systems closed-loop topology for computing the free vibration characteristics of elastically coupled flexible launch vehicle boosters. In this approach, the coupled system is idealized as a triple-beam system-like structure coupled by linear translational springs, where a non-uniform free-free Euler-Bernoulli beam is used. A large thrust-to-weight ratio leads to large axial accelerations that result in an axial inertia load distribution from nose to tail. Consequently, it causes the development of significant compressive forces along the length of the launch vehicle. Therefore, it is important to take into account this effect in the transverse vibration model. This scenario does not need the global dynamics equations of a system, and it has high computational efficiency and low memory requirements. The validity of the presented scenario is achieved through comparison to other approaches published in the literature.
Responses of the frog primary vestibular afferents to direct vibration of the semicircular canal
NASA Technical Reports Server (NTRS)
Orlov, I. V.
1980-01-01
Responses of primary afferents (PA) of lateral semicircular canal to sinusoidal vibration of the canal wall within the range 0.05-200 Hz (mean amplitudes 5-15 microns) in immobilized frogs were studied. Dynamic characteristics (gain, phase) of relative linear velocity of the vibrator (micron X/s) were examined. At 0.2 Hz, the gain was 5.35 + or - 3.19 imp X/s /micron X/s (mean; S.D.; n=14) and linearly decreased if the frequency rose. Phase lag of relative velocity at 0.05 Hz was 49.8 deg + or - 16.5 deg (n=13) and at 1 Hz 97 deg + or - 9.4 deg (n=22). At 100 Hz phase lag was about 240 deg. Three groups of PA are described: wide range PA reacting in the range from 0.05 up to 60-180 Hz; high frequency PA responding in the range from 20-40 up to 100-150 Hz; and low frequency PA responding in the range from 0.05 up to 2-20 Hz.
NASA Astrophysics Data System (ADS)
Kaewunruen, Sakdirat; Remennikov, Alex M.
2006-11-01
The vibration of in situ concrete sleepers in a railway track structure is a major factor causing cracking of prestressed concrete sleepers and excessive railway track maintenance cost. Not only does the ballast interact with the sleepers, but the rail pads also take part in affecting their free vibration characteristics. This paper presents a sensitivity analysis of free vibration behaviors of an in situ railway concrete sleeper (standard gauge sleeper), incorporating sleeper/ballast interaction, subjected to the variations of rail pad properties. Through finite element analysis, Timoshenko-beam and spring elements were used in the in situ railway concrete sleeper modeling. This model highlights the influence of rail pad parameters on the free vibration characteristics of in situ sleepers. In addition, information on the first five flexural vibration modes indicates the dynamic performance of railway track when using different types of rail pads, as it plays a vital role in the cracking deterioration of concrete sleepers.
Vibration and flutter characteristics of the SR7L large-scale propfan
NASA Technical Reports Server (NTRS)
August, Richard; Kaza, Krishna Rao V.
1988-01-01
An investigation of the vibration characteristics and aeroelastic stability of the SR7L Large-Scale Advanced Propfan was performed using a finite element blade model and an improved aeroelasticity code. Analyses were conducted for different blade pitch angles, blade support conditions, number of blades, rotational speeds, and freestream Mach numbers. A finite element model of the blade was used to determine the blade's vibration behavior and sensitivity to support stiffness. The calculated frequencies and mode shape obtained with this model agreed well with the published experimental data. A computer code recently developed at NASA Lewis Research Center and based on three-dimensional, unsteady, lifting surface aerodynamic theory was used for the aeroelastic analysis to examine the blade's stability at a cruise condition of Mach 0.8 at 1700 rpm. The results showed that the blade is stable for that operating point. However, a flutter condition was predicted if the cruise Mach number was increased to 0.9.
Vibration responses of h-BN sheet to charge doping and external strain
Yang, Wei; Yang, Yu; Zheng, Fawei; Zhang, Ping
2013-12-07
Based on density functional theory and density functional perturbation theory calculations, we systematically investigate the vibration responses of h-BN sheet to charge doping and external strains. It is found that under hole doping, the phonon frequencies of the ZO and TO branches at different wave vector q shift linearly with different slopes. Under electron doping, although the phonon frequencies shift irregularly, the shifting values are different at different phonon wave vectors. Interestingly, we find that external strain can restrain the irregular vibration responses of h-BN sheet to electron doping. The critical factor is revealed to be the relative position of the nearly free electron and boron p{sub z} states of h-BN sheet. Under external strains, the vibration responses of h-BN sheet are also found to be highly dependent on the phonon branches. Different vibration modes at different q points are revealed to be responsible for the vibration responses of h-BN sheet to charge doping and external strain. Our results point out a new way to detect the doping or strain status of h-BN sheet by measuring the vibration frequencies at different wave vector.
Design and analysis of vibration energy harvesters based on peak response statistics
NASA Astrophysics Data System (ADS)
Adhikari, S.; Friswell, M. I.; Litak, G.; Haddad Khodaparast, H.
2016-06-01
Energy harvesting using cantilever piezoelectric vibration energy harvesters excited by Gaussian broadband random base excitation is considered. The optimal design and analysis of energy harvesters under random excitation is normally performed using the mean and standard deviation of a response quantity of interest, such as the voltage. An alternative approach based on the statistics of the peak voltage is developed in this paper. Three extreme response characteristics, namely (a) level crossing, (b) response peaks above certain level, and (c) fractional time spend above a certain level, have been employed. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions have been derived for number of level crossings, statistics of response peaks and fractional time spend above a certain level for the output voltage. It is shown that these quantities can be related to the standard deviation of the voltage and its derivative with respect to time. Direct numerical simulation has been used to validate the analytical expressions. Based on the analytical results, closed-form expressions for optimal system parameters have been proposed. Numerical examples are given to illustrate the applicability of the analytical results.
NASA Astrophysics Data System (ADS)
Tsujino, Jiromaru; Ueoka, Tetsugi; Kikuchi, Yuya
2004-05-01
The configurations of large-capacity 27 kHz ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. Ultrasonic complex vibration systems are effective for various types of metal welding and essential for new applications in various industries. The large-capacity vibration source consists of a complex transverse rod with a welding tip (titanium alloy), a complex vibration rod with a flange and a stepped part for holding the system (stainless-steel), a one-wavelength longitudinal vibration disk (aluminum alloy) and six bolt-clamped Langevin type piezo-electric ceramic (PZT) transducers (BLTs) installed along the circumference of the disk at an angle difference of 60°. The vibration source is driven using three driving systems with three transformers at a phase difference of 120°, and the disk is driven in a circular locus. The transverse vibration rod installed at the center of the disk is driven transversally and the welding tip of the rod vibrates in a circular locus.
Vibration-Induced Motor Responses of Infants With and Without Myelomeningocele
Teulier, Caroline; Smith, Beth A.; Kim, Byungji; Beutler, Benjamin D.; Martin, Bernard J.; Ulrich, Beverly D.
2012-01-01
Background The severity of myelomeningocele (MMC) stems both from a loss of neurons due to neural tube defect and a loss of function in viable neurons due to reduced movement experience during the first year after birth. In young infants with MMC, the challenge is to reinforce excitability and voluntary control of all available neurons. Muscle vibration paired with voluntary movement may increase motoneuron excitability and contribute to improvements in neural organization, responsiveness, and control. Objectives This study examined whether infants with or without MMC respond to vibration by altering their step or stance behavior when supported upright on a treadmill. Design This was a cross-sectional study. Methods Twenty-four 2- to 10-month-old infants, 12 with typical development (TD) and 12 with MMC (lumbar and sacral lesions), were tested. Infants were supported upright with their feet in contact with a stationary or moving treadmill during 30-second trials. Rhythmic alternating vibrations were applied to the right and left rectus femoris muscles, the lateral gastrocnemius muscle, or the sole of the foot. Two cameras and behavior coding were used to determine step count, step type, and motor response to vibration onset. Results Step count decreased and swing duration increased in infants with TD during vibration of the sole of the foot on a moving treadmill (FT-M trials). Across all groups the percentage of single steps increased during vibration of the lateral gastrocnemius muscle on a moving treadmill. Infants with MMC and younger infants with TD responded to onset of vibration with leg straightening during rectus femoris muscle stimulation and by stepping during FT-M trials more often than older infants with TD. Conclusions Vibration seems a viable option for increasing motor responsiveness in infants with MMC. Follow-up studies are needed to identify optimal methods of administering vibration to maximize step and stance behavior in infants. PMID:22228610
Influence of tyre-road contact model on vehicle vibration response
NASA Astrophysics Data System (ADS)
Múčka, Peter; Gagnon, Louis
2015-09-01
The influence of the tyre-road contact model on the simulated vertical vibration response was analysed. Three contact models were compared: tyre-road point contact model, moving averaged profile and tyre-enveloping model. In total, 1600 real asphalt concrete and Portland cement concrete longitudinal road profiles were processed. The linear planar model of automobile with 12 degrees of freedom (DOF) was used. Five vibration responses as the measures of ride comfort, ride safety and dynamic load of cargo were investigated. The results were calculated as a function of vibration response, vehicle velocity, road quality and road surface type. The marked differences in the dynamic tyre forces and the negligible differences in the ride comfort quantities were observed among the tyre-road contact models. The seat acceleration response for three contact models and 331 DOF multibody model of the truck semi-trailer was compared with the measured response for a known profile of test section.
Nondestructive Evaluation of Ceramic Candle Filters Using Vibration Response
Chen, Roger H. L.; Kiriakidis, Alejandro C.; Peng, Steve W.
1997-07-01
This study aims at the development of an effective nondestructive evaluation technique to predict the remaining useful life of a ceramic candle filter during a power plant's annual maintenance shutdown. The objective of the present on-going study is to establish the vibration signatures of ceramic candle filters at varying degradation levels due to different operating hours, and to study the various factors involving the establishment of the signatures.
NASA Astrophysics Data System (ADS)
Xueqian, Chen; Zhanpeng, Shen; Qinshu, He; Qiang, Du; Xin'en, Liu
2016-09-01
Rubber isolators are widely used in engineering structures, which often exhibit some nonlinearity and uncertainty properties subjected to different environment exciting. In order to study the nonlinear characteristic and uncertainty of a rubber isolator system, the sin-sweep vibration tests with different base exciting level are carried out firstly. Then a single freedom degree mass-spring-damper model is introduced to simplify the rubber isolator system. In the theory model, the spring and the damper are represented by polynomial functions of the relative displacement. The coefficients in the functions are identified by the test data, while the uncertainties of the coefficients are quantified by the principal components analysis (PCA) and Monte Carlo (MC) simulations. The major resonant frequencies and the damping ratios of the isolation system are calculated according to the theory model, the amplitude-frequency nonlinear characteristics are simulated by Runge-Kutta numerical method. The simulation results agree well with the experimental results, which indicate that the nonlinear model and the uncertainty quantifying results are feasible to predict the vibration characteristic and uncertainty of the isolation systems.
Characteristics of steady vibration in a rotating hub-beam system
NASA Astrophysics Data System (ADS)
Zhao, Zhen; Liu, Caishan; Ma, Wei
2016-02-01
A rotating beam features a puzzling character in which its frequencies and modal shapes may vary with the hub's inertia and its rotating speed. To highlight the essential nature behind the vibration phenomena, we analyze the steady vibration of a rotating Euler-Bernoulli beam with a quasi-steady-state stretch. Newton's law is used to derive the equations governing the beam's elastic motion and the hub's rotation. A combination of these equations results in a nonlinear partial differential equation (PDE) that fully reflects the mutual interaction between the two kinds of motion. Via the Fourier series expansion within a finite interval of time, we reduce the PDE into an infinite system of a nonlinear ordinary differential equation (ODE) in spatial domain. We further nondimensionalize the ODE and discretize it via a difference method. The frequencies and modal shapes of a general rotating beam are then determined numerically. For a low-speed beam where the ignorance of geometric stiffening is feasible, the beam's vibration characteristics are solved analytically. We validate our numerical method and the analytical solutions by comparing with either the past experiments or the past numerical findings reported in existing literature. Finally, systematic simulations are performed to demonstrate how the beam's eigenfrequencies vary with the hub's inertia and rotating speed.
Study on vibration characteristics of the shaft system for a dredging pump based on FEM
NASA Astrophysics Data System (ADS)
Zhai, L. M.; Qin, L.; Liu, C. Y.; Liu, X.; He, L. Y.; He, Y.; Wang, Z. W.
2012-11-01
The dynamic characteristics of the shaft system for a dredging pump were studied with the Finite Element Method (FEM) by SAMCEF ROTOR. At first, the influence of the fluid-solid coupling interaction of mud water and impeller, water sealing and pump shaft on the lateral critical speeds were analyzed. The results indicated that the mud water must be taken into consideration, while the water sealing need not to. Then the effects of radial and thrust rolling bearings on the lateral critical speeds were discussed, which shows that the radial bearing close to the impeller has greatest impact on the 1st order critical speed. At last, the upper and lower limits of the critical speeds of lateral, axial and torsional vibration were calculated. The rated speed of the dredging pump was far less than the predicted critical speed, which can ensure the safe operation of the unit. Each vibration mode is also shown in this paper. This dynamic analysis method offers some reference value on the research of vibration and stability of the shaft system in dredging pump.
The use of statistical characteristics of reducer vibrations as diagnostic symptoms
NASA Technical Reports Server (NTRS)
Balitskiy, F. Y.; Genkin, M. D.; Ivanova, M. A.; Sokolova, A. G.
1973-01-01
The results of a statistical analysis of the vibrations of the experimental RS-1 reducer stand, with a spiral-gear transmission, operating on a closed circuit, are presented. The analysis was carried out on the Minsk-2 and Minsk-32 digital computers, with two-channel analog-digital converter, built in the Institute of the Science of Mechanics. Two-dimensional distribution patterns, conditional dispersions and dispersion ratios were calculated. The octave-band-filtered first harmonics of the tooth frequency f sub z of the vibrations at two different measurement points were considered as the components of the vibration process to be analyzed. The regression lines, corresponding to different values of the loading torque, are presented. Since it was not the gear drive parameters which were determined by diagnostic methods, but the characteristics most sensitive to change in state of the object of the investigation, the loading torque, which is the simplest and most accessible for measurement, was chosen as the condition parameter.
NASA Technical Reports Server (NTRS)
White, W. F., Jr.; Malatino, R. E.
1975-01-01
A method is presented for determining the free vibration characteristics of a rotating blade having nonuniform spanwise properties and cantilever boundary conditions. The equations which govern the coupled flapwise, chordwise, and torsional motion of such a blade are solved using an integrating matrix method. By expressing the equations of motion and matrix notation, utilizing the integrating matrix as an operator, and applying the boundary conditions, the equations are formulated into an eigenvalue problem whose solutions may be determined by conventional methods. Computer results are compared with experimental data.
Measurements of an ARS DE204S Cryocooler's Thermal and Vibration Characteristics
Haid, B
2004-08-24
This document describes measurements that characterize an Advanced Research Systems DE204S cryocooler system. The data is relevant to the thermal performance and vibration characteristics of the cold-head. The thermal measurements include heat load mapping of the 1st and 2nd stage, and temperature fluctuation measurement of the 2nd stage heat station. A comparison of fluctuation measurements by four different sensors is also included to support the 2nd stage fluctuation results. Finally, optical measurement of the cyclic 2nd stage heat station deflection is described.
NASA Astrophysics Data System (ADS)
Mori, Kotaro; Horibe, Tadashi; Ishikawa, Shigekazu; Shindo, Yasuhide; Narita, Fumio
2015-12-01
This work deals with the dynamic bending and energy harvesting characteristics of giant magnetostrictive cantilevers with resonant tuning both numerically and experimentally. The giant magnetostrictive cantilever is fabricated using a thin Terfenol-D layer, SUS layer, movable proof mass, etc, and, is designed to automatically adjust its own resonant frequency to match the external vibration frequency in real time. Three-dimensional finite element analysis was conducted, and the resonant frequency, induced voltage and stress in the magnetostrictive cantilevers were predicted. The resonant frequency and induced voltage were also measured, and comparison was made between simulation and experiment. The time-varying behavior and self-tuning ability are discussed in detail.
Vibration characteristics of a large wind turbine tower on non-rigid foundations
NASA Technical Reports Server (NTRS)
Yee, S. T.; Cang, T. Y. P.; Scavuzzo, R. J.; Timmerman, D. H.; Fenton, J. W.
1977-01-01
Vibration characteristics of the Mod-OA wind turbine supported by nonrigid foundations were investigated for a range of soil rigidities. The study shows that the influence of foundation rotation on the fundamental frequency of the wind turbine is quite significant for cohesive soils or loose sand. The reduction in natural frequency can be greater than 20 percent. However, for a foundation resting on well graded, dense granular materials or bedrock, such effect is small and the foundation can be treated as a fixed base.
Neurocognitive responses to a single session of static squats with whole body vibration.
Amonette, William E; Boyle, Mandy; Psarakis, Maria B; Barker, Jennifer; Dupler, Terry L; Ott, Summer D
2015-01-01
The purpose of this study was to determine if the head accelerations using a common whole body vibration (WBV) exercise protocol acutely reduced neurocognition in healthy subjects. Second, we investigated differential responses to WBV plates with 2 different delivery mechanisms: vertical and rotational vibrations. Twelve healthy subjects (N = 12) volunteered and completed a baseline (BASE) neurocognitive assessment: the Immediate Postconcussion Assessment and Cognitive Test (ImPACT). Subjects then participated in 3 randomized exercise sessions separated by no more than 2 weeks. The exercise sessions consisted of five 2-minute sets of static hip-width stance squats, with the knees positioned at a 45° angle of flexion. The squats were performed with no vibration (control [CON]), with a vertically vibrating plate (vertical vibration [VV]), and with a rotational vibrating plate (rotational vibration [RV]) set to 30 Hz with 4 mm of peak-to-peak displacement. The ImPACT assessments were completed immediately after each exercise session and the composite score for 5 cognitive domains was analyzed: verbal memory, visual memory, visual motor speed, reaction time, and impulse control. Verbal memory scores were unaffected by exercise with or without vibration (p = 0.40). Likewise, visual memory was not different (p = 0.14) after CON, VV, or RV. Significant differences were detected for visual motor speed (p = 0.006); VV was elevated compared with BASE (p = 0.01). There were no significant differences (p = 0.26) in reaction time or impulse control (p = 0.16) after exercise with or without vibration. In healthy individuals, 10 minutes of 30 Hz, 4-mm peak-to-peak displacement vibration exposure with a 45° angle of knee flexion did not negatively affect neurocognition. PMID:25536489
Mahbub, Md H; Yokoyama, Kenjiro; Laskar, Md S; Inoue, Masaiwa; Takahashi, Yukio; Yamamoto, Shinji; Harada, Noriaki
2007-05-01
This study was designed to assess the influence of an antivibration glove on digital vascular responses in healthy subjects exposed to short-term grasping of a vibrating handle. To measure finger blood flow (FBF) and finger skin temperature (FST) once at the end of every min, a blood flowmeter sensor was attached to the dorsum and a thermistor sensor was attached to the medial surface of the subject's middle phalanx of the third finger of the right hand. After 5 min of baseline measurements without or with an antivibration glove meeting ISO standard 10819, worn on the right hand, subjects gripped a vibrating handle with the same hand for a period of 5 min. Vibration was generated at two frequencies of 31.5 Hz and 250 Hz with a frequency weighted rms acceleration of 5.5 m/s(2). FBF and FST continued to be recorded for a further 5 min after release of the vibrating handle. Statistical analysis showed no significant change after vibration exposure in either FST or FBF at 250 Hz, compared to baseline (control) measurements while using the antivibration glove. At 31.5 Hz, FBF data exhibited a significant difference between before and after grasping of vibrating handle, which was less under the condition of wearing the antivibration glove than under the condition of bare hand. The results provide evidence that the antivibration glove considerably influenced finger vascular changes in healthy subjects induced by vibration exposure, especially against high frequency vibration. Further studies are required to assess finger vascular responses to hand-transmitted vibration with antivibration gloves of different manufacturers. PMID:17575396
Evaluation of human response to structural vibration induced by sonic boom
NASA Technical Reports Server (NTRS)
Sutherland, L. C.; Czech, J.
1992-01-01
This paper addresses the topic of building vibration response to sonic boom and the evaluation of the associated human response to this vibration. The paper reexamines some of the issues addressed in the previous extensive coverage of the topic, primarily by NASA, and attempts to offer a fresh viewpoint for some of the problems that may assist in reassessing the potential impact of sonic boom over populated areas. The topics addressed are: (1) human response to vibration; (2) criteria for, and acoustic signature of rattle; (3) structural response to shaped booms, including definition of two new descriptors for assessing the structural response to sonic boom; and (4) a detailed review of the previous NASA/FAA Sonic Boom Test Program involving structural response measurements at Edwards AFB and an initial estimate of structural response to sonic booms from possible high speed civil transport configurations. Finally, these estimated vibration responses are shown to be substantially greater than the human response and rattle criteria developed earlier.
Response of a flexible filament in a flowing soap film subject to a forced vibration
NASA Astrophysics Data System (ADS)
Jia, Laibing; Xiao, Qing; Wu, Haijun; Wu, Yanfeng; Yin, Xiezhen
2015-01-01
The interactions between flexible plates and fluids are important physical phenomena. A flag in wind is one of the most simplified and classical models for studying the problem. In this paper, we investigated the response of a flag in flow with an externally forced vibration by using flexible filaments and soap film. Experiments show that for a filament that is either in oscillation or stationary, the external forced vibration leads to its oscillation. A synchronization phenomenon occurs in the experiments. A small perturbation leads to a large response of flapping amplitude in response. The insight provided here is helpful to the applications in the flow control, energy harvesting, and bionic propulsion areas.
Vibration characteristics of NiTi-Al MMC beam fabricated with ultrasonic welding
NASA Astrophysics Data System (ADS)
Chen, Jian; Wang, Yiqing; Kuang, Xinbin; Zhang, Teng; Liu, Hongzhong; Lu, Bingheng; Xu, Minglong
2015-12-01
A free-vibration differential equation of the compound beam of NiTi-Al MMC (metal matrix composite) is built considering the recovery stress of NiTi foil and based on Timoshenko beam theory to predict the frequency tuning characteristics of the compound beam. The clamped-free (CF) beam is under compressive stress state due to the recovery stress in the NiTi foil, which may cause a reduction in its natural frequency. For an 80 mm CF beam with 8% NiTi (prestrain 3%) embedded in Al matrix, the natural frequency decreases by 52.1% when temperature is up to 70 °C. However the stress state of clamped-clamped (CC) beam depends on the combined effect of recovery stress and thermal expansion of NiTi. At least 20% NiTi should be embedded in Al matrix to increase the natural frequency of CC beam. Finally, the NiTi-Al MMC beam is prepared by ultrasonic welding process. A thermal modal experiment is conducted to study the vibration characteristics of the compound beam. The results show that the natural frequency of the compound beam could be tuned effectively by volume fraction of the NiTi embedded in Al foil, which is consistent with theoretical calculations.
Vibration characteristics of thin rotating cylindrical shells with various boundary conditions
NASA Astrophysics Data System (ADS)
Sun, Shupeng; Chu, Shiming; Cao, Dengqing
2012-08-01
An analysis is presented for the vibration characteristics of thin rotating cylindrical shells with various boundary conditions by use of Fourier series expansion method. Based on Sanders' shell equations, the governing equations of motion which take into account the effects of centrifugal and Coriolis forces as well as the initial hoop tension due to rotating are derived. The displacement field is expressed as a product of Fourier series expressions which represents the axial modal displacements and trigonometric functions which represents the circumferential modal displacements. Stokes' transformation is employed to derive the derivatives of the Fourier series expressions. Then, through the process of formula derivation, an explicit expression of the exact frequency equation can be obtained for a thin rotating cylinder with classical boundary conditions of any type. Once the frequency equation has been determined, the frequencies are calculated numerically. To validate the present analysis, comparisons between the results of the present method and previous studies are performed and very good agreement is achieved. Finally, the method is applied to investigate the vibration characteristics of thin rotating cylindrical shells under various boundaries, and the results are presented.
Ma, Lin; Xu, Zhiwu; Zheng, Kun; Yan, Jiuchun; Yang, Shiqin
2014-03-01
The vibration characteristics of an aluminum surface subjected to ultrasonic waves were investigated with a combination of numerical simulation and experimental testing. The wetting behavior of solder droplets on the vibrating aluminum surface was also examined. The results show that the vibration pattern of the aluminum surface is inhomogeneous. The amplitude of the aluminum surface exceeds the excitation amplitude in some zones, while the amplitude decreases nearly to zero in other zones. The distribution of the zero-amplitude zones is much less dependent on the strength of the vibration than on the location of the vibration source. The surface of the liquid solder vibrates at an ultrasonic frequency that is higher than the vibration source, and the amplitude of the liquid solder is almost twice that of the aluminum surface. The vibration of the surface of the base metal (liquid solder) correlates with the oxide film removal effect. Significant removal of the oxide film can be achieved within 2s when the amplitude of the aluminum surface is higher than 5.4 μm or when the amplitude of the liquid solder surface is higher than 10.2 μm. PMID:24295911
ERIC Educational Resources Information Center
Janssen, Erick; And Others
1994-01-01
Compared reflexogenic and psychogenic penile responses in men with and without erectile disorder. Hypothesized that men with psychogenic dysfunction respond minimally to vibrotactile stimulation. As predicted, responses were different in the vibration condition. Interpretations are provided in terms of attention and appraisal. (BF)
Subjective response to combined noise and vibration during flight of a large twin-jet airplane
NASA Technical Reports Server (NTRS)
Clevenson, S. A.
1976-01-01
A NASA twin-jet airplane was used to obtain controlled noise and vibration environments during flight while obtaining subjective responses from 13 passenger-subjects (6 females and 7 males). Subjective ratings of overall comfort, comfort when considering only vibration, and comfort when considering only noise were obtained during times of different vibration and noise environments. Passenger-subjects were able to distinguish and rate noise better than vibration. In addition, there was a statistically significant difference in ratings of ride comfort due to both sex type and flight experience. Males rated flying discomfort much more severely than females when rating the overall ride and the ride when considering only the noise environment. Experienced passengers also rated the overall ride to be more uncomfortable than inexperienced passengers.
Mechanical and vibrational responses of gate-tunable graphene resonator
NASA Astrophysics Data System (ADS)
Lei, Yuqing; Sun, Jiangping; Gong, Xionghui
2015-03-01
The vibrational mechanical properties of gate-tunable graphene resonator were investigated in detail using finite element analysis (FEA) and simulation. Treating the graphene resonator as a two-dimensional (2D) thin plate, the relationship between resonance frequency and driving force was explored. The effects of built-in tension, adsorbates and graphene size on the performance of resonator including resonance frequency and tunability were also studied. It was shown that resonance frequency could be tuned by the electrostatically induced average tension due to driving force, and exponentially increased with increasing driving force. When the single-layer graphene resonator without any adsorbates had no or very small built-in tension, the tunability of resonator was greater. However, for a high-frequency-range resonator, the resonator with high built-in tension should be used. The simulation results suggested potential applications of graphene resonators tuned by a driving force, such as widely tunable or ultrahigh frequency nanoelectromechanical systems (NEMS) devices.
Thermal cycling and vibration response for PREPP concrete waste forms
Nielson, R.M.; Welch, J.M.
1983-06-01
The Process Experimental Pilot Plant (PREPP) will process those transuranic wastes which do not satisfy the Waste Isolation Pilot Plant (WIPP) Waste Acceptance Criteria. Since these wastes will contain considerable quantities of combustible materials, incineration will be an integral part of the treatment process. Four basic types of PREPP ash wastes have been identified. The four types are designated high metal box waste, combustible waste, average waste, and inorganic sludge. In this process, the output of the incinerator is a mixture of ash and shredded noncombustible material (principally metals) which is separated into two sizes, -1/4 inch (under-size waste) and reverse arrow 1/4 inch (oversize waste). These wastes are solidified with hydraulic cement in 55-gallon drums. Simulated PREPP waste forms prepared by Colorado School of Mines Research Institute were subjected to thermal cycling and vibration testing to demonstrate compliance with the WIPP immobilization criterion. Although actual storage and transport conditions are expected to vary somewhat from those utilized in the testing protocol, the generation of only very small amounts of particulate suggests that the immobilization criterion should be routinely met for similar waste form formulations and production procedures. However, the behavior of waste forms containing significant quantities of off-gas scrubber sludge or considerably higher waste loadings may differ. Limited thermal cycling and vibration testing of prototype waste forms should be conducted if the final formulations or production methods used for actual waste forms differ appreciably from those tested in this study. If such testing is conducted, consideration should be given to designing the experiment to accommodate a larger number of thermal cycles more representative of the duration of storage expected.
Woodcock, J; Sica, G; Peris, E; Sharp, C; Moorhouse, A T; Waddington, D C
2016-03-01
The present research quantifies the influence of source type and the presence of audible vibration-induced rattle on annoyance caused by vibration in residential environments. The sources of vibration considered are railway and the construction of a light rail system. Data were measured in the United Kingdom using a socio-vibration survey (N = 1281). These data are analyzed using ordinal logit models to produce exposure-response relationships describing community annoyance as a function of vibration exposure. The influence of source type and the presence of audible vibration-induced rattle on annoyance are investigated using dummy variable analysis, and quantified using odds-ratios and community tolerance levels. It is concluded that the sample population is more likely to express higher levels of annoyance if the vibration source is construction compared to railway, and if vibration-induced rattle is audible. PMID:27036258
NASA Technical Reports Server (NTRS)
Van Dyke, Michael B.
2014-01-01
During random vibration testing of electronic boxes there is often a desire to know the dynamic response of certain internal printed wiring boards (PWBs) for the purpose of monitoring the response of sensitive hardware or for post-test forensic analysis in support of anomaly investigation. Due to restrictions on internally mounted accelerometers for most flight hardware there is usually no means to empirically observe the internal dynamics of the unit, so one must resort to crude and highly uncertain approximations. One common practice is to apply Miles Equation, which does not account for the coupled response of the board in the chassis, resulting in significant over- or under-prediction. This paper explores the application of simple multiple-degree-of-freedom lumped parameter modeling to predict the coupled random vibration response of the PWBs in their fundamental modes of vibration. A simple tool using this approach could be used during or following a random vibration test to interpret vibration test data from a single external chassis measurement to deduce internal board dynamics by means of a rapid correlation analysis. Such a tool might also be useful in early design stages as a supplemental analysis to a more detailed finite element analysis to quickly prototype and analyze the dynamics of various design iterations. After developing the theoretical basis, a lumped parameter modeling approach is applied to an electronic unit for which both external and internal test vibration response measurements are available for direct comparison. Reasonable correlation of the results demonstrates the potential viability of such an approach. Further development of the preliminary approach presented in this paper will involve correlation with detailed finite element models and additional relevant test data.
Acute bone response to whole body vibration in healthy pre-pubertal boys.
Harrison, R; Ward, K; Lee, E; Razaghi, H; Horne, C; Bishop, N J
2015-06-01
The skeleton responds to mechanical stimulation. We wished to ascertain the magnitude and speed of the growing skeleton's response to a standardised form of mechanical stimulation, vibration. 36 prepubertal boys stood for 10 minutes in total on one of two vibrating platforms (high (>2 g) or low (<1 g) magnitude vibration) on either 1, 3 or 5 successive days (n=12 for each duration); 15 control subjects stood on an inactive platform. Blood samples were taken at intervals before and after vibration to measure bone formation (P1NP, osteocalcin) and resorption (CTx) markers as well as osteoprotegerin and sclerostin. There were no significant differences between platform and control groups in bone turnover markers immediately after vibration on days 1, 3 and 5. Combining platform groups, at day 8 P1NP increased by 25.1% (CI 12.3 to 38.0; paired t-test p=0.005) and bone resorption increased by 10.9% (CI 3.6 to 18.2; paired t-test p=0.009) compared to baseline. Osteocalcin, osteoprotogerin and sclerostin did not change significantly. The growing skeleton can respond quickly to vibration of either high or low magnitude. Further work is needed to determine the utility of such "stimulation-testing" in clinical practice. PMID:26032203
Zeeman, Martha E; Kartha, Sonia; Winkelstein, Beth A
2016-08-01
Whole-body vibration (WBV) is linked epidemiologically to neck and back pain in humans, and to forepaw mechanical allodynia and cervical neuroinflammation in a rodent model of WBV, but the response of the low back and lumbar spine to WBV is unknown. A rat model of WBV was used to determine the effect of different WBV exposures on hind paw behavioral sensitivity and neuroinflammation in the lumbar spinal cord. Rats were exposed to 30 min of WBV at either 8 or 15 Hz on days 0 and 7, with the lumbar spinal cord assayed using immunohistochemistry at day 14. Behavioral sensitivity was measured using mechanical stimulation of the hind paws to determine the onset, persistence, and/or recovery of allodynia. Both WBV exposures induce mechanical allodynia 1 day following WBV, but only the 8 Hz WBV induces a sustained decrease in the withdrawal threshold through day 14. Similarly, increased activation of microglia, macrophages, and astrocytes in the superficial dorsal horn of the lumbar spinal cord is only evident after the painful 8 Hz WBV. Moreover, extracellular signal-regulated kinase (ERK)-phosphorylation is most robust in neurons and astrocytes of the dorsal horn, with the most ERK phosphorylation occurring in the 8 Hz group. These findings indicate that a WBV exposure that induces persistent pain also induces a host of neuroimmune cellular activation responses that are also sustained. This work indicates there is an injury-dependent response that is based on the vibration parameters, providing a potentially useful platform for studying mechanisms of painful spinal injuries. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1439-1446, 2016. PMID:27571442
Flow-induced vibration characteristics of the BWR/5-201 jet pump
LaCroix, L.V.
1982-09-01
A General Electric boiling water reactor BWR/5-201 jet pump was tested for flow-induced vibration (FIV) characteristics in the Large Steam Water Test Facility at Moss Landing, CA, during the period June-July 1978. High level periodic FIV were observed at reactor operating conditions (1027 psia, 532/sup 0/F and prototypical flow rates) for the specific single jet pump assembly tested. High level FIV of similar amplitude and character have been shown capable of damaging jet pump components and associated support hardware if allowed to continue unchecked. High level FIV were effectively suppressed in two special cases tested: (1) lateral load (>500 lb) at the mixer to diffuser slip joint; and (2) a labyrinth seal (5 small, circumferential grooves) on the mixer at the slip joint. Stability criteria for the particular jet pump tested were developed from test data. A cause-effect relationship between the dynamic pressure within the slip joint and the jet pump vibration was established.
A spider's biological vibration filter: micromechanical characteristics of a biomaterial surface.
Young, Seth L; Chyasnavichyus, Marius; Erko, Maxim; Barth, Friedrich G; Fratzl, Peter; Zlotnikov, Igor; Politi, Yael; Tsukruk, Vladimir V
2014-11-01
A strain-sensing lyriform organ (HS-10) found on all of the legs of a Central American wandering spider (Cupiennius salei) detects courtship, prey and predator vibrations transmitted by the plant on which it sits. It has been suggested that the viscoelastic properties of a cuticular pad directly adjacent to the sensory organ contribute to the organ's pronounced high-pass characteristics. Here, we investigate the micromechanical properties of the cuticular pad biomaterial in search of a deeper understanding of its impact on the function of the vibration sensor. These properties are considered to be an effective adaptation for the selective detection of signals for frequencies >40 Hz. Using surface force spectroscopy mapping we determine the elastic modulus of the pad surface over a temperature range of 15-40 °C at various loading frequencies. In the glassy state, the elastic modulus was ~100 MPa, while in the rubbery state the elastic modulus decreased to 20 MPa. These data are analyzed according to the principle of time-temperature superposition to construct a master curve that relates mechanical properties, temperature and stimulus frequencies. By estimating the loss and storage moduli vs. temperature and frequency it was possible to make a direct comparison with electrophysiology experiments, and it was found that the dissipation of energy occurs within a frequency window whose position is controlled by environmental temperatures. PMID:25065547
NASA Astrophysics Data System (ADS)
Jo, Jun Hyeon; Rhim, Yoon Chul
2011-09-01
The axial vibration characteristics of the flexible optical disk are investigated experimentally considering the pick-up window and the geometry of a moving pick-up. The axial runout of the disk is measured by using a laser displacement sensor along the four perpendicular radial directions. Measurements are conducted with respect to the shapes of pick-up faces, which have different radius of curvatures, as well as to the positions of the moving pick-up. A flat stabilizer with damping orifices is used in the experiment and the disk is rotated at 8,000, 10,000, and 12,000 rpm. The axial runouts and the displacements of the disk are measured for 6 different shaped pick-ups. The smallest axial runout of 10 µm, which is well manageable for the current optical disk drive technology, is obtained when we use the curved pick-up with curvatures of 400 mm in the direction of disk rotation.
Effects of blood in veins of dragonfly wing on the vibration characteristics.
Hou, Dan; Yin, Yajun; Zhao, Hongxiao; Zhong, Zheng
2015-03-01
How the blood in veins of dragonfly wing affects its vibration characteristics is investigated. Based on the experimental results of the wing's morphology and microstructures, including the veins, the membranes and the pterostigma, accurate three-dimensional finite element models of the dragonfly forewing are developed. Considering the blood in veins, the total mass, mass distribution and the moments of inertia of the wing are studied. The natural frequencies/modal shapes are analyzed when the veins are filled with and without blood, respectively. The based natural frequency of the model with blood (189 Hz) is much closer to the experimental result. Relative to bending modal shapes, the torsional ones are affected more significantly by the blood. The results in this article reveal the multi-functions of the blood in dragonfly wings and have important implications for the bionic design of flapping-wing micro air vehicles. PMID:25577611
Free-vibration characteristics and correlation of a space station split-blanket solar array
NASA Technical Reports Server (NTRS)
Carney, Kelly S.; Shaker, Francis J.
1989-01-01
Two methods for studying the free-vibration characteristics of a large split-blanket solar array in a zero-g cantilevered configuration are presented. The zero-g configuration corrresponds to an on-orbit configuration of the Space Station solar array. The first method applies the equations of continuum mechanics to determine the natural frequencies of the array; the second uses the finite element method program, MSC/NASTRAN. The stiffness matrix from the NASTRAN solution was found to be erroneously grounded. The results from the two methods are compared. It is concluded that the grounding does not seriously compromise the solution to the elastic modes of the solar array. However, the correct rigid body modes need to be included to obtain the correct dynamic model.
Free-vibration characteristics and correlation of a Space Station split-blanket solar array
NASA Technical Reports Server (NTRS)
Carney, Kelly S.; Shaker, Francis J.
1989-01-01
Two methods for studying the free-vibration characteristics of a large split-blanket solar array in a zero-g cantilevered configuration are presented. The zero-g configuration corresponds to an on-orbit configuration of the Space Station solar array. The first method applies the equations of continuum mechanics to determine the natural frequencies of the array; the second uses the finite element method program, MSC/NASTRAN. The stiffness matrix from the NASTRAN solution was found to be erroneously grounded. The results from the two methods are compared. It is concluded that the grounding does not seriously compromise the solution to the elastic modes of the solar array. However, the correct rigid body modes need to be icluded to obtain the correct dynamic model.
Scanning LDV for vibration measurement of filiform hairs in crickets in response to induced airflow
NASA Astrophysics Data System (ADS)
Santulli, C.; Finn, T. J.; Seidel, R.; Jeronimidis, G.
2006-06-01
Cercal hairs represent in cricket a wind sensitive escape system, able to detect the airflow generated from predating species. These sensors have been studied as a biomimetic concept to allow the development of MEMS for biomedical use. In particular, the behaviour of the hairs, including airflow response, resonant frequency and damping, has been investigated up to a frequency of 20 kHz. The microscopic nature of the hairs, the complex vibrations of excited hairs and the high damping of the system suggested that the use of Laser Doppler vibrometry could possibly improve the test performance. Two types of tests were performed: in the first case the hairs were indirectly excited using the signal obtained from a vibrating aluminium plate, whilst in the second case the hairs were directly excited using a white noise chirp. The results from the first experiment indicated that the hairs move in-phase with the exciting signal up to frequencies in the order of 10 kHz, responding to the vibration modes of the plate with a signal attenuation of 12 to 20 dB. The chirp experiment revealed the presence of rotational resonant modes at 6850 and 11300 Hz. No clear effect of hair length was perceivable on the vibration response of the filiform sensors. The obtained results proved promising to support the mechanical and vibration characterisation of the hairs and suggest that scanning Laser vibrometry can be used extensively on highly dampened biological materials.
On the dimension of complex responses in nonlinear structural vibrations
NASA Astrophysics Data System (ADS)
Wiebe, R.; Spottswood, S. M.
2016-07-01
The ability to accurately model engineering systems under extreme dynamic loads would prove a major breakthrough in many aspects of aerospace, mechanical, and civil engineering. Extreme loads frequently induce both nonlinearities and coupling which increase the complexity of the response and the computational cost of finite element models. Dimension reduction has recently gained traction and promises the ability to distill dynamic responses down to a minimal dimension without sacrificing accuracy. In this context, the dimensionality of a response is related to the number of modes needed in a reduced order model to accurately simulate the response. Thus, an important step is characterizing the dimensionality of complex nonlinear responses of structures. In this work, the dimensionality of the nonlinear response of a post-buckled beam is investigated. Significant detail is dedicated to carefully introducing the experiment, the verification of a finite element model, and the dimensionality estimation algorithm as it is hoped that this system may help serve as a benchmark test case. It is shown that with minor modifications, the method of false nearest neighbors can quantitatively distinguish between the response dimension of various snap-through, non-snap-through, random, and deterministic loads. The state-space dimension of the nonlinear system in question increased from 2-to-10 as the system response moved from simple, low-level harmonic to chaotic snap-through. Beyond the problem studied herein, the techniques developed will serve as a prescriptive guide in developing fast and accurate dimensionally reduced models of nonlinear systems, and eventually as a tool for adaptive dimension-reduction in numerical modeling. The results are especially relevant in the aerospace industry for the design of thin structures such as beams, panels, and shells, which are all capable of spatio-temporally complex dynamic responses that are difficult and computationally expensive to
NASA Technical Reports Server (NTRS)
Van Dyke, Michael B.
2013-01-01
Present preliminary work using lumped parameter models to approximate dynamic response of electronic units to random vibration; Derive a general N-DOF model for application to electronic units; Illustrate parametric influence of model parameters; Implication of coupled dynamics for unit/board design; Demonstrate use of model to infer printed wiring board (PWB) dynamics from external chassis test measurement.
NASA Astrophysics Data System (ADS)
Sakai, Hirotaka; Urakawa, Fumihiro; Aikawa, Akira; Namura, Akira
The vibration of concrete sleepers is an important factor engendering track deterioration. In this paper, we created a three-dimensional finite element model to reproduce a prestressed concrete (PC) sleeper in detail, expressing influence of ballast layers with a 3D spring series and dampers to reproduce their vibration and dynamic characteristics. Determination of these parameters bases on the experimental modal analysis using an impact excitation technique for PC sleepers by adjusting the accelerance between the analytical results and experimental results. Furthermore, we compared the difference of these characteristics between normal sleepers and those with some structural modifications. Analytical results clarified that such means as sleeper width extension and increased sleeper thickness will influence the reduction of ballasted track vibration as improvements of PC sleepers.
NASA Technical Reports Server (NTRS)
Sutton, M. A.; Davis, P. K.
1976-01-01
Numerical solutions of the governing equations of motion of a liquid squeeze film damped forced vibration system were carried out to examine the feasibility of using a liquid squeeze film to cushion and protect large structures, such as buildings, located in areas of high seismic activity. The mathematical model used was that for a single degree of freedom squeeze film damped spring mass system. The input disturbance was simulated by curve fitting actual seismic data with an eleventh order Lagranging polynomial technique. Only the normal component of the seismic input was considered. The nonlinear, nonhomogeneous governing differential equation of motion was solved numerically to determine the transmissibility over a wide range of physical parameters using a fourth-order Runge-Kutta technique. It is determined that a liquid squeeze film used as a damping agent in a spring-mass system can significantly reduce the response amplitude for a seismic input disturbance.
Dias, Thaisa; Polito, Marcos
2015-01-01
This study aimed to compare the acute cardiovascular responses during and after resistance exercise with and without whole-body vibration. Nineteen sedentary adults randomly performed one session of isometric squats without vibration and the same exercise with vibration. Systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were measured. SBP, DBP and HR were also measured for 20 min after the sessions. The exercise with vibration demonstrated significant values (P < 0.05) for SBP (second to sixth sets), DBP (third to sixth sets) and SVR (second to sixth sets) compared with the exercise without vibration. After the sessions, the values of SBP for both exercises were significantly lower than the respective resting values; with no difference between the sessions. In conclusion, exercise with vibration caused increases in SBP, DBP and SVR compared with exercise with no vibration in sedentary adults. PMID:26031551
Analysis of vibrational response in graphite oxide nanoplatelets
NASA Astrophysics Data System (ADS)
Prias Barragan, Jhon Jairo; Gross, Katherine; Lajaunie, Luc; Arenal, Raul; Ariza Calderon, Hernando; Prieto, Pedro
In this work, we present a new low-cost fabrication process to obtain graphite oxide nanoplatelets from bamboo pyroligneous acid (GO-BPA) by thermal decomposition method using a pyrolysis system for different carbonization temperatures from 673 to 973 K. The GO-BPA samples were characterized by using Raman, FTIR, XRD, SEM and TEM techniques, whose results suggest that increased carbonization temperature increases graphite conversion, boundary defects, desorption of some organic compounds and phonon response, respectively. We discuss potential applications of the GO-BPA samples involving phonon response that would benefit from a fully scaled technology, advanced electronic sensors and devices.
NASA Technical Reports Server (NTRS)
Walter, T. J.
1978-01-01
Vibration characteristics for overhauled T53 engines, including rejection rate, principal sources of vibration, and normal procedures taken by the overhaul center to reduce engine vibration are summarized. Analytical and experimental data were compared to determine the engine's dynamic response to unbalance forces with results showing that the engine operates through bending critical speeds. Present rigid rotor balancing techniques are incapable of compensating for the flexible rotor unbalance. A comparison of typical test cell and aircraft vibration levels disclosed significant differences in the engine's dynamic response. A probable spline shift phenomenon was uncovered and investigated. Action items to control costs and reduce vibration levels were identified from analytical and experimental studies.
Effects of gear crack propagation paths on vibration responses of the perforated gear system
NASA Astrophysics Data System (ADS)
Ma, Hui; Pang, Xu; Zeng, Jin; Wang, Qibin; Wen, Bangchun
2015-10-01
This paper investigates the dynamic behaviors of a perforated gear system considering effects of the gear crack propagation paths and this study focuses on the effects of a crack propagating through the rim on the time-varying mesh stiffness (TVMS) and vibration responses. Considering the effects of the extended tooth contact, a finite element (FE) model of a gear pair is established based on ANSYS software. TVMS of the perforated gear with crack propagating through tooth and rim are calculated by using the FE model. Furthermore, a lumped mass model is adopted to investigate the vibration responses of the perforated gear system. The results show that there exist three periods related to slots of the gear body in a rotating period of the perforated gear. Gear cracks propagating through tooth and rim both reduce the gear body stiffness and lead to reduction of TVMS besides the crack tooth contact moment, and the TVMS weakening for the former is less than that for the latter. Moreover, the results also show that the gear crack propagating through the rim (CPR) has a greater effect on vibration responses than the gear crack propagating through the tooth (CPT) under the same crack level. Vibration level increases with the increasing crack depth, especially for the gear with CPR.
Experimental studies for determining human discomfort response to vertical sinusoidal vibration
NASA Technical Reports Server (NTRS)
Dempsey, T. K.; Leatherwood, J. D.
1975-01-01
A study was conducted to investigate several problems related to methodology and design of experiments to obtain human comfort response to vertical sinusoidal vibration. Specifically, the studies were directed to the determination of (1) the adequacy of frequency averaging of vibration data to obtain discomfort predictors, (2) the effect of practice on subject ratings, (3) the effect of the demographic factors of age, sex, and weight, and (4) the relative importance of seat and floor vibrations in the determination of measurement and criteria specification location. Results indicate that accurate prediction of discomfort requires knowledge of both the acceleration level and frequency content of the vibration stimuli. More importantly, the prediction of discomfort was shown to be equally good based upon either floor accelerations or seat accelerations. Furthermore, it was demonstrated that the discomfort levels in different seats resulting from similar vibratory imputs were equal. Therefore, it was recommended that criteria specifications and acceleration measurements be made at the floor location. The results also indicated that practice did not systematically influence discomfort responses nor did the demographic factors of age, weight, and sex contribute to the discomfort response variation.
Response characteristics of selected personnel neutron dosimeters
McDonald, J.C.; Fix, J.J.; Hadley, R.T.; Holbrook, K.L.; Yoder, R.C.; Roberson, P.L.; Endres, G.W.R.; Nichols, L.L.; Schwartz, R.B.
1983-09-01
Performance characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined from their evaluation of neutron dose equivalent received after irradiations with specific neutron sources at either the National Bureau of Standards (NBS) or the Pacific Northwest Laboratory (PNL). The characteristics assessed included: lower detection level, energy response, precision and accuracy. It was found that when all of the laboratories employed a common set of calibrations, the overall accuracy was approximately +-20%, which is within uncertainty expected for these dosimeters. For doses above 80 mrem, the accuracy improved to better than 10% when a common calibration was used. Individual differences found in this study may reflect differences in calibration technique rather than differences in the dose rates of actual calibration standards. Second, at dose rates above 100 mrem, the precision for the best participants was generally below +-10% which is also within expected limits for these types of dosimeters. The poorest results had a standard deviation of about +-25%. At the lowest doses, which were sometimes below the lower detection limit, the precision often approached or exceeded +-100%. Third, the lower level of detection for free field /sup 252/Cf neutrons generally ranged between 20 and 50 mrem. Fourth, the energy dependence study provided a characterization of the response of the dosimeters to neutron energies far from the calibration energy. 11 references, 22 figures, 26 tables.
NASA Technical Reports Server (NTRS)
Dolkas, C. B.; Leon, H. A.; Chackerian, M.
1971-01-01
Study carried out to obtain some notion of the initial phasing and interactive effects among some hormones known to be responsive to vibration stress. Sprague-Dawley derived rats were exposed to the acute effects of confinement and confinement with lateral (plus or minus G sub y) vibration. The coincident monitoring of glucose, insulin, growth hormone, and corticosterone plasma levels, during and immediately subsequent to exposure to brief low level vibration, exhibits the effects of inhibition of insulin release by epinephrine. The ability of insulin (IRI) to return rapidly to basal levels, from appreciably depressed levels during vibration, in the face of elevated levels of glucose is also shown. Corticosterone responds with almost equal rapidity, but in opposite phase to the IRI. The immuno-assayable growth hormone (IGH) dropped from a basal level of 32 ng/ml to 7.3 ng/ml immediately subsequent to vibration and remained at essentially that level throughout the experiment (60 min). Whether these levels represent a real fall in the rat or whether they merely follow the immuno-logically deficient form is still in question.
NASA Astrophysics Data System (ADS)
Viswamurthy, S. R.; Ganguli, Ranjan
2007-03-01
This study aims to determine optimal locations of dual trailing-edge flaps to achieve minimum hub vibration levels in a helicopter, while incurring low penalty in terms of required trailing-edge flap control power. An aeroelastic analysis based on finite elements in space and time is used in conjunction with an optimal control algorithm to determine the flap time history for vibration minimization. The reduced hub vibration levels and required flap control power (due to flap motion) are the two objectives considered in this study and the flap locations along the blade are the design variables. It is found that second order polynomial response surfaces based on the central composite design of the theory of design of experiments describe both objectives adequately. Numerical studies for a four-bladed hingeless rotor show that both objectives are more sensitive to outboard flap location compared to the inboard flap location by an order of magnitude. Optimization results show a disjoint Pareto surface between the two objectives. Two interesting design points are obtained. The first design gives 77 percent vibration reduction from baseline conditions (no flap motion) with a 7 percent increase in flap power compared to the initial design. The second design yields 70 percent reduction in hub vibration with a 27 percent reduction in flap power from the initial design.
Free vibration characteristics of multiple load path blades by the transfer matrix method
NASA Technical Reports Server (NTRS)
Murthy, V. R.; Joshi, Arun M.
1986-01-01
The determination of free vibrational characteristics is basic to any dynamic design, and these characteristics can form the basis for aeroelastic stability analyses. Conventional helicopter blades are typically idealized as single-load-path blades, and the transfer matrix method is well suited to analyze such blades. Several current helicopter dynamic programs employ transfer matrices to analyze the rotor blades. In this paper, however, the transfer matrix method is extended to treat multiple-load-path blades, without resorting to an equivalent single-load-path approximation. With such an extension, these current rotor dynamic programs which employ the transfer matrix method can be modified with relative ease to account for the multiple load paths. Unlike the conventional blades, the multiple-load-path blades require the introduction of the axial degree-of-freedom into the solution process to account for the differential axial displacements of the different load paths. The transfer matrix formulation is validated through comparison with the finite-element solutions.
NASA Technical Reports Server (NTRS)
Carden, H. D.
1979-01-01
Mechanical excitation was used, and measurements of acceleration response, natural frequencies, and nodal patterns were performed. Results indicate that the wall sections and the complete wall did not act as a unit in responding to sinusoidal vibration inputs. Calculated frequencies of the components that account for this independent behavior of the studs and face sheets agreed resonably well with experimental frequencies. Experimental vibrations of the plate glass window agreed with the calculated behavior, and responses of the window exposed to airplane flyover noise were readily correlated with the test results.
Torsional optokinetic nystagmus: normal response characteristics
Farooq, S J; Proudlock, F A; Gottlob, I
2004-01-01
Background/aims: Few studies have investigated normal response characteristics of torsional optokinetic nystagmus (tOKN). The authors have investigated the effect of stimulus velocity and central/peripheral stimulation on tOKN. Methods: Torsional OKN was elicited using a sinusoidal grating rotating at velocities of 3°/s to 1000°/s in clockwise and anticlockwise directions. To investigate the effect of central stimulation, stimulus size was varied from 2.86° to 50.8°. An artificial scotoma placed over a 50.8° stimulus was varied from 2.86° to 43.2° to investigate peripheral stimulation. Eight subjects participated in each experiment and torsional eye movements were recorded using video-oculography. The mean slow phase velocity (MSPV) and gain were calculated. Results: The maximum gain occurred in response to 8°/s stimulation. The MSPV increased up to a stimulus velocity of 200°/s achieving a maximum of 3°/s in both directions. MSPV was linearly correlated with the log of stimulus velocity. The smallest field size, rotating at 40°/s, evoked 10% of the gain elicited by the largest display. When the most peripheral stimulus was used, the gain was maintained at 50% of the gain evoked when the full display was used. Conclusions: A wide range of stimulus velocities can elicit tOKN and peripheral field stimulation contributes significantly to its response. PMID:15148215
Acceleration response spectrum for prediction of structural vibration due to individual bouncing
NASA Astrophysics Data System (ADS)
Chen, Jun; Wang, Lei; Racic, Vitomir; Lou, Jiayue
2016-08-01
This study is designed to develop an acceleration response spectrum that can be used in vibration serviceability assessment of civil engineering structures, such as floors and grandstands those are dynamically excited by individual bouncing. The spectrum is derived from numerical simulations and statistical analysis of acceleration responses of a single degree of freedom system with variable natural frequency and damping under a large number of experimentally measured individual bouncing loads. Its mathematical representation is fit for fast yet reliable application in design practice and is comprised of three equations that describe three distinct frequency regions observed in the actual data: the first resonant plateau (2-3.5 Hz), the second resonant plateau (4-7 Hz) and a descension region (7-15 Hz). Finally, this paper verifies the proposed response spectrum approach to predict structural vibration by direct comparison against numerical simulations and experimental results.
Paarmann, A.; Hayashi, T.; Mukamel, S.; Miller, R. J. D.
2009-01-01
A simulation formalism for the nonlinear response of vibrational excitons is presented and applied to the OH stretching vibrations of neat liquid H2O. The method employs numerical integration of the Schrödinger equation and allows explicit treatment of fluctuating transition frequencies, vibrational couplings, dipole moments, and the anharmonicities of all these quantities, as well as nonadiabatic effects. The split operator technique greatly increases computational feasibility and performance. The electrostatic map for the OH stretching vibrations in liquid water employed in our previous study [A. Paarmann et al., J. Chem. Phys. 128, 191103 (2008)] is presented. The two-dimensional spectra are in close agreement with experiment. The fast 100 fs dynamics are primarily attributed to intramolecular mixing between states in the two-dimensional OH stretching potential. Small intermolecular couplings are sufficient to reproduce the experimental energy transfer time scales. Interference effects between Liouville pathways in excitonic systems and their impact on the analysis of the nonlinear response are discussed. PMID:19485440
NASA Astrophysics Data System (ADS)
Wang, Fu-Cheng; Tsao, Yu-Chia; Yen, Jia-Yush
2009-06-01
This paper demonstrates a method to control an electron beam lithography (EBL) system's vibrations with a newly developed technique called disturbance response decoupling (DRD). Resolution requirements make the vibration control of EBL systems increasingly important. Satisfying performance criteria requires considering two kinds of disturbances, load disturbances from the machine and ground disturbances from the environment, in EBL systems. Controlling lithography tools' vibrations has been studied for many years; however, designing controllers by traditional approaches can be very complicated because of these two types of disturbances' conflicting requirements. Therefore, DRD techniques were applied for this paper to deal independently with these performance requirements. The DRD control method was initially proposed in 2001 to address vehicle suspension control problems. This paper proposes a generalized and experimentally realized DRD control structure to suppress an EBL system's vibrations. The work was carried out in three parts. First, passive isolators were used to isolate ground disturbances. Second, active components were applied to improve the system's responses to load disturbances. Finally, the system was integrated to verify its overall performance. Simulations and experiments verify the proposed control strategies' effectiveness.
Analytical and experimental vibration and buckling characteristics of a pretensioned stayed column
NASA Technical Reports Server (NTRS)
Belvin, W. K.
1982-01-01
Modal vibration tests to determine lateral modes of vibration of a stayed column and static axial compression tests to determine the column's buckling and postbuckling behavior have been performed. Effects of stay tension levels and vibration-load interaction are presented. Two finite element models are used to analyze the column, a three-dimensional frame using NASTRAN and an equivalent two-dimensional frame using an exact dynamic stiffness matrix. Both analyses correlated well with the linear vibration and buckling experimental data. Results indicate premature buckling of the column due to vibration-load interaction and nonlinear oscillations due to stay slackening. Postbuckling behavior of the column is unusual because of stay slackening and results in a postbuckling restoring force of less than the bifurcation buckling load. Guidelines for design of pretensioned structures are presented which consider buckling, postbuckling and vibration behavior.
NASA Astrophysics Data System (ADS)
Issa, Jimmy S.; Shaw, Steven W.
2015-07-01
In this work we investigate the nonlinear dynamic response of systems composed of a primary inertia to which multiple identical vibration absorbers are attached. This problem is motivated by observations of systems of centrifugal pendulum vibration absorbers that are designed to reduce engine order torsional vibrations in rotating systems, but the results are relevant to translational systems as well. In these systems the total absorber mass is split into multiple equal masses for purposes of distribution and/or balance, and it is generally expected that the absorbers will act in unison, corresponding to a synchronous response. In order to capture nonlinear effects of the responses of the absorbers, specifically, their amplitude-dependent frequency, we consider them to possess nonlinear stiffness. The equations of motion for the system are derived and it is shown how one can uncouple the equations for the absorbers from that for the primary inertia, resulting in a system of identical resonators that are globally coupled. These symmetric equations are scaled for weak nonlinear effects, near resonant forcing, and small damping. The method of averaging is applied, from which steady-state responses and their stability are investigated. The response of systems with two, three, and four absorbers are considered in detail, demonstrating a rich variety of bifurcations of the synchronous response, resulting in responses with various levels of symmetry in which sub-groups of absorbers are mutually synchronous. It is also shown that undamped models with more than two absorbers possess a degenerate response, which is made robust by the addition of damping to the model. Design guidelines are proposed based on the nature of the system response, with the aim of minimizing the acceleration of the primary system. It is shown that the desired absorber parameters are selected so that the system achieves a stable synchronous response which does not undergo jumps via saddle
NASA Astrophysics Data System (ADS)
Ma, Hui; Pang, Xu; Feng, Ranjiao; Wen, Bangchun
2016-03-01
In this paper, a mesh stiffness model is developed for profile shifted gears with addendum modifications and tooth profile modifications (TPMs). The time-varying mesh stiffness (TVMS), load sharing factor (LSF), loaded static transmission error (LSTE) and non-loaded static transmission error (NLSTE) of a profile shifted spur gear pair with TPMs are obtained by the analytical model. The optimum profile modification curve under different amounts of TPM is determined by analyzing the LSTE first. Then, considering the effect of NLSTE, finite element (FE) model of a geared rotor system is established. The system vibration responses under different TPM curves are analyzed and the optimum modification curve is further evaluated by amplitude frequency responses. The results show that the optimum modification curve is related to the amount of TPM and modification coefficients. The comparison of the optimum profile modification curves is evaluated by LSTE and vibration responses, which shows that the optimum modification curve should be determined by evaluating the vibration response of the geared rotor system in the low mesh frequency range.
Electrorheological vibration system
NASA Astrophysics Data System (ADS)
Korobko, Evguenia V.; Shulman, Zinovy P.; Korobko, Yulia O.
2001-07-01
The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.
Vibration Response Testing of the CEBAF 12GeV Upgrade Cryomodules
Davis, G. Kirk; Matalevich, Joseph R.; Wiseman, Mark A.; Powers, Thomas J.
2012-09-01
The CEBAF 12 GeV upgrade project includes 80 new 7-cell cavities to form 10 cryomodules. These cryomodules were tested during production to characterize their microphonic response in situ. For several early cryomodules, detailed (vibration) modal studies of the cryomodule string were performed during the assembly process to identify the structural contributors to the measured cryomodule microphonic response. Structural modifications were then modelled, implemented, and verified by subsequent modal testing and in-situ microphonic response testing. Interim and latest results from this multi-stage process will be reviewed.
Dynamic characteristics of a cable-stayed bridge measured from traffic-induced vibrations
NASA Astrophysics Data System (ADS)
Wang, Yun-Che; Chen, Chern-Hwa
2012-09-01
This paper studies the dynamic characteristics of the Kao-Ping-Hsi cable-stayed bridge under daily traffic conditions. Experimental data were measured from a structural monitoring system, and system-identification techniques, such as the random decrement (RD) technique and Ibrahim time-domain (ITD) method, were adopted. The first five modes of the bridge were identified for their natural frequencies and damping ratios under different traffic loading conditions, in terms of root-mean-square (RMS) deck velocities. The magnitude of the torsion mode of the Kao-Ping-Hsi cable-stayed bridge is found to be one order-of-magnitude less than the transfer mode, and two orders-of-magnitude less than the vertical modes. Out results indicated that vibrations induced by traffic flow can be used as an indicator to monitor the health of the bridge due to their insensitivity to the natural frequencies of the cable-stayed bridge. Furthermore, the damping ratios may be used as a more sensitive indicator to describe the condition of the bridge.
NASA Technical Reports Server (NTRS)
Knight, Brent; Parsons, David; Smith, Andrew; Hunt, Ron; LaVerde, Bruce; Towner, Robert; Craigmyle, Ben
2013-01-01
Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from a series of acoustically excited tests to determine the effectiveness of these dampers for equipment mounted to a curved orthogrid panel for a launch vehicle application. Vibration attenuation trends are examined for variations in particle damper fill level, component mass, and excitation energy. A significant response reduction at the component level was achieved, suggesting that comparatively small, strategically placed, particle damper devices might be advantageously used in launch vehicle design. These test results were compared to baseline acoustic response tests without particle damping devices, over a range of isolation and damping parameters. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.
NASA Technical Reports Server (NTRS)
Leatherwood, J. D.; Dempsey, T. K.
1976-01-01
An experimental investigation determined that the psychophysical relationships between subjective discomfort evaluations to vibratory stimuli and subjective evaluations of the intensity of vibratory stimuli can be expressed in a linear fashion. Furthermore, significant differences were found to exist between discomfort and intensity subjective response for several but not all discrete frequencies investigated. The implication of these results is that ride quality criteria based upon subjective evaluation of vibration intensity should be applied cautiously in the development of criteria for human comfort.
Vibration and Operational Characteristics of a Composite-Steel (Hybrid) Gear
NASA Technical Reports Server (NTRS)
Handschuh, Robert F.; LaBerge, Kelsen E.; DeLuca, Samuel; Pelagalli, Ryan
2014-01-01
Hybrid gears have been tested consisting of metallic gear teeth and shafting connected by composite web. Both free vibration and dynamic operation tests were completed at the NASA Glenn Spur Gear Fatigue Test Facility, comparing these hybrid gears to their steel counterparts. The free vibration tests indicated that the natural frequency of the hybrid gear was approximately 800 Hz lower than the steel test gear. The dynamic vibration tests were conducted at five different rotational speeds and three levels of torque in a four square test configuration. The hybrid gears were tested both as fabricated (machined, composite layup, then composite cure) and after regrinding the gear teeth to the required aerospace tolerance. The dynamic vibration tests indicated that the level of vibration for either type of gearing was sensitive to the level of load and rotational speed.
Analytical and experimental evaluations of Space Shuttle TPS tile vibration response
NASA Technical Reports Server (NTRS)
Piersol, A. G.; Pope, L. D.
1982-01-01
Analytical studies and laboratory experiments have been performed to evaluate the vibration response of the Space Shuttle Thermal Protection System (TPS) tiles due to the intense rocket generated acoustic noise during lift-off. The TPS tiles are mounted over the exterior of the Space Shuttle Orbiter structure through Strain Isolation Pads (SIP) which protect the tiles from thermal induced shear loads at their interface. The analytical predictions indicate that the response of a typical tile is governed by the structural vibration inputs through the SIP under the tile at frequencies below 250 Hz, and by the direct acoustic excitation over the exterior surface of the tile at frequencies above 250 Hz. An evaluation of the laboratory test data for this same tile, in which conditioned (partial) coherent output spectral analysis procedures were used, leads to exactly the same conclusion. The results demonstrate the power of conditioned spectral analysis procedures in identifying vibration response mechanisms when two or more of the inputs are highly correlated.
NASA Astrophysics Data System (ADS)
Wang, Yan; Li, Lu-ping; Lu, Xu-xiang; Rao, Hong-de; Liu, Yu-jing
2008-11-01
Integral shroud is an advanced technique used to improve reliability of steam turbine blades. In this paper, dynamic characteristics of vibration-impact process of steam turbine blades with integral shroud are studied. To test and verify the reliability of calculation result, a series of experiments are well performed on the platform of contracting and impacting of blades tips. The dynamic strain data under different gaps, different loads and different rotating speeds are surveyed through which the log decrement at each condition is obtained, and the effects of vibration damping are obtained by comparing the log decrement. The results of experimental study show that larger log decrement means larger system damping and better effectives of vibration reduction. Besides, the effects of vibro-impact reduction of different parameters are got and the experimental study results show that the vibro-impact structure is a good vibration damper. The dynamic stress of the blade with integral shroud is insensitive to loads when the gap between adjacent integral shrouds is small. In short, the achievements gained in the paper have revealed dynamic characteristics for vibro-impact process of steam turbine blades with integral shroud, which will bring important engineering application to development and modification design of the integrally shrouded blades.
Universal response spectrum procedure for predicting walking-induced floor vibration
NASA Astrophysics Data System (ADS)
Brownjohn, James; Racic, Vitomir; Chen, Jun
2016-03-01
Floor vibrations caused by people walking are an important serviceability problem both for human occupants and vibration-sensitive equipment. Present design methodologies available for prediction of vibration response due to footfall loading are complex and suffer from division between low and high frequency floors. In order to simplify the design process and to avoid the problem of floor classification, this paper presents a methodology for predicting vibration response metrics due to pedestrian footfalls for any floor type having natural frequency in the range 1-20 Hz. Using a response spectrum approach, a database of 852 weight-normalised vertical ground reaction force (GRF) time histories recorded for more than 60 individuals walking on an instrumented treadmill was used to calculate response metrics. Chosen metrics were peak values of 1 s peak root-mean-square (RMS) acceleration and peak envelope one-third octave velocities. These were evaluated by weight-normalising the GRFs and applying to unit-mass single degree of freedom oscillators having natural frequencies in the range 1-20 Hz and damping ratios in the range 0.5-5%. Moreover, to account for effect of mode shape and duration of crossing (i.e. duration of dynamic loading), the recorded GRFs were applied for three most typical mode shapes and floor spans from 5 m to 40 m. The resulting peak values as functions of frequency i.e. spectra are condensed to statistical representations for chosen probability of being exceeded over a wide range of applications. RMS (acceleration) spectra show strong peaks corresponding to the first harmonic of pacing rate followed by clear minima at approximately 3.5 Hz, a second much smaller peak corresponding to the second harmonic and a steady decline with increasing frequency beginning around 5 Hz. One-third octave spectra show asymptotic trends with frequency, span and damping. A comprehensive validation exercise focusing on the acceleration RMS spectra was based on a
A scaling approach for the prediction of high-frequency mean responses of vibrating systems.
Li, Xianhui
2010-05-01
This analysis presents a scaling approach to predict high-frequency mean responses of vibrating systems. The basis of the approach lies in the dynamic similitude between the original systems and the scaled models. A general scaling law is formulated using Skudrzyk's mean-value theorem and its specific form is derived for the case of a flexural plate. Modal density is scaled down to reduce the computational cost in the high-frequency mean response prediction. Different scaling procedures are numerically experimented and some insights are given about the accuracy of the scaling approach as compared with a dense finite element analysis. PMID:21117716
Modeling “unilateral” response in the cross-ties of a cable network: Deterministic vibration
NASA Astrophysics Data System (ADS)
Giaccu, Gian Felice; Caracoglia, Luca; Barbiellini, Bernardo
2014-09-01
Cross-ties are employed as passive devices for the mitigation of stay-cable vibrations, exhibited on cable-stayed bridges under wind and wind-rain excitation. Large-amplitude oscillation can result in damage to the cables or perceived discomfort to bridge users. The “cable-cross-ties system” derived by connecting two or more stays by transverse cross-ties is often referred to as an “in-plane cable network”. Linear modeling of network dynamics has been available for some time. This framework, however, cannot be used to detect incipient failure in the restrainers due to slackening or snapping. A new model is proposed in this paper to analyze the effects of a complete loss in the pre-tensioning force imparted to the cross-ties, which leads to the “unilateral” free-vibration response of the network (i.e., a cross-tie with linear-elastic internal force in tension and partially inactive in compression). Deterministic free vibrations of a three-cable network are investigated by using the “equivalent linearization method”. A performance coefficient is introduced to monitor the relative reduction in the average (apparent) stiffness of the connector during free vibration response (“mode by mode”), exhibiting unilateral behavior. A reduction of fifty percent in the apparent stiffness was observed in the cross-tie when the pre-tensioning force is small in comparison with the tension force in the stay. This coefficient may be used as a damage indicator for the selection of the initial pre-tensioning force in the cross-ties needed to avoid slackening.
NASA Astrophysics Data System (ADS)
Mandapuram, Santosh; Rakheja, Subhash; Marcotte, Pierre; Boileau, Paul-Émile
2011-08-01
The apparent mass and seat-to-head-transmissibility response functions of the seated human body were investigated under exposures to fore-aft ( x), vertical ( z), and combined fore-aft and vertical ( x and z) axis whole-body vibration. The coupling effects of dual-axis vibration were investigated using two different frequency response function estimators based upon the cross- and auto-spectral densities of the response and excitation signals, denoted as H1 and Hv estimators, respectively. The experiments were performed to measure the biodynamic responses to single and uncorrelated dual-axis vibration, and to study the effects of hands support, back support and vibration magnitude on the body interactions with the seatpan and the backrest, characterized in terms of apparent masses and the vibration transmitted to the head. The data were acquired with 9 subjects exposed to two different magnitudes of vibration applied along the individual x- and z-axis (0.25 and 0.4 m/s 2 rms), and along both the axis (0.28 and 0.4 m/s 2 rms along each axis) in the 0.5-20 Hz frequency range. The two methods resulted in identical single-axis responses but considerably different dual-axis responses. The dual-axis responses derived from the Hv estimator revealed notable effects of dual-axis vibration, as they comprised both the direct and cross-axis responses observed under single axis vibration. Such effect, termed as the coupling effect, was not evident in the dual-axis responses derived using the commonly used H1 estimator. The results also revealed significant effects of hands and back support conditions on the coupling effects and the measured responses. The back support constrained the upper body movements and thus showed relatively weaker coupling compared to that observed in the responses without the back support. The effect of hand support was also pronounced under the fore-aft vibration. The results suggest that a better understanding of the seated human body responses to
On multiple manifestations of the second response branch in streamwise vortex-induced vibrations
NASA Astrophysics Data System (ADS)
Cagney, N.; Balabani, S.
2013-07-01
The structural motion and velocity field in the wake of a cylinder exhibiting vortex-induced vibration (VIV) in the streamwise direction were measured using Particle-Image Velocimetry. The effect of hysteresis on the amplitude response of the cylinder and the existence of multiple wake modes in the region of the second response branch were examined. As the reduced velocity was decreased, there was a reduction in the lock-in range; outside this range the amplitude response was found to be negligible and the A-II mode (which is similar to the von Kármán vortex street) was observed in the wake. When the reduced velocity was increased the second branch could be manifested in two forms, depending on whether the wake exhibited the SA or the A-IV mode (in which two and four vortices are shed per wake cycle, respectively). The A-IV mode has been observed in studies in which a cylinder was forced to oscillate in the streamwise direction; however, this represents the first time that it has been recorded in the wake of a freely oscillating body, and it was not previously known that the A-IV mode was capable of exciting self-sustaining vibrations. Both the SA and A-IV modes were stable and no intermittent mode-switching was observed; however, it was found to be unpredictable which mode would dominate as the reduced velocity was varied and the cylinder entered the second response branch. Analysis of the cylinder displacement signals measured while each mode was dominant indicated that the SA mode excited larger amplitude vibrations than the A-IV mode. A reduced velocity near the second response branch was identified at which the wake could exhibit either the SA, A-IV, or A-II modes, with the latter occurring as the reduced velocity was decreased. Although bi-modal behaviour is well established in VIV studies, as far as the authors are aware, this represents the first time that a point has been observed in the response regime of a freely oscillating structure in which three
Characterization of the tendon vibration reflex response in hemi-spastic stroke individuals.
Suresh, Nina L; Wang, Inga; Heckman, C J; Rymer, W Zev
2011-01-01
The objective of our study was to assess the role of persistent inward currents, or PICs, on the excitability of motoneurons innervating spastic muscle in hemi-spastic stroke individuals. This was accomplished by examining the effects of tonic vibration applied to the tendon of the biceps brachii muscle. The elicited TVR (tonic vibration reflex) provides a useful way to assess the degree of excitability of spinal neurons in spastic syndromes, and it has additional features that may signify the presence of PICs in spastic motoneurons. We applied sinusoidal stretches of varied duration to the biceps tendon of two hemi-spastic stroke individuals and one neurologically intact individual. We recorded the resulting TVR response from electromyographic(EMG) signals obtained from the biceps as well as force recorded at the wrist. The results of our preliminary study show that the initial rise of the TVR force response as well as the force magnitude are generally greater in spastic muscle, perhaps a marker of motoneuron excitability. Additionally, a shorter vibration duration was sufficient to evoke a response on the spastic side of our tested stroke subjects. However, the key marker of PICs--the decay of the force response as well as sustained after-discharge did not exhibit clear differences. Our present data suggests that motoneurons innervating spastic muscle are more readily activated, and thus exhibit increased excitability, which could possibly be a function of greater depolarization, without a change in PIC magnitude. Our data does not rule out the possibility of subthreshold activation of the PIC resulting in enhanced motoneuron depolarization. PMID:22254740
NASA Astrophysics Data System (ADS)
Huang, Ya; Griffin, Michael J.
2008-04-01
Nonlinear biodynamic responses are evident in many studies of the apparent masses of sitting and standing subjects in static postures that require muscle activity for postural control. In the present study, 12 male subjects adopted a relaxed semi-supine posture assumed to involve less muscle activity than during static sitting and standing. The supine subjects were exposed to two types of vertical vibration (in the x-axis of the semi-supine body): (i) continuous random vibration (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75, and 1.0 m s -2 rms); (ii) intermittent random vibration (0.25-20 Hz) alternately at 0.25 and 1.0 m s -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 10.35 to 7.32 Hz as the vibration magnitude increased from 0.125 to 1.0 m s -2 rms. This nonlinear response was apparent in both the vertical ( x-axis) apparent mass and in the horizontal ( z-axis) cross-axis apparent mass. As the vibration magnitude increased from 0.25 to 1.0 m s -2 rms, the median resonance frequency of the apparent mass with intermittent random vibration decreased from 9.28 to 8.06 Hz whereas, over the same range of magnitudes with continuous random vibration, the resonance frequency decreased from 9.62 to 7.81 Hz. The median change in the resonance frequency (between 0.25 and 1.0 m s -2 rms) was 1.37 Hz with the intermittent random vibration and 1.71 with the continuous random vibration. With the intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration of the same magnitudes. The response was typical of thixotropy that may be a primary cause of the nonlinear biodynamic responses to whole-body vibration.
Suzuki, K.; Watanabe, T.; Mitsumori, T.; Shimizu, N.; Kobayashi, H.; Ogawa, N.
1995-08-01
This report deals with the experimental study of seismic response behavior of piping systems in industrial facilities such as petrochemical, oil refinery, and nuclear plants. Special attention is focused on the nonlinear dynamic response of piping systems due to frictional vibration appearing in piping and supporting devices. A three-dimensional mock-up piping and supporting structure model wherein piping is of 30-m length and 200-mm diameter is excited by a large-scale (15 m x 15 m) shaking table belong to the National Research Institute for Earth Science and Disaster Prevention in Tsukuba, Ibaraki. Power spectra of the response vibration and the loading-response relationship in the form of a hysteresis loop under several loading conditions are obtained. The response reduction effect caused by frictional vibration is evaluated and demonstrated in terms of response reduction factor.
Dong, Ren G.; Welcome, Daniel E.; McDowell, Thomas W.; Wu, John Z.
2015-01-01
While simulations of the measured biodynamic responses of the whole human body or body segments to vibration are conventionally interpreted as summaries of biodynamic measurements, and the resulting models are considered quantitative, this study looked at these simulations from a different angle: model calibration. The specific aims of this study are to review and clarify the theoretical basis for model calibration, to help formulate the criteria for calibration validation, and to help appropriately select and apply calibration methods. In addition to established vibration theory, a novel theorem of mechanical vibration is also used to enhance the understanding of the mathematical and physical principles of the calibration. Based on this enhanced understanding, a set of criteria was proposed and used to systematically examine the calibration methods. Besides theoretical analyses, a numerical testing method is also used in the examination. This study identified the basic requirements for each calibration method to obtain a unique calibration solution. This study also confirmed that the solution becomes more robust if more than sufficient calibration references are provided. Practically, however, as more references are used, more inconsistencies can arise among the measured data for representing the biodynamic properties. To help account for the relative reliabilities of the references, a baseline weighting scheme is proposed. The analyses suggest that the best choice of calibration method depends on the modeling purpose, the model structure, and the availability and reliability of representative reference data. PMID:26740726
NASA Astrophysics Data System (ADS)
Dong, Ren G.; Welcome, Daniel E.; McDowell, Thomas W.; Wu, John Z.
2015-11-01
While simulations of the measured biodynamic responses of the whole human body or body segments to vibration are conventionally interpreted as summaries of biodynamic measurements, and the resulting models are considered quantitative, this study looked at these simulations from a different angle: model calibration. The specific aims of this study are to review and clarify the theoretical basis for model calibration, to help formulate the criteria for calibration validation, and to help appropriately select and apply calibration methods. In addition to established vibration theory, a novel theorem of mechanical vibration is also used to enhance the understanding of the mathematical and physical principles of the calibration. Based on this enhanced understanding, a set of criteria was proposed and used to systematically examine the calibration methods. Besides theoretical analyses, a numerical testing method is also used in the examination. This study identified the basic requirements for each calibration method to obtain a unique calibration solution. This study also confirmed that the solution becomes more robust if more than sufficient calibration references are provided. Practically, however, as more references are used, more inconsistencies can arise among the measured data for representing the biodynamic properties. To help account for the relative reliabilities of the references, a baseline weighting scheme is proposed. The analyses suggest that the best choice of calibration method depends on the modeling purpose, the model structure, and the availability and reliability of representative reference data.
NASA Technical Reports Server (NTRS)
Frady, Gregory P.; Duvall, Lowery D.; Fulcher, Clay W. G.; Laverde, Bruce T.; Hunt, Ronald A.
2011-01-01
A rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for a curved orthogrid panel typical of launch vehicle skin structures. Several test article configurations were produced by adding component equipment of differing weights to the flight-like vehicle panel. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was employed to describe the assumed correlation of phased input sound pressures across the energized panel. This application demonstrates the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software modules developed for the RPTF method can be easily adapted for
NASA Astrophysics Data System (ADS)
Matsumoto, Yasunao; Griffin, Michael J.
2005-11-01
The effect of the magnitude of continuous and transient whole-body vibration in the vertical direction on both subjective and biodynamic responses of human subjects has been investigated experimentally. Additionally, the relation between the subjective responses and the dynamic responses has also been studied. Twelve subjects were exposed to sinusoidal continuous vibrations at five frequencies (3.15-8.0 Hz) and at three magnitudes (0.5-2.0 m s -2 rms). They were also exposed to transient vibrations that were modulated one-and-half cycle sinusoidal waveforms at the same frequencies as the continuous vibrations and at three magnitudes corresponding to the magnitudes used for the continuous vibrations. Discomfort was measured by the method of magnitude estimation with reference stimuli having frequency components in the middle of the frequency range used in this study. The driving-point dynamic responses (the ratio between the force and the motion, i.e., acceleration and velocity, at the driving point) were also measured and divided by the responses to the reference stimuli used in the measurement of discomfort so as to allow the comparison of the dynamic responses with the discomfort responses. Both the discomfort estimates and the normalised driving-point dynamic responses were influenced by the stimuli magnitudes, especially with the continuous vibration. At 3.15 and 4.0 Hz, the discomfort estimates and the normalised mechanical impedance and apparent mass increased significantly with increases in vibration magnitude from 0.5-2.0 m s -2 rms. Magnitude estimates for discomfort were correlated with the normalised mechanical impedance and apparent mass in the frequency range investigated. For the transient vibrations, the discomfort estimates and the driving-point dynamic responses were interpreted as responses in frequency bands around the fundamental frequency of the input motion. The results indicate similar nonlinearities in discomfort and driving-point dynamic
NASA Astrophysics Data System (ADS)
Huang, Ya; Griffin, Michael J.
2008-04-01
The resonance frequencies in frequency response functions of the human body (e.g. apparent mass and transmissibility) decrease with increasing vibration magnitude. This nonlinear biodynamic response is found with various sitting and standing postures requiring postural control. The present study measured the apparent mass of the body in a relaxed semi-supine posture with two types of longitudinal horizontal vibration (in the z-axis of the semi-supine body): (i) continuous random excitation (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75 and 1.0 ms -2 rms); (ii) intermittent random excitation (0.25-20 Hz) alternately at 0.25 and 1.0 ms -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 3.7 to 2.4 Hz as the vibration magnitude increased from 0.125 to 1.0 ms -2 rms. A nonlinear response was apparent in both the horizontal ( z-axis) apparent mass and the vertical ( x-axis) cross-axis apparent mass. With intermittent random vibration, as the vibration magnitude increased from 0.25 to 1.0 ms -2 rms, the median resonance frequency of the apparent mass decreased from 3.2 to 2.5 Hz whereas, with continuous random vibration over the same range of magnitudes, the resonance frequency decreased from 3.4 to 2.4 Hz. The median change in the resonance frequency (between 0.25 and 1.0 ms -2 rms) was 0.6 Hz with the intermittent random vibration and 0.9 Hz with the continuous random vibration. With intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration at the same magnitudes. The responses were consistent with passive thixotropy being a primary cause of nonlinear biodynamic responses to whole-body vibration, although reflex activity of the muscles may also have an influence.
Constrained tibial vibration does not produce an anabolic bone response in adult mice.
Christiansen, Blaine A; Kotiya, Akhilesh A; Silva, Matthew J
2009-10-01
Osteoporosis is characterized by low bone mass and increased fracture risk. High frequency, low-amplitude whole-body vibration (WBV) has been proposed as a treatment for osteoporosis because it can stimulate new bone formation and prevent trabecular bone loss. We developed constrained tibial vibration (CTV) as a method for controlled vibrational loading of the lower leg of a mouse. We first subjected mice to five weeks of daily CTV loading (0.5 G maximum acceleration) with loading parameters chosen to independently investigate the effects of strain magnitude, loading frequency, and cyclic acceleration on the adaptive response to vibration. We hypothesized that mice subjected to the highest magnitude of dynamic strain would have the largest bone formation response. We observed a slight, local benefit of CTV loading on trabecular bone, as BV/TV was 5.2% higher in the loaded vs. non-loaded tibia of mice loaded with the highest bone strain magnitude. However, despite these positive differences, we observed significantly lower measures of trabecular structure in both loaded and non-loaded tibias from CTV loaded mice compared to Sham and Baseline Control animals, indicating a negative systemic effect of CTV on trabecular bone. Based on this evidence, we conducted a follow-up study wherein mice were subjected to CTV or sham loading, and tibias were scanned at the beginning and end of the study period using in vivo microCT. Consistent with the findings of the first study, trabecular BV/TV in both tibias of CTV loaded and Sham mice was, on average, 36% and 31% lower on day 36 than day 0, respectively, compared to 20% lower in Age-Matched Controls over the same time period. Contrary to the first study, there were no differences between loaded and non-loaded tibias in CTV loaded mice, providing no evidence for a local benefit of CTV. In summary, 5 weeks of daily CTV loading of mice was, at best, weakly anabolic for trabecular bone in the proximal tibia, while daily handling
NASA Astrophysics Data System (ADS)
Yang, Yongchao; Nagarajaiah, Satish
2016-06-01
Randomly missing data of structural vibration responses time history often occurs in structural dynamics and health monitoring. For example, structural vibration responses are often corrupted by outliers or erroneous measurements due to sensor malfunction; in wireless sensing platforms, data loss during wireless communication is a common issue. Besides, to alleviate the wireless data sampling or communication burden, certain accounts of data are often discarded during sampling or before transmission. In these and other applications, recovery of the randomly missing structural vibration responses from the available, incomplete data, is essential for system identification and structural health monitoring; it is an ill-posed inverse problem, however. This paper explicitly harnesses the data structure itself-of the structural vibration responses-to address this (inverse) problem. What is relevant is an empirical, but often practically true, observation, that is, typically there are only few modes active in the structural vibration responses; hence a sparse representation (in frequency domain) of the single-channel data vector, or, a low-rank structure (by singular value decomposition) of the multi-channel data matrix. Exploiting such prior knowledge of data structure (intra-channel sparse or inter-channel low-rank), the new theories of ℓ1-minimization sparse recovery and nuclear-norm-minimization low-rank matrix completion enable recovery of the randomly missing or corrupted structural vibration response data. The performance of these two alternatives, in terms of recovery accuracy and computational time under different data missing rates, is investigated on a few structural vibration response data sets-the seismic responses of the super high-rise Canton Tower and the structural health monitoring accelerations of a real large-scale cable-stayed bridge. Encouraging results are obtained and the applicability and limitation of the presented methods are discussed.
Response characteristics of the human torsional vestibuloocular reflex
NASA Technical Reports Server (NTRS)
Peterka, Robert J.
1992-01-01
The characteristics of the response dynamics of the human torsional vestibuloocular reflex were studied during controlled rotations about an earth-horizontal axis. The results extended the frequency range to 2 Hz and identified the nonlinearity of the amplitude response.
An investigation of the vibration characteristics of shrouded-bladed-disk rotor stages
NASA Technical Reports Server (NTRS)
Chen, L.-T.; Dugundji, J.
1979-01-01
Coupled differential equations of motion are given for application to a rotating, pretwisted and heated beam under the effects of thermal stresses and gas bending loads. The circumferential modes of the multi-blade vibration of a bladed-disk rotor stage were studied. A finite element method was developed for the dynamic and static deformation analysis of the blade. The deformations of a bladed disk and a shrouded-bladed disk were studied by introducing a special bladed-disk element and a special shrouded-blade element. Some features of the vibration of part-span-shrouded, bladed-disk rotor stages are discussed. The static deformation, thermal stress and gas bending effects on the blade vibration were presented previously.
Zalesskaya, G.A.; Yakovlev, D.L.
1995-02-01
CO{sub 2} laser-induced delayed fluorescence was used to study the collisional vibration-energy exchange between the polyatomic molecules in gases. The efficiency of collisional exchange, the mean amount of energy transfer in one collision, as well as their correlation with the vibration energy and with the size of excited molecule were determined for diacetyl, acetophenone, benzophenone, and anthraquinone molecules form the experimentally observed pressure dependences of the decay rates and fluorescence intensities. It was shown that the mean amount of energy transfer per collision decreases with the molecular size and increases as E{sup m}, with m>2, with increasing the vibration energy. 25 refs., 4 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Rakheja, S.; Stiharu, I.; Zhang, H.; Boileau, P.-É.
2006-12-01
The relative interactions of the seated occupants with an inclined backrest were investigated in terms of apparent mass (APMS) responses at the two driving-points formed by the buttock-seat pan and the upper body-backrest under exposure to broad-band and road-measured vertical vibration. The measurements were performed using 24 adult subjects seated with full contact with the back support and two different positions of the hands (in lap and on steering wheel), while exposed to three different levels of broad band (0.25, 0.5 and 1.0 m/s 2 rms acceleration) vibration in the 0.5-40 Hz frequency range, and a track-measured vibration spectrum (1.07 m/s 2 rms acceleration). The forces developed on the seat pan and the backrest in directions normal to the supporting surfaces were measured to derive the APMS responses at both the driving-points. The results showed significant interactions of the upper body with the back support in a direction normal to the backrest, even though the vibration is applied along the vertical axis. At low frequencies, the backrest APMS magnitude was smaller than that measured at the seat pan, but it either exceeded or approached that of the seat pan APMS in the vicinity of the primary resonant frequencies. The results also suggested considerable effect of the hands position on the APMS magnitudes measured at both the driving-points. The effects of variations in the excitation type and magnitude, considered in this study, were observed to be small compared to those caused by the hands position and individual body masses. Owing to the strong effects of the body mass on the measured APMS responses at both driving-points, a total of 8 target data sets were identified corresponding to four mass groups (<60, 60.6-70, 70.5-80 and >80 kg) and two hands positions for formulating mechanical equivalent models. The model parameters identified for the target functions suggested that the models mass, stiffness and damping parameters increase with increasing
Physiological response to whole-body vibration in athletes and sedentary subjects.
Gojanovic, B; Feihl, F; Gremion, G; Waeber, B
2014-01-01
Whole-body vibration (WBV) is a new exercise method, with good acceptance among sedentary subjects. The metabolic response to WBV has not been well documented. Three groups of male subjects, inactive (SED), endurance (END) and strength trained (SPRINT) underwent a session of side-alternating WBV composed of three 3-min exercises (isometric half-squat, dynamic squat, dynamic squat with added load), and repeated at three frequencies (20, 26 and 32 Hz). VO(2), heart rate and Borg scale were monitored. Twenty-seven healthy young subjects (10 SED, 8 SPRINT and 9 END) were included. When expressed in % of their maximal value recorded in a treadmill test, both the peak oxygen consumption (VO(2)) and heart rate (HR) attained during WBV were greatest in the SED, compared to the other two groups (VO(2): 59.3 % in SED vs 50.8 % in SPRINT and 48.0 % in END, p<0.01; HR 82.7 % in SED vs 80.4 % in SPRINT and 72.4 % in END, p<0.05). In conclusions, the heart rate and metabolic response to WBV differs according to fitness level and type, exercise type and vibration frequency. In SED, WBV can elicit sufficient cardiovascular response to benefit overall fitness and thus be a potentially useful modality for the reduction of cardiovascular risk. PMID:25157652
Vibration Characteristics of Acoustically Levitated Object with Rigid and Elastic Reflectors
NASA Astrophysics Data System (ADS)
Hong, Zhen-Yu; Xie, Wen-Jun; Wei, Bing-Bo
2010-01-01
Levitation stability is a crucial factor that influences acoustic levitation capability. We present two sample-including models for a single-axis acoustic levitator with either a rigid or elastic reflector. Numerical analysis shows that, with the rigid reflector, both the decay time from initial disturbance and the vibration amplitude increase with sample density, which is unfavorable for levitation stability. However, with the elastic reflector, the decay time and the vibration amplitude are greatly reduced by choosing appropriate parameters of the reflector. Experimental results agree well with theoretical predictions, indicating that levitation stability can be remarkably enhanced by replacing the rigid reflector with an elastic reflector.
EUV/FUV response characteristics of photographic films for the Multi-Spectral Solar Telescope Array
NASA Technical Reports Server (NTRS)
Hoover, Richard B.; Walker, Arthur B. C., Jr.; Deforest, Craig E.; Allen, Maxwell J.; Lindblom, Joakim F.
1991-01-01
The photographic film employed by NASA's Multi-Spectral Solar Telescope Array must have high-to-ultrahigh resolution; since the spacecraft bearing the telescope must be evacuated to prevent the failure of delicate EUV and soft X-ray filters due to acoustic vibration during launch, the films must also have very low outgassing rates. An account is presently given of the properties of important new emulsions selected for flight, together with response-characteristics data for the experimental XUV 100 film and an uncoated Spectroscopic 649 emulsion.
NASA Astrophysics Data System (ADS)
BLÜTHNER, R.; SEIDEL, H.; HINZ, B.
2002-05-01
Back muscle forces contribute essentially to the whole-body vibration-induced spinal load. The electromyogram (EMG) can help to estimate these forces during whole-body vibration (WBV). Thirty-eight subjects were exposed to identical random low-frequency WBV (0·7, 1·0 and 1·4 m/s-2 r.m.s. weighted acceleration) at a relaxed, erect and bent forward postures. The acceleration of the seat and the force between the seat and the buttocks were measured. Six EMGs were derived from the right side of the m. trapezius pars descendens, m. ileocostalis lumborum pars thoracis, m. ileocostalis lumborum pars lumborum; m. longissimus thoracis pars thoracis, m. longissimus thoracis pars lumborum, and lumbar multifidus muscle. All data were filtered for anti-aliasing and sampled with 1000 Hz. Artefacts caused by the ECG in the EMG were identified and eliminated in the time domain using wavelets. The individually rectified and normalized EMGs were averaged across subjects. The EMGs without WBV exhibited characteristic patterns for the three postures examined. The coherence and transfer functions indicated characteristic myoelectric responses to random WBV with several effects of posture and WBV magnitude. A comprehensive set of transfer functions from the seat acceleration or the mean normalized input force to the mean processed EMG was presented.The results can be used for the development of more sophisticated models with a separate control of various back muscle groups. However, the EMG-force relationship under dynamic conditions needs to be examined in more detail before the results can be implemented. Since different reflex mechanisms depending on the frequency of WBV are linked with different types of active muscle fibres, various time delays between the EMG and muscle force may be necessary.
Solar Ultraviolet Magnetograph Investigation (SUMI) Component Responses to Payload Vibration Testing
NASA Technical Reports Server (NTRS)
Hunt, Ronald A.
2011-01-01
Vibration testing of SUMI was performed at both the experiment and payload levels. No accelerometers were installed inside the experiment during testing, but it is certain that component responses were very high. The environments experienced by optical and electronic components in these tests is an area of ongoing concern. The analysis supporting this presentation included a detailed finite element model of the SUMI experiment section, the dynamic response of which, correlated well with accelerometer measurements from the testing of the experimental section at Marshall Space Flight Center. The relatively short timeframe available to complete the task and the limited design information available was a limitation on the level of detail possible for the non-experiment portion of the model. However, since the locations of interest are buried in the experimental section of the model, the calculated responses should be enlightening both for the development of test criteria and for guidance in design.
A Study of the Temperature Characteristics of Vibration Mode Axes for Vibratory Cylinder Gyroscopes
Wu, Yulie; Xi, Xiang; Tao, Yi; Wu, Xiaomei; Wu, Xuezhong
2011-01-01
The zero bias stability, which is an important performance parameter for vibratory cylinder gyroscopes, is high sensitive to temperature change. It is considered that the varying temperature makes the vibration mode axes unstable, which has significant influence on the zero bias stability. This paper will investigate this problem in detail. First, the relationships between the angular positions of vibration mode axes and the zero bias are analyzed. Secondly, the thermal-modal model of the cylinder resonator with several defects such as mass imbalance, frequency split (FS), and geometry errors are developed by ANSYS. Simulation results show that with the increase of temperature, angular positions of the vibration mode axes obviously change, which leads to a dramatic zero bias drift. Finally, several major influence factors on the angular position stability of vibration mode axes, including frequency split, geometry errors, thermal elastic modulus coefficient (TEMC) and thermal expansion coefficient (TEC) are analyzed in detail. Simulation results in this paper will be helpful for deep understanding of the drift principle of zero bias induced by temperature for vibratory cylinder gyroscopes and also be helpful for further temperature compensation or control. PMID:22164038
The Response of Vocal Fold Fibroblasts and Mesenchymal Stromal Cells to Vibration
Gaston, Joel; Quinchia Rios, Beatriz; Bartlett, Rebecca; Berchtold, Craig; Thibeault, Susan L.
2012-01-01
Illumination of cellular changes caused by mechanical forces present within the laryngeal microenvironment may well guide strategies for tissue engineering the vocal fold lamina propria. The purpose of this study was to compare the response of human vocal fold fibroblasts (hVFF) and bone marrow mesenchymal stem cells (BM-MSC) to vibratory stimulus. In order to study these effects, a bioreactor capable of vibrating two cell seeded substrates was developed. The cell seeded substrates contact each other as a result of the sinusoidal frequency, producing a motion similar to the movement of true vocal folds. Utilizing this bioreactor, hVFF and BM-MSC were subjected to 200 Hz vibration and 20% strain for 8 hours. Immunohistochemistry (Ki-67 and TUNEL) was performed to examine cell proliferation and apoptosis respectively, while semi-quantitative RT-PCR was used to assess extracellular matrix related gene expression. HVFF significantly proliferated (p = 0.011) when subjected to 200 Hz vibration and 20% strain, while BM-MSC did not (p = 1.0). A statistically significant increase in apoptosis of BM-MSC (p = 0.0402) was observed under the experimental conditions; however high cell viability (96%) was maintained. HVFF did not have significantly altered apoptosis (p = 0.7849) when subjected to vibration and strain. Semi-quantitative RT-PCR results show no significant differences in expression levels of collagen I (BM-MSC p = 0.1951, hVFF p = v0.3629), fibronectin (BM-MSC p = 0.1951, hVFF p = 0.2513), and TGF-β1 (BM-MSC p = 0.2534, hVFF p = 0.6029) between vibratory and static conditions in either cell type. Finally, smooth muscle actin mRNA was not present in either vibrated or static samples, indicating that no myofibroblast differentiation occurred for either cell type. Together, these results demonstrate that BM-MSC may be a suitable alternative to hVFF for vocal fold tissue engineering. Further investigation into a larger number of
NASA Technical Reports Server (NTRS)
Childs, D. W.; Moyer, D. S.
1985-01-01
A review is presented of various rotordynamic problems which have been encountered and eliminated in developing the current flight engines, and continuing subsynchronous problems which are being encountered in developing a 109% power level engine. The basic model for the High Pressure Oxygen Turbopump (HPOTP) of the SSME including the structural dynamic model for the rotor and housing and component models for the liquid and gas seals, turbine-clearance excitation forces, and impeller-diffuser forces are discussed. Results from a linear model are used to examine the synchronous response and stability characteristics of the HPOTP, examining bearing load and stability problems associated with the second critical speed. Various seal modifications are examined and shown to have favorable consequences with respect to bearing reactions and stability.
NASA Technical Reports Server (NTRS)
Harrison, Phillip; Frady, Greg; Duvall, Lowery; Fulcher, Clay; LaVerde, Bruce
2010-01-01
The development of new launch vehicles in the Aerospace industry often relies on response measurements taken from previously developed vehicles during various stages of liftoff and ascent, and from wind tunnel models. These measurements include sound pressure levels, dynamic pressures in turbulent boundary layers and accelerations. Rigorous statistical scaling methods are applied to the data to derive new environments and estimate the performance of new skin panel structures. Scaling methods have proven to be reliable, particularly for designs similar to the vehicles used as the basis for scaling, and especially in regions of smooth acreage without exterior protuberances or heavy components mounted to the panel. To account for response attenuation of a panel-mounted component due to its apparent mass at higher frequencies, the vibroacoustics engineer often reduces the acreage vibration according to a weight ratio first suggested by Barrett. The accuracy of the reduction is reduced with increased weight of the panel-mounted component, and does not account for low-frequency amplification of the component/panel response as a system. A method is proposed that combines acreage vibration from scaling methods with finite element analysis to account for the frequency-dependent dynamics of heavy panel-mounted components. Since the acreage and mass-loaded skins respond to the same dynamic input pressure, such pressure may be eliminated in favor of a frequency-dependent scaling function applied to the acreage vibration to predict the mass-loaded panel response. The scaling function replaces the Barrett weight ratio, and contains all of the dynamic character of the loaded and unloaded skin panels. The solution simplifies for spatially uncorrelated and fully correlated input pressures. Since the prediction uses finite element models of the loaded and unloaded skins, a rich suite of response data are available to the design engineer, including interface forces, stress and strain
NASA Technical Reports Server (NTRS)
Frady, Gregory P.; Duvall, Lowery D.; Fulcher, Clay W. G.; Laverde, Bruce T.; Hunt, Ronald A.
2011-01-01
rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for component-loaded curved orthogrid panels typical of launch vehicle skin structures. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was applied to correlate the measured input sound pressures across the energized panel. This application quantifies the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software developed for the RPTF method allows easy replacement of the diffuse acoustic field with other pressure fields such as a turbulent boundary layer (TBL) model suitable for vehicle ascent. Structural responses
A study of ribbing effect on the vibration response and transmission of an L-shaped plate.
Lin, Tian Ran; Tan, Jiwen; Zhou, Yifan; Jiang, Jingliang; Zhang, Kai
2016-06-01
This paper presents an analytical solution for the vibration response of a ribbed L-shaped plate using a modal expansion solution approach. The analytical model is then employed to study the ribbing effect on vibration reduction and transmission between the two plate components of the L-shaped plate. It is found that for the system considered in the study, a rib inserted between the excitation force and the source plate can lead to a large vibration reduction for both source and receiving plates except at a frequency band near the fundamental resonant frequency of the rib where the rib's flexural stiffness is negligible. A reduced vibration transmission to the receiving plate can also be achieved by placing a rib near the plate/plate junction, attributed to the increased moment impedance at the coupling after the rib insertion. Increasing the rib's flexural stiffness under this condition can further reduce vibration transmission in the low frequency bands while increasing the rib's mass can lead to a reduced vibration transmission in the higher frequency bands. The insights obtained from this study are relevant to vibration control of structures such as transformer tanks and machine covers. PMID:27369128
Frequency Response of the Sample Vibration Mode in Scanning Probe Acoustic Microscope
NASA Astrophysics Data System (ADS)
Zhao, Ya-Jun; Cheng, Qian; Qian, Meng-Lu
2010-05-01
Based on the interaction mechanism between tip and sample in the contact mode of a scanning probe acoustic microscope (SPAM), an active mass of the sample is introduced in the mass-spring model. The tip motion and frequency response of the sample vibration mode in the SPAM are calculated by the Lagrange equation with dissipation function. For the silicon tip and glass assemblage in the SPAM the frequency response is simulated and it is in agreement with the experimental result. The living myoblast cells on the glass slide are imaged at resonance frequencies of the SPAM system, which are 20kHz, 30kHz and 120kHz. It is shown that good contrast of SPAM images could be obtained when the system is operated at the resonance frequencies of the system in high and low-frequency regions.
Temperature modulation of the vibrational responses of a flexible fluid-conveying pipe
NASA Astrophysics Data System (ADS)
Adelaja, Adekunle
2013-12-01
In this study, the nonlinear transverse vibration of a flexible pipe conveying hot, pressurized fluid is investigated. The pipe which is subjected to a pinned-pinned end condition extends as a result of several operating variables such as internal fluid temperature variation, pre-stress and internal pressurization. The equation of motion is solved analytically by hybrid Fourier-Laplace transforms, and the effects of inlet temperature, temperature gradient, and coefficient of area deformation are investigated on the natural frequencies and transverse dynamic response of the pipeline. While the inlet temperature and temperature gradient are found to be inversely proportional to the natural frequencies and amplitude of the dynamic response, increase in the coefficient of area deformation has little effect on the natural frequencies for the particular case considered.
Fares, Elie-Jacques; Charrière, Nathalie; Montani, Jean-Pierre; Schutz, Yves; Dulloo, Abdul G.; Miles-Chan, Jennifer L.
2016-01-01
Background and Aim There is increasing recognition about the importance of enhancing energy expenditure (EE) for weight control through increases in low-intensity physical activities comparable with daily life (1.5–4 METS). Whole-body vibration (WBV) increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a “dose-response” exists between commonly-used vibration frequencies (VF) and EE, nor if WBV influences respiratory quotient (RQ), and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz). Methods EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz). Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest), separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest) at 40 Hz, separated by 5 min seated rest. Results Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001). However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration. Conclusion No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS). PMID:26974147
Dynamic characteristics of heat exchanger tubes vibrating in a tube support plate inactive mode
Jendrzejczyk, J.A.
1984-06-01
Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contract all of the TSPs. Noncontact results in an inactive TSP which can lead to detrimental flow induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimental quantities.
Dynamic characteristics of heat exchanger tubes vibrating in a tube support plate inactive mode
Jendrzejczyk, J.A.
1985-01-01
Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contact all of the TSPs. Noncontact results in an inactive TSP which can lead to detrimental flow induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimetnal quantities.
Effect of radial stretch on vibration characteristics of single-layered circular graphene sheets
NASA Astrophysics Data System (ADS)
Pahlani, Gunjan; Verma, Deepti; Gupta, Shakti
Vibrations of single-layered circular graphene sheets are studied using molecular mechanics (MM) simulations. Interactions between bonded and non-bonded atoms are prescribed using MM3 potential. Frequencies of different modes of vibration are computed from the eigenvalues and eigen vectors of mass weighted Hessian of the system. This study is performed on graphene sheets of various diameters. A linear continuum membrane model for predicting vibrational frequencies is studied using finite element (FE) method. Frequencies for several modes computed from continuum and molecular model matched well for moderate values of radial stretch, however, with increased stretch those deviated from each other significantly. In particular for higher values of stretch the MM simulations predict considerably lower values of frequencies compared to that found from FE simulations. Also, at higher values of stretch the frequency vs. stretch curve obtained from MM simulations showed a hardening behavior which could not be captured by the linear continuum model. We have also found a similar behavior in two-layered graphene sheets using MM simulations.
Cao, Hongrui; Niu, Linkai; He, Zhengjia
2012-01-01
Bearing defects are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this study, an integrated finite element (FE) model is proposed to predict the vibration responses of a spindle bearing system with localized bearing defects and then the sensor placement for better detection of bearing faults is optimized. A nonlinear bearing model is developed based on Jones' bearing theory, while the drawbar, shaft and housing are modeled as Timoshenko's beam. The bearing model is then integrated into the FE model of drawbar/shaft/housing by assembling equations of motion. The Newmark time integration method is used to solve the vibration responses numerically. The FE model of the spindle-bearing system was verified by conducting dynamic tests. Then, the localized bearing defects were modeled and vibration responses generated by the outer ring defect were simulated as an illustration. The optimization scheme of the sensor placement was carried out on the test spindle. The results proved that, the optimal sensor placement depends on the vibration modes under different boundary conditions and the transfer path between the excitation and the response. PMID:23012514
Glasser, S; Collings, R; Paton, J; Marsden, J
2015-07-01
This study assessed whether postural responses induced by vibratory perturbations of the hip abductors and ankle evertors, were modified when distal tactile sensation was experimentally reduced through cooling. Sixteen healthy subjects were investigated pre and post cooling. Subjects stood with their eyes closed with a stance width of 4 cm. A 2s vibratory stimulus was applied to the left or right hip abductor or ankle evertor muscle. The order of the site and side of the stimulation was randomised. The postural response to hip abductor and ankle evertor vibration was recorded using 3D motion analysis (Codamotion, Leicestershire). Medio-lateral centre of pressure motion was simultaneously recorded during quiet standing via a force plate (Kistler, UK). Pre-cooling people responded to unilateral ankle vibration with an ipsilateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. People responded to unilateral hip vibration with a contralateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. Following an experimental reduction in distal tactile sensation there was a significant reduction in the amplitude of pelvic tilt in response to ankle vibration (F(6.2)=P<0.05) and a significant increase in amplitude of pelvic tilt in response to hip vibration (F(5.2)=P<0.05). This suggests that the sensitivity to artificial stimulation of hip proprioception increases with distal cooling, possibly indicating a change in the gain/weighting placed upon sensory information from the hips. PMID:26153881
NASA Astrophysics Data System (ADS)
Godtliebsen, Ian H.; Hansen, Mads Bøttger; Christiansen, Ove
2015-01-01
We show how the eigenvalue equations of vibrational coupled cluster response theory can be solved using a subspace projection method with Davidson update, where basis vectors are stacked tensors decomposed into canonical (CP, Candecomp/Parafac) form. In each update step, new vectors are first orthogonalized to old vectors, followed by a tensor decomposition to a prescribed threshold TCP. The algorithm can provide excitation energies and eigenvectors of similar accuracy as a full vector approach and with only a very modest increase in the number of vectors required for convergence. The algorithm is illustrated with sample calculations for formaldehyde, 1,2,5-thiadiazole, and water. Analysis of the formaldehyde and thiadiazole calculations illustrate a number of interesting features of the algorithm. For example, the tensor decomposition threshold is optimally put to rather loose values, such as TCP = 10-2. With such thresholds for the tensor decompositions, the original eigenvalue equations can still be solved accurately. It is thus possible to directly calculate vibrational wave functions in tensor decomposed format.
Frequency weighting for vibration-induced white finger compatible with exposure-response models.
Brammer, Anthony J; Pitts, Paul M
2012-01-01
An analysis has been performed to derive a frequency weighting for the development of vibration-induced white finger (VWF). It employs a model to compare health risks for pairs of population groups that are selected to have similar health outcomes from operating power tools or machines with markedly different acceleration spectra (rock drills, chain saws, pavement breakers and motorcycles). The model defines the Relative Risk, RR(f(trial)), which is constructed from the ratio of daily exposures and includes a trial frequency weighting that is applied to the acceleration spectra. The trial frequency weighting consists of a frequency-independent primary frequency range, and subordinate frequency ranges in which the response to vibration diminishes, with cut-off frequencies that are changed to influence the magnitude of RR(f(trial)). The frequency weighting so derived when RR(f(trial)) = 1 is similar to those obtained by other methods (W(hf), W(hT)). It consists of a frequency independent range from about 25 Hz to 500 Hz (-3 dB frequencies), with an amplitude cut-off rate of 12 dB/octave below 25 Hz and above 500 Hz. The range is compatible with studies of vasoconstriction in persons with VWF. The results provide further evidence that the ISO frequency weighting may be inappropriate for assessing the risk of developing VWF. PMID:23060253
Acute Bone Marker Responses to Whole-Body Vibration and Resistance Exercise in Young Women
Sherk, Vanessa D.; Chrisman, Carmen; Smith, Jessica; Young, Kaelin C.; Singh, Harshvardhan; Bemben, Michael G.; Bemben, Debra A.
2014-01-01
Whole-body vibration (WBV) augments the musculoskeletal effects of resistance exercise (RE). However, its acute effects on bone turnover markers (BTM) have not been determined. This study examined BTM responses to acute high intensity RE and high intensity RE with WBV (WBV+RE) in young women (n=10) taking oral contraceptives in a randomized, cross-over repeated measures design. WBV+RE exposed subjects to 5 one-minute bouts of vibration (20 Hz, 3.38 peak–peak displacement, separated by 1 minute of rest) prior to RE. Fasting blood samples were obtained before (Pre), immediately post WBV (PostVib), immediately post RE (IP), and 30 minutes post RE (P30). Bone ALP did not change at any time point. TRAP5b significantly (p<0.05) increased from the Pre to PostVib, then decreased from IP to P30 for both conditions. CTX significantly decreased (p<0.05) from Pre to PostVib and from Pre to P30 only for WBV+RE. WBV+RE showed a greater decrease in CTX than RE (-12.6 ± 4.7% vs. -1.13 ± 3.5%). In conclusion, WBV was associated with acute decreases in CTX levels not elicited with resistance exercise alone in young women. PMID:22902255
NASA Technical Reports Server (NTRS)
Bielawa, Richard L.; Hefner, Rachel E.; Castagna, Andre
1991-01-01
The results are presented of an analytic and experimental research program involving a Sikorsky S-55 helicopter tail cone directed ultimately to the improved structural analysis of airframe substructures typical of moderate sized helicopters of metal semimonocoque construction. Experimental static strain and dynamic shake-testing measurements are presented. Correlation studies of each of these tests with a PC-based finite element analysis (COSMOS/M) are described. The tests included static loadings at the end of the tail cone supported in the cantilever configuration as well as vibrational shake-testing in both the cantilever and free-free configurations.
Dutta, P. K.; Hatfield, R. W.; Runstadler, Jr., P. W.
1981-10-01
This report describes calibration studies of the IRAD GAGE Vibrating Wire Stressmeter. The work has been performed for the University of California, Lawrence Livermore Laboratory, to understand and interpret the behavior and performance of the stressmeter in Climax granite. To help interpret the results obtained in Climax granite, the study also included calibration tests of the gage in other materials: Barre granite, aluminum, and Lucite. Stressmeter calibrations were carried out in thin rock slabs by determining the relation between the stressmeter readings and uniaxial plane stresses. Calibrations were also conducted under biaxial and triaxial stress fields.
The impact of unilateral vibrations on aerodynamic characteristics of airfoils in transonic flow
NASA Astrophysics Data System (ADS)
Zamuraev, V.; Kalinina, A.
2016-06-01
The work is devoted to the mathematical modeling of the influence of forced vibrations of a surface element on one side of the airfoil on the shock-wave structure of transonic flow around. The influence of parameters of oscillations on the airfoil wave drag and the lift force were qualitatively and quantitatively investigated for constant maximum velocity amplitude, which is close in magnitude to the sound velocity in the incoming flow, and for a wide range of frequencies. The arising of additional lift force is shown.
NASA Technical Reports Server (NTRS)
Robertson, D. K.
1984-01-01
Partial differential equations are derived for free lateral and torsional vibration of a uniform free-free beam with a rotational mass attached to each extremity. For appropriate boundary conditions, nonlinear algebraic equations are obtained using a symbolic manipulation computer program, the solutions of which enable the computation of the neutral frequencies and mode-shapes. The mode-shapes are linear combinations of trigonometric and hyperbolic sine and cosine functions. A computer program is written for the numerical solution of the algebraic equations mentioned above, which can compute the natural frequencies, mode-shapes, and node points for any given set of parameters, for any given number of modes.
NASA Astrophysics Data System (ADS)
Hong, Sung-Kwon; Castanier, Matthew P.; Epureanu, Bogdan I.
2009-03-01
Modeling and re-analysis techniques are proposed for predicting the dynamic response of complex structures that have suffered damage in one or more of their components. When such damages are present, the model of the healthy structure may no longer capture the system-level response or the loading from the rest of the structure on the damaged components. Hence, novel models that allow for an accurate re-analysis of the response of damaged structures are needed in important applications, including damage detection. Herein, such models are obtained by using a reduced order modeling approach based on component mode synthesis. Because the resonant response of a complex structure is often sensitive to component uncertainties (in geometric parameters such as thickness, material properties such as Young's modulus, etc.), novel parametric reduced order models (PROMs) are developed. In previous work, PROMs have been applied for handling uncertainties in a single substructure. Herein, PROMs are extended to the general case of multiple substructures with uncertain parameters or damage. Two damage cases are considered: severe structural deformation (dents), and cracks. For the first damage case, an approximate method based on static mode compensation (SMC) is used to perform fast re-analysis of the vibration response of the damaged structure. The re-analysis is performed through a range of locations and severity levels of the damage. For selected damage locations and levels, the SMC approximation is compared to full finite element analysis to demonstrate the accuracy and computational time savings for the new method. For the second damage case (cracks), the vibration problem becomes nonlinear due to the intermittent contact of the crack faces. Therefore, to estimate the resonant frequencies for a cracked structure, the bi-linear frequency approximation (BFA) is used for cracks of various lengths. Since BFA is based on linear analyses, it is fast and particularly well suited for
NASA Astrophysics Data System (ADS)
Belliard, Laurent; Cornelius, Thomas W.; Perrin, Bernard; Kacemi, Nazim; Becerra, Loïc; Thomas, Olivier; Eugenia Toimil-Molares, Maria; Cassinelli, Marco
2013-11-01
We report on the ultrafast vibrational response of single copper nanowires investigated by femtosecond transient reflectivity measurements. The oscillations of the sample reflectivity are correlated with individual modes of resonance for wires with a diameter ranging from 100 to 500 nm and are compared with 2D finite element simulation. Fluctuation of the sample-substrate coupling is illustrated through its effect on the damping rate. We demonstrate elastic confinement in free standing wires which allowed the detection of up to the third harmonic of the breathing mode. By removing the energy relaxation channel towards the substrate, we obtained nano-oscillators with quality factors up to 130. Finally, taking advantage of the very high spectral resolution achieved on free standing wires, we could observe the elastic coupling between two close wires via their polymer cladding.
NASA Astrophysics Data System (ADS)
Zhang, Xiao-Ming; Ding, Han
2008-11-01
The concept of uncertainty plays an important role in the design of practical mechanical system. The most common methods for solving uncertainty problems are to model the parameters as a random vector. A natural way to handle the randomness is to admit that a given probability density function represents the uncertainty distribution. However, the drawback of this approach is that the probability distribution is difficult to obtain. In this paper, we use the non-probabilistic convex model to deal with the uncertain parameters in which there is no need for probability density functions. Using the convex model theory, a new method to optimize the dynamic response of mechanical system with uncertain parameters is derived. Because the uncertain parameters can be selected as the optimization parameters, the present method can provide more information about the optimization results than those obtained by the deterministic optimization. The present method is implemented for a torsional vibration system. The numerical results show that the method is effective.
The response of a plate bonded to a randomly vibrating viscoelastic half-space.
NASA Technical Reports Server (NTRS)
Remington, P. J.
1972-01-01
The response of an infinite Bernoulli-Euler plate placed on the surface of a randomly vibrating viscoelastic half-space is calculated, allowing for the presence of shear stresses between the plate and the half-space. The shear stresses arise from the condition that the relative motion between the plate and the half-space vanishes at the interface. The three components of displacement of the free surface of the half-space before the plate is added are assumed to be stationary homogeneous random functions of position and time. From the wavenumber-frequency spectra of these displacements the frequency spectra of the three components of displacement of the plate half-space interface are calculated. As an example, the frequency spectrum of the vertical interface displacement is calculated for two assumed forms of the wavenumber spectra of the free-surface displacements.
Psychosocial Characteristics Mediating the Response: An Exploratory Study.
ERIC Educational Resources Information Center
Witmer, J. Melvin; And Others
1983-01-01
Examined the psychosocial characteristics that cognitively mediate between life stressors and the stress response in 235 subjects. Results from the five instruments used showed self-esteem was by far the most important characteristic discriminating between good and poor copers. Other factors were external control, life pace and irrational beliefs.…
Vibration damping characteristics of graphite/epoxy composites for large space structures
NASA Technical Reports Server (NTRS)
Gibson, R. F.
1982-01-01
Limited data on extensional and flexural damping of small specimens of graphite/epoxy and unreinforced epoxy resin were obtained. Flexural damping was measured using a forced vibration technique based on resonant flexural vibration of shaker excited double cantilever specimens. Extensional damping was measured by subjecting similar specimens to low frequency sinusoidal oscillation in a servohydraulic tensile testing machine while plotting load versus extensional strain. Damping was found to vary slowly and continuously over the frequency range 0.01 - 1000 Hz, and no drastic transitions were observed. Composite damping was found to be less than neat resin damping. Comparison of small specimen damping values with assembled column damping values seems to indicate that, for those materials, material damping is more important than joint damping. The data reported was limited not by the test apparatus, but by signal conditioning and data acquisition. It is believed that filtering of the strain gage signals and the use of digital storage with slow playback will make it possible to extend the frequency and amplitude ranges significantly.
Qiu, Yi; Griffin, Michael J
2012-01-01
The biodynamic responses to the human body give an understanding of why human responses to vibration (changes in health, comfort, and performance) vary with the frequency and direction of vibration. Studies have shown that biodynamic responses also vary with the magnitude of vibration and that the backrests of seats influence the transmission of vibration to the seated human body. There has been little study of the nonlinearity in the biodynamic responses of the body to dual-axis excitation and no study of the influence of backrests during dual-axis excitation. This study investigated the apparent mass and cross-axis apparent mass of the human body exposed to random vibration (0.2 to 20 Hz) in all 15 possible combinations of four magnitudes (0, 0.25, 0.5 and 1.0 ms(-2) r.m.s.) of fore-and-aft vibration and the same four magnitudes of vertical vibration. Nonlinearity was evident, with the body softening with increasing magnitude of vibration when using a fixed magnitude of vibration in one direction and varying the magnitude of vibration in the other direction. The fore-and-aft apparent mass on the seat was greater without a backrest at the lower frequencies but greater with a backrest at the higher frequencies. The vertical apparent mass on the seat was decreased by the backrest at low frequencies. Cross-axis coupling was evident, with excitation in one axis producing a response in the other axis. It is concluded that the nonlinearity of the body evident during single-axis and multi-axis vibration, and the influence of backrests, should be taken into account when determining frequency weightings for predicting human responses to vibration and when optimising the dynamics of seating to minimise exposure to vibration. PMID:22146145
Dynamic response characteristics of two transport models tested in the National Transonic Facility
NASA Technical Reports Server (NTRS)
Young, Clarence P., Jr.
1993-01-01
This paper documents recent experiences with measuring the dynamic response characteristics of a commercial transport and a military transport model during full scale Reynolds number tests in the National Transonic Facility. Both models were limited in angle of attack while testing at full scale Reynolds number and cruise Mach number due to pitch or stall buffet response. Roll buffet (wing buzz) was observed for both models at certain Mach numbers while testing at high Reynolds number. Roll buffet was more severe and more repeatable for the military transport model at cruise Mach number. Miniature strain-gage type accelerometers were used for the first time for obtaining dynamic data as a part of the continuing development of miniature dynamic measurements instrumentation for cryogenic applications. This paper presents the results of vibration measurements obtained for both the commercial and military transport models and documents the experience gained in the use of miniature strain gage type accelerometers.
NASA Astrophysics Data System (ADS)
Ganguli, R.
2002-11-01
An aeroelastic analysis based on finite elements in space and time is used to model the helicopter rotor in forward flight. The rotor blade is represented as an elastic cantilever beam undergoing flap and lag bending, elastic torsion and axial deformations. The objective of the improved design is to reduce vibratory loads at the rotor hub that are the main source of helicopter vibration. Constraints are imposed on aeroelastic stability, and move limits are imposed on the blade elastic stiffness design variables. Using the aeroelastic analysis, response surface approximations are constructed for the objective function (vibratory hub loads). It is found that second order polynomial response surfaces constructed using the central composite design of the theory of design of experiments adequately represents the aeroelastic model in the vicinity of the baseline design. Optimization results show a reduction in the objective function of about 30 per cent. A key accomplishment of this paper is the decoupling of the analysis problem and the optimization problems using response surface methods, which should encourage the use of optimization methods by the helicopter industry.
G-seat system step input and sinusoidal response characteristics
NASA Technical Reports Server (NTRS)
Showalter, T. W.; Miller, R. J.
1978-01-01
The step input and sinusoidal response characteristics of a pneumatically driven computer controlled G set are examined in this study. The response data show that this system can be modeled as a first order system with an 0.08 sec time lag and a 0.53 sec time constant.
NASA Astrophysics Data System (ADS)
MATSUMOTO, Y.; GRIFFIN, M. J.
2002-03-01
The effect of the “phase” on human responses to vertical whole-body vibration and shock has been investigated analytically using alternative methods of predicting subjective responses (using r.m.s., VDV and various frequency weightings). Two types of phase have been investigated: the effect of the relative phase between two frequency components in the input stimulus, and the phase response of the human body. Continuous vibrations and shocks, based on half-sine and one-and-a-half-sine accelerations, each of which had two frequency components, were used as input stimuli. For the continuous vibrations, an effect of relative phase was found for the vibration dose value (VDV) when the ratio between two frequency components was three: about 12% variation in the VDV of the unweighted acceleration was possible by changing the relative phase. The effect of the phase response of the body represented by frequency weightings was most significant when the frequencies of two sinusoidal components were about 3 and 9 Hz. With shocks, the effect of relative phase was observed for all stimuli used. The variation in the r.m.s. acceleration and in the VDV caused by variations in the relative phase varied between 3 and 100%, depending on the nature of stimulus and the frequency weighting. The phase of the frequency weightings had a different effect on the r.m.s. and the VDV.
Optical measurement of the weak non-linearity in the eardrum vibration response to auditory stimuli
NASA Astrophysics Data System (ADS)
Aerts, Johan
The mammalian hearing organ consists of the external ear (auricle and ear canal) followed by the middle ear (eardrum and ossicles) and the inner ear (cochlea). Its function is to convert the incoming sound waves and convert them into nerve pulses which are processed in the final stage by the brain. The main task of the external and middle ear is to concentrate the incoming sound waves on a smaller surface to reduce the loss that would normally occur in transmission from air to inner ear fluid. In the past it has been shown that this is a linear process, thus without serious distortions, for sound waves going up to pressures of 130 dB SPL (˜90 Pa). However, at large pressure changes up to several kPa, the middle ear movement clearly shows non-linear behaviour. Thus, it is possible that some small non-linear distortions are also present in the middle ear vibration at lower sound pressures. In this thesis a sensitive measurement set-up is presented to detect this weak non-linear behaviour. Essentially, this set-up consists of a loud-speaker which excites the middle ear, and the resulting vibration is measured with an heterodyne vibrometer. The use of specially designed acoustic excitation signals (odd random phase multisines) enables the separation of the linear and non-linear response. The application of this technique on the middle ear demonstrates that there are already non-linear distortions present in the vibration of the middle ear at a sound pressure of 93 dB SPL. This non-linear component also grows strongly with increasing sound pressure. Knowledge of this non-linear component can contribute to the improvement of modern hearing aids, which operate at higher sound pressures where the non-linearities could distort the signal considerably. It is also important to know the contribution of middle ear non-linearity to otoacoustic emissions. This are non-linearities caused by the active feedback amplifier in the inner ear, and can be detected in the external and
2010-01-01
Background We evaluated pulmonologists variability in the interpretation of Vibration response imaging (VRI) obtained from healthy subjects and patients hospitalized for community acquired pneumonia. Methods The present is a prospective study conducted in a tertiary university hospital. Twenty healthy subjects and twenty three pneumonia cases were included in this study. Six pulmonologists blindly analyzed images of normal subjects and pneumonia cases and evaluated different aspects of VRI images related to the quality of data aquisition, synchronization of the progression of breath sound distribution and agreement between the maximal energy frame (MEF) of VRI (which is the maximal geographical area of lung vibrations produced at maximal inspiration) and chest radiography. For qualitative assessment of VRI images, the raters' evaluations were analyzed by degree of consistency and agreement. Results The average value for overall identical evaluations of twelve features of the VRI image evaluation, ranged from 87% to 95% per rater (94% to 97% in control cases and from 79% to 93% per rater in pneumonia cases). Inter-rater median (IQR) agreement was 91% (82-96). The level of agreement according to VRI feature evaluated was in most cases over 80%; intra-class correlation (ICC) obtained by using a model of subject/rater for the averaged features was overall 0.86 (0.92 in normal and 0.73 in pneumonia cases). Conclusions Our findings suggest good agreement in the interpretation of VRI data between different raters. In this respect, VRI might be helpful as a radiation free diagnostic tool for the management of pneumonia. PMID:20222975
Cap, J.S.
1997-11-01
Defining the maximum expected shock and vibration responses for an on-road truck transportation environment is strongly dependent on the amount of response data that can be obtained. One common test scheme consists of measuring response data over a relatively short prescribed road course and then reviewing that data to obtain the maximum response levels. The more mathematically rigorous alternative is to collect an unbiased ensemble of response data during a long road trip. This paper compares data gathered both ways during a recent on-road certification test for a tractor trailer van being designed by Sandia.
Vibration signature analysis of multistage gear transmission
NASA Technical Reports Server (NTRS)
Choy, F. K.; Tu, Y. K.; Savage, M.; Townsend, D. P.
1989-01-01
An analysis is presented for multistage multimesh gear transmission systems. The analysis predicts the overall system dynamics and the transmissibility to the gear box or the enclosed structure. The modal synthesis approach of the analysis treats the uncoupled lateral/torsional model characteristics of each stage or component independently. The vibration signature analysis evaluates the global dynamics coupling in the system. The method synthesizes the interaction of each modal component or stage with the nonlinear gear mesh dynamics and the modal support geometry characteristics. The analysis simulates transient and steady state vibration events to determine the resulting torque variations, speeds, changes, rotor imbalances, and support gear box motion excitations. A vibration signature analysis examines the overall dynamic characteristics of the system, and the individual model component responses. The gear box vibration analysis also examines the spectral characteristics of the support system.
Free-vibration characteristics of a large split-blanket solar array in a 1-g field
NASA Technical Reports Server (NTRS)
Shaker, F. J.
1976-01-01
Two methods for studying the free vibration characteristics of a large split blanket solar array in both a 0-g and a 1-g cantilevered configuration are presented. The 0-g configuration corresponds to an in-orbit configuration of the array; the 1-g configuration is a typical ground test configuration. The first method applies the equations of continuum mechanics to determine the mode shapes and frequencies of the array; the second method uses the Rayleigh-Ritz approach. In the Rayleigh-Ritz method the array displacements are represented by string modes and cantilevered beam modes. The results of this investigation are summarized by a series of graphs illustrating the effects of various array parameters on the mode shapes and frequencies of the system. The results of the two methods are also compared in tabular form.
Abraham, Alon; Albulaihe, Hana; Alabdali, Majed; Qrimli, Mohammad; Breiner, Ari; Barnett, Carolina; Katzberg, Hans D.; Lovblom, Leif E.; Perkins, Bruce A.; Bril, Vera
2015-01-01
Introduction Vibration perception threshold (VPT) examination using a neurothesiometer provides objective, sensitive and specific information, and has been utilized mainly in patients with diabetic polyneropathy. Objectives Explore the utility of VPT examination in CIDP patients. Methods CIDP subjects attending the Neuromuscular clinic between 01/2013 and 12/2014 were evaluated. Demographic data, clinical history, physical examination, VPT values, and electrophysiologic data from their charts were extracted. Results 70 charts were reviewed. 55 CIDP patients had elevated VPT, associated with higher frequency of abnormal sensory testing for various modalities (92.7% vs. 46.7%, p<0.0001), lower sensory and motor amplitudes and reduced conduction velocities on nerve conduction studies, and lower treatment response rates (54% vs. 93%, p = 0.01). Conclusion VPT examination is a simple tool, which is a reliable and sensitive measure not only for diabetic neuropathy, but also for CIDP. Moreover, in CIDP, elevated VPT values are also associated with lower treatment response rates. PMID:26545096
Fard, Mohammad A; Ishihara, Tadashi; Inooka, Hikaru
2003-08-01
Although many studies exist concerning the influence of seat vibration on the head in the seated human body, the dynamic response of the head-neck complex (HNC) to the trunk vibration has not been well investigated. Little quantitative knowledge exists about viscoelastic parameters of the neck. In this study, the dynamics of the HNC is identified when it is exposed to the trunk horizontal (fore-and-aft) vibration. The frequency response functions between the HNC angular velocity and the trunk horizontal acceleration, corresponding to four volunteers, are obtained in the frequency range of 0.5 Hz to 10 Hz. A fourth-order mathematical model, derived by considering a double-inverted-pendulum model for the HNC, is designed to simulate the dynamic response of the HNC to the trunk horizontal vibration. The frequency domain identification method is used to determine the coefficients of the mathematical model of the HNC. Good agreement has been obtained between experimental and simulation results. This indicates that the system, similar to the designed fourth-order model, has mainly two resonance frequencies. The viscoelastic parameters of the neck, including the spring and damping coefficients, are then obtained by use of the optimization method. PMID:12968578