Benefits of Spacecraft Level Vibration Testing

NASA Technical Reports Server (NTRS)

Gordon, Scott; Kern, Dennis L.

2015-01-01

NASA-HDBK-7008 Spacecraft Level Dynamic Environments Testing discusses the approaches, benefits, dangers, and recommended practices for spacecraft level dynamic environments testing, including vibration testing. This paper discusses in additional detail the benefits and actual experiences of vibration testing spacecraft for NASA Goddard Space Flight Center (GSFC) and Jet Propulsion Laboratory (JPL) flight projects. JPL and GSFC have both similarities and differences in their spacecraft level vibration test approach: JPL uses a random vibration input and a frequency range usually starting at 5 Hz and extending to as high as 250 Hz. GSFC uses a sine sweep vibration input and a frequency range usually starting at 5 Hz and extending only to the limits of the coupled loads analysis (typically 50 to 60 Hz). However, both JPL and GSFC use force limiting to realistically notch spacecraft resonances and response (acceleration) limiting as necessary to protect spacecraft structure and hardware from exceeding design strength capabilities. Despite GSFC and JPL differences in spacecraft level vibration test approaches, both have uncovered a significant number of spacecraft design and workmanship anomalies in vibration tests. This paper will give an overview of JPL and GSFC spacecraft vibration testing approaches and provide a detailed description of spacecraft anomalies revealed.

49 CFR Appendix C to Part 173 - Procedure for Base-level Vibration Testing

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Procedure for Base-level Vibration Testing C Appendix C to Part 173 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... Base-level Vibration Testing Base-level vibration testing shall be conducted as follows: 1. Three...

49 CFR Appendix C to Part 173 - Procedure for Base-level Vibration Testing

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Procedure for Base-level Vibration Testing C Appendix C to Part 173 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... Base-level Vibration Testing Base-level vibration testing shall be conducted as follows: 1. Three...

Centaur liquid oxygen boost pump vibration test

NASA Technical Reports Server (NTRS)

Tang, H. M.

1975-01-01

The Centaur LOX boost pump was subjected to both the simulated Titan Centaur proof flight and confidence demonstration vibration test levels. For each test level, both sinusoidal and random vibration tests were conducted along each of the three orthogonal axes of the pump and turbine assembly. In addition to these tests, low frequency longitudinal vibration tests for both levels were conducted. All tests were successfully completed without damage to the boost pump.

Vibration Testing of Stirling Power Convertors

NASA Technical Reports Server (NTRS)

Hughes, Bill; Goodnight, Thomas; McNelis, Mark E.; Suarez, Vicente J.; Schreiber, Jeff; Samorezov, Sergey

2003-01-01

The NASA John H. Glenn Research Center (GRC) and the U.S. Department of Energy (DOE) are currently developing a high efficient, long life, free piston Stirling convertor for use as an advanced spacecraft power system for future NASA missions. As part of this development, a Stirling Technology Demonstrator Convertor (TDC), developed by Stirling Technology Company (STC) for DOE, was vibration tested at GRC s Structural Dynamics Laboratory (SDU7735) in November- December 1999. This testing demonstrated that the Stirling TDC is able to withstand the harsh random vibration (20 to 2000 Hertz) seen during a typical spacecraft launch and survive with no structural damage or functional power performance degradation, thereby enabling its usage in future spacecraft power systems. The Stirling Vibration Test Team at NASA GRC and STC personnel conducted tests on a single 55 electric watt TDC. The purpose was to characterize the TDC s structural response to vibration and determine if the TDC could survive the vibration criteria established by the Jet Propulsion Laboratory (JPL) for launch environments. The TDC was operated at full-stroke and full power conditions during the vibration testing. The TDC was tested in two orientations, with the direction of vibration parallel and perpendicular to the TDC s moving components (displacer and piston). The TDC successfully passed a series of sine and random vibration tests. The most severe test was a 12.3 Grms random vibration test (peak vibration level of 0.2 g2/Hz from 50 to 250 Hertz) with test durations of 3 minutes per axis. The random vibration test levels were chosen to simulate, with margin, the maximum anticipated launch vibration conditions. As a result of this very successful vibration testing and successful evaluations in other key technical readiness areas, the Stirling power system is now considered a viable technology for future application for NASA spacecraft missions. Possible usage of the Stirling power system would be to supply on- board electric spacecraft power for future NASA Deep-Space Missions, performing as an attractive alternative to Radioisotope Thermoelectric Generators (RTG). Usage of the Stirling technology is also being considered as the electric power source for future Mars rovers, whose mission profiles may exclude the use of photovoltaic power systems (such as exploring at high Martian latitudes or for missions of lengthy durations). GRC s Thermo-Mechanical Systems Branch (5490) provides Stirling technology expertise under a Space Act Agreement with the DOE. Additional vibration testing, by GRC s Structural Systems Dynamics Branch (7733, is planned to continue to demonstrate the Stirling power system s vibration capability as its technology and flight system designs progress.

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.

A micro-vibration generated method for testing the imaging quality on ground of space remote sensing

NASA Astrophysics Data System (ADS)

Gu, Yingying; Wang, Li; Wu, Qingwen

2018-03-01

In this paper, a novel method is proposed, which can simulate satellite platform micro-vibration and test the impact of satellite micro-vibration on imaging quality of space optical remote sensor on ground. The method can generate micro-vibration of satellite platform in orbit from vibrational degrees of freedom, spectrum, magnitude, and coupling path. Experiment results show that the relative error of acceleration control is within 7%, in frequencies from 7Hz to 40Hz. Utilizing this method, the system level test about the micro-vibration impact on imaging quality of space optical remote sensor can be realized. This method will have an important applications in testing micro-vibration tolerance margin of optical remote sensor, verifying vibration isolation and suppression performance of optical remote sensor, exploring the principle of micro-vibration impact on imaging quality of optical remote sensor.

Validation of Force Limited Vibration Testing at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Rice, Chad; Buehrle, Ralph D.

2003-01-01

Vibration tests were performed to develop and validate the forced limited vibration testing capability at the NASA Langley Research Center. The force limited vibration test technique has been utilized at the Jet Propulsion Laboratory and other NASA centers to provide more realistic vibration test environments for aerospace flight hardware. In standard random vibration tests, the payload is mounted to a rigid fixture and the interface acceleration is controlled to a specified level based on a conservative estimate of the expected flight environment. In force limited vibration tests, both the acceleration and force are controlled at the mounting interface to compensate for differences between the flexible flight mounting and rigid test fixture. This minimizes the over test at the payload natural frequencies and results in more realistic forces being transmitted at the mounting interface. Force and acceleration response data was provided by NASA Goddard Space Flight Center for a test article that was flown in 1998 on a Black Brant sounding rocket. The measured flight interface acceleration data was used as the reference acceleration spectrum. Using this acceleration spectrum, three analytical methods were used to estimate the force limits. Standard random and force limited vibration tests were performed and the results are compared with the flight data.

Data of piezoelectric vibration energy harvesting of a bridge undergoing vibration testing and train passage.

PubMed

Cahill, Paul; Hazra, Budhaditya; Karoumi, Raid; Mathewson, Alan; Pakrashi, Vikram

2018-04-01

The data presented in this article is in relation to the research article "Vibration energy harvesting based monitoring of an operational bridge undergoing forced vibration and train passage" Cahill et al. (2018) [1]. The article provides data on the full-scale bridge testing using piezoelectric vibration energy harvesters on Pershagen Bridge, Sweden. The bridge is actively excited via a swept sinusoidal input. During the testing, the bridge remains operational and train passages continue. The test recordings include the voltage responses obtained from the vibration energy harvesters during these tests and train passages. The original dataset is made available to encourage the use of energy harvesting for Structural Health Monitoring.

Vibration testing of the JE-M-604-4-IUE rocket motor (Thiokol P/N E 28639-03)

NASA Technical Reports Server (NTRS)

Alt, R. E.; Tosh, J. T.

1976-01-01

The NASA International Ultraviolet Explorer (IUE) rocket motor (TE-M-604-4), a solid fuel, spherical rocket motor, was vibration tested in the Impact, Vibration, and Acceleration (IVA) Test Unit of the von Karman Gas Dynamics Facility (VKF). The objective of the test program was to subject the motor to qualification levels of sinusoidal and random vibration prior to the altitude firing of the motor in the Propulsion Development Test Cell (T-3), Engine Test Facility (ETF), AEDC. The vibration testing consisted of a low level sine survey from 5 to 2,000 Hz, followed by a qualification level sine sweep and qualification level random vibration. A second low level sine survey followed the qualification level testing. This sequence of testing was accomplished in each of three orthogonal axes. No motor problems were observed due to the imposition of these dynamic environments.

77 FR 58301 - Technical Amendment; Airworthiness Standards: Aircraft Engines; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-20

... technical amendment, the FAA clarified aircraft engine vibration test requirements in the airworthiness... amendment, the FAA intended to clarify vibration test requirements in Sec. 33.83 of 14 Code of Federal... read as follows: Sec. 33.83 Vibration test. (a) Each engine must undergo vibration surveys to establish...

Seminar on Understanding Digital Control and Analysis in Vibration Test Systems

NASA Technical Reports Server (NTRS)

1975-01-01

The advantages of the digital methods over the analog vibration methods are demonstrated. The following topics are covered: (1) methods of computer-controlled random vibration and reverberation acoustic testing, (2) methods of computer-controlled sinewave vibration testing, and (3) methods of computer-controlled shock testing. General algorithms are described in the form of block diagrams and flow diagrams.

1. Credit PSR. This view displays the north and west ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Credit PSR. This view displays the north and west facades of Test Stand "G" (Vibration Facility) as seen when looking east southeast (110°). Test Stand "G" no longer houses the vibrator; it now houses an autoclave due to the changing nature of the testing work. The Vibration Facility was Test Stand "G"'s historic function. Test Stand "E" is at the far right. The Vibration Facility subjected motor and engine assemblies to various vibration patterns in order to simulate flight conditions and evaluate the durability of engine and motor designs. - Jet Propulsion Laboratory Edwards Facility, Test Stand G, Edwards Air Force Base, Boron, Kern County, CA

Investigation of Concrete Floor Vibration Using Heel-Drop Test

NASA Astrophysics Data System (ADS)

Azaman, N. A. Mohd; Ghafar, N. H. Abd; Azhar, A. F.; Fauzi, A. A.; Ismail, H. A.; Syed Idrus, S. S.; Mokhjar, S. S.; Hamid, F. F. Abd

2018-04-01

In recent years, there is an increased in floor vibration problems of structures like residential and commercial building. Vibration is defined as a serviceability issue related to the comfort of the occupant or damage equipment. Human activities are the main source of vibration in the building and it could affect the human comfort and annoyance of residents in the building when the vibration exceed the recommend level. A new building, Madrasah Tahfiz located at Yong Peng have vibration problem when load subjected on the first floor of the building. However, the limitation of vibration occurs on building is unknown. Therefore, testing is needed to determine the vibration behaviour (frequency, damping ratio and mode shape) of the building. Heel-drop with pace 2Hz was used in field measurement to obtain the vibration response. Since, the heel-drop test results would vary in light of person performance, test are carried out three time to reduce uncertainty. Natural frequency from Frequency Response Function analysis (FRF) is 17.4Hz, 16.8, 17.4Hz respectively for each test.

In-Flight Vibration Environment of the NASA F-15B Flight Test Fixture

NASA Technical Reports Server (NTRS)

Corda, Stephen; Franz, Russell J.; Blanton, James N.; Vachon, M. Jake; DeBoer, James B.

2002-01-01

Flight vibration data are analyzed for the NASA F-15B/Flight Test Fixture II test bed. Understanding the in-flight vibration environment benefits design and integration of experiments on the test bed. The power spectral density (PSD) of accelerometer flight data is analyzed to quantify the in-flight vibration environment from a frequency of 15 Hz to 1325 Hz. These accelerometer data are analyzed for typical flight conditions and maneuvers. The vibration data are compared to flight-qualification random vibration test standards. The PSD levels in the lateral axis generally are greater than in the longitudinal and vertical axes and decrease with increasing frequency. At frequencies less than approximately 40 Hz, the highest PSD levels occur during takeoff and landing. Peaks in the PSD data for the test fixture occur at approximately 65, 85, 105-110, 200, 500, and 1000 Hz. The pitch-pulse and 2-g turn maneuvers produce PSD peaks at 115 Hz. For cruise conditions, the PSD level of the 85-Hz peak is greatest for transonic flight at Mach 0.9. From 400 Hz to 1325 Hz, the takeoff phase has the highest random vibration levels. The flight-measured vibration levels generally are substantially lower than the random vibration test curve.

Differential effect of muscle vibration on intracortical inhibitory circuits in humans

PubMed Central

Rosenkranz, Karin; Rothwell, John C

2003-01-01

Low amplitude muscle vibration (0.5 ms; 80 Hz; duration 1.5 s) was applied in turn to each of three different intrinsic hand muscles (first dorsal interosseus, FDI; abductor pollicis brevis, APB; and abductor digiti minimi, ADM) in order to test its effect on the EMG responses evoked by transcranial magnetic stimulation (TMS). Recordings were also taken from flexor and extensor carpi radialis (FCR and ECR, respectively). We evaluated the amplitude of motor evoked potentials (MEPs) produced by a single TMS pulse, short interval intracortical inhibition and facilitation (SICI and ICF) and long interval intracortical inhibition (LICI). TMS pulses were applied 1 s after the start of vibration with subjects relaxed throughout. Vibration increased the amplitude of MEPs evoked in the vibrated muscle (162 ± 6 % of MEP with no vibration; mean ± s.e.m.), but suppressed MEPs in the two non-vibrated hand muscles (72 ± 9 %). Compared with no vibration (test response reduced to 51 ± 5 % of control), there was less SICI in the vibrated muscle (test response reduced to 92 ± 28 % of control) and more in the non-vibrated hand muscles (test response reduced to 27 ± 5 % of control). The opposite occurred for LICI: compared with the no vibration condition (test response reduced to 33 ± 6 % control), there was more LICI in the vibrated muscle (test response reduced to 17 ± 3 % control) than in the non-vibrated hand muscles (test response reduced to 80 ± 11 % control) even when the intensity of the test stimulus was adjusted to compensate for the changes in baseline MEP. There was no effect on ICF. Cutaneous stimulation of the index finger (80 Hz, 1.5 s duration, twice sensory threshold) had no consistent differential effect on any of the parameters. We conclude that vibratory input from muscle can differentially modulate excitability in motor cortical circuits. PMID:12821723

Multiple direction vibration fixture

DOEpatents

Cericola, Fred; Doggett, James W.; Ernest, Terry L.; Priddy, Tommy G.

1991-01-01

An apparatus for simulating a rocket launch environment on a test item undergoing centrifuge testing by subjecting the item simultaneously or separately to vibration along an axis of centripetal force and along an axis perpendicular to the centripetal force axis. The apparatus includes a shaker motor supported by centrifuge arms and a right angle fixture pivotally connected to one of the shaker motor mounts. When the shaker motor vibrates along the centripetal force axis, the vibrations are imparted to a first side of the right angle fixture. The vibrations are transmitted 90 degrees around the pivot and are directed to a second side of the right angle fixture which imparts vibrations perpendicular to the centripetal force axis. The test item is in contact with a third side of the right angle fixture and receives both centripetal-force-axis vibrations and perpendicular axis vibrations simultaneously. A test item can be attached to the third side near the flexible coupling or near the air bag to obtain vibrations along the centripetal force axis or transverse to the centripetal force axis.

Vibration sensibility testing in the workplace. Day-to-day reliability.

PubMed

Rosecrance, J C; Cook, T M; Satre, D L; Goode, J D; Schroder, M J

1994-09-01

Loss of vibration sensibility has been suggested as an early indicator of peripheral compression neuropathy, including carpal tunnel syndrome. Although vibration sensibility has been used frequently to evaluate carpal tunnel syndrome, the day-to-day reliability of vibration measurements in an industrial population measured at the workplace has not been assessed. Vibration sensibility testing was performed at the university ergonomics laboratory on 50 volunteers (100 hands) and at a newspaper company on 50 workers (100 hands). Vibration perception and disappearance thresholds were measured on two occasions separated by 3 to 5 days. Student's t tests indicated no significant differences between the first and second tests or between the two groups. Pearson product-moment correlations for test-retest reliability were lower in the industry group but were relatively high despite the less than optimal testing conditions. Our findings suggest that vibration sensibility measurements are reliable from day to day not only in the laboratory but also in the workplace.

14 CFR 33.43 - Vibration test.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each... configuration of the propeller type which is used for the endurance test, and using, for other engines, the same...

14 CFR 33.83 - Vibration test.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine... experience, analysis, and component test and shall address, as a minimum, blades, vanes, rotor discs, spacers...

14 CFR 33.83 - Vibration test.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine... experience, analysis, and component test and shall address, as a minimum, blades, vanes, rotor discs, spacers...

14 CFR 33.43 - Vibration test.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each... configuration of the propeller type which is used for the endurance test, and using, for other engines, the same...

14 CFR 33.83 - Vibration test.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine... experience, analysis, and component test and shall address, as a minimum, blades, vanes, rotor discs, spacers...

14 CFR 33.43 - Vibration test.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each... configuration of the propeller type which is used for the endurance test, and using, for other engines, the same...

Research on simultaneous impact of hand-arm and whole-body vibration.

PubMed

Kowalski, Piotr; Zając, Jacek

2012-01-01

This article presents the results of laboratory tests on the combined effect of whole-body vibration (WBV) and hand-arm vibration (HAV). The reactions of subjects exposed to various combinations of vibration were recorded. The vibrotactile perception threshold (VPT) test identified changes caused by exposure to vibration. Ten male subjects met the criteria of the study. There were 4 series of tests: a reference test and tests after exposure to HAV, WBV, and after simultaneous exposure to HAV and WBV. An analysis of the results (6000 ascending and descending VPTs) showed that the changes in VPTs were greatest after simultaneous exposure to both kinds of vibration. The increase in VPT, for all stimulus frequencies, was then higher than after exposure to HAV or WBV only.

Effects of vibration and shock on the performance of gas-bearing space-power Brayton cycle turbomachinery. Part 4: Suppression of rotor-bearing system vibrations through flexible bearing support damping

NASA Technical Reports Server (NTRS)

Tessarzik, J. M.; Chiang, T.; Badgley, R. H.

1974-01-01

A bearing damper, operating on the support flexure of a pivoted pad in a tilting-pad type gas-lubricated journal bearing, has been designed, built, and tested under externally-applied random vibrations. The NASA Brayton Rotating Unit (BRU), a 36,000 rpm, 10-Kwe turbogenerator had previously been subjected in the MTI Vibration Test Laboratory to external random vibrations, and vibration response data had been recorded and analyzed for amplitude distribution and frequency content at a number of locations in the machine. Based on data from that evaluation, a piston-type damper was designed and developed for each of the two flexibly-supported journal bearing pads (one in each of the two three-pad bearings). A modified BRU, with dampers installed, has been re-tested under random vibration conditions. Root-mean-square vibration amplitudes were determined from the test data, and displacement power spectral density analyses have been performed. Results of these data reduction efforts have been compared with vibration tolerance limits. Results of the tests indicate significant reductions in vibration levels in the bearing gas-lubricant films, particularly in the rigidly-mounted pads. The utility of the gas-lubricated damper for limiting rotor-bearing system vibrations in high-speed turbomachinery has thus been demonstrated.

Vibration Testing of an Operating Stirling Convertor

NASA Technical Reports Server (NTRS)

Hughes, William O.; McNelis, Mark E.; Goodnight, Thomas W.

2000-01-01

The NASA John H. Glenn Research Center and the U.S. Department of Energy are currently developing a Stirling convertor for use as an advanced spacecraft power system for future NASA deep-space missions. As part of this development, a Stirling Technology Demonstrator Convertor (TDC) was recently tested to verify its survivability and capability of withstanding its expected launch random vibration environment. The TDC was fully operational (producing power) during the random vibration testing. The output power of the convertor was measured during the testing, and these results are discussed in this paper. Numerous accelerometers and force gauges were also present which provided information on the dynamic characteristics of the TDC and an indication of any possible damage due to vibration. These measurements will also be discussed in this paper. The vibration testing of the Stirling TDC was extremely successful. The TDC survived all its vibration testing with no structural damage or functional performance degradation. As a result of this testing, the Stirling convertor's capability to withstand vibration has been demonstrated, enabling its usage in future spacecraft power systems.

Force Limited Vibration Testing

NASA Technical Reports Server (NTRS)

Scharton, Terry; Chang, Kurng Y.

2005-01-01

This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test data. A simple two degree of freedom system is shown and the governing equations for basic force limiting results for this system are reviewed. The design and results of the shuttle vibration forces (SVF) experiments are reviewed. The Advanced Composition Explorer (ACE) also was used to validate force limiting. Test instrumentation and supporting equipment are reviewed including piezo-electric force transducers, signal processing and conditioning systems, test fixtures, and vibration controller systems. Several examples of force limited vibration testing are presented with some results.

14 CFR 33.83 - Vibration test.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Vibration test. 33.83 Section 33.83 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine...

33 CFR 159.103 - Vibration test.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Vibration test. 159.103 Section 159.103 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.103 Vibration test. The device...

A new compound control method for sine-on-random mixed vibration test

NASA Astrophysics Data System (ADS)

Zhang, Buyun; Wang, Ruochen; Zeng, Falin

2017-09-01

Vibration environmental test (VET) is one of the important and effective methods to provide supports for the strength design, reliability and durability test of mechanical products. A new separation control strategy was proposed to apply in multiple-input multiple-output (MIMO) sine on random (SOR) mixed mode vibration test, which is the advanced and intensive test type of VET. As the key problem of the strategy, correlation integral method was applied to separate the mixed signals which included random and sinusoidal components. The feedback control formula of MIMO linear random vibration system was systematically deduced in frequency domain, and Jacobi control algorithm was proposed in view of the elements, such as self-spectrum, coherence, and phase of power spectral density (PSD) matrix. Based on the excessive correction of excitation in sine vibration test, compression factor was introduced to reduce the excitation correction, avoiding the destruction to vibration table or other devices. The two methods were synthesized to be applied in MIMO SOR vibration test system. In the final, verification test system with the vibration of a cantilever beam as the control object was established to verify the reliability and effectiveness of the methods proposed in the paper. The test results show that the exceeding values can be controlled in the tolerance range of references accurately, and the method can supply theory and application supports for mechanical engineering.

Portable Life Support Stretcher Unit (PLSSU) Environmental Tests: Preproduction Model.

DTIC Science & Technology

1982-06-01

fixture was taken out by fluttering of the castering wheels since the securing straps were too soft to transmit the motion. At higher frequencies, it was...5 3.3 Proof Tests . . . 6 3.4 Vibration Tests . . . 9 3.4.1 General . . . 9 3.4.2 Pretest Inspection . . . 12 3.4.3 Vertical Vibration on Wheels ...14 3.4.4 Horizontal Vibration on Wheels . . . 15 3.4.5 Horizontal Vibration with Handle Suspension . . . 16 3.4.6 Vertical Vibration with Handle

Vibration and acoustic testing of TOPEX/Poseidon satellite

NASA Technical Reports Server (NTRS)

Boatman, Dave; Scharton, Terry; Hershfeld, Donald; Larkin, Paul

1992-01-01

The satellite was subjected to a 1.5G swept sine vibration test and a 146 dB overall level acoustic test, in accordance with Ariane launch vehicle requirements, at the NASA Goddard Space Flight Center. Extensive pretest analysis of the sine test was conducted to plan the input notching and to justify vibration testing the satellite only in the longitudinal axis. A unique measurement system was utilized to determine the six components of interface force between the shaker and the satellite in the sine vibration test. The satellite was heavily instrumented in both the sine vibration and acoustic test in order to insure that the launch loads were enveloped with appropriate margin and that satellite responses did not exceed the compatibilities of the structure and equipment. The test specification, objectives, instrumentation, and test results are described herein.

Force Limited Vibration Testing Monograph

NASA Technical Reports Server (NTRS)

Scharton, Terry D.

1997-01-01

The practice of limiting the shaker force in vibration tests was investigated at the NASA Jet Propulsion Laboratory (JPL) in 1990 after the mechanical failure of an aerospace component during a vibration test. Now force limiting is used in almost every major vibration test at JPL and in many vibration tests at NASA Goddard Space Flight Center (GSFC) and at many aerospace contractors. The basic ideas behind force limiting have been in the literature for several decades, but the piezo-electric force transducers necessary to conveniently implement force limiting have been available only in the last decade. In 1993, funding was obtained from the NASA headquarters Office of Chief Engineer to develop and document the technology needed to establish force limited vibration testing as a standard approach available to all NASA centers and aerospace contractors. This monograph is the final report on that effort and discusses the history, theory, and applications of the method in some detail.

Measurement of Dynamic Viscoelasticity of Full-Size Wood Composite Panels Using a Vibration Testing Method

Treesearch

Cheng Guan; Houjiang Zhang; John F. Hunt; Lujing Zhou; Dan Feng

2016-01-01

The dynamic viscoelasticity of full-size wood composite panels (WCPs) under the free-free vibrational state were determined by a vibration testing method. Vibration detection tests were performed on 194 pieces of three types of full-size WCPs (particleboard, medium density fiberboard, and plywood (PW)). The dynamic viscoelasticity from smaller specimens cut from the...

Modeling of UH-60A Hub Accelerations with Neural Networks

NASA Technical Reports Server (NTRS)

Kottapalli, Sesi

2002-01-01

Neural network relationships between the full-scale, flight test hub accelerations and the corresponding three N/rev pilot floor vibration components (vertical, lateral, and longitudinal) are studied. The present quantitative effort on the UH-60A Black Hawk hub accelerations considers the lateral and longitudinal vibrations. An earlier study had considered the vertical vibration. The NASA/Army UH-60A Airloads Program flight test database is used. A physics based "maneuver-effect-factor (MEF)", derived using the roll-angle and the pitch-rate, is used. Fundamentally, the lateral vibration data show high vibration levels (up to 0.3 g's) at low airspeeds (for example, during landing flares) and at high airspeeds (for example, during turns). The results show that the advance ratio and the gross weight together can predict the vertical and the longitudinal vibration. However, the advance ratio and the gross weight together cannot predict the lateral vibration. The hub accelerations and the advance ratio can be used to satisfactorily predict the vertical, lateral, and longitudinal vibration. The present study shows that neural network based representations of all three UH-60A pilot floor vibration components (vertical, lateral, and longitudinal) can be obtained using the hub accelerations along with the gross weight and the advance ratio. The hub accelerations are clearly a factor in determining the pilot vibration. The present conclusions potentially allow for the identification of neural network relationships between the experimental hub accelerations obtained from wind tunnel testing and the experimental pilot vibration data obtained from flight testing. A successful establishment of the above neural network based link between the wind tunnel hub accelerations and the flight test vibration data can increase the value of wind tunnel testing.

Characterization of Friction Joints Subjected to High Levels of Random Vibration

NASA Technical Reports Server (NTRS)

deSantos, Omar; MacNeal, Paul

2012-01-01

This paper describes the test program in detail including test sample description, test procedures, and vibration test results of multiple test samples. The material pairs used in the experiment were Aluminum-Aluminum, Aluminum- Dicronite coated Aluminum, and Aluminum-Plasmadize coated Aluminum. Levels of vibration for each set of twelve samples of each material pairing were gradually increased until all samples experienced substantial displacement. Data was collected on 1) acceleration in all three axes, 2) relative static displacement between vibration runs utilizing photogrammetry techniques, and 3) surface galling and contaminant generation. This data was used to estimate the values of static friction during random vibratory motion when "stick-slip" occurs and compare these to static friction coefficients measured before and after vibration testing.

CM-2 Environmental / Modal Testing of Spacehab Racks

NASA Technical Reports Server (NTRS)

McNelis, Mark E.; Goodnight, Thomas W.; Farkas, Michael A.

2001-01-01

Combined environmental/modal vibration testing has been implemented at the NASA Glenn Research Center's Structural Dynamics Laboratory. The benefits of combined vibration testing are that it facilitates test article modal characterization and vibration qualification testing. The Combustion Module-2 (CM-2) is a space experiment that launches on Shuttle mission STS 107 in the SPACEHAB Research Double Module. The CM-2 flight hardware is integrated into a SPACEHAB single and double rack. CM-2 rack level combined vibration testing was recently completed on a shaker table to characterize the structure's modal response and verify the random vibration response. Control accelerometers and limit force gauges, located between the fixture and rack interface, were used to verify the input excitation. Results of the testing were used to verify the loads and environments for flight on the Shuttle.

Vibration Sensitivity of a Wide-Temperature Electronically Scanned Pressure Measurement (ESP) Module

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Garza, Frederico R.

2001-01-01

A vibration sensitivity test was conducted on a Wide-Temperature ESP module. The test object was Module "M4," a 16-channel, 4 psi unit scheduled for installation in the Arc Sector of NTF. The module was installed on a vibration exciter and loaded to positive then negative full-scale pressures (+/-2.5 psid). Test variables were the following: Vibration frequencies: 20, 55, 75 Hz. Vibration level: 1 g. Vibration axes: X, Y, Z. The pressure response was measured on each channel, first without and then with the vibration turned on, and the difference analyzed by means of the statistical t-test. The results show that the vibration sensitivity does not exceed 0.01% Full Scale Output per g (with the exception of one channel on one axis) to a 95 percent confidence level. This specification, limited by the resolution of the pressure source, lies well below the total uncertainty specification of 0.1 percent Full Scale Output.

Field Test Data for Detecting Vibrations of a Building Using High-Speed Video Cameras

DTIC Science & Technology

2017-10-01

ARL-TR-8185 ● OCT 2017 US Army Research Laboratory Field Test Data for Detecting Vibrations of a Building Using High -Speed Video...Field Test Data for Detecting Vibrations of a Building Using High -Speed Video Cameras by Caitlin P Conn and Geoffrey H Goldman Sensors and...June 2016 – October 2017 4. TITLE AND SUBTITLE Field Test Data for Detecting Vibrations of a Building Using High -Speed Video Cameras 5a. CONTRACT

49 CFR 178.608 - Vibration standard.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Vibration standard. 178.608 Section 178.608... Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section. (b) Test method. (1...

49 CFR 178.608 - Vibration standard.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration standard. 178.608 Section 178.608... Testing of Non-bulk Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section...

49 CFR 178.608 - Vibration standard.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Vibration standard. 178.608 Section 178.608... Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section. (b) Test method. (1...

49 CFR 178.608 - Vibration standard.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Vibration standard. 178.608 Section 178.608... Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section. (b) Test method. (1...

49 CFR 178.608 - Vibration standard.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Vibration standard. 178.608 Section 178.608... Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section. (b) Test method. (1...

Summary of the modeling and test correlations of a NASTRAN finite element vibrations model for the AH-1G helicopter, task 1

NASA Technical Reports Server (NTRS)

Cronkhite, J. D.; Berry, V. L.; Dompka, R. V.

1987-01-01

The AH-1G NASTRAN finite element model (FEM) is described and the correlations with measured data that were conducted to verify the model are summarized. Comparisons of the AH-1G NASTRAN FEM calculations with measured data include the following: (1) fuselage and tailboom static load deflection (stiffness) testing, (2) airframe ground vibration testing (0-30 H<), (3) airframe flight vibration testing (main rotor, 2,4, and 6/rev), and (4) tailboom effective skin static testing. A description of the modeling rationale and techniques used to develop the NASTRAN FEM is presented in conjunction with all previous correlation work. In general, the correlations show good agreement between analysis and test in stiffness and vibration response through 15 to 20 Hz. For higher frequencies (equal to or greater than 4/rev (21.6 Hz)), the vibration responses generally did not agree well. Also, the lateral (2/rev (10.8 Hz)) flight vibration responses were much lower in the FEM than test, indicating that there is a significant excitation source other than at the main rotor hub that is affecting the lateral vibrations, such as downwash impingement on the vertical tail.

Particle damping applied research on mining dump truck vibration control

NASA Astrophysics Data System (ADS)

Song, Liming; Xiao, Wangqiang; Guo, Haiquan; Yang, Zhe; Li, Zeguang

2018-05-01

Vehicle vibration characteristics has become an important evaluation indexes of mining dump truck. In this paper, based on particle damping technology, mining dump truck vibration control was studied by combining the theoretical simulation with actual testing, particle damping technology was successfully used in mining dump truck cab vibration control. Through testing results analysis, with a particle damper, cab vibration was reduced obviously, the methods and basis were provided for vehicle vibration control research and particle damping technology application.

CM-2 Environmental/Modal Testing of SPACEHAB Racks

NASA Technical Reports Server (NTRS)

McNelis, Mark E.; Goodnight, Thomas W.

2001-01-01

Combined environmental/modal vibration testing has been implemented at the NASA Glenn Research Center's Structural Dynamics Laboratory. The benefits of combined vibration testing are that it facilitates test article modal characterization and vibration qualification testing. The Combustion Module-2 (CM-2) is a space experiment that will launch on shuttle mission STS-107 in the SPACEHAB Research Double Module. The CM-2 flight hardware is integrated into a SPACEHAB single and double rack. CM-2 rack-level combined vibration testing was recently completed on a shaker table to characterize the structure's modal response and verify the random vibration response. Control accelerometers and limit force gauges, located between the fixture and rack interface, were used to verify the input excitation. Results of the testing were used to verify the loads and environments for flight on the shuttles.

The History of a Decision: A Standard Vibration Test Method for Qualification

DOE PAGES

Rizzo, Davinia; Blackburn, Mark

2017-01-01

As Mil-Std-810G and subsequent versions have included multiple degree of freedom vibration test methodologies, it is important to understand the history and factors that drove the original decision in Mil-Std-810 to focus on single degree of freedom (SDOF) vibration testing. By assessing the factors and thought process of early Mil-Std-810 vibration test methods, it enables one to better consider the use of multiple degree of freedom testing now that it is feasible with today’s technology and documented in Mil-Std-810. This paper delves into the details of the decision made in the 1960s for the SDOF vibration testing standards in Mil-Std-810more » beyond the limitations of technology at the time. We also consider the implications for effective test planning today considering the advances in test capabilities and improvements in understanding of the operational environment.« less

The History of a Decision: A Standard Vibration Test Method for Qualification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rizzo, Davinia; Blackburn, Mark

As Mil-Std-810G and subsequent versions have included multiple degree of freedom vibration test methodologies, it is important to understand the history and factors that drove the original decision in Mil-Std-810 to focus on single degree of freedom (SDOF) vibration testing. By assessing the factors and thought process of early Mil-Std-810 vibration test methods, it enables one to better consider the use of multiple degree of freedom testing now that it is feasible with today’s technology and documented in Mil-Std-810. This paper delves into the details of the decision made in the 1960s for the SDOF vibration testing standards in Mil-Std-810more » beyond the limitations of technology at the time. We also consider the implications for effective test planning today considering the advances in test capabilities and improvements in understanding of the operational environment.« less

Research on Vibration Test in Urban Indoor Substation

NASA Astrophysics Data System (ADS)

Ma, Yuchao; Mo, Juan; Xu, Jin; Fan, Baozhen

2018-01-01

The problem of vibration and noise of urban indoor substations has becoming more and more socially concerned.The urban indoor substation of 110kV and its conjoined buildings were taken as the research object and the vibration tests of the transformer and each floor slab were respectively carried out.The sound vibration characteristics and sound transmission rules of the urban indoor substation were obtained through the time-frequency analysis and coherence analysis of the test data. The vibration spectrum of transformer body was mainly 100Hz together with its multiplying factors and the vibration characteristics of the floor slab were basically the same as those of the transformer body. it is crucial to control the vibration and noise transmission in the equipment floor of the urban indoor substation.

46 CFR 162.050-37 - Vibration test.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 6 2010-10-01 2010-10-01 false Vibration test. 162.050-37 Section 162.050-37 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Pollution Prevention Equipment § 162.050-37 Vibration test. (a...

Performance Characterization and Vibration Testing of 30-cm Carbon-Carbon Ion Optics

NASA Technical Reports Server (NTRS)

Steven Snyder, John; Brophy, John R.

2004-01-01

Carbon-based ion optics have the potential to significantly increase the operable life and power ranges of ion thrusters because of reduced erosion rates compared to molybdenum optics. The development of 15-cm and larger diameter grids has encountered many problems, however, not the least of which is the ability to pass vibration testing. JPL has recently developed a new generation of 30-cm carbon-carbon ion optics in order to address these problems and demonstrate the viability of the technology. Perveance, electron backstreaming, and screen grid transparency data are presented for two sets of optics. Vibration testing was successfully performed on two different sets of ion optics with no damage and the results of those tests are compared to models of grid vibrational behavior. It will be shown that the vibration model is a conservative predictor of grid response and can accurately describe test results. There was no change in grid alignment as a result of vibration testing and a slight improvement, if any change at all, in optics performance.

A New Large Vibration Test Facility Concept for the James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Ross, Brian P.; Johnson, Eric L.; Hoksbergen, Joel; Lund, Doug

2014-01-01

The James Webb Space Telescope consists of three main components, the Integrated Science Instrument Module (ISIM) Element, the Optical Telescope Element (OTE), and the Spacecraft Element. The ISIM and OTE are being assembled at the National Aeronautics and Space Administration's Goddard Spaceflight Center (GSFC). The combined OTE and ISIM Elements, called OTIS, will undergo sine vibration testing before leaving Goddard. OTIS is the largest payload ever tested at Goddard and the existing GSFC vibration facilities are incapable of performing a sine vibration test of the OTIS payload. As a result, a new large vibration test facility is being designed. The new facility will consist of a vertical system with a guided head expander and a horizontal system with a hydrostatic slip table. The project is currently in the final design phase with installation to begin in early 2015 and the facility is expected to be operational by late 2015. This paper will describe the unique requirements for a new large vibration test facility and present the selected final design concepts.

Incorporating Vibration Test Results for the Advanced Stirling Convertor into the System Dynamic Model

NASA Technical Reports Server (NTRS)

Meer, David W.; Lewandowski, Edward J.

2010-01-01

The U.S. Department of Energy (DOE), Lockheed Martin Corporation (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Convertors (ASC) at NASA GRC undergo a vibration test sequence intended to simulate the vibration history that an ASC would experience when used in an ASRG for a space mission. During these tests, a data system collects several performance-related parameters from the convertor under test for health monitoring and analysis. Recently, an additional sensor recorded the slip table position during vibration testing to qualification level. The System Dynamic Model (SDM) integrates Stirling cycle thermodynamics, heat flow, mechanical mass, spring, damper systems, and electrical characteristics of the linear alternator and controller. This Paper presents a comparison of the performance of the ASC when exposed to vibration to that predicted by the SDM when exposed to the same vibration.

Neural Network Modeling of UH-60A Pilot Vibration

NASA Technical Reports Server (NTRS)

Kottapalli, Sesi

2003-01-01

Full-scale flight-test pilot floor vibration is modeled using neural networks and full-scale wind tunnel test data for low speed level flight conditions. Neural network connections between the wind tunnel test data and the tlxee flight test pilot vibration components (vertical, lateral, and longitudinal) are studied. Two full-scale UH-60A Black Hawk databases are used. The first database is the NASMArmy UH-60A Airloads Program flight test database. The second database is the UH-60A rotor-only wind tunnel database that was acquired in the NASA Ames SO- by 120- Foot Wind Tunnel with the Large Rotor Test Apparatus (LRTA). Using neural networks, the flight-test pilot vibration is modeled using the wind tunnel rotating system hub accelerations, and separately, using the hub loads. The results show that the wind tunnel rotating system hub accelerations and the operating parameters can represent the flight test pilot vibration. The six components of the wind tunnel N/rev balance-system hub loads and the operating parameters can also represent the flight test pilot vibration. The present neural network connections can significandy increase the value of wind tunnel testing.

Ground Vibration Testing Options for Space Launch Vehicles

NASA Technical Reports Server (NTRS)

Patterson, Alan; Smith, Robert K.; Goggin, David; Newsom, Jerry

2011-01-01

New NASA launch vehicles will require development of robust systems in a fiscally-constrained environment. NASA, Department of Defense (DoD), and commercial space companies routinely conduct ground vibration tests as an essential part of math model validation and launch vehicle certification. Although ground vibration testing must be a part of the integrated test planning process, more affordable approaches must also be considered. A study evaluated several ground vibration test options for the NASA Constellation Program flight test vehicles, Orion-1 and Orion-2, which concluded that more affordable ground vibration test options are available. The motivation for ground vibration testing is supported by historical examples from NASA and DoD. The approach used in the present study employed surveys of ground vibration test subject-matter experts that provided data to qualitatively rank six test options. Twenty-five experts from NASA, DoD, and industry provided scoring and comments for this study. The current study determined that both element-level modal tests and integrated vehicle modal tests have technical merits. Both have been successful in validating structural dynamic math models of launch vehicles. However, element-level testing has less overall cost and schedule risk as compared to integrated vehicle testing. Future NASA launch vehicle development programs should anticipate that some structural dynamics testing will be necessary. Analysis alone will be inadequate to certify a crew-capable launch vehicle. At a minimum, component and element structural dynamic tests are recommended for new vehicle elements. Three viable structural dynamic test options were identified. Modal testing of the new vehicle elements and an integrated vehicle test on the mobile launcher provided the optimal trade between technical, cost, and schedule.

Coupled rotor/fuselage dynamic analysis of the AH-1G helicopter and correlation with flight vibrations data

NASA Technical Reports Server (NTRS)

Corrigan, J. C.; Cronkhite, J. D.; Dompka, R. V.; Perry, K. S.; Rogers, J. P.; Sadler, S. G.

1989-01-01

Under a research program designated Design Analysis Methods for VIBrationS (DAMVIBS), existing analytical methods are used for calculating coupled rotor-fuselage vibrations of the AH-1G helicopter for correlation with flight test data from an AH-1G Operational Load Survey (OLS) test program. The analytical representation of the fuselage structure is based on a NASTRAN finite element model (FEM), which has been developed, extensively documented, and correlated with ground vibration test. One procedure that was used for predicting coupled rotor-fuselage vibrations using the advanced Rotorcraft Flight Simulation Program C81 and NASTRAN is summarized. Detailed descriptions of the analytical formulation of rotor dynamics equations, fuselage dynamic equations, coupling between the rotor and fuselage, and solutions to the total system of equations in C81 are included. Analytical predictions of hub shears for main rotor harmonics 2p, 4p, and 6p generated by C81 are used in conjunction with 2p OLS measured control loads and a 2p lateral tail rotor gearbox force, representing downwash impingement on the vertical fin, to excite the NASTRAN model. NASTRAN is then used to correlate with measured OLS flight test vibrations. Blade load comparisons predicted by C81 showed good agreement. In general, the fuselage vibration correlations show good agreement between anslysis and test in vibration response through 15 to 20 Hz.

Method and apparatus for determining material structural integrity

DOEpatents

Pechersky, Martin

1996-01-01

A non-destructive method and apparatus for determining the structural integrity of materials by combining laser vibrometry with damping analysis techniques to determine the damping loss factor of a material. The method comprises the steps of vibrating the area being tested over a known frequency range and measuring vibrational force and velocity as a function of time over the known frequency range. Vibrational velocity is preferably measured by a laser vibrometer. Measurement of the vibrational force depends on the vibration method. If an electromagnetic coil is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by the amount of coil current used in vibrating the magnet. If a reciprocating transducer is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by a force gauge in the reciprocating transducer. Using known vibrational analysis methods, a plot of the drive point mobility of the material over the preselected frequency range is generated from the vibrational force and velocity measurements. The damping loss factor is derived from a plot of the drive point mobility over the preselected frequency range using the resonance dwell method and compared with a reference damping loss factor for structural integrity evaluation.

Test-retest reliability of neurophysiological tests of hand-arm vibration syndrome in vibration exposed workers and unexposed referents.

PubMed

Gerhardsson, Lars; Gillström, Lennart; Hagberg, Mats

2014-01-01

Exposure to hand-held vibrating tools may cause the hand-arm vibration syndrome (HAVS). The aim was to study the test-retest reliability of hand and muscle strength tests, and tests for the determination of thermal and vibration perception thresholds, which are used when investigating signs of neuropathy in vibration exposed workers. In this study, 47 vibration exposed workers who had been investigated at the department of Occupational and Environmental Medicine in Gothenburg were compared with a randomized sample of 18 unexposed subjects from the general population of the city of Gothenburg. All participants passed a structured interview, answered several questionnaires and had a physical examination including hand and finger muscle strength tests, determination of vibrotactile (VPT) and thermal perception thresholds (TPT). Two weeks later, 23 workers and referents, selected in a randomized manner, were called back for the same test-procedures for the evaluation of test-retest reliability. The test-retest reliability after a two week interval expressed as limits of agreement (LOA; Bland-Altman), intra-class correlation coefficients (ICC) and Pearson correlation coefficients was excellent for tests with the Baseline hand grip, Pinch-grip and 3-Chuck grip among the exposed workers and referents (N = 23: percentage of differences within LOA 91 - 100%; ICC-values ≥0.93; Pearson r ≥0.93). The test-retest reliability was also excellent (percentage of differences within LOA 96-100 %) for the determination of vibration perception thresholds in digits 2 and 5 bilaterally as well as for temperature perception thresholds in digits 2 and 5, bilaterally (percentage of differences within LOA 91 - 96%). For ICC and Pearson r the results for vibration perception thresholds were good for digit 2, left hand and for digit 5, bilaterally (ICC ≥ 0.84; r ≥0.85), and lower (ICC = 0.59; r = 0.59) for digit 2, right hand. For the latter two indices the test-retest reliability for the determination of temperature thresholds was lower and showed more varying results. The strong test-retest reliability for hand and muscle strength tests as well as for the determination of VPTs makes these procedures useful for diagnostic purposes and follow-up studies in vibration exposed workers.

Experimental analysis of thread movement in bolted connections due to vibrations

NASA Technical Reports Server (NTRS)

Ramey, G. ED; Jenkins, Robert C.

1994-01-01

The objective of this study was to identify the main design parameters contributing to loosening of bolts due to vibration and to identify their relative importance and degree of contribution to bolt loosening. Vibration testing was conducted on a shaketable with a controlled-random input in the dynamic testing laboratory of the Structural Test Division of MSFC. Test specimens which contained one test bolt were vibrated for a fixed amount of time and percentage of pre-load loss was measured. Each specimen tested implemented some combination of eleven design parameters as dictated by the design of experiment methodology employed. The eleven design parameters were: bolt size (diameter), lubrication on bolt, hole tolerance, initial pre-load, nut locking device, grip length, thread pitch, lubrication between mating materials, class of fit, joint configuration and mass of configuration. These parameters were chosen for this experiment because they are believed to be the design parameters having the greatest impact on bolt loosening. Two values of each design parameter were used and each combination of parameters tested was subjected to two different directions of vibration and two different g-levels of vibration. One replication was made for each test to gain some indication of experimental error and repeatability and to give some degree of statistical credibility to the data, resulting in a total of 96 tests being performed. The results of the investigation indicated that nut locking devices, joint configuration, fastener size, and mass of configuration were significant in bolt loosening due to vibration. The results of this test can be utilized to further research the complex problem of bolt loosening due to vibration.

Random Vibrations

NASA Technical Reports Server (NTRS)

Messaro. Semma; Harrison, Phillip

2010-01-01

Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

Psycho-vibratory evaluation of timber floors - Towards the determination of design indicators of vibration acceptability and vibration annoyance

NASA Astrophysics Data System (ADS)

Negreira, J.; Trollé, A.; Jarnerö, K.; Sjökvist, L.-G.; Bard, D.

2015-03-01

In timber housing constructions, vibrations can be a nuisance for inhabitants. Notably, the vibrational response of wooden floor systems is an issue in need of being dealt with more adequately in the designing of such buildings. Studies addressing human response to vibrations are needed in order to be able to better estimate what level of vibrations in dwellings can be seen as acceptable. In the present study, measurements on five different wooden floors were performed in a laboratory environment at two locations in Sweden (SP in Växjö and LU in Lund). Acceleration measurements were carried out while a person either was walking on a particular floor or was seated in a chair placed there as the test leader was walking on the floor. These participants filled out a questionnaire regarding their perception and experiencing of the vibrations in question. Independently of the subjective tests, several static and dynamic characteristics of the floors were determined through measurements. The ultimate aim was to develop indicators of human response to floor vibrations, specifically those regarding vibration acceptability and vibration annoyance, their being drawn based on relationships between the questionnaire responses obtained and the parameter values determined on the basis of the measurements carried out. To that end, use was made of multilevel regression. Although the sample of floors tested was small, certain clear trends could be noted. The first eigenfrequency (calculated in accordance with Eurocode 5) and Hu and Chui's criterion (calculated from measured quantities) proved to be the best indicators of vibration annoyance, and the Maximum Transient Vibration Value (computed on the basis of the accelerations experienced by the test subjects) to be the best indicator of vibration acceptability.

An observational study of the effect of vibration on the caking of suspensions in oily vehicles.

PubMed

Jain, Rohit; Bork, Olaf; Alawi, Fadil; Nanjan, Karthigeyan; Tucker, Ian G

2016-11-30

An oily suspension of penethamate (PNT) that was physically stable on storage, caked solidly during road/air transport. This paper reports on the caking behaviour of PNT oily suspension formulations exposed to vibrations in a lab-based test designed to simulate road/air transport. The lab-test was used to study the effects of container type (glass v PET) and formulation (oil, surfactant type and concentration) on the physical stability of suspension under vibration. Redispersibility of the sediment was lower at longer vibrations times and at higher intensity of vibration. Caking on vibration was strongly influenced by the type of container (caking in glass but not in PET) possibly due to tribo-charging of particles. Caking on vibration was dependent on the formulation: type and concentration of surfactant; type of oil. The physical stability of oily suspensions, and the effect of vibration are two areas which have been largely neglected in the pharmaceutical literature. This paper discusses some potential mechanisms for the observations but studies using fully characterised materials are required. Finally we conclude that static testing of physical stability of oily suspensions is not sufficient and that a vibrational stress test is required. Copyright © 2016 Elsevier B.V. All rights reserved.

Force Limited Vibration Test of HESSI Imager

NASA Technical Reports Server (NTRS)

Amato, Deborah; Pankow, David; Thomsen, Knud

2000-01-01

The High Energy Solar Spectroscopic Imager (HESSI) is a solar x-ray and gamma-ray observatory scheduled for launch in November 2000. Vibration testing of the HESSI imager flight unit was performed in August 1999. The HESSI imager consists of a composite metering tube, two aluminum trays mounted to the tube on titanium flexure mounts, and nine modulation grids mounted on each tray. The vibration tests were acceleration controlled and force limited, in order to prevent overtesting. The force limited strategy reduced the shaker force and notched the acceleration at resonances. The test set-up, test levels, and results are presented. The development of the force limits is also discussed. The imager successfully survived the vibration testing.

Gearbox vibration diagnostic analyzer

NASA Technical Reports Server (NTRS)

1992-01-01

This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.

An Examination of a Music Appreciation Method Incorporating Tactile Sensations from Artificial Vibrations

NASA Astrophysics Data System (ADS)

Ideguchi, Tsuyoshi; Yoshida, Ryujyu; Ooshima, Keita

We examined how test subject impressions of music changed when artificial vibrations were incorporated as constituent elements of a musical composition. In this study, test subjects listened to several music samples in which different types of artificial vibration had been incorporated and then subjectively evaluated any resulting changes to their impressions of the music. The following results were obtained: i) Even if rhythm vibration is added to a silent component of a musical composition, it can effectively enhance musical fitness. This could be readily accomplished when actual sounds that had been synchronized with the vibration components were provided beforehand. ii) The music could be listened to more comfortably by adding not only a natural vibration extracted from percussion instruments but also artificial vibration as tactile stimulation according to intentional timing. Furthermore, it was found that the test subjects' impression of the music was affected by a characteristic of the artificial vibration. iii) Adding vibration to high-frequency areas can offer an effective and practical way of enhancing the appeal of a musical composition. iv) The movement sensations of sound and vibration could be experienced when the strength of the sound and vibration are modified in turn. These results suggest that the intentional application of artificial vibration could result in a sensitivity amplification factor on the part of a listener.

Research Problems Associated with Limiting the Applied Force in Vibration Tests and Conducting Base-Drive Modal Vibration Tests

NASA Technical Reports Server (NTRS)

Scharton, Terry D.

1995-01-01

The intent of this paper is to make a case for developing and conducting vibration tests which are both realistic and practical (a question of tailoring versus standards). Tests are essential for finding things overlooked in the analyses. The best test is often the most realistic test which can be conducted within the cost and budget constraints. Some standards are essential, but the author believes more in the individual's ingenuity to solve a specific problem than in the application of standards which reduce problems (and technology) to their lowest common denominator. Force limited vibration tests and base-drive modal tests are two examples of realistic, but practical testing approaches. Since both of these approaches are relatively new, a number of interesting research problems exist, and these are emphasized herein.

Investigation of difficult component effects on finite element model vibration prediction for the Bell AH-1G helicopter. Volume 1: Ground vibration test results

NASA Technical Reports Server (NTRS)

Dompka, R. V.

1989-01-01

Under the NASA-sponsored Design Analysis Methods for VIBrationS (DAMVIBS) program, a series of ground vibration tests and NASTRAN finite element model (FEM) correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Previous correlations of the AH-1G showed good agreement between NASTRAN and tests through 15 to 20 Hz, but poor agreement in the higher frequency range of 20 to 30 Hz. Thus, this effort emphasized the higher frequency airframe vibration response correlations and identified areas that need further R and T work. To conduct the investigations, selected difficult components (main rotor pylon, secondary structure, nonstructural doors/panels, landing gear, engine, fuel, etc.) were systematically removed to quantify their effects on overall vibratory response of the airframe. The entire effort was planned and documented, and the results reviewed by NASA and industry experts in order to ensure scientific control of the testing, analysis, and correlation exercise. In particular, secondary structure and damping had significant effects on the frequency response of the airframe above 15 Hz. Also, the nonlinear effects of thrust stiffening and elastomer mounts were significant on the low frequency pylon modes below main rotor 1p (5.4 Hz). The results of the ground vibration testing are presented.

Concorde noise-induced building vibrations: John F. Kennedy International Airport

NASA Technical Reports Server (NTRS)

Mayes, W. H.; Stephens, D. G.; Deloach, R.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.; Miller, W. T.

1978-01-01

Outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded at eight homesites and a school along with the associated vibration levels in the walls, windows, and floors at these test sites. Limited subjective tests were conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise. Both vibration and rattle were detected subjectively in several houses for some operations of both the Concorde and subsonic aircraft. Seated subjects more readily detected floor vibrations than wall or window vibrations. Aircraft noise generally caused more window vibrations than common nonaircraft events such as walking and closing doors. Nonaircraft events and aircraft flyovers resulted in comparable wall vibration levels, while floor vibrations were generally greater for nonaircraft events than for aircraft flyovers. The relationship between structural vibration and aircraft noise is linear, with vibration levels being accurately predicted from overall sound pressure levels (OASPL) measured near the structure. Relatively high levels of structural vibration measured during Concorde operations are due more to higher OASPL levels than to unique Concorde-source characteristics.

49 CFR 178.803 - Testing and certification of IBCs.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Vibration 6 X 6 X 6 X 6 X 6 X 1.5 X Bottom lift 2 X X X X X Top lift 2 X 2 X 2 X 2 5 X Stacking 7 X 7 X 7 X... X Righting 2 5 X Tear 5 X 1 Flexible IBCs must be capable of withstanding the vibration test. 2 This... each test. 6 The vibration test may be performed in another order for IBCs manufactured and tested...

49 CFR 178.803 - Testing and certification of IBCs.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Vibration 6 X 6 X 6 X 6 X 6 X 1.5 X Bottom lift 2 X X X X X Top lift 2 X 2 X 2 X 2,5 X Stacking 7 X 7 X 7 X... X Righting 2,5 X Tear 5 X 1 Flexible IBCs must be capable of withstanding the vibration test. 2 This... each test. 6 The vibration test may be performed in another order for IBCs manufactured and tested...

49 CFR 178.803 - Testing and certification of IBCs.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Vibration 6 X 6 X 6 X 6 X 6 X 1.5 X Bottom lift 2 X X X X X Top lift 2 X 2 X 2 X 2 5 X Stacking 7 X 7 X 7 X... X Righting 2 5 X Tear 5 X 1 Flexible IBCs must be capable of withstanding the vibration test. 2 This... each test. 6 The vibration test may be performed in another order for IBCs manufactured and tested...

Analysis and control of the vibration of doubly fed wind turbine

NASA Astrophysics Data System (ADS)

Yu, Manye; Lin, Ying

2017-01-01

The fault phenomena of the violent vibration of certain doubly-fed wind turbine were researched comprehensively, and the dynamic characteristics, load and fault conditions of the system were discussed. Firstly, the structural dynamics analysis of wind turbine is made, and the dynamics mold is built. Secondly, the vibration testing of wind turbine is done with the German test and analysis systems BBM. Thirdly, signal should be analyzed and dealt with. Based on the experiment, spectrum analysis of the motor dynamic balance can be made by using signal processing toolbox of MATLAB software, and the analysis conclusions show that the vibration of wind turbine is caused by dynamic imbalance. The results show that integrating mechanical system dynamics theory with advanced test technology can solve the vibration problem more successfully, which is important in vibration diagnosis of mechanical equipment.

Vibration and noise analysis of a gear transmission system

NASA Technical Reports Server (NTRS)

Choy, F. K.; Qian, W.; Zakrajsek, J. J.; Oswald, F. B.

1993-01-01

This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig.

System transmits mechanical vibration into hazardous environment

NASA Technical Reports Server (NTRS)

Armstrong, D. G.; Gaal, A. E.

1965-01-01

Vibration transducers are tested in a hazardous environment using a single axis transmission system with an electromagnetic shaker table and vibrating wires which drive identical rocker arms, one in the test cell and the other outside. This system can be modified for a multiaxis configuration.

Research on the design of fixture for motor vibration test

NASA Astrophysics Data System (ADS)

Shen, W. X.; Ma, W. S.; Zhang, L. W.

2018-03-01

The vibration reliability of the new energy automobile motor plays a very important role in driving safety, so it is very important to test the vibration durability of the motor. In the vibration test process, the fixture is very important, simulated road spectrum signal vibration can be transmitted without distortion to the motor through the fixture, fixture design directly affect the result of vibration endurance test. On the basis of new energy electric vehicle motor concrete structure, Two fixture design and fixture installation schemes for lateral cantilever type and base bearing type are put forward in this article, the selection of material, weighting process, middle alignment process and manufacturing process are summarized.The modal analysis and frequency response calculation of the fixture are carried out in this design, combine with influence caused by fixture height and structure profile on response frequency, the response frequency of each order of the fixture is calculated, then ultimately achieve the purpose of guiding the design.

Dual-Actuator Active Vibration-Control System

NASA Technical Reports Server (NTRS)

Kascak, Albert F.; Kiraly, Louis J.; Montague, Gerald T.; Palazzolo, Alan B.; Manchala, Daniel

1994-01-01

Dual-actuator active vibration-control (DAAVC) system is developmental system of type described in "Active Vibration Dampers for Rotating Machinery" (LEW-15427). System features sensors and actuators positioned and oriented at bearings to measure and counteract vibrations of shaft along either of two axes perpendicular to axis of rotation. Effective in damping vibrations of helicopter-engine test stand, making it safer to operate engine at speeds near and above first resonance of engine/test-stand system. Opens new opportunities for engine designers to draw more power from engine, and concept applicable to other rotating machines.

Experimental analysis of thread movement in bolted connections due to vibrations

NASA Technical Reports Server (NTRS)

Ramsey, G. ED; Jenkins, Robert C.

1995-01-01

This is the final report of research project NAS8-39131 #33 sponsored by NASA's George C. Marshall Space Flight Center (MSFC) and carried out by the Civil Engineering Department of Auburn University (Auburn, Alabama) and personnel of MSFC. The objective of this study was to identify the main design parameters contributing to the loosening of bolts due to vibration and to identify their relative importance and degree of contribution to bolt loosening. Vibration testing was conducted on a shaketable with a controlled-random input in the dynamic testing laboratory of the Structural Test Division of MSFC. Test specimens which contained one test bolt were vibrated for a fixed amount of time and a percentage of pre-load loss was measured. Each specimen tested implemented some combination of eleven design parameters as dictated by the design of experiment methodology employed. The eleven design parameters were: bolt size (diameter), lubrication on bolt, hole tolerance, initial pre-load, nut locking device, grip length, thread pitch, lubrication between mating materials, class of fit, joint configuration, and mass of configuration. These parameters were chosen for this experiment because they are believed to be the design parameters having the greatest impact on bolt loosening. Two values of each design parameter were used and each combination of parameters tested was subjected to two different directions of vibration and two different g-levels of vibration. One replication was made for each test to gain some indication of experimental error and repeatability and to give some degree of statistical credibility to the data, resulting in a total of 96 tests being performed. The results of the investigation indicated that nut locking devices, joint configuration, fastener size, and mass of configuration were significant in bolt loosening due to vibration. The results of this test can be utilized to further research the complex problem of bolt loosening due to vibration.

Vibration-reducing gloves: transmissibility at the palm of the hand in three orthogonal directions.

PubMed

McDowell, Thomas W; Dong, Ren G; Welcome, Daniel E; Xu, Xueyan S; Warren, Christopher

2013-01-01

Vibration-reducing (VR) gloves are commonly used as a means to help control exposures to hand-transmitted vibrations generated by powered hand tools. The objective of this study was to characterise the vibration transmissibility spectra and frequency-weighted vibration transmissibility of VR gloves at the palm of the hand in three orthogonal directions. Seven adult males participated in the evaluation of seven glove models using a three-dimensional hand-arm vibration test system. Three levels of hand coupling force were applied in the experiment. This study found that, in general, VR gloves are most effective at reducing vibrations transmitted to the palm along the forearm direction. Gloves that are found to be superior at reducing vibrations in the forearm direction may not be more effective in the other directions when compared with other VR gloves. This casts doubts on the validity of the standardised glove screening test. Practitioner Summary: This study used human subjects to measure three-dimensional vibration transmissibility of vibration-reducing gloves at the palm and identified their vibration attenuation characteristics. This study found the gloves to be most effective at reducing vibrations along the forearm direction. These gloves did not effectively attenuate vibration along the handle axial direction.

Optical fiber grating vibration sensor for vibration monitoring of hydraulic pump

NASA Astrophysics Data System (ADS)

Zhang, Zhengyi; Liu, Chuntong; Li, Hongcai; He, Zhenxin; Zhao, Xiaofeng

2017-06-01

In view of the existing electrical vibration monitoring traditional hydraulic pump vibration sensor, the high false alarm rate is susceptible to electromagnetic interference and is not easy to achieve long-term reliable monitoring, based on the design of a beam of the uniform strength structure of the fiber Bragg grating (FBG) vibration sensor. In this paper, based on the analysis of the vibration theory of the equal strength beam, the principle of FBG vibration tuning based on the equal intensity beam is derived. According to the practical application of the project, the structural dimensions of the equal strength beam are determined, and the optimization design of the vibrator is carried out. The finite element analysis of the sensor is carried out by ANSYS, and the first order resonant frequency is 94.739 Hz. The vibration test of the sensor is carried out by using the vibration frequency of 35 Hz and the vibration source of 50 Hz. The time domain and frequency domain analysis results of test data show that the sensor has good dynamic response characteristics, which can realize the accurate monitoring of the vibration frequency and meet the special requirements of vibration monitoring of hydraulic pump under specific environment.

System level mechanical testing of the Clementine spacecraft

NASA Technical Reports Server (NTRS)

Haughton, James; Hauser, Joseph; Raynor, William; Lynn, Peter

1994-01-01

This paper discusses the system level structural testing that was performed to qualify the Clementine Spacecraft for flight. These tests included spin balance, combined acoustic and axial random vibration, lateral random vibration, quasi-static loads, pyrotechnic shock, modal survey and on-orbit jitter simulation. Some innovative aspects of this effort were: the simultaneously combined acoustic and random vibration test; the mass loaded interface modal survey test; and the techniques used to assess how operating on board mechanisms and thrusters affect sensor vision.

Topographic analysis of the skull vibration-induced nystagmus test with piezoelectric accelerometers and force sensors.

PubMed

Dumas, Georges; Lion, Alexis; Perrin, Philippe; Ouedraogo, Evariste; Schmerber, Sébastien

2016-03-23

Vibration-induced nystagmus is elicited by skull or posterior cervical muscle stimulations in patients with vestibular diseases. Skull vibrations delivered by the skull vibration-induced nystagmus test are known to stimulate the inner ear structures directly. This study aimed to measure the vibration transfer at different cranium locations and posterior cervical regions to contribute toward stimulus topographic optimization (experiment 1) and to determine the force applied on the skull with a hand-held vibrator to study the test reproducibility and provide recommendations for good clinical practices (experiment 2). In experiment 1, a 100 Hz hand-held vibrator was applied on the skull (vertex, mastoids) and posterior cervical muscles in 11 healthy participants. Vibration transfer was measured by piezoelectric sensors. In experiment 2, the vibrator was applied 30 times by two experimenters with dominant and nondominant hands on a mannequin equipped to measure the force. Experiment 1 showed that after unilateral mastoid vibratory stimulation, the signal transfer was higher when recorded on the contralateral mastoid than on the vertex or posterior cervical muscles (P<0.001). No difference was observed between the different vibratory locations when vibration transfer was measured on vertex and posterior cervical muscles. Experiment 2 showed that the force applied to the mannequin varied according to the experimenters and the handedness, higher forces being observed with the most experienced experimenter and with the dominant hand (10.3 ± 1.0 and 7.8 ± 2.9 N, respectively). The variation ranged from 9.8 to 29.4% within the same experimenter. Bone transcranial vibration transfer is more efficient from one mastoid to the other mastoid than other anatomical sites. The mastoid is therefore the optimal site for skull vibration-induced nystagmus test in patients with unilateral vestibular lesions and enables a stronger stimulation of the healthy side. In clinical practice, the vibrator should be placed on the mastoid and should be held by the clinician's dominant hand.

Hand-arm Vibration Effects on Performance, Tactile Acuity, and Temperature of Hand

PubMed Central

Forouharmajd, Farhad; Yadegari, Mehrdad; Ahmadvand, Masoumeh; Forouharmajd, Farshad; Pourabdian, Siamak

2017-01-01

Effects of vibration appear as mechanical and psychological disorders, including stress reactions, cognitive and movement disorders, problem in concentration and paying attention to the assigned duties. The common signs and symptoms of hand-arm vibration (HAV) in the fingers and hands may appear as pins and needles feeling, tingling, numbness, and also the loss of finger sensation and dexterity. Laboratory Virtual Instrument Engineering Workbench programming software designed for occupational vibrations measurement was used to calculate HAV acceleration. Hole steadiness test is designed to measure involuntary movement of people. V-Pieron test is designed for one of the other aspects of the psycho motor phenomena of steadiness by moving the stylus across a V-form ruler. The two points test was an experiment of touch acuity, which used a caliper by placing the two styli very close on the pad of finger knuckles. The temperature of finger skin is also measured simultaneous to the above tests. Wilcoxon test indicated that a significant decrement in hand steadiness occurred after gripping a vibrating handle for 2 min (P ≤ 0.003). Wilcoxon test also represented a significant change in errors after gripping a grinder vibratory handle (P ≤ 0.003). The differences at all of the knuckles were significant with a confidence interval percentage of 99%. There was a significant reduction in finger skin temperature before and after exposure to vibration (mean = 0.45°C, based on paired sample test). The obtained results considerably demonstrated the relation between hand performance and vibrations due to gripping a grinder. It can be concluded that an injury or accident may happen after exposure to vibrations for the fine duties, in fast actions. PMID:29204383

Hand-arm Vibration Effects on Performance, Tactile Acuity, and Temperature of Hand.

PubMed

Forouharmajd, Farhad; Yadegari, Mehrdad; Ahmadvand, Masoumeh; Forouharmajd, Farshad; Pourabdian, Siamak

2017-01-01

Effects of vibration appear as mechanical and psychological disorders, including stress reactions, cognitive and movement disorders, problem in concentration and paying attention to the assigned duties. The common signs and symptoms of hand-arm vibration (HAV) in the fingers and hands may appear as pins and needles feeling, tingling, numbness, and also the loss of finger sensation and dexterity. Laboratory Virtual Instrument Engineering Workbench programming software designed for occupational vibrations measurement was used to calculate HAV acceleration. Hole steadiness test is designed to measure involuntary movement of people. V-Pieron test is designed for one of the other aspects of the psycho motor phenomena of steadiness by moving the stylus across a V-form ruler. The two points test was an experiment of touch acuity, which used a caliper by placing the two styli very close on the pad of finger knuckles. The temperature of finger skin is also measured simultaneous to the above tests. Wilcoxon test indicated that a significant decrement in hand steadiness occurred after gripping a vibrating handle for 2 min ( P ≤ 0.003). Wilcoxon test also represented a significant change in errors after gripping a grinder vibratory handle ( P ≤ 0.003). The differences at all of the knuckles were significant with a confidence interval percentage of 99%. There was a significant reduction in finger skin temperature before and after exposure to vibration (mean = 0.45°C, based on paired sample test). The obtained results considerably demonstrated the relation between hand performance and vibrations due to gripping a grinder. It can be concluded that an injury or accident may happen after exposure to vibrations for the fine duties, in fast actions.

30 CFR 75.211 - Roof testing and scaling.

Code of Federal Regulations, 2011 CFR

2011-07-01

... examination does not disclose a hazardous condition, sound and vibration roof tests, or other equivalent tests, shall be made where supports are to be installed. When sound and vibration tests are made, they shall be...

30 CFR 75.211 - Roof testing and scaling.

Code of Federal Regulations, 2014 CFR

2014-07-01

... examination does not disclose a hazardous condition, sound and vibration roof tests, or other equivalent tests, shall be made where supports are to be installed. When sound and vibration tests are made, they shall be...

30 CFR 75.211 - Roof testing and scaling.

Code of Federal Regulations, 2012 CFR

2012-07-01

... examination does not disclose a hazardous condition, sound and vibration roof tests, or other equivalent tests, shall be made where supports are to be installed. When sound and vibration tests are made, they shall be...

30 CFR 75.211 - Roof testing and scaling.

Code of Federal Regulations, 2013 CFR

2013-07-01

... examination does not disclose a hazardous condition, sound and vibration roof tests, or other equivalent tests, shall be made where supports are to be installed. When sound and vibration tests are made, they shall be...

Summary of AH-1G flight vibration data for validation of coupled rotor-fuselage analyses

NASA Technical Reports Server (NTRS)

Dompka, R. V.; Cronkhite, J. D.

1986-01-01

Under a NASA research program designated DAMVIBS (Design Analysis Methods for VIBrationS), four U. S. helicopter industry participants (Bell Helicopter, Boeing Vertol, McDonnell Douglas Helicopter, and Sikorsky Aircraft) are to apply existing analytical methods for calculating coupled rotor-fuselage vibrations of the AH-1G helicopter for correlation with flight test data from an AH-1G Operational Load Survey (OLS) test program. Bell Helicopter, as the manufacturer of the AH-1G, was asked to provide pertinent rotor data and to collect the OLS flight vibration data needed to perform the correlations. The analytical representation of the fuselage structure is based on a NASTRAN finite element model (FEM) developed by Bell which has been extensively documented and correlated with ground vibration tests.The AH-1G FEM was provided to each of the participants for use in their coupled rotor-fuselage analyses. This report describes the AH-1G OLS flight test program and provides the flight conditions and measured vibration data to be used by each participant in their correlation effort. In addition, the mechanical, structural, inertial and aerodynamic data for the AH-1G two-bladed teetering main rotor system are presented. Furthermore, modifications to the NASTRAN FEM of the fuselage structure that are necessary to make it compatible with the OLS test article are described. The AH-1G OLS flight test data was found to be well documented and provide a sound basis for evaluating currently existing analysis methods used for calculation of coupled rotor-fuselage vibrations.

A Quadruped Micro-Robot Based on Piezoelectric Driving

PubMed Central

Su, Qi; Quan, Qiquan; Deng, Jie; Yu, Hongpeng

2018-01-01

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s. PMID:29518964

A Quadruped Micro-Robot Based on Piezoelectric Driving.

PubMed

Su, Qi; Quan, Qiquan; Deng, Jie; Yu, Hongpeng

2018-03-07

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s.

Development of rotorcraft interior noise control concepts. Phase 2: Full scale testing, revision 1

NASA Technical Reports Server (NTRS)

Yoerkie, C. A.; Gintoli, P. J.; Moore, J. A.

1986-01-01

The phase 2 effort consisted of a series of ground and flight test measurements to obtain data for validation of the Statistical Energy Analysis (SEA) model. Included in the gound tests were various transfer function measurements between vibratory and acoustic subsystems, vibration and acoustic decay rate measurements, and coherent source measurements. The bulk of these, the vibration transfer functions, were used for SEA model validation, while the others provided information for characterization of damping and reverberation time of the subsystems. The flight test program included measurements of cabin and cockpit sound pressure level, frame and panel vibration level, and vibration levels at the main transmission attachment locations. Comparisons between measured and predicted subsystem excitation levels from both ground and flight testing were evaluated. The ground test data show good correlation with predictions of vibration levels throughout the cabin overhead for all excitations. The flight test results also indicate excellent correlation of inflight sound pressure measurements to sound pressure levels predicted by the SEA model, where the average aircraft speech interference level is predicted within 0.2 dB.

Force limits measured on a space shuttle flight

NASA Technical Reports Server (NTRS)

Scharton, T.

2000-01-01

The random vibration forces between a payload and the sidewall of the space shuttle have been measured in flight and compared with the force specifications used in ground vibration tests. The flight data are in agreement with a semi-empirical method, which is widely used to predict vibration test force limits.

Radiation Analysis Program

DTIC Science & Technology

2018-02-28

qualification testing to include vibrational, thermal bake and thermal cycling to ensure the experiment would perform as expected during operation on...series of tests for flight qualification. These tests included bake and thermal cycling. In addition, vibrational testing was also accomplished

Noise-Induced Building Vibrations Caused by Concorde and Conventional Aircraft Operations at Dulles and Kennedy International Airports

NASA Technical Reports Server (NTRS)

Mayes, W. H.; Stephens, D. G.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.; Deloach, R.; Cawthorn, J. M.; Finley, T. D.; Lynch, J. W.

1978-01-01

Outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded, as were the associated vibration levels in the walls, windows, and floors at building test sites. In addition, limited subjective tests were conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise. Representative peak levels of aircraft noise-induced building vibrations are reported and comparisons are made with structural damage criteria and with vibration levels induced by common domestic events. In addition, results of a pilot study are reported which indicate the human detection threshold for noise-induced floor vibrations.

A New Approach in Force-Limited Vibration Testing of Flight Hardware

NASA Technical Reports Server (NTRS)

Kolaini, Ali R.; Kern, Dennis L.

2012-01-01

The force-limited vibration test approaches discussed in NASA-7004C were developed to reduce overtesting associated with base shake vibration tests of aerospace hardware where the interface responses are excited coherently. This handbook outlines several different methods of specifying the force limits. The rationale for force limiting is based on the disparity between the impedances of typical aerospace mounting structures and the large impedances of vibration test shakers when the interfaces in general are coherently excited. Among these approaches, the semi-empirical method is presently the most widely used method to derive the force limits. The inclusion of the incoherent excitation of the aerospace structures at mounting interfaces has not been accounted for in the past and provides the basis for more realistic force limits for qualifying the hardware using shaker testing. In this paper current methods for defining the force limiting specifications discussed in the NASA handbook are reviewed using data from a series of acoustic and vibration tests. A new approach based on considering the incoherent excitation of the structural mounting interfaces using acoustic test data is also discussed. It is believed that the new approach provides much more realistic force limits that may further remove conservatism inherent in shaker vibration testing not accounted for by methods discussed in the NASA handbook. A discussion on using FEM/BEM analysis to obtain realistic force limits for flight hardware is provided.

Non-contact modal testing by the electromagnetic acoustic principle: Applications to bending and torsional vibrations of metallic pipes

NASA Astrophysics Data System (ADS)

Kim, Hongjin; Park, Chan Il; Lee, Sun Ho; Kim, Yoon Young

2013-02-01

This work aims to investigate a possibility of non-contact vibration modal testing for bending and torsional motions of cylindrical bodies such as pipes. Here, a transducer operated by the electromagnetic acoustic coupling principle is newly devised. Depending on vibration modes, bending or torsional, different magnetic circuit configurations are employed to fabricate the transducer. The main characteristic of the proposed transducer is non-contact vibration generation in a test specimen without any mechanical movement of the actuating unit. It can be also used as a non-contact sensing unit if necessary. The validity and the performance of the proposed non-contact modal testing method are checked with several experiments.

Research on mining truck vibration control based on particle damping

NASA Astrophysics Data System (ADS)

Liming, Song; Wangqiang, Xiao; Zeguang, Li; Haiquan, Guo; Zhe, Yang

2018-03-01

More and more attentions were got by people about the research on mining truck driving comfort. As the vibration transfer terminal, cab is one of the important part of mining truck vibration control. In this paper, based on particle damping technology and its application characteristics, through the discrete element modeling, DEM & FEM coupling simulation and analysis, lab test verification and actual test in the truck, particle damping technology was successfully used in driver’s seat base of mining truck, cab vibration was reduced obviously, meanwhile applied research and method of particle damping technology in mining truck vibration control were provided.

A Resonant Damping Study Using Piezoelectric Materials

NASA Technical Reports Server (NTRS)

Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

2008-01-01

Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

Vibration manual

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.

Automation of vibroacoustic data bank for random vibration criteria development. [for the space shuttle and launch vehicles

NASA Technical Reports Server (NTRS)

Ferebee, R. C.

1982-01-01

A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablet, and a dry-silver hard copier which are all desk-top type hardware and occupy minimal space. The data bank contains data from the Saturn V and Titan III flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one-third octave band plots over the frequency range from 20 to 2000 Hz. The data was stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data was statistically analyzed and the resulting 97.5% probability levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. This automated vibroacoustic data bank system greatly enhances the speed and accuracy of formulating vibration test criteria. In the future, the data bank will be expanded to include all data acquired from the space shuttle flight test program.

Examining the Usefulness of ISO 10819 Anti-Vibration Glove Certification.

PubMed

Budd, Diandra; House, Ron

2017-03-01

Anti-vibration gloves are commonly worn to reduce hand-arm vibration exposure from work with hand-held vibrating tools when higher priority and more effective controls are unavailable. For gloves to be marketed as 'anti-vibration' they must meet the vibration transmissibility criteria described in the International Organization for Standardization (ISO) standard 10819 (2013). Several issues exist with respect to the methodology used for glove testing as well as the requirements for glove design and composition in ISO 10819 (2013). The true usefulness of anti-vibration gloves at preventing hand-arm vibration syndrome (HAVS) is controversial, given that their performance is dependent on tool vibration characteristics and the anthropometrics of workers in real working conditions. The major risk associated with the use of anti-vibration gloves is that it will give employees and employers a false sense of protection against the negative effects of hand-transmitted vibration. This commentary examines the limitations of the current international standards for anti-vibration glove testing and certification, thereby calling into question the degree of protection that anti-vibration gloves provide against HAVS, and cautioning users to consider both their benefits and potential drawbacks on a case-by-case basis. © The Author 2017. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Vibration-reducing gloves: transmissibility at the palm of the hand in three orthogonal directions

PubMed Central

McDowell, Thomas W.; Dong, Ren G.; Welcome, Daniel E.; Xu, Xueyan S.; Warren, Christopher

2015-01-01

Vibration-reducing (VR) gloves are commonly used as a means to help control exposures to hand-transmitted vibrations generated by powered hand tools. The objective of this study was to characterise the vibration transmissibility spectra and frequency-weighted vibration transmissibility of VR gloves at the palm of the hand in three orthogonal directions. Seven adult males participated in the evaluation of seven glove models using a three-dimensional hand–arm vibration test system. Three levels of hand coupling force were applied in the experiment. This study found that, in general, VR gloves are most effective at reducing vibrations transmitted to the palm along the forearm direction. Gloves that are found to be superior at reducing vibrations in the forearm direction may not be more effective in the other directions when compared with other VR gloves. This casts doubts on the validity of the standardised glove screening test. Practitioner Summary This study used human subjects to measure three-dimensional vibration transmissibility of vibration-reducing gloves at the palm and identified their vibration attenuation characteristics. This study found the gloves to be most effective at reducing vibrations along the forearm direction. These gloves did not effectively attenuate vibration along the handle axial direction. PMID:24160755

Analysis and modification of a single-mesh gear fatigue rig for use in diagnostic studies

NASA Technical Reports Server (NTRS)

Zakrajsek, James J.; Townsend, Dennis P.; Oswald, Fred B.; Decker, Harry J.

1992-01-01

A single-mesh gear fatigue rig was analyzed and modified for use in gear mesh diagnostic research. The fatigue rig allowed unwanted vibration to mask the test-gear vibration signal, making it difficult to perform diagnostic studies. Several possible sources and factors contributing to the unwanted components of the vibration signal were investigated. Sensor mounting location was found to have a major effect on the content of the vibration signal. In the presence of unwanted vibration sources, modal amplification made unwanted components strong. A sensor location was found that provided a flatter frequency response. This resulted in a more useful vibration signal. A major network was performed on the fatigue rig to reduce the influence of the most probable sources of the noise in the vibration signal. The slave gears were machined to reduce weight and increase tooth loading. The housing and the shafts were modified to reduce imbalance, looseness, and misalignment in the rotating components. These changes resulted in an improved vibration signal, with the test-gear mesh frequency now the dominant component in the signal. Also, with the unwanted sources eliminated, the sensor mounting location giving the most robust representation of the test-gear meshing energy was found to be at a point close to the test gears in the load zone of the bearings.

[Study on the vibrational spectra and XRD characters of Huanglong jade from Longling County, Yunnan Province].

PubMed

Pei, Jing-cheng; Fan, Lu-wei; Xie, Hao

2014-12-01

Based on the conventional test methods, the infrared absorption spectrum, Raman spectrum and X-ray diffraction (XRD) were employed to study the characters of the vibration spectrum and mineral composition of Huanglong jade. The testing results show that Huanglong jade shows typical vibrational spectrum characteristics of quartziferous jade. The main infrared absorption bands at 1162, 1076, 800, 779, 691, 530 and 466 cm(-1) were induced by the asymmetric stretching vibration, symmetrical stretching vibration and bending vibration of Si-O-Si separately. Especially the absorption band near 800 cm(-1) is split, which indicates that Huanglong jade has good crystallinity. In Raman spectrum, the main strong vibration bands at 463 and 355 cm(-1) were attributed to bending vibration of Si-O-Si. XRD test confirmed that Quartz is main mineral composition of Huanglong jade and there is a small amount of hematite in red color samples which induced the red color of Huanglong jade. This is the first report on the infrared, Raman and XRD spectra feature of Huanglong jade. It will provide a scientific basis for the identification, naming and other research for huanglong jade.

Ground vibration test results of a JetStar airplane using impulsive sine excitation

NASA Technical Reports Server (NTRS)

Kehoe, Michael W.; Voracek, David F.

1989-01-01

Structural excitation is important for both ground vibration and flight flutter testing. The structural responses caused by this excitation are analyzed to determine frequency, damping, and mode shape information. Many excitation waveforms have been used throughout the years. The use of impulsive sine (sin omega t)/omega t as an excitation waveform for ground vibration testing and the advantages of using this waveform for flight flutter testing are discussed. The ground vibration test results of a modified JetStar airplane using impulsive sine as an excitation waveform are compared with the test results of the same airplane using multiple-input random excitation. The results indicated that the structure was sufficiently excited using the impulsive sine waveform. Comparisons of input force spectrums, mode shape plots, and frequency and damping values for the two methods of excitation are presented.

Developing Uncertainty Models for Robust Flutter Analysis Using Ground Vibration Test Data

NASA Technical Reports Server (NTRS)

Potter, Starr; Lind, Rick; Kehoe, Michael W. (Technical Monitor)

2001-01-01

A ground vibration test can be used to obtain information about structural dynamics that is important for flutter analysis. Traditionally, this information#such as natural frequencies of modes#is used to update analytical models used to predict flutter speeds. The ground vibration test can also be used to obtain uncertainty models, such as natural frequencies and their associated variations, that can update analytical models for the purpose of predicting robust flutter speeds. Analyzing test data using the -norm, rather than the traditional 2-norm, is shown to lead to a minimum-size uncertainty description and, consequently, a least-conservative robust flutter speed. This approach is demonstrated using ground vibration test data for the Aerostructures Test Wing. Different norms are used to formulate uncertainty models and their associated robust flutter speeds to evaluate which norm is least conservative.

Method and apparatus for determining material structural integrity

DOEpatents

Pechersky, M.J.

1994-01-01

Disclosed are a nondestructive method and apparatus for determining the structural integrity of materials by combining laser vibrometry with damping analysis to determine the damping loss factor. The method comprises the steps of vibrating the area being tested over a known frequency range and measuring vibrational force and velocity vs time over the known frequency range. Vibrational velocity is preferably measured by a laser vibrometer. Measurement of the vibrational force depends on the vibration method: if an electromagnetic coil is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by the coil current. If a reciprocating transducer is used, the vibrational force is determined by a force gauge in the transducer. Using vibrational analysis, a plot of the drive point mobility of the material over the preselected frequency range is generated from the vibrational force and velocity data. Damping loss factor is derived from a plot of the drive point mobility over the preselected frequency range using the resonance dwell method and compared with a reference damping loss factor for structural integrity evaluation.

Fixed Base Modal Testing Using the NASA GRC Mechanical Vibration Facility

NASA Technical Reports Server (NTRS)

Staab, Lucas D.; Winkel, James P.; Suarez, Vicente J.; Jones, Trevor M.; Napolitano, Kevin L.

2016-01-01

The Space Power Facility at NASA's Plum Brook Station houses the world's largest and most powerful space environment simulation facilities, including the Mechanical Vibration Facility (MVF), which offers the world's highest-capacity multi-axis spacecraft shaker system. The MVF was designed to perform sine vibration testing of a Crew Exploration Vehicle (CEV)-class spacecraft with a total mass of 75,000 pounds, center of gravity (cg) height above the table of 284 inches, diameter of 18 feet, and capability of 1.25 gravity units peak acceleration in the vertical and 1.0 gravity units peak acceleration in the lateral directions. The MVF is a six-degree-of-freedom, servo-hydraulic, sinusoidal base-shake vibration system that has the advantage of being able to perform single-axis sine vibration testing of large structures in the vertical and two lateral axes without the need to reconfigure the test article for each axis. This paper discusses efforts to extend the MVF's capabilities so that it can also be used to determine fixed base modes of its test article without the need for an expensive test-correlated facility simulation.

Hand function in workers with hand-arm vibration syndrome.

PubMed

Cederlund, R; Isacsson, A; Lundborg, G

1999-01-01

Hand-arm vibration syndrome has been specially addressed in the Scandinavian countries in recent years, but the syndrome is still not sufficiently recognized in many countries. The object of this preliminary study was to describe the nature and character of vibration-induced impairment in the hands of exposed workers. Twenty symptomatic male workers (aged 28 to 65 years) subjected to vibration by hand-held tools were interviewed about subjective symptoms and activities of daily living and were assessed with a battery of objective tests for sensibility, dexterity, grip function, and grip strength. The test results were compared with normative data. The majority of patients complained of cold intolerance, numbness, pain, sensory impairment, and difficulties in handling manual tools and in handwriting. The various objective tests showed considerable variation in indications of pathologic outcome, revealing differences in sensitivity to detect impaired hand function. Semmes-Weinstein monofilament testing for perception of light touch-deep pressure sensation, the small-object shape identification test, and moving two-point discrimination testing for functional sensibility provided the most indications of pathologic outcomes. The authors conclude that vibration-exposed patients present considerable impairment in hand function.

Ground vibration test results for Drones for Aerodynamic and Structural Testing (DAST)/Aeroelastic Research Wing (ARW-1R) aircraft

NASA Technical Reports Server (NTRS)

Cox, T. H.; Gilyard, G. B.

1986-01-01

The drones for aerodynamic and structural testing (DAST) project was designed to control flutter actively at high subsonic speeds. Accurate knowledge of the structural model was critical for the successful design of the control system. A ground vibration test was conducted on the DAST vehicle to determine the structural model characteristics. This report presents and discusses the vibration and test equipment, the test setup and procedures, and the antisymmetric and symmetric mode shape results. The modal characteristics were subsequently used to update the structural model employed in the control law design process.

Gearbox Tooth Cut Fault Diagnostics Using Acoustic Emission and Vibration Sensors — A Comparative Study

PubMed Central

Qu, Yongzhi; He, David; Yoon, Jae; Van Hecke, Brandon; Bechhoefer, Eric; Zhu, Junda

2014-01-01

In recent years, acoustic emission (AE) sensors and AE-based techniques have been developed and tested for gearbox fault diagnosis. In general, AE-based techniques require much higher sampling rates than vibration analysis-based techniques for gearbox fault diagnosis. Therefore, it is questionable whether an AE-based technique would give a better or at least the same performance as the vibration analysis-based techniques using the same sampling rate. To answer the question, this paper presents a comparative study for gearbox tooth damage level diagnostics using AE and vibration measurements, the first known attempt to compare the gearbox fault diagnostic performance of AE- and vibration analysis-based approaches using the same sampling rate. Partial tooth cut faults are seeded in a gearbox test rig and experimentally tested in a laboratory. Results have shown that the AE-based approach has the potential to differentiate gear tooth damage levels in comparison with the vibration-based approach. While vibration signals are easily affected by mechanical resonance, the AE signals show more stable performance. PMID:24424467

Vibration reduction of pneumatic percussive rivet tools: mechanical and ergonomic re-design approaches.

PubMed

Cherng, John G; Eksioglu, Mahmut; Kizilaslan, Kemal

2009-03-01

This paper presents a systematic design approach, which is the result of years of research effort, to ergonomic re-design of rivet tools, i.e. rivet hammers and bucking bars. The investigation was carried out using both ergonomic approach and mechanical analysis of the rivet tools dynamic behavior. The optimal mechanical design parameters of the re-designed rivet tools were determined by Taguchi method. Two ergonomically re-designed rivet tools with vibration damping/isolation mechanisms were tested against two conventional rivet tools in both laboratory and field tests. Vibration characteristics of both types of tools were measured by laboratory tests using a custom-made test fixture. The subjective field evaluations of the tools were performed by six experienced riveters at an aircraft repair shop. Results indicate that the isolation spring and polymer damper are very effective in reducing the overall level of vibration under both unweighted and weighted acceleration conditions. The mass of the dolly head and the housing played a significant role in the vibration absorption of the bucking bars. Another important result was that the duct iron has better vibration reducing capability compared to steel and aluminum for bucking bars. Mathematical simulation results were also consistent with the experimental results. Overall conclusion obtained from the study was that by applying the design principles of ergonomics and by adding vibration damping/isolation mechanisms to the rivet tools, the vibration level can significantly be reduced and the tools become safer and user friendly. The details of the experience learned, design modifications, test methods, mathematical models and the results are included in the paper.

Adaptive-passive vibration control systems for industrial applications

NASA Astrophysics Data System (ADS)

Mayer, D.; Pfeiffer, T.; Vrbata, J.; Melz, T.

2015-04-01

Tuned vibration absorbers have become common for passive vibration reduction in many industrial applications. Lightly damped absorbers (also called neutralizers) can be used to suppress narrowband disturbances by tuning them to the excitation frequency. If the resonance is adapted in-operation, the performance of those devices can be significantly enhanced, or inertial mass can be decreased. However, the integration of actuators, sensors and control electronics into the system raises new design challenges. In this work, the development of adaptive-passive systems for vibration reduction at an industrial scale is presented. As an example, vibration reduction of a ship engine was studied in a full scale test. Simulations were used to study the feasibility and evaluate the system concept at an early stage. Several ways to adjust the resonance of the neutralizer were evaluated, including piezoelectric actuation and common mechatronic drives. Prototypes were implemented and tested. Since vibration absorbers suffer from high dynamic loads, reliability tests were used to assess the long-term behavior under operational conditions and to improve the components. It was proved that the adaptive systems are capable to withstand the mechanical loads in an industrial application. Also a control strategy had to be implemented in order to track the excitation frequency. The most mature concepts were integrated into the full scale test. An imbalance exciter was used to simulate the engine vibrations at a realistic level experimentally. The neutralizers were tested at varying excitation frequencies to evaluate the tracking capabilities of the control system. It was proved that a significant vibration reduction is possible.

TEST SYSTEM FOR EVALUATING SPENT NUCLEAR FUEL BENDING STIFFNESS AND VIBRATION INTEGRITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John; Wang, Hong; Bevard, Bruce Balkcom

2013-01-01

Transportation packages for spent nuclear fuel (SNF) must meet safety requirements specified by federal regulations. For normal conditions of transport, vibration loads incident to transport must be considered. This is particularly relevant for high-burnup fuel (>45 GWd/MTU). As the burnup of the fuel increases, a number of changes occur that may affect the performance of the fuel and cladding in storage and during transportation. The mechanical properties of high-burnup de-fueled cladding have been previously studied by subjecting defueled cladding tubes to longitudinal (axial) tensile tests, ring-stretch tests, ring-compression tests, and biaxial tube burst tests. The objective of this study ismore » to investigate the mechanical properties and behavior of both the cladding and the fuel in it under vibration/cyclic loads similar to the sustained vibration loads experienced during normal transport. The vibration loads to SNF rods during transportation can be characterized by dynamic, cyclic, bending loads. The transient vibration signals in a specified transport environment can be analyzed, and frequency, amplitude and phase components can be identified. The methodology being implemented is a novel approach to study the vibration integrity of actual SNF rod segments through testing and evaluating the fatigue performance of SNF rods at defined frequencies. Oak Ridge National Laboratory (ORNL) has developed a bending fatigue system to evaluate the response of the SNF rods to vibration loads. A three-point deflection measurement technique using linear variable differential transformers is used to characterize the bending rod curvature, and electromagnetic force linear motors are used as the driving system for mechanical loading. ORNL plans to use the test system in a hot cell for SNF vibration testing on high burnup, irradiated fuel to evaluate the pellet-clad interaction and bonding on the effective lifetime of fuel-clad structure bending fatigue performance. Technical challenges include pure bending implementation, remote installation and detachment of the SNF test specimen, test specimen deformation measurement, and identification of a driving system suitable for use in a hot cell. Surrogate test specimens have been used to calibrate the test setup and conduct systematic cyclic tests. The calibration and systematic cyclic tests have been used to identify test protocol issues prior to implementation in the hot cell. In addition, cyclic hardening in unidirectional bending and softening in reverse bending were observed in the surrogate test specimens. The interface bonding between the surrogate clad and pellets was found to impact the bending response of the surrogate rods; confirming this behavior in the actual spent fuel segments will be an important aspect of the hot cell test implementation,« less

Vibrational multiconfiguration self-consistent field theory: implementation and test calculations.

PubMed

Heislbetz, Sandra; Rauhut, Guntram

2010-03-28

A state-specific vibrational multiconfiguration self-consistent field (VMCSCF) approach based on a multimode expansion of the potential energy surface is presented for the accurate calculation of anharmonic vibrational spectra. As a special case of this general approach vibrational complete active space self-consistent field calculations will be discussed. The latter method shows better convergence than the general VMCSCF approach and must be considered the preferred choice within the multiconfigurational framework. Benchmark calculations are provided for a small set of test molecules.

Ensuring Safe Exploration: Ares Launch Vehicle Integrated Vehicle Ground Vibration Testing

NASA Technical Reports Server (NTRS)

Tuma, M. L.; Chenevert, D. J.

2009-01-01

Ground vibration testing has been an integral tool for developing new launch vehicles throughout the space age. Several launch vehicles have been lost due to problems that would have been detected by early vibration testing, including Ariane 5, Delta III, and Falcon 1. NASA will leverage experience and testing hardware developed during the Saturn and Shuttle programs to perform ground vibration testing (GVT) on the Ares I crew launch vehicle and Ares V cargo launch vehicle stacks. NASA performed dynamic vehicle testing (DVT) for Saturn and mated vehicle ground vibration testing (MVGVT) for Shuttle at the Dynamic Test Stand (Test Stand 4550) at Marshall Space Flight Center (MSFC) in Huntsville, Alabama, and is now modifying that facility to support Ares I integrated vehicle ground vibration testing (IVGVT) beginning in 2012. The Ares IVGVT schedule shows most of its work being completed between 2010 and 2014. Integrated 2nd Stage Ares IVGVT will begin in 2012 and IVGVT of the entire Ares launch stack will begin in 2013. The IVGVT data is needed for the human-rated Orion launch vehicle's Design Certification Review (DCR) in early 2015. During the Apollo program, GVT detected several serious design concerns, which NASA was able to address before Saturn V flew, eliminating costly failures and potential losses of mission or crew. During the late 1970s, Test Stand 4550 was modified to support the four-body structure of the Space Shuttle. Vibration testing confirmed that the vehicle's mode shapes and frequencies were better than analytical models suggested, however, the testing also identified challenges with the rate gyro assemblies, which could have created flight instability and possibly resulted in loss of the vehicle. Today, NASA has begun modifying Test Stand 4550 to accommodate Ares I, including removing platforms needed for Shuttle testing and upgrading the dynamic test facilities to characterize the mode shapes and resonant frequencies of the vehicle. The IVGVT team expects to collect important information about the new launch vehicles, greatly increasing astronaut safety as NASA prepares to explore the Moon and beyond.

Passive vibration isolation of reaction wheel disturbances using a low frequency flexible space platform

NASA Astrophysics Data System (ADS)

Kamesh, D.; Pandiyan, R.; Ghosal, Ashitava

2012-03-01

Reaction wheel assemblies (RWAs) are momentum exchange devices used in fine pointing control of spacecrafts. Even though the spinning rotor of the reaction wheel is precisely balanced to minimize emitted vibration due to static and dynamic imbalances, precision instrument payloads placed in the neighborhood can always be severely impacted by residual vibration forces emitted by reaction wheel assemblies. The reduction of the vibration level at sensitive payloads can be achieved by placing the RWA on appropriate mountings. A low frequency flexible space platform consisting of folded continuous beams has been designed to serve as a mount for isolating a disturbance source in precision payloads equipped spacecrafts. Analytical and experimental investigations have been carried out to test the usefulness of the low frequency flexible platform as a vibration isolator for RWAs. Measurements and tests have been conducted at varying wheel speeds, to quantify and characterize the amount of isolation obtained from the reaction wheel generated vibration. These tests are further extended to other variants of similar design in order to bring out the best isolation for given disturbance loads. Both time and frequency domain analysis of test data show that the flexible beam platform as a mount for reaction wheels is quite effective and can be used in spacecrafts for passive vibration control.

Effects of controlled whole-body vibration training in improving fall risk factors among individuals with multiple sclerosis: A pilot study.

PubMed

Yang, Feng; Finlayson, Marcia; Bethoux, Francois; Su, Xiaogang; Dillon, Loretta; Maldonado, Hector M

2018-03-01

The purpose of this study was to systematically examine the effect of an 8-week controlled whole-body vibration training on improving fall risk factors and the bone mineral density among people with multiple sclerosis (PwMS). This study adopted a single group pre-test-post-test design. Twenty-five PwMS (50.3 years SD 14.1) received vibration training on a side-alternating vibration platform. Each training session was repeated three times every week for 8 weeks. Prior to and following the 8-week training course, a battery of fall risk factors were evaluated: the body balance, functional mobility, muscle strength, range of motion, and fear of falling. Bone density at both calcanei was also assessed. Twenty-two participants completed the study. Compared with pre-test, almost all fall risk factors and the bone density measurement were significantly improved at post-test, with moderate to large effect sizes varying between 0.571 and 1.007. The 8-week vibration training was well accepted by PwMS and improved their fall risk factors. The important findings of this study were that vibration training may increase the range of motion of ankle joints on the sagittal plane, lower the fear of falling, and improve bone density. IMPLICATIONS FOR REHABILITATION An 8-week vibration training course could be well-accepted by people with multiple sclerosis (MS). Vibration training improves the risk factors of falls in people living with MS. Vibration training could be a promising rehabilitation intervention in individuals with MS.

The Potential Neural Mechanisms of Acute Indirect Vibration

PubMed Central

2011-01-01

There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception suggesting neural enhancement. Nevertheless, the neural mechanism(s) of vibration and its potentiating effect have received little attention. One proposal suggests that spinal reflexes enhance muscle contraction through a reflex activity known as tonic vibration stretch reflex (TVR), which increases muscle activation. However, TVR is based on direct, brief, and high frequency vibration (>100 Hz) which differs to indirect vibration, which is applied to the whole body or body parts at lower vibration frequency (5-45 Hz). Likewise, muscle tuning and neuromuscular aspects are other candidate mechanisms used to explain the vibration phenomenon. But there is much debate in terms of identifying which neural mechanism(s) are responsible for acute vibration; due to a number of studies using various vibration testing protocols. These protocols include: different methods of application, vibration variables, training duration, exercise types and a range of population groups. Therefore, the neural mechanism of acute vibration remain equivocal, but spinal reflexes, muscle tuning and neuromuscular aspects are all viable factors that may contribute in different ways to increasing muscular performance. Additional research is encouraged to determine which neural mechanism(s) and their contributions are responsible for acute vibration. Testing variables and vibration applications need to be standardised before reaching a consensus on which neural mechanism(s) occur during and post-vibration. Key points There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception, but little attention has been given to the neural mechanism(s) of acute indirect vibration. Current findings suggest that acute vibration exposure may cause a neural response, but there is little consensus on identifying which neural mechanism(s) are specifically responsible. This is due to a number of studies using various vibration testing protocols (i.e.varying frequencies, amplitudes, durations, and methods of application). Spinal reflexes, muscle tuning and neuromuscular aspects and central motor command are all viable neuromechanical factors that may contribute at different stages to transiently increasing muscular performance. Additional research is encouraged to determine when (pre, during and post) the different neural mechanism(s) respond to direct and indirect vibration stimuli. PMID:24149291

Wake Shield Facility Modal Survey Test in Vibration Acoustic Test Facility

NASA Image and Video Library

1991-10-09

Astronaut Ronald M. Sega stands beside the University of Houston's Wake Shield Facility before it undergoes a Modal Survey Test in the Vibration and Acoustic Test Facility Building 49, prior to being flown on space shuttle mission STS-60.

Simulation of the dynamic environment for missile component testing: Demonstration

NASA Technical Reports Server (NTRS)

Chang, Kurng Y.

1989-01-01

The problems in defining a realistic test requirement for missile and space vehicle components can be classified into two categories: (1) definition of the test environment representing the expected service condition, and (2) simulation of the desired environment in the test laboratory. Recently, a new three-dimensional (3-D) test facility was completed at the U.S. Army Harry Diamond Laboratory (HDL) to simulate triaxial vibration input to a test specimen. The vibration test system is designed to support multi-axial vibration tests over the frequency range of 5 to 2000 Hertz. The availability of this 3-D test system motivates the development of new methodologies addressing environmental definition and simulation.

Vibration characteristics of dental high-speed turbines and speed-increasing handpieces.

PubMed

Poole, Ruth L; Lea, Simon C; Dyson, John E; Shortall, Adrian C C; Walmsley, A Damien

2008-07-01

Vibrations of dental handpieces may contribute to symptoms of hand-arm vibration syndrome in dental personnel and iatrogenic enamel cracking in teeth. However, methods for measuring dental handpiece vibrations have previously been limited and information about vibration characteristics is sparse. This preliminary study aimed to use a novel approach to assess the vibrations of unloaded high-speed handpieces in vitro. Maximum vibration displacement amplitudes of five air turbines and two speed-increasing handpieces were recorded whilst they were operated with and without a rotary cutting instrument (RCI) using a scanning laser vibrometer (SLV). RCI rotation speeds, calculated from frequency peaks, were consistent with expected values. ANOVA statistical analysis indicated significant differences in vibrations between handpiece models (p<0.01), although post hoc tests revealed that differences between most individual models were not significant (p>0.11). Operating handpieces with a RCI resulted in greater vibrations than with no RCI (p<0.01). Points on the head of the handpiece showed greater vibration displacement amplitudes than points along the body (p<0.01). Although no single measurement exceeded 4 microm for the handpieces in the current test setup (implying that these vibrations may be unlikely to cause adverse effects), this study has formed the basis for future work which will include handpiece vibration measurements whilst cutting under clinically representative loads.

EFFECTOF ISOLATION WALL USING SCRAP TIRE ON GROUND VIBRATION REDUCTION

NASA Astrophysics Data System (ADS)

Kashimoto, Takahiko; Kashimoto, Yusuke; Hayakawa, Kiyoshi; Matsui, Tamotsu; Fujimoto, Hiroaki

Some countermeasure methods against the environmental ground vibration caused by some traffic vibrations have been proposed so far. The authors have developed a new type ground vibration isolation wall using scrap tire, and evaluated its effectiveness on the ground vibration reduction by full scale field tests. In this paper, the authors discussed and examined the effectiveness of the developed countermeasure method by two field tests. The one concerns on the effect of scrap tire as soft material of vibration isolation wall, and the other on the effect of the developed countermeasure method practically applied in a residential area close to monorail traffic. As the results, it was elucidated that the ground vibration of 2-3 dB was reduced in case of two times volume of the soft material, the conversion ratio of the vibration energy of the soft material to the kinetic energy was higher than that of the core material of PHC pile, the vibration acceleration of 0.19 - 1.26 gal was reduced by the developed countermeasure method in case of the monorail traffic, and the vibration reduction measured behind the isolation wall agreed well with the proposed theoretical value, together with confirming the effectiveness of the ground vibration isolation wall using scrap tire as the countermeasure method against the environmental ground vibration.

Study of vibrations produced by a vibrating beam used for vibrating concretes. [and their transmission to human operator

NASA Technical Reports Server (NTRS)

Silas, C.; Brindeu, L.; Grosanu, I.; Cioara, T.

1974-01-01

For compacting concretes in building, vibrating beams are used. The vibrations are generated by inertial vibrators, and the beam is normally displaced by the operator by means of a handle that is elastically fastened to the beam by means of rubber pads. Considered are vibrations transmitted to the operator, taking into account the beam's shock vibration motions. The steady state motion of a dynamic beam pattern is studied, and results of experimental tests with existing equipment are presented.

The multi-axis vibration environment and man.

PubMed

Lovesey, E J

1970-12-01

Many investigations into the effects of vibration on man have been performed since Mallock's first study of London Underground vibrations in 1902. The vibration research has tended to be confined to the vertical (heave) axis, yet recent experiments have indicated that low frequency vibration along the lateral (sway) axis has a greater adverse effect upon comfort and performance. Measurements of the vibration environments in current forms of transport including motor vehicles, hovercraft and aircraft etc have shown that appreciable quantities of vibration along all three axes exist. Further vibration research should consider the effects of multi-axis vibrations upon man rather than limit tests to single axis vibration.

Vibration Control of Deployable Astromast Boom: Preliminary Experiments

NASA Technical Reports Server (NTRS)

Swaminadham, M.; Hamilton, David A.

1994-01-01

This paper deals with the dynamic characterization of a flexible aerospace solar boom. The modeling issues and sine dwell vibration testing to determine natural frequencies and mode shapes of a continuous-longer on deployable ASTROMAST lattice boom are discussed. The details of the proof-of-concept piezoelectric active vibration experiments on a simple cantilever beam to control its vibrations are presented. The control parameters like voltage to the controller crystal and its location are investigated, to determine the effectiveness of control element to suppress selected resonant vibrations of the test specimen. Details of this experiment and plans for its future adaptation to the prototype structure are also discussed.

Experiment on the concrete slab for floor vibration evaluation of deteriorated building

NASA Astrophysics Data System (ADS)

Hong, S. U.; Na, J. H.; Kim, S. H.; Lee, Y. T.

2014-08-01

Damages from noise and vibration are increasing every year, and most of which are noises between floors in deteriorated building caused by floor impact sound. In this study, the floor vibration of the deteriorated buildings constructed with the concrete slabs of thickness no more than 150 mm was evaluated by the vibration impact sound. This highly reliable study was conducted to assess floor vibration according with the serviceability evaluation standard of Reiher / Meister and Koch and vibration evaluation standard of ISO and AIJ. Designed pressure for the concrete slab sample of floor vibration assessment was 24MPa, and the sample was manufactured pursuant to KS F 2865 and JIS A 1440-2 with size of 3200 mm × 3200 mm × 140 mm. Tests were conducted twice with accelerometers, and Fast Fourier Transform was performed for comparative analysis by the vibration assessment criteria. The peak displacement from Test 1 was in the range of 0.00869 - 0.02540 mm; the value of peak frequency ranged from 18 to 27 Hz, and the average value was 22Hz. The peak acceleration value from Test 2 was in the range of 0.47 - 1.07 % g; the value of peak frequency was 18.5 - 22.57 Hz, and the average was 21Hz. The vibration was apparently recognizable in most cases according to the Reiher/Meister standard. In case of Koch graph for the damage assessment of the structure, the vibration was at the medium level and causes no damage to the building structure. The measured vibration results did not exceed the damage limit or serviceability limit of building according to the vibration assessment criteria of ISO and residential assessment guidelines provided by Architectural Institute of Japan (AIJ).

16 CFR 1211.5 - General testing parameters.

Code of Federal Regulations, 2012 CFR

2012-01-01

... § 1211.4(c) for compliance with the Standard for Safety for Tests for Safety-Related Controls Employing... vibration level of 5g is to be used for the Vibration Test. (6) When a Computational Investigation is... tested. (8) The Endurance test is to be conducted concurrently with the Operational test. The control...

16 CFR § 1211.5 - General testing parameters.

Code of Federal Regulations, 2013 CFR

2013-01-01

... covered by § 1211.4(c) for compliance with the Standard for Safety for Tests for Safety-Related Controls... vibration level of 5g is to be used for the Vibration Test. (6) When a Computational Investigation is... tested. (8) The Endurance test is to be conducted concurrently with the Operational test. The control...

16 CFR 1211.5 - General testing parameters.

Code of Federal Regulations, 2011 CFR

2011-01-01

... § 1211.4(c) for compliance with the Standard for Safety for Tests for Safety-Related Controls Employing... vibration level of 5g is to be used for the Vibration Test. (6) When a Computational Investigation is... tested. (8) The Endurance test is to be conducted concurrently with the Operational test. The control...

16 CFR 1211.5 - General testing parameters.

Code of Federal Regulations, 2014 CFR

2014-01-01

... § 1211.4(c) for compliance with the Standard for Safety for Tests for Safety-Related Controls Employing... vibration level of 5g is to be used for the Vibration Test. (6) When a Computational Investigation is... tested. (8) The Endurance test is to be conducted concurrently with the Operational test. The control...

Positioning and Microvibration Control by Electromagnets of an Air Spring Vibration Isolation System

NASA Technical Reports Server (NTRS)

Watanabe, Katsuhide; Cui, Weimin; Haga, Takahide; Kanemitsu, Yoichi; Yano, Kenichi

1996-01-01

Active positioning and microvibration control has been attempted by electromagnets equipped in a bellows-type, air-spring vibration isolation system. Performance tests have been carried out to study the effects. The main components of the system's isolation table were four electromagnetic actuators and controllers. The vibration isolation table was also equipped with six acceleration sensors for detecting microvibration of the table. The electromagnetic actuators were equipped with bellows-type air springs for passive support of the weight of the item placed on the table, with electromagnets for active positioning, as well as for microvibration control, and relative displacement sensors. The controller constituted a relative feedback system for positioning control and an absolute feedback system for vibration isolation control. In the performance test, a 1,490 kg load (net weight of 1,820 kg) was placed on the vibration isolation table, and both the positioning and microvibration control were carried out electromagnetically. Test results revealed that the vibration transmission was reduced by 95%.

Concorde noise-induced building vibrations John F. Kennedy International Airport

NASA Technical Reports Server (NTRS)

Mayes, W. H.; Deloach, R.; Stephens, D. G.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.

1978-01-01

The outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded at six home sites along with the associated vibration levels in the walls, windows, and floors of these test homes. Limited subjective tests conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise showed that both vibration and rattle were detected subjectively in several houses for some operations of both the Concorde and subsonic aircraft. Preliminary results indicate that the relationship between window vibration and aircraft noise is: (1) linear, with vibration levels being accurately predicted from OASPL levels measured near the window; (2) consistent from flyover to flyover for a given aircraft type under approach conditions; (3) no different for Concorde than for other conventional jet transports (in the case of window vibrations induced under approach power conditions); and (4) relatively high levels of window vibration measured during Concorde operations are due more to higher OASPL levels than to unique Concorde source characteristics.

Vibrational response analysis of tires using a three-dimensional flexible ring-based model

NASA Astrophysics Data System (ADS)

Matsubara, Masami; Tajiri, Daiki; Ise, Tomohiko; Kawamura, Shozo

2017-11-01

Tire vibration characteristics influence noise, vibration, and harshness. Hence, there have been many investigations of the dynamic responses of tires. In this paper, we present new formulations for the prediction of tire tread vibrations below 150 Hz using a three-dimensional flexible ring-based model. The ring represents the tread including the belt, and the springs represent the tire sidewall stiffness. The equations of motion for lateral, longitudinal, and radial vibration on the tread are derived based on the assumption of inextensional deformation. Many of the associated numerical parameters are identified from experimental tests. Unlike most studies of flexible ring models, which mainly discussed radial and circumferential vibration, this study presents steady response functions concerning not only radial and circumferential but also lateral vibration using the three-dimensional flexible ring-based model. The results of impact tests described confirm the theoretical findings. The results show reasonable agreement with the predictions.

Comparison of vibrations of a combination of solid-rocket launch vehicle and payload during a ground firing and launching

NASA Technical Reports Server (NTRS)

Schoenster, J. A.; Pierce, H. B.

1975-01-01

The results of a study into the environmental vibrations of a payload mounted on the Nike rocket launch vehicle were presented. Data were obtained during the flight acceptance test of the payload, the firing of the total vehicle in a special test stand, and the powered and unpowered flights of the vehicle. The vibrational response of the structure was measured. Data were also obtained on the fluctuating pressure on the outside surface of the vehicle and inside the forward and after ends of the rocket chamber. A comparison of the data from the three test conditions indicated that external pressure fluctuations were the major source of vibrations in the payload area, and pressure fluctuations within the rocket motor were the major source of vibrations contiguous to the payload area.

Field Telemetry of Blade-rotor Coupled Torsional Vibration at Matuura Power Station Number 1 Unit

NASA Technical Reports Server (NTRS)

Isii, Kuniyoshi; Murakami, Hideaki; Otawara, Yasuhiko; Okabe, Akira

1991-01-01

The quasi-modal reduction technique and finite element model (FEM) were used to construct an analytical model for the blade-rotor coupled torsional vibration of a steam turbine generator of the Matuura Power Station. A single rotor test was executed in order to evaluate umbrella vibration characteristics. Based on the single rotor test results and the quasi-modal procedure, the total rotor system was analyzed to predict coupled torsional frequencies. Finally, field measurement of the vibration of the last stage buckets was made, which confirmed that the double synchronous resonance was 124.2 Hz, meaning that the machine can be safely operated. The measured eigen values are very close to the predicted value. The single rotor test and this analytical procedure thus proved to be a valid technique to estimate coupled torsional vibration.

Inficon Transpector MPH Mass Spectrometer Random Vibration Test Report

NASA Technical Reports Server (NTRS)

Santiago-Bond, Jo; Captain, Janine

2015-01-01

The purpose of this test report is to summarize results from the vibration testing of the INFICON Transpector MPH100M model Mass Spectrometer. It also identifies requirements satisfied, and procedures used in the test. As a payload of Resource Prospector, it is necessary to determine the survivability of the mass spectrometer to proto-qualification level random vibration. Changes in sensitivity of the mass spectrometer can be interpreted as a change in alignment of the instrument. The results of this test will be used to determine any necessary design changes as the team moves forward with flight design.

Deducing Electronic Unit Internal Response During a Vibration Test Using a Lumped Parameter Modeling Approach

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.

A new reference tip-timing test bench and simulator for blade synchronous and asynchronous vibrations

NASA Astrophysics Data System (ADS)

Hajnayeb, Ali; Nikpour, Masood; Moradi, Shapour; Rossi, Gianluca

2018-02-01

The blade tip-timing (BTT) measurement technique is at present the most promising technique for monitoring the blades of axial turbines and aircraft engines in operating conditions. It is generally used as an alternative to strain gauges in turbine testing. By conducting a comparison with the standard methods such as those based on strain gauges, one determines that the technique is not intrusive and does not require a complicated installation process. Despite its superiority to other methods, the experimental performance analysis of a new BTT method needs a test stand that includes a reference measurement system (e.g. strain gauges equipped with telemetry or other complex optical measurement systems, like rotating laser Doppler vibrometers). In this article, a new reliable, low-cost BTT test setup is proposed for simulating and analyzing blade vibrations based on kinematic inversion. In the proposed test bench, instead of the blades vibrating, it is the BTT sensor that vibrates. The vibration of the sensor is generated by a shaker and can therefore be easily controlled in terms of frequency, amplitude and waveform shape. The amplitude of vibration excitation is measured by a simple accelerometer. After introducing the components of the simulator, the proposed test bench is used in practice to simulate both synchronous and asynchronous vibration scenarios. Then two BTT methods are used to evaluate the quality of the acquired data. The results demonstrate that the proposed setup is able to generate simulated pulse sequences which are almost the same as those generated by the conventional BTT systems installed around a bladed disk. Moreover, the test setup enables its users to evaluate BTT methods by using a limited number of sensors. This significantly reduces the total costs of the experiments.

A Method for Implementing Force-Limited Vibration Control

NASA Technical Reports Server (NTRS)

Worth, Daniel B.

1997-01-01

NASA/GSFC has implemented force-limited vibration control on a controller which can only accept one profile. The method uses a personal computer based digital signal processing board to convert force and/or moment signals into what appears to he an acceleration signal to the controller. This technique allows test centers with older controllers to use the latest force-limited control techniques for random vibration testing. The paper describes the method, hardware, and test procedures used. An example from a test performed at NASA/GSFC is used as a guide.

National Transonic Facility model and model support vibration problems

NASA Technical Reports Server (NTRS)

Young, Clarence P., Jr.; Popernack, Thomas G., Jr.; Gloss, Blair B.

1990-01-01

Vibrations of models and model support system were encountered during testing in the National Transonic Facility. Model support system yaw plane vibrations have resulted in model strain gage balance design load limits being reached. These high levels of vibrations resulted in limited aerodynamic testing for several wind tunnel models. The yaw vibration problem was the subject of an intensive experimental and analytical investigation which identified the primary source of the yaw excitation and resulted in attenuation of the yaw oscillations to acceptable levels. This paper presents the principal results of analyses and experimental investigation of the yaw plane vibration problems. Also, an overview of plans for development and installation of a permanent model system dynamic and aeroelastic response measurement and monitoring system for the National Transonic Facility is presented.

Impact of vibration and agitation speed on dissolution of USP prednisone tablets RS and various IR tablet formulations.

PubMed

Seeger, Nicole; Lange, Sigrid; Klein, Sandra

2015-08-01

Dissolution testing is an in vitro procedure which is widely used in quality control (QC) of solid oral dosage forms and, given that real biorelevant test conditions are applied, can also be used as a predictive tool for the in vivo performance of such formulations. However, if a dissolution method is intended to be used for such purposes, it has to deliver results that are only determined by the quality of the test product, but not by other variables. In the recent past, more and more questions were arising on how to address the effects of vibration on dissolution test results. The present study was performed to screen for the correlation of prednisone dissolution of USP Prednisone Tablets RS with vibration caused by a commercially available vibration source as well as to investigate how drug release from a range of immediate release formulations containing class 1-4 drugs of the biopharmaceutical classification scheme is affected by vibration when performing dissolution experiments at different agitation rates. Results of the present study show that the dissolution process of oral drug formulations can be affected by vibration. However, it also becomes clear that the degree of which a certain level of vibration impacts dissolution is strongly dependent on several factors such as drug properties, formulation parameters, and the design of the dissolution method. To ensure the establishment of robust and predictive dissolution test methods, the impact of variation should thus be considered in method design and validation.

Application of higher harmonic blade feathering on the OH-6A helicopter for vibration reduction

NASA Technical Reports Server (NTRS)

Straub, F. K.; Byrns, E. V., Jr.

1986-01-01

The design, implementation, and flight test results of higher harmonic blade feathering for vibration reduction on the OH-6A helicopter are described. The higher harmonic control (HHC) system superimposes fourth harmonic inputs upon the stationary swashplate. These inputs are transformed into 3P, 4P and 5P blade feathering angles. This results in modified blade loads and reduced fuselage vibrations. The primary elements of this adaptive vibration suppression system are: (1) acceleration transducers sensing the vibratory response of the fuselage; (2) a higher harmonic blade pitch actuator system; (3) a flightworthy microcomputer, incorporating the algorithm for reducing vibrations, and (4) a signal conditioning system, interfacing between the sensors, the microcomputer and the HHC actuators. The program consisted of three distinct phases. First, the HHC system was designed and implemented on the MDHC OH-6A helicopter. Then, the open loop, or manual controlled, flight tests were performed, and finally, the closed loop adaptive control system was tested. In 1983, one portion of the closed loop testing was performed, and in 1984, additional closed loop tests were conducted with improved software. With the HHC system engaged, the 4P pilot seat vibration levels were significantly lower than the baseline ON-6A levels. Moreover, the system did not adversely affect blade loads or helicopter performance. In conclusion, this successful proof of concept project demonstrated HHC to be a viable vibration suppression mechanism.

The Efficacy of Anti-vibration Gloves

PubMed Central

Hewitt, Sue; Dong, Ren; McDowell, Tom; Welcome, Daniel

2016-01-01

Anyone seeking to control the risks from vibration transmitted to the hands and arms may contemplate the use of anti-vibration gloves. To make an informed decision about any type of personal protective equipment, it is necessary to have performance data that allow the degree of protection to be estimated. The information provided with an anti-vibration glove may not be easy to understand without some background knowledge of how gloves are tested and does not provide any clear route for estimating likely protection. Some of the factors that influence the potential efficacy of an anti-vibration glove include how risks from hand–arm vibration exposure are assessed, how the standard test for a glove is carried out, the frequency range and direction of the vibration for which protection is sought, how much hand contact force or pressure is applied and the physical limitations due to glove material and construction. This paper reviews some of the background issues that are useful for potential purchasers of anti-vibration gloves. Ultimately, anti-vibration gloves cannot be relied on to provide sufficient and consistent protection to the wearer and before their use is contemplated all other available means of vibration control ought first to be implemented. PMID:27582615

Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

NASA Technical Reports Server (NTRS)

Dervan, Jared; Robertson, Brandon; Staab, Lucas; Culberson, Michael

2014-01-01

Commodities are transferred between the Multi-Purpose Crew Vehicle (MPCV) crew module (CM) and service module (SM) via an external umbilical that is driven apart with spring-loaded struts after the structural connection is severed. The spring struts must operate correctly for the modules to separate safely. There was no vibration testing of strut development units scoped in the MPCV Program Plan; therefore, any design problems discovered as a result of vibration testing would not have been found until the component qualification. The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations including identified lessons learned and best practices to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

Active vibration control for flexible rotor by optimal direct-output feedback control

NASA Technical Reports Server (NTRS)

Nonami, Kenzou; Dirusso, Eliseo; Fleming, David P.

1989-01-01

Experimental research tests were performed to actively control the rotor vibrations of a flexible rotor mounted on flexible bearing supports. The active control method used in the tests is called optimal direct-output feedback control. This method uses four electrodynamic actuators to apply control forces directly to the bearing housings in order to achieve effective vibration control of the rotor. The force actuators are controlled by an analog controller that accepts rotor displacement as input. The controller is programmed with experimentally determined feedback coefficients; the output is a control signal to the force actuators. The tests showed that this active control method reduced the rotor resonance peaks due to unbalance from approximately 250 micrometers down to approximately 25 micrometers (essentially runout level). The tests were conducted over a speed range from 0 to 10,000 rpm; the rotor system had nine critical speeds within this speed range. The method was effective in significantly reducing the rotor vibration for all of the vibration modes and critical speeds.

Active vibration control for flexible rotor by optimal direct-output feedback control

NASA Technical Reports Server (NTRS)

Nonami, K.; Dirusso, E.; Fleming, D. P.

1989-01-01

Experimental research tests were performed to actively control the rotor vibrations of a flexible rotor mounted on flexible bearing supports. The active control method used in the tests is called optimal direct-output feedback control. This method uses four electrodynamic actuators to apply control forces directly to the bearing housings in order to achieve effective vibration control of the rotor. The force actuators are controlled by an analog controller that accepts rotor displacement as input. The controller is programmed with experimentally determined feedback coefficients; the output is a control signal to the force actuators. The tests showed that this active control method reduced the rotor resonance peaks due to unbalance from approximately 250 microns down to approximately 25 microns (essentially runout level). The tests were conducted over a speed range from 0 to 10,000 rpm; the rotor system had nine critical speeds within this speed range. The method was effective in significantly reducing the rotor vibration for all of the vibration modes and critical speeds.

Vibration and Acoustic Testing for Mars Micromission Spacecraft

NASA Technical Reports Server (NTRS)

Kern, Dennis L.; Scharton, Terry D.

1999-01-01

The objective of the Mars Micromission program being managed by the Jet Propulsion Laboratory (JPL) for NASA is to develop a common spacecraft that can carry telecommunications equipment and a variety of science payloads for exploration of Mars. The spacecraft will be capable of carrying robot landers and rovers, cameras, probes, balloons, gliders or aircraft, and telecommunications equipment to Mars at much lower cost than recent NASA Mars missions. The lightweight spacecraft (about 220 Kg mass) will be launched in a cooperative venture with CNES as a TWIN auxiliary payload on the Ariane 5 launch vehicle. Two or more Mars Micromission launches are planned for each Mars launch opportunity, which occur every 26 months. The Mars launch window for the first mission is November 1, 2002 through April 2003, which is planned to be a Mars airplane technology demonstration mission to coincide with the 100 year anniversary of the Kittyhawk flight. Several subsequent launches will create a telecommunications network orbiting Mars, which will provide for continuous communication with lenders and rovers on the Martian surface. Dedicated science payload flights to Mars are slated to start in 2005. This new cheaper and faster approach to Mars exploration calls for innovative approaches to the qualification of the Mars Micromission spacecraft for the Ariane 5 launch vibration and acoustic environments. JPL has in recent years implemented new approaches to spacecraft testing that may be effectively applied to the Mars Micromission. These include 1) force limited vibration testing, 2) combined loads, vibration and modal testing, and 3) direct acoustic testing. JPL has performed nearly 200 force limited vibration tests in the past 9 years; several of the tests were on spacecraft and large instruments, including the Cassini and Deep Space One spacecraft. Force limiting, which measures and limits the spacecraft base reaction force using triaxial force gages sandwiched between the spacecraft and the test fixture, alleviates the severe overtest at spacecraft resonances inherent in rigid fixture vibration tests. It has the distinct advantage over response limiting that the method is not dependent on the accuracy of a detailed dynamic model of the spacecraft. Combined loads, vibration, and modal testing were recently performed on the QuikSCAT spacecraft. The combined tests were performed in a single test setup per axis on a vibration shaker, reducing test time by a factor of two or three. Force gages were employed to measure the true c.g. acceleration of the spacecraft for structural loads verification using a sine burst test, to automatically notch random vibration test input accelerations at spacecraft resonances based on predetermined force limits, and to directly measure modal masses in a base drive modal test. In addition to these combined tests on the shaker, the QuikSCAT spacecraft was subjected to a direct field acoustic test by surrounding the spacecraft, still on the vibration shaker, with rock concert type acoustic speakers. Since the spacecraft contractor does not have a reverberant field acoustic test facility, performing a direct field acoustic test -saved the program nearly two weeks schedule time that would have been required for packing / unpacking and shipping of the spacecraft. This paper discusses the rationale behind and advantages of the above test approaches and provides examples of their actual implementation and comparisons to flight data. The applicability of the test approaches to Mars Micromission spacecraft qualification is discussed.

Disk Crack Detection for Seeded Fault Engine Test

NASA Technical Reports Server (NTRS)

Luo, Huageng; Rodriguez, Hector; Hallman, Darren; Corbly, Dennis; Lewicki, David G. (Technical Monitor)

2004-01-01

Work was performed to develop and demonstrate vibration diagnostic techniques for the on-line detection of engine rotor disk cracks and other anomalies through a real engine test. An existing single-degree-of-freedom non-resonance-based vibration algorithm was extended to a multi-degree-of-freedom model. In addition, a resonance-based algorithm was also proposed for the case of one or more resonances. The algorithms were integrated into a diagnostic system using state-of-the- art commercial analysis equipment. The system required only non-rotating vibration signals, such as accelerometers and proximity probes, and the rotor shaft 1/rev signal to conduct the health monitoring. Before the engine test, the integrated system was tested in the laboratory by using a small rotor with controlled mass unbalances. The laboratory tests verified the system integration and both the non-resonance and the resonance-based algorithm implementations. In the engine test, the system concluded that after two weeks of cycling, the seeded fan disk flaw did not propagate to a large enough size to be detected by changes in the synchronous vibration. The unbalance induced by mass shifting during the start up and coast down was still the dominant response in the synchronous vibration.

A procedure obtaining stiffnesses and masses of a structure from vibration modes and substructure static test data

NASA Technical Reports Server (NTRS)

Edighoffer, H. H.

1979-01-01

A component mode desynthesis procedure is developed for determining the unknown vibration characteristics of a structural component (i.e., a launch vehicle) given the vibration characteristics of a structural system composed of that component combined with a known one (i.e., a payload). At least one component static test has to be performed. These data are used in conjunction with the system measured frequencies and mode shapes to obtain the vibration characteristics of each component. The flight dynamics of an empty launch vehicle can be determined from measurements made on a vehicle/payload combination in conjunction with a static test on the payload.

Hologram interferometry in automotive component vibration testing

NASA Astrophysics Data System (ADS)

Brown, Gordon M.; Forbes, Jamie W.; Marchi, Mitchell M.; Wales, Raymond R.

1993-02-01

An ever increasing variety of automotive component vibration testing is being pursued at Ford Motor Company, U.S.A. The driving force for use of hologram interferometry in these tests is the continuing need to design component structures to meet more stringent functional performance criteria. Parameters such as noise and vibration, sound quality, and reliability must be optimized for the lightest weight component possible. Continually increasing customer expectations and regulatory pressures on fuel economy and safety mandate that vehicles be built from highly optimized components. This paper includes applications of holographic interferometry for powertrain support structure tuning, body panel noise reduction, wiper system noise and vibration path analysis, and other vehicle component studies.

A novel vibration sensor based on phase grating interferometry

NASA Astrophysics Data System (ADS)

Li, Qian; Liu, Xiaojun; Zhao, Li; Lei, Zili; Lu, Zhen; Guo, Lei

2017-05-01

Vibration sensors with high accuracy and reliability are needed urgently for vibration measurement. In this paper a vibration sensor with nanometer resolution is developed. This sensor is based on the principle of phase grating interference for displacement measurement and spatial polarization phase-shift interference technology, and photoelectric counting and A/D signal subdivision are adopted for vibration data output. A vibration measurement system consisting of vibration actuator and displacement adjusting device has been designed to test the vibration sensor. The high resolution and high reliability of the sensor are verified through a series of comparison experiments with Doppler interferometer.

Transducer senses displacements of panels subjected to vibration

NASA Technical Reports Server (NTRS)

Pea, R. O.

1965-01-01

Inductive vibration sensor measures the surface displacement of nonferrous metal panels subjected to vibration or flutter. This transducer does not make any physical contact with the test panel when measuring.

A novel approach for simulating the optical misalignment caused by satellite platform vibration in the ground test of satellite optical communication systems.

PubMed

Wang, Qiang; Tan, Liying; Ma, Jing; Yu, Siyuan; Jiang, Yijun

2012-01-16

Satellite platform vibration causes the misalignment between incident direction of the beacon and optical axis of the satellite optical communication system, which also leads to the instability of the laser link and reduces the precision of the system. So how to simulate the satellite platform vibration is a very important work in the ground test of satellite optical communication systems. In general, a vibration device is used for simulating the satellite platform vibration, but the simulation effect is not ideal because of the limited randomness. An approach is reasonable, which uses a natural random process for simulating the satellite platform vibration. In this paper, we discuss feasibility of the concept that the effect of angle of arrival fluctuation is taken as an effective simulation of satellite platform vibration in the ground test of the satellite optical communication system. Spectrum characteristic of satellite platform vibration is introduced, referring to the model used by the European Space Agency (ESA) in the SILEX program and that given by National Aeronautics and Space Development Agency (NASDA) of Japan. Spectrum characteristic of angle of arrival fluctuation is analyzed based on the measured data from an 11.16km bi-directional free space laser transmission experiment. Spectrum characteristic of these two effects is compared. The results show that spectra of these two effects have similar variation trend with the variation of frequency and feasibility of the concept is proved by the comparison results. At last the procedure of this method is proposed, which uses the power spectra of angle of arrival fluctuation to simulate that of the satellite platform vibration. The new approach is good for the ground test of satellite optical communication systems.

Principal Components Analysis of Triaxial Vibration Data From Helicopter Transmissions

NASA Technical Reports Server (NTRS)

Tumer, Irem Y.; Huff, Edward M.

2001-01-01

Research on the nature of the vibration data collected from helicopter transmissions during flight experiments has led to several crucial observations believed to be responsible for the high rates of false alarms and missed detections in aircraft vibration monitoring systems. This work focuses on one such finding, namely, the need to consider additional sources of information about system vibrations. In this light, helicopter transmission vibration data, collected using triaxial accelerometers, were explored in three different directions, analyzed for content, and then combined using Principal Components Analysis (PCA) to analyze changes in directionality. In this paper, the PCA transformation is applied to 176 test conditions/data sets collected from an OH58C helicopter to derive the overall experiment-wide covariance matrix and its principal eigenvectors. The experiment-wide eigenvectors. are then projected onto the individual test conditions to evaluate changes and similarities in their directionality based on the various experimental factors. The paper will present the foundations of the proposed approach, addressing the question of whether experiment-wide eigenvectors accurately model the vibration modes in individual test conditions. The results will further determine the value of using directionality and triaxial accelerometers for vibration monitoring and anomaly detection.

Vibration Considerations for Cryogenic Tanks Using Glass Bubbles Insulation

NASA Technical Reports Server (NTRS)

Werlink, Rudolph J.; Fesmire, James E.; Sass, Jared P.

2011-01-01

The use of glass bubbles as an efficient and practical thermal insulation system has been previously demonstrated in cryogenic storage tanks. One such example is a spherical, vacuum-jacketed liquid hydrogen vessel of 218,000 liter capacity where the boiloff rate has been reduced by approximately 50 percent. Further applications may include non-stationary tanks such as mobile tankers and tanks with extreme duty cycles or exposed to significant vibration environments. Space rocket launch events and mobile tanker life cycles represent two harsh cases of mechanical vibration exposure. A number of bulk fill insulation materials including glass bubbles, perlite powders, and aerogel granules were tested for vibration effects and mechanical behavior using a custom design holding fixture subjected to random vibration on an Electrodynamic Shaker. The settling effects for mixtures of insulation materials were also investigated. The vibration test results and granular particle analysis are presented with considerations and implications for future cryogenic tank applications. A thermal performance update on field demonstration testing of a 218,000 L liquid hydrogen storage tank, retrofitted with glass bubbles, is presented. KEYWORDS: Glass bubble, perlite, aerogel, insulation, liquid hydrogen, storage tank, mobile tanker, vibration.

Piezoelectric pushers for active vibration control of rotating machinery

NASA Technical Reports Server (NTRS)

Palazzolo, Alan B.; Kascak, Albert F.

1988-01-01

The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers have been discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Tests are currently being conducted with piezoelectric pusher-based active vibration control. Results from tests performed on NASA test rigs as preliminary verification of the related theory are presented.

Piezoelectric pushers for active vibration control of rotating machinery

NASA Technical Reports Server (NTRS)

Palazzolo, A. B.; Lin, R. R.; Alexander, R. M.; Kascak, A. F.; Montague, J.

1989-01-01

The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers have been discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Tests are currently being conducted with piezoelectric pusher-based active vibration control. Results from tests performed on NASA test rigs as preliminary verification of the related theory are presented.

Portable vibration exciter

NASA Technical Reports Server (NTRS)

Beecher, L. C.; Williams, F. T.

1970-01-01

Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

Health Monitoring System for Composite Structures

NASA Technical Reports Server (NTRS)

Tang, S. S.; Riccardella, P. C.; Andrews, R. J.; Grady, J. E.; Mucciaradi, A. N.

1996-01-01

An automated system was developed to monitor the health status of composites. It uses the vibration characteristics of composites to identify a component's damage condition. The vibration responses are characterized by a set of signal features defined in the time, frequency and spatial domains. The identification of these changes in the vibration characteristics corresponding to different health conditions was performed using pattern recognition principles. This allows efficient data reduction and interpretation of vast amounts of information. Test components were manufactured from isogrid panels to evaluate performance of the monitoring system. The components were damaged by impact to simulate different health conditions. Free vibration response was induced by a tap test on the test components. The monitoring system was trained using these free vibration responses to identify three different health conditions. They are undamaged vs. damaged, damage location and damage zone size. High reliability in identifying the correct component health condition was achieved by the monitoring system.

Miniature Long-life Space Cryocoolers

NASA Technical Reports Server (NTRS)

Tward, E.

1993-01-01

TRW has designed, built, and tested a miniature integral Stirling cooler and a miniature pulse tube cooler intended for long-life space application. Both efficient, low-vibration coolers were developed for cooling IR sensors to temperatures as low as 50 K on lightsats. The vibrationally balanced nonwearing design Stirling cooler incorporates clearance seals maintained by flexure springs for both the compressor and the drive displacer. The design achieved its performance goal of 0.25 W at 65 K for an input power to the compressor of 12 W. The cooler recently passed launch vibration tests prior to its entry into an extended life test and its first scheduled flight in 1995. The vibrationally balanced, miniature pulse tube cooler intended for a 10-year long-life space application incorporates a flexure bearing compressor vibrationally balanced by a motor-controlled balancer and a completely passive pulse tube cold head.

Towards identifying the dynamics of sliding by acoustic emission and vibration

NASA Astrophysics Data System (ADS)

Korchuganov, M. A.; Filippov, A. V.; Tarasov, S. Yu.; Podgornyh, O. A.; Shamarin, N. N.; Filippova, E. O.

2016-11-01

The results of experiments with high load and sliding speed sliding conditions on tribologically mated pairs such as steel 1045/steel 1045 (test 1), steel 1045/basalt (test 2) and Hadfield steel/basalt (test 3) have been carried out in order to identify their response in terms of the acoustic emission and vibration signals. The steel to rock and rock to steel transfer has been revealed by examining the worn surfaces of both steel and rock samples with the use of laser scanning microscopy. The AE signal characteristics have been determined for the tribological pairs studied. The dynamics of sliding has been evaluated by measuring the vibration accelerations. Relationship between wear mode and either acoustic emission signal or vibration signal has been established. The minimal vibration oscillations amplitude and acoustic emission signal energy have been found out in sliding Hadfield steel/basalt pair.

Quantifying and managing uncertainty in operational modal analysis

NASA Astrophysics Data System (ADS)

Au, Siu-Kui; Brownjohn, James M. W.; Mottershead, John E.

2018-03-01

Operational modal analysis aims at identifying the modal properties (natural frequency, damping, etc.) of a structure using only the (output) vibration response measured under ambient conditions. Highly economical and feasible, it is becoming a common practice in full-scale vibration testing. In the absence of (input) loading information, however, the modal properties have significantly higher uncertainty than their counterparts identified from free or forced vibration (known input) tests. Mastering the relationship between identification uncertainty and test configuration is of great interest to both scientists and engineers, e.g., for achievable precision limits and test planning/budgeting. Addressing this challenge beyond the current state-of-the-art that are mostly concerned with identification algorithms, this work obtains closed form analytical expressions for the identification uncertainty (variance) of modal parameters that fundamentally explains the effect of test configuration. Collectively referred as 'uncertainty laws', these expressions are asymptotically correct for well-separated modes, small damping and long data; and are applicable under non-asymptotic situations. They provide a scientific basis for planning and standardization of ambient vibration tests, where factors such as channel noise, sensor number and location can be quantitatively accounted for. The work is reported comprehensively with verification through synthetic and experimental data (laboratory and field), scientific implications and practical guidelines for planning ambient vibration tests.

VIBRATION TESTING OF RESILIENT PACKAGE CUSHIONING MATERIALS

DTIC Science & Technology

government and industry. Testing equipment which meets tentative ASTM requirements was developed. Preliminary tests were conducted on a resilient expanded ... polystyrene foam (in 3 densities) and a polyether urethane foam (in one density). When vibrated under static loads known to provide optimum shock

Evaluating the effectiveness of gloves in reducing the hazards of hand-transmitted vibration.

PubMed

Griffin, M J

1998-05-01

A method of evaluating the effectiveness of gloves in reducing the hazards of hand-transmitted vibration is proposed. The glove isolation effectiveness was calculated from: (a) the measured transmissibility of a glove, (b) the vibration spectrum on the handle of a specific tool (or class of tools), and (c) the frequency weighting indicating the degree to which different frequencies of vibration cause injury. With previously reported tool vibration spectra and glove transmissibilities (from 10-1000 Hz), the method was used to test 10 gloves with 20 different powered tools. The frequency weighting for hand-transmitted vibration advocated in British standard 6842 (1987) and international standard 5349 (1986) greatly influences the apparent isolation effectiveness of gloves. With the frequency weighting, the gloves had little effect on the transmission of vibration to the hand from most of the tools. Only for two or three tools (those dominated by high frequency vibration) did any glove provide useful attenuation. Without the frequency weighting, some gloves showed useful attenuation of the vibration on most powered tools. In view of the uncertain effect of the vibration frequency in the causation of disorders from hand-transmitted vibration, it is provisionally suggested that the wearing of a glove by the user of a particular vibratory tool could be encouraged if the glove reduces the transmission of vibration when it is evaluated without the frequency weighting and does not increase the vibration when it is evaluated with the frequency weighting. A current international standard for the measurement and evaluation of the vibration transmitted by gloves can classify a glove as an antivibration glove when it provides no useful attenuation of vibration, whereas a glove providing useful attenuation of vibration on a specific tool can fail the test.

Vibration Tests on Transit Buses

DOT National Transportation Integrated Search

1979-03-01

The objective of this vibration measurement program was to quantify the vibration environment which would be experienced by Automatic Vehicle Monitoring (AVM) equipment when installed on buses during typical city route service operations. Two buses w...

Modal simulation of gearbox vibration with experimental correlation

NASA Technical Reports Server (NTRS)

Choy, Fred K.; Ruan, Yeefeng F.; Zakrajsek, James J.; Oswald, Fred B.

1992-01-01

A newly developed global dynamic model was used to simulate the dynamics of a gear noise rig at NASA Lewis Research Center. Experimental results from the test rig were used to verify the analytical model. In this global dynamic model, the number of degrees of freedom of the system are reduced by transforming the system equations of motion into modal coordinates. The vibration of the individual gear-shaft system are coupled through the gear mesh forces. A three-dimensional, axial-lateral coupled, bearing model was used to couple the casing structural vibration to the gear-rotor dynamics. The coupled system of modal equations is solved to predict the resulting vibration at several locations on the test rig. Experimental vibration data was compared to the predictions of the global dynamic model. There is excellent agreement between the vibration results from analysis and experiment.

Synthesis of Sine-on-Random vibration profiles for accelerated life tests based on fatigue damage spectrum equivalence

NASA Astrophysics Data System (ADS)

Angeli, Andrea; Cornelis, Bram; Troncossi, Marco

2018-03-01

In many real life environments, mechanical and electronic systems are subjected to vibrations that may induce dynamic loads and potentially lead to an early failure due to fatigue damage. Thus, qualification tests by means of shakers are advisable for the most critical components in order to verify their durability throughout the entire life cycle. Nowadays the trend is to tailor the qualification tests according to the specific application of the tested component, considering the measured field data as reference to set up the experimental campaign, for example through the so called "Mission Synthesis" methodology. One of the main issues is to define the excitation profiles for the tests, that must have, besides the (potentially scaled) frequency content, also the same damage potential of the field data despite being applied for a limited duration. With this target, the current procedures generally provide the test profile as a stationary random vibration specified by a Power Spectral Density (PSD). In certain applications this output may prove inadequate to represent the nature of the reference signal, and the procedure could result in an unrealistic qualification test. For instance when a rotating part is present in the system the component under analysis may be subjected to Sine-on-Random (SoR) vibrations, namely excitations composed of sinusoidal contributions superimposed to random vibrations. In this case, the synthesized test profile should preserve not only the induced fatigue damage but also the deterministic components of the environmental vibration. In this work, the potential advantages of a novel procedure to synthesize SoR profiles instead of PSDs for qualification tests are presented and supported by the results of an experimental campaign.

Effects of a single session of whole body vibration on ankle plantarflexion spasticity and gait performance in patients with chronic stroke: a randomized controlled trial.

PubMed

Chan, Kwan-Shan; Liu, Chin-Wei; Chen, Tien-Wen; Weng, Ming-Cheng; Huang, Mao-Hsiung; Chen, Chia-Hsin

2012-12-01

To investigate the effects of a single session of whole body vibration training on ankle plantarflexion spasticity and gait performance in chronic stroke patients. Randomized controlled trial. Rehabilitation unit in university hospital. Thirty subjects with chronic stroke were randomized into either a control group (n = 15) or a group receiving a single session of whole body vibration (n = 15). The intervention group was actually treated with whole body vibration while the control group was treated with placebo treatment. The spastic changes were measured clinically and neurophysiologically. Subjective evaluation of ankle spasticity was performed via a visual analogue scale. Gait performances were evaluated by the timed up and go test, 10-meter walk test and cadence. A forceplate was used for measuring foot pressure. The changes between whole body vibration and control groups were significantly different in Modified Ashworth Scale (1.33, 95% confidence interval (CI) = 1.06~1.60). The H (max)/M (max) ratio (0.14, 95% CI = 0.01~0.26) and visual analogue scale (1.87, 95% CI = 1.15~2.58) were significantly decreased. Whole body vibration could significantly improve gait velocity, timed up and go test (6.03, 95% CI = 3.17~8.89) and 10-meter walk test (1.99, 95% CI = 0.11~3.87). The uneven body weight posture on bilateral feet was also improved after vibration. These results suggest that a single session of whole body vibration training can reduce ankle plantarflexion spasticity in chronic stroke patients, thereby potentially increasing ambulatory capacity.

Whole body vibration in helicopters: risk assessment in relation to low back pain.

PubMed

Kåsin, Jan Ivar; Mansfield, Neil; Wagstaff, Anthony

2011-08-01

Helicopter pilots are exposed to whole body vibration (WBV) in their working environment. WBV has been associated with low back pain (LBP) and helicopter pilots have a high prevalence for LBP compared with other professions. The aim of this study was to develop a test protocol for measuring helicopters with ISO 2631-1 and to perform a whole body vibration risk assessment based on the European Vibration Directive in a number of commonly used military and civilian helicopters. Both absolute values and individual difference in current helicopter types are of interest in order to evaluate the possible role of vibration in LBP in helicopter pilots. In operationally relevant maneuvers, six helicopters were tested. In order to standardize measurements, each continuous flight was split into 15 separate maneuvers. A model of a working day exposure pattern was used to calculate A(8) vibration magnitudes for each helicopter. The vibration A(8) exposure estimates ranged from 0.32-0.51 m x s(-2) during an 8-h working day A(8). This compares with EU and ISO lower bounds risk criteria of 0.5 and 0.43 m x s(-2) A(8), respectively. Despite the vibration levels being relatively low, helicopter pilots report a high incidence of LBP. It is possible that helicopter pilot postures increase the risk of LBP when combined with WBV. The test protocol used in this study could be generally applied for other rotary winged aircraft testing to allow for comparison of WBV results. Data from different flight phases could be used to model different exposure profiles.

Characterization of vibration transfer paths in nose gearboxes of an AH-64 Apache

NASA Astrophysics Data System (ADS)

Islam, A. K. M. Anwarul; Dempsey, Paula J.; Feldman, Jason; Larsen, Chris

2014-03-01

Health monitoring of rotorcraft components, which is currently being performed by Health and Usage Monitoring Systems (HUMS) through analyzing vibration signatures of dynamic mechanical components, is very important for their safe and economic operation. Vibration diagnostic algorithms in HUMS analyze vibration signatures associated with faults and quantify them as condition indicators (CI) to predict component behavior. Vibration transfer paths (VTP) play important roles in CI response and are characterized by frequency response functions (FRF) derived from vibration signatures of dynamic mechanical components of a helicopter. With an objective to investigate the difference in VTP of a component in a helicopter and test stand, and to relate that to the CI response, VTP measurements were recorded from 0-50 kHz under similar conditions in the left and right nose gearboxes (NGBs) of an AH-64 Apache and an isolated left NGB in a test stand at NASA Glenn Research Center. The test fixture enabled the application of measured torques - common during an actual operation. Commercial and lab piezo shakers, and an impact hammer were used in both systems to collect the vibration response using two types of commercially available accelerometers under various test conditions. The FRFs of both systems were found to be consistent, and certain real-world installation and maintenance issues, such as sensor alignments, locations and installation torques, had minimal effect on the VTP. However, gear vibration transfer path dynamics appeared to be somewhat dependent on presence of oil, and the lightly-damped ring gear produced sharp and closer transfer path resonances.

Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects

NASA Technical Reports Server (NTRS)

Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.

2011-01-01

Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.

Dynamic (Vibration) Testing: Design-Certification of Aerospace System

NASA Technical Reports Server (NTRS)

Aggarwal, Pravin K.

2010-01-01

Various types of dynamic testing of structures for certification purposes are described, including vibration, shock and acoustic testing. Modal testing is discussed as it frequently complements dynamic testing and is part of the structural verification/validation process leading up to design certification. Examples of dynamic and modal testing are presented as well as the common practices, procedures and standards employed.

Interethnic differences at the thermometric response to cold test: functional disorders of blood circulation in hand fingers and exposure to hand-arm vibration.

PubMed

Riolfi, A; Princivalle, A; Romeo, L; Caramaschi, P; Perbellini, L

2008-02-01

To report some notable aspects regarding thermometric response to cold test in black African subjects compared with Caucasians: both groups comprised persons exposed to hand-arm vibration and controls. An overall sample of 48 workers was examined in order to study their blood circulation in hand fingers: a control group of 12 healthy Caucasian workers never exposed before to hand-arm vibration; 12 Caucasian workers exposed for several years to vibrating tools and affected by occupational Raynaud's phenomenon; 12 healthy black African workers exposed to hand-arm vibration for almost 3 years; and 12 healthy black African workers never exposed to hand-arm vibration. Computerized skin thermometry was performed and thermometric curves were analyzed according to thermometric interpretation criteria such as the area-over-curve (AOC), the fifth minute of recovery/baseline temperature ratio (5REC/BT) and the temperature at the tenth minute of recovery (10REC) after cold test. Thermometric parameters in Caucasian subjects confirmed the basis of the existing literature in controls (basal finger temperature higher than 32 degrees C and complete recovery to the initial temperature after the cold test) and also in patients with Raynaud's phenomenon (basal temperature often lower than control subjects and slow recovery of finger temperature after cold test). Statistically significant difference was found between healthy Caucasians and healthy black subjects in all the parameters tested: healthy black subjects showed values of AOC and 10REC suggesting almost constantly lower finger temperatures during the thermometry test. Black people, both exposed and non-exposed to hand-arm vibration showed thermometric parameters suggesting poor blood microcirculation, which seems even poorer than in Caucasian people complaining Raynaud's phenomenon. Our chronothermometric tests suggest some significant interethnic differences in peripheral microcirculation, which seems rather poor in black African subjects in comparison with Caucasians.

Understanding of the Dynamics of the Stirling Convertor Advanced by Structural Testing

NASA Technical Reports Server (NTRS)

Hughes, William O.

2003-01-01

The NASA Glenn Research Center, the U.S. Department of Energy, and the Stirling Technology Company (STC) are developing a highly efficient, long-life, free-piston Stirling convertor for use as an advanced spacecraft power system for future NASA missions, including deep-space and Mars surface applications. As part of this development, four structural dynamic test programs were recently performed on Stirling Technology Demonstration Convertors (TDC's) that were designed and built by STC under contract to the Department of Energy. This testing was performed in Glenn's Structural Dynamics Laboratory and Microgravity Emissions Laboratory. The first test program, in November and December 1999, demonstrated that the Stirling TDC could withstand the harsh random vibration experienced during a typical spacecraft launch and survive with no structural damage or functional power performance degradation. This was a critical step in enabling the use of Stirling convertors for future spacecraft power systems. The most severe test was a 12.3grms random vibration test, with test durations of 3 min per axis. The random vibration test levels were chosen to simulate, with margin, the maximum anticipated launch vibration conditions. The Microgravity Emissions Laboratory is typically used to measure the dynamics produced by operating space experiments and the resulting impact to the International Space Station's microgravity environment. For the second Stirling dynamic test program, performed in January 2001, the Microgravity Emissions Laboratory was used to characterize the structure-borne disturbances produced by the normal operation of a pair of Stirling convertors. The forces and moments produced by the normal operation of a Stirling system must be recognized and controlled, if necessary, so that other nearby spacecraft components, such as cameras, are not adversely affected. The Stirling convertor pair emitted relatively benign tonal forces at its operational frequency and associated harmonics. Therefore, Stirling power systems will not disturb spacecraft science experiments if minimal appropriate mounting efforts are made. The third test program, performed in February and May 2001, resulted in a modal characterization of a Stirling convertor. Since the deflection of the TDC piston rod, under vibration excitation, was of particular interest, the outer pressure shell was removed to allow access to the rod. Through this testing, the Stirling TDC's natural frequencies and modes were identified. This knowledge advanced our understanding of the successful 1999 vibration test and may be utilized to optimize the output power of future Stirling designs. The fourth test program, in April 2001, was conducted to characterize the structural response of a pair of Stirling convertors, as a function of their mounting interface stiffness. The test results provide guidance for the Stirling power package interface design. Properly designed, the interface may lead to increased structural capability and power performance beyond what was demonstrated in the successful 1999 vibration test. Dynamic testing performed to date at Glenn has shown that the Stirling convertors can withstand liftoff random vibration environments and meet "good neighbor" vibratory emission requirements. Furthermore, the future utilization of the information obtained during the tests will allow the corporation selected to be the Stirling system integrator to optimize their convertor and system interfaces designs. Glenn's Thermo-Mechanical Systems Branch provides Stirling technology expertise under a Space Act Agreement with the Department of Energy. Additional vibration testing by Glenn's Structural Systems Dynamics Branch is planned to continue to demonstrate the Stirling power system's vibration capability as its technology and flight system designs progress.

Shock and vibration tests of uranium mononitride fuel pellets for a space power nuclear reactor

NASA Technical Reports Server (NTRS)

Adams, D. W.

1972-01-01

Shock and vibration tests were conducted on cylindrically shaped, depleted, uranium mononitride (UN) fuel pellets. The structural capabilities of the pellets were determined under exposure to shock and vibration loading which a nuclear reactor may encounter during launching into space. Various combinations of diametral and axial clearances between the pellets and their enclosing structures were tested. The results of these tests indicate that for present fabrication of UN pellets, a diametral clearance of 0.254 millimeter and an axial clearance of 0.025 millimeter are tolerable when subjected to launch-induced loads.

Skylab

NASA Image and Video Library

1971-06-01

The Apollo Telescope Mount (ATM), one of four major components comprising the Skylab, was designed and developed by the Marshall Space Flight Center. In this image, the ATM is shown undergoing horizontal vibration testing in a vibration test unit.

Dynamic Capability of an Operating Stirling Convertor

NASA Technical Reports Server (NTRS)

Goodnight, Thomas W.; Hughes, William O.; McNelis, Mark E.

2000-01-01

The NASA John H. Glenn Research Center and the US Department of Energy are currently developing a Stirling convertor for use as an advanced spacecraft power system for future NASA deep-space missions. NASA Headquarters has recently identified the Stirling technology generator for potential use as the spacecraft power system for two of NASA's new missions, the Europa Orbiter and the Solar Probe missions (planned for launch in 2006 and 2007 respectively). As part of the development of this power system, a Stirling Technology Demonstration Convertor was vibration tested at NASA John H. Glenn Research Center to verify its survivability and capability of withstanding the harsh dynamic environment typically seen by the spacecraft when it is launched by an expendable launch vehicle. The Technology Demonstration Convertor was fully operational (producing power) during the random vibration testing. The output power of the convertor and other convertor performance indicators were measured during the testing, and these results are discussed in this paper. Numerous accelerometers and force gauges also were used to provide information on the dynamic characteristics of the Technology Demonstration Convertor and as an indication of any possible damage due to the vibration. These measurements will also be discussed in this paper. The vibration testing of the Stirling Technology Demonstration Convertor was extremely successful. The Technology Demonstration Convertor survived all its vibration testing with no structural damage or functional performance degradation. As a result of this testing, the Stirling convertor's capability to withstand vibration has been demonstrated, enabling its usage in future spacecraft power systems.

Development and evaluation of vibrating Kelly Ball Test (VKelly test) for the workability of concrete.

DOT National Transportation Integrated Search

2015-03-01

Due to the low workability of slipform concrete mixtures, the science of rheology is not strictly applicable for such concrete. However, : the concept of rheological behavior may still be considered useful. A novel workability test method (Vibrating ...

A Vibration Isolation System for Use in a Large Thermal Vacuum Test Facility

NASA Technical Reports Server (NTRS)

Hershfeld, Donald; VanCampen, Julie

2002-01-01

A thermal vacuum payload platform that is isolated from background vibration is required to support the development of future instruments for Hubble Space Telescope (HST) and the Next Generation Space Telescope (NGST) at the Goddard Space Flight Center (GSFC). Because of the size and weight of the thermal/vacuum facility in which the instruments are tested, it is not practical to isolate the entire facility externally. Therefore, a vibration isolation system has been designed and fabricated to be installed inside the chamber. The isolation system provides a payload interface of 3.05 m (10 feet) in diameter and is capable of supporting a maximum payload weight of 4536 kg (10,000 Lbs). A counterweight system has been included to insure stability of payloads having high centers of gravity. The vibration isolation system poses a potential problem in that leakage into the chamber could compromise the ability to maintain vacuum. Strict specifications were imposed on the isolation system design to minimize leakage. Vibration measurements, obtained inside the chamber, prior to installing the vibration isolation system, indicated levels in all axes of approximately 1 milli-g at about 20 Hz. The vibration isolation system was designed to provide a minimum attenuation of 40 dB to these levels. This paper describes the design and testing of this unique vibration isolation system. Problems with leakage and corrective methods are presented. Isolation performance results are also presented.

Coupled Facility/Payload Vibration Modeling Improvements

NASA Technical Reports Server (NTRS)

Carnahan, Timothy M.; Kaiser, Michael

2015-01-01

A major phase of aerospace hardware verification is vibration testing. The standard approach for such testing is to use a shaker to induce loads into the payload. In preparation for vibration testing at NASA/GSFC there is an analysis to assess the responses of the payload. A new method of modeling the test is presented that takes into account dynamic interactions between the facility and the payload. This dynamic interaction has affected testing in the past, but been ignored or adjusted for during testing. By modeling the combination of the facility and test article (payload) it is possible to improve the prediction of hardware responses. Many aerospace test facilities work in similar way to those at NASA Goddard Space Flight Center. Lessons learned here should be applicable to other test facilities with similar setups.

Experimental and theoretical investigation of passive damping concepts for member forced and free vibration

NASA Technical Reports Server (NTRS)

Razzaq, Zia; Mykins, David W.

1987-01-01

Potential passive damping concepts for use in space structures are identified. The effectiveness of copper brush, wool swab, and silly putty in chamber dampers is investigated through natural vibration tests on a tubular aluminum member. The member ends have zero translation and possess partial rotational restraints. The silly putty in chamber dampers provide the maximum passive damping efficiency. Forced vibration tests are then conducted with one, two, and three damper chambers containing silly putty. Owing to the limitation of the vibrator used, the performance of these dampers could not be evaluated experimentally until the forcing function was disengaged. Nevertheless, their performance is evaluated through a forced dynamic finite element analysis conducted as a part of this investigation. The theoretical results based on experimentally obtained damping ratios indicate that the passive dampers are considerably more effective under member natural vibration than during forced vibration. Also, the maximum damping under forced vibration occurs at or near resonance.

Ambient Vibration Testing for Story Stiffness Estimation of a Heritage Timber Building

PubMed Central

Min, Kyung-Won; Kim, Junhee; Park, Sung-Ah; Park, Chan-Soo

2013-01-01

This paper investigates dynamic characteristics of a historic wooden structure by ambient vibration testing, presenting a novel estimation methodology of story stiffness for the purpose of vibration-based structural health monitoring. As for the ambient vibration testing, measured structural responses are analyzed by two output-only system identification methods (i.e., frequency domain decomposition and stochastic subspace identification) to estimate modal parameters. The proposed methodology of story stiffness is estimation based on an eigenvalue problem derived from a vibratory rigid body model. Using the identified natural frequencies, the eigenvalue problem is efficiently solved and uniquely yields story stiffness. It is noteworthy that application of the proposed methodology is not necessarily confined to the wooden structure exampled in the paper. PMID:24227999

Train-induced field vibration measurements of ground and over-track buildings.

PubMed

Zou, Chao; Wang, Yimin; Moore, James A; Sanayei, Masoud

2017-01-01

Transit-oriented development, such as metro depot and over-track building complexes, has expanded rapidly over the last 5years in China. Over-track building construction has the advantage of comprehensive utilization of land resources, ease of commuting to work, and provide funds for subway construction. But the high frequency of subway operations into and out of the depots can generate excessive vibrations that transmit into the over track buildings, radiate noise within the buildings, hamper the operation of vibration sensitive equipment, and adversely affect the living quality of the building occupants. Field measurements of vibration during subway operations were conducted at Shenzhen, China, a city of 10.62 million people in southern China. Considering the metro depot train testing line and throat area train lines were the main vibration sources, vibration data were captured in five measurement setups. The train-induced vibrations were obtained and compared with limitation of FTA criteria. The structure-radiated noise was calculated using measured vibration levels. The vertical vibration energy directly passed through the columns on both sides of track into the platform, amplifying vibration on the platform by up to 6dB greater than ground levels at testing line area. Vibration amplification around the natural frequency in the vertical direction of over-track building made the peak values of indoor floor vibration about 16dB greater than outdoor platform vibration. We recommend to carefully examining design of new over-track buildings within 40m on the platform over the throat area to avoid excessive vertical vibrations and noise. For both buildings, the measured vertical vibrations were less than the FTA limit. However, it is demonstrated that the traffic-induced high-frequency noise has the potential to annoy occupants on the upper floors. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of vibration on retention characteristics of screen acquisition systems. [for surface tension propellant acquisition

NASA Technical Reports Server (NTRS)

Tegart, J. R.; Aydelott, J. C.

1978-01-01

The design of surface tension propellant acquisition systems using fine-mesh screen must take into account all factors that influence the liquid pressure differentials within the system. One of those factors is spacecraft vibration. Analytical models to predict the effects of vibration have been developed. A test program to verify the analytical models and to allow a comparative evaluation of the parameters influencing the response to vibration was performed. Screen specimens were tested under conditions simulating the operation of an acquisition system, considering the effects of such parameters as screen orientation and configuration, screen support method, screen mesh, liquid flow and liquid properties. An analytical model, based on empirical coefficients, was most successful in predicting the effects of vibration.

Interferometric fibre-optic curvature sensing for structural, directional vibration measurements

NASA Astrophysics Data System (ADS)

Kissinger, Thomas; Chehura, Edmon; James, Stephen W.; Tatam, Ralph P.

2017-06-01

Dynamic fibre-optic curvature sensing using fibre segment interferometry is demonstrated using a cost-effective rangeresolved interferometry interrogation system. Differential strain measurements from four fibre strings, each containing four fibre segments of gauge length 20 cm, allow the inference of lateral vibrations as well as the direction of the vibration of a cantilever test object. Dynamic tip displacement resolutions in the micrometre range over a 21 kHz interferometric bandwidth demonstrate the suitability of this approach for highly sensitive fibre-optic directional vibration measurements, complementing existing laser vibrometry techniques by removing the need for side access to the structure under test.

The Shock and Vibration Digest, Volume 14, Number 4

DTIC Science & Technology

1982-04-01

temperature, humidity, shock, and vibration -- can influence this capability; as a result an almost continuous program of research and development has...pro- ducing reliability tests. For some time there has been interest in the Army Test Methodology program for developing a vibration system capable...geology of the Livermore Valley is obtained. 82-768 Transient Stress Wave Propagation in HTGR Fuel Element Impacts I.T. Almajan and P.D. Smith

Journal of Engineering Thermophysics (Selected Articles),

DTIC Science & Technology

1983-05-20

A SURGE TEST OF A TWIN-SHAFT TURBOJET ENGINE ON GROUND TEST BED* Chiang Feng (Shengyang Aeroengine Company) ABSTRACT Instrument technique for...oscillogram for the static pressure behind the two compressors. This noise was analyzed and believed to have arisen from the vibrations of the rotating blades...booms are heard. The vibrational energy of the surge is enormous, especially in the range of 85-90% of rotational speed. One can feel the vibrations

The Shock and Vibration Bulletin. Part 3. Shock Testing, Shock Analysis

DTIC Science & Technology

1974-08-01

APPROXIMATE TRANSFORMATION C.S. O’Hearne and J.W. Shipley, Martin Marietta Aerospace, Orlando, Florida LINEAR LUMPED-MASS MODELING TECHNIQUES FOR BLAST LOADED...Leppert, B.K. Wada, Jet Propulsion Laboratory, Pasadena, California, and R. Miyakawa, Martin - Marietta Aerospace, Denver, Colorado (assigned to the Jet...Wilmington, Delaware Vibration Testing and Analysis DEVELOPMENT OF SAM-D MISSILE RANDOM VIBRATION RESPONSE LOADS P.G. Hahn, Martin Marietta Aerospace

Dynamic Testing of In-Situ Composite Floors and Evaluation of Vibration Serviceability Using the Finite Element Method

DTIC Science & Technology

2006-08-21

Dynamic Testing of In-Situ Composite Floors and Evaluation of Vibration Serviceability Using the Finite Element Method By Anthony R. Barrett...Setareh Alfred L. Wicks 21 August 2006 Blacksburg, VA Keywords: vibration, floor, serviceability , walking, modal analysis, fundamental frequency...burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, along the crawlerway in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, along the crawlerway in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Ride Dynamics and Evaluation of Human Exposure to Whole Body Vibration. Change 1

DTIC Science & Technology

2012-04-03

vehicle specification and/or the detailed test plan. This (half-round obstacle) accelerometer will be low-pass filtered ( post test ) at 30 Hz...Engineers TARADCOM Tank-Automotive Research and Development Command TOP Test Operations Procedure VDV Vibration Dose Value WBV Whole Body...

Viking Mars lander 1975 dynamic test model/orbiter developmental test model forced vibration test

NASA Technical Reports Server (NTRS)

Fortenberry, J.; Brownlee, G. R.

1974-01-01

The Viking Mars Lander 1975 dynamic test model and orbiter developmental test model were subjected to forced vibration sine tests. Flight acceptance (FA) and type approval (TA) test levels were applied to the spacecraft structure in a longitudinal test configuration using a 133,440-N (30,000-lb) force shaker. Testing in the two lateral axes (X, Y) was performed at lower levels using four 667-N (150-lb) force shakers. Forced vibration qualification (TA) test levels were successfully imposed on the spacecraft at frequencies down to 10 Hz. Measured responses showed the same character as analytical predictions, and correlation was reasonably good. Because of control system test tolerances, orbiter primary structure generally did not reach the design load limits attained in earlier static testing. A post-test examination of critical orbiter structure disclosed no apparent damage to the structure as a result of the test environment.

Vibration testing and analysis using holography

NASA Technical Reports Server (NTRS)

1971-01-01

Time average holography is useful in recording steady state vibrational mode patterns. Phase relationships under steady state conditions are measured with real time holography and special phase shifting techniques. Data from Michelson interferometer verify vibration amplitudes from holographic data.

Space Shuttle Crawler Transporter Vibration Analysis in Support of Rollout Fatigue Load Spectra Verification Program

NASA Technical Reports Server (NTRS)

Margasahayam, Ravi N.; Meyer, Karl A.; Nerolich, Shaun M.; Burton, Roy C.; Gosselin, Armand M.

2004-01-01

The Crawler Transporter (CT), designed and built for the Apollo Program in the 1960's and surpassing its initial operational life, has become an integral part of the Space Shuttle Program (SSP). The CT transports the Space Shuttle Vehicle (SSV) stack, atop the Mobile Launch Platform (MLP), from the Vehicle Assembly Building (VAB) to the launch pad. This support structure provides hydraulic jacking, leveling and load equalization for the 12 million pound stack on its 3.5-5.0 mile rollout to the launch pad. Major elements of the SSV, consisting of the orbiter, solid rocket boosters (SRB) and external tank (ET) have required fatigue analyses as part of the mission life certification. Compared to rollout vibration, the SSV sees relatively high vibration loads during launch, ascent, descent and landing phases of the mission. Although preliminary measured SRB vibration levels during rollout were of low amplitude and frequency, the duration of the rollout phase is typically high, from 5-6 hours. As part of an expanded mission life assessment, additional certification effort was initiated to define fatigue load spectra for rollout. This study addresses the CT vibration analyses in support of the rollout fatigue study. Structural models developed for modal and vibration analyses were used to identify unique CT, CT/MLP and CT/MLP/SRB vibration characteristics for comparison to instrumented rollout tests. Whereas the main structural and vibration characteristics of the SSV are well defined, minimum analytical and vibration test data on the Crawler Transporter were available. Unique vibration characteristics of the CT are attributable to the drive mechanism, hydraulic jacking system, structural framing and the CT-to-MLP support pad restraints. Initial tests performed on the CT/MLP/SRB configuration showed reasonable correlation with predicted mode shapes and frequencies.

Design and evaluation of a suspension seat to reduce vibration exposure of subway operators: a case study.

PubMed

Marcotte, Pierre; Beaugrand, Sylvie; Boutin, Jérôme; Larue, Christian

2010-01-01

Subway operators have complained about discomfort caused by whole-body vibration. To address this problem, a suspension seat with extensive ergonomic features has been adapted to the confined space of the subway operator cab. The suspension was modified from an existing suspension in order to reduce the dominant frequency of the subway vertical vibration (2.4 Hz). The suspension seat has been extensively tested on a vertical hydraulic shaker. These tests have shown that the SEAT value was lower for a higher vibration level, for higher subject weight, and for the suspension adjusted at median height. The seat also produces a lower SEAT value when there was a predominance of the 6 Hz vibration component. The horizontal seat adjustments had no influence on the suspension SEAT value. Removing the suspension damper also decreases the SEAT value for all the tested configurations. The final version of the suspension seat prototype was validated during normal subway operation with 19 different operators having weight in the 5th, 50th and 95th percentile of the operator population. Accelerations were measured with triaxial accelerometers at the seat cushion, above the suspension and on the floor. In addition to the vibration measurements, each operator was asked about his perceived discomfort from vibration exposure. Globally, the suspension seat attenuated the vertical vibration (SEAT values from 0.86 to 0.99), but discomfort due to amplification of the 2.4 Hz component occurred when the suspension height was adjusted at the minimum, even when the global weighted acceleration was lower (SEAT value < 1). These results suggest that in order to reduce the discomfort caused by whole-body vibration, the transmissibility of the seat should also be considered, in particular when there is a dominant frequency in the vibration spectra.

Vibration characteristics of 1/8-scale dynamic models of the space-shuttle solid-rocket boosters

NASA Technical Reports Server (NTRS)

Leadbetter, S. A.; Stephens, W.; Sewall, J. L.; Majka, J. W.; Barret, J. R.

1976-01-01

Vibration tests and analyses of six 1/8 scale models of the space shuttle solid rocket boosters are reported. Natural vibration frequencies and mode shapes were obtained for these aluminum shell models having internal solid fuel configurations corresponding to launch, midburn (maximum dynamic pressure), and near endburn (burnout) flight conditions. Test results for longitudinal, torsional, bending, and shell vibration frequencies are compared with analytical predictions derived from thin shell theory and from finite element plate and beam theory. The lowest analytical longitudinal, torsional, bending, and shell vibration frequencies were within + or - 10 percent of experimental values. The effects of damping and asymmetric end skirts on natural vibration frequency were also considered. The analytical frequencies of an idealized full scale space shuttle solid rocket boosted structure are computed with and without internal pressure and are compared with the 1/8 scale model results.

[Hand-arm vibration syndrome in a nurse carrying out gypsum cutting operations].

PubMed

Speziale, Martina; Picchiotti, E

2009-01-01

A professional nurse, employed mainly on gypsum cutting operations, developed a hand-arm vibration syndrome with Raynaud's phenomenon, neurosensitive disorders and impairment of the bone and joints apparatus of the hand and arm. The nurse underwent diagnostic investigations (cold test, X-ray of the upper limbs, blood tests); also the vibration levels transmitted from instrument were measured and the exposure times were established. Clinical investigations showed the presence of a hand-arm vibration syndrome with secondary Raynaud's phenomenon and environmental surveys revealed very high vibration levels, such as could be associated with the disease with a causal relationship. In the literature no reports exist of the vibration syndrome being associated with health care workers in orthopaedic departments. The case described in this study occurred because of peculiar organisational factors that most likely have never occurred in other hospitals or orthopaedic departments.

Farfield Ion Current Density Measurements before and after the NASA HiVHAc EDU2 Vibration Test

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Shastry, Rohit

2012-01-01

There is an increasing need to characterize the plasma plume of the NASA HiVHAc thruster in order to better understand the plasma physics and to obtain data for spacecraft interaction studies. To address this need, the HiVHAc research team is in the process of developing a number of plume diagnostic systems. This paper presents the initial results of the farfield current density probe diagnostic system. Farfield current density measurements were carried out before and after a vibration test of the HiVHAc engineering development unit 2 that simulate typical launch conditions. The main purposes of the current density measurements were to evaluate the thruster plume divergence and to investigate any changes in the plasma plume that may occur as a result of the vibration test. Radial sweeps, as opposed to the traditional polar sweeps, were performed during these tests. The charged-weighted divergence angles were found to vary from 16 to 28 degrees. Charge density profiles measured pre- and post-vibration-test were found to be in excellent agreement. This result, alongside thrust measurements reported in a companion paper, confirm that the operation of the HiVHAc engineering development unit 2 were not altered by full-level/random vibration testing.

Some space shuttle tile/strain-isolator-pad sinusoidal vibration tests

NASA Technical Reports Server (NTRS)

Miserentino, R.; Pinson, L. D.; Leadbetter, S. A.

1980-01-01

Vibration tests were performed on the tile/strain-isolator-pad system used as thermal protection for the space shuttle orbiter. Experimental data on normal and in-plane vibration response and damping properties are presented. Three test specimens exhibited shear type motion during failures that occurred in the tile near the tile/strain-isolator-pad bond-line. A dynamic instability is described which has large in-plane motion at a frequency one-half that of the nominal driving frequency. Analysis shows that this phenomenon is a parametric response.

Resolving Sensory Conflict: the Effect of Muscle Vibration on Postural Stability

NASA Technical Reports Server (NTRS)

Layne, Charles S.

1991-01-01

The otolith-tilt reinterpretation hypothesis (OTTR) proposes that the central nervous system adapts to weightlessness by reinterpreting all otolith input as linear motion. While interpreting otolith input exclusively as linear motion is functionally useful in space, it is maladaptive upon return to Earth. Astronauts have reported experiencing illusory sensations during head movement which contributes to postural instability. The effect is assessed of muscle vibration in combination with a variety of sensory conflicts on postural equilibrium. The equilibrium of six healthy subjects was tested using the EquiTest sensory test protocol, with and without the confounding influence of triceps surea vibration. The data were analyzed with repeated measures with vibration, vision status, and platform status as independent variables. All main effects and an interaction between the presence of vision and platform sway referencing were found to be significant. Overall, a 4.5 pct. decrease in postural stability was observed with vibration. The trend of the difference scores between conditions with and without vibration suggests that vibration is most destabilizing when the triceps surea is able to change length during postural sway (i.e., conditions with a fixed support surface). The impact of sway referencing vision was virtually identical to that of eye closure, providing compelling evidence that sway referencing 'nulls out' useful cues about subject sway.

Acute bone response to whole body vibration in healthy pre-pubertal boys.

PubMed

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.

Effect of shelf aging on vibration transmissibility of anti-vibration gloves

PubMed Central

SHIBATA, Nobuyuki

2017-01-01

Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves. PMID:28978817

Sensor validation and fusion for gas turbine vibration monitoring

NASA Astrophysics Data System (ADS)

Yan, Weizhong; Goebel, Kai F.

2003-08-01

Vibration monitoring is an important practice throughout regular operation of gas turbine power systems and, even more so, during characterization tests. Vibration monitoring relies on accurate and reliable sensor readings. To obtain accurate readings, sensors are placed such that the signal is maximized. In the case of characterization tests, strain gauges are placed at the location of vibration modes on blades inside the gas turbine. Due to the prevailing harsh environment, these sensors have a limited life and decaying accuracy, both of which impair vibration assessment. At the same time bandwidth limitations may restrict data transmission, which in turn limits the number of sensors that can be used for assessment. Knowing the sensor status (normal or faulty), and more importantly, knowing the true vibration level of the system all the time is essential for successful gas turbine vibration monitoring. This paper investigates a dynamic sensor validation and system health reasoning scheme that addresses the issues outlined above by considering only the information required to reliably assess system health status. In particular, if abnormal system health is suspected or if the primary sensor is determined to be faulted, information from available "sibling" sensors is dynamically integrated. A confidence expresses the complex interactions of sensor health and system health, their reliabilities, conflicting information, and what the health assessment is. Effectiveness of the scheme in achieving accurate and reliable vibration evaluation is then demonstrated using a combination of simulated data and a small sample of a real-world application data where the vibration of compressor blades during a real time characterization test of a new gas turbine power system is monitored.

Central Tire Inflation: Demonstration Tests in the South

Treesearch

R.B. Rummer; C. Ashmore; D.L. Sirois; C.L. Rawlins

1990-01-01

Tests of prototype Central Tire Inflation (CT11 systems were conducted to quantify CT1 performance, road wear, and truck vibration. The CT1 systems were tested in both experimental and operational settings. Changes in the road surface that occurred during the tests could not be statistically attributed to reduced tire pressure. Vibration at the seat base, however,...

Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: AMSU-A1 METSAT Instrument (S/N 105) Qualification, Level Vibration Tests of December 1998 (S/O 605445, OC-419)

NASA Technical Reports Server (NTRS)

Heffner, R. J.

1998-01-01

This is the Engineering Test Report, AMSU-AL METSAT Instrument (S/N 105) Qualification Level Vibration Tests of December 1998 (S/0 605445, OC-419), for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

Voyager: Vibration Acoustics and Pyro Shock Testing

NASA Image and Video Library

2017-07-05

An engineer works on vibration acoustics and pyro shock testing for one of NASA's Voyager spacecraft on November 18, 1976. Several of the spacecraft's science instruments are visible at left. https://photojournal.jpl.nasa.gov/catalog/PIA21733

A Novel Well Drill Assisted with High-Frequency Vibration Using the Bending Mode

PubMed Central

Qi, Xinda; Chen, Weishan; Tang, Xintian; Shi, Shengjun

2018-01-01

It is important for companies to increase the efficiency of drilling as well as prolong the lifetime of the drilling tool. Since some previous investigations indicated that a superposition of well drilling with an additional vibration increases the drilling efficiency, this paper introduces a novel well drill which is assisted with additional vibrations by means of piezoelectric sandwich bending vibration transducer. The proposed drill uses bending vibrations in two different directions to from an elliptical trajectory movement, which can help the drill to break the surface of hard material more efficiently and clean away the lithic fragments more easily. The proposed well drill with bending vibration transducer is designed to have a resonance frequency of the first bending vibration mode of about 1779 Hz. The motion equation of the particle on the edge of the drill bit is developed and analyzed. The vibration trajectory of the particle on the edge of the drill bit is calculated by using finite element method. A prototype of the proposed drill using bending vibrations is fabricated and tested to verify the aim of drilling efficiency increase. The feed speed of the vibration assisted drilling is tested to be about 0.296 mm/s when the excitation voltage of the transducer is 300 V, while this speed decreases to about 0.195 mm/s when no vibration is added. This comparison shows that the feed speed of the vibration assisted drilling is about 52% higher than that of the normal drilling, which means the proposed drill has a better efficiency and it is important to consider vibration superimposition in well drilling. In addition, the surface of the drill hole gained by the vibration assisted drilling is smoother than that of the normal drilling, which makes the clearance easier. PMID:29641481

Quiet Spike(TradeMark) Build-up Ground Vibration Testing Approach

NASA Technical Reports Server (NTRS)

Spivey, Natalie D.; Herrera, Claudia Y.; Truax, Roger; Pak, Chan-gi; Freund, Donald

2007-01-01

Flight tests of the Gulfstream Aerospace Corporation s Quiet Spike(TradeMark) hardware were recently completed on the National Aeronautics and Space Administration Dryden Flight Research Center F-15B airplane. NASA Dryden uses a modified F-15B (836) airplane as a testbed aircraft to cost-effectively fly flight research experiments that are typically mounted underneath the airplane, along the fuselage centerline. For the Quiet Spike(TradeMark) experiment, instead of a centerline mounting, a forward-pointing boom was attached to the radar bulkhead of the airplane. The Quiet Spike(TradeMark) experiment is a stepping-stone to airframe structural morphing technologies designed to mitigate the sonic-boom strength of business jets flying over land. Prior to flying the Quiet Spike(TradeMark) experiment on the F-15B airplane several ground vibration tests were required to understand the Quiet Spike(TradeMark) modal characteristics and coupling effects with the F-15B airplane. Because of flight hardware availability and compressed schedule requirements, a "traditional" ground vibration test of the mated F-15B Quiet Spike(TradeMark) ready-for-flight configuration did not leave sufficient time available for the finite element model update and flutter analyses before flight-testing. Therefore, a "nontraditional" ground vibration testing approach was taken. This report provides an overview of each phase of the "nontraditional" ground vibration testing completed for the Quiet Spike(TradeMark) project.

Structural Dynamics Testing of Advanced Stirling Convertor Components

NASA Technical Reports Server (NTRS)

Oriti, Salvatore M.; Williams, Zachary Douglas

2013-01-01

NASA Glenn Research Center has been supporting the development of Stirling energy conversion for use in space. Lockheed Martin has been contracted by the Department of Energy to design and fabricate flight-unit Advanced Stirling Radioisotope Generators, which utilize Sunpower, Inc., free-piston Advanced Stirling Convertors. The engineering unit generator has demonstrated conversion efficiency in excess of 20 percent, offering a significant improvement over existing radioisotope-fueled power systems. NASA Glenn has been supporting the development of this generator by developing the convertors through a technology development contract with Sunpower, and conducting research and experiments in a multitude of areas, such as high-temperature material properties, organics testing, and convertor-level extended operation. Since the generator must undergo launch, several launch simulation tests have also been performed at the convertor level. The standard test sequence for launch vibration exposure has consisted of workmanship and flight acceptance levels. Together, these exposures simulate what a flight convertor will experience. Recently, two supplementary tests were added to the launch vibration simulation activity. First was a vibration durability test of the convertor, intended to quantify the effect of vibration levels up to qualification level in both the lateral and axial directions. Second was qualification-level vibration of several heater heads with small oxide inclusions in the material. The goal of this test was to ascertain the effect of the inclusions on launch survivability to determine if the heater heads were suitable for flight.

Coupled Facility-Payload Vibration Modeling Improvements

NASA Technical Reports Server (NTRS)

Carnahan, Timothy M.; Kaiser, Michael A.

2015-01-01

A major phase of aerospace hardware verification is vibration testing. The standard approach for such testing is to use a shaker to induce loads into the payload. In preparation for vibration testing at National Aeronautics and Space Administration/Goddard Space Flight Center an analysis is performed to assess the responses of the payload. A new method of modeling the test is presented that takes into account dynamic interactions between the facility and the payload. This dynamic interaction has affected testing in the past, but been ignored or adjusted for during testing. By modeling the combined dynamics of the facility and test article (payload) it is possible to improve the prediction of hardware responses. Many aerospace test facilities work in similar way to those at NASA/Goddard Space Flight Center. Lessons learned here should be applicable to other test facilities with similar setups.

MODE IDENTIFICATION OF AN ARCH DAM BY A DYNAMIC AIR-GUN TEST.

USGS Publications Warehouse

Liu, Hsi-Ping; Fedock, Joseph J.; Fletcher, Jon B.

1986-01-01

Thirteen natural frequencies of a concrete arch dam (Monticello Dam near Sacramento, California) have been identified by using a dynamic testing method which employs an air gun firing in the reservoir as the excitation source. These vibrations modes are determined from the peak responses in the Fourier amplitude spectra of the free-vibration data recorded at three crest locations using three-component geophones. Comparisons of the first five natural frequencies with results obtained by forced vibration tests using rotating mass shakers show good agreement. The next eight higher-frequency modes, not previously identified, are determined from data of the present tests.

NASA-DoD Lead-Free Electronics Project: Vibration Test

NASA Technical Reports Server (NTRS)

Woodrow, Thomas A.

2010-01-01

Vibration testing was conducted by Boeing Research and Technology (Seattle) for the NASA-DoD Lead-Free Electronics Solder Project. This project is a follow-on to the Joint Council on Aging Aircraft/Joint Group on Pollution Prevention (JCAA/JG-PP) Lead-Free Solder Project which was the first group to test the reliability of lead-free solder joints against the requirements of the aerospace/miLItary community. Twenty seven test vehicles were subjected to the vibration test conditions (in two batches). The random vibration Power Spectral Density (PSD) input was increased during the test every 60 minutes in an effort to fail as many components as possible within the time allotted for the test. The solder joints on the components were electrically monitored using event detectors and any solder joint failures were recorded on a Labview-based data collection system. The number of test minutes required to fail a given component attached with SnPb solder was then compared to the number of test minutes required to fail the same component attached with lead-free solder. A complete modal analysis was conducted on one test vehicle using a laser vibrometer system which measured velocities, accelerations, and displacements at one . hundred points. The laser vibrometer data was used to determine the frequencies of the major modes of the test vehicle and the shapes of the modes. In addition, laser vibrometer data collected during the vibration test was used to calculate the strains generated by the first mode (using custom software). After completion of the testing, all of the test vehicles were visually inspected and cross sections were made. Broken component leads and other unwanted failure modes were documented.

The Shock and Vibration Bulletin. Part 1. Welcome, Keynote Address, Invited Papers, Pyrotechnic Shock, and Shock Testing and Analysis

DTIC Science & Technology

1983-05-01

DESIGN PROCEDURE M. S. IIAndal, University of Vermont, Burlington, VT Machinery Dynamics ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF ROTATING BLADE... methodology to accurately predict rotor vibratory loads and has recently been initiated for detail design and bench test- coupled rotor/airframe vibrations... design methodology , a trating on the basic disciplines of aerodynamics and struc. coupled rotor/airframe vibration analysis has been developed. tural

Dynamics Control Approaches to Improve Vibratory Environment of the Helicopter Aircrew

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh Kanchana

Although helicopter has become a versatile mode of aerial transportation, high vibration levels leads to poor ride quality for its passengers and aircrew. Undesired vibration transmitted through the helicopter seats have been known to cause fatigue and discomfort to the aircrew in the short-term as well as neck strain and back pain injuries due to long-term exposure. This research study investigated the use of novel active as well as passive methodologies integrated in helicopter seats to mitigate the aircrew exposure to high vibration levels. Due to significantly less certification effort required to modify the helicopter seat structure, application of novel technologies to the seat is more practical compared to flight critical components such as the main rotor to reduce aircrew vibration. In particular, this research effort developed a novel adaptive seat mount approach based on active vibration control technology. This novel design that incorporated two stacked piezoelectric actuators as active struts increases the bending stiffness to avoid the low frequency resonance while generating forces to counteract higher harmonic vibration peaks. A real-time controller implemented using a feed-forward algorithm based on adaptive notches counteracted the forced vibration peaks while a robust feedback control algorithm suppressed the resonance modes. The effectiveness of the adaptive seat mount system was demonstrated through extensive closed-loop control tests on a full-scale helicopter seat using representative helicopter floor vibration profiles. Test results concluded that the proposed adaptive seat mount approach based on active control technology is a viable solution for the helicopter seat vibration control application. In addition, a unique flight test using a Bell-412 helicopter demonstrated that the aircrew is exposed to high levels of vibration during flight and that the whole body vibration spectrum varied substantially depending on operating conditions as well as the aircrew configurations. This investigation also demonstrated the suitability of integrating novel energy absorbing cushion materials to the seat as a low cost solution to improve aircrew vibration suppression. Therefore, it was recommended to pursue certification of novel seat cushion materials as a near-term solution to mitigate undesirable occupational health hazards in helicopter aircrew due to vibration exposure.

A Magnetic Suspension and Excitation System for Spin Vibration Testing of Turbomachinery Blades

NASA Technical Reports Server (NTRS)

Johnson, Dexter; Brown, Gerald V.; Mehmed, Oral

1998-01-01

The Dynamic Spin Rig (DSR) is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. A heteropolar radial active magnetic bearing was integrated into the DSR to provide non-contact magnetic suspension and mechanical excitation of the rotor to induce turbomachinery blade vibrations. The magnetic bearing replaces one of the two existing conventional radial ball bearings. Prior operation of the DSR used two voice-coil type linear electromagnetic shakers which provided axial excitation of the rotor. The new magnetic suspension and excitation system has provided enhanced testing capabilities. Tests were performed at high rotational speeds for longer duration and higher vibration amplitudes. Some characteristics of the system include magnetic bearing stiffness values up to 60,000 lb./in., closed loop control bandwidth around 500 Hz, and multi-directional radial excitation of the rotor. This paper reports on the implementation and operation of this system and presents some test results using this system.

Application of a computerized vibroacoustic data bank for random vibration criteria development

NASA Technical Reports Server (NTRS)

Ferebee, R. C.

1982-01-01

A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablets, and a dry silver hard copier which are all desk top type hardware and occupy minimal space. Currently, the data bank contains data from the Saturn 5 and Titan 3 flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one third octave band plots over the frequency range from 20 to 2000 Hz. The data were stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data were statistically analyzed, and the resulting 97.5 percent confidence levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. A user's manual is included to guide potential users through the programs.

Testing of YUH-61A helicopter transmission in NASA Lewis 2240-kW (3000-hp facility

NASA Technical Reports Server (NTRS)

Mitchell, A. M.; Oswald, F. B.; Schuller, F. T.

1986-01-01

A helicopter transmission that was being considered for the Army's Utility Tactical Transport Attack System (UTTAS) was tested in the NASA Lewis 2240-kW (3000-hp) test facility to obtain the transmission's operational data. The results will form a vibration and efficiency data base for evaluation similar-class helicopter transmissions. The transmission's mechanical efficiency was determined to be 98.7 percent at its rated power level of 2080 kW (2792 hp). At power levels up to 113 percent of rated the transmission displayed 56 percent higher vibration acceleration levels on the right input than on the left input. Both vibration signature analysis and final visual inspection indicated that the right input spiral-bevel gear had poor contact patterns. The highest vibration meter level was 52 g's rms at the accessory gear, which had free-wheeling gearsets. At 113 percent power and 100 percent rated speed the vibration meter levels generally ranged from 3 to 25 g's rms.

Maintaining Flatness of a Large Aperture Potassium Bromide Beamsplitter Through Mounting and Vibration

NASA Technical Reports Server (NTRS)

Losch, Patricia; Lyons, James J., III; Morell, Armando; Heaney, Jim

1998-01-01

The Composite Infrared Spectrometer (CIRS) instrument on the Cassini Mission launched in October of 1997. The CIRS instrument contains a mid-infrared (MIR) and a far-infrared interferometer (FIR) and operates at 170 Kelvin. The MIR is a Michelson Fourier transform spectrometer utilizing a 76 mm (3 inch) diameter potassium bromide beamsplitter and compensator pair. The potassium bromide elements were tested to verify effects of cooldown and vibration prior to integration into the instrument. The instrument was then aligned at ambient temperatures, tested cryogenically and re-verified after vibration. 'Me stringent design optical figure requirements for the beamsplitter and compensator included fabrication errors, mounting stresses and vibration load effects. This paper describes the challenges encountered in mounting the elements to minimize distortion and to survive vibration.

Maintaining Flatness of a Large Aperture Potassium Bromide Beamsplitter through Mounting and Vibration

NASA Technical Reports Server (NTRS)

Losch, Patricia; Lyons, James, III; Morell, Armando; Heaney, Jim

1998-01-01

The Composite Infrared Spectrometer (CIRS) instrument on the Cassini Mission launched in October of 1997. The CIRS instrument contains a mid-infrared and a far-infrared interferometer and operates at 170 Kelvin. The mid-infrared interferometer is a Michelson- type Fourier transform spectrometer utilizing a 3 inch diameter potassium bromide beamsplitter/compensator pair. The potassium bromide elements were tested to verify effects of cooldown and vibration prior to integration into the instrument. The instrument was then aligned at ambient temperatures, tested cryogenically and re-verified after vibration. The stringent design optical figure requirements for the beamsplitter and compensator included fabrication errors, mounting stresses and vibration load effects. This paper describes the challenges encountered in mounting the elements to minimize distortion and to survive vibration.

Short-Term Effects of Whole-Body Vibration Combined with Task-Related Training on Upper Extremity Function, Spasticity, and Grip Strength in Subjects with Poststroke Hemiplegia: A Pilot Randomized Controlled Trial.

PubMed

Lee, Jung-Sun; Kim, Chang-Yong; Kim, Hyeong-Dong

2016-08-01

The aim of this study was to determine the effect of whole-body vibration training combined with task-related training on arm function, spasticity, and grip strength in subjects with poststroke hemiplegia. Forty-five subjects with poststroke were randomly allocated to 3 groups, each with 15 subjects as follows: control group, whole-body vibration group, and whole-body vibration plus task-related training group. Outcome was evaluated by clinical evaluation and measurements of the grip strength before and 4 weeks after intervention. Our results show that there was a significantly greater increase in the Fugl-Meyer scale, maximal grip strength of the affected hand, and grip strength normalized to the less affected hand in subjects undergoing the whole-body vibration training compared with the control group after the test. Furthermore, there was a significantly greater increase in the Wolf motor function test and a decrease in the modified Ashworth spasticity total scores in subjects who underwent whole-body vibration plus task-related training compared with those in the other 2 groups after the test. The findings indicate that the use of whole-body vibration training combined with task-related training has more benefits on the improvement of arm function, spasticity, and maximal grip strength than conventional upper limb training alone or with whole-body vibration in people with poststroke hemiplegia.

Field measurements and analyses of environmental vibrations induced by high-speed Maglev.

PubMed

Li, Guo-Qiang; Wang, Zhi-Lu; Chen, Suwen; Xu, You-Lin

2016-10-15

Maglev, offers competitive journey-times compared to the railway and subway systems in markets for which distance between the stations is 100-1600km owing to its high acceleration and speed; however, such systems may have excessive vibration. Field measurements of Maglev train-induced vibrations were therefore performed on the world's first commercial Maglev line in Shanghai, China. Seven test sections along the line were selected according to the operating conditions, covering speeds from 150 to 430km/h. Acceleration responses of bridge pier and nearby ground were measured in three directions and analyzed in both the time and frequency domain. The effects of Maglev train speed on vibrations of the bridge pier and ground were studied in terms of their peak accelerations. Attenuation of ground vibration was investigated up to 30m from the track centerline. Effects of guideway configuration were also analyzed based on the measurements through two different test sections with same train speed of 300km/h. The results showed that peak accelerations exhibited a strong correlation with both train speed and distance off the track. Guideway configuration had a significant effect on transverse vibration, but a weak impact on vertical and longitudinal vibrations of both bridge pier and ground. Statistics indicated that, contrary to the commonly accepted theory and experience, vertical vibration is not always dominant: transverse and longitudinal vibrations should also be considered, particularly near turns in the track. Moreover, measurements of ground vibration induced by traditional high-speed railway train were carried out with the same testing devices in Bengbu in the Anhui Province. Results showed that the Maglev train generates significantly different vibration signatures as compared to the traditional high-speed train. The results obtained from this paper can provide good insights on the impact of Maglev system on the urban environment and the quality of human life nearby. Copyright © 2016 Elsevier B.V. All rights reserved.

Design and performance analysis of a rotary traveling wave ultrasonic motor with double vibrators.

PubMed

Dong, Zhaopeng; Yang, Ming; Chen, Zhangqi; Xu, Liang; Meng, Fan; Ou, Wenchu

2016-09-01

This paper presents the development of a rotary traveling wave ultrasonic motor, in which a vibrating stator and vibrating rotor are combined in one motor. The stator and rotor are designed as similar structures an elastic body and a piezoelectric ceramic ring. In exciting of the piezoelectric ceramics, the elastic body of the stator and rotor will generate respective traveling waves, which force each other forward in the contact zone. Based on the elliptical rule of particle motion and matching principle of vibration, the design rules of two vibrators are determined. The finite element method is used to design the sizes of vibrators to ensure that they operate in resonance, and the simulation is verified by measuring the vibration with an impedance analyzer. It is found out that to maintain an appropriate contact between the stator and rotor, two vibrators need to be designed with close resonance frequencies, different vibration amplitudes, and be driven by an identical driving frequency. To analyze this innovative contact mechanism, particle velocity synthesis theory and contact force analysis using Hertz contact model are carried out. Finally, a prototype is fabricated and tested to verify the theoretical results. The test results show that the output performance of the motor driven by the two vibrators is significantly improved compared to the motor driven by a sole stator or rotor, which confirms the validity of the double-vibrator motor concept. Copyright © 2016 Elsevier B.V. All rights reserved.

Non-Synchronous Vibration of Turbomachinery Airfoils

DTIC Science & Technology

2006-03-01

study and prevention of non-synchronous vibrations. Non-synchronous vibrations in turbine engine blades are the result of the interaction of an...was a modern fan vane blade known as the H2 case. This blade encountered NSV in experimental rig testing. An analysis was performed with TURBO ...design stage for flow over turbine engine blades . REFERENCES Anagnostopoulos, P., ed. Flow-Induced Vibrations in Engineering

Virtual Shaker Testing: Simulation Technology Improves Vibration Test Performance

NASA Technical Reports Server (NTRS)

Ricci, Stefano; Peeters, Bart; Fetter, Rebecca; Boland, Doug; Debille, Jan

2008-01-01

In the field of vibration testing, the interaction between the structure being tested and the instrumentation hardware used to perform the test is a critical issue. This is particularly true when testing massive structures (e.g. satellites), because due to physical design and manufacturing limits, the dynamics of the testing facility often couples with the test specimen one in the frequency range of interest. A further issue in this field is the standard use of a closed loop real-time vibration control scheme, which could potentially shift poles and change damping of the aforementioned coupled system. Virtual shaker testing is a novel approach to deal with these issues. It means performing a simulation which closely represents the real vibration test on the specific facility by taking into account all parameters which might impact the dynamic behavior of the specimen. In this paper, such a virtual shaker testing approach is developed. It consists of the following components: (1) Either a physical-based or an equation-based coupled electro-mechanical lumped parameter shaker model is created. The model parameters are obtained from manufacturer's specifications or by carrying out some dedicated experiments; (2) Existing real-time vibration control algorithm are ported to the virtual simulation environment; and (3) A structural model of the test object is created and after defining proper interface conditions structural modes are computed by means of the well-established Craig-Bampton CMS technique. At this stage, a virtual shaker test has been run, by coupling the three described models (shaker, control loop, structure) in a co-simulation routine. Numerical results have eventually been correlated with experimental ones in order to assess the robustness of the proposed methodology.

Experimental demonstration of 1.5Hz passive isolation system for precision optical payloads

NASA Astrophysics Data System (ADS)

Guan, Xin; Wang, Guang-yuan; Cao, Dong-jing; Tang, Shao-fan; Chen, Xiang; Liang, Lu; Zheng, Gang-tie

2017-11-01

The ground resolution of remote sensing satellite has been raised from hundreds of meters to less than one meter in recent few decades. As a result, the precision optical payload becomes more and more sensitive to structure vibrations of satellite buses. Although these vibrations generally have extremely low magnitude, they can result in significant image quality degradation to an optical payload. The suggestion of using vibration isolators to isolate payload from the satellite bus has been put forward in 1980s'[1]. Recently, WorldView-2 achieved its perfect image quality via using a set of low frequency isolators[2]. Recently, some of the optical payload manufacturers begin to provide vibration isolators as standard parts together with their main products . During the prototype testing of an earth resource satellite, the image of the optical payload was found to jitter for 5 10 pixels due to disturbances transmitted from the satellite bus structure. Test results indicated that the acceleration level of the vibration was of mG magnitude. To solve the problem, a highly sensitive vibration isolation system was developed to reduce the transmission of disturbances. Integrated isolation performance tests showed that the image jitter can be decreased to below 0.3 pixels.

Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: AMSU-A2 METSAT Instrument (S/N 108) Acceptance Level Vibration Tests of Dec 1999/Jan 2000 (S/O 784077, OC-454)

NASA Technical Reports Server (NTRS)

Heffner, R.

2000-01-01

This is the Engineering Test Report, AMSU-A2 METSAT Instrument (S/N 108) Acceptance Level Vibration Test of Dec 1999/Jan 2000 (S/O 784077, OC-454), for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

The effects of visual control whole body vibration exercise on balance and gait function of stroke patients.

PubMed

Choi, Eon-Tak; Kim, Yong-Nam; Cho, Woon-Soo; Lee, Dong-Kyu

2016-11-01

[Purpose] This study aims to verify the effects of visual control whole body vibration exercise on balance and gait function of stroke patients. [Subjects and Methods] A total of 22 stroke patients were randomly assigned to two groups; 11 to the experimental group and 11 to the control group. Both groups received 30 minutes of Neuro-developmental treatment 5 times per week for 4 weeks. The experimental group additionally performed 10 minutes of visual control whole body vibration exercise 5 times per week during the 4 weeks. Balance was measured using the Functional Reach Test. Gait was measured using the Timed Up and Go Test. [Results] An in-group comparison in the experimental group showed significant differences in the Functional Reach Test and Timed Up and Go Test. In comparing the groups, the Functional Reach Test and Timed Up and Go Test of the experimental group were more significantly different compared to the control group. [Conclusion] These results suggest that visual control whole body vibration exercise has a positive effect on the balance and gait function of stroke patients.

FDR Soil Moisture Sensor for Environmental Testing and Evaluation

NASA Astrophysics Data System (ADS)

Linmao, Ye; longqin, Xue; guangzhou, Zhang; haibo, Chen; likuai, Shi; zhigang, Wu; gouhe, Yu; yanbin, Wang; sujun, Niu; Jin, Ye; Qi, Jin

To test the affect of environmental stresses on a adaptability of soil moisture capacitance sensor(FDR) a number of stresses were induced including vibrational shock as well as temperature and humidity through the use of a CH-I constant humidity chamber with variable temperature. A Vibrational platform was used to exam the resistance and structural integrity of the sensor after vibrations simulating the process of using, transporting and handling the sensor. A Impactive trial platform was used to test the resistance and structural integrity of the sensor after enduring repeated mechanical shocks. An CH-I constant humidity chamber with high-low temperature was used to test the adaptability of sensor in different environments with high temperature, low temperature and constant humidity. Otherwise, scope of magnetic force line of sensor was also tested in this paper. Test show:the capacitance type soil moisture sensor spread a feeling machine to bear heat, high wet and low temperature, at bear impact and vibration experiment in pass an examination, is a kind of environment to adapt to ability very strong instrument;Spread a feeling machine moreover electric field strength function radius scope 7 cms.

The NASA/industry design analysis methods for vibrations (DAMVIBS) program - Accomplishments and contributions

NASA Technical Reports Server (NTRS)

Kvaternik, Raymond G.

1991-01-01

A NASA Langley-sponsored rotorcraft structural dynamics program, known as Design Analysis Methods for VIBrationS (DAMVIBS), has been under development since 1984. The objective of this program was to establish the technology base needed by the industry to develop an advanced finite-element-based dynamics design analysis capability for vibrations. Under the program, teams from the four major helicopter manufacturers have formed finite-element models, conducted ground vibration tests, made test/analysis comparisons of both metal and composite airframes, performed 'difficult components' studies on airframes to identify components which need more complete finite-element representation for improved correlation, and evaluated industry codes for computing coupled rotor-airframe vibrations. Studies aimed at establishing the role that structural optimization can play in airframe vibrations design work have also been initiated. Five government/industry meetings were held in connection with these activities during the course of the program. Because the DAMVIBS Program is coming to an end, the fifth meeting included a brief assessment of the program and its benefits to the industry.

The NASA/industry design analysis methods for vibrations (DAMVIBS) program: Accomplishments and contributions

NASA Technical Reports Server (NTRS)

Kvaternik, Raymond G.

1991-01-01

A NASA Langley-sponsored rotorcraft structural dynamics program, known as Design Analysis Methods for VIBrationS (DAMVIBS), has been under development since 1984. The objective of this program was to establish the technology base needed by the industry to develop an advanced finite-element-based dynamics design analysis capability for vibrations. Under the program, teams from the four major helicopter manufacturers have formed finite-element models, conducted ground vibration tests, made test/analysis comparisons of both metal and composite airframes, performed 'difficult components' studies on airframes to identify components which need more complete finite-element representation for improved correlation, and evaluated industry codes for computing coupled rotor-airframe vibrations. Studies aimed at establishing the role that structural optimization can play in airframe vibrations design work have also been initiated. Five government/industry meetings were held in connection with these activities during the course of the program. Because the DAMVIBS Program is coming to an end, the fifth meeting included a brief assessment of the program and its benefits to the industry.

A vibration powered wireless mote on the Forth Road Bridge

NASA Astrophysics Data System (ADS)

Jia, Yu; Yan, Jize; Feng, Tao; Du, Sijun; Fidler, Paul; Soga, Kenichi; Middleton, Campbell; Seshia, Ashwin A.

2015-12-01

The conventional resonant-approaches to scavenge kinetic energy are typically confined to narrow and single-band frequencies. The vibration energy harvester device reported here combines both direct resonance and parametric resonance in order to enhance the power responsiveness towards more efficient harnessing of real-world ambient vibration. A packaged electromagnetic harvester designed to operate in both of these resonant regimes was tested in situ on the Forth Road Bridge. In the field-site, the harvester, with an operational volume of ∼126 cm3, was capable of recovering in excess of 1 mW average raw AC power from the traffic-induced vibrations in the lateral bracing structures underneath the bridge deck. The harvester was integrated off-board with a power conditioning circuit and a wireless mote. Duty- cycled wireless transmissions from the vibration-powered mote was successfully sustained by the recovered ambient energy. This limited duration field test provides the initial validation for realising vibration-powered wireless structural health monitoring systems in real world infrastructure, where the vibration profile is both broadband and intermittent.

A new vibrator to stimulate muscle proprioceptors in fMRI.

PubMed

Montant, Marie; Romaiguère, Patricia; Roll, Jean-Pierre

2009-03-01

Studying cognitive brain functions by functional magnetic resonance imaging (fMRI) requires appropriate stimulation devices that do not interfere with the magnetic fields. Since the emergence of fMRI in the 90s, a number of stimulation devices have been developed for the visual and auditory modalities. Only few devices, however, have been developed for the somesthesic modality. Here, we present a vibration device for studying somesthesia that is compatible with high magnetic field environments and that can be used in fMRI machines. This device consists of a poly vinyl chloride (PVC) vibrator containing a wind turbine and of a pneumatic apparatus that controls 1-6 vibrators simultaneously. Just like classical electromagnetic vibrators, our device stimulates muscle mechanoreceptors (muscle spindles) and generates reliable illusions of movement. We provide the fMRI compatibility data (phantom test), the calibration curve (vibration frequency as a function of air flow), as well as the results of a kinesthetic test (perceived speed of the illusory movement as a function of vibration frequency). This device was used successfully in several brain imaging studies using both fMRI and magnetoencephalography.

A Resonant Synchronous Vibration Based Approach for Rotor Imbalance Detection

NASA Technical Reports Server (NTRS)

Luo, Huangeng; Rodriquez, Hector; Hallman, Darren; Lewicki, David G.

2006-01-01

This paper presents a methodology of detecting rotor imbalances, such as mass imbalance and crack-induced imbalance, using shaft synchronous vibrations. An iterative scheme is developed to identify parameters from measured synchronous vibration data. A detection system is integrated by using state-of-the-art commercial analysis equipment. A laboratory rotor test rig is used to verify the system integration and algorithm validation. A real engine test has been carried out and the results are reported.

Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

NASA Technical Reports Server (NTRS)

Dervan, Jared; Robertson, Brandan; Staab, Lucas; Culberson, Michael; Pellicciotti, Joseph

2014-01-01

The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations referenced in detail in the NESC final report [1] including identified lessons learned to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

NASA Technical Reports Server (NTRS)

Dervan, Jared; Robertson, Brandon; Staab, Lucas; Culberson, Michael; Pellicciotti, Joseph

2014-01-01

The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations referenced in detail in the NESC final report including identified lessons learned to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

KENNEDY SPACE CENTER, FLA. - Framed between palm trees, solid rocket boosters loom above the Mobile Launcher Platform (MLP) as the crawler transporter slowly moves it along the crawlerway. The journey is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - Framed between palm trees, solid rocket boosters loom above the Mobile Launcher Platform (MLP) as the crawler transporter slowly moves it along the crawlerway. The journey is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter has slowly moved the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter has slowly moved the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter is slowly moving the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter is slowly moving the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, out of the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Microelectronics Instrument Products Shock and Vibration Electro-Optics. Section B; Acceptance Data Package

NASA Technical Reports Server (NTRS)

1995-01-01

The motor/encoder (henceforth referred to as the UUT) test sequence began with a baseline functional evaluation, which demonstrated that the motor satisfied the operating torque, cogging torque, winding resistance, and mechanical requirements of SOW. In addition, the encoder electrical requirements were verified, as well as the alignment of the encoder outputs relative to the motor shaft position. There were no discrepancies observed in this portion of the test. The UUT was then exposed to a number of environments, including thermal vacuum, thermal cycling, random and sine vibration, and mechanical shock. During the thermal environments, the performance of the UUT under load was verified at specified points in the cycles, as described in ATP 20049. In addition, the UUT was bench tested between the two thermal environments. No anomalies were observed during the thermal tests. The vibration and shock tests were performed by East-West Technology Corporation, West Babylon, New York. The UUT was delivered to the lab in a sealed vibration fixture in order to maintain the cleanliness levels required by the SOW. In addition, a three ounce load was attached to the motor shaft. The attachment method of this load caused damage to the shaft and bearing during random vibration of S/N 0003 on April 28, 1995, and is described further in NCR 00168.

Threshold Assessment of Gear Diagnostic Tools on Flight and Test Rig Data

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Mosher, Marianne; Huff, Edward M.

2003-01-01

A method for defining thresholds for vibration-based algorithms that provides the minimum number of false alarms while maintaining sensitivity to gear damage was developed. This analysis focused on two vibration based gear damage detection algorithms, FM4 and MSA. This method was developed using vibration data collected during surface fatigue tests performed in a spur gearbox rig. The thresholds were defined based on damage progression during tests with damage. The thresholds false alarm rates were then evaluated on spur gear tests without damage. Next, the same thresholds were applied to flight data from an OH-58 helicopter transmission. Results showed that thresholds defined in test rigs can be used to define thresholds in flight to correctly classify the transmission operation as normal.

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete

PubMed Central

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-01

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study. PMID:29316732

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete.

PubMed

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-08

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study.

Experiments In Characterizing Vibrations Of A Structure

NASA Technical Reports Server (NTRS)

Yam, Yeung; Hadaegh, Fred Y.; Bayard, David S.

1993-01-01

Report discusses experiments conducted to test methods of identification of vibrational and coupled rotational/vibrational modes of flexible structure. Report one in series that chronicle development of integrated system of methods, sensors, actuators, analog and digital signal-processing equipment, and algorithms to suppress vibrations in large, flexible structure even when dynamics of structure partly unknown and/or changing. Two prior articles describing aspects of research, "Autonomous Frequency-Domain Indentification" (NPO-18099), and "Automated Characterization Of Vibrations Of A Structure" (NPO-18141).

Vibration Isolation for Launch of a Space Station Orbital Replacement Unit

NASA Technical Reports Server (NTRS)

Maly, Joseph R.; Sills, Joel W., Jr.; Pendleton, Scott C.; James, George H., III; Mimovich, Mark

2004-01-01

Delivery of Orbital Replacement Units (ORUs) to on-orbit destinations such a the International Space Station (ISS) and the Hubble Space Telescope is an important component of the space program. ORUs are integrated on orbit with space assets to maintain and upgrade functionality. For ORUs comprised of sensitive equipment, the dynamic launch environment drives design and testing requirements, and high frequency random vibrations are generally the cause for failure. Vibration isolation can mitigate the structure-borne vibration environment during launch, and hardware has been developed that can provide a reduced environment for current and future launch environments. Random vibration testing of one ORU to equivalent Space Shuttle launch levels revealed that its qualification and acceptance requirements were exceeded. An isolation system was designed to mitigate the structure-borne launch vibration environment. To protect this ORU, the random vibration levels at 50 Hz must be attenuated by a factor of two and those at higher frequencies even more. Design load factors for Shuttle launch are high, so a metallic load path is needed to maintain strength margins. Isolation system design was performed using a finite element model of the ORU on its carrier with representative disturbance inputs. Iterations on the modelled to an optimized design based on flight proven SoftRide MultiFlex isolators. Component testing has been performed on prototype isolators to validate analytical predictions.

Experimental and numerical study on vibration of the full-revolving propulsion ship stern

NASA Astrophysics Data System (ADS)

Liu, Chang-qing; Che, Chi-dong; Shen, Xiao-han

2015-03-01

In order to solve the severe vibration problems of an ocean engineering ship with a full-revolving propulsion system, the navigation tests, including forced vibration response test and modal test, are carried out in its stern. It is concluded from the comparison of the time-domain waveform and spectrum from different measurement points that three main factors lead to a high-level stern vibration. Firstly, the specific dynamic stiffness of a water tank is relatively small compared with its neighbor hold, which makes it act like a vibration isolator preventing vibrational energy transmitting to the main hold. Secondly, there exists high-density local modes in the working frequency range of the main engine and thus the local resonance occurs. Thirdly, the abnormal engagement of gears caused by the large deflection of the shaft bearing due to its low mounting rigidity leads to violent extra impulse excitations at high speeds. Then the modification against the dynamic defects is given by simply improving the specific stiffness of the water tanks. And the effect is validated by the FEM calculation. Some important experience is obtained with the problems being solved, which is useful in the design of ships with the same propulsion system. It is also believed that the dynamic consideration is as important as the static analysis for the ships, and that most of the vibration problems may be avoided with a proper acoustic design.

Adaptive PI control strategy for flat permanent magnet linear synchronous motor vibration suppression

NASA Astrophysics Data System (ADS)

Meng, Fanwei; Liu, Chengying; Li, Zhijun; Wang, Liping

2013-01-01

Due to low damping ratio, flat permanent magnet linear synchronous motor's vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor's motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature-axis current under typical load. Adaptive PI control strategy can effectively suppress the flat permanent magnet linear synchronous motor's vibration without affecting the motor's performance.

Vibration Testing of the Pluto/New Horizons Radioisotope Thermoelectric Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles D. Griffin

The Radioisotopic Thermal Generator (RTG) for the Pluto/New Horizons spacecraft was subjected to a flight dynamic acceptance test to demonstrate that it would perform successfully following launch. Seven RTGs of this type had been assembled and tested at Mound, Ohio from 1984 to 1997. This paper chronicles major events in establishing a new vibration test laboratory at the Idaho National Laboratory and the nineteen days of dynamic testing.

High-Temperature Modal Survey of a Hot-Structure Control Surface

NASA Technical Reports Server (NTRS)

Spivey, Natalie D.

2011-01-01

Ground vibration tests are routinely conducted for supporting flutter analysis for subsonic and supersonic vehicles; however, for hypersonic vehicles, thermoelastic vibration testing techniques are neither well established nor routinely performed. New high-temperature material systems, fabrication technologies and high-temperature sensors expand the opportunities to develop advanced techniques for performing ground vibration tests at elevated temperatures. When high-temperature materials, which increase in stiffness when heated, are incorporated into a hot-structure that contains metallic components that decrease in stiffness when heated, the interaction between those materials can affect the hypersonic flutter analysis. A high-temperature modal survey will expand the research database for hypersonics and improve the understanding of this dual-material interaction. This report discusses the vibration testing of the carbon-silicon carbide Ruddervator Subcomponent Test Article, which is a truncated version of a full-scale hot-structure control surface. Two series of room-temperature modal test configurations were performed in order to define the modal characteristics of the test article during the elevated-temperature modal survey: one with the test article suspended from a bungee cord (free-free) and the second with it mounted on the strongback (fixed boundary). Testing was performed in the NASA Dryden Flight Research Center Flight Loads Laboratory Large Nitrogen Test Chamber.

Return to Flying Duties Following Centrifuge or Vibration Exposures

NASA Technical Reports Server (NTRS)

Scheuring, Richard A.; Clarke, Jonathan; Jones, Jeffrey A.

2009-01-01

Introduction: In an effort to determine the human performance limits for vibration in spacecraft being developed by NASA, astronauts were evaluated during a simulated launch profile in a centrifuge/vibration environment and separate vibration-only simulation. Current USAF and Army standards for return to flight following centrifuge exposures require 12-24 hours to pass before a crewmember may return to flying duties. There are no standards on vibration exposures and return to flying duties. Based on direct observation and provocative neurological testing of the astronauts, a new standard for return to flying duties following centrifuge and/or vibration exposures was established. Methods: 13 astronaut participants were exposed to simulated launch profiles in a + 3.5 Gx bias centrifuge/vibration environment and separately on a vibration table at the NASA-Ames Research Center. Each subject had complete neurological evaluations pre- and post-exposure for the centrifuge/vibration runs with the NASA neurological function rating scale (NFRS). Subjects who participated in the vibration-only exposures had video oculography performed with provocative maneuvers in addition to the NFRS. NFRS evaluations occurred immediately following each exposure and at 1 hour post-run. Astronauts who remained symptomatic at 1 hour had repeat NFRS performed at 1 hour intervals until the crewmember was asymptomatic. Results: Astronauts in the centrifuge/vibration study averaged a 3-5 point increase in NFRS scores immediately following exposure but returned to baseline 3 hours post-run. Subjects exposed to the vibration-only simulation had a 1-3 point increase following exposure and returned to baseline within 1-2 hours. Pre- and post- vibration exposure video oculography did not reveal any persistent ocular findings with provocative testing 1 hour post-exposure. Discussion: Based on direct observations and objective measurement of neurological function in astronauts following simulated launch profiles, asymptomatic individuals are allowed to return to flying duties within 3 hours following centrifuge/vibration and 2 hours after vibration-only exposures.

Adaptations of mouse skeletal muscle to low intensity vibration training

PubMed Central

McKeehen, James N.; Novotny, Susan A.; Baltgalvis, Kristen A.; Call, Jarrod A.; Nuckley, David J.; Lowe, Dawn A.

2013-01-01

Purpose We tested the hypothesis that low intensity vibration training in mice improves contractile function of hindlimb skeletal muscles and promotes exercise-related cellular adaptations. Methods We subjected C57BL/6J mice to 6 wk, 5 d·wk−1, 15 min·d−1 of sham or low intensity vibration (45 Hz, 1.0 g) while housed in traditional cages (Sham-Active, n=8; Vibrated-Active, n=10) or in small cages to restrict physical activity (Sham-Restricted, n=8; Vibrated-Restricted, n=8). Contractile function and resistance to fatigue were tested in vivo (anterior and posterior crural muscles) and ex vivo on the soleus muscle. Tibialis anterior and soleus muscles were evaluated histologically for alterations in oxidative metabolism, capillarity, and fiber types. Epididymal fat pad and hindlimb muscle masses were measured. Two-way ANOVAs were used to determine effects of vibration and physical inactivity. Results Vibration training resulted in a 10% increase in maximal isometric torque (P=0.038) and 16% faster maximal rate of relaxation (P=0.030) of the anterior crural muscles. Posterior crural muscles were unaffected by vibration, with the exception of greater rates of contraction in Vibrated-Restricted mice compared to Vibrated-Active and Sham-Restricted mice (P=0.022). Soleus muscle maximal isometric tetanic force tended to be greater (P=0.057) and maximal relaxation was 20% faster (P=0.005) in Vibrated compared to Sham mice. Restriction of physical activity induced muscle weakness but was not required for vibration to be effective in improving strength or relaxation. Vibration training did not impact muscle fatigability or any indicator of cellular adaptation investigated (P≥0.431). Fat pad but not hindlimb muscle masses were affected by vibration training. Conclusion Vibration training in mice improved muscle contractility, specifically strength and relaxation rates, with no indication of adverse effects to muscle function or cellular adaptations. PMID:23274599

Journal of Engineering Thermophysics (Selected Articles),

DTIC Science & Technology

1983-05-13

compressor, prediction of unsteady vibration , and prevention of unsteady vibration . This test was undergone on a turbojet engine. The paper stresses the...induce unsteady engine vibration . While studying the effect of inlet anomaly and variation of the first stage nozzle area of the turbine, the engine...constant revolution speed curve until unsteady vibration or stall appeared. In studying the influence of the starting sequence, starting was

Concorde noise-induced building vibrations, John F. Kennedy International Airport

NASA Technical Reports Server (NTRS)

Mayes, W. H.; Deloach, R.; Stephens, D. G.; Cawthorn, J. M.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Miller, W. T.; Ward, D. W.

1978-01-01

The outdoor/indoor noise levels and associated vibration levels resulting from aircraft and nonaircraft events were recorded at eight homesites and a school. In addition, limited subjective tests were conducted to examine the human detection/annoyance thresholds for building vibration and rattle caused by aircraft noise. Presented herein are the majority of the window and wall vibration data recorded during Concorde and subsonic aircraft overflights.

The development of sine vibration test requirements for Viking lander capsule components

NASA Technical Reports Server (NTRS)

Barrett, S.

1974-01-01

In connection with the Viking project for exploring the planet Mars, two identical spacecraft, each consisting of an orbiter and a lander, will be launched in the third quarter of 1975. Upon arrival at the planet, the Viking lander will separate from the Viking orbiter and descend to a soft landing at a selected site on the Mars surface. It was decided to perform a sine vibration test on the Viking spacecraft, in its launch configuration, to qualify it for the booster-induced transient-dynamic environment. It is shown that component-level testing is a cost- and schedule-effective prerequisite to the system-level, sine-vibration test sequences.

Ground vibration test of the XV-15 Tiltrotor Research Aircraft and pretest predictions

NASA Technical Reports Server (NTRS)

Studebaker, Karen; Abrego, Anita

1994-01-01

The first comprehensive ground vibration survey was performed on the XV-15 Tiltrotor Research Aircraft to measure the vibration modes of the airframe and to provide data critical for determining whirl flutter stability margins. The aircraft was suspended by the wings with bungee cords and cables. A NASTRAN finite element model was used in the design of the suspension system to minimize its interference with the wing modes. The primary objective of the test was to measure the dynamic characteristics of the wings and pylons for aeroelastic stability analysis. In addition, over 130 accelerometers were placed on the airframe to characterize the fuselage, wing, and tail vibration. Pretest predictions were made with the NASTRAN model as well as correlations with the test data. The results showed that the suspension system provided the isolation necessary for modal measurements.

Environmental test of the BGO calorimeter for DArk Matter Particle Explorer

NASA Astrophysics Data System (ADS)

Hu, Yi-Ming; Chang, Jin; Chen, Deng-Yi; Guo, Jian-Hua; Zhang, Yun-Long; Feng, Chang-Qing

2016-11-01

DArk Matter Particle Explorer (DAMPE) is the first Chinese astronomical satellite, successfully launched on Dec. 17 2015. As the most important payload of DAMPE, the BGO calorimeter contains 308 bismuth germanate crystals, with 616 photomultiplier tubes, one coupled to each end of every crystal. Environmental tests have been carried out to explore the environmental adaptability of the flight model of the BGO calorimeter. In this work we report the results of the vibration tests. During the vibration tests, no visible damage occurred in the mechanical assembly. After random or sinusoidal vibrations, the change of the first order natural frequency of BGO calorimeter during the modal surveys is less than 5%. The shift ratio of Most Probable Value of MIPs changes in cosmic-ray tests are shown, the mean value of which is about -4%. The comparison of results of cosmic-ray tests before and after the vibration shows no significant change in the performance of the BGO calorimeter. All these results suggest that the calorimeter and its structure have passed through the environment tests successfully. Supported by National Natural Science Foundation of China (11203090, 11003051, 11273070) and Strategic Priority Research Program on Space Science of Chinese Academy of Sciences (XDA04040202)

Performance and Environmental Test Results of the High Voltage Hall Accelerator Engineering Development Unit

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Haag, Thomas; Huang, Wensheng; Shastry, Rohit; Pinero, Luis; Peterson, Todd; Mathers, Alex

2012-01-01

NASA Science Mission Directorate's In-Space Propulsion Technology Program is sponsoring the development of a 3.5 kW-class engineering development unit Hall thruster for implementation in NASA science and exploration missions. NASA Glenn and Aerojet are developing a high fidelity high voltage Hall accelerator that can achieve specific impulse magnitudes greater than 2,700 seconds and xenon throughput capability in excess of 300 kilograms. Performance, plume mappings, thermal characterization, and vibration tests of the high voltage Hall accelerator engineering development unit have been performed. Performance test results indicated that at 3.9 kW the thruster achieved a total thrust efficiency and specific impulse of 58%, and 2,700 sec, respectively. Thermal characterization tests indicated that the thruster component temperatures were within the prescribed material maximum operating temperature limits during full power thruster operation. Finally, thruster vibration tests indicated that the thruster survived the 3-axes qualification full-level random vibration test series. Pre and post-vibration test performance mappings indicated almost identical thruster performance. Finally, an update on the development progress of a power processing unit and a xenon feed system is provided.

Ground vibration test of the laminar flow control JStar airplane

NASA Technical Reports Server (NTRS)

Kehoe, M. W.; Cazier, F. W., Jr.; Ellison, J. F.

1985-01-01

A ground vibration test was conducted on a Lockheed JetStar airplane that had been modified for the purpose of conducting laminar flow control experiments. The test was performed prior to initial flight flutter tests. Both sine-dwell and single-point-random excitation methods were used. The data presented include frequency response functions and a comparison of mode frequencies and mode shapes from both methods.

NASA Dryden's F-15B aircraft with the Gulfstream Quiet Spike sonic boom mitigator attached undergoes ground vibration testing in preparation for test flights

NASA Image and Video Library

2006-05-01

NASA Dryden's F-15B testbed aircraft with the Gulfstream Quiet Spike sonic boom mitigator attached undergoes ground vibration testing in preparation for test flights. The project seeks to verify the structural integrity of the multi-segmented, articulating spike attachment designed to reduce and control a sonic boom.

Vibration, acoustic, and shock design and test criteria for components on the Solid Rocket Boosters (SRB), Lightweight External Tank (LWT), and Space Shuttle Main Engines (SSME)

NASA Technical Reports Server (NTRS)

1984-01-01

The vibration, acoustics, and shock design and test criteria for components and subassemblies on the space shuttle solid rocket booster (SRB), lightweight tank (LWT), and main engines (SSME) are presented. Specifications for transportation, handling, and acceptance testing are also provided.

The Shock Vibration Bulletin. Part 3. Isolation and Damping, Vibration Test Criteria, and Vibration Analysis and Test

DTIC Science & Technology

1987-01-01

PULLERS AND SEPARATION JOINTS M. J. Evans and V. H. Neubert , The Pennsylvania State Univevsity, University Partk, PA, and L. J. Bement, NASA, Langley...Laboratory, Wshingt’,, DC Wednesday Nondevelopment Mr. James W. Daniel, Mr. Paul Hahn, 15 October, A.M. Items Workshop, U.S. Army Missile Martl.n Marietta...Session i, Command, Orlando Aerospace, Methods Redstone Arseral, AL Orlando, FL Wednesday Structural Mr. Etanley Barrett, Hr. W. Paul Dunn, 15

Random vibration (stress screening) of printed wiring assemblies

NASA Technical Reports Server (NTRS)

Bastien, Gilbert J.

1988-01-01

The results of a random vibration test screening (RVSS) study of the determination of the upper and lower vibration limits on printed wiring assemblies (PWA) are summarized. The study results are intended to serve as a guide for engineers and designers who make decisions on PWA features that need to withstand the stresses of dynamic testing and screening. The maximum allowable PWA deflection, G levels, and PSD levels are compared to the expected or actual levels to determine if deleterious effects will occur.

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

Study of passenger subjective response to ideal and real-vehicle vibration environments

NASA Technical Reports Server (NTRS)

Kirby, R. H.; Mikulka, P. J.

1975-01-01

The stimulus received by subjects tested on the passenger ride quality apparatus (PRQA) is defined. Additional analyses on the data collected from field tests using buses, were conducted to assess the relation between subjective ratings of ride quality and vibrations measured on the buses, and to better define the vibration stimulus measured in the field. The relation of subjective evaluation of simulations of bus rides produced by the DRQA to subjective evaluations of the actual bus rides is discussed. The relative contribution of the seat and floor vibration to human comfort in a simulated aircraft ride environment is discussed along with the determination of equal comfort curves through magnitude estimation.

Vibration and noise characteristics of an elevated box girder paved with different track structures

NASA Astrophysics Data System (ADS)

Li, Xiaozhen; Liang, Lin; Wang, Dangxiong

2018-07-01

The vibration and noise of elevated concrete box girders (ECBGs) are now among the most concerned issues in the field of urban rail transit (URT) systems. The track structure, belonging to critical load-transfer components, directly affects the characteristics of loading transmission into bridge, as well as the noise radiation from such system, which further determines the reduction of vibration and noise in ECBGs significantly. In order to investigate the influence of different track structures on the vibration and structure-borne noise of ECBGs, a frequency-domain theoretical model of vehicle-track coupled system, taking into account the effect of multiple wheels, is firstly established in the present work. The analysis of track structures focuses on embedded sleepers, trapezoidal sleepers, and steel-spring floating slabs (SSFS). Next, a vibration and noise field test was performed, with regard to a 30 m simple supported ECBG (with the embedded-sleeper track structure) of an URT system. Based on the tested results, two numerical models, involving a finite element model for the vibration analysis, as well as a statistical energy analysis (SEA) model for the prediction of the noise radiation, are established and validated. The results of the numerical simulations and the field tests are well matched, which offers opportunities to predict the vibration and structure-borne noise of ECBGs by the proposed modelling methodology. From the comparison between the different types of track structures, the spatial distribution and reduction effect of vibration and noise are lastly studied. The force applied on ECBG is substantially determined by both the wheel-rail force (external factor) and the transmission rate of track structure (internal factor). The SSFS track is the most effective for vibration and noise reduction of ECBGs, followed in descending order by the trapezoidal-sleeper and embedded-sleeper tracks. The above result provides a theoretical basis for the vibration and noise reduction design of urban rail transit systems.

Measurement of ground and nearby building vibration and noise induced by trains in a metro depot.

PubMed

Zou, Chao; Wang, Yimin; Wang, Peng; Guo, Jixing

2015-12-01

Metro depots are where subway trains are parked and where maintenance is carried out. They usually occupy the largest ground areas in metro projects. Due to land utilization problems, Chinese cities have begun to develop over-track buildings above metro depots for people's life and work. The frequently moving trains, when going into and out of metro depots, can cause excessive vibration and noise to over-track buildings and adversely affect the living quality of the building occupants. Considering the current need of reliable experimental data for the construction of metro depots, field measurements of vibration and noise on the ground and inside a nearby 3-story building subjected to moving subway trains were conducted in a metro depot at Guangzhou, China. The amplitudes and frequency contents of velocity levels were quantified and compared. The composite A-weighted equivalent sound levels and maximum sound levels were captured. The predicted models for vibration and noise of metro depot were proposed based on existing models and verified. It was found that the vertical vibrations were significantly greater than the horizontal vibrations on the ground and inside the building near the testing line. While at the throat area, the horizontal vibrations near the curved track were remarkably greater than the vertical vibrations. The attenuation of the vibrations with frequencies above 50 Hz was larger than the ones below 50 Hz, and the frequencies of vibration transmitting to adjacent buildings were mainly within 10-50 Hz. The largest equivalent sound level generated in the throat area was smaller than the testing line one, but the instantaneous maximum sound level induced by wheels squeal, contact between wheels and rail joints as well as turnout was close to or even greater than the testing line one. The predicted models gave a first estimation for design and assessment of newly built metro depots. Copyright © 2015 Elsevier B.V. All rights reserved.

Advanced superposition methods for high speed turbopump vibration analysis

NASA Technical Reports Server (NTRS)

Nielson, C. E.; Campany, A. D.

1981-01-01

The small, high pressure Mark 48 liquid hydrogen turbopump was analyzed and dynamically tested to determine the cause of high speed vibration at an operating speed of 92,400 rpm. This approaches the design point operating speed of 95,000 rpm. The initial dynamic analysis in the design stage and subsequent further analysis of the rotor only dynamics failed to predict the vibration characteristics found during testing. An advanced procedure for dynamics analysis was used in this investigation. The procedure involves developing accurate dynamic models of the rotor assembly and casing assembly by finite element analysis. The dynamically instrumented assemblies are independently rap tested to verify the analytical models. The verified models are then combined by modal superposition techniques to develop a completed turbopump model where dynamic characteristics are determined. The results of the dynamic testing and analysis obtained are presented and methods of moving the high speed vibration characteristics to speeds above the operating range are recommended. Recommendations for use of these advanced dynamic analysis procedures during initial design phases are given.

The influence of flywheel micro vibration on space camera and vibration suppression

NASA Astrophysics Data System (ADS)

Li, Lin; Tan, Luyang; Kong, Lin; Wang, Dong; Yang, Hongbo

2018-02-01

Studied the impact of flywheel micro vibration on a high resolution optical satellite that space-borne integrated. By testing the flywheel micro vibration with six-component test bench, the flywheel disturbance data is acquired. The finite element model of the satellite was established and the unit force/torque were applied at the flywheel mounting position to obtain the micro vibration data of the camera. Integrated analysis of the data of the two parts showed that the influence of flywheel micro vibration on the camera is mainly concentrated around 60-80 Hz and 170-230 Hz, the largest angular displacement of the secondary mirror along the optical axis direction is 0.04″ and the maximum angular displacement vertical to optical axis is 0.032″. After the design and installation of vibration isolator, the maximum angular displacement of the secondary mirror is 0.011″, the decay rate of root mean square value of the angular displacement is more than 50% and the maximum is 96.78%. The whole satellite was suspended to simulate the boundary condition on orbit; the imaging experiment results show that the image motion caused by the flywheel micro vibrationis less than 0.1 pixel after installing the vibration isolator.

Transient vibration analytical modeling and suppressing for vibration absorber system under impulse excitation

NASA Astrophysics Data System (ADS)

Wang, Xi; Yang, Bintang; Yu, Hu; Gao, Yulong

2017-04-01

The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.

Vibration test of 1/5 scale H-II launch vehicle

NASA Astrophysics Data System (ADS)

Morino, Yoshiki; Komatsu, Keiji; Sano, Masaaki; Minegishi, Masakatsu; Morita, Toshiyuki; Kohsetsu, Y.

In order to predict dynamic loads on the newly designed Japanese H-II launch vehicle, the adequacy of prediction methods has been assessed by the dynamic scale model testing. The three-dimensional dynamic model was used in the analysis to express coupling effects among axial, lateral (pitch and yaw) and torsional vibrations. The liquid/tank interaction was considered by use of a boundary element method. The 1/5 scale model of the H-II launch vehicle was designed to simulate stiffness and mass properties of important structural parts, such as core/SRB junctions, first and second stage Lox tanks and engine mount structures. Modal excitation of the test vehicle was accomplished with 100-1000 N shakers which produced random or sinusoidal vibrational forces. The vibrational response of the test vehicle was measured at various locations with accelerometers and pressure sensor. In the lower frequency range, corresmpondence between analysis and experiment was generally good. The basic procedures in analysis seem to be adequate so far, but some improvements in mathematical modeling are suggested by comparison of test and analysis.

Fatigue Damage Spectrum calculation in a Mission Synthesis procedure for Sine-on-Random excitations

NASA Astrophysics Data System (ADS)

Angeli, Andrea; Cornelis, Bram; Troncossi, Marco

2016-09-01

In many real-life environments, certain mechanical and electronic components may be subjected to Sine-on-Random vibrations, i.e. excitations composed of random vibrations superimposed on deterministic (sinusoidal) contributions, in particular sine tones due to some rotating parts of the system (e.g. helicopters, engine-mounted components,...). These components must be designed to withstand the fatigue damage induced by the “composed” vibration environment, and qualification tests are advisable for the most critical ones. In the case of an accelerated qualification test, a proper test tailoring which starts from the real environment (measured vibration signals) and which preserves not only the accumulated fatigue damage but also the “nature” of the excitation (i.e. sinusoidal components plus random process) is important to obtain reliable results. In this paper, the classic time domain approach is taken as a reference for the comparison of different methods for the Fatigue Damage Spectrum (FDS) calculation in case of Sine-on-Random vibration environments. Then, a methodology to compute a Sine-on-Random specification based on a mission FDS is proposed.

A noise control package for vibrating screens1),2)

PubMed Central

Lowe, M. Jenae; Yantek, David S.; Yang, Junyi; Schuster, Kevin C.; Mechling, Jessie J.

2015-01-01

Hearing loss was the second-most common illness reported to the Mine Safety and Health Administration (MSHA) in 2009. Furthermore, between 2000 and 2010, 30% of all noise-related injury complaints reported to MSHA were for coal preparation plant employees. Previous National Institute for Occupational Safety and Health (NIOSH) studies have shown that vibrating screens are key noise sources to address in order to reduce coal preparation plant noise. In response, NIOSH researchers have developed a suite of noise controls for vibrating screens consisting of constrained layer damping (CLD) treatments, a tuned mechanism suspension, an acoustic enclosure, and spring inserts. Laboratory testing demonstrates that this noise control suite reduces the A-weighted sound power level of the vibrating screen by 6 dB. To provide a comparison to laboratory results and prove durability, field testing of two noise controls was performed on a vibrating screen in a working coal preparation plant. The spring inserts and CLD treatments were selected due to their ease of installation and practicability. Field testing of these controls yielded reductions that were comparable to laboratory results. PMID:26257468

Validation of Methods to Predict Vibration of a Panel in the Near Field of a Hot Supersonic Rocket Plume

NASA Technical Reports Server (NTRS)

Bremner, P. G.; Blelloch, P. A.; Hutchings, A.; Shah, P.; Streett, C. L.; Larsen, C. E.

2011-01-01

This paper describes the measurement and analysis of surface fluctuating pressure level (FPL) data and vibration data from a plume impingement aero-acoustic and vibration (PIAAV) test to validate NASA s physics-based modeling methods for prediction of panel vibration in the near field of a hot supersonic rocket plume. For this test - reported more fully in a companion paper by Osterholt & Knox at 26th Aerospace Testing Seminar, 2011 - the flexible panel was located 2.4 nozzle diameters from the plume centerline and 4.3 nozzle diameters downstream from the nozzle exit. The FPL loading is analyzed in terms of its auto spectrum, its cross spectrum, its spatial correlation parameters and its statistical properties. The panel vibration data is used to estimate the in-situ damping under plume FPL loading conditions and to validate both finite element analysis (FEA) and statistical energy analysis (SEA) methods for prediction of panel response. An assessment is also made of the effects of non-linearity in the panel elasticity.

Assessment of vibration produced by the grinders used in the shipbuilding industry of Korea.

PubMed

Park, Hee-Sok; Yim, Sang-Hyuk

2007-04-01

The objective of this study is to estimate the prevalence of finger blanching among the workers in a shipyard of Korea using the dose-response relationship suggested by ISO 5349. The characteristics of vibration exposure produced by six types of grinders were investigated. Vibration measurement was made under the real work conditions. Exposure time was estimated by questionnaire and direct observation. In addition, cold provocation tests were performed, and the results from the tests were compared with the estimated prevalence. As a result, 4 hour-energy-equivalent frequency-weighted accelerations of the finishing grinding (FG) and the prepainting grinding (PG) jobs were 6.23 m/s(2) and 13.39 m/s(2), respectively. The mean exposure time for holding the grinders was 4.64 h per day. Using the ISO 5349 method, it was predicted that after exposure to vibration for 10.79 yr, about a half of the FG workers could develop finger blanching. For the PG workers, the corresponding predicted latency was 5.02 yr. A discrepancy was found between the results from the ISO relationship and those from the cold provocation tests. A linear regression model was suggested employing vibration acceleration and vibration exposure time as explanatory variables for vascular dysfunction.

Progress in industrial holography in France

NASA Astrophysics Data System (ADS)

Smigielski, Paul

1992-01-01

Industrial applications of holography in France are briefly reviewed. Particular attention is given to nondestructive testing of helicopter blades at Aerospatiale Central Laboratory, the use of holography at Renault for car-engine vibration study, vibration characterization of turbo-jet engine components at SNECMA, and vibration analysis of plates in an industrial hemodynamic tunnel.

Shake Test Results and Dynamic Calibration Efforts for the Large Rotor Test Apparatus

NASA Technical Reports Server (NTRS)

Russell, Carl R.

2014-01-01

A shake test of the Large Rotor Test Apparatus (LRTA) was performed in an effort to enhance NASAscapability to measure dynamic hub loads for full-scale rotor tests. This paper documents the results of theshake test as well as efforts to calibrate the LRTA balance system to measure dynamic loads.Dynamic rotor loads are the primary source of vibration in helicopters and other rotorcraft, leading topassenger discomfort and damage due to fatigue of aircraft components. There are novel methods beingdeveloped to reduce rotor vibrations, but measuring the actual vibration reductions on full-scale rotorsremains a challenge. In order to measure rotor forces on the LRTA, a balance system in the non-rotatingframe is used. The forces at the balance can then be translated to the hub reference frame to measure therotor loads. Because the LRTA has its own dynamic response, the balance system must be calibrated toinclude the natural frequencies of the test rig.

Assessment of a Cavity to Optimize Ultrasonic Efficiency to Remove Intraradicular Posts.

PubMed

Graça, Izabela Araujo Aguiar; Sponchiado Júnior, Emílio Carlos; Marques, André Augusto Franco; de Moura Martins, Leandro; Garrido, Ângela Delfina Bittencourt

2017-08-01

The study assessed an in vitro protocol for the removal of cast metal posts using ultrasonic vibration in multirooted teeth by drilling a cavity in the coronal portion of the post followed by ultrasound application in the cavity. Forty endodontically treated molars received intraradicular cast posts and were divided into 4 groups according to the removal protocol: the control group, no cavity and no ultrasonic vibration; the ultrasonic group, no cavity and ultrasonic vibration in the coronal portion of the core; the cavity group, a cavity in the core and no ultrasonic vibration; and the cavity ultrasonic group, a cavity in the core and ultrasonic vibration inside the cavity. The traction test was performed on all samples using a universal testing machine (EMIC DL-2000; EMIC Equipamentos e Sistemas de Ensaio LTDA, São José dos Pinhais, PR, Brazil) at a speed of 1 mm/min, obtaining values in Newtons. The data were statistically analyzed using analysis of variance and the Tukey-Kramer test (P < .05). The results showed statistically significant differences between the tested groups (control group = 322.74 N, ultrasonic group = 283.09 N, cavity group = 244.00 N, and cavity ultrasonic group = 237.69 N). The lowest mean strength was found in the group that received ultrasonic vibration inside the cavity. Preparing a cavity in the coronal core followed by ultrasonic vibration reduces the traction force required for removal. The removal protocol was effective for removing posts in multirooted teeth cemented with zinc phosphate. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Study of T53 engine vibration

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.

The Shock and Vibration Bulletin. Part 3. Acoustic and Vibration Testing, Impact and Blast

DTIC Science & Technology

1976-08-01

Research Institute, San Antonio, Texas DESIGN OF A BLAST LOAD GENERATOR FOR OVERPRESSURE TESTING .................................. 261I P. Lieberman...Mathews and B. W. Duggin, Sandia Laboratories, Albuquerque, New Mexico ESTIMATION OF SHIP SHOCK PARAMETERS FOR CONSISTENT DESIGN AND TEST SPECIFICATION G. C...Seattle, Washington COMPONENT TESTING OF LIQUID SHOCK ISOLATORS AND ELASTOMERS IN SUPPORT OF RECENT SHOCK ISOLATION SYSTEM DESIGNS AJ.IP. Ashley, Boeing

Synchronous meteorological satellite system description document, volume 3

NASA Technical Reports Server (NTRS)

Pipkin, F. B.

1971-01-01

The structural design, analysis, and mechanical integration of the synchronous meteorological satellite system are presented. The subjects discussed are: (1) spacecraft configuration, (2) structural design, (3) static load tests, (4) fixed base sinusoidal vibration survey, (5) flight configuration sinusoidal vibration tests, (6) spacecraft acoustic test, and (7) separation and shock test. Descriptions of the auxiliary propulsion subsystem, the apogee boost motor, communications system, and thermal control subsystem are included.

14 CFR 25.907 - Propeller vibration and fatigue.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) The applicant must determine the magnitude of the propeller vibration stresses or loads, including any stress peaks and resonant conditions, throughout the operational envelope of the airplane by either: (1) Measurement of stresses or loads through direct testing or analysis based on direct testing of the propeller...

14 CFR 25.907 - Propeller vibration and fatigue.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) The applicant must determine the magnitude of the propeller vibration stresses or loads, including any stress peaks and resonant conditions, throughout the operational envelope of the airplane by either: (1) Measurement of stresses or loads through direct testing or analysis based on direct testing of the propeller...

14 CFR 25.907 - Propeller vibration and fatigue.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) The applicant must determine the magnitude of the propeller vibration stresses or loads, including any stress peaks and resonant conditions, throughout the operational envelope of the airplane by either: (1) Measurement of stresses or loads through direct testing or analysis based on direct testing of the propeller...

Acute effects of muscle vibration on sensorimotor integration.

PubMed

Lapole, Thomas; Tindel, Jérémy

2015-02-05

Projections from the somesthetic cortex are believed to be involved in the modulation of motor cortical excitability by muscle vibration. The aim of the present pilot study was to analyse the effects of a vibration intervention on short-latency afferent inhibition (SAI), long-latency afferent inhibition (LAI), and afferent facilitation (AF), three intracortical mechanisms reflecting sensorimotor integration. Abductor pollicis brevis (APB) SAI, AF and LAI were investigated on 10 subjects by conditioning test transcranial magnetic stimulation pulses with median nerve electrical stimulation at inter-stimuli intervals in the range 15-25 ms, 25-60 ms, and 100-200 ms, respectively. Test motor evoked potentials (MEPs) were compared to unconditioned MEPs. Measurements were performed before and just after 15 min of vibration applied to the muscle belly of APB at a frequency of 80 Hz. SAI and LAI responses were significantly reduced compared to unconditioned test MEPs (P=0.039 and P<0.001, respectively). AF MEP amplitude was greater than SAI and LAI one (P=0.009 and P=0.004, respectively), but not different from test MEP (P=0.511). There was no significant main effect of vibration (P=0.905). However, 4 subjects were clearly identified as responders. Their mean vibration-induced increase was 324 ± 195% in APB SAI MEP amplitude, and 158 ± 53% and 319 ± 80% in AF and LAI, respectively. Significant differences in SAI, AF and LAI vibration-induced changes were found for responders when compared to non-responders (P=0.019, P=0.038, and P=0.01, respectively). A single session of APB vibration may increase sensorimotor integration, via decreased inhibition and increased facilitation. However, such results were not observed for all subjects, suggesting that other factors (such as attention to the sensory inputs) may have played a role. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (on the horizon) and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (on the horizon) and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (framed between the boosters), and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (framed between the boosters), and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, along the crawlerway in support of engineering analysis vibration tests on the crawler and MLP. In the distance, at left, is Launch Pad 39A. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, along the crawlerway in support of engineering analysis vibration tests on the crawler and MLP. In the distance, at left, is Launch Pad 39A. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, crawls away from the Vehicle Assembly Building in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, crawls away from the Vehicle Assembly Building in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch away from the Vehicle Assembly Building (VAB) in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch away from the Vehicle Assembly Building (VAB) in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Carrying a set of twin solid rocket boosters, the crawler transporter slowly moves the Mobile Launcher Platform (MLP) past the NASA-KSC News Center where the U.S. flag flies daily. The journey is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - Carrying a set of twin solid rocket boosters, the crawler transporter slowly moves the Mobile Launcher Platform (MLP) past the NASA-KSC News Center where the U.S. flag flies daily. The journey is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Investigation of Gearbox Vibration Transmission Paths on Gear Condition Indicator Performance

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Islam, AKM Anwarul; Feldman, Jason; Larsen, Chris

2013-01-01

Helicopter health monitoring systems use vibration signatures generated from damaged components to identify transmission faults. For damaged gears, these signatures relate to changes in dynamics due to the meshing of the damaged tooth. These signatures, referred to as condition indicators (CI), can perform differently when measured on different systems, such as a component test rig, or a full-scale transmission test stand, or an aircraft. These differences can result from dissimilarities in systems design and environment under dynamic operating conditions. The static structure can also filter the response between the vibration source and the accelerometer, when the accelerometer is installed on the housing. To assess the utility of static vibration transfer paths for predicting gear CI performance, measurements were taken on the NASA Glenn Spiral Bevel Gear Fatigue Test Rig. The vibration measurements were taken to determine the effect of torque, accelerometer location and gearbox design on accelerometer response. Measurements were taken at the housing and compared while impacting the gear set near mesh. These impacts were made at gear mesh to simulate gear meshing dynamics. Data measured on a helicopter gearbox installed in a static fixture were also compared to the test rig. The behavior of the structure under static conditions was also compared to CI values calculated under dynamic conditions. Results indicate that static vibration transfer path measurements can provide some insight into spiral bevel gear CI performance by identifying structural characteristics unique to each system that can affect specific CI response.

KENNEDY SPACE CENTER, FLA. - As the crawler transporter slowly moves the Mobile Launcher Platform (MLP) out of the Vehicle Assembly Building, the two solid rocket boosters on top are framed in the doorway. The move is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - As the crawler transporter slowly moves the Mobile Launcher Platform (MLP) out of the Vehicle Assembly Building, the two solid rocket boosters on top are framed in the doorway. The move is in support of engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - As the crawler transporter slowly moves the Mobile Launcher Platform (MLP) out of the Vehicle Assembly Building, the driver of the front control cab can be seen. The MLP is carrying two solid rocket boosters for engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - As the crawler transporter slowly moves the Mobile Launcher Platform (MLP) out of the Vehicle Assembly Building, the driver of the front control cab can be seen. The MLP is carrying two solid rocket boosters for engineering analysis vibration tests on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Active vibration attenuating seat suspension for an armored helicopter crew seat

NASA Astrophysics Data System (ADS)

Sztein, Pablo Javier

An Active Vibration Attenuating Seat Suspension (AVASS) for an MH-60S helicopter crew seat is designed to protect the occupants from harmful whole-body vibration (WBV). Magnetorheological (MR) suspension units are designed, fabricated and installed in a helicopter crew seat. These MR isolators are built to work in series with existing Variable Load Energy Absorbers (VLEAs), have minimal increase in weight, and maintain crashworthiness for the seat system. Refinements are discussed, based on testing, to minimize friction observed in the system. These refinements include the addition of roller bearings to replace friction bearings in the existing seat. Additionally, semi-active control of the MR dampers is achieved using special purpose built custom electronics integrated into the seat system. Experimental testing shows that an MH-60S retrofitted with AVASS provides up to 70.65% more vibration attenuation than the existing seat configuration as well as up to 81.1% reduction in vibration from the floor.

Wind tunnel balance system for determination of wind-induced vibrations of a rigid shuttle model in the launch configuration

NASA Technical Reports Server (NTRS)

1971-01-01

A wind tunnel balance system was designed to determine the wind-induced vibrations of a space shuttle model. The balance utilizes a flexible sting mounting in conjunction with a geometrically scaled rigid model. Bending and torsional displacements are determined through strain-gauge-instrumented spring bar mechanisms. The natural frequency of the string-model system can be varied continuously throughout the expected scaled frequency range of the shuttle vehicle while a test is in progress by the use of moveable riders on the spring bar mechanism. Through the use of a frequency analyzer, the output can be used to determine troublesome vibrational frequencies. A dimensional analysis of the wind-induced vibration problem is also presented which suggests a test procedure. In addition a computer program for analytical studies of the forced vibration problem is presented.

The performance of a piezoelectric-sensor-based SHM system under a combined cryogenic temperature and vibration environment

NASA Astrophysics Data System (ADS)

Qing, Xinlin P.; Beard, Shawn J.; Kumar, Amrita; Sullivan, Kevin; Aguilar, Robert; Merchant, Munir; Taniguchi, Mike

2008-10-01

A series of tests have been conducted to determine the survivability and functionality of a piezoelectric-sensor-based active structural health monitoring (SHM) SMART Tape system under the operating conditions of typical liquid rocket engines such as cryogenic temperature and vibration loads. The performance of different piezoelectric sensors and a low temperature adhesive under cryogenic temperature was first investigated. The active SHM system for liquid rocket engines was exposed to flight vibration and shock environments on a simulated large booster LOX-H2 engine propellant duct conditioned to cryogenic temperatures to evaluate the physical robustness of the built-in sensor network as well as operational survivability and functionality. Test results demonstrated that the developed SMART Tape system can withstand operational levels of vibration and shock energy on a representative rocket engine duct assembly, and is functional under the combined cryogenic temperature and vibration environment.

CaSO4 Scale Formation on Vibrated Piping System in the Presence Citric Acid

NASA Astrophysics Data System (ADS)

Mangestiyono, W.; Jamari, J.; Muryanto, S.; Bayuseno, A. P.

2018-02-01

Vibration in many industries commonly generated by the operation mechanical equipment such as extruder, mixer, blower, compressor, turbine, generator etc. Vibration propagates into the floor and attacks the pipe around those mechanical equipment. In this paper, the influence of vibration in a pipe on the CaSO4 scale formation was investigated to understand the effect of vibration on the kinetics, mass of scale, crystal phases and crystal polymorph. To generate vibration force, mechanical equipment was prepared consisted of electrical motor, crankshaft, connecting rod and a vibration table at where test pipe section mounted. Deposition rate increased significantly when the vibration affected to the system i.e. 0.5997 and 1.6705 gr/hr for vibration frequency 4.00 and 8.00 Hz. The addition 10.00 ppm of citric acid declined the deposition rate of 8 Hz experiment from 3.4599 gr/hr to 2.2865 gr/hr.

Finite Element Analysis and Experimental Study on Elbow Vibration Transmission Characteristics

NASA Astrophysics Data System (ADS)

Qing-shan, Dai; Zhen-hai, Zhang; Shi-jian, Zhu

2017-11-01

Pipeline system vibration is one of the significant factors leading to the vibration and noise of vessel. Elbow is widely used in the pipeline system. However, the researches about vibration of elbow are little, and there is no systematic study. In this research, we firstly analysed the relationship between elbow vibration transmission characteristics and bending radius by ABAQUS finite element simulation. Then, we conducted the further vibration test to observe the vibration transmission characteristics of different elbows which have the same diameter and different bending radius under different flow velocity. The results of simulation calculation and experiment both showed that the vibration acceleration levels of the pipeline system decreased with the increase of bending radius of the elbow, which was beneficial to reduce the transmission of vibration in the pipeline system. The results could be used as reference for further studies and designs for the low noise installation of pipeline system.

Analysis and demonstration of vibration waveform reconstruction in distributed optical fiber vibration sensing system

NASA Astrophysics Data System (ADS)

Zhu, Hui; Shan, Xuekang; Sun, Xiaohan

2017-10-01

A method for reconstructing the vibration waveform from the optical time-domain backscattering pulses in the distributed optical fiber sensing system (DOFSS) is proposed, which allows for extracting and recovering the external vibration signal from the tested pulses by analog signal processing, so that can obtain vibration location and waveform simultaneously. We establish the response model of DOFSS to the external vibration and analyze the effects of system parameters on the operational performance. The main parts of the DOFSS are optimized, including delay fiber length and wavelength, to improve the sensitivity of the system. The experimental system is set up and the vibration amplitudes and reconstructed waveforms are fit well with the original driving signal. The experimental results demonstrate that the performance of vibration waveform reconstruction is good with SNR of 15 dB whenever the external vibrations with different intensities and frequencies exert on the sensing fiber.

Decentralized semi-active damping of free structural vibrations by means of structural nodes with an on/off ability to transmit moments

NASA Astrophysics Data System (ADS)

Poplawski, Blazej; Mikułowski, Grzegorz; Mróz, Arkadiusz; Jankowski, Łukasz

2018-02-01

This paper proposes, tests numerically and verifies experimentally a decentralized control algorithm with local feedback for semi-active mitigation of free vibrations in frame structures. The algorithm aims at transferring the vibration energy of low-order, lightly-damped structural modes into high-frequency modes of vibration, where it is quickly damped by natural mechanisms of material damping. Such an approach to mitigation of vibrations, known as the prestress-accumulation release (PAR) strategy, has been earlier applied only in global control schemes to the fundamental vibration mode of a cantilever beam. In contrast, the decentralization and local feedback allows the approach proposed here to be applied to more complex frame structures and vibration patterns, where the global control ceases to be intuitively obvious. The actuators (truss-frame nodes with controllable ability to transmit moments) are essentially unblockable hinges that become unblocked only for very short time periods in order to trigger local modal transfer of energy. The paper proposes a computationally simple model of the controllable nodes, specifies the control performance measure, yields basic characteristics of the optimum control, proposes the control algorithm and then tests it in numerical and experimental examples.

Vibration sensing in smart machine rotors using internal MEMS accelerometers

NASA Astrophysics Data System (ADS)

Jiménez, Samuel; Cole, Matthew O. T.; Keogh, Patrick S.

2016-09-01

This paper presents a novel topology for enhanced vibration sensing in which wireless MEMS accelerometers embedded within a hollow rotor measure vibration in a synchronously rotating frame of reference. Theoretical relations between rotor-embedded accelerometer signals and the vibration of the rotor in an inertial reference frame are derived. It is thereby shown that functionality as a virtual stator-mounted displacement transducer can be achieved through appropriate signal processing. Experimental tests on a prototype rotor confirm that both magnitude and phase information of synchronous vibration can be measured directly without additional stator-mounted key-phasor sensors. Displacement amplitudes calculated from accelerometer signals will become erroneous at low rotational speeds due to accelerometer zero-g offsets, hence a corrective procedure is introduced. Impact tests are also undertaken to examine the ability of the internal accelerometers to measure transient vibration. A further capability is demonstrated, whereby the accelerometer signals are used to measure rotational speed of the rotor by analysing the signal component due to gravity. The study highlights the extended functionality afforded by internal accelerometers and demonstrates the feasibility of internal sensor topologies, which can provide improved observability of rotor vibration at externally inaccessible rotor locations.

Experimental Analysis of Mast Lifting and Bending Forces on Vibration Patterns Before and After Pinion Reinstallation in an OH-58 Transmission Test Rig

NASA Technical Reports Server (NTRS)

Huff, Edward M.; Lewicki, David G.; Tumer, Irem Y.; Decker, Harry; Barszez, Eric; Zakrajsek, James J.; Norvig, Peter (Technical Monitor)

2000-01-01

As part of a collaborative research program between NASA Ames Research Center (ARC), NASA Glenn Research Center (GRC), and the US Army Laboratory, a series of experiments is being performed in GRC's 500 HP OH-58 Transmission Test Rig facility and ARC's AH-I Cobra and OH-58c helicopters. The findings reported in this paper were drawn from Phase-I of a two-phase test-rig experiment, and are focused on the vibration response of an undamaged pinion gear operating in the transmission test rig. To simulate actual flight conditions, the transmission system was run at three torque levels, as well as two mast lifting and two mast bending levels. The test rig was also subjected to disassembly and reassembly of the main pinion housing to simulate the effect of maintenance operations. An analysis of variance based on the total power of the spectral distribution indicates the relative effect of each experimental factor, including Wong interactions with torque. Reinstallation of the main pinion assembly is shown to introduce changes in the vibration signature, suggesting the possibility of a strong effect of maintenance on HUMS design and use. Based on these results, further research will be conducted to compare these vibration responses with actual OH58c helicopter transmission vibration patterns.

An electromechanical coupling model of a bending vibration type piezoelectric ultrasonic transducer.

PubMed

Zhang, Qiang; Shi, Shengjun; Chen, Weishan

2016-03-01

An electromechanical coupling model of a bending vibration type piezoelectric ultrasonic transducer is proposed. The transducer is a Langevin type transducer which is composed of an exponential horn, four groups of PZT ceramics and a back beam. The exponential horn can focus the vibration energy, and can enlarge vibration amplitude and velocity efficiently. A bending vibration model of the transducer is first constructed, and subsequently an electromechanical coupling model is constructed based on the vibration model. In order to obtain the most suitable excitation position of the PZT ceramics, the effective electromechanical coupling coefficient is optimized by means of the quadratic interpolation method. When the effective electromechanical coupling coefficient reaches the peak value of 42.59%, the optimal excitation position (L1=22.52 mm) is found. The FEM method and the experimental method are used to validate the developed analytical model. Two groups of the FEM model (the Group A center bolt is not considered, and but the Group B center bolt is considered) are constructed and separately compared with the analytical model and the experimental model. Four prototype transducers around the peak value are fabricated and tested to validate the analytical model. A scanning laser Doppler vibrometer is employed to test the bending vibration shape and resonance frequency. Finally, the electromechanical coupling coefficient is tested indirectly through an impedance analyzer. Comparisons of the analytical results, FEM results and experiment results are presented, and the results show good agreement. Copyright © 2015 Elsevier B.V. All rights reserved.

Hand-arm vibration in tropical rain forestry workers.

PubMed

Futatsuka, M; Inaoka, T; Ohtsuka, R; Sakurai, T; Moji, K; Igarashi, T

1995-01-01

Working conditions and health hazards including vibration syndrome related to forestry work using chain-saws were studied in Papua New Guinea and Indonesia. The subjects comprised 291 workers including 97 chain-saw operators. The health examination consisted of peripheral circulatory and sensory tests in the upper extremities. The vibration spectrum measured at the handle of the chain-saw indicated that these acceleration levels would lead to a moderately high risk of hand-arm vibration syndrome (HAVS). The peripheral circulatory function tests revealed dysfunction after more than five years vibration exposure. However, in general, the results of the function tests and subjective complaints showed fewer health problems compared to those of Japanese forestry workers. The reason of such differences of vibration effects seem to be the following: (1) warmer climate (more than 25 degrees C throughout the year), (2) young workers and short work experience. (3) short time vibration exposures on working days in the natural forests, (4) seasonal changes in logging work (5) healthy workers effects. Thus, we found no clear evidence that the workers of our study suffered from HAVS. A principal component analysis was applied. The factor score of the components of the reactive dynamics of peripheral circulation differed significantly after more than five years' exposure. On the other hand, we cannot deny the possibility that subclinical dysfunction of peripheral circulation may be caused by chain-saw operation in the tropics in future. Further investigations on the HAVS among forestry workers in the tropic environment are needed.

Finite-Element Vibration Analysis and Modal Testing of Graphite Epoxy Tubes and Correlation Between the Data

NASA Technical Reports Server (NTRS)

Taleghani, Barmac K.; Pappa, Richard S.

1996-01-01

Structural materials in the form of graphite epoxy composites with embedded rubber layers are being used to reduce vibrations in rocket motor tubes. Four filament-wound, graphite epoxy tubes were studied to evaluate the effects of the rubber layer on the modal parameters (natural vibration frequencies, damping, and mode shapes). Tube 1 contained six alternating layers of 30-degree helical wraps and 90-degree hoop wraps. Tube 2 was identical to tube 1 with the addition of an embedded 0.030-inch-thick rubber layer. Tubes 3 and 4 were identical to tubes 1 and 2, respectively, with the addition of a Textron Kelpoxy elastomer. This report compares experimental modal parameters obtained by impact testing with analytical modal parameters obtained by NASTRAN finite-element analysis. Four test modes of tube 1 and five test modes of tube 3 correlate highly with corresponding analytical predictions. Unsatisfactory correlation of test and analysis results occurred for tubes 2 and 4 and these comparisons are not shown. Work is underway to improve the analytical models of these tubes. Test results clearly show that the embedded rubber layers significantly increase structural modal damping as well as decrease natural vibration frequencies.

Sensor design for outdoor racing bicycle field testing for human vibration comfort evaluation

NASA Astrophysics Data System (ADS)

Vanwalleghem, Joachim; De Baere, Ives; Loccufier, Mia; Van Paepegem, Wim

2013-09-01

This paper is concerned with the vibrational comfort evaluation of the cyclist when cycling a rough surface. Outdoor comfort tests have so far only been done through instrumenting the bicycle with accelerometers. This work instruments a racing bicycle with custom-made contact force sensors and velocity sensors to acquire human comfort through the absorbed power method. Comfort evaluation is assessed at the hand-arm and seat interface of the cyclist with the bicycle. By means of careful finite-element analysis for designing the force gauges at the handlebar and the seat combined with precise calibration of both force and velocity sensors, all sensors have proven to work properly. Initial field tests are focused on the proper functioning of the designed sensors and their suitability for vibration comfort measurements. Tests on a cobblestone road reveal that the outcome of the absorbed power values is within the same range as those from laboratory tests found in the literature. This sensor design approach for outdoor testing with racing bicycles may give a new interpretation on evaluating the cyclist's comfort since the vibrational load is not only quantified in terms of acceleration but also in terms of force and velocity at the bicycle-cyclist contact points.

Viking 1975 Orbiter Development Test Model/Lander Dynamic Test Model dynamic environmental testing - An overview

NASA Technical Reports Server (NTRS)

Milder, G.

1975-01-01

The current work presents an overview of the Viking 1975 environmental testing from an engineering standpoint. An extremely large vibration test fixture had to be designed, analyzed, and integrated into a test setup that employed hydrostatic bearings in a new fashion. A vibration control system was also required that would allow for thirty-six channels of sine-wave peak select control from acceleration, force-of-strain transducers. In addition, some 68 channels of peak limiting shutdown capability were needed for backup and monitoring of other data during the forced vibration test. Pretesting included analyses of the fixture design, overturning moment, control system capabilities, and response of the entire spacecraft/fixture/exciter system to the test environment. Closed-loop control for acoustic testing was a necessity due to the fact that the Viking spacecraft took up a major portion of the volume of the 10,000 cu ft chamber. The spacecraft emerged from testing undamaged.

Dynamic determination of modulus of elasticity of full-size wood composite panels using a vibration method

Treesearch

Cheng Guan; Houjiang Zhang; Lujing Zhou; Xiping Wang

2015-01-01

A vibration testing method based on free vibration theory in a ‘‘free–free” support condition was investigated for evaluating the modulus of elasticity (MOE) of full-size wood composite panels (WCPs). Vibration experiments were conducted on three types of WCPs (medium density fibreboard, particleboard, and plywood) to determine the dynamic MOE of the panels. Static...

Use of piezoelectric dampers for improving the feel of golf clubs

NASA Astrophysics Data System (ADS)

Bianchini, Emanuele; Spangler, Ronald L., Jr.; Pandell, Tracy

1999-06-01

Several sports are based upon a tool (club, bat, stick) striking an object (ball, puck) across a field of play. Anytime two structures collide, vibration is created by the impact of the two. The impact of the objects excites the structural modes of the tool, creating a vibration that can be felt by the player, especially if the hit is not at a `sweet spot'. Vibration adversely affects both feel and performance. This paper explains how piezoelectric dampers were developed to reduce vibration and improve the feel of ball-impact sporting goods such as golf clubs. The paper describes how the dynamic characteristics of a golf club were calculated, at first in the free-free condition, and then during its operation conditions (the swing of the club, and the impact with the ball). The dynamic characteristics were used to develop a damper that addressed a specific, or multiple, modes of interest. The damper development and testing are detailed in this paper. Both objective laboratory tests and subjective player tests were performed to evaluate the effectiveness of the piezoelectric dampers. The results of the tests, along with published medical data on the sensitivity of the human body, were used to draw a correlation between human feel and vibration reduction.

Vibration syndrome in chipping and grinding workers.

PubMed

1984-10-01

A clear conclusion from these studies is that vibration syndrome occurs in chipping and grinding workers in this country and that earlier reports that it may not exist were probably inaccurate. The careful selection of exposed and control groups for analysis strengthens the observed association between vibration syndrome and the occupational use of pneumatic chipping hammers and grinding tools. In the foundry populations studied the vibration syndrome was severe, with short latencies and high prevalences of the advanced stages. The shipyard population did not display this pattern. This difference can be attributed to variations in work practices but the more important factor seems to be the effect of incentive work schedules. Comparisons of groups of hourly and incentive workers from the shipyard and within foundry populations consistently demonstrated that incentive work was associated with increased severity of vibration syndrome. Excessive vibration levels were measured on chipping and grinding tools. Of the factors studied, reduction of throttle level decreased the vibration levels measured on chipping hammers. For grinders, the working condition of the tool affected the measured vibration acceleration levels. Grinders receiving average to poor maintenance showed higher vibration levels. The results of objective clinical testing did not yield tests with diagnostic properties. To date, the clinical judgment of the physician remains the primary focus of the diagnosis of vibration syndrome. A number of actions can be taken to prevent vibration syndrome. Preplacement medical examinations can identify workers predisposed to or experiencing Raynaud's phenomenon or disease. Informing employees and employers about the signs, symptoms, and consequences of vibration syndrome can encourage workers to report the condition to their physicians promptly. Engineering approaches to preventing vibration syndrome include increased quality control on castings to reduce finishing time and automation of the finishing process. Tool manufacturers can contribute by modifying or redesigning tools to reduce vibration. The technology to reduce vibration from hand tools exists but the engineering application is difficult. Vibration from chain saws has been reduced through changes in design and some companies have begun to redesign jackhammers, scalers, grinders, and chipping hammers. As these become available, purchasers can encourage manufacturers by selecting tools with antivibration characteristics. Vibration from tools currently in use can be controlled by periodically scheduled inspection and maintenance programs for vibrating tools.(ABSTRACT TRUNCATED AT 400 WORDS)

The Shock and Vibration Bulletin. Part 3. Skylab, Vibration Testing and Analysis

DTIC Science & Technology

1973-06-01

Zft- ,Instrument Unit - (Acoustic Test Only) -orward Compartment Crew Ouarters Meteoroid Shield IntertageTACS Spheres (Acoustic Tesi - Radiator...weighs more than the lower floor. You Mru ertes: You hadn’t flown this struc- might feel that since the analysis approach wasconfirmed on the upper floor

Internal Temperature Control For Vibration Testers

NASA Technical Reports Server (NTRS)

Dean, Richard J.

1996-01-01

Vibration test fixtures with internal thermal-transfer capabilities developed. Made of aluminum for rapid thermal transfer. Small size gives rapid response to changing temperatures, with better thermal control. Setup quicker and internal ducting facilitates access to parts being tested. In addition, internal flows smaller, so less energy consumed in maintaining desired temperature settings.

Some Aspects of the Investigation of Random Vibration Influence on Ride Comfort

NASA Astrophysics Data System (ADS)

DEMIĆ, M.; LUKIĆ, J.; MILIĆ, Ž.

2002-05-01

Contemporary vehicles must satisfy high ride comfort criteria. This paper attempts to develop criteria for ride comfort improvement. The highest loading levels have been found to be in the vertical direction and the lowest in lateral direction in passenger cars and trucks. These results have formed the basis for further laboratory and field investigations. An investigation of the human body behaviour under random vibrations is reported in this paper. The research included two phases; biodynamic research and ride comfort investigation. A group of 30 subjects was tested. The influence of broadband random vibrations on the human body was examined through the seat-to-head transmissibility function (STHT). Initially, vertical and fore and aft vibrations were considered. Multi-directional vibration was also investigated. In the biodynamic research, subjects were exposed to 0·55, 1·75 and 2·25 m/s2 r.m.s. vibration levels in the 0·5- 40 Hz frequency domain. The influence of sitting position on human body behaviour under two axial vibrations was also examined. Data analysis showed that the human body behaviour under two-directional random vibrations could not be approximated by superposition of one-directional random vibrations. Non-linearity of the seated human body in the vertical and fore and aft directions was observed. Seat-backrest angle also influenced STHT. In the second phase of experimental research, a new method for the assessment of the influence of narrowband random vibration on the human body was formulated and tested. It included determination of equivalent comfort curves in the vertical and fore and aft directions under one- and two-directional narrowband random vibrations. Equivalent comfort curves for durations of 2·5, 4 and 8 h were determined.

Whole-body vibration improves neuromuscular parameters and functional capacity in osteopenic postmenopausal women.

PubMed

Dutra, Milena C; de Oliveira, Mônica L; Marin, Rosangela V; Kleine, Hellen C R; Silva, Orivaldo L; Lazaretti-Castro, Marise

2016-08-01

In this longitudinal, paired-control study, we developed special vibration platforms to evaluate the effects of low-intensity vibration on neuromuscular function and functional capacity in osteopenic postmenopausal women. Women in the platform group (PG; n = 62) stood still and barefoot on the platform for 20 minutes, 5 times a week for 12 months. Each platform vibrated with a frequency of 60 Hz, intensity of 0.6g, and amplitude of less than 1 mm. Women in the control group (CG; n = 60) were followed up and instructed not to modify their physical activity during the study. Every 3 months all volunteers were invited to a visit to check for any change in their lifestyle. Assessments were performed at baseline and at 12 months, and included isometric muscle strength in the hip flexors and back extensors, right handgrip strength, dynamic upper limb strength (arm curl test), upper trunk flexibility (reach test [RT]), mobility (timed up and go test), and static balance (unipedal stance test). Statistical analyses were performed using the intention-to-treat strategy. Both groups were similar for all variables at baseline. At the end of intervention, the PG was significantly better than CG in all parameters but in the RT. When compared with baseline, after 12 months of vibration the PG presented statistically significant improvements in isometric and dynamic muscle strength in the hip flexors (+36.7%), back extensors (+36.5%), handgrip strength (+4.4%), arm curl test (+22.8%), RT (+9.9%), unipedal stance test (+6.8%), and timed up and go test (-9.2%), whereas the CG showed no significant differences during the same period of time. As such, there were no side effects related to the study procedures during the 12 months of intervention. Low-intensity vibration improved balance, motility, and muscle strength in the upper and lower limbs in postmenopausal women.

Subsychronous vibration of multistage centrifugal compressors forced by rotating stall

NASA Technical Reports Server (NTRS)

Fulton, J. W.

1987-01-01

A multistage centrifugal compressor, in natural gas re-injection service on an offshore petroleum production platform, experienced subsynchronous vibrations which caused excessive bearing wear. Field performance testing correlated the subsynchronous amplitude with the discharge flow coefficient, demonstrating the excitation to be aerodynamic. Adding two impellers allowed an increase in the diffuser flow angle (with respect to tangential) to meet the diffuser stability criteria based on factory and field tests correlated using the theory of Senoo (for rotating stall in a vaneless diffuser). This modification eliminated all significant subsynchronous vibrations in field service, thus confirming the correctness of the solution. Other possible sources of aerodynamically induced vibrations were considered, but the judgment that those are unlikely has been confirmed by subsequent experience with other similar compressors.

Postural stability effects of random vibration at the feet of construction workers in simulated elevation.

PubMed

Simeonov, P; Hsiao, H; Powers, J; Ammons, D; Kau, T; Amendola, A

2011-07-01

The risk of falls from height on a construction site increases under conditions which degrade workers' postural control. At elevation, workers depend heavily on sensory information from their feet to maintain balance. The study tested two hypotheses: "sensory enhancement"--sub-sensory (undetectable) random mechanical vibrations at the plantar surface of the feet can improve worker's balance at elevation; and "sensory suppression"--supra-sensory (detectable) random mechanical vibrations can have a degrading effect on balance in the same experimental settings. Six young (age 20-35) and six aging (age 45-60) construction workers were tested while standing in standard and semi-tandem postures on instrumented gel insoles. The insoles applied sub- or supra-sensory levels of random mechanical vibrations to the feet. The tests were conducted in a surround-screen virtual reality system, which simulated a narrow plank at elevation on a construction site. Upper body kinematics was assessed with a motion-measurement system. Postural stability effects were evaluated by conventional and statistical mechanics sway measures, as well as trunk angular displacement parameters. Analysis of variance did not confirm the "sensory enhancement" hypothesis, but provided evidence for the "sensory suppression" hypothesis. The supra-sensory vibration had a destabilizing effect, which was considerably stronger in the semi-tandem posture and affected most of the sway variables. Sensory suppression associated with elevated vibration levels on a construction site may increase the danger of losing balance. Construction workers at elevation, e.g., on a beam or narrow plank might be at increased risk of fall if they can detect vibrations under their feet. To reduce the possibility of losing balance, mechanical vibration to supporting structures used as walking/working surfaces should be minimized when performing construction tasks at elevation. Published by Elsevier Ltd.

Modulation of soleus corticospinal excitability during Achilles tendon vibration.

PubMed

Lapole, Thomas; Temesi, John; Arnal, Pierrick J; Gimenez, Philippe; Petitjean, Michel; Millet, Guillaume Y

2015-09-01

Soleus (SOL) corticospinal excitability has been reported to increase during Achilles tendon vibration. The aim of the present study was to further investigate SOL corticospinal excitability and elucidate the changes to intracortical mechanisms during Achilles tendon vibration. Motor-evoked potentials (MEPs) were elicited in the SOL by transcranial magnetic stimulation (TMS) of the corresponding motor cortical area of the leg with and without 50-Hz Achilles tendon vibration. SOL input-output curves were determined. Paired-pulse protocols were also performed to investigate short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) by conditioning test TMS pulses with sub-threshold TMS pulses at inter-stimulus intervals of 3 and 13 ms, respectively. During Achilles tendon vibration, motor threshold was lower than in the control condition (43 ± 13 vs. 49 ± 11 % of maximal stimulator output; p = 0.008). Input-output curves were also influenced by vibration, i.e. there was increased maximal MEP amplitude (0.694 ± 0.347 vs. 0.268 ± 0.167 mV; p < 0.001), decreased TMS intensity to elicit a MEP of half the maximal MEP amplitude (100 ± 13 vs. 109 ± 9 % motor threshold; p = 0.009) and a strong tendency for decreased slope constant (0.076 ± 0.04 vs. 0.117 ± 0.04; p = 0.068). Vibration reduced ICF (98 ± 61 vs. 170 ± 105 % of test MEP amplitude; p = 0.05), but had no effect on SICI (53 ± 26 vs. 48 ± 22 % of test MEP amplitude; p = 0.68). The present results further document the increased vibration-induced corticospinal excitability in the soleus muscle and suggest that this increase is not mediated by changes in SICI or ICF.

Active Blade Vibration Control Being Developed and Tested

NASA Technical Reports Server (NTRS)

Johnson, Dexter

2003-01-01

Gas turbine engines are currently being designed to have increased performance, lower weight and manufacturing costs, and higher reliability. Consequently, turbomachinery components, such as turbine and compressor blades, have designs that are susceptible to new vibration problems and eventual in-service failure due to high-cycle fatigue. To address this problem, researchers at the NASA Glenn Research Center are developing and testing innovative active blade vibration control concepts. Preliminary results of using an active blade vibration control system, involving a rotor supported by an active magnetic bearing in Glenn's Dynamic Spin Rig, indicate promising results (see the photograph). Active blade vibration control was achieved using feedback of blade strain gauge signals within the magnetic bearing control loop. The vibration amplitude was reduced substantially (see the graphs). Also, vibration amplitude amplification was demonstrated; this could be used to enhance structural mode identification, if desired. These results were for a nonrotating two-bladed disk. Tests for rotating blades are planned. Current and future active blade vibration control research is planned to use a fully magnetically suspended rotor and smart materials. For the fully magnetically suspended rotor work, three magnetic bearings (two radial and one axial) will be used as actuators instead of one magnetic bearing. This will allow additional degrees of freedom to be used for control. For the smart materials work, control effectors located on and off the blade will be considered. Piezoelectric materials will be considered for on-the-blade actuation, and actuator placement on a stator vane, or other nearby structure, will be investigated for off-the-blade actuation. Initial work will focus on determining the feasibility of these methods by performing basic analysis and simple experiments involving feedback control.

Field joint environmental protection system vibration/pressurization qualification

NASA Technical Reports Server (NTRS)

Cook, M.

1989-01-01

The procedures used and results obtained from vibration testing the redesigned solid rocket motor (RSRM) field joint environmental protection system (FJEPS), hereafter referred to as the joint protection system (JPS) are documented. The major purposes were to certify that the flight-designed JPS will withstand the dynamic environmental conditions of the redesigned solid rocket booster, and to certify that the cartridge check valve (vent valve) will relieve pressure build-up under the JPS during the initial 120 sec of flight. Also, an evaluation of the extruded cork insulation bonding was performed after the vibration testing.

The Shock and Vibration Bulletin. Part 4. Vibration Testing, Instrumentation, Loads and Environments, Tracked Vehicles

DTIC Science & Technology

1978-09-01

self with a nonlinear (thermocouple) function, the limits X os nu 2O being: x Enables Temperature Controller to command heat 0 Code Temnperature ___6...34 Shock and Vi- bration Bulletin 42, 1970. (2) R.T. Fandrich, " Self -Tuning Re- • sonant Fixtures", 47th Shock andVibration Symposium, October 1976. . " (3...is given in Fig. 4. timTit for "ysem From the shape of some of these it is apparent linear respose that in some tests dampino ratios of the order 0 of

A piezoelectric six-DOF vibration energy harvester based on parallel mechanism: dynamic modeling, simulation, and experiment

NASA Astrophysics Data System (ADS)

Yuan, G.; Wang, D. H.

2017-03-01

Multi-directional and multi-degree-of-freedom (multi-DOF) vibration energy harvesting are attracting more and more research interest in recent years. In this paper, the principle of a piezoelectric six-DOF vibration energy harvester based on parallel mechanism is proposed to convert the energy of the six-DOF vibration to single-DOF vibrations of the limbs on the energy harvester and output voltages. The dynamic model of the piezoelectric six-DOF vibration energy harvester is established to estimate the vibrations of the limbs. On this basis, a Stewart-type piezoelectric six-DOF vibration energy harvester is developed and explored. In order to validate the established dynamic model and the analysis results, the simulation model of the Stewart-type piezoelectric six-DOF vibration energy harvester is built and tested with different vibration excitations by SimMechanics, and some preliminary experiments are carried out. The results show that the vibration of the limbs on the piezoelectric six-DOF vibration energy harvester can be estimated by the established dynamic model. The developed Stewart-type piezoelectric six-DOF vibration energy harvester can harvest the energy of multi-directional linear vibration and multi-axis rotating vibration with resonance frequencies of 17 Hz, 25 Hz, and 47 Hz. Moreover, the resonance frequencies of the developed piezoelectric six-DOF vibration energy harvester are not affected by the direction changing of the vibration excitation.

Passive Isolators for use on the International Space Station

NASA Technical Reports Server (NTRS)

Houston, Janice; Gattis, Christy

2003-01-01

The value of the International Space Station (ISS) as a premier microgravity environment is currently at risk due to structure-borne vibration. The vibration sources are varied and include crew activities such as exercising or simply moving from module to module, and electro- mechanical equipment such as fans and pumps. Given such potential degradation of usable microgravity, anything that can be done to dampen vibration on-orbit will significantly benefit microgravity users. Most vibration isolation schemes, both active and passive, have proven to be expensive - both operationally and from the cost of integrating isolation systems into primary/secondary structural interfaces (e.g., the ISS module/rack interface). Recently, passively absorptive materials have been tested at the bolt interfaces between the operating equipment and support structure (secondary/tertiary structural interfaces). The results indicate that these materials may prove cost-effective in mitigating the vibrational problems of the ISS. We report herein tests of passive absorbers placed at the interface of a vibration-inducing component: the Development Distillation Assembly, a subassembly of the Urine Processing Assembly, which is a rotating centrifuge and cylinder assembly attached to a mounting plate. Passive isolators were installed between this mounting plate and its support shelf. Three materials were tested: BISCO HT-800, Sorbothane 30 and Sorbothane 50, plus a control test with a hard shim. In addition, four distinct combinations of the HT-800 and Sorbothane 50 were tested. Results show a significant (three orders of magnitude) reduction of transmitted energy, as measured in power spectral density (PSD), using the isolation materials. It is noted, however, that passive materials cannot prevent the transmission of very strong forces or absorb the total energy induced from structural resonances.

Assassin bug uses aggressive mimicry to lure spider prey.

PubMed

Wignall, Anne E; Taylor, Phillip W

2011-05-07

Assassin bugs (Stenolemus bituberus) hunt web-building spiders by invading the web and plucking the silk to generate vibrations that lure the resident spider into striking range. To test whether vibrations generated by bugs aggressively mimic the vibrations generated by insect prey, we compared the responses of spiders to bugs with how they responded to prey, courting male spiders and leaves falling into the web. We also analysed the associated vibrations. Similar spider orientation and approach behaviours were observed in response to vibrations from bugs and prey, whereas different behaviours were observed in response to vibrations from male spiders and leaves. Peak frequency and duration of vibrations generated by bugs were similar to those generated by prey and courting males. Further, vibrations from bugs had a temporal structure and amplitude that were similar to vibrations generated by leg and body movements of prey and distinctly different to vibrations from courting males or leaves, or prey beating their wings. To be an effective predator, bugs do not need to mimic the full range of prey vibrations. Instead bugs are general mimics of a subset of prey vibrations that fall within the range of vibrations classified by spiders as 'prey'.

Mated vertical ground vibration test

NASA Technical Reports Server (NTRS)

Ivey, E. W.

1980-01-01

The Mated Vertical Ground Vibration Test (MVGVT) was considered to provide an experimental base in the form of structural dynamic characteristics for the shuttle vehicle. This data base was used in developing high confidence analytical models for the prediction and design of loads, pogo controls, and flutter criteria under various payloads and operational missions. The MVGVT boost and launch program evolution, test configurations, and their suspensions are described. Test results are compared with predicted analytical results.

Structural and Acoustic Damping Characteristics of Polyimide Microspheres

NASA Technical Reports Server (NTRS)

Palumbo, Daniel L.; Park, Junhong

2005-01-01

A broad range of tests have been performed to evaluate the capability of tiny lightweight polyimide spheres to reduce sound and vibration. The types of testing includes impedance tube measurement of propagation constant, sound power insertion loss for single and double wall systems, particle frame wave characterization and beam vibration reduction. The tests were performed using spheres made of two types of polyimide and with varying diameter. Baseline results were established using common noise reduction treatment materials such as fiberglass and foam. The spheres were difficult to test due to their inherent mobility. Most tests required some adaptation to contain the spheres. One test returned obvious non-linear behavior, a result which has come to be expected for treatments of this type. The polyimide spheres are found to be a competent treatment for both sound and vibration energy with the reservation that more work needs to be done to better characterize the non-linear behavior.

Application of the Semi-Empirical Force-Limiting Approach for the CoNNeCT SCAN Testbed

NASA Technical Reports Server (NTRS)

Staab, Lucas D.; McNelis, Mark E.; Akers, James C.; Suarez, Vicente J.; Jones, Trevor M.

2012-01-01

The semi-empirical force-limiting vibration method was developed and implemented for payload testing to limit the structural impedance mismatch (high force) that occurs during shaker vibration testing. The method has since been extended for use in analytical models. The Space Communications and Navigation Testbed (SCAN Testbed), known at NASA as, the Communications, Navigation, and Networking re-Configurable Testbed (CoNNeCT), project utilized force-limiting testing and analysis following the semi-empirical approach. This paper presents the steps in performing a force-limiting analysis and then compares the results to test data recovered during the CoNNeCT force-limiting random vibration qualification test that took place at NASA Glenn Research Center (GRC) in the Structural Dynamics Laboratory (SDL) December 19, 2010 to January 7, 2011. A compilation of lessons learned and considerations for future force-limiting tests is also included.

Nondestructive evaluation of green wood using stress wave and transverse vibration techniques

Treesearch

Udaya B. Halabe; Gangadhar M. Bidigalu; Hota V.S. GangaRao; Robert J. Ross

1997-01-01

Longitudinal stress wave and transverse vibration nondestructive testing (NDT) techniques have proven to be accurate means of evaluating the quality of wood based products. Researchers have found strong relationships between stress wave and transverse vibration parameters (e.g., wave velocity and modulus of elasticity predicted using NDT measurements) with the actual...

77 FR 4650 - Airworthiness Directives; General Electric Company Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-31

... blade borescope inspection (BSI) or a failed engine core vibration survey, establishes a new lower life... LPT rotor stage 3 disk removal after a failed HPT blade BSI or a failed engine core vibration survey... engine test cell as part of an engine manual performance run fulfill the vibration survey requirements of...

14 CFR 23.907 - Propeller vibration and fatigue.

Code of Federal Regulations, 2013 CFR

2013-01-01

... based on direct testing of the propeller on the airplane and engine installation for which approval is... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood...

14 CFR 23.907 - Propeller vibration and fatigue.

Code of Federal Regulations, 2014 CFR

2014-01-01

... based on direct testing of the propeller on the airplane and engine installation for which approval is... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood...

CR-Calculus and adaptive array theory applied to MIMO random vibration control tests

NASA Astrophysics Data System (ADS)

Musella, U.; Manzato, S.; Peeters, B.; Guillaume, P.

2016-09-01

Performing Multiple-Input Multiple-Output (MIMO) tests to reproduce the vibration environment in a user-defined number of control points of a unit under test is necessary in applications where a realistic environment replication has to be achieved. MIMO tests require vibration control strategies to calculate the required drive signal vector that gives an acceptable replication of the target. This target is a (complex) vector with magnitude and phase information at the control points for MIMO Sine Control tests while in MIMO Random Control tests, in the most general case, the target is a complete spectral density matrix. The idea behind this work is to tailor a MIMO random vibration control approach that can be generalized to other MIMO tests, e.g. MIMO Sine and MIMO Time Waveform Replication. In this work the approach is to use gradient-based procedures over the complex space, applying the so called CR-Calculus and the adaptive array theory. With this approach it is possible to better control the process performances allowing the step-by-step Jacobian Matrix update. The theoretical bases behind the work are followed by an application of the developed method to a two-exciter two-axis system and by performance comparisons with standard methods.

Nonlinear dynamic analysis of rigid rotor supported by gas foil bearings: Effects of gas film and foil structure on subsynchronous vibrations

NASA Astrophysics Data System (ADS)

Guo, Zhiyang; Feng, Kai; Liu, Tianyu; Lyu, Peng; Zhang, Tao

2018-07-01

Highly nonlinear subsynchronous vibrations are the main causing factors of failure in gas foil bearing (GFB)-rotor systems. Thus, investigating the vibration generation mechanisms and the relationship between subsynchronous vibrations and GFBs is necessary to ensure the healthy operation of rotor systems. In this study, an integrated nonlinear dynamic model with the consideration of shaft motion, unsteady gas film, and deformations of foil structure is established to investigate the effect of gas film and foil structure on system subsynchronous response. One test rig of GFB-rotor system is developed for model comparison. High agreement is shown between the prediction and test data, especially in the frequency domain. The nonlinear dynamic response is analyzed using waterfall plots, operation deflection shapes, journal orbits, Poincaré maps, and fast Fourier transforms. The parameter studies reveal that subsynchronous vibrations are highly related to gas film and foil structure. Subsynchronous vibrations can be adjusted by parameters such as bump stiffness, nominal clearance, and static loads. Therefore, gas foil bearing parameters should be carefully adjusted by system manufacturers to achieve the best rotordynamic performance.

Digital evaluation of sitting posture comfort in human-vehicle system under Industry 4.0 framework

NASA Astrophysics Data System (ADS)

Tao, Qing; Kang, Jinsheng; Sun, Wenlei; Li, Zhaobo; Huo, Xiao

2016-09-01

Most of the previous studies on the vibration ride comfort of the human-vehicle system were focused only on one or two aspects of the investigation. A hybrid approach which integrates all kinds of investigation methods in real environment and virtual environment is described. The real experimental environment includes the WBV(whole body vibration) test, questionnaires for human subjective sensation and motion capture. The virtual experimental environment includes the theoretical calculation on simplified 5-DOF human body vibration model, the vibration simulation and analysis within ADAMS/VibrationTM module, and the digital human biomechanics and occupational health analysis in Jack software. While the real experimental environment provides realistic and accurate test results, it also serves as core and validation for the virtual experimental environment. The virtual experimental environment takes full advantages of current available vibration simulation and digital human modelling software, and makes it possible to evaluate the sitting posture comfort in a human-vehicle system with various human anthropometric parameters. How this digital evaluation system for car seat comfort design is fitted in the Industry 4.0 framework is also proposed.

Vibration Modal Characterization of a Stirling Convertor via Base-Shake Excitation

NASA Technical Reports Server (NTRS)

Suarez, Vicente J.; Goodnight, Thomas W.; Hughes, William O.; Samorezov, Sergey

2003-01-01

The U.S. Department of Energy (DOE), Lockheed Martin (LM), Stirling Technology Company (STC), and NASA John H. Glenn Research Center (GRC) are currently developing a high-efficiency Stirling convertor for use in a Stirling Radioisotope Generator (SRG). NASA and DOE have identified the SRG for potential use as an advanced power system for future NASA Space Science missions, providing spacecraft onboard electric power for deep space missions and power for unmanned Mars rovers. Low-level, baseshake sine vibration tests were conducted on the Stirling Technology Demonstration Convertor (TDC), at NASA GRC's Structural Dynamics Laboratory, in February 2001, as part of the development of this Stirling technology. The purpose of these tests was to provide a better understanding of the TDC's internal dynamic response to external vibratory base excitations. The knowledge obtained can therein be used to help explain the success that the TDC enjoyed in its previous random vibration qualification tests (December 1999). This explanation focuses on the TDC s internal dynamic characteristics in the 50 to 250 Hz frequency range, which corresponds to the maximum input levels of its qualification random vibration test specification. The internal dynamic structural characteristics of the TDC have now been measured in two separate tests under different motoring and dynamic loading conditions: (1) with the convertor being electrically motored, under a vibratory base-shake excitation load, and (2) with the convertor turned off, and its alternator internals undergoing dynamic excitation via hammer impact loading. This paper addresses the test setup, procedure and results of the base-shake vibration testing conducted on the motored TDC, and will compare these results with those results obtained from the dynamic impact tests (May 2001) on the nonmotored TDC.

Optimized Non-Obstructive Particle Damping (NOPD) Treatment for Composite Honeycomb Structures

NASA Technical Reports Server (NTRS)

Panossian, H.

2008-01-01

Non-Obstructive Particle Damping (NOPD) technology is a passive vibration damping approach whereby metallic or non-metallic particles in spherical or irregular shapes, of heavy or light consistency, and even liquid particles are placed inside cavities or attached to structures by an appropriate means at strategic locations, to absorb vibration energy. The objective of the work described herein is the development of a design optimization procedure and discussion of test results for such a NOPD treatment on honeycomb (HC) composite structures, based on finite element modeling (FEM) analyses, optimization and tests. Modeling and predictions were performed and tests were carried out to correlate the test data with the FEM. The optimization procedure consisted of defining a global objective function, using finite difference methods, to determine the optimal values of the design variables through quadratic linear programming. The optimization process was carried out by targeting the highest dynamic displacements of several vibration modes of the structure and finding an optimal treatment configuration that will minimize them. An optimal design was thus derived and laboratory tests were conducted to evaluate its performance under different vibration environments. Three honeycomb composite beams, with Nomex core and aluminum face sheets, empty (untreated), uniformly treated with NOPD, and optimally treated with NOPD, according to the analytically predicted optimal design configuration, were tested in the laboratory. It is shown that the beam with optimal treatment has the lowest response amplitude. Described below are results of modal vibration tests and FEM analyses from predictions of the modal characteristics of honeycomb beams under zero, 50% uniform treatment and an optimal NOPD treatment design configuration and verification with test data.

Noninterference Systems Developed for Measuring and Monitoring Rotor Blade Vibrations

NASA Technical Reports Server (NTRS)

Kurkov, Anatole P.

2003-01-01

In the noninterference measurement of blade vibrations, a laser light beam is transmitted to the rotor blade tips through a single optical fiber, and the reflected light from the blade tips is collected by a receiving fiber-optic bundle and conducted to a photodetector. Transmitting and receiving fibers are integrated in an optical probe that is enclosed in a metal tube which also houses a miniature lens that focuses light on the blade tips. Vibratory blade amplitudes can be deduced from the measurement of the instantaneous time of arrival of the blades and the knowledge of the rotor speed. The in-house noninterference blade-vibration measurement system was developed in response to requirements to monitor blade vibrations in several tests where conventional strain gauges could not be installed or where there was a need to back up strain gauges should critical gauges fail during the test. These types of measurements are also performed in the aircraft engine industry using proprietary in-house technology. Two methods of measurement were developed for vibrations that are synchronous with a rotor shaft. One method requires only one sensor; however, it is necessary to continuously record the data while the rotor is being swept through the resonance. In the other method, typically four sensors are employed and the vibratory amplitude is deduced from the data by performing a least square fit to a harmonic function. This method does not require continuous recording of data through the resonance and, therefore, is better suited for monitoring. The single-probe method was tested in the Carl facility at the Wright- Patterson Air Force Base, and the multiple-probe method was tested in NASA Glenn Research Center's Spin Rig facility, which uses permanent magnets to excite synchronous vibrations. Representative results from this test are illustrated in the bar chart. Nonsynchronous vibrations were measured online during testing of the Quiet High Speed Fan in Glenn s 9- by 15-Foot Low-Speed Wind Tunnel. Three sensors were employed, enabling a reconstruction of the vibratory patterns at the leading and trailing edges at the tip span, as well as a determination of vibratory amplitudes for every blade.

Operational modal analysis of a high-rise multi-function building with dampers by a Bayesian approach

NASA Astrophysics Data System (ADS)

Ni, Yanchun; Lu, Xilin; Lu, Wensheng

2017-03-01

The field non-destructive vibration test plays an important role in the area of structural health monitoring. It assists in monitoring the health status and reducing the risk caused by the poor performance of structures. As the most economic field test among the various vibration tests, the ambient vibration test is the most popular and is widely used to assess the physical condition of a structure under operational service. Based on the ambient vibration data, modal identification can help provide significant previous study for model updating and damage detection during the service life of a structure. It has been proved that modal identification works well in the investigation of the dynamic performance of different kinds of structures. In this paper, the objective structure is a high-rise multi-function office building. The whole building is composed of seven three-story structural units. Each unit comprises one complete floor and two L shaped floors to form large spaces along the vertical direction. There are 56 viscous dampers installed in the building to improve the energy dissipation capacity. Due to the special feature of the structure, field vibration tests and further modal identification were performed to investigate its dynamic performance. Twenty-nine setups were designed to cover all the degrees of freedom of interest. About two years later, another field test was carried out to measure the building for 48 h to investigate the performance variance and the distribution of the modal parameters. A Fast Bayesian FFT method was employed to perform the modal identification. This Bayesian method not only provides the most probable values of the modal parameters but also assesses the associated posterior uncertainty analytically, which is especially relevant in field vibration tests arising due to measurement noise, sensor alignment error, modelling error, etc. A shaking table test was also implemented including cases with and without dampers, which assists in investigating the effect of dampers. The modal parameters obtained from different tests were investigated separately and then compared with each other.

Vortex Shedding from a Vibrating Cable with Attached Spherical Bodies in a Linear Shear Flow.

DTIC Science & Technology

1982-10-27

correlation and strengthened parallel vo:tex shedding. The test model used in the present study was a flexible cable. The vortex street wake behind a vibrating...pattern, different tha. the characteristic patterns associated with either the stationary or vibrating locked-on vortex street wakes was observed... vortex shedding to the vibration of a rigid or flexible cylinder has been explored by Griffin [17]. He presents a model for a universal wake Strouhal

Effects of Achilles tendon vibration, surface and visual conditions on lower leg electromyography in young adults with and without recurrent ankle sprains.

PubMed

Lubetzky, Anat V; Price, Robert; McCoy, Sarah W

2016-07-01

Functional ankle instability is associated with decreased ankle muscle function. Compliant surfaces and eyes-closed training are commonly used for rehabilitation and prevention of ankle sprains. Brief Achilles tendon vibration is commonly used in the study of postural control. To test the level of activation of tibialis anterior (TIB) and fibularis longus (FIB), bilateral Achilles tendon vibration was applied for the middle 20 s in a series of 60-s trials, when 10 healthy young adults and 10 adults with history of repeated ankle sprains were standing bipedal: on floor, on memory foam, or on a Both Sides Up (BOSU) ball, with eyes open, and on floor and foam with eyes closed. Differences in Integrated surface electromyography (IEMG) of TIB and FIB were significant for both groups pre, during, and post vibration (Friedman Tests, p < 0.001 for all). In both groups, the highest IEMG for TIB was obtained during vibration when standing on foam with eyes closed, whereas the highest IEMG for FIB was obtained during vibration when standing on the BOSU. Bipedal stance on BOSU and brief Achilles tendon vibration may be a useful intervention when a session's goal is to facilitate lower leg muscles activation. Future research should explore training effects as well as the effect of FIB tendon vibration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laboratory and field measurements and evaluations of vibration at the handles of riveting hammers

PubMed Central

McDOWELL, THOMAS W.; WARREN, CHRISTOPHER; WELCOME, DANIEL E.; DONG, REN G.

2015-01-01

The use of riveting hammers can expose workers to harmful levels of hand-transmitted vibration (HTV). As a part of efforts to reduce HTV exposures through tool selection, the primary objective of this study was to evaluate the applicability of a standardized laboratory-based riveting hammer assessment protocol for screening riveting hammers. The second objective was to characterize the vibration emissions of reduced vibration riveting hammers and to make approximations of the HTV exposures of workers operating these tools in actual work tasks. Eight pneumatic riveting hammers were selected for the study. They were first assessed in a laboratory using the standardized method for measuring vibration emissions at the tool handle. The tools were then further assessed under actual working conditions during three aircraft sheet metal riveting tasks. Although the average vibration magnitudes of the riveting hammers measured in the laboratory test were considerably different from those measured in the field study, the rank orders of the tools determined via these tests were fairly consistent, especially for the lower vibration tools. This study identified four tools that consistently exhibited lower frequency-weighted and unweighted accelerations in both the laboratory and workplace evaluations. These observations suggest that the standardized riveting hammer test is acceptable for identifying tools that could be expected to exhibit lower vibrations in workplace environments. However, the large differences between the accelerations measured in the laboratory and field suggest that the standardized laboratory-based tool assessment is not suitable for estimating workplace riveting hammer HTV exposures. Based on the frequency-weighted accelerations measured at the tool handles during the three work tasks, the sheet metal mechanics assigned to these tasks at the studied workplace are unlikely to exceed the daily vibration exposure action value (2.5 m s−2) using any of the evaluated riveting hammers. PMID:22539561

Integrating Oil Debris and Vibration Gear Damage Detection Technologies Using Fuzzy Logic

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Afjeh, Abdollah A.

2002-01-01

A diagnostic tool for detecting damage to spur gears was developed. Two different measurement technologies, wear debris analysis and vibration, were integrated into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual measurement technologies. This diagnostic tool was developed and evaluated experimentally by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spur Gear Fatigue Test Rig. Experimental data were collected during experiments performed in this test rig with and without pitting. Results show combining the two measurement technologies improves the detection of pitting damage on spur gears.

Measurement of the time-temperature dependent dynamic mechanical properties of boron/aluminum composites

NASA Technical Reports Server (NTRS)

Dicarlo, J. A.; Maisel, J. E.

1978-01-01

A flexural vibration test and associated equipment were developed to accurately measure the low strain dynamic modulus and damping of composite materials from -200 C to over 500 C. The basic test method involves the forced vibration of composite bars at their resonant free-free flexural modes in a high vacuum cryostat furnace. The accuracy of these expressions and the flexural test was verified by dynamic moduli and damping capacity measurements on 50 fiber volume percent boron/aluminum (B/Al) composites vibrating near 2000 Hz. The phase results were summarized to permit predictions of the B/Al dynamic behavior as a function of frequency, temperature, and fiber volume fraction.

Vibration characteristics of OH-58A helicopter main rotor transmission

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Coy, John J.

1987-01-01

Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.

Objectives and Progress on Integrated Vehicle Ground Vibration Testing for the Ares Launch Vehicles

NASA Technical Reports Server (NTRS)

Tuma, Margaret L.; Asloms. Brice R.

2009-01-01

As NASA begins design and development of the Ares launch vehicles to replace the Space Shuttle and explore beyond low Earth orbit, Integrated Vehicle Ground Vibration Testing (IVGVT) will be a vital component of ensuring that those vehicles can perform the missions assigned to them. A ground vibration test (GVT) is intended to measure by test the fundamental dynamic characteristics of launch vehicles during various phases of flight. During the series of tests, properties such as natural frequencies, mode shapes, and transfer functions are measured directly. This data is then used to calibrate loads and control systems analysis models for verifying analyses of the launch vehicle. The Ares Flight & Integrated Test Office (FITO) will be conducting IVGVT for the Ares I crew launch vehicle at Marshall Space Flight Center (MSFC) from 2011 to 2012 using the venerable Test Stand (TS) 4550, which supported similar tests for the Saturn V and Space Shuttle vehicle stacks.

Magnetic Actuators and Suspension for Space Vibration Control

NASA Technical Reports Server (NTRS)

Knospe, Carl R.; Allaire, Paul E.; Lewis, David W.

1993-01-01

The research on microgravity vibration isolation performed at the University of Virginia is summarized. This research on microgravity vibration isolation was focused in three areas: (1) the development of new actuators for use in microgravity isolation; (2) the design of controllers for multiple-degree-of-freedom active isolation; and (3) the construction of a single-degree-of-freedom test rig with umbilicals. Described are the design and testing of a large stroke linear actuator; the conceptual design and analysis of a redundant coarse-fine six-degree-of-freedom actuator; an investigation of the control issues of active microgravity isolation; a methodology for the design of multiple-degree-of-freedom isolation control systems using modern control theory; and the design and testing of a single-degree-of-freedom test rig with umbilicals.

Active member vibration control for a 4 meter primary reflector support structure

NASA Technical Reports Server (NTRS)

Umland, J. W.; Chen, G.-S.

1992-01-01

The design and testing of a new low voltage piezoelectric active member with integrated load cell and displacement sensor is described. This active member is intended for micron level vibration and structural shape control of the Precision Segmented Reflector test-bed. The test-bed is an erectable 4 meter diameter backup support truss for a 2.4 meter focal length parabolic reflector. Active damping of the test-bed is then demonstrated using the newly developed active members. The control technique used is referred to as bridge feedback. With this technique the internal sensors are used in a local feedback loop to match the active member's input impedance to the structure's load impedance, which then maximizes vibrational energy dissipation. The active damping effectiveness is then evaluated from closed loop frequency responses.

Nerve regeneration in nerve grafts conditioned by vibration exposure.

PubMed

Bergman, S; Widerberg, A; Danielsen, N; Lundborg, G; Dahlin, L B

1995-01-01

Regeneration distances were studied in nerves from vibration-exposed limbs. One hind limb of anaesthetized rats was attached to a vibration exciter and exposed to vibration (80 Hz/32 m/s2) for 5 h/day for 2 or 5 days. Seven days after the latest vibration period a 10-mm long nerve graft was taken from the vibrated sciatic nerve and sutured into a corresponding defect in the con-tralateral sciatic nerve and vice versa, thereby creating two different models within the same animal: (i) regeneration from a freshly transected unvibrated nerve into a vibrated graft and (ii) regeneration from a vibrated nerve into a fresh nerve graft (vibrated recipient side). Four, 6 or 8 days postoperatively (p.o.) the distances achieved by the regenerating axons were determined using the pinch reflex test. Two days of vibration did not influence the regeneration, but 5 days of vibration reduced the initial delay period and a slight reduction of regeneration rate was observed. After 5 days of vibration an increased regeneration distance was observed in both models at day 4 p.o. and at day 6 p.o. in vibrated grafts. This study demonstrates that vibration can condition peripheral nerves and this may be caused by local changes in the peripheral nerve trunk and in the neuron itself.

Investigation of difficult component effects on finite element model vibration prediction for the Bell AG-1G helicopter. Volume 2: Correlation results

NASA Technical Reports Server (NTRS)

Dompka, R. V.

1989-01-01

Under the NASA-sponsored DAMVIBS (Design Analysis Methods for VIBrationS) program, a series of ground vibration tests and NASTRAN finite element model (FEM) correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Previous correlations of the AG-1G showed good agreement between NASTRAN and tests through 15 to 20 Hz, but poor agreement in the higher frequency range of 20 to 30 Hz. Thus, this effort emphasized the higher frequency airframe vibration response correlations and identified areas that need further R and T work. To conduct the investigations, selected difficult components (main rotor pylon, secondary structure, nonstructural doors/panels, landing gear, engine, furl, etc.) were systematically removed to quantify their effects on overall vibratory response of the airframe. The entire effort was planned and documented, and the results reviewed by NASA and industry experts in order to ensure scientific control of the testing, analysis, and correlation exercise. In particular, secondary structure and damping had significant effects on the frequency response of the airframe above 15 Hz. Also, the nonlinear effects of thrust stiffening and elastomer mounts were significant on the low frequency pylon modes below main rotor 1p (5.4 Hz). The results of the NASTRAN FEM correlations are given.

SHIIVER (Structural Heat Intercept Insulation Vibration Evaluation Rig)

NASA Image and Video Library

2017-06-11

SHIIVER (Structural Heat Intercept Insulation Vibration Evaluation Rig) is a cryogenic test tank developed to evaluate heat intercept concepts. It arrived at Marshall Space Flight Center on August 10, 2017. The tank will receive heat sensors and spray-on foam insulation before making its way to Plum Brook station for further insulation and testing.

Engine-Vibration Analyzer

NASA Technical Reports Server (NTRS)

Tolmei, V. R.

1982-01-01

Proposed circuit would monitor vibration spectrum of engines under test or in service. It could detect subtle out-of-specification conditions and could be programed to shut down engine if an out-of-limits condition develops. Possible uses of monitor are in bench testing automobiles and outboard motors and as a safety device in very critical engine applications.

49 CFR Appendix C to Part 173 - Procedure for Base-level Vibration Testing

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Procedure for Base-level Vibration Testing C Appendix C to Part 173 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS...-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Pt. 173, App. C Appendix C to Part 173—Procedure for...

49 CFR Appendix C to Part 173 - Procedure for Base-level Vibration Testing

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Procedure for Base-level Vibration Testing C Appendix C to Part 173 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS...-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Pt. 173, App. C Appendix C to Part 173—Procedure for...

Servomotors. (Latest Citations from the Aerospace Database)

NASA Technical Reports Server (NTRS)

1996-01-01

The bibliography contains citations concerning the design, testing, and application of servomotors. AC, DC, and brushless motor drives are discussed. Applications are examined, including use in hydraulic presses; teleprinters; machine tools; sewing machines; and servocontrol devices for instrumentation, robots, and aircraft control. Testing methods evaluate precision, vibration and vibration reduction, and stability of servomotors.

3D digital image correlation methods for full-field vibration measurement

NASA Astrophysics Data System (ADS)

Helfrick, Mark N.; Niezrecki, Christopher; Avitabile, Peter; Schmidt, Timothy

2011-04-01

In the area of modal test/analysis/correlation, significant effort has been expended over the past twenty years in order to make reduced models and to expand test data for correlation and eventual updating of the finite element models. This has been restricted by vibration measurements which are traditionally limited to the location of relatively few applied sensors. Advances in computers and digital imaging technology have allowed 3D digital image correlation (DIC) methods to measure the shape and deformation of a vibrating structure. This technique allows for full-field measurement of structural response, thus providing a wealth of simultaneous test data. This paper presents some preliminary results for the test/analysis/correlation of data measured using the DIC approach along with traditional accelerometers and a scanning laser vibrometer for comparison to a finite element model. The results indicate that all three approaches correlated well with the finite element model and provide validation for the DIC approach for full-field vibration measurement. Some of the advantages and limitations of the technique are presented and discussed.

Ground and flight test results of a total main rotor isolation system

NASA Technical Reports Server (NTRS)

Halwes, Dennis R.

1987-01-01

A six degree-of-freedom (DOF) isolation system using six LIVE units has been installed under an Army/NASA contract on a Bell 206LM helicopter. This system has been named the Total Rotor Isolation System, or TRIS. To determine the effectiveness of TRIS in reducing helicopter vibration, a flight verification study was conducted at Bell's Flight Research Center in Arlington, Texas. The flight test data indicate that the 4/rev vibration level at the pilot's seat were suppressed below the 0.04g level throughout the transition envelope. Flight tests indicate over 95% suppression of vibration level from the rotor hub to the pilot's seat. The TRIS installation was designed with a decoupled control system and has shown a significant improvement in aircraft flying qualities, such that it permitted the trimmed aircraft to be flown hands-off for a significant period of time, over 90 seconds. The TRIS flight test program has demonstrated a system that greatly reduces vibration levels of a current-generation helicopter, while significantly improving the flying qualities to a point where stability augmentation is no longer a requirement.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, crawl out of the Vehicle Assembly Building (VAB) in support of the second engineering analysis vibration test on the crawler and MLP. In the background is another MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, crawl out of the Vehicle Assembly Building (VAB) in support of the second engineering analysis vibration test on the crawler and MLP. In the background is another MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. On either side of the boosters on the horizon can be seen the two launch pads. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. On either side of the boosters on the horizon can be seen the two launch pads. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician monitors the performance of a crawler-transporter as it moves Mobile Launcher Platform (MLP) number 3, with a set of twin solid rocket boosters bolted atop, to the intersection in the crawlerway during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A, and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician monitors the performance of a crawler-transporter as it moves Mobile Launcher Platform (MLP) number 3, with a set of twin solid rocket boosters bolted atop, to the intersection in the crawlerway during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A, and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters bolted to it, atop the crawler-transporter, inches along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The MLP is viewed from the KSC News Center across the turn basin. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters bolted to it, atop the crawler-transporter, inches along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The MLP is viewed from the KSC News Center across the turn basin. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician walks towards the intersection of the crawlerway beside a crawler-transporter moving Mobile Launcher Platform (MLP) number 3, with a set of twin solid rocket boosters bolted atop, during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A, and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician walks towards the intersection of the crawlerway beside a crawler-transporter moving Mobile Launcher Platform (MLP) number 3, with a set of twin solid rocket boosters bolted atop, during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A, and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (on the horizon at right; Pad 39B is at far left), and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A (on the horizon at right; Pad 39B is at far left), and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Ambient Vibration Tests of an Arch Dam with Different Reservoir Water Levels: Experimental Results and Comparison with Finite Element Modelling

PubMed Central

Ranieri, Gaetano

2014-01-01

This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012) and at the end of winter (March 2013), respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series. In-contact single-station measurements were done by means of one single high resolution triaxial tromometer and two low-frequency seismometers, placed in different points of the structure. The Standard Spectral Ratio method has been used to evaluate the natural frequencies of vibration of the structure. A 3D finite element model of the arch dam-reservoir-foundation system has been developed to verify analytically determined vibration properties, such as natural frequencies and mode shapes, and their changes linked to water level with the experimental results. PMID:25003146

Evaluation of EDR-3 vibration, shock, temperature, and humidity recording unit

NASA Technical Reports Server (NTRS)

Rees, Kevin G.; Mondale, C. F.

1990-01-01

The purpose of this evaluation was to determine if the self-contained, off-the-shelf, Environmental Data Recorder 3 (EDR-3) could be qualified to monitor shock, vibration, and temperature during rail transportation of space shuttle solid rocket components. The evaluation testing started in November 1989 and continued until June 1990. Two EDR-3 units were used to monitor both on- and off-plant shipments of shuttle components. In addition, extensive testing was performed at Thiokol's Vibration Test facility, T-53. Testing demonstrated that the EDR-3 is capable of successfully monitoring actual shipments of solid rocket hardware. Thiokol metrology has verified the accuracy of temperature monitoring. In addition, calibrated shock/vibration testing demonstrated that the EDR-3 does accurately record acceleration. It is recommended that the vendor modify the EDR-3 data recovery system to allow remote communication via a 30-foot cable. This would permit communication with the unit mounted on a case segment after a rail car cover is installed. The vendor will make this change and produce a new model, designated EDR-3-10. It is further recommended that Thiokol qualify the EDR-3-10 for transportation monitoring of redesigned solid rocket motor (RSRM) components.

A new portable vibrator for plaster pouring: effect on the marginal fit at cylinder-abutment

PubMed Central

de ANDRADE, Pâmela Cândida Aires Ribas; LUTHI, Leonardo Flores; STANLEY, Kyle; CARDOSO, Antônio Carlos

2012-01-01

Objective The aim of this study was to test a new portable vibrator for plaster pouring (developed for this purpose), comparing the effect of its use on the accuracy of working cast of implant-supported restorations to the conventional vibrator. Material and methods From a master cast with 2 implants, 30 transfer moldings were made randomly and divided into three groups: Group I (GI): pouring performed in an outsourced dental laboratory with conventional plaster vibrator (10 casts), Group II (GII): pouring performed in the laboratory of the Federal University of Santa Catarina (UFSC) with conventional plaster vibrator (10 casts) and Group III (GIII): pouring performed with the portable vibrator fabricated for this study (10 casts). The position of the analogue and marginal adaptation of the infrastructure were verified by testing the single screw on the master model and on the working model. The measurement of misfit was blindly performed with a precision microscope and analyzing unit, Quadra-Check 200. The data were statistically analyzed by analysis of variance (ANOVA) and the Holm-Sidak test (α=0.05). Results Means±standard deviations were as follows: GI: 19.19±4.73 µm; GII: 21.72±5.41 µm; GIII: 13.5±2.39 µm (P<0.05), with GIII significantly lower as compared to the other groups. Conclusion Within the limitations of this study, it was concluded that a greater accuracy of working cast was achieved when a portable vibrator was used for casting molds. PMID:23138736

Detecting Gear Tooth Fatigue Cracks in Advance of Complete Fracture

NASA Technical Reports Server (NTRS)

Zakrajsek, James J.; Lewicki, David G.

1996-01-01

Results of using vibration-based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the fillet area of a tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-line and after the tests were completed. The objectives of this effort were to identify methods capable of detecting the fatigue crack and to determine how far in advance of total failure positive detection was given. Results show that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture in the thin rim gear tests. In the standard full rim gear test all of the methods responded to the fatigue crack in advance of tooth fracture; however, only three of the methods responded to the fatigue crack in the early stages of crack propagation.

Experimental investigations on the damping effect due to passengers on flexural vibrations of railway vehicle carbody and basic studies on the mimicry of the effect with simple substitutions

NASA Astrophysics Data System (ADS)

Tomioka, T.; Takigami, T.; Aida, K.

2017-07-01

The effect of passengers on a railway vehicle is usually considered as additional mass in designing a carbody. However, previous studies by means of stationary excitation tests or running tests using actual vehicles indicate that passengers behave not as mass but as damping. In this paper, the authors examined the passengers' damping effect under controlled excitation conditions on a roller rig through a series of excitation tests using a commuter-type vehicle. Large and multi-modal reductions of flexural vibrations of the carbody were observed when passengers existed. Influences of the number of passengers, distributions and postures of passengers were investigated. The authors also tried to mimic the damping effect by passengers using flexible tanks filled with fluids. Three kinds of fluids which have different viscosities have been tested. As a result of the excitation tests, good vibration reduction effects were observed by applying those tanks, and it has been found that the flexible tanks filled with fluids bring about vibration reduction effect (including multi-modal reduction) which is equal to or rather better than the case of similar mass of passengers in the carbody; the difference of viscosity gave little affect on the damping abilities. From these measurement results, a possibility of realising effective damping devices against flexural vibrations of railway vehicle carbodies representing passengers damping effect, in a simple, economical and environmental friendly way, has been demonstrated.

An examination of the vibration transmissibility of the hand-arm system in three orthogonal directions.

PubMed

Welcome, Daniel E; Dong, Ren G; Xu, Xueyan S; Warren, Christopher; McDowell, Thomas W; Wu, John Z

2015-02-01

The objective of this study is to enhance the understanding of the vibration transmission in the hand-arm system in three orthogonal directions ( X, Y , and Z ). For the first time, the transmitted vibrations distributed on the entire hand-arm system exposed in the three orthogonal directions via a 3-D vibration test system were measured using a 3-D laser vibrometer. Seven adult male subjects participated in the experiment. This study confirms that the vibration transmissibility generally decreased with the increase in distance from the hand and it varied with the vibration direction. Specifically, to the upper arm and shoulder, only moderate vibration transmission was measured in the test frequency range (16 to 500 Hz), and virtually no transmission was measured in the frequency range higher than 50 Hz. The resonance vibration on the forearm was primarily in the range of 16-30 Hz with the peak amplitude of approximately 1.5 times of the input vibration amplitude. The major resonance on the dorsal surfaces of the hand and wrist occurred at around 30-40 Hz and, in the Y direction, with peak amplitude of more than 2.5 times of the input amplitude. At higher than 50 Hz, vibration transmission was effectively limited to the hand and fingers. A major finger resonance was observed at around 100 Hz in the X and Y directions and around 200 Hz in the Z direction. In the fingers, the resonance magnitude in the Z direction was generally the lowest, and the resonance magnitude in the Y direction was generally the highest with the resonance amplitude of 3 times the input vibration, which was similar to the transmissibility at the wrist and hand dorsum. The implications of the results are discussed. Prolonged, intensive exposure to hand-transmitted vibration could result in hand-arm vibration syndrome. While the syndrome's precise mechanisms remain unclear, the characterization of the vibration transmissibility of the system in the three orthogonal dimensions performed in this study can help understand the syndrome and help develop improved frequency weightings for assessing the risk of the exposure for developing various components of the syndrome.

An examination of the vibration transmissibility of the hand-arm system in three orthogonal directions

PubMed Central

Welcome, Daniel E.; Dong, Ren G.; Xu, Xueyan S.; Warren, Christopher; McDowell, Thomas W.; Wu, John Z.

2015-01-01

The objective of this study is to enhance the understanding of the vibration transmission in the hand-arm system in three orthogonal directions (X, Y, and Z). For the first time, the transmitted vibrations distributed on the entire hand-arm system exposed in the three orthogonal directions via a 3-D vibration test system were measured using a 3-D laser vibrometer. Seven adult male subjects participated in the experiment. This study confirms that the vibration transmissibility generally decreased with the increase in distance from the hand and it varied with the vibration direction. Specifically, to the upper arm and shoulder, only moderate vibration transmission was measured in the test frequency range (16 to 500 Hz), and virtually no transmission was measured in the frequency range higher than 50 Hz. The resonance vibration on the forearm was primarily in the range of 16–30 Hz with the peak amplitude of approximately 1.5 times of the input vibration amplitude. The major resonance on the dorsal surfaces of the hand and wrist occurred at around 30–40 Hz and, in the Y direction, with peak amplitude of more than 2.5 times of the input amplitude. At higher than 50 Hz, vibration transmission was effectively limited to the hand and fingers. A major finger resonance was observed at around 100 Hz in the X and Y directions and around 200 Hz in the Z direction. In the fingers, the resonance magnitude in the Z direction was generally the lowest, and the resonance magnitude in the Y direction was generally the highest with the resonance amplitude of 3 times the input vibration, which was similar to the transmissibility at the wrist and hand dorsum. The implications of the results are discussed. Relevance to industry Prolonged, intensive exposure to hand-transmitted vibration could result in hand-arm vibration syndrome. While the syndrome's precise mechanisms remain unclear, the characterization of the vibration transmissibility of the system in the three orthogonal dimensions performed in this study can help understand the syndrome and help develop improved frequency weightings for assessing the risk of the exposure for developing various components of the syndrome. PMID:26635424

Acute bone response to whole body vibration in healthy pre-pubertal boys

PubMed Central

Harrison, R.; Ward, K.; Lee, E.; Razaghi, H.; Horne, C.; Bishop, N.J.

2015-01-01

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

The effects of whole-body vibration on the Wingate test for anaerobic power when applying individualized frequencies.

PubMed

Surowiec, Rachel K; Wang, Henry; Nagelkirk, Paul R; Frame, Jeffrey W; Dickin, D Clark

2014-07-01

Recently, individualized frequency (I-Freq) has been introduced with the notion that athletes may elicit a greater reflex response at differing levels (Hz) of vibration. The aim of the study was to evaluate acute whole-body vibration as a feasible intervention to increase power in trained cyclists and evaluate the efficacy of using I-Freq as an alternative to 30Hz, a common frequency seen in the literature. Twelve highly trained, competitive male cyclists (age, 29.9 ± 10.0 years; body height, 175.4 ± 7.8 cm; body mass, 77.3 ± 13.9 kg) participated in the study. A Wingate test for anaerobic power was administered on 3 occasions: following a control of no vibration, 30 Hz, or I-freq. Measures of peak power, average power (AP), and the rate of fatigue were recorded and compared with the vibration conditions using separate repeated measures analysis of variance. Peak power, AP, and the rate of fatigue were not significantly impacted by either the 30 Hz or I-Freq vibration interventions (p > 0.05). Given the trained status of the individuals in this study, the ability to elicit an acute response may have been muted. Future studies should further refine the vibration parameters used and assess changes in untrained or recreationally trained populations.

The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program : Bell Helicopter Textron accomplishments

NASA Technical Reports Server (NTRS)

Cronkhite, James D.

1993-01-01

Accurate vibration prediction for helicopter airframes is needed to 'fly from the drawing board' without costly development testing to solve vibration problems. The principal analytical tool for vibration prediction within the U.S. helicopter industry is the NASTRAN finite element analysis. Under the NASA DAMVIBS research program, Bell conducted NASTRAN modeling, ground vibration testing, and correlations of both metallic (AH-1G) and composite (ACAP) airframes. The objectives of the program were to assess NASTRAN airframe vibration correlations, to investigate contributors to poor agreement, and to improve modeling techniques. In the past, there has been low confidence in higher frequency vibration prediction for helicopters that have multibladed rotors (three or more blades) with predominant excitation frequencies typically above 15 Hz. Bell's findings under the DAMVIBS program, discussed in this paper, included the following: (1) accuracy of finite element models (FEM) for composite and metallic airframes generally were found to be comparable; (2) more detail is needed in the FEM to improve higher frequency prediction; (3) secondary structure not normally included in the FEM can provide significant stiffening; (4) damping can significantly affect phase response at higher frequencies; and (5) future work is needed in the areas of determination of rotor-induced vibratory loads and optimization.

In-service tests of the effectiveness of vibration control measures on the BART rail transit system

NASA Astrophysics Data System (ADS)

Saurenman, Hugh

2005-09-01

Controlling vibration from new rail transit systems can be quite expensive when the alignment passes through residential areas. However, there is relatively little documented information on how effective different vibration mitigation approaches perform under in-service conditions. This paper presents results of a number of vibration measurements of the different track forms used on the current San Francisco Bay Area Rapid Transit (BART) system including floating slab, resiliently supported half ties, and high-resilience direct fixation fasteners in subways and one section of floating slab used on at-grade tracks. The goal was to obtain data that would improve the predictions of future vibration levels and perhaps lead to more cost effective vibration mitigation strategies for the proposed BART extension to San Jose. The tests show that the floating slabs are performing much as designed, the resiliently supported half ties are less effective than expected, and the high resilience track fasteners are probably performing as expected, although the results are clouded because of severe rail corrugation in the area where the new fasteners were installed. Some unanticipated results are the apparent interaction of the floating slab resonance, the wheel rotation frequency, the bogey dynamics, and vibration propagation characteristics of the ground.

Wireless Network for Measurement of Whole-Body Vibration

PubMed Central

Koenig, Diogo; Chiaramonte, Marilda S.; Balbinot, Alexandre

2008-01-01

This article presents the development of a system integrated to a ZigBee network to measure whole-body vibration. The developed system allows distinguishing human vibrations of almost 400Hz in three axes with acceleration of almost 50g. The tests conducted in the study ensured the correct functioning of the system for the project's purpose. PMID:27879866

The vibrational properties of Chinese fir wood during moisture sorption process

Treesearch

Jiali Jiang; Jianxiong Lu; Zhiyong Cai

2012-01-01

The vibrational properties of Chinese fir (Cunninghamia lanceolata) wood were investigated in this study as a function of changes in moisture content (MC) and grain direction. The dynamic modulus of elasticity (DMOE) and logarithmic decrement σ were examined using a cantilever beam vibration testing apparatus. It was observed that DMOE and 6 of wood vaned...

Materials Testing in Long Cane Design: Sensitivity, Flexibility, and Transmission of Vibration

ERIC Educational Resources Information Center

Rodgers, Mark D.; Emerson, Robert Wall

2005-01-01

Different materials that are used in manufacturing long cane shafts were assessed for their ability to transmit vibration and their sensitivity to tactile information, flexibility, and durability. It was found that the less flexible a cane shaft is, the better it transmits vibrations that are useful for discriminating surface textures and that…

The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program: McDonnell-Douglas Helicopter Company achievements

NASA Technical Reports Server (NTRS)

Toossi, Mostafa; Weisenburger, Richard; Hashemi-Kia, Mostafa

1993-01-01

This paper presents a summary of some of the work performed by McDonnell Douglas Helicopter Company under NASA Langley-sponsored rotorcraft structural dynamics program known as DAMVIBS (Design Analysis Methods for VIBrationS). A set of guidelines which is applicable to dynamic modeling, analysis, testing, and correlation of both helicopter airframes and a large variety of structural finite element models is presented. Utilization of these guidelines and the key features of their applications to vibration modeling of helicopter airframes are discussed. Correlation studies with the test data, together with the development and applications of a set of efficient finite element model checkout procedures, are demonstrated on a large helicopter airframe finite element model. Finally, the lessons learned and the benefits resulting from this program are summarized.

Finite element analysis using NASTRAN applied to helicopter transmission vibration/noise reduction

NASA Technical Reports Server (NTRS)

Howells, R. W.; Sciarra, J. J.

1975-01-01

A finite element NASTRAN model of the complete forward rotor transmission housing for the Boeing Vertol CH-47 helicopter was developed and applied to reduce transmission vibration/noise at its source. In addition to a description of the model, a technique for vibration/noise prediction and reduction is outlined. Also included are the dynamic response as predicted by NASTRAN, test data, the use of strain energy methods to optimize the housing for minimum vibration/noise, and determination of design modifications which will be manufactured and tested. The techniques presented are not restricted to helicopters but are applicable to any power transmission system. The transmission housing model developed can be used further to evaluate static and dynamic stresses, thermal distortions, deflections and load paths, fail-safety/vulnerability, and composite materials.

High-Temperature Modal Survey of a Hot-Structure Control Surface

NASA Technical Reports Server (NTRS)

Spivey, Natalie Dawn

2010-01-01

Ground vibration tests or modal surveys are routinely conducted for supporting flutter analysis for subsonic and supersonic vehicles; however, for hypersonic vehicle applications, thermoelastic vibration testing techniques are not well established and are not routinely performed for supporting hypersonic flutter analysis. New high-temperature material systems, fabrication technologies and high-temperature sensors expand the opportunities to develop advanced techniques for performing ground vibration tests at elevated temperatures. High-temperature materials have the unique property of increasing in stiffness when heated. When these materials are incorporated into a hot-structure, which includes metallic components that decrease in stiffness with increasing temperature, the interaction between the two materials systems needs to be understood because that interaction could ultimately affect the hypersonic flutter analysis. Performing a high-temperature modal survey will expand the research database for hypersonics and will help build upon the understanding of the dual material interaction. This paper will discuss the vibration testing of the Carbon-Silicon Carbide Ruddervator Subcomponent Test Article which is a truncated version of the full-scale X-37 hot-structure control surface. In order to define the modal characteristics of the test article during the elevated-temperature modal survey, two series of room-temperature modal test configurations had to be performed. The room-temperature test series included one with the test article suspended from a bungee cord (free-free) and the second with it mounted on the strongback (fixed boundary condition) in NASA Dryden's Flight Loads Lab large nitrogen test chamber.

Analysis of Piezoelectric Actuator for Vibration Control of Composite plate

NASA Astrophysics Data System (ADS)

Gomaa, Ahmed R.; Hai, Huang

2017-07-01

Vibration analysis is studied numerically in this paper for a simply supported composite plate subjected to external loadings. Vibrations are controlled by using piezoelectric patches. Finite element method (ANSYS) is used for obtaining finite element model of the smart plate structure, a layered composite plate is manufactured experimentally and tested to obtain the structure mechanical properties. Different piezoelectric patch areas and different applied gain voltage effects on vibration attenuation is studied. The numerical solution is compared with the experimental work, a good agreement achieved.

Investigation of vibration characteristics of electric motors

NASA Technical Reports Server (NTRS)

Bakshis, A. K.; Tamoshyunas, Y. K.

1973-01-01

The vibration characteristics of electric motors were analyzed using mathematical statistics methods. The equipment used and the method of conducting the test are described. Curves are developed to show the visualization of the electric motor vibrations in the vertical direction. Additional curves are included to show the amplitude-phase frequency characteristic of dynamic rotor-housing vibrations at the first lug and the same data for the second lug of the electric motor. Mathematical models were created to show the transmission function of the dynamic rotor housing system.

Ground vibrations from heavy freight trains

NASA Astrophysics Data System (ADS)

Dawn, T. M.

1983-03-01

Ground vibration from heavy freight trains on good quality welded track are found to have only a weak dependence on train speed above 30 km/h. At the site on which these tests were carried out a critical speed was found at which the vibration reached a peak. The frequencies of vibration produced appear to be functions of track and vehicle dimensions and the critical speed occurs at the coincidence of sleeper passage frequency and the total vehicle on track resonance frequency.

Local vibration inhibits H-reflex but does not compromise manual dexterity and does not increase tremor.

PubMed

Budini, Francesco; Laudani, Luca; Bernardini, Sergio; Macaluso, Andrea

2017-10-01

The present work aimed at investigating the effects of local vibration on upper limb postural and kinetic tremor, on manual dexterity and on spinal reflex excitability. Previous studies have demonstrated a decrease in spinal reflex excitability and in force fluctuations in the lower limb but an increase in force fluctuation in the upper limbs. As hand steadiness is of vital importance in many daily-based tasks, and local vibration may also be applied in movement disorders, we decided to further explore this phenomenon. Ten healthy volunteers (26±3years) were tested for H reflex, postural and kinetic tremor and manual dexterity through a Purdue test. EMG was recorded from flexor carpi radialis (FCR) and extensor digitorum communis (EDC). Measurements were repeated at baseline, after a control period during which no vibration was delivered and after vibration. Intervention consisted in holding for two minutes a vibrating handle (frequency 75Hz, displacement∼7mm), control consisted in holding for two minutes the same handle powered off. Reflex excitability decreased after vibration whilst postural tremor and manual dexterity were not affected. Peak kinetic tremor frequency increased from baseline to control measurements (P=0.002). Co-activation EDC/FCR increased from control to vibration (P=0.021). These results show that two minutes local vibration lead to a decrease in spinal excitability, did not compromise manual dexterity and did not increase tremor; however, in contrast with expectations, tremor did not decrease. It is suggested that vibration activated several mechanisms with opposite effects, which resulted in a neutral outcome on postural and kinetic tremor. Copyright © 2017 Elsevier B.V. All rights reserved.

Exposure to whole-body vibration and seat transmissibility in a large sample of earth scrapers.

PubMed

Salmoni, Alan; Cann, Adam; Gillin, Kent

2010-01-01

It is often difficult to access a large sample of vehicles in various work environments to evaluate worker exposure to vibration such as in construction and mining. Thus the main purpose of the present research was to test vibration exposure in a relatively large number of earth scrapers. The second aim was to assess vibration exposure values on seat transmissibility. 33earth scrapers were assessed for both exposure to whole-body vibration and seat transmissibility. Two triaxial accelerometers, one placed on the seat and one on the floor directly below the seat, were used to gather whole-body vibration values (a(w)). Each machine was tested for a minimum of three complete work cycles: idling, scraping, travelling full, dumping, travelling empty back to the scrape site. Results showed that idling and scraping produced low levels of vibration when compared to travelling and dumping. Second, when the a(w) values were compared to the EU safety standards for an eight hour work day, the data (z axis) exceeded the exposure action value (0.5 m/s2) in all machines, and the exposure limit value (1.15 m/s2) in some. Implications; Operators of the scrapers were being exposed to unsafe levels of whole-body vibration. When the seats were assessed to see whether they were attenuating operator exposure to vibration, many of the seat effective amplitude transmissibility (SEAT) values exceeded 1.0. This meant that some of the seats were actually amplifying the vibration present at the floor, particularly in the y axis. Travelways should be kept smooth, operating speeds reduced, and new seats, effective in all three axes, designed.

Force Limited Random Vibration Test of TESS Camera Mass Model

NASA Technical Reports Server (NTRS)

Karlicek, Alexandra; Hwang, James Ho-Jin; Rey, Justin J.

2015-01-01

The Transiting Exoplanet Survey Satellite (TESS) is a spaceborne instrument consisting of four wide field-of-view-CCD cameras dedicated to the discovery of exoplanets around the brightest stars. As part of the environmental testing campaign, force limiting was used to simulate a realistic random vibration launch environment. While the force limit vibration test method is a standard approach used at multiple institutions including Jet Propulsion Laboratory (JPL), NASA Goddard Space Flight Center (GSFC), European Space Research and Technology Center (ESTEC), and Japan Aerospace Exploration Agency (JAXA), it is still difficult to find an actual implementation process in the literature. This paper describes the step-by-step process on how the force limit method was developed and applied on the TESS camera mass model. The process description includes the design of special fixtures to mount the test article for properly installing force transducers, development of the force spectral density using the semi-empirical method, estimation of the fuzzy factor (C2) based on the mass ratio between the supporting structure and the test article, subsequent validating of the C2 factor during the vibration test, and calculation of the C.G. accelerations using the Root Mean Square (RMS) reaction force in the spectral domain and the peak reaction force in the time domain.

The Dornier 328 Acoustic Test Cell (ATC) for interior noise tests and selected test results

NASA Technical Reports Server (NTRS)

Hackstein, H. Josef; Borchers, Ingo U.; Renger, Klaus; Vogt, Konrad

1992-01-01

To perform acoustic studies for achieving low noise levels for the Dornier 328, an acoustic test cell (ATC) of the Dornier 328 has been built. The ATC consists of a fuselage section, a realistic fuselage suspension system, and three exterior noise simulation rings. A complex digital 60 channel computer/amplifier noise generation system as well as multichannel digital data acquisition and evaluation system have been used. The noise control tests started with vibration measurements for supporting acoustic data interpretation. In addition, experiments have been carried out on dynamic vibration absorbers, the most important passive noise reduction measure for low frequency propeller noise. The design and arrangement of the current ATC are presented. Furthermore, exterior noise simulation as well as data acquisition are explained. The most promising results show noise reduction due to synchrophasing and dynamic vibration absorbers.

Vibration isolation/suppression: research experience for undergraduates in mechatronics and smart structures

NASA Astrophysics Data System (ADS)

Fonda, James; Rao, Vittal S.; Sana, Sridhar

2001-08-01

This paper provides an account of a student research project conducted under the sponsoring of the National Science Foundation (NSF) program on Research Experience for Undergraduates (REU) in Mechatronics and Smart Strictures in the summer of 2000. The objective of the research is to design and test a stand-alone controller for a vibration isolation/suppression system. The design specification for the control system is to suppress the vibrations induced by the external disturbances by at least fiver times and hence to achieve vibration isolation. Piezo-electric sensors and actuators are utilized for suppression of unwanted vibrations. Various steps such as modeling of the system, controller design, simulation, closed-loop testing using d- Space rapid prototyping system, and analog control implementation are discussed in the paper. Procedures for data collection, the trade-offs carried out in the design, and analog controller implementation issues are also presented in the paper. The performances of various controllers are compared. The experiences of an undergraduate student are summarized in the conclusion of the paper.

In-service tests of the effectiveness of vibration control measures on the BART rail transit system

NASA Astrophysics Data System (ADS)

Saurenman, Hugh; Phillips, James

2006-06-01

This paper presents results of a number of vibration measurements of the different track forms used on the current San Francisco Bay Area Rapid Transit (BART) system including floating slab, resiliently supported half-ties and high-resilience direct fixation fasteners in subway and one section of floating slab used on at-grade track. The goal was to obtain data that would improve the predictions of future vibration levels and perhaps lead to more cost effective vibration mitigation strategies for the proposed BART extension to San Jose. The tests show that the floating slabs are performing much as designed, the resiliently supported half-ties are less effective than expected, and the high resilience track fasteners are probably performing as expected although the results are clouded because of severe rail corrugation in the area where the new fasteners were installed. One unanticipated result is the apparent interaction of the floating slab resonance, the wheel rotation frequency, the bogie dynamics, and vibration propagation characteristics of the ground.

[Correction of physical performance of mice with the derivatives of 3-oxypyridine and pyridine].

PubMed

Stratienko, E N; Sizaeva, V E; Smirnov, L D; Kuz'min, V I; Samoĭlov, N N; Iasnetsov, V V

2002-01-01

Effects of 21 phenyl ethyl-substituted derivatives of 3-oxypyridine (3-OP), 6 adamantine derivatives of pyridine (PD) and actoprotectors bemithyl and bromanthane on physical performance (PP) were evaluated during treadmill testing of mice in ordinary conditions and following vibration. It was stated that in ordinary conditions PP was improved by eleven 3-OP derivatives and 3 adamantine PDs; nine 3-OP derivatives and 3 adamantine PDs had a positive effect following vibration. The actoprotective effect of the compounds depends on their chemical composition, dose and a background. A phenyl ethyl-substituted 3-OP derivative (code CK-132) administered in ordinary conditions and following vibration surpassed significantly the other compounds tested or compared with (bemithyl and bromanthane) in this experiment with regard to the spectrum of effective doses (5-100 mg/kg) and the actoprotective activity (PP improved by 32 to 110%). The compound (code CK-132) can be further test validated as an actoprotector against the impacts of vibration.

Eddy-current system for the vibration-testing of blades

DOEpatents

Jacobs, Martin E.

1977-01-01

This invention is an improved system for the vibration-testing of cantilevered non-ferrous articles by inducing eddy currents therein. The principal advantage of the system is that relatively little heat is generated in the article being vibrated. Thus, a more accurate measurement of the fatigue characteristics of the article is obtained. Furthermore, the generation of relatively little heat in the blade permits tests to be conducted in low-pressure atmospheres simulating certain actual processes environments. Heat-generation in the vibrated article is minimized by utilizing eddy currents which are generated by an electromagnet whose magnetic field varies but does not change polarity. The typical winding for the electromagnet is excited with pulsating d.c. That is, the winding is alternately charged by connecting it across a d.c. power supply and then discharged by connecting it across a circuit for receiving current generated in the winding by self-induction. Preferably, the discharge circuit is designed so that the waveform of the discharging current approximates that of the charging current.

Achilles tendon vibration-induced changes in plantar flexor corticospinal excitability.

PubMed

Lapole, Thomas; Temesi, John; Gimenez, Philippe; Arnal, Pierrick J; Millet, Guillaume Y; Petitjean, Michel

2015-02-01

Daily Achilles tendon vibration has been shown to increase muscle force, likely via corticospinal neural adaptations. The aim of the present study was to determine the extent by which corticospinal excitability is influenced during direct Achilles tendon vibration. Motor-evoked potentials (MEPs) were elicited in the soleus (SOL), gastrocnemius medialis (GM) and tibialis anterior (TA) by transcranial magnetic stimulation of the motor cortical area of the leg with and without Achilles tendon vibration at various frequencies (50, 80 and 110 Hz). Contralateral homologues were also investigated. SOL and GM MEP amplitude significantly increased by 226 ± 188 and 66 ± 39%, respectively, during Achilles tendon vibration, without any difference between the tested frequencies. No MEP changes were reported for TA or contralateral homologues. Increased SOL and GM MEP amplitude suggests increased vibration-induced corticospinal excitability independent of vibration frequency.

Rate coefficients of exchange reactions accounting for vibrational excitation of reagents and products

NASA Astrophysics Data System (ADS)

Kustova, E. V.; Savelev, A. S.; Kunova, O. V.

2018-05-01

Theoretical models for the vibrational state-resolved Zeldovich reaction are assessed by comparison with the results of quasi-classical trajectory (QCT) calculations. An error in the model of Aliat is corrected; the model is generalized taking into account NO vibrational states. The proposed model is fairly simple and can be easily implemented to the software for non-equilibrium flow modeling. It provides a good agreement with the QCT rate coefficients in the whole range of temperatures and reagent/product vibrational states. The developed models are tested in simulations of vibrational and chemical relaxation of air mixture behind a shock wave. The importance of accounting for excitated NO vibrational states and accurate prediction of Zeldovich reactions rates is shown.

Using the Saturn V and Titan III Vibroacoustic Databanks for Random Vibration Criteria Development

NASA Technical Reports Server (NTRS)

Ferbee, R C.

2009-01-01

This is an update to TN D-7159, "Development and Application of Vibroacoustic Structural Data Banks in Predicting Vibration Design and Test Criteria for Rocket Vehicle Structures", which was originally published in 1973. Errors in the original document have been corrected and additional data from the Titan III program have been included. Methods for using the vibroacoustic databanks for vibration test criteria development are shown, as well as all of the data with drawings and pictures of the measurement locations. An Excel spreadsheet with the data included is available from the author.

Preliminary vibration, acoustic, and shock design and test criteria for components on the Lightweight External Tank (LWT)

NASA Technical Reports Server (NTRS)

1981-01-01

The Space Shuttle LWT is divided into zones and subzones. Zones are designated primarily to assist in determining the applicable specifications. A subzone (general Specification) is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, specifications for appropriate subzone weight ranges are available. Along with the specifications are vibration, acoustic, shock, transportation, handling, and acceptance test requirements and procedures. A method of selecting applicable vibration, acoustic, and shock specifications is presented.

Scaling Techniques for Combustion Device Random Vibration Predictions

NASA Technical Reports Server (NTRS)

Kenny, R. J.; Ferebee, R. C.; Duvall, L. D.

2016-01-01

This work presents compares scaling techniques that can be used for prediction of combustion device component random vibration levels with excitation due to the internal combustion dynamics. Acceleration and unsteady dynamic pressure data from multiple component test programs are compared and normalized per the two scaling approaches reviewed. Two scaling technique are reviewed and compared against the collected component test data. The first technique is an existing approach developed by Barrett, and the second technique is an updated approach new to this work. Results from utilizing both techniques are presented and recommendations about future component random vibration prediction approaches are given.

Vibration Performance Comparison Study on Current Fiber Optic Connector Technologies

NASA Technical Reports Server (NTRS)

Ott, Melanie N.; Thomes Jr., William J.; LaRocca, Frank V.; Switzer, Robert C.; Chuska, Rick F.; Macmurphy, Shawn L.

2008-01-01

Fiber optic cables are increasingly being used in harsh environments where they are subjected to vibration. Understanding the degradation in performance under these conditions is essential for integration of the fibers into the given application. System constraints oftentimes require fiber optic connectors so subsystems can be removed or assembled as needed. In the present work, various types of fiber optic connectors were monitored in-situ during vibration testing to examine the transient change in optical transmission and the steady-state variation following the event. Inspection of the fiber endfaces and connectors was performed at chosen intervals throughout the testing.

Piezoelectric Instruments of High Natural Frequency Vibration Characteristics and Protection Against Interference by Mass Forces

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.

Actively Controlled Landing Gear for Aircraft Vibration Reduction

NASA Technical Reports Server (NTRS)

Horta, Lucas G.; Daugherty, Robert H.; Martinson, Veloria J.

1999-01-01

Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.

Robust energy-absorbing compensators for the ACTEX II test article

NASA Astrophysics Data System (ADS)

Blaurock, Carl A.; Miller, David W.; Nye, Ted

1995-05-01

The paper addresses the problem of satellite solar panel vibration. A multi-layer vibration control scheme is investigated using a flight test article. Key issues in the active control portion are presented in the paper. The paper discusses the primary control design drivers, which are the time variations in modal frequencies due to configuration and thermal changes. A local control design approach is investigated, but found to be unworkable due to sensor/actuator non-collocation. An alternate design process uses linear robust control techniques, by describing the modal shifts as uncertainties. Multiple modal design, alpha- shifted multiple model, and a feedthrough compensation scheme are examined. Ground and simulation tests demonstrate that the resulting controllers provide significant vibration reduction in the presence of expected system variations.

Novel railway-subgrade vibration monitoring technology using phase-sensitive OTDR

NASA Astrophysics Data System (ADS)

Wang, Zhaoyong; Lu, Bin; Zheng, Hanrong; Ye, Qing; Pan, Zhengqing; Cai, Haiwen; Qu, Ronghui; Fang, Zujie; Zhao, Howell

2017-04-01

High-speed railway is being developed rapidly; its safety, including infrastructure and train operation, is vital. This paper presents a railway-subgrade vibration monitoring scheme based on phase-sensitive OTDR for railway safety. The subgrade vibration is detected and rebuilt. Multi-dimension comprehensive analysis (MDCA) is proposed to identify the running train signals and illegal constructions along railway. To our best knowledge, it is the first time that a railway-subgrade vibration monitoring scheme is proposed. This scheme is proved effective by field tests for real-time train tracking and activities monitoring along railway. It provides a new passive distributed way for all-weather railway-subgrade vibration monitoring.

Testing of UH-60A helicopter transmission in NASA Lewis 2240-kW (3000-hp) facility

NASA Technical Reports Server (NTRS)

Mitchell, A. M.; Oswald, F. B.; Coe, H. H.

1986-01-01

The U.S. Army's UH-60A Black Hawk 2240-kW (3000-hp) class, twin-engine helicopter transmission was tested at the NASA Lewis Research Center. The vibration and efficiency test results will be used to enhance the data base for similar-class helicopters. Most of the data were obtained for a matrix of test conditions of 50 to 100 percent of rated rotor speed and 20 to 100 percent of rated input power. The transmission's mechanical efficiency at 100 percent of rated power was 97.3 and 97.5 percent with its inlet oil maintained at 355 and 372 K (180 and 210 F), respectively. The highest vibration reading was 72 g's rms at the upper housing side wall. Other vibration levels measured near the gear meshes are reported.

Vibration and stretching effects on flexibility and explosive strength in young gymnasts.

PubMed

Kinser, Ann M; Ramsey, Michael W; O'Bryant, Harold S; Ayres, Christopher A; Sands, William A; Stone, Michael H

2008-01-01

Effects of simultaneous vibration-stretching on flexibility and explosive strength in competitive female gymnasts were examined. Twenty-two female athletes (age = 11.3 +/- 2.6 yr; body mass = 35.3 +/- 11.6 kg; competitive levels = 3-9) composed the simultaneous vibration-stretching (VS) group, which performed both tests. Flexibility testing control groups were stretching-only (SF) (N = 7) and vibration-only (VF) (N = 8). Explosive strength-control groups were stretching-only (SES) (N = 8) and vibration-only (VES) (N = 7). Vibration (30 Hz, 2-mm displacement) was applied to four sites, four times for 10 s, with 5 s of rest in between. Right and left forward-split (RFS and LFS) flexibility was measured by the distance between the ground and the anterior suprailiac spine. A force plate (sampling rate, 1000 Hz) recorded countermovement and static jump characteristics. Explosive strength variables included flight time, jump height, peak force, instantaneous forces, and rates of force development. Data were analyzed using Bonferroni adjusted paired t-tests. VS had statistically increased flexibility (P) and large effect sizes (d) in both the RFS (P = 1.28 x 10(-7), d = 0.67) and LFS (P = 2.35 x 10(-7), d = 0.72). VS had statistically different results of favored (FL) (P = 4.67 x 10(-8), d= 0.78) and nonfavored (NFL) (P = 7.97 x 10(-10), d = 0.65) legs. VF resulted in statistical increases in flexibility and medium d on RFS (P = 6.98 x 10(-3), d = 0.25) and statistically increased flexibility on VF NFL flexibility (P = 0.002, d = 0.31). SF had no statistical difference between measures and small d. For explosive strength, there were no statistical differences in variables in the VS, SES, and VES for the pre- versus posttreatment tests. Simultaneous vibration and stretching may greatly increase flexibility while not altering explosive strength.

Nondestructive structural evaluation of wood floor systems with a vibration technique.

Treesearch

Xiping Wang; Robert J. Ross; Lawrence Andrew Soltis

2002-01-01

The objective of this study was to determine if transverse vibration methods could be used to effectively assess the structural integrity of wood floors as component systems. A total of 10 wood floor systems, including 3 laboratory-built floor sections and 7 in-place floors in historic buildings, were tested. A forced vibration method was applied to the floor systems...

Diesel engine torsional vibration control coupling with speed control system

NASA Astrophysics Data System (ADS)

Guo, Yibin; Li, Wanyou; Yu, Shuwen; Han, Xiao; Yuan, Yunbo; Wang, Zhipeng; Ma, Xiuzhen

2017-09-01

The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well.

Conception d'un système de mesure automatisé pour la caractérisation expérimentale des moteurs piézo-électriquesAn automated test system for piezoelectric motors

NASA Astrophysics Data System (ADS)

Ferreira, A.

1996-04-01

This paper describes an automated test system for piezoelectric motors allowing the experimental characterization of its electromechanical behaviour. In the first part, an experimental method is given for evaluation of losses generated in the different mechanisms of conversion: electric energy into ultrasonic vibrating energy and ultrasonic vibrating energy into mechanical energy of revolving motion. In the second part, the present method is experimentally validated on a travelling-wave-type rotary motor (Shinsei USR-60). The free stator vibration is analysed by a laser vibrometer which gives a picture both of amplitude and of phase vibration. This result allows one to obtain an identification of vibrations modes and an evaluation of ultrasonic vibrating energy and electromechanical efficiency. To characterize the working of the complete motor, the no-load working mode is first considered. The measurement of its maximal mechanical characteristics (maximal no-load rotating speed, maximal driving torque) with respect to axial load allows the choice of optimum axial load. For this optimum value, the load working mode is, finally, investigated for the evaluation of load characteristics and conversion losses.

Method for Vibration Response Simulation and Sensor Placement Optimization of a Machine Tool Spindle System with a Bearing Defect

PubMed Central

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

Effect of ultrasonic tip designs on intraradicular post removal.

PubMed

Aguiar, Anny Carine Barros; de Meireles, Daniely Amorim; Marques, André Augusto Franco; Sponchiado Júnior, Emílio Carlos; Garrido, Angela Delfina Bitencourt; Garcia, Lucas da Fonseca Roberti

2014-11-01

To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (P > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (P < 0.05). Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.

Low-Magnitude, High-Frequency Vibration Fails to Accelerate Ligament Healing but Stimulates Collagen Synthesis in the Achilles Tendon.

PubMed

Thompson, William R; Keller, Benjamin V; Davis, Matthew L; Dahners, Laurence E; Weinhold, Paul S

2015-05-01

Low-magnitude, high-frequency vibration accelerates fracture and wound healing and prevents disuse atrophy in musculoskeletal tissues. To investigate the role of low-magnitude, high-frequency vibration as a treatment to accelerate healing of an acute ligament injury and to examine gene expression in the intact Achilles tendon of the injured limb after low-magnitude, high-frequency vibration. Controlled laboratory study. Complete surgical transection of the medial collateral ligament (MCL) was performed in 32 Sprague-Dawley rats, divided into control and low-magnitude, high-frequency vibration groups. Low-magnitude, high-frequency vibration started on postoperative day 2, and rats received vibration for 30 minutes a day for 12 days. All rats were sacrificed 2 weeks after the operation, and their intact and injured MCLs were biomechanically tested or used for histological analysis. Intact Achilles tendons from the injured limb were evaluated for differences in gene expression. Mechanical testing revealed no differences in the ultimate tensile load or the structural stiffness between the control and vibration groups for either the injured or intact MCL. Vibration exposure increased gene expression of collagen 1 alpha (3-fold), interleukin 6 (7-fold), cyclooxygenase 2 (5-fold), and bone morphogenetic protein 12 (4-fold) in the intact Achilles tendon when compared with control tendons ( P < .05). While no differences were observed in the mechanical or histological properties of the fully transected MCL after low-magnitude, high-frequency vibration treatment, significant enhancements in gene expression were observed in the intact Achilles tendon. These included collagen, several inflammatory cytokines, and growth factors critical for tendons. As low-magnitude, high-frequency vibration had no negative effects on ligament healing, vibration therapy may be a useful tool to accelerate healing of other tissues (bone) in multitrauma injuries without inhibiting ligament healing. Additionally, the enhanced gene expression in response to low-magnitude, high-frequency vibration in the intact Achilles tendon suggests the need to further study its potential to accelerate tendon healing in partial injury or repair models.

Evaluation of a Concrete Continuous Beam Bridge Using Load Test

NASA Astrophysics Data System (ADS)

Zhang, Xiedong; Li, Hong; Li, Xiaofan; Xiang, Musheng; Shen, Chengwu

2007-03-01

Load test is an efficient way to evaluate highway bridges. This paper presents static and dynamic load tests on a prestressed concrete continuous beam bridge. We obtained the influence line and the vibration property of the bridge from FEM analysis. The stress, deformation and the vibration characteristics of the bridge were measured. We found that the measured data are consistent with those from the theoretical calculation, indicating good condition of the bridge.

Assembly, Integration, and Test Methods for Operationally Responsive Space Satellites

DTIC Science & Technology

2010-03-01

like assembly and vibration tests, to ensure there have been no failures induced by the activities. External thermal control blankets and radiator...configuration of the satellite post- vibration test and adds time to the process. • Thermal blanketing is not realistic with current technology or...patterns for thermal blankets and radiator tape. The computer aided drawing (CAD) solid model was used to generate patterns that were cut and applied real

Laser geodynamic satellite thermal/optical/ vibrational analyses and testing. Volume 2: Technical report, book 1. [retroreflector design

NASA Technical Reports Server (NTRS)

1974-01-01

The results of the LAGEOS thermal/optical/vibrational analysis and test program are reported. Through analyses and tests it is verified that the MSFC LAGEOS design provides a retroreflector thermal environment which maintains acceptable retroflector internal thermal gradients. The technical results of the study, organized by the major task areas are presented. The interrelationships of the major tasks are described and the major decisions are identified.

Evaluation of reaction time performance and subjective drowsiness during whole-body vibration exposure

NASA Astrophysics Data System (ADS)

Azizan, A.; Zali, Z.; Padil, H.

2018-05-01

Despite the automotive industry’s interest in how vibration affects the level of human comfort, there is little focus on the effect of vibration on drowsiness level. Thus, this study involves eighteen healthy male participants to study the effect of exposure to vibration on the drowsiness level. Prior to the experiment, the total transmitted vibration measured at interfaces between the seat pan and seat back to the human body for each participant was modified to become 0.2 ms-2 r.m.s and 0.4 ms-2 r.m.s. During the experiment, the participants were seated and exposed to 20-minutes of Gaussian random vibration with frequency band 1-15 Hz at two level of amplitude (low vibration amplitude and medium vibration amplitude) on separate days. The level of drowsiness was measured using a PVT test prior and after exposure to the vibration while participants rated their subjective drowsiness by using the Karolinska Sleepiness Scale (KSS). The significant increase in the number of lapse and reaction time because of the exposure to vibration in both conditions provide strong evidence of drowsiness. In this regard, the medium vibration amplitude shows a more prominent effect. All participants have shown a steady increase of drowsiness level in KSS. Meanwhile, there are no significant differences found between low vibration amplitude and medium vibration amplitude in the KSS. These findings suggest that human alertness level is greatly affected by the exposure to vibration and these effects are more pronounced at higher vibration amplitude. Both findings indicate that the presence of vibration promotes drowsiness, especially at higher vibration amplitude.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters bolted to it, atop the crawler-transporter, crawl to the intersection in the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. In the background are Launch Pads 39A (right) and 39B (left). The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters bolted to it, atop the crawler-transporter, crawl to the intersection in the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. In the background are Launch Pads 39A (right) and 39B (left). The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. In the distance, at left, is Launch Pad 39A. The water on the right of the crawlerway is the Banana River. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - The crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB) in support of engineering analysis vibration tests on the crawler and MLP. In the distance, at left, is Launch Pad 39A. The water on the right of the crawlerway is the Banana River. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Seen across the water of the Launch Complex 39 turn basin, a crawler-transporter, carrying Mobile Launcher Platform (MLP) number 3 with a set of twin solid rocket boosters bolted atop, crawls out of the 525-foot-tall Vehicle Assembly Building during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Seen across the water of the Launch Complex 39 turn basin, a crawler-transporter, carrying Mobile Launcher Platform (MLP) number 3 with a set of twin solid rocket boosters bolted atop, crawls out of the 525-foot-tall Vehicle Assembly Building during the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician inspects the shoes on one of eight tracks of a crawler-transporter (CT). The CT is moving Mobile Launcher Platform (MLP) number 3 with a set of twin solid rocket boosters bolted on top to the intersection in the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - A Kennedy Space Center technician inspects the shoes on one of eight tracks of a crawler-transporter (CT). The CT is moving Mobile Launcher Platform (MLP) number 3 with a set of twin solid rocket boosters bolted on top to the intersection in the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The view reveals the river gravel surface that is 4 inches thick on the straightaway sections and 8 inches thick on curves. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-21

KENNEDY SPACE CENTER, FLA. - Mobile Launcher Platform (MLP) number 3 and a set of twin solid rocket boosters, atop the crawler-transporter, inch along the crawlerway in support of the second engineering analysis vibration test on the crawler and MLP. The view reveals the river gravel surface that is 4 inches thick on the straightaway sections and 8 inches thick on curves. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB, travels toward Launch Pad 39A and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

KENNEDY SPACE CENTER, FLA. - Viewed across the turn basin in the Launch Complex 39 Area, the crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB). The journey is in support of engineering analysis vibration tests on the crawler and MLP. The water on the right of the crawlerway is the Banana River. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

NASA Image and Video Library

2003-11-17

KENNEDY SPACE CENTER, FLA. - Viewed across the turn basin in the Launch Complex 39 Area, the crawler transporter slowly moves the Mobile Launcher Platform (MLP), carrying a set of twin solid rocket boosters, away from the Vehicle Assembly Building (VAB). The journey is in support of engineering analysis vibration tests on the crawler and MLP. The water on the right of the crawlerway is the Banana River. The crawler is moving at various speeds up to 1 mph in an effort to achieve vibration data gathering goals as it leaves the VAB and then returns. The boosters are braced at the top for stability. The primary purpose of these rollout tests is to gather data to develop future maintenance requirements on the transport equipment and the flight hardware. Various parts of the MLP and crawler transporter have been instrumented with vibration data collection equipment.

Satellite Vibration Testing: Angle optimisation method to Reduce Overtesting

NASA Astrophysics Data System (ADS)

Knight, Charly; Remedia, Marcello; Aglietti, Guglielmo S.; Richardson, Guy

2018-06-01

Spacecraft overtesting is a long running problem, and the main focus of most attempts to reduce it has been to adjust the base vibration input (i.e. notching). Instead this paper examines testing alternatives for secondary structures (equipment) coupled to the main structure (satellite) when they are tested separately. Even if the vibration source is applied along one of the orthogonal axes at the base of the coupled system (satellite plus equipment), the dynamics of the system and potentially the interface configuration mean the vibration at the interface may not occur all along one axis much less the corresponding orthogonal axis of the base excitation. This paper proposes an alternative testing methodology in which the testing of a piece of equipment occurs at an offset angle. This Angle Optimisation method may have multiple tests but each with an altered input direction allowing for the best match between all specified equipment system responses with coupled system tests. An optimisation process that compares the calculated equipment RMS values for a range of inputs with the maximum coupled system RMS values, and is used to find the optimal testing configuration for the given parameters. A case study was performed to find the best testing angles to match the acceleration responses of the centre of mass and sum of interface forces for all three axes, as well as the von Mises stress for an element by a fastening point. The angle optimisation method resulted in RMS values and PSD responses that were much closer to the coupled system when compared with traditional testing. The optimum testing configuration resulted in an overall average error significantly smaller than the traditional method. Crucially, this case study shows that the optimum test campaign could be a single equipment level test opposed to the traditional three orthogonal direction tests.

Ground vibration tests of a high fidelity truss for verification of on orbit damage location techniques

NASA Technical Reports Server (NTRS)

Kashangaki, Thomas A. L.

1992-01-01

This paper describes a series of modal tests that were performed on a cantilevered truss structure. The goal of the tests was to assemble a large database of high quality modal test data for use in verification of proposed methods for on orbit model verification and damage detection in flexible truss structures. A description of the hardware is provided along with details of the experimental setup and procedures for 16 damage cases. Results from selected cases are presented and discussed. Differences between ground vibration testing and on orbit modal testing are also described.

Correlation of AH-1G airframe test data with a NASTRAN mathematical model

NASA Technical Reports Server (NTRS)

Cronkhite, J. D.; Berry, V. L.

1976-01-01

Test data was provided for evaluating a mathematical vibration model of the Bell AH-1G helicopter airframe. The math model was developed and analyzed using the NASTRAN structural analysis computer program. Data from static and dynamic tests were used for comparison with the math model. Static tests of the fuselage and tailboom were conducted to verify the stiffness representation of the NASTRAN model. Dynamic test data were obtained from shake tests of the airframe and were used to evaluate the NASTRAN model for representing the low frequency (below 30 Hz) vibration response of the airframe.

The influence of vibration on seated human drowsiness

PubMed Central

AZIZAN, Amzar; FARD, Mohammad; AZARI, Michael F.; BENEDIKTSDÓTTIR, Bryndís; ARNARDÓTTIR, Erna Sif; JAZAR, Reza; MAEDA, Setsuo

2016-01-01

Although much is known about human body vibration discomfort, there is little research data on the effects of vibration on vehicle occupant drowsiness. A laboratory experimental setup has been developed. Vibration was applied to the volunteers sitting on the vehicle seat mounted on the vibration platform. Seated volunteers were exposed to a Gaussian random vibration, with 1–15 Hz frequency bandwidth at 0.2 ms−2 r.m.s., for 20-minutes. Two drowsiness measurement methods were used, Psychomotor Vigilance Test (PVT) and Karolinska Sleepiness Scale (KSS). Significant changes in PVT (p<0.05) and KSS (p<0.05) were detected in all eighteen volunteers. Furthermore, a moderate correlation (r>0.4) was observed between objective measurement (PVT) and subjective measurement (KSS). The results suggest that exposure to vibration even for 20-minutes can cause significant drowsiness impairing psychomotor performance. This finding has important implications for road safety. PMID:26829971

Comparative studies of perceived vibration strength for commercial mobile phones.

PubMed

Lee, Heow Pueh; Lim, Siak Piang

2014-05-01

A mobile phone, also known as cell phone or hand phone, is among the most popular electrical devices used by people all over the world. The present study examines the vibration perception of mobile phones by co-relating the relevant design parameters such as excitation frequency, and size and mass of mobile phones to the vibration perception survey by volunteers. Five popular commercially available mobile phone models were tested. The main findings for the perception surveys were that higher vibration frequency and amplitude of the peak acceleration would result in stronger vibration perception of the mobile phones. A larger contact surface area with the palms and figures, higher peak acceleration and the associated larger peak inertia force may be the main factors for the relatively higher vibration perception. The future design for the vibration alert of the mobile phones is likely to follow this trend. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Acute effects of whole-body vibration on the motor function of patients with stroke: a randomized clinical trial.

PubMed

Silva, Adriana Teresa; Dias, Miqueline Pivoto Faria; Calixto, Ruanito; Carone, Antonio Luis; Martinez, Beatriz Bertolaccini; Silva, Andreia Maria; Honorato, Donizeti Cesar

2014-04-01

The aim of this study was to investigate the acute effects of whole-body vibration on the motor function of patients with stroke. The present investigation was a randomized clinical trial studying 43 individuals with hemiparesis after stroke, with 33 subjects allocated to the intervention group and 10 subjects allocated to the control group. The intervention group was subjected to one session of vibration therapy (frequency of 50 Hz and amplitude of 2 mm) comprising four 1-min series with 1-min rest intervals between series in three body positions: bipedal stances with the knees flexed to 30 degrees and 90 degrees and a unipedal stance on the paretic limb. The analytical tests were as follows: simultaneous electromyography of the affected and unaffected tibialis anterior and rectus femoris muscles bilaterally in voluntary isometric contraction; the Six-Minute Walk Test; the Stair-Climb Test; and the Timed Get-Up-and-Go Test. The data were analyzed by independent and paired t tests and by analysis of covariance. There was no evidence of effects on the group and time interaction relative to variables affected side rectus femoris, unaffected side rectus femoris, affected side tibialis anterior, unaffected side tibialis anterior, and the Stair-Climb Test (P > 0.05). There was evidence of effects on the group interaction relative to variables Six-Minute Walk Test and Timed Get-Up-and-Go Test (P < 0.05). Whole-body vibration contributed little to improve the functional levels of stroke patients.

Integrated Vehicle Ground Vibration Testing in Support of Launch Vehicle Loads and Controls Analysis

NASA Technical Reports Server (NTRS)

Askins, Bruce R.; Davis, Susan R.; Salyer, Blaine H.; Tuma, Margaret L.

2008-01-01

All structural systems possess a basic set of physical characteristics unique to that system. These unique physical characteristics include items such as mass distribution and damping. When specified, they allow engineers to understand and predict how a structural system behaves under given loading conditions and different methods of control. These physical properties of launch vehicles may be predicted by analysis or measured by certain types of tests. Generally, these properties are predicted by analysis during the design phase of a launch vehicle and then verified by testing before the vehicle becomes operational. A ground vibration test (GVT) is intended to measure by test the fundamental dynamic characteristics of launch vehicles during various phases of flight. During the series of tests, properties such as natural frequencies, mode shapes, and transfer functions are measured directly. These data will then be used to calibrate loads and control systems analysis models for verifying analyses of the launch vehicle. NASA manned launch vehicles have undergone ground vibration testing leading to the development of successful launch vehicles. A GVT was not performed on the inaugural launch of the unmanned Delta III which was lost during launch. Subsequent analyses indicated had a GVT been performed, it would have identified instability issues avoiding loss of the vehicle. This discussion will address GVT planning, set-up, execution and analyses, for the Saturn and Shuttle programs, and will also focus on the current and on-going planning for the Ares I and V Integrated Vehicle Ground Vibration Test (IVGVT).

Microgravity Vibration Control and Civil Applications

NASA Technical Reports Server (NTRS)

Whorton, Mark Stephen; Alhorn, Dean Carl

1998-01-01

Controlling vibration of structures is essential for both space structures as well as terrestrial structures. Due to the ambient acceleration levels anticipated for the International Space Station, active vibration isolation is required to provide a quiescent acceleration environment for many science experiments. An overview is given of systems developed and flight tested in orbit for microgravity vibration isolation. Technology developed for vibration control of flexible space structures may also be applied to control of terrestrial structures such as buildings and bridges subject to wind loading or earthquake excitation. Recent developments in modern robust control for flexible space structures are shown to provide good structural vibration control while maintaining robustness to model uncertainties. Results of a mixed H-2/H-infinity control design are provided for a benchmark problem in structural control for earthquake resistant buildings.

Prevalence of vibration-induced white finger in fluorspar mines in Weardale.

PubMed Central

Chatterjee, D S; Petrie, A; Taylor, W

1978-01-01

A combined epidemiological and clinical study of vibration-induced white finger (VWF) was carried out involving 115 men in four fluorspar mines. The overall prevalence of VWF was found to be 50% among 42 vibration-exposed subjects, while that of constitutional white finger (CWF) was 5-6% in all men studied. The VWF latent interval was 1-19 years with a mean of 5-6 years. An association was observed between the exposure time and VWF stages which included 18 men in Stage 0, three in the intermediate Stage of 0T/0N, five in Stage 2 and 16 in Stage 3; no men were seen at Stage 1. Among those with VWF in Stage 3, the index, middle and ring fingers were affected in both hands and the little fingers and thumbs were last to be involved. Clinically, on general examination, apart from vibration-induced white finger, the men in the 'vibration' group were not as healthy as those in the 'control' group. The circumference of the index fingers was not significantly different for the different groups. Neurological tests showed that the ridge test and, to a lesser extent, the two-point discrimination and the light touch tests, could be regarded as useful for the diagnosis of VWF. PMID:698134

Air injection test on a Kaplan turbine: prototype - model comparison

NASA Astrophysics Data System (ADS)

Angulo, M.; Rivetti, A.; Díaz, L.; Liscia, S.

2016-11-01

Air injection is a very well-known resource to reduce pressure pulsation magnitude in turbines, especially on Francis type. In the case of large Kaplan designs, even when not so usual, it could be a solution to mitigate vibrations arising when tip vortex cavitation phenomenon becomes erosive and induces structural vibrations. In order to study this alternative, aeration tests were performed on a Kaplan turbine at model and prototype scales. The research was focused on efficiency of different air flow rates injected in reducing vibrations, especially at the draft tube and the discharge ring and also in the efficiency drop magnitude. It was found that results on both scales presents the same trend in particular for vibration levels at the discharge ring. The efficiency drop was overestimated on model tests while on prototype were less than 0.2 % for all power output. On prototype, air has a beneficial effect in reducing pressure fluctuations up to 0.2 ‰ of air flow rate. On model high speed image computing helped to quantify the volume of tip vortex cavitation that is strongly correlated with the vibration level. The hydrophone measurements did not capture the cavitation intensity when air is injected, however on prototype, it was detected by a sonometer installed at the draft tube access gallery.

Hand-arm vibration syndrome: clinical characteristics, conventional electrophysiology and quantitative sensory testing.

PubMed

Rolke, Roman; Rolke, Silke; Vogt, Thomas; Birklein, Frank; Geber, Christian; Treede, Rolf-Detlef; Letzel, Stephan; Voelter-Mahlknecht, Susanne

2013-08-01

Workers exposed to vibrating tools may develop hand-arm vibration syndrome (HAVS). We assessed the somatosensory phenotype using quantitative sensory testing (QST) in comparison to electrophysiology to characterize (1) the most sensitive QST parameter for detecting sensory loss, (2) the correlation of QST and electrophysiology, and (3) the frequency of a carpal tunnel syndrome (CTS) in HAVS. QST, cold provocation tests, fine motor skills, and median nerve neurography were used. QST included thermal and mechanical detection and pain thresholds. Thirty-two patients were examined (54 ± 11 years, 91% men) at the more affected hand compared to 16 matched controls. Vibration detection threshold was the most sensitive parameter to detect sensory loss that was more pronounced in the sensitivity range of Pacinian (150 Hz, x12) than Meissner's corpuscles (20 Hz, x3). QST (84% abnormal) was more sensitive to detect neural dysfunction than conventional electrophysiology (37% abnormal). Motor (34%) and sensory neurography (25%) were abnormal in HAVS. CTS frequency was not increased (9.4%). Findings are consistent with a mechanically-induced, distally pronounced motor and sensory neuropathy independent of CTS. HAVS involves a neuropathy predominantly affecting large fibers with a sensory damage related to resonance frequencies of vibrating tools. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

[The health condition of forest workers exposed to noise and vibration produced by chain saws].

PubMed

Malinowska-Borowska, Jolanta; Socholik, Violetta; Harazin, Barbara

2012-01-01

Lumberjacks' working conditions are difficult due to the presence of numerous occupational hazards. Physical factors that pose a health risk are noise and vibration produced by chain saws. Excessive exposure of lumberjacks to noise and vibration can lead to the development of hand-arm vibration syndrome and hearing loss. The aim of the work was to analyze the health condition of forestry workers exposed to occupational physical hazards. A preliminary, questionnaire-based assessment of health status was conducted in 22 chain saw operators. In a group of 15 forestry workers audiometry, vibrotactile perception thresholds and cold provocation test were performed. X-ray diagnostic imaging of upper limbs was also done. At the same time noise and vibration produced by chain saws used in forestry was measured. Vascular or neurological disorders were found in nearly half of tested workers with seniority from 2 to 20 years; 40% of the surveyed was diagnosed with hearing impairment. An 8-hour energy equivalent vibration level measured on chain saws was 4.6 m/s2. An 8-hour equivalent sound pressure level was 99.1 dB(A). The threshold limit values for noise and vibration are exceeded at woodcutters' posts. There are changes in lumberjacks' health resulting from exposure to harmful physical agents. Preventive actions are urgently needed to be addressed, especially to people employed in single-handed forestry companies.

Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades

NASA Technical Reports Server (NTRS)

Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

2012-01-01

Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

Effect of temperature- and frequency-dependent dynamic properties of rail pads on high-speed vehicle-track coupled vibrations

NASA Astrophysics Data System (ADS)

Wei, Kai; Wang, Feng; Wang, Ping; Liu, Zi-xuan; Zhang, Pan

2017-03-01

The soft under baseplate pad of WJ-8 rail fastener frequently used in China's high-speed railways was taken as the study subject, and a laboratory test was performed to measure its temperature and frequency-dependent dynamic performance at 0.3 Hz and at -60°C to 20°C with intervals of 2.5°C. Its higher frequency-dependent results at different temperatures were then further predicted based on the time-temperature superposition (TTS) and Williams-Landel-Ferry (WLF) formula. The fractional derivative Kelvin-Voigt (FDKV) model was used to represent the temperature- and frequency-dependent dynamic properties of the tested rail pad. By means of the FDKV model for rail pads and vehicle-track coupled dynamic theory, high-speed vehicle-track coupled vibrations due to temperature- and frequency-dependent dynamic properties of rail pads was investigated. Finally, further combining with the measured frequency-dependent dynamic performance of vehicle's rubber primary suspension, the high-speed vehicle-track coupled vibration responses were discussed. It is found that the storage stiffness and loss factor of the tested rail pad are sensitive to low temperatures or high frequencies. The proposed FDKV model for the frequency-dependent storage stiffness and loss factors of the tested rail pad can basically meet the fitting precision, especially at ordinary temperatures. The numerical simulation results indicate that the vertical vibration levels of high-speed vehicle-track coupled systems calculated with the FDKV model for rail pads in time domain are higher than those calculated with the ordinary Kelvin-Voigt (KV) model for rail pads. Additionally, the temperature- and frequency-dependent dynamic properties of the tested rail pads would alter the vertical vibration acceleration levels (VALs) of the car body and bogie in 1/3 octave frequencies above 31.5 Hz, especially enlarge the vertical VALs of the wheel set and rail in 1/3 octave frequencies of 31.5-100 Hz and above 315 Hz, which are the dominant frequencies of ground vibration acceleration and rolling noise (or bridge noise) caused by high-speed railways respectively. Since the fractional derivative value of the adopted rubber primary suspension, unlike the tested rail pad, is very close to 1, its frequency-dependent dynamic performance has little effect on high-speed vehicle-track coupled vibration responses.

APPARATUS FOR NON-DESTRUCTIVE INSPECTION OF CANTILEVERED MEMBERS

DOEpatents

Taylor, E.R.; Mahoney, C.H.; Lay, C.R.

1961-10-24

An apparatus for non-destructive inspection of cantilevered members, such as compressor blades, is described. The member under inspection is vibrated with a regulated source of air under pressure. The amplitude of vibration of the member is maintained at its natural frequency. The frequency of vibration of the member is measured. An indication of an excessive decay or erratic shifting in the measured frequency above an allowable hysteretic decay is provided as an indication of a fault in the member. The member is vibrated for a selected test period. (AEC)

Effect of vertical active vibration isolation on tracking performance and on ride qualities

NASA Technical Reports Server (NTRS)

Dimasi, F. P.; Allen, R. E.; Calcaterra, P. C.

1972-01-01

An investigation to determine the effect on pilot performance and comfort of an active vibration isolation system for a commercial transport pilot seat is reported. The test setup consisted of: a hydraulic shaker which produced random vertical vibration inputs; the active vibration isolation system; the pilot seat; the pilot control wheel and column; the side-arm controller; and a two-axis compensatory tracking task. The effects of various degrees of pilot isolation on short-term (two-minute) tracking performance and comfort were determined.

Vibration mode and vibration shape under excitation of a three phase model transformer core

NASA Astrophysics Data System (ADS)

Okabe, Seiji; Ishigaki, Yusuke; Omura, Takeshi

2018-04-01

Structural vibration characteristics and vibration shapes under three-phase excitation of a archetype transformer core were investigated to consider their influences on transformer noise. Acoustic noise and vibration behavior were measured in a three-limb model transformer core. Experimental modal analysis by impact test was performed. The vibration shapes were measured by a laser scanning vibrometer at different exciting frequencies. Vibration amplitude of the core in out-of-plane direction were relatively larger than those in other two in-plane directions. It was consistent with the result that the frequency response function of the core in out-of-plane direction was larger by about 20 dB or more than those in in-plane directions. There were many vibration modes having bending deformation of limbs in out-of-plane direction. The vibration shapes of the core when excited at 50 Hz and 60 Hz were almost the same because the fundamental frequencies of the vibration were not close to the resonance frequencies. When excitation frequency was 69 Hz which was half of one of the resonance frequencies, the vibration shape changed to the one similar to the resonance vibration mode. Existence of many vibration modes in out-of-plane direction of the core was presumed to be a reason why frequency characteristics of magnetostriction and transformer noise do not coincide.

Comparative evaluation of Space Transportation System (STS)-3 flight and acoustic test random vibration response of the OSS-1 payload

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.

Development of flexural vibration inspection techniques to rapidly assess the structural health of rural bridge systems

Treesearch

Brian K. Brashaw; Robert Vatalaro; Xiping Wang; Kevin Sarvela; James P. Wacker

2008-01-01

Approximately 4,000 vehicle bridges in the State of Minnesota contain structural timber members. Recent research at the University of Minnesota Duluth Natural Resources Research Institute (UMD NRRI) has been conducted on vibration testing of timber bridges as a means of developing rapid in-place testing techniques for assessing the structural health of bridges. The...

Shock and vibration tests of a SNAP-8 NaK pump

NASA Technical Reports Server (NTRS)

Stromquist, A. J.; Nelson, R. B.; Hibben, L.

1971-01-01

The pump used for reactor cooling in the SNAP 8 space power system was subjected to the expected vehicle launch vibration, and shock loading in accordance with the SNAP 8 environmental specification. Subsequent disassembly revealed damage to the thrust bearing pins, which should be redesigned and strengthened. The unit was operational, however, when run in a test loop after reassembly.

Proceedings of Damping 1993, volume 3

NASA Astrophysics Data System (ADS)

Portis, Bonnie L.

1993-06-01

Presented are individual papers of Damping '93, held 24-26 February 1993 in San Francisco. The subjects included: passive damping concepts; passive damping analysis and design techniques; optimization; damped control/structure interaction; viscoelastic material testing and characterization; highly damped materials; vibration suppression techniques; damping identification and dynamic testing; applications to aircraft; space structures; Marine structures; and commercial products; defense applications; and payoffs of vibration suppression.

Proceedings of Damping 1993, volume 1

NASA Astrophysics Data System (ADS)

Portis, Bonnie L.

1993-06-01

Presented are individual papers of Damping '93 held 24-26 February, 1993, in San Francisco. The subjects included: passive damping concepts; passive damping analysis and design techniques; optimization; damped control/structure interaction; viscoelastic material testing and characterization; highly damped materials; vibration suppression techniques; damping identification and dynamic testing; application to aircraft; space structures; marine structures; commercial products; defense applications; and payoffs of vibration suppression.

Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge.

PubMed

Guan, W; Meng, X F; Dong, X M

2014-12-01

Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

Effects on Diagnostic Parameters After Removing Additional Synchronous Gear Meshes

NASA Technical Reports Server (NTRS)

Decker, Harry J.

2003-01-01

Gear cracks are typically difficult to diagnose with sufficient time before catastrophic damage occurs. Significant damage must be present before algorithms appear to be able to detect the damage. Frequently there are multiple gear meshes on a single shaft. Since they are all synchronous with the shaft frequency, the commonly used synchronous averaging technique is ineffective in removing other gear mesh effects. Carefully applying a filter to these extraneous gear mesh frequencies can reduce the overall vibration signal and increase the accuracy of commonly used vibration metrics. The vibration signals from three seeded fault tests were analyzed using this filtering procedure. Both the filtered and unfiltered vibration signals were then analyzed using commonly used fault detection metrics and compared. The tests were conducted on aerospace quality spur gears in a test rig. The tests were conducted at speeds ranging from 2500 to 5000 revolutions per minute and torques from 184 to 228 percent of design load. The inability to detect these cracks with high confidence results from the high loading which is causing fast fracture as opposed to stable crack growth. The results indicate that these techniques do not currently produce an indication of damage that significantly exceeds experimental scatter.

Deck and Cable Dynamic Testing of a Single-span Bridge Using Radar Interferometry and Videometry Measurements

NASA Astrophysics Data System (ADS)

Piniotis, George; Gikas, Vassilis; Mpimis, Thanassis; Perakis, Harris

2016-03-01

This paper presents the dynamic testing of a roadway, single-span, cable-stayed bridge for a sequence of static load and ambient vibration monitoring scenarios. Deck movements were captured along both sideways of the bridge using a Digital Image Correlation (DIC) and a Ground-based Microwave Interfererometer (GBMI) system. Cable vibrations were measured at a single point location on each of the six cables using the GBMI technique. Dynamic testing involves three types of analyses; firstly, vibration analysis and modal parameter estimation (i. e., natural frequencies and modal shapes) of the deck using the combined DIC and GBMI measurements. Secondly, dynamic testing of the cables is performed through vibration analysis and experimental computation of their tension forces. Thirdly, the mechanism of cable-deck dynamic interaction is studied through their Power Spectra Density (PSD) and the Short Time Fourier Transform (STFT) analyses. Thereby, the global (deck and cable) and local (either deck or cable) bridge modes are identified, serving a concrete benchmark of the current state of the bridge for studying the evolution of its structural performance in the future. The level of synergy and complementarity between the GBMI and DIC techniques for bridge monitoring is also examined and assessed.

Combined isometric and vibration training does not enhance strength beyond that of isometric training alone.

PubMed

Fisher, J; Van-Dongen, M; Sutherland, R

2014-10-08

Research considering combined vibration and strength training is extensive yet results are equivocal. However, to date there appears no research which has considered the combination of both direct vibration and whole---body vibration when used in an isometric deadlift position. The aims of this study were to compare groups performing isometric training with and without direct and whole---body vibration. Twenty four participants (19---24 years) were randomly divided into: isometric training with vibration (ST+VT: n=8), isometric training without vibration (ST: n=8), and control (CON: n=8). Within the training groups participants trained twice per week, for 6 weeks, performing 6---sets of maximal isometric deadlift contractions, increasing in duration from 30 seconds to 40 seconds (weeks 1---6). Hip and knee angle was maintained at 60° and 110°, respectively for both testing and training. Training sessions for ST+VT were identical to ST with the addition of a direct vibratory stimulus through hand---held straps and whole---body vibration via standing on vibration a platform. The amplitude remained constant (2mm) throughout the intervention whilst the frequency increased from 35Hz to 50Hz. Pre--- and post---test isometric strength was measured using an isometric deadlift dynamometer. Results revealed significant increases in isometric strength for both ST+VT (p < 0.001, 23.8%) and ST (p < 0.001, 32.5%) compared to CON, with no significant differences between ST+VT and ST training groups. The present study provides evidence to suggest that there are no greater gains to be incurred by the addition of a vibratory stimulus to traditional strength training.

Combined isometric and vibration training does not enhance strength beyond that of isometric training alone.

PubMed

Fisher, J; Van-Dongen, M; Sutherland, R

2015-09-01

Research considering combined vibration and strength training is extensive yet results are equivocal. However, to date there appears no research which has considered the combination of both direct vibration and whole-body vibration when used in an isometric deadlift position. The aim of this study was to compare groups performing isometric training with and without direct and whole-body vibration. Twenty four participants (19-24 years) were randomly divided into: isometric training with vibration (ST+VT: N.=8), isometric training without vibration (ST: N.=8), and control (CON: N.=8). Within the training groups participants trained twice per week, for 6 weeks, performing 6-sets of maximal isometric deadlift contractions, increasing in duration from 30 seconds to 40 seconds (weeks 1-6). Hip and knee angle was maintained at 60° and 110°, respectively for both testing and training. Training sessions for ST+VT were identical to ST with the addition of a direct vibratory stimulus through hand-held straps and whole-body vibration via standing on vibration a platform. The amplitude remained constant (2 mm) throughout the intervention whilst the frequency increased from 35Hz to 50Hz. Pre- and post-test isometric strength was measured using an isometric deadlift dynamometer. Results revealed significant increases in isometric strength for both ST+VT (P<0.001, 23.8%) and ST (P<0.001, 32.5%) compared to CON, with no significant differences between ST+VT and ST training groups. The present study provides evidence to suggest that there are no greater gains to be incurred by the addition of a vibratory stimulus to traditional strength training.

Vibrations Generated by Several Nickel-titanium Endodontic File Systems during Canal Shaping in an Ex Vivo Model.

PubMed

Choi, Dong-Min; Kim, Jin-Woo; Park, Se-Hee; Cho, Kyung-Mo; Kwak, Sang Won; Kim, Hyeon-Cheol

2017-07-01

This study aimed to compare the vibration generated by several nickel-titanium (NiTi) file systems and transmitted to teeth under 2 different motions (continuous rotation motion and reciprocating motion). Sixty J-shaped resin blocks (Endo Training Bloc-J; Dentsply Maillefer, Ballaigues, Switzerland) were trimmed to a root-shaped form and divided into 2 groups according to the types of electric motors: WaveOne motor (WOM, Dentsply Maillefer) and X-Smart Plus motor (XSM, Dentsply Maillefer). Each group was further subdivided into 3 subgroups (n = 10 each) according to the designated file systems: ProTaper Next (PTN, Dentsply Maillefer), ProTaper Universal (PTU, Dentsply Maillefer), and WaveOne (WOP, Dentsply Maillefer) systems. Vibration was measured during the pecking motion using an accelerometer attached to a predetermined consistent position. The average vibration values were subjected to 2-way analysis of variance as well as the t test and Duncan test for post hoc comparison at the 95% confidence interval. Both motor types and instrument types produced significantly different ranges of average vibrations. Regardless of the instrument types, the WOM group generated greater vibration than the XSM group (P < .05). Although PTN and PTU did not show significant differences, the WOP group showed significantly greater vibration than the other groups regardless of motor types (P < .05). Under the limitations of this study design, the reciprocating NiTi file system may generate greater vibration than the continuous rotation NiTi file systems. The motor type also has a significant effect to amplify the vibrations. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effect of whole-body vibration exercise on mobility, balance ability and general health status in frail elderly patients: a pilot randomized controlled trial.

PubMed

Zhang, Li; Weng, Changshui; Liu, Miao; Wang, Qiuhua; Liu, Liming; He, Yao

2014-01-01

To study the effects of whole-body vibration exercises on the mobility function, balance and general health status, and its feasibility as an intervention in frail elderly patients. Pilot randomized controlled trial. Forty-four frail older persons (85.27 ± 3.63 years) meeting the Fried Frailty Criteria. All eligible subjects were randomly assigned to the experimental group, who received a whole-body vibration exercise alone (vibration amplitude: 1-3 mm; frequency: 6-26 Hz; 4-5 bouts × 60 seconds; 3-5 times weekly), or a control group, who received usual care and exercises for eight weeks. The Timed Up and Go Test, 30-second chair stand test, lower extremities muscle strength, balance function, balance confidence and General Health Status were assessed at the beginning of the study, after four weeks and eight weeks of the intervention. Whole-body vibration exercise reduced the time of the Timed Up and Go Test (40.47 ± 15.94 s to 21.34 ± 4.42 s), improved the bilateral knees extensor strength (6.96 ± 1.70 kg to 11.26 ± 2.08 kg), the posture stability (surface area ellipse: 404.58 ± 177.05 to 255.95 ± 107.28) and General Health Status (Short-form Health Survey score: 24.51 ± 10.69 and 49.63 ± 9.85 to 45.03 ± 11.15 and 65.23 ± 9.39, respectively). The repeated-measures ANOVA showed that there were significant differences in the Timed Up and Go Test, 30-second chair stand test, bilateral knees extensor strength, activities-specific balance confidence score and general health status between the two groups (P < 0.05). No side-effects were observed during the training. Whole-body vibration exercise is a safe and effective method that can improve the mobility, knee extensor strength, balance and the general health status in the frail elderly.

The Coupling of Flexural Propeller Vibrations with the Torsional Crankshaft Vibrations

NASA Technical Reports Server (NTRS)

Meyer, J.

1943-01-01

The exact mathematical treatment of the problem is possible by replacing the propeller blade by a homogeneous prismatic rod. Conclusions can them be drawn as to the behavior of an actual propeller, since tests on propeller blades have indicated a qualitative agreement with the homogeneous rod. The natural frequencies are determined and the stressing of the systems under the various vibration modes are discussed.

Advanced Stirling Convertor Dynamic Test Approach and Results

NASA Technical Reports Server (NTRS)

Meer, David W.; Hill, Dennis; Ursic, Joseph

2009-01-01

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Converters (ASC) at NASA John H. Glenn Research Center undergo a vibration test sequence intended to simulate the vibration history of an ASC used in an ASRG for a space mission. This sequence includes testing at Workmanship and Flight Acceptance levels interspersed with periods of extended operation to simulate pre and post fueling. The final step in the test sequence utilizes additional testing at Flight Acceptance levels to simulate launch. To better replicate the acceleration profile seen by an ASC incorporated into an ASRG, the input spectra used in testing the convertors was modified based on dynamic testing of the ASRG Engineering Unit ( ASRG-EU) at Lockheed Martin. This paper presents the vibration test plan for current and future ASC units, including the modified input spectra, and the results of recent tests using these spectra. The test results include data from several accelerometers mounted on the convertors as well as the piston position and output power variables.

Quiet Spike(TradeMark) Build-up Ground Vibration Testing Approach

NASA Technical Reports Server (NTRS)

Spivey, Natalie D.; Herrera, Claudia Y.; Truax, Roger; Pak, Chan-gi; Freund, Donald

2007-01-01

Flight tests of Gulfstream Aerospace Corporation s Quiet Spike(TradeMark) hardware were recently completed on the NASA Dryden Flight Research Center F-15B airplane. NASA Dryden uses a modified F-15B airplane as a testbed aircraft to cost-effectively fly flight research experiments that are typically mounted underneath the F-15B airplane, along the fuselage centerline. For the Quiet Spike(TradeMark) experiment, however, instead of a centerline mounting, a relatively long forward-pointing boom was attached to the radar bulkhead of the F-15B airplane. The Quiet Spike(TradeMark) experiment is a stepping-stone to airframe structural morphing technologies designed to mitigate the sonic-boom strength of business jets over land. The Quiet Spike(TradeMark) boom is a concept in which an aircraft s noseboom would be extended prior to supersonic acceleration. This morphing effectively lengthens the aircraft, thus reducing the peak sonic-boom amplitude, but is also expected to partition the otherwise strong bow shock into a series of reduced-strength, noncoalescing shocklets. Prior to flying the Quiet Spike(TradeMark) experiment on the F-15B airplane several ground vibration tests were required to understand the Quiet Spike(TradeMark) modal characteristics and coupling effects with the F-15B airplane. However, due to the flight hardware availability and compressed schedule requirements, a "traditional" ground vibration test of the mated F-15B Quiet Spike(TradeMark) ready-for- flight configuration did not leave sufficient time available for the finite element model update and flutter analyses before flight testing. Therefore, a "nontraditional" ground vibration testing approach was taken. This paper provides an overview of each phase of the "nontraditional" ground vibration testing completed for the Quiet Spike(TradeMark) project which includes the test setup details, instrumentation layout, and modal results obtained in support of the structural dynamic modeling and flutter analyses.

Metal foil method for noncontact measurement of lateral vibrations of a nonmetallic cylinder by a solenoid

NASA Astrophysics Data System (ADS)

Han, Soon Woo; Bang, Young Bong; Kim, Yoon Young

2006-10-01

This investigation shows that if a solenoid encircles a metal foil loop wound around a nonmetallic cylinder vibrating laterally, an electromotive force is induced in the solenoid. The induction is possible only when the foil loop is complete and an antisymmetric magnetic field is applied to the foil. In this work, stationary permanent magnets were used. Because the solenoid is the sensing element, no physical contact between the element and a test specimen is required. The effects of the metal foil thickness and width on the measurement sensitivity were studied and vibration modal testing of an acryl cylinder was performed.

An Accelerated Method for Testing Soldering Tendency of Core Pins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Qingyou; Xu, Hanbing; Ried, Paul

2010-01-01

An accelerated method for testing die soldering has been developed. High intensity ultrasonic vibrations has been used to simulate the die casting conditions such as high pressure and high impingement speed of molten metal on the pin. Soldering tendency of steels and coated pins has been examined. The results indicate that in the low carbon steel/Al system, the onset of soldering is 60 times faster with ultrasonic vibration than that without ultrasonic vibration. In the H13/A380 system, the onset of soldering reaction is accelerated to 30-60 times. Coating significantly reduces the soldering tendency of the core pins.

Gel performance in rheology and profile control under low-frequency vibration: coupling application of physical and chemical EOR techniques.

PubMed

Zheng, Li Ming; Pu, Chun Sheng; Liu, Jing; Ma, Bo; Khan, Nasir

2017-01-01

Flowing gel plugging and low-frequency vibration oil extraction technology have been widely applied in low-permeability formation. High probability of overlapping in action spheres of two technologies might lead to poor operating efficiency during gel injection. Study on flowing gel rheological properties under low-frequency vibration was essential, which was carried out indoor with viscosity measurement. Potential dynamic mechanisms were analyzed for the rheological variation. Under low-frequency vibration, gel rheological properties were found to be obviously influenced, with vibration delaying gel cross-linking in induction period, causing a two-stage gel viscosity change in acceleration period, and decreasing gel strength in stable period. Surface of gel system under vibration presented different fluctuating phenomenon from initial harmonic vibrating to heterogeneous fluctuating (droplet separation might appear) to final harmonic vibrating again. Dynamic displacement in unconsolidated sand pack revealed that low-frequency vibration during gel injection might be a measure to achieve deep profile control, with the gel injection depth increased by 65.8 % compared with the vibration-free sample. At last, suggestions for field test were given in the paper to achieve lower injection friction and better gel plugging efficiency.

Vibration effects of the space shuttle main engine high pressure oxidizer turbopump bellows

NASA Technical Reports Server (NTRS)

Harp, J. A.

1978-01-01

A welded metal bellows was subjected to a series of vibration tests in a 400 psi oxygen environment to evaluate the effects of the bellows convolutes rubbing on the damper ring in the high pressure oxidizer turbopump of the space shuttle main engine. The bellows was subjected to approximately 2 million cycles at 0.007 in. double amplitude displacement during this series of tests, at a frequency of 400 Hz. Intrumentation of the test specimen revealed no significant heat buildup caused by the rubbing of the bellows convolutes on the damper ring. A final destruct test was made to determine if a fire would result if the bellows ruptured in the 400 psi oxygen environment, thus exposing a fresh metal surface. The vibration input was changed to 0.8 in. double amplitude displacement at 20 Hz to intentionally rupture the bellows. Failure occurred after 2.5 sec; no fire or heat buildup was encountered.

Magnetic Excitation for Spin Vibration Testing

NASA Technical Reports Server (NTRS)

Johnson, Dexter; Mehmed, Oral; Brown, Gerald V.

1997-01-01

The Dynamic Spin Rig Laboratory (DSRL) at the NASA Lewis Research Center is a facility used for vibration testing of structures under spinning conditions. The current actuators used for excitation are electromagnetic shakers which are configured to apply torque to the rig's vertical rotor. The rotor is supported radially and axially by conventional bearings. Current operation is limited in rotational speed, excitation capability, and test duration. In an effort to enhance its capabilities, the rig has been initially equipped with a radial magnetic bearing which provides complementary excitation and shaft support. The new magnetic feature has been used in actual blade vibration tests and its performance has been favorable. Due to the success of this initial modification further enhancements are planned which include making the system fully magnetically supported. This paper reports on this comprehensive effort to upgrade the DSRL with an emphasis on the new magnetic excitation capability.

Modeling and dynamic environment analysis technology for spacecraft

NASA Astrophysics Data System (ADS)

Fang, Ren; Zhaohong, Qin; Zhong, Zhang; Zhenhao, Liu; Kai, Yuan; Long, Wei

Spacecraft sustains complex and severe vibrations and acoustic environments during flight. Predicting the resulting structures, including numerical predictions of fluctuating pressure, updating models and random vibration and acoustic analysis, plays an important role during the design, manufacture and ground testing of spacecraft. In this paper, Monotony Integrative Large Eddy Simulation (MILES) is introduced to predict the fluctuating pressure of the fairing. The exact flow structures of the fairing wall surface under different Mach numbers are obtained, then a spacecraft model is constructed using the finite element method (FEM). According to the modal test data, the model is updated by the penalty method. On this basis, the random vibration and acoustic responses of the fairing and satellite are analyzed by different methods. The simulated results agree well with the experimental ones, which shows the validity of the modeling and dynamic environment analysis technology. This information can better support test planning, defining test conditions and designing optimal structures.

Structural Monitoring and Field Test for Kao Ping Hsi Cable-Stayed Bridge in Taiwan

NASA Astrophysics Data System (ADS)

Chen, Chern-Hwa

2010-05-01

This work applies system identification techniques to analyze the measured data from structural monitoring system and field test for Kao Ping Hsi cable-stayed bridge in Taiwan. The continuous wavelet transform algorithm can be used to identify the dynamic characteristics of the cable-stayed bridge under environmental vibration. The identified results with traffic flow were compared with those obtained from ambient vibration test. The excellent agreement both the identified results from different traffic conditions indicates that the traffic flow would not significantly change the natural frequencies of the cable-stayed bridge. The modal parameters identified from the field vibration test will be compared with those used in the finite element analysis. The results obtained herein will be used as the damage detection for monitoring the long-term safety of the Kao Ping Hsi cable-stayed bridge by using structural monitoring system.

Survey of Active Vibration Isolation Systems for Microgravity Applications

NASA Technical Reports Server (NTRS)

Grodsinsky, Carlos M.; Whorton, Mark S.

2000-01-01

In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration-sensitive experiments has gained increasing visibility. To date, three active microgravity vibration isolation systems have successfully been demonstrated in flight. A tutorial discussion of the microgravity vibration isolation problem, including a description of the acceleration environment of the International Space Station and attenuation requirements, as well as a comparison or the dynamics of passive isolation, active rack-level isolation, and active payload-level isolation is provided. The flight test results of the three demonstrated systems: suppression of transient accelerations by levitation, the microgravity vibration isolation mount, and the active rack isolation system are surveyed.

Correlation of finite element free vibration predictions using random vibration test data. M.S. Thesis - Cleveland State Univ.

NASA Technical Reports Server (NTRS)

Chambers, Jeffrey A.

1994-01-01

Finite element analysis is regularly used during the engineering cycle of mechanical systems to predict the response to static, thermal, and dynamic loads. The finite element model (FEM) used to represent the system is often correlated with physical test results to determine the validity of analytical results provided. Results from dynamic testing provide one means for performing this correlation. One of the most common methods of measuring accuracy is by classical modal testing, whereby vibratory mode shapes are compared to mode shapes provided by finite element analysis. The degree of correlation between the test and analytical mode shapes can be shown mathematically using the cross orthogonality check. A great deal of time and effort can be exhausted in generating the set of test acquired mode shapes needed for the cross orthogonality check. In most situations response data from vibration tests are digitally processed to generate the mode shapes from a combination of modal parameters, forcing functions, and recorded response data. An alternate method is proposed in which the same correlation of analytical and test acquired mode shapes can be achieved without conducting the modal survey. Instead a procedure is detailed in which a minimum of test information, specifically the acceleration response data from a random vibration test, is used to generate a set of equivalent local accelerations to be applied to the reduced analytical model at discrete points corresponding to the test measurement locations. The static solution of the analytical model then produces a set of deformations that once normalized can be used to represent the test acquired mode shapes in the cross orthogonality relation. The method proposed has been shown to provide accurate results for both a simple analytical model as well as a complex space flight structure.

Ground vibration test of F-16 airplane with initial decoupler pylon

NASA Technical Reports Server (NTRS)

Cazier, F. W., Jr.; Kehoe, M. W.

1984-01-01

A ground vibration test was conducted on an F-16 airplane loaded on each wing with a 370-gal tank mounted on a standard pylon, a GBU-8 store mounted on a decoupler pylon, and an AIM-9J missile mounted on a wing-tip launcher. The decoupler pylon is a passive wing/store flutter-suppression device. The test was conducted prior to initial flight tests to determine the modal frequencies, mode shapes, and structural damping coefficients. The data presented include frequency response plots, force effect plots, and limited mode shape data.

Magnetic shielding and vacuum test for passive hydrogen masers

NASA Technical Reports Server (NTRS)

Gubser, D. U.; Wolf, S. A.; Jacoby, A. B.; Jones, L. D.

1982-01-01

Vibration tests on high permeability magnetic shields used in the SAO-NRL Advanced Development Model (ADM) hydrogen maser were made. Magnetic shielding factors were measured before and after vibration. Preliminary results indicate considerable (25%) degradation. Test results on the NRL designed vacuum pumping station for the ADM hydrogen maser are also discussed. This system employs sintered zirconium carbon getter pumps to pump hydrogen plus small ion pumps to pump the inert gases. In situ activation tests and pumping characteristics indicate that the system can meet design specifications.

Modal Analysis of MARS Solar Panel and Planar Vibrations

NASA Technical Reports Server (NTRS)

Simonyan, Andranik; Williams, R. Brett

2007-01-01

This slide presentation reviews the modal analysis of MARS solar panels and the planar vibrations. Included are views of the solar panels mock-up assembly, a view of the test seup,a view of the plot from the test, with the raw numbers of the frequencies in Hz values with the mode number, the spatial acceleration plots of Center sub panel at resonant frequencies, predictions from the Finite element models, an explanation of the two test that were done on the plate and the results from both tests,

Test operation of a pneumatic vibrating-blade planer in phosphate and coal: a progress report on planer-mining research, 1958--1960

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, W.S.

1962-01-01

Third report in a series describes progress in research with the pneumatic vibrating-blade planer: Tests conducted in the Arickaree phosphate mine in Utah and in the Roslyn No. 9 coal mine in Washington. After the Arickaree mine tests, the bit design was improved, and tests were conducted in the Roslyn No. 9 mine to check the modifications. The redesigned cutting tool was an improvement, and the possibility of planing coal as well as phosphate was proved.

Microelectronics Instrument Products Shock and Vibration Electro-optics: C-Qualification Test Report

NASA Technical Reports Server (NTRS)

1994-01-01

In this test report all measurements made during testing are recorded in ATP 20049 DS data sheets and are included in the log. The motor/encoder (henceforth referred to as the UUT) test sequence began with a baseline functional evaluation, which demonstrated that the motor satisfied the operating torque, cogging torque, winding resistance, and mechanical requirements of SOW. In addition, the encoder electrical requirements were verified, as well as the alignment of the encoder outputs relative tc, the motor shaft position. There were no discrepancies observed in this portion of the test. The UUT was then exposed to a number of environments, including thermal vacuum, thermal cycling, random and sine vibration, and mechanical shock. During the thermal environments, the performance of the UUT under load was verified at specified points in the cycles, as described in ATP 20049. In addition, the UUT was bench tested between the two thermal environments. No anomalies were observed during the thermal tests. The load attachment method was subsequently corrected, and vibration of S/N 0002 began while 0003 was being repaired.

Vibration Testing of Electrical Cables to Quantify Loads at Tie-Down Locations

NASA Technical Reports Server (NTRS)

Dutson, Joseph D.

2013-01-01

The standard method for defining static equivalent structural load factors for components is based on Mile s equation. Unless test data is available, 5% critical damping is assumed for all components when calculating loads. Application of this method to electrical cable tie-down hardware often results in high loads, which often exceed the capability of typical tie-down options such as cable ties and P-clamps. Random vibration testing of electrical cables was used to better understand the factors that influence component loads: natural frequency, damping, and mass participation. An initial round of vibration testing successfully identified variables of interest, checked out the test fixture and instrumentation, and provided justification for removing some conservatism in the standard method. Additional testing is planned that will include a larger range of cable sizes for the most significant contributors to load as variables to further refine loads at cable tie-down points. Completed testing has provided justification to reduce loads at cable tie-downs by 45% with additional refinement based on measured cable natural frequencies.

Structural Analysis and Testing of an Erectable Truss for Precision Segmented Reflector Application

NASA Technical Reports Server (NTRS)

Collins, Timothy J.; Fichter, W. B.; Adams, Richard R.; Javeed, Mehzad

1995-01-01

This paper describes analysis and test results obtained at Langley Research Center (LaRC) on a doubly curved testbed support truss for precision reflector applications. Descriptions of test procedures and experimental results that expand upon previous investigations are presented. A brief description of the truss is given, and finite-element-analysis models are described. Static-load and vibration test procedures are discussed, and experimental results are shown to be repeatable and in generally good agreement with linear finite-element predictions. Truss structural performance (as determined by static deflection and vibration testing) is shown to be predictable and very close to linear. Vibration test results presented herein confirm that an anomalous mode observed during initial testing was due to the flexibility of the truss support system. Photogrammetric surveys with two 131-in. reference scales show that the root-mean-square (rms) truss-surface accuracy is about 0.0025 in. Photogrammetric measurements also indicate that the truss coefficient of thermal expansion (CTE) is in good agreement with that predicted by analysis. A detailed description of the photogrammetric procedures is included as an appendix.

Influence of resistance load on neuromuscular response to vibration training.

PubMed

Luo, Jin; Clarke, Michael; McNamara, Brian; Moran, Kieran

2009-03-01

The purpose of this study was to examine the influence of resistance load on the acute and acute residual effects of vibration training, with vibration applied directly to the bicep tendon in a maximal-effort dynamic resistance exercise (3 sets of maximal-effort bicep curls). Eleven participants were exposed to 4 training conditions in random order: exercise with 1 of 2 different loads (40% 1-repetition maximum [RM] or 70% 1RM load) combined with 1 of 2 vibration conditions (vibration [1.2 mm, 65 Hz] or sham vibration). Five minutes before and after the exercise, a set of maximal-effort bicep curls with a load of either 40 or 70% 1RM was performed as the pre- and posttraining test. Concentric elbow joint angular velocity, moment and power, and bicep root mean square electromyography (EMGrms) were measured during training and in the pre- and posttraining tests. The results show that during training (acute effect) and at 5 minutes after training (acute residual effect), vibration did not induce a significant change in EMGrms, mean and peak angular velocities, moment and power, time to peak power, and initial power at 100 milliseconds after the start of the concentric phase for either resistance load. Therefore, in aiming to train neuromuscular output using maximal-effort dynamic contractions (40 and 70% 1RM), there is no benefit in employing direct vibration, at least with a 1.2-mm amplitude and 65-Hz frequency. However, the amplitude of 1.2 mm may be too high to effectively stimulate neuromuscular output in maximal-effort dynamic contractions per se.

Active Vibration Control of Hydrodynamic Journal Bearings

NASA Astrophysics Data System (ADS)

Tůma, J.; Šimek, J.; Škuta, J.; Los, J.; Zavadil, J.

Rotor instability is one of the most serious problems of high-speed rotors supported by sliding bearings. With constantly increasing parameters, new machines problems with rotor instability are encountered more and more often. Even though there are many solutions based on passive improvement of the bearing geometry to enlarge the operational speed range of the journal bearing, the paper deals with a working prototype of a system for the active vibration control of journal bearings with the use of piezoactuators. The actively controlled journal bearing consists of a movable bushing, which is actuated by two piezoactuators. It is assumed that the journal vibration is measured by a pair of proximity probes. Force produced by piezoactuators and acting at the bushing is controlled according to error signals derived from the proximity probe output signals. The active vibration control was tested with the use of a test rig, which consists of a rotor supported by two controllable journal bearings and driven by an inductive motor up to 23,000 rpm. As it was proved by experiments the active vibration control extends considerably the range of the rotor operational speed.

Impact of the plasmonic near- and far-field resonance-energy shift on the enhancement of infrared vibrational signals.

PubMed

Vogt, Jochen; Huck, Christian; Neubrech, Frank; Toma, Andrea; Gerbert, David; Pucci, Annemarie

2015-09-07

We report on the impact of the differing spectral near- and far-field properties of resonantly excited gold nanoantennas on the vibrational signal enhancement in surface-enhanced infrared absorption (SEIRA). The knowledge on both spectral characteristics is of considerable importance for the optimization of plasmonic nanostructures for surface-enhanced spectroscopy techniques. From infrared micro-spectroscopic measurements, we simultaneously obtain spectral information on the plasmonic far-field response and, via SEIRA spectroscopy of a test molecule, on the near-field enhancement. The molecular test layer of 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) was deposited on the surface of gold nanoantennas with different lengths and thus different far-field resonance energies. We carefully studied the Fano-type vibrational lines in a broad spectral window, in particular, how the various vibrational signals are enhanced in relation to the ratio of the far-field plasmonic resonance and the molecular vibrational frequencies. As a detailed experimental proof of former simulation studies, we show the clearly red-shifted maximum SEIRA enhancement compared to the far-field resonance.

Combination of process and vibration data for improved condition monitoring of industrial systems working under variable operating conditions

NASA Astrophysics Data System (ADS)

Ruiz-Cárcel, C.; Jaramillo, V. H.; Mba, D.; Ottewill, J. R.; Cao, Y.

2016-01-01

The detection and diagnosis of faults in industrial processes is a very active field of research due to the reduction in maintenance costs achieved by the implementation of process monitoring algorithms such as Principal Component Analysis, Partial Least Squares or more recently Canonical Variate Analysis (CVA). Typically the condition of rotating machinery is monitored separately using vibration analysis or other specific techniques. Conventional vibration-based condition monitoring techniques are based on the tracking of key features observed in the measured signal. Typically steady-state loading conditions are required to ensure consistency between measurements. In this paper, a technique based on merging process and vibration data is proposed with the objective of improving the detection of mechanical faults in industrial systems working under variable operating conditions. The capabilities of CVA for detection and diagnosis of faults were tested using experimental data acquired from a compressor test rig where different process faults were introduced. Results suggest that the combination of process and vibration data can effectively improve the detectability of mechanical faults in systems working under variable operating conditions.

Vascular and nerve damage in workers exposed to vibrating tools. The importance of objective measurements of exposure time.

PubMed

Gerhardsson, Lars; Balogh, Istvan; Hambert, Per-Arne; Hjortsberg, Ulf; Karlsson, Jan-Erik

2005-01-01

The aim of the present study was to compare the development of vibration white fingers (VWF) in workers in relation to different ways of exposure estimation, and their relationship to the standard ISO 5349, annex A. Nineteen vibration exposed (grinding machines) male workers completed a questionnaire followed by a structured interview including questions regarding their estimated hand-held vibration exposure. Neurophysiological tests such as fractionated nerve conduction velocity in hands and arms, vibrotactile perception thresholds and temperature thresholds were determined. The subjective estimation of the mean daily exposure-time to vibrating tools was 192 min (range 18-480 min) among the workers. The estimated mean exposure time calculated from the consumption of grinding wheels was 42 min (range 18-60 min), approximately a four-fold overestimation (Wilcoxon's signed ranks test, p<0.001). Thus, objective measurements of the exposure time, related to the standard ISO 5349, which in this case were based on the consumption of grinding wheels, will in most cases give a better basis for adequate risk assessment than self-exposure assessment.

Analysis of motor fan radiated sound and vibration waveform by automatic pattern recognition technique using "Mahalanobis distance"

NASA Astrophysics Data System (ADS)

Toma, Eiji

2018-06-01

In recent years, as the weight of IT equipment has been reduced, the demand for motor fans for cooling the interior of electronic equipment is on the rise. Sensory test technique by inspectors is the mainstream for quality inspection of motor fans in the field. This sensory test requires a lot of experience to accurately diagnose differences in subtle sounds (sound pressures) of the fans, and the judgment varies depending on the condition of the inspector and the environment. In order to solve these quality problems, development of an analysis method capable of quantitatively and automatically diagnosing the sound/vibration level of a fan is required. In this study, it was clarified that the analysis method applying the MT system based on the waveform information of noise and vibration is more effective than the conventional frequency analysis method for the discrimination diagnosis technology of normal and abnormal items. Furthermore, it was found that due to the automation of the vibration waveform analysis system, there was a factor influencing the discrimination accuracy in relation between the fan installation posture and the vibration waveform.

Assessment of coarse and fine hand motor performance in asymptomatic subjects exposed to hand-arm vibration.

PubMed

Popević, Martin B; Janković, Srđan M; Borjanović, Srđan S; Jovičić, Slavica R; Tenjović, Lazar R; Milovanović, Aleksandar P S; Bulat, Petar

2014-03-01

A frequently encountered exposure profile for hand-arm vibration in contemporary occupational setting comprises workers with a long history of intermittent exposure but without detectable signs of hand-arm vibration syndrome (HAVS). Yet, most of the published studies deal with developed HAVS cases, rarely discussing the biological processes that may be involved in degradation of manual dexterity and grip strength when it can be most beneficial - during the asymptomatic stage. In the present paper, a group of 31 male asymptomatic vibration-exposed workers (according to the Stockholm Workshop Scale) were compared against 30 male controls. They were tested using dynamometry and dexterimetry (modelling coarse and fine manual performance respectively) and cold provocation was done to detect possible differences in manual performance drop on these tests. The results showed reduced manual dexterity but no significant degradation in hand grip strength in the exposed subjects. This suggests that intermittent exposure profile and small cumulative vibration dose could only lead to a measurable deficit in manual dexterity but not hand grip strength even at non-negligible A(8) levels and long term exposures.

Ground shake test of the UH-60A helicopter airframe and comparison with NASTRAN finite element model predictions

NASA Technical Reports Server (NTRS)

Howland, G. R.; Durno, J. A.; Twomey, W. J.

1990-01-01

Sikorsky Aircraft, together with the other major helicopter airframe manufacturers, is engaged in a study to improve the use of finite element analysis to predict the dynamic behavior of helicopter airframes, under a rotorcraft structural dynamics program called DAMVIBS (Design Analysis Methods for VIBrationS), sponsored by the NASA-Langley. The test plan and test results are presented for a shake test of the UH-60A BLACK HAWK helicopter. A comparison is also presented of test results with results obtained from analysis using a NASTRAN finite element model.

[Quantification of the gnostic sensitivity via measurement of the vibration threshold and of finger tip sensation].

PubMed

Oosterhuis, H J; Bouwsma, C; van Halsema, B; Hollander, R A; Kros, C J; Tombroek, I

1992-10-03

Quantification of vibration perception and fingertip sensation in routine neurological examination. Neurological Clinic, University Hospital, Groningen, the Netherlands. Prospective, controlled investigation. Vibration perception and fingertip sensation were quantified in a large group of normal control persons of various ages and in neurological patients and compared with the usual sensory tests at routine neurological examination. The vibration perception limit was measured with a biothesiometer without accelerometer, the fingertip sensation with a device for two-point discrimination slightly modified according to Renfrew ('Renfrew meter'). Concordance of the tests was studied by calculating kappa values. The normal values of both sensory qualities had a log-normal distribution and increased with age. The values obtained with the Renfrew meter correlated well with those of the two-point discrimination and stereognosis but were systematically higher than those indicated by Renfrew. Both methods appear useful at routine neurological examination if certain measuring precautions are taken.

Vibration considerations for cryogenic tanks using glass bubbles insulation

NASA Astrophysics Data System (ADS)

Werlink, Rudy John; Fesmire, James; Sass, Jared P.

2012-06-01

The use of glass bubbles as an efficient and practical thermal insulation system hasbeen previously demonstrated in cryogenic storage tanks. One such example is a spherical,vacuum-jacketed liquid hydrogen vessel of 218,000 liter capacity where the boiloff rate hasbeen reduced by approximately 50 percent. Further applications may include non-stationarytanks such as mobile tankers and tanks with extreme duty cycles or exposed to significantvibration environments. Space rocket launch events and mobile tanker life cycles representtwo harsh cases of mechanical vibration exposure. A number of bulk fill insulationmaterials including glass bubbles, perlite powders, and aerogel granules were tested forvibration effects and mechanical behavior using a custom design holding fixture subjectedto random vibration on an Electrodynamic Shaker. The settling effects for mixtures ofinsulation materials were also investigated. The vibration test results and granular particleanalysis are presented with considerations and implications for future cryogenic tankapplications.

Fault detection of gearbox using time-frequency method

NASA Astrophysics Data System (ADS)

Widodo, A.; Satrijo, Dj.; Prahasto, T.; Haryanto, I.

2017-04-01

This research deals with fault detection and diagnosis of gearbox by using vibration signature. In this work, fault detection and diagnosis are approached by employing time-frequency method, and then the results are compared with cepstrum analysis. Experimental work has been conducted for data acquisition of vibration signal thru self-designed gearbox test rig. This test-rig is able to demonstrate normal and faulty gearbox i.e., wears and tooth breakage. Three accelerometers were used for vibration signal acquisition from gearbox, and optical tachometer was used for shaft rotation speed measurement. The results show that frequency domain analysis using fast-fourier transform was less sensitive to wears and tooth breakage condition. However, the method of short-time fourier transform was able to monitor the faults in gearbox. Wavelet Transform (WT) method also showed good performance in gearbox fault detection using vibration signal after employing time synchronous averaging (TSA).