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Sample records for fatigue test results

  1. Structural fatigue test results for large wind turbine blade sections

    NASA Technical Reports Server (NTRS)

    Faddoul, J. R.; Sullivan, T. L.

    1982-01-01

    In order to provide quantitative information on the operating life capabilities of wind turbine rotor blade concepts for root-end load transfer, a series of cantilever beam fatigue tests was conducted. Fatigue tests were conducted on a laminated wood blade with bonded steel studs, a low cost steel spar (utility pole) with a welded flange, a utility pole with additional root-end thickness provided by a swaged collar, fiberglass spars with both bonded and nonbonded fittings, and, finally, an aluminum blade with a bolted steel fitting (Lockheed Mod-0 blade). Photographs, data, and conclusions for each of these tests are presented. In addition, the aluminum blade test results are compared to field failure information; these results provide evidence that the cantilever beam type of fatigue test is a satisfactory method for obtaining qualitative data on blade life expectancy and for identifying structurally underdesigned areas (hot spots).

  2. Hot fire fatigue testing results for the compliant combustion chamber

    NASA Technical Reports Server (NTRS)

    Pavli, Albert J.; Kazaroff, John M.; Jankovsky, Robert S.

    1992-01-01

    A hydrogen-oxygen subscale rocket combustion chamber was designed incorporating an advanced design concept to reduce strain and increase life. The design permits unrestrained thermal expansion of a circumferential direction and, thereby, provides structural compliance during the thermal cycling of hot-fire testing. The chamber was built and test fired at a chamber pressure of 4137 kN/sq m (600 psia) and a hydrogen-oxygen mixture ratio of 6.0. Compared with a conventional milled-channel configuration, the new structurally compliant chamber had a 134 or 287 percent increase in fatigue life, depending on the life predicted for the conventional configuration.

  3. Screening Test Results of Fatigue Properties of type 316LN Stainless Steel in Mercury

    SciTech Connect

    Pawel, S.J.

    1999-05-20

    Fully reversed, load-controlled uniaxial push-pull fatigue tests at room temperature have been performed in air and in mercury on specimens of type 316LN stainless steel. The results indicate a significant influence of mercury on fatigue properties. Compared to specimens tested in air, specimens tested in mercury had reproducibly shorter fatigue lives (by a factor of 2-3), and fracture faces exhibiting intergranular cracking. Preliminary indications are that crack initiation in each environment is similar, but mercury significantly accelerates crack propagation.

  4. Report on FY15 Alloy 617 SMT Creep-Fatigue Test Results

    SciTech Connect

    Wang, Yanli; Jetter, Robert I.; Baird, Seth T.; Pu, Chao; Sham, Sam

    2015-06-22

    For the temperature range of 990-950C, Alloy 617 is a candidate IHX structural material for high temperature gas reactors (HTGRs) because of its high temperature creep properties. Also, its superior strength over a broad temperature range also offers advantages for certain component applications. In order for the designers to be able to use Alloy 617 for these high temperature components, Alloy 617 has to be approved for use in Section III (the nuclear section) of the ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code. A plan has been developed to propose a Code Case for use of Alloy 617 at elevated temperature in Section III of the ASME Code by September 2015. There has not been a new high temperature material approved for use in Section III for almost 20 years. The Alloy 617 Code Case effort would lead the way to establish a path for Code qualification of new high temperature materials of interest to other advanced SMRs. Creep-fatigue at elevated temperatures is the most damaging structural failure mode. In the past 40 years significant efforts have been devoted to the elevated temperature Code rule development in Section III, Subsection NH* of the ASME Boiler and Pressure Vessel Code, to ascertain conservative structural designs to prevent creep-fatigue failure. The current Subsection NH creep-fatigue procedure was established by the steps of (1) analytically obtaining a detailed stress-strain history, (2) comparing the stress and strain components to cyclic test results deconstructed into stress and strain quantities, and (3) recombining the results to obtain a damage function in the form of the so-called creep-fatigue damage-diagram. The deconstruction and recombination present difficulties in evaluation of test data and determination of cyclic damage in design. The uncertainties in these steps lead to the use of overly conservative design factors in the current creep-fatigue procedure. In addition, and of major significance to the

  5. Rolling-element fatigue life of silicon nitride balls: Preliminary test results

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.

    1972-01-01

    Hot pressed silicon nitride was evaluated as a rolling element bearing material. The five-ball fatigue tester was used to test 12.7 mm (0.500 in.) diameter balls at a maximum Hertz stress of 800,000 psi at a race temperature of 130 F. The fatigue spalls in the silicon nitride resembled those in typical bearing steels. The ten-percent fatigue life of the silicon nitride balls was approximately one-eighth to one-fifth that of typical bearing steels (52100 and M-50). The load capacity of the silicon nitride was approximately one-third that of typical bearing steels. The load capacity of the silicon nitride was significantly higher than previously tested ceramic materials for rolling element bearings.

  6. Multiaxial fatigue low cycle fatigue testing

    NASA Technical Reports Server (NTRS)

    Zamrik, S. Y.

    1985-01-01

    Multiaxial testing methods are reviewed. Advantages and disadvantages of each type test is discussed. Significant multiaxial data available in the literature is analyzed. The yield theories are compared for multiaxial fatigue analysis.

  7. Creep-Fatigue Interactions in a 9 Pct Cr-1 Pct Mo Martensitic Steel: Part I. Mechanical Test Results

    NASA Astrophysics Data System (ADS)

    Fournier, B.; Sauzay, M.; Caës, C.; Noblecourt, M.; Mottot, M.; Allais, L.; Tournie, I.; Pineau, A.

    2009-02-01

    Creep-fatigue (CF) tests are carried out on a modified 9 pct Cr-1 pct Mo (P91) steel at 550 °C. These CF tests are strain controlled during the cyclic part of the stress-strain hysteresis loop and then load controlled when the stress is maintained at its maximum value, to produce a prescribed value of the creep strain before cyclic deformation is reversed under strain-controlled conditions. The observed cyclic softening implies that the applied creep stress continuously decreases with the number of cycles. However, the minimum creep rates measured at the end of the holding periods do not decrease when the applied stress decreases. The minimum creep rates measured at the end of these tests can be hundreds of times faster than those observed for the as-received material. This acceleration of creep rates can be to the microstructural coarsening and to the decrease of the dislocation density observed after fatigue and CF loadings. Cyclic creep tests consisting of very long holding periods interrupted by unloading/reloading are also carried out. These results suggest that cyclic loadings affect the creep lifetime and flow behavior only if a plastic strain is applied during cycling. Creep tests carried out on a material cyclically prestrained and fatigue tests carried out on a material previously deformed in creep confirm that the deterioration of the mechanical properties is much faster in fatigue and CF compared to creep.

  8. An assessment of wind tunnel test data on flexible thermal protection materials and results of new fatigue tests of threads

    NASA Technical Reports Server (NTRS)

    Coe, Charles F.

    1985-01-01

    Advanced Flexible Reusable Surface Insulation (AFRSI) was developed as a replacement for the low-temperature (white) tiles on the Space Shuttle. The first use of the AFRSI for an Orbiter flight was on the OMS POD of Orbiter (OV-099) for STS-6. Post flight examination after STS-6 showed that damage had occurred to the AFRSI during flight. The failure anomaly between previous wind-tunnel tests and STS-6 prompted a series of additional wind tunnel tests to gain an insight as to the cause of the failure. An assessment of all the past STS-6 wind tunnel tests pointed out the sensitivity of the test results to scaling of dynamic loads due to the difference of boundary layer thickness, and the material properties as a result of exposure to heating. The thread component of the AFRSI was exposed to fatigue testing using an apparatus that applied pulsating aerodynamic loads on the threads similar to the loads caused by an oscillating shock. Comparison of the mean values of the number-of-cycles to failure showed that the history of the thread was the major factor in its performance. The thread and the wind tunnel data suggests a mechanism of failure for the AFRSI.

  9. Hydraulic Fatigue-Testing Machine

    NASA Technical Reports Server (NTRS)

    Hodo, James D.; Moore, Dennis R.; Morris, Thomas F.; Tiller, Newton G.

    1987-01-01

    Fatigue-testing machine applies fluctuating tension to number of specimens at same time. When sample breaks, machine continues to test remaining specimens. Series of tensile tests needed to determine fatigue properties of materials performed more rapidly than in conventional fatigue-testing machine.

  10. Results of an interlaboratory fatigue test program conducted on alloy 800H at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Ellis, J. R.

    1985-01-01

    The experimental approach adopted for low cycle fatigue tests of alloy 800H involved the use of electrohydraulic test systems, hour glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas were complicated by the lack of reliable data for the heat of Alloy 800H under investigation. The method adopted was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA Lewis. Fatigue tests were conducted on both solid and turbular specimens at temperatures of 20, 593, and 760 C and strain ranges of 2.0, 1.0, and 0.5 percent. The subject test method can, under certain circumstances, produce fatigue data which are serious in error. This approach subsequently was abandoned at General Atomic Company in favor of parallel gage length specimens and axial extensiometers.

  11. Reversal bending fatigue testing

    SciTech Connect

    Wang, Jy-An John; Wang, Hong; Tan, Ting

    2014-10-21

    Embodiments for apparatuses for testing reversal bending fatigue in an elongated beam are disclosed. Embodiments are configured to be coupled to first and second end portions of the beam and to apply a bending moment to the beam and create a pure bending condition in an intermediate portion of the beam. Embodiments are further configured to cyclically alternate the direction of the bending moment applied to the beam such that the intermediate portion of the beam cyclically bends in opposite directions in a pure bending condition.

  12. Fatigue testing of drill pipe

    SciTech Connect

    Grondin, G.Y.; Kulak, G.L.

    1994-06-01

    Twenty-nine tests in air and 27 tests in a 3.5% NaCl solution were conducted to test the fatigue strength of Grade E 4.5-in.-OD, 16.6-lbm/ft (114-mm-OD, 24.7-kg/m) drillpipe. The effects of stress range, mean stress, corrosion, and upset geometry were tested on the drillpipe body alone and on specimens that included the tool joint, upset, and drillpipe body. Stress range and mean stress effects were significant in noncorrosive and corrosive environments. The effect of upset geometry was minimal on an external upset compared with that on an internal/external upset. Among the specimens that failed, grinding marks on the drillpipe surface, which occurred during inspection at the mill, caused failure of about 60% of the specimens. Grinding created a notch effect and induced a detrimental residual-stress pattern on the pipe surface, which decreased drillpipe fatigue life. API guidelines for cumulative fatigue of Range 2 drillpipe were evaluated in light of these experimental test results and were found to be unsafe for drilling in noncorrosive conditions and possibly too conservative for corrosive conditions.

  13. Control system of the fatigue stand for material tests under combined bending with torsion loading and experimental results

    NASA Astrophysics Data System (ADS)

    Rozumek, Dariusz; Marciniak, Zbigniew

    2008-08-01

    The paper presents the control system of the fatigue test stand MZGS-200PL. Electric signals from the strain gauge Wheatstone bridges were processed with spectrum analyzer and the computer. In the computer, the signals were registered on the hard disk. The paper presents characteristics signals loading, power spectral density, autocorrelations and cross-correlation. The circular smooth specimens were tested. As compared with hydraulic machines for fatigue tests, the presented machine is reliable and simple, it works quietly, it allows to save energy, it is small and cheap. The test stand MZGS-200PL allows to perform tests under cyclic proportional, non-proportional and random bending with torsion, as well as tests under pure bending and pure torsion.

  14. Results of High R-Ratio Fatigue Crack Growth Tests on 304 Stainless Steel in Low Oxygen Water

    SciTech Connect

    Evans, W. M.; Wire, G. L.

    2002-08-01

    Fatigue crack growth rate tests were performed on a 304 stainless steel compact tension (CT) specimen in water with 40-60 cc/kg H[sub]2. Data in the literature for CT tests show minor environmental effects in hydrogenated water, but higher effects in oxygenated water. However, the PWR data presented by Bernard, et al (1979) were taken at low stress ratios (R=0.05) and high stress intensity levels (delta K=16-41 MPa square root m). The purpose of these tests is to explore the crack growth rate characteristics of 304 SS in hydrogenated water at higher R values (0.7 and 0.83) and lower delta K values (11.0 and 7.7 MPa square root m). Each set of R, delta K conditions were tested at frequencies of 0.1, 0.01 and 0.001 Hz. The results show a pronounced effect on crack growth rates when compared to available literature data on air rates.

  15. A Very High-Cycle Fatigue Test and Fatigue Properties of TC17 Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Shengbo; Gao, Chao; Cheng, Li; Li, Xiaowei; Feng, Yu

    2016-03-01

    The present work studied the very high-cycle fatigue (VHCF) test and fatigue properties of TC17 titanium alloy. The specimens for bending vibration were designed using the finite element method and the VHCF tests were conducted by using the ultrasonic fatigue testing system. The results indicated that there is no the fatigue limit for TC17 titanium alloy, and the S-N curve shows a continuously descending trend. The fatigue crack initiates at the specimen surface within the range of VHCF and the VHCF lives follow the log-normal distribution more closely.

  16. Material Fatigue Testing System

    NASA Technical Reports Server (NTRS)

    Gilley, P. J. (Inventor)

    1973-01-01

    A system for cyclicly applying a varying load to a material under test is described. It includes a load sensor which senses the magnitude of load being applied to a material, and, upon sensing a selected magnitude of loading, causes the load to be maintained for a predetermined time and then cause the system to resume cyclical loading.

  17. Fatigue Crack Growth Rate Test Results for Al-Li 2195 Parent Metal, Variable Polarity Plasma Arc Welds and Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Hafley, Robert A.; Wagner, John A.; Domack, Marcia S.

    2000-01-01

    The fatigue crack growth rate of aluminum-lithium (Al-Li) alloy 2195 plate and weldments was determined at 200-F, ambient temperature and -320-F. The effects of stress ratio (R), welding process, orientation and thickness were studied. Results are compared with plate data from the Space Shuttle Super Lightweight Tank (SLWT) allowables program. Data from the current series of tests, both plate and weldment, falls within the range of data generated during the SLWT allowables program.

  18. Review of some results of the author's fatigue investigations with applications in engineering and material science

    NASA Astrophysics Data System (ADS)

    Buch, A.

    1994-04-01

    This document deals with research results mainly connected with the problem of fatigue calculations and various aspects of fatigue. It contains the following topics: Correlation between fatigue limits and ultimate tensile strength, Fatigue properties of pure metals, Analytical approach to notch-size effects in fatigue of aircraft sheet materials, Torsional fatigue life of axle shafts under program loading, Fatigue properties of aircraft lugs with interference fit, Comparison of various aircraft loading test results with the aid of Relative-Miner-Rule, The Relative Method in the case of Local-Strain-Approach, and Prediction of fatigue life.

  19. Creep-Fatigue Interaction Testing

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.

    2001-01-01

    Fatigue fives in metals are nominally time independent below 0.5 T(sub Melt). At higher temperatures, fatigue lives are altered due to time-dependent, thermally activated creep. Conversely, creep rates are altered by super. imposed fatigue loading. Creep and fatigue generally interact synergistically to reduce material lifetime. Their interaction, therefore, is of importance to structural durability of high-temperature structures such as nuclear reactors, reusable rocket engines, gas turbine engines, terrestrial steam turbines, pressure vessel and piping components, casting dies, molds for plastics, and pollution control devices. Safety and lifecycle costs force designers to quantify these interactions. Analytical and experimental approaches to creep-fatigue began in the era following World War II. In this article experimental and life prediction approaches are reviewed for assessing creep-fatigue interactions of metallic materials. Mechanistic models are also discussed briefly.

  20. Heat pipe fatigue test specimen: Metallurgical evaluation

    NASA Technical Reports Server (NTRS)

    Walak, Steven E.; Cronin, Michael J.; Grobstein, Toni

    1992-01-01

    An innovative creep/fatigue test was run to simulate the temperature, mechanical load, and sodium corrosion conditions expected in a heat pipe designed to supply thermal energy to a Stirling cycle power converter. A sodium-charged Inconel 718 heat pipe with a Nickel 200 screen wick was operated for 1090 hr at temperatures between 950 K (1250 F) and 1050 K (1430 F) while being subjected to creep and fatigue loads in a servo-hydraulic testing machine. After testing, the heat pipe was sectioned and examined using optical microscopy, scanning electron microscopy, and electron microprobe analysis with wavelength dispersive x-ray spectroscopy. The analysis concentrated on evaluating topographic, microstructural, and chemical changes in the sodium exposed surfaces of the heat pipe wall and wick. Surface changes in the evaporator, condenser, and adiabatic sections of the heat pipe were examined in an effort to correlate the changes with the expected sodium environment in the heat pipe. This report describes the setup, operating conditions, and analytical results of the sodium heat pipe fatigue test.

  1. Fatigue, Creep-Fatigue, and Thermomechanical Fatigue Life Testing of Alloys

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Lerch, Bradley A.; McGaw, Michael A.

    2000-01-01

    The fatigue crack initiation resistance of an alloy is determined by conducting a series of tests over a range of values of stress amplitude or strain range. The observed number of cycles to failure is plotted against the stress amplitude or strain range to obtain a fatigue curve. The fatigue properties quoted for an alloy are typically the constants used in the equation(s) that describe the fatigue curve. Fatigue lives of interest may be as low as 10(exp 2) or higher than 10(exp 9) cycles. Because of the enormous scatter associated with fatigue, dozens of tests may be needed to confidently establish a fatigue curve, and the cost may run into several thousands of dollars. To further establish the effects on fatigue life of the test temperature, environment, alloy condition, mean stress effects, creep-fatigue effects, thermomechanical cycling, etc. requires an extraordinarily large and usually very costly test matrix. The total effort required to establish the fatigue resistance of an alloy should not be taken lightly. Fatigue crack initiation tests are conducted on relatively small and presumed to be initially crack-free, samples of an alloy that are intended to be representative of the alloy's metallurgical and physical condition. Generally, samples are smooth and have uniformly polished surfaces within the test section. Some may have intentionally machined notches of well-controlled geometry, but the surface at the root of the notch is usually not polished. The purpose of polishing is to attain a reproducible surface finish. This is to eliminate surface finish as an uncontrolled variable. Representative test specimen geometries will be discussed later. Test specimens are cyclically loaded until macroscopically observable cracks initiate and eventually grow to failure. Normally, the fatigue failure life of a specimen is defined as the number of cycles to separation of the specimen into two pieces. Alternative definitions are becoming more common, particularly for

  2. Statistical treatment of fatigue test data

    SciTech Connect

    Raske, D.T.

    1980-01-01

    This report discussed several aspects of fatigue data analysis in order to provide a basis for the development of statistically sound design curves. Included is a discussion on the choice of the dependent variable, the assumptions associated with least squares regression models, the variability of fatigue data, the treatment of data from suspended tests and outlying observations, and various strain-life relations.

  3. Laser thermal shock and fatigue testing system

    NASA Astrophysics Data System (ADS)

    Fantini, Vincenzo; Serri, Laura; Bianchi, P.

    1997-08-01

    Thermal fatigue consists in repeatedly cycling the temperature of a specimen under test without any other constraint and stopping the test when predefined damage aspects. The result is a lifetime in terms of number of cycles. The parameters of the thermal cycle are the following: minimum and maximum temperature, time of heating, of cooling and time at high or at low temperature. When the temperature jump is very big and fast, phenomena of thermal shock can be induced. Among the numerous techniques used to perform these tests, the laser thermal fatigue cycling is very effective when fast heating of small and localized zones is required. That's the case of test performed to compare new and repaired blades of turbogas machines or components of combustion chambers of energy power plants. In order to perform these tests a thermal fatigue system, based on 1 kW Nd-YAG laser as source of heating, has been developed. The diameter of the heated zone of the specimen irradiated by the laser is in the range 0.5 - 20 mm. The temperatures can be chosen between 200 degree(s)C and 1500 degree(s)C and the piece can be maintained at high and/or low temperature from 0 s to 300 s. Temperature are measured by two sensors: a pyrometer for the high range (550 - 1500 degree(s)C) and a contactless thermocouple for the low range (200 - 550 degree(s)C). Two different gases can be blown on the specimen in the irradiated spot or in sample backside to speed up cooling phase. A PC-based control unit with a specially developed software performs PID control of the temperature cycle by fast laser power modulation. A high resolution vision system of suitable magnification is connected to the control unit to detect surface damages on the specimen, allowing real time monitoring of the tested zone as well as recording and reviewing the images of the sample during the test. Preliminary thermal fatigue tests on flat specimens of INCONEL 738 and HAYNES 230 are presented. IN738 samples, laser cladded by

  4. Fatigue

    MedlinePlus

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  5. Specimen Design for Fatigue Testing at Very High Frequencies

    NASA Astrophysics Data System (ADS)

    MATIKAS, T. E.

    2001-11-01

    Components in rotational machinery such as turbine blades used in military aircraft engines are subjected to low-amplitude, high-frequency loads in the kHz range. Under high cycle fatigue (HCF), the initiation state of a crack consumes most of the life of the component. Vibratory stresses may therefore result in unexpected failures of the material. Hence, there is a need for HCF studies to address HCF-related failures of turbine engines and to develop a life prediction methodology. Ultrasonic fatigue provides accelerated HCF testing enabling the simulation of realistic loading conditions for testing materials used in structural components subjected to vibratory stresses. Specimen design is critical for optimum ultrasonic fatigue testing. The objective of this study is therefore to develop analytical modelling necessary for the design of test coupons to be fatigue tested at ultrasonic frequencies.

  6. Evaluation of Giga-cycle Fatigue Properties of Austenitic Stainless Steels Using Ultrasonic Fatigue Test

    NASA Astrophysics Data System (ADS)

    Takahashi, Kyouhei; Ogawa, Takeshi

    Ultrasonic fatigue tests have been performed in austenitic stainless steel, SUS316NG, in order to investigate giga-cycle fatigue strength of pre-strained materials, i.e. 5, 10 and 20% tensile pre-strains and -20% compressive pre-strain. The pre-strains were applied before specimen machining. The austenitic stainless steels are known to exhibit remarkable self-heating during the fatigue experiment. Therefore, heat radiation method was established by setting fatigue specimens in a low temperature chamber at about -100°C. The self-heating was controlled by intermittent loading condition, which enabled us to maintain the test section of the specimens at about room temperature. The results revealed that the fatigue strength increased with increasing pre-strain levels. Fish-eye fracture was observed for -20% pre-strained specimen fractured at 4.11×107 cycles, while the other specimens exhibited ordinary fatigue fracture surface originated from stage I facet on the specimen surface. The increase in fatigue limit was predicted by Vickers hardness, HV, which depended on the size of indented region. The prediction was successful using HV values obtained by the size of the indented region similar to those of the stage I facets.

  7. Fatigue analysis and testing of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Greaves, Peter Robert

    This thesis focuses on fatigue analysis and testing of large, multi MW wind turbine blades. The blades are one of the most expensive components of a wind turbine, and their mass has cost implications for the hub, nacelle, tower and foundations of the turbine so it is important that they are not unnecessarily strong. Fatigue is often an important design driver, but fatigue of composites is poorly understood and so large safety factors are often applied to the loads. This has implications for the weight of the blade. Full scale fatigue testing of blades is required by the design standards, and provides manufacturers with confidence that the blade will be able to survive its service life. This testing is usually performed by resonating the blade in the flapwise and edgewise directions separately, but in service these two loads occur at the same time.. A fatigue testing method developed at Narec (the National Renewable Energy Centre) in the UK in which the flapwise and edgewise directions are excited simultaneously has been evaluated by comparing the Palmgren-Miner damage sum around the blade cross section after testing with the damage distribution caused by the service life. A method to obtain the resonant test configuration that will result in the optimum mode shapes for the flapwise and edgewise directions was then developed, and simulation software was designed to allow the blade test to be simulated so that realistic comparisons between the damage distributions after different test types could be obtained. During the course of this work the shortcomings with conventional fatigue analysis methods became apparent, and a novel method of fatigue analysis based on multi-continuum theory and the kinetic theory of fracture was developed. This method was benchmarked using physical test data from the OPTIDAT database and was applied to the analysis of a complete blade. A full scale fatigue test method based on this new analysis approach is also discussed..

  8. Computer controlled thermal fatigue test system

    SciTech Connect

    Schmale, D.T.; Jones, W.B.

    1986-01-01

    A servo-controlled hydraulic mechanical test system has been configured to conduct computer-controlled thermal fatigue tests. The system uses induction heating, a digital temperature controller, infrared pyrometry, forced air cooling, and quartz rod extensometry. In addition, a digital computer controls the tests and allows precise data analysis and interpretation.

  9. Mechanical degradation of fuel cell membranes under fatigue fracture tests

    NASA Astrophysics Data System (ADS)

    Khorasany, Ramin M. H.; Sadeghi Alavijeh, Alireza; Kjeang, Erik; Wang, G. G.; Rajapakse, R. K. N. D.

    2015-01-01

    The effects of cyclic stresses on the fatigue and mechanical stability of perfluorosulfonic acid (PFSA) membranes are experimentally investigated under standard fuel cell conditions. The experiments are conducted ex-situ by subjecting membrane specimens to cyclic uniaxial tension at controlled temperature and relative humidity. The fatigue lifetime is measured in terms of the number of cycles until ultimate fracture. The results indicate that the membrane fatigue lifetime is a strong function of the applied stress, temperature, and relative humidity. The fatigue life increases exponentially with reduced stresses in all cases. The effect of temperature is found to be more significant than that of humidity, with reduced fatigue life at high temperatures. The maximum membrane strain at fracture is determined to decrease exponentially with increasing membrane lifetime. At a given fatigue life, a membrane exposed to fuel cell conditions is shown to accommodate more plastic strain before fracture than one exposed to room conditions. Overall, the proposed ex-situ membrane fatigue experiment can be utilized to benchmark the fatigue lifetime of new materials in a fraction of the time and cost associated with conventional in-situ accelerated stress testing methods.

  10. Compression and compression fatigue testing of composite laminates

    NASA Technical Reports Server (NTRS)

    Porter, T. R.

    1982-01-01

    The effects of moisture and temperature on the fatigue and fracture response of composite laminates under compression loads were investigated. The structural laminates studied were an intermediate stiffness graphite-epoxy composite (a typical angle ply laimna liminate had a typical fan blade laminate). Full and half penetration slits and impact delaminations were the defects examined. Results are presented which show the effects of moisture on the fracture and fatigue strength at room temperature, 394 K (250 F), and 422 K (300 F). Static tests results show the effects of defect size and type on the compression-fracture strength under moisture and thermal environments. The cyclic tests results compare the fatigue lives and residual compression strength under compression only and under tension-compression fatigue loading.

  11. Fatigue crack growth testing of sub-clad defects

    SciTech Connect

    Jones, D.P.; Leax, T.R.

    1998-04-01

    Fatigue crack growth tests were performed on four point bend specimens with crack like defects intentionally placed in A302B low-alloy pressure vessel steel clad with 308/309L weld deposited stainless steel. The defects were placed in the base metal under the cladding by machining a cavity from the side opposite the cladding, electric-discharge machining a very sharp flaw, fatigue pre-cracking the flaw, and then filling up the cavity by a weld repair process. The specimens were stress relieved before fatigue testing. The specimens were fatigue cycled at positive load ratios until the defects broke through to the surface. The specimens were then fractured at liquid nitrogen temperatures to reveal the fracture surfaces. Seven different sub-clad flaw specimens were tested in room temperature air and each test provides a record of cycles to defect break-through. Changes in defect size and shape as a function of applied load cycles were obtained by benchmarking the crack at various stages of the load history. The results provide a set of embedded defect data which can be used for qualifying fatigue crack growth analysis procedures such as those in Section XI of the ASME Boiler and Pressure Vessel Code. A comparison between calculated and measured values shows that the ASME B and PV Section XI fatigue crack growth procedures conservatively predict cycles to defect break-through for small sub-clad defects.

  12. Eddy Current Method for Fatigue Testing

    NASA Technical Reports Server (NTRS)

    Simpson, John W. (Inventor); Fulton, James P. (Inventor); Wincheski, Russell A. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor); Nath, Shridhar C. (Inventor)

    1997-01-01

    Flux-focusing electromagnetic sensor using a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. A ferrous shield isolates a high-turn pick-up coil from an excitation coil. Use of the magnetic shield produces a null voltage output across the receiving coil in presence of an unflawed sample. Redistribution of the current flow in the sample caused by the presence of flaws. eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. Maximum sensor output is obtained when positioned symmetrically above the crack. By obtaining position of maximum sensor output, it is possible to track the fault and locate the area surrounding its tip. Accuracy of tip location is enhanced by two unique features of the sensor; a very high signal-to-noise ratio of the probe's output resulting in an extremely smooth signal peak across the fault, and a rapidly decaying sensor output outside a small area surrounding the crack tip enabling the search region to be clearly defined. Under low frequency operation, material thinning due to corrosion causes incomplete shielding of the pick-up coil. Low frequency output voltage of the probe is therefore a direct indicator of thickness of the test sample. Fatigue testing a conductive material is accomplished by applying load to the material, applying current to the sensor, scanning the material with the sensor, monitoring the sensor output signal, adjusting material load based on the sensor output signal of the sensor, and adjusting position of the sensor based on its output signal.

  13. Fatigue crack growth automated testing method

    SciTech Connect

    Hatch, P.W.; VanDenAvyle, J.A.; Laing, J.

    1989-06-01

    A computer controlled servo-hydraulic mechanical test system has been configured to conduct automated fatigue crack growth testing. This provides two major benefits: it allows continuous cycling of specimens without operator attention over evenings and weekends; and complex load histories, including random loading and spectrum loading, can be applied to the specimens to simulate cyclic loading of engineering structures. The software is written in MTS Multi-User Basic to control test machine output and acquire data at predetermined intervals. Compact tension specimens are cycled according to ASTM specification E647-86. Fatigue crack growth is measured via specimen compliance during the test using a compliance/crack length calibration determined earlier by visual crack length measurements. This setup was used to measure crack growth rates in 6063 aluminum alloy for a variety of cyclic loadings, including spectrum loads. Data collected compared well with tests run manually. 13 figs.

  14. Spectrum fatigue testing of T-shaped tension clips

    NASA Astrophysics Data System (ADS)

    Palmberg, Bjoern; Wallstenius, Bengt

    1992-12-01

    An investigation of strain distributions during static loading and crack propagation and fatigue lives under spectrum loading of T-shaped tension clips was carried out. Three slightly different, with respect to geometry, T shaped tension clips made of aluminum alloy 7010-T73651 were studied. The type 1 and 4 test specimens were different only with respect to the web thickness of the clamping end. The type 1 and 2 test specimens were different with repect to milled flat circular countersink around the holes in the type 2 specimens and with respect to the radius between the web and foot. The spectrum fatigue loading consisted of a load sequence representative for the wing root, lower side, of a fighter aircraft. Tests were made at two different load levels for each specimen type. The strain measurements show that the countersink in the type 2 specimens increases the stresses in the fatigue critical region. This is also manifested in the spectrum fatigue life results, where type 2 specimens show the shortest fatigue lives. The strain measurements show that the torque used for the bolts in joining two test specimens or one test specimen and a dummy has a rather large impact on the strain in the fatigue region. The strains decrease with increasing torque. The spectrum fatigue loading resulted in approximately an equal number of flights to obtain a 10.0 mm crack for specimens of type 1 and 4. This suggests that the type 1 configuration is superior since the web thickness is smaller for this type as compared to the type 4 specimens. In other words, the type 4 specimens have an unnecessary oversize of the clamping end web thickness.

  15. Comparing Rotary Bend Wire Fatigue Test Methods at Different Test Speeds

    NASA Astrophysics Data System (ADS)

    Weaver, Jason D.; Gutierrez, Erick J.

    2015-12-01

    Given its relatively simple setup and ability to produce results quickly, rotary bend fatigue testing is becoming commonplace in the medical device industry and is the subject of a new standard test method ASTM E2948-14. Although some research has been conducted to determine if results differ for different rotary bend fatigue test setups or test speeds, these parameters have not been extensively studied together. In this work, we investigate the effects of these two parameters on the fatigue life of three commonly used medical device alloys (ASTM F2063 nitinol, ASTM F138 stainless steel, and ASTM F1058 cobalt chromium). Results with three different rotary bend fatigue test setups revealed no difference in fatigue life among those setups. Increasing test speed, however, between 100 and 35,000 RPM led to an increased fatigue life for all three alloys studied (average number of cycles to fracture increased between 2.0 and 5.1 times between slowest and fastest test speed). Supplemental uniaxial tension tests of stainless steel wire at varying strain rates showed a strain rate dependence in the mechanical response which could in part explain the increased fatigue life at faster test speeds. How exactly strain rate dependence might affect the fatigue properties of different alloys at different alternating strain values requires further study. Given the difference in loading rates between benchtop fatigue tests and in vivo deformations, the potential for strain rate dependence should be considered when designing durability tests for medical devices and in extrapolating results of those tests to in vivo performance.

  16. Hybrid bearing technology for advanced turbomachinery: Rolling contact fatigue testing

    SciTech Connect

    Dill, J.F.

    1996-01-01

    The purpose of this paper is to describe the basic structure and results to date of a major ARPA funded effort to provide a tribological performance database on ceramic bearing materials and their interaction with standard bearing steels. Program efforts include studies of material physical properties, machining characteristics, and tribological performance. The majority of the testing completed to date focuses on rolling contact fatigue testing of the ceramic materials, including efforts to arrive at optimum approaches to evaluating ceramic/steel hybrid combinations in rolling contact fatigue.

  17. Fatigue Testing of Wing Beam by the Resonance Method

    NASA Technical Reports Server (NTRS)

    Bleakney, William M

    1938-01-01

    Preliminary fatigue tests on two aluminum-alloy wing-beam specimens subjected to reversed axial loading are described. The motion used consists in incorporating one or two reciprocating motors in a resonance system of which the specimen is the spring element. A description is given of the reciprocating motors, and of the method of assembling and adjusting the vibrating system. The results indicate that the method is well adapted to fatigue tests of not only uniform wing beams but also wing beams with asymmetrical local reinforcements.

  18. X-43A Rudder Spindle Fatigue Life Estimate and Testing

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Dawicke, David S.; Johnston, William M.; James, Mark A.; Simonsen, Micah; Mason, Brian H.

    2005-01-01

    Fatigue life analyses were performed using a standard strain-life approach and a linear cumulative damage parameter to assess the effect of a single accidental overload on the fatigue life of the Haynes 230 nickel-base superalloy X-43A rudder spindle. Because of a limited amount of information available about the Haynes 230 material, a series of tests were conducted to replicate the overload and in-service conditions for the spindle and corroborate the analysis. Both the analytical and experimental results suggest that the spindle will survive the anticipated flight loads.

  19. Fatigue in the military: towards a fatigue detection test based on the saccadic velocity.

    PubMed

    Diaz-Piedra, Carolina; Rieiro, Héctor; Suárez, Juan; Rios-Tejada, Francisco; Catena, Andrés; Di Stasi, Leandro Luigi

    2016-09-01

    Fatigue is a major contributing factor to operational errors. Therefore, the validation of objective and sensitive indices to detect fatigue is critical to prevent accidents and catastrophes. Whereas tests based on saccadic velocity (SV) have become popular, their sensitivity in the military is not yet clear, since most research has been conducted in laboratory settings using not fully validated instruments. Field studies remain scarce, especially in extreme conditions such as real flights. Here, we investigated the effects of real, long flights on SV. We assessed five newly commissioned military helicopter pilots during their aviation training. Pilots flew Sikorsky S-76C helicopters, under instrumental flight rules, for more than 2 h (ca. 150 min). Eye movements were recorded before and after the flight with an eye tracker using a standard guided-saccade task. We also collected subjective ratings of fatigue. SV significantly decreased from the Pre-Flight to the Post-Flight session in all pilots by around 3% (range: 1-4%). Subjective ratings showed the same tendency. We provide conclusive evidence about the high sensitivity of fatigue tests based on SV in real flight conditions, even in small samples. This result might offer military medical departments a valid and useful biomarker of warfighter physiological state. PMID:27531394

  20. Rolling-Element Fatigue Testing and Data Analysis - A Tutorial

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Zaretsky, Erwin V.

    2011-01-01

    In order to rank bearing materials, lubricants and other design variables using rolling-element bench type fatigue testing of bearing components and full-scale rolling-element bearing tests, the investigator needs to be cognizant of the variables that affect rolling-element fatigue life and be able to maintain and control them within an acceptable experimental tolerance. Once these variables are controlled, the number of tests and the test conditions must be specified to assure reasonable statistical certainty of the final results. There is a reasonable correlation between the results from elemental test rigs with those results obtained with full-scale bearings. Using the statistical methods of W. Weibull and L. Johnson, the minimum number of tests required can be determined. This paper brings together and discusses the technical aspects of rolling-element fatigue testing and data analysis as well as making recommendations to assure quality and reliable testing of rolling-element specimens and full-scale rolling-element bearings.

  1. Estimation of the minimum number of test specimens for fatigue testing of acrylic bone cement.

    PubMed

    Lewis, Gladius; Sadhasivini, Anupama

    2004-08-01

    In the literature on fatigue testing of acrylic bone cements, data sets of various sizes have been used in different test series for the same cement formulation. There are two important consequences of this situation. First, it means that some test series last much longer than others, with all the implications for the cost of testing. Second, it makes drawing conclusions about the fatigue performance of a cement, based on the results of different literature series, a problematic issue. Clearly then, a recommendation as to what should be the minimum number of test specimens to use that would allow for confidence in the results of the statistical treatment of the test results (Gmin) would be desirable. In the present work, a method that could be used to culminate in such a recommendation is described. This method involves (i) obtaining experimental fatigue test results and (ii) analyzing those results using the Weibull probability distribution function and other statistical methods. This methodology is illustrated using fatigue life results obtained from uniaxial tension-compression fatigue tests on specimens fabricated from the polymerizing dough of one commercially available acrylic bone cement. For a tolerable error of 5%, we estimated Gmin to be either 7 (if the fatigue life results are treated using the two-parameter Weibull distribution function) or 11 (if the fatigue life results are treated using the three-parameter Weibull distribution function). To be on the conservative side, we therefore recommend that Gmin be 11. Three key limitations of the methodology presented here are discussed. PMID:15046933

  2. Designing of a Testing Machine for Shear-Mode Fatigue Crack Growth

    NASA Astrophysics Data System (ADS)

    Kusaba, A.; Okazaki, S.; Endo, M.; Yanase, K.

    As recognized, flaking-type failure is one of the serious problems for railroad tracks and bearings. In essence, flaking-type failure is closely related to the growth of the shear-mode (Mode-II and Mode-III) fatigue crack. In our research group, it is demonstrated that a shear-mode fatigue crack can be reproduced for cylindrical specimens by applying the cyclic torsion in the presence of the static axial compressive stress. However, a biaxial servo-hydraulic fatigue testing machine is quite expensive to purchase and costly to maintain. The low testing speed (about 10Hz) of the testing machine further aggravates the situation. As a result, study on shear-mode fatigue crack growth is still in the nascent stage. To overcome the difficulties mentioned above, in this research activity, we developed a high-performance and cost-effective testing machine to reproduce the shear-mode fatigue crack growth by improving the available resonance-type torsion fatigue testing machine. The primary advantage of using the resonance-type torsion fatigue testing machine is cost-efficiency. In addition, the testing speed effectively can be improved, in comparison with that of a biaxial servo-hydraulic fatigue testing machine. By utilizing the newly-designed testing machine, we have demonstrated that we can successfully reproduce the shear-mode fatigue crack.

  3. Design features and results from fatigue reliability research machines.

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Kececioglu, D.; Mcconnell, J. B.

    1971-01-01

    The design, fabrication, development, operation, calibration and results from reversed bending combined with steady torque fatigue research machines are presented. Fifteen-centimeter long, notched, SAE 4340 steel specimens are subjected to various combinations of these stresses and cycled to failure. Failure occurs when the crack in the notch passes through the specimen automatically shutting down the test machine. These cycles-to-failure data are statistically analyzed to develop a probabilistic S-N diagram. These diagrams have many uses; a rotating component design example given in the literature shows that minimum size and weight for a specified number of cycles and reliability can be calculated using these diagrams.

  4. Rolling contact fatigue testing of thermally sprayed coatings

    SciTech Connect

    Maekelae, A.; Vuoristo, P.; Lahdensuo, M.; Niemi, K.; Maentylae, T.

    1994-12-31

    Two Rolling Contact Fatigue (RCF) test systems have been developed in order to compare coatings according to their service lives under high-load rolling contact. Experimental testing facilities of the three-roller and the two-roller type RCF test equipment are presented and problems involved with testing of thermally sprayed coatings are discussed. The aim of this three-year-project is to study reasons for development of coating micropitting and delamination of high-velocity oxyfuel (HVOF) and detonation gun sprayed coatings. Some observations of rolling contact fatigue behavior of detonation gun sprayed WC+12% Co coating subjected to a nearly pure rolling line contact at cyclic Hertzian stress level of approximately 410 MPa are made, but interpreting the results requires still more work.

  5. Multi-axial fatigue testing machine

    SciTech Connect

    Sallberg, D.W.; Lawson, T.J.; Cardon, M.H.

    1989-02-07

    A testing machine is described for multi-axis fatigue testing of a component having inner and outer elements subject to linear and rotational forces about different axes comprising a base, first, second and third hydraulic actuators secured to the base, hydraulic pressure means and control means coupled to the actuators for controlled operation of the actuators, gimbal means comprising first and second gimbals mounted on the base and interconnected for rotation about mutually perpendicular axes, the first gimbal having means for attachment to one of the elements, means for substantially independently coupling the first and second actuators to the first and second gimbals respectively so that each actuator effects rocking movement of one gimbal without inputting torque about the axis of the other gimbal, and means for attaching the third actuator to the other of the elements, whereby the three actuators independently and controllably apply loads to the component about three axes of motion.

  6. Rolling element fatigue testing of gear materials

    NASA Technical Reports Server (NTRS)

    Nahm, A. H.

    1978-01-01

    Rolling element fatigue lives of eleven alloys were evaluated. The eleven alloys studied were three nitriding alloys (Super Nitralloy, Nitralloy 135, and Nitralloy N), four case carburizing alloys (AISI 9310, CBS 600, CBS 1000M and Vasco X-2), and four throughhardening alloys (Vasco Matrix II,AISI W-1, AISI S-2 and AISI O-2). Several different heat treatments and/or melting processes were studied on the three carburizing alloy steels. Metallurgical analyses were made before and after the RC rig tests. Test data were statistically analyzed using the Weibull distribution function. B-10 lives were compared versus VIM-VAR AISI M-50 and carburized VAR AISI 9310, as reference alloys.

  7. Bending fatigue tests on SiC-Al tapes under alternating stress at room temperature

    NASA Technical Reports Server (NTRS)

    Herzog, J. A.

    1981-01-01

    The development of a testing method for fatigue tests on SiC-Al tapes containing a small amount of SiC filaments under alternating stress is reported. The fatigue strength curves resulting for this composite are discussed. They permit an estimate of its behavior under continuous stress and in combination with various other matrices, especially metal matrices.

  8. Novel dynamic fatigue-testing device: design and measurements

    NASA Astrophysics Data System (ADS)

    Foong, Chee-Hoe; Wiercigroch, Marian; Deans, William F.

    2006-08-01

    The influence of dynamics on a propagating fatigue crack has not been studied experimentally yet mainly due to quasi-static loading from traditional fatigue-testing machines. To overcome this serious drawback, a novel base-excited fatigue-testing device was designed and built to allow measurement of the dynamic responses of a single-edge-notch beam (SENB) under a growing fatigue crack. In this paper, the details of the novel test rig including initial development, modification and instrumentation are given. The experimental time histories obtained for harmonic and chaotic excitations have shown that the fatigue rig is capable of generating a wide range of loading patterns. Moreover, the experimental crack growth curves and features of the fracture surface have confirmed that the rig is capable of inducing proper fatigue cracks.

  9. Evaluation of composite flattened tubular specimen. [fatigue tests

    NASA Technical Reports Server (NTRS)

    Liber, T.; Daniel, I. M.

    1978-01-01

    Flattened tubular specimens of graphite/epoxy, S-glass/epoxy, Kevlar-49/epoxy, and graphite/S-glass/epoxy hybrid materials were evaluated under static and cyclic uniaxial tensile loading and compared directly with flat coupon data of the same materials generated under corresponding loading conditions. Additional development for the refinement of the flattened specimen configuration and fabrication was required. Statically tested graphite/epoxy, S-glass/epoxy, and Kevlar 49/epoxy flattened tube specimens exhibit somewhat higher average strengths than their corresponding flat coupons. Flattened tube specimens of the graphite/S-glass/epoxy hybrid and the graphite/epoxy flattened tube specimens failed in parasitic modes with consequential lower strength than the corresponding flat coupons. Fatigue tested flattened tube specimens failed in parasitic modes resulting in lower fatigue strengths than the corresponding flat coupons.

  10. Reversible Bending Fatigue Testing on Zry-4 Surrogate Rods

    SciTech Connect

    Wang, Jy-An John; Wang, Hong; Bevard, Bruce Balkcom; Howard, Rob L

    2014-01-01

    Testing high-burnup spent nuclear fuel (SNF) presents many challenges in areas such as specimen preparation, specimen installation, mechanical loading, load control, measurements, data acquisition, and specimen disposal because these tasks are complicated by the radioactivity of the test specimens. Research and comparison studies conducted at Oak Ridge National Laboratory (ORNL) resulted in a new concept in 2010 for a U-frame testing setup on which to perform hot-cell reversible bending fatigue testing. Subsequently, the three-dimensional finite element analysis and the engineering design of components were completed. In 2013 the ORNL team finalized the upgrade of the U-frame testing setup and the integration of the U-frame setup into a Bose dual linear motor test bench to develop a cyclic integrated reversible-bending fatigue tester (CIRFT). A final check was conducted on the CIRFT test system in August 2013, and the CIRFT was installed in the hot cell in September 2013 to evaluate both the static and dynamic mechanical response of SNF rods under simulated loads. The fatigue responses of Zircaloy-4 (Zry-4) cladding and the role of pellet pellet and pellet clad interactions are critical to SNF vibration integrity, but such data are not available due to the unavailability of an effective testing system. While the deployment of the developed CIRFT test system in a hot cell will provide the opportunity to generate the data, the use of a surrogate rod has proven quite effective in identifying the underlying deformation mechanism of an SNF composite rod under an equivalent loading condition. This paper presents the experimental results of using surrogate rods under CIRFT reversible cyclic loading. Specifically, monotonic and cyclic bending tests were conducted on surrogate rods made of a Zry-4 tube and alumina pellet inserts, both with and without an epoxy bond.

  11. Metal Matrix Composites: Fatigue and Fracture Testing. (Latest citations from the Aerospace Database)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The bibliography contains citations concerning techniques and results of testing metal matrix composites for fatigue and fracture. Methods include non-destructive testing techniques, and static and cyclic techniques for assessing compression, tensile, bending, and impact characteristics.

  12. High frequency fatigue testing of Udimet 700 at 1400 F

    NASA Technical Reports Server (NTRS)

    Conn, A. F.; Rudy, S. L.

    1972-01-01

    An investigation pertaining to the development of life prediction methods for materials subjected to high temperature creep/fatigue conditions is presented. High frequency (13.4 kHz) fatigue data were measured at 1400 F on specimens of the nickel-based alloy Udimet 700. Tests were conducted on the virgin material, as well as on specimens which had received prior exposures to high temperature, fatigue, and creep.

  13. Fatigue test of RC beams strengthened with prestressed CFLs

    NASA Astrophysics Data System (ADS)

    Guo, Xinyan; Huang, Peiyan; Liu, Guangwan; Xie, Jianhe

    2008-11-01

    Applying prestress to fiber reinforced polymer (FRP) can be used more efficiently since a greater portion energy of its tensile capacity is engaged. Based on carbon fiber laminate (CFL), fatigue tests are made to find out the fatigue behavior of reinforced concrete (RC) beams strengthened with prestressed CFL. The interfacial debonding is a main failure mode for RC beams strengthened with prestressed CFLs under the cyclic loading. Furthermore, it has been found that the stress value of CFLs decide whether the additional prestressing has a negative or positive effect on the fatigue behavior of the strengthened beam, and the excessive prestressing would reduce the fatigue life of the strengthened beam.

  14. Rolling element fatigue testing of gear materials

    NASA Technical Reports Server (NTRS)

    Nahm, A. H.

    1978-01-01

    Rolling element fatigue lives of nine alloys were evaluated in Rolling Contact (RC) rigs. Test conditions included a Hertzian stress at 4,826 MPa (700 ksi), a rolling speed of 6.23 m/sec (245 in/sec.). Tests were run with a Type I oil (MIL-L-7808G) at room temperature. B-10 lives (10% failure rate) of alloys were compared versus reference alloys, VIM-VAR AISI M-50 and VAR AISI 9310. Six case carburizing alloys (AISI 9310, CBS600, CBS1000M, EX00014, Vasco X-2 and EX00053) and three through-hardening alloys (AISI M-50, VascoMax 350 and Vasco Matrix 2 evaluated, showed RCF performance inferior or equivalent to that of AISI 9310 and AISI M-50. It was also found that the effects of vacuum melting processes, different tempering temperatures, freezing cycle during heat treating, shot peening, gold plating and chrome plating employed in the present investigation did not significantly affect RCF life.

  15. Transverse Tension Fatigue Life Characterization Through Flexure Testing of Composite Materials

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Chawan, Arun D.; Krueger, Ronald; Paris, Isabelle

    2001-01-01

    The transverse tension fatigue life of S2/8552 glass-epoxy and IM7/8552 carbon-epoxy was characterized using flexure tests of 90-degree laminates loaded in 3-point and 4-point bending. The influence of specimen polishing and specimen configuration on transverse tension fatigue life was examined using the glass-epoxy laminates. Results showed that 90-degree bend specimens with polished machined edges and polished tension-side surfaces, where bending failures where observed, had lower fatigue lives than unpolished specimens when cyclically loaded at equal stress levels. The influence of specimen thickness and the utility of a Weibull scaling law was examined using the carbon-epoxy laminates. The influence of test frequency on fatigue results was also documented for the 4-point bending configuration. A Weibull scaling law was used to predict the 4-point bending fatigue lives from the 3-point bending curve fit and vice-versa. Scaling was performed based on maximum cyclic stress level as well as fatigue life. The scaling laws based on stress level shifted the curve fit S-N characterizations in the desired direction, however, the magnitude of the shift was not adequate to accurately predict the fatigue lives. Furthermore, the scaling law based on fatigue life shifted the curve fit S-N characterizations in the opposite direction from measured values. Therefore, these scaling laws were not adequate for obtaining accurate predictions of the transverse tension fatigue lives.

  16. Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Choi, Sung R.; Miller, Robert A.

    2004-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

  17. Accelerated Fatigue Testing of Stent-Like Diamond Specimens

    NASA Astrophysics Data System (ADS)

    Zipse, A.; Schlun, M.; Dreher, G.; Zum Gahr, J.; Rebelo, N.

    2011-07-01

    In this study, we investigated the fatigue behavior of stent-like diamond specimens with particular attention paid to the nature of the test specimen, the constitutive model for the finite element analyses and the displacement condition. A newly designed test rig did enhance the investigation and results with respect to the simulation of the expected in vivo displacement conditions. The excellent performance of the new test method presented within our study provides a good basis for future tests without risk of compromised results due to differing characteristics between test specimens and finished stents, inappropriate displacement conditions or constitutive material model and provides a high reliability and applicability of the results to actual stents.

  18. Effect of Preloading on Fatigue Strength in Dynamic Fatigue Testing of Ceramic Materials at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1995-01-01

    Previously derived solutions of fatigue strength as a function of preloading were verified by applying preloads to elevated temperature dynamic fatigue tests of 96 wt% alumina at 1000 C and NC 132 silicon nitride at 1100 C. The technique was found very useful in identification and control of the governing failure mechanism when multiple failure mechanisms, such as slow crack growth, creep and oxidation occurred simultaneously at elevated temperatures.

  19. Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

    2008-01-01

    Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

  20. Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

    2012-01-01

    Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

  1. Hydraulic servo system increases accuracy in fatigue testing

    NASA Technical Reports Server (NTRS)

    Dixon, G. V.; Kibler, K. S.

    1967-01-01

    Hydraulic servo system increases accuracy in applying fatigue loading to a specimen under test. An error sensing electronic control loop, coupled to the hydraulic proportional closed loop cyclic force generator, provides an accurately controlled peak force to the specimen.

  2. Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 °C

    NASA Astrophysics Data System (ADS)

    Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L., III; Busby, Jeremy T.; Mo, Kun; Stubbins, James F.

    2013-01-01

    Creep-fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep-fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep-fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep-fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep-fatigue life. The linear damage summation could predict the creep-fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep-fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep-fatigue life prediction results for both materials.

  3. Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

    SciTech Connect

    Chen, Xiang; Sokolov, Mikhail A; Sham, Sam; ERDMAN III, DONALD L; Busby, Jeremy T; Mo, Kun; Stubbins, James

    2013-01-01

    Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.

  4. Comments on the origin of acoustic emission in fatigue testing of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Heiple, C. R.; Carpenter, S. H.; Armentrout, D. L.

    The size of acoustic emission (AE) signals expected from inclusion fracture during fatigue testing of 7075 aluminum has been estimated on the basis of previous measurements of AE produced by the fracture of boron particles incorporated into 2219 aluminum. The AF signal size expected from deformation in the plastic zone ahead of the fatigue crack was estimated from the results of tensile tests on 7075 aluminum. The signals predicted from both processes are near or below the noise level in the fatigue experiments and are therefore far too small to account for the signals actually observed. Nearly simultaneous fracture of multiple inclusions could produce signals as large as those observed in fatigue tests of 7075 aluminum, however, fatigue tests of 7050 aluminum produced signals as large or larger than in 7075. Since 7050 has substantially fewer inclusions than 7075, the simultaneous failure of multiple inclusions is unlikely to be a major AE source in fatigue testing of either aluminum alloy. Thus, the most probable source of acoustic emission during fatigue testing of 7075 and 7050 aluminum is the crack advance itself. The measured crack advance per cycle is large enough to release sufficient elastic energy to account for the AE signals observed.

  5. 1000-ton testing machine for cyclic fatigue tests of materials at liquid nitrogen temperatures

    NASA Astrophysics Data System (ADS)

    Khitruk, A. A.; Klimchenko, Yu. A.; Kovalchuk, O. A.; Marushin, E. L.; Mednikov, A. A.; Nasluzov, S. N.; Privalova, E. K.; Rodin, I. Yu.; Stepanov, D. B.; Sukhanova, M. V.

    2014-01-01

    One of the main tasks of superconductive magnets R&D is to determine the mechanical and fatigue properties of structural materials and the critical design elements in the cryogenic temperature range. This paper describes a new facility built based on the industrial 1000-ton (10 MN) testing machine Schenk PC10.0S. Special equipment was developed to provide the mechanical and cyclic tensile fatigue tests of large-scale samples at the liquid nitrogen temperature and in a given load range. The main feature of the developed testing machine is the cryostat, in which the device converting a standard compression force of the testing machine to the tensile force affected at the test object is placed. The control system provides the remote control of the test and obtaining, processing and presentation of test data. As an example of the testing machine operation the test program and test results of the cyclic tensile fatigue tests of fullscale helium inlet sample of the PF1 coil ITER are presented.

  6. 1000–ton testing machine for cyclic fatigue tests of materials at liquid nitrogen temperatures

    SciTech Connect

    Khitruk, A. A.; Klimchenko, Yu. A.; Kovalchuk, O. A.; Marushin, E. L.; Mednikov, A. A.; Nasluzov, S. N.; Privalova, E. K.; Rodin, I. Yu.; Stepanov, D. B.; Sukhanova, M. V.

    2014-01-29

    One of the main tasks of superconductive magnets R and D is to determine the mechanical and fatigue properties of structural materials and the critical design elements in the cryogenic temperature range. This paper describes a new facility built based on the industrial 1000-ton (10 MN) testing machine Schenk PC10.0S. Special equipment was developed to provide the mechanical and cyclic tensile fatigue tests of large-scale samples at the liquid nitrogen temperature and in a given load range. The main feature of the developed testing machine is the cryostat, in which the device converting a standard compression force of the testing machine to the tensile force affected at the test object is placed. The control system provides the remote control of the test and obtaining, processing and presentation of test data. As an example of the testing machine operation the test program and test results of the cyclic tensile fatigue tests of fullscale helium inlet sample of the PF1 coil ITER are presented.

  7. Low-cycle fatigue testing methods

    NASA Technical Reports Server (NTRS)

    Lieurade, H. P.

    1978-01-01

    The good design of highly stressed mechanical components requires accurate knowledge of the service behavior of materials. The main methods for solving the problems of designers are: determination of the mechanical properties of the material after cyclic stabilization; plotting of resistance to plastic deformation curves; effect of temperature on the life on low cycle fatigue; and simulation of notched parts behavior.

  8. Fatigue Crack Growth Threshold Testing of Metallic Rotorcraft Materials

    NASA Technical Reports Server (NTRS)

    Newman, John A.; James, Mark A.; Johnson, William M.; Le, Dy D.

    2008-01-01

    Results are presented for a program to determine the near-threshold fatigue crack growth behavior appropriate for metallic rotorcraft alloys. Four alloys, all commonly used in the manufacture of rotorcraft, were selected for study: Aluminum alloy 7050, 4340 steel, AZ91E Magnesium, and Titanium alloy Ti-6Al-4V (beta-STOA). The Federal Aviation Administration (FAA) sponsored this research to advance efforts to incorporate damage tolerance design and analysis as requirements for rotorcraft certification. Rotorcraft components are subjected to high cycle fatigue and are typically subjected to higher stresses and more stress cycles per flight hour than fixed-wing aircraft components. Fatigue lives of rotorcraft components are generally spent initiating small fatigue cracks that propagate slowly under near-threshold cracktip loading conditions. For these components, the fatigue life is very sensitive to the near-threshold characteristics of the material.

  9. An Axial-Torsional, Thermomechanical Fatigue Testing Technique

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Bonacuse, Peter J.

    1995-01-01

    A technique for conducting strain-controlled, thermomechanical, axial-torsional fatigue tests on thin-walled tubular specimens was developed. Three waveforms of loading, namely, the axial strain waveform, the engineering shear strain waveform, and the temperature waveform were required in these tests. The phasing relationships between the mechanical strain waveforms and the temperature and axial strain waveforms were used to define a set of four axial-torsional, thermomechanical fatigue (AT-TMF) tests. Real-time test control (3 channels) and data acquisition (a minimum of 7 channels) were performed with a software program written in C language and executed on a personal computer. The AT-TMF testing technique was used to investigate the axial-torsional thermomechanical fatigue behavior of a cobalt-base superalloy, Haynes 188. The maximum and minimum temperatures selected for the AT-TMF tests were 760 and 316 C, respectively. Details of the testing system, calibration of the dynamic temperature profile of the thin-walled tubular specimen, thermal strain compensation technique, and test control and data acquisition schemes, are reported. The isothermal, axial, torsional, and in- and out-of-phase axial-torsional fatigue behaviors of Haynes 188 at 316 and 760 C were characterized in previous investigations. The cyclic deformation and fatigue behaviors of Haynes 188 in AT-TMF tests are compared to the previously reported isothermal axial-torsional behavior of this superalloy at the maximum and minimum temperatures.

  10. Elevated temperature fatigue testing of metals

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.

    1981-01-01

    The major technology areas needed to perform a life prediction of an aircraft turbine engine hot section component are discussed and the steps required for life prediction are outlined. These include the determination of the operating environment, the calculation of the thermal and mechanical loading of the component, the cyclic stress-strain and creep behavior of the material required for structural analysis, and the structural analysis to determine the local stress-strain-temperature-time response of the material at the critical location in the components. From a knowledge of the fatigue, creep, and failure resistance of the material, a prediction of the life of the component is made. Material characterization and evaluation conducted for the purpose of calculating fatigue crack initiation lives of components operating at elevated temperatures are emphasized.

  11. Improved Flat Specimens For Tensile And Fatigue Testing Of Composites

    NASA Technical Reports Server (NTRS)

    Worthem, Dennis W.

    1994-01-01

    Improved shape proposed for flat, reduced-gauge-section specimens for tensile and fatigue testing of advanced composite materials at ambient and high temperatures. Typical specimen consists of flat bar 15.2 centimeters long, 1.27 centimeters wide, and 0.318 centimeters thick, with full-width tab regions at ends, 3.81-centimeters-long gauge section of reduced width in middle, and two transition regions where width tapers between tab and gauge widths along 6.35-centimeters-radius circular arc tangent to edge of gauge section. Specimen gripped by squeezing between tabs in tab regions, and tensile test load applied via tab grips. Configuration reduces undesired concentrations of stresses in transition and tab regions, forcing tensile failure to occur in gauge section and ensuring more-consistent results in tensile tests.

  12. Isometric knee extensor fatigue following a Wingate test: peripheral and central mechanisms.

    PubMed

    Fernandez-del-Olmo, M; Rodriguez, F A; Marquez, G; Iglesias, X; Marina, M; Benitez, A; Vallejo, L; Acero, R M

    2013-02-01

    Central and peripheral fatigue have been explored during and after running or cycling exercises. However, the fatigue mechanisms associated with a short maximal cycling exercise (30 s Wingate test) have not been investigated. In this study, 10 volunteer subjects performed several isometric voluntary contractions using the leg muscle extensors before and after two bouts of cycling at 25% of maximal power output and two bouts of Wingate tests. Transcranial magnetic stimulation (TMS) and electrical motor nerve stimulation (NM) were applied at rest and during the voluntary contractions. Maximal voluntary contraction (MVC), voluntary activation (VA), twitch amplitude evoked by electrical nerve stimulation, M wave and motor potential evoked by TMS (MEP) were recorded. MVC, VA and twitch amplitude evoked at rest by NM decreased significantly after the first and second Wingate tests, indicating central and peripheral fatigue. MVC and VA, but not the twitch amplitude evoked by NM, recovered before the second Wingate test. These results suggest that the Wingate test results in a decrease in MVC associated with peripheral and central fatigue. While the peripheral fatigue is associated with an intramuscular impairment, the central fatigue seems to be the main reason for the Wingate test-induced impairment of MVC. PMID:21812824

  13. Results of inphase axial-torsional fatigue experiments on 304 stainless steel

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1989-01-01

    A series of axial-torsional, inphase, strain-controlled, low-cycle fatigue tests were performed at room temperature on tubular specimens of 304 stainless steel. The program was conducted in cooperation with the task group on multiaxial fatigue research of ASTM committee E-09. The objective was to quantify the variability in multiaxial test results among several laboratories. Only included is data which was generated at the NASA Lewis Research Center's High Temperature Fatigue and Structures Laboratory. The experimental equipment and procedures used are described. The tubular specimens were polished on the outer surface to aid in the use of a cellulose film surface replication technique for crack detection. However, cracking initiated predominantly on the internal surface for all specimens. Honing of the bore of the tubular specimens lessened but did not entirely eliminate this problem. The observed fatigue lives are compared with lives calculated from three multiaxial life models. Constants for the life prediction models were obtained from uniaxial and torsional tests performed on the same heat of material. The observed fatigue lives agreed with calculated lives to within a factor of two for all but one of the life prediction models.

  14. On the use of ultrasonic fatigue testing technique--variable amplitude loadings and crack growth monitoring.

    PubMed

    Müller, T; Sander, M

    2013-12-01

    In the very high cycle fatigue regime high-frequency testing techniques are required. Using the ultrasonic fatigue technique, testing time could be reduced significantly in comparison to conventional servo-hydraulic machines. An ultrasonic fatigue testing system developed by the BOKU Vienna with load frequencies of about 20kHz is used for variable amplitude loading investigations in the VHCF regime. Therefore, the amplitude level during fatigue tests is controlled by a PC using an own developed software. Additionally, an in situ reconstruction of a damage equivalent load spectrum based on a load time history is introduced schematically. To optimize the experimental procedure a temperature-controlled pulse-pause adaption has been developed and implemented into the software. For quantifying the influence of variable amplitude loadings on the fatigue life, e.g. load interaction effects, the crack growth is measured by using the potential drop technique that is adapted to the ultrasonic fatigue testing system. Finally, the results of two-step-block loading tests are presented. PMID:23597637

  15. Failure of the human lumbar motion-segments resulting from anterior shear fatigue loading.

    PubMed

    Skrzypiec, Daniel M; Nagel, Katrin; Sellenschloh, Kay; Klein, Anke; Püschel, Klaus; Morlock, Michael M; Huber, Gerd

    2016-08-01

    An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32-42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the upper vertebra of the motion-segment, at a frequency of 5 Hz. During fatigue experiments, several failure events were observed in the dynamic creep curves. Post-test x-ray, CT and dissection revealed that all specimens had delamination of the intervertebral disc. Anterior shear fatigue predominantly resulted in fracture of the apophyseal processes of the upper vertebrae (n=4). Exposure to the anterior shear fatigue loading caused motion-segment instability and resulted in vertebral slip corresponding to grade I and 'mild' grade II spondylolisthesis, as observed clinically. PMID:26829975

  16. Failure of the human lumbar motion-segments resulting from anterior shear fatigue loading

    PubMed Central

    SKRZYPIEC, Daniel M.; NAGEL, Katrin; SELLENSCHLOH, Kay; KLEIN, Anke; PÜSCHEL, Klaus; MORLOCK, Michael M.; HUBER, Gerd

    2016-01-01

    An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32–42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the upper vertebra of the motion-segment, at a frequency of 5 Hz. During fatigue experiments, several failure events were observed in the dynamic creep curves. Post-test x-ray, CT and dissection revealed that all specimens had delamination of the intervertebral disc. Anterior shear fatigue predominantly resulted in fracture of the apophyseal processes of the upper vertebrae (n=4). Exposure to the anterior shear fatigue loading caused motion-segment instability and resulted in vertebral slip corresponding to grade I and ‘mild’ grade II spondylolisthesis, as observed clinically. PMID:26829975

  17. Cognitive and Physical Fatigue Tasks Enhance Pain, Cognitive Fatigue and Physical Fatigue in People with Fibromyalgia

    PubMed Central

    Dailey, Dana L; Keffala, Valerie J; Sluka, Kathleen A

    2014-01-01

    Objective Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task and a dual fatigue task. Methods Twenty four people with fibromyalgia and 33 healthy controls completed pain, fatigue and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue and perceived physical fatigue were assessed during each task using visual analogue scales. Function was assessed with shoulder range of motion and grip. Results People with fibromyalgia had significantly higher increases in pain, cognitive fatigue and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (p<0.01). People with fibromyalgia performed equivalently on measures of physical performance and cognitive performance on the physical and cognitive fatigue tasks, respectively. Conclusions These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. PMID:25074583

  18. Fatigue acceptance test limit criterion for larger diameter rolled thread fasteners

    SciTech Connect

    Kephart, A.R.

    1997-05-01

    This document describes a fatigue lifetime acceptance test criterion by which studs having rolled threads, larger than 1.0 inches in diameter, can be assured to meet minimum quality attributes associated with a controlled rolling process. This criterion is derived from a stress dependent, room temperature air fatigue database for test studs having a 0.625 inch diameter threads of Alloys X-750 HTH and direct aged 625. Anticipated fatigue lives of larger threads are based on thread root elastic stress concentration factors which increase with increasing thread diameters. Over the thread size range of interest, a 30% increase in notch stress is equivalent to a factor of five (5X) reduction in fatigue life. The resulting diameter dependent fatigue acceptance criterion is normalized to the aerospace rolled thread acceptance standards for a 1.0 inch diameter, 0.125 inch pitch, Unified National thread with a controlled Root radius (UNR). Testing was conducted at a stress of 50% of the minimum specified material ultimate strength, 80 Ksi, and at a stress ratio (R) of 0.10. Limited test data for fastener diameters of 1.00 to 2.25 inches are compared to the acceptance criterion. Sensitivity of fatigue life of threads to test nut geometry variables was also shown to be dependent on notch stress conditions. Bearing surface concavity of the compression nuts and thread flank contact mismatch conditions can significantly affect the fastener fatigue life. Without improved controls these conditions could potentially provide misleading acceptance data. Alternate test nut geometry features are described and implemented in the rolled thread stud specification, MIL-DTL-24789(SH), to mitigate the potential effects on fatigue acceptance data.

  19. Acceleration of fatigue tests for built-up titanium components

    NASA Technical Reports Server (NTRS)

    Watanabe, R. T.

    1976-01-01

    A study was made of the feasibility of a room-temperature scheme of accelerating fatigue tests for Mach 3 advanced supersonic transport aircraft. The test scheme used equivalent room-temperature cycles calculated for supersonic flight conditions. Verification tests were conducted using specimens representing titanium wing lower surface structure. Test-acceleration parameters were developed for the test with an auxiliary test set. Five specimens were tested with a flight-by-flight load and temperature spectrum to simulate typical Mach 3 operation. Two additional sets of five specimens were tested at room temperature to evaluate the test-acceleration scheme. The fatigue behavior of the specimens generally correlated well with the proposed correction method.

  20. Influence of laser hardening and resulting microstructure on fatigue properties of carbon steels

    SciTech Connect

    Cerny, I.; Fuerbacher, I.; Linhart, V.

    1998-06-01

    Cylindrical specimens of a CSN 12050 carbon steel, equivalent to the UNS G 10420 steel, with two different initial microstructures, normalized and heat treated, were surface processed without melting by a 2.5 kW, CO{sub 2} laser to study the effects of laser-beam hardening and resulting microstructure on fatigue properties and mechanisms. Two configurations of circumferential laser passes were made, resulting in one and three separate surface hardened lines, respectively. Fatigue resistance was studied using alternating bend tests. A detailed metallographic study and x-ray measurements of surface stresses were carried out. It was shown that the laser beam hardening under different conditions either reduced or slightly improved the fatigue life.

  1. Fatigue Testing of Abrasive Water Jet Cut Titanium

    SciTech Connect

    Hovanski, Yuri; Dahl, Michael E.; Williford, Ralph E.

    2009-06-08

    Battelle Memorial Institute as part of its U.S. Department of Energy (USDOE) Contract No. DE-AC05-76RL01830 to operate the Pacific Northwest National Laboratory (PNNL) provides technology assistance to qualifying small businesses in association with a Technology Assistance Program (TAP). Qualifying companies are eligible to receive a set quantity of labor associated with specific technical assistance. Having applied for a TAP agreement to assist with fatigue characterization of Abrasive Water Jet (AWJ) cut titanium specimens, the OMAX Corporation was awarded TAP agreement 09-02. This program was specified to cover dynamic testing and analysis of fatigue specimens cut from titanium alloy Ti-6%Al-4%V via AWJ technologies. In association with the TAP agreement, a best effort agreement was made to characterize fatigue specimens based on test conditions supplied by OMAX.

  2. DOE/MSU composite material fatigue database: Test methods, materials, and analysis

    SciTech Connect

    Mandell, J.F.; Samborsky, D.D.

    1997-12-01

    This report presents a detailed analysis of the results from fatigue studies of wind turbine blade composite materials carried out at Montana State University (MSU) over the last seven years. It is intended to be used in conjunction with the DOE/MSU composite Materials Fatigue Database. The fatigue testing of composite materials requires the adaptation of standard test methods to the particular composite structure of concern. The stranded fabric E-glass reinforcement used by many blade manufacturers has required the development of several test modifications to obtain valid test data for materials with particular reinforcement details, over the required range of tensile and compressive loadings. Additionally, a novel testing approach to high frequency (100 Hz) testing for high cycle fatigue using minicoupons has been developed and validated. The database for standard coupon tests now includes over 4,100 data points for over 110 materials systems. The report analyzes the database for trends and transitions in static and fatigue behavior with various materials parameters. Parameters explored are reinforcement fabric architecture, fiber content, content of fibers oriented in the load direction, matrix material, and loading parameters (tension, compression, and reversed loading). Significant transitions from good fatigue resistance to poor fatigue resistance are evident in the range of materials currently used in many blades. A preliminary evaluation of knockdowns for selected structural details is also presented. The high frequency database provides a significant set of data for various loading conditions in the longitudinal and transverse directions of unidirectional composites out to 10{sup 8} cycles. The results are expressed in stress and strain based Goodman Diagrams suitable for design. A discussion is provided to guide the user of the database in its application to blade design.

  3. Ion beam sputter etching of orthopedic implanted alloy MP35N and resulting effects on fatigue

    NASA Technical Reports Server (NTRS)

    Wintucky, E. G.; Christopher, M.; Bahnuik, E.; Wang, S.

    1981-01-01

    The effects of two types of argon ion sputter etched surface structures on the tensile stress fatigue properties of orthopedic implant alloy MP35N were investigated. One surface structure was a natural texture resulting from direct bombardment by 1 keV argon ions. The other structure was a pattern of square holes milled into the surface by a 1 keV argon ion beam through a Ni screen mask. The etched surfaces were subjected to tensile stress only in fatigue tests designed to simulate the cyclic load conditions experienced by the stems of artificial hip joint implants. Both types of sputter etched surface structures were found to reduce the fatigue strength below that of smooth surface MP35N.

  4. Final report on low-cycle fatigue and creep-fatigue testing of salt-filled alloy 800 specimens

    SciTech Connect

    Kaae, J L

    1982-05-01

    Uniaxial low-cycle fatigue and creep-fatigue tests have been carried out on hollow alloy 800 specimens that were either filled with air or with a molten mixture of sodium nitrate, potassium nitrate and an oxidizer. Low-cycle fatigue tests were carried out at 1200/sup 0/F and 650/sup 0/F by cycling the strain continuously between equal mangitude of tensile and compressive values at a rate of 4 x 10/sup -3/sec/sup -1/ until failure. The creep-fatigue tests were carried out at 1200/sup 0/F. The loading cycle differed from that of low-cycle fatigue testing only in the imposition of a hold at the peak compressive strain in each cycle. Cracks always initiated on the inner surface of the hollow specimen, and therefore, corrosive effects on crack propagation and initiation were controlled by the environment within the specimen cavity. In common with tests carried out earlier on steam-filled alloy 800 specimens, at 1200/sup 0/F in the presence of molten salt the heat of alloy 800 with the lower carbon content had a higher fatigue strength than the heat with the higher carbon content even though different heats were used in the two testing programs. The fatigue strength of the two heats of material in the presence of molten salt at 650/sup 0/F were about the same. Tests with air-filled specimens indicated that the presence of the molten salt degraded the fatigue life at 1200/sup 0/F but did not affect the creep fatigue life, while the presence of steam enhanced both the fatigue life and the creep-fatigue life.

  5. Surface Fatigue Tests Of M50NiL Gears And Bars

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis P.; Bamberger, Eric N.

    1994-01-01

    Report presents results of tests of steels for use in gears and bearings of advanced aircraft. Spur-gear endurance tests and rolling-element surface fatigue tests performed on gear and bar specimens of M50NiL steel processed by vacuum induction melting and vacuum arc remelting (VIM-VAR). Compares results of tests with similar tests of specimens of VIM-VAR AISI 9310 steel and of AISI 9310 steel subjected to VAR only.

  6. Fatigue testing of plasma-sprayed thermal barrier coatings, volume 2

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Nagy, A.; Popelar, C. F.

    1990-01-01

    A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

  7. Effects of Total SAT® Test Time on Performance and Fatigue. Research Notes. RN-37

    ERIC Educational Resources Information Center

    Ackerman, Phillip L.; Kanfer, Ruth; Wolman, Stacey D.

    2005-01-01

    The current study was designed to examine performance effects and fatigue effects associated with different total SAT testing times. In addition, the researchers examined personality, motivation, and other determinants of individual differences in examinee fatigue before, during, and after testing.

  8. Design of PF-1 Coil Helium Inlet and Dummy Joint Samples for Fatigue Tests at 77K

    NASA Astrophysics Data System (ADS)

    Nasluzov, S. N.; Sukhanova, M. V.; Rodin, I. Yu.; Marushin, E. L.; Mednikov, A. A.; Stepanov, D. B.; Lantsetov, A. A.; Khitruk, A. A.

    A helium inlet and dummy joint between conductors are one of the most important elements of the winding pack of the ITER PF -1 coil double pancakes. A helium inlet is used for letting liquid helium into the PF-1 coil conductor. A full-scale helium inlet sample for fatigue tests and the respective tooling were designed and manufactured. Fatigue tests of the full-scale helium inlet sample were conducted in accordance with ITER requirements testing parameters in order to check the fatigue strength of the structure. Before the fatigue tests thermo-cycling of the helium inlet in the temperature range of 77 to 293 K was conducted. Before and after the fatigue tests the leak tightness of the full-scale helium inlet sample was validated by the vacuum chamber method. A low ohm electrical joint is used to connect two NbTi «CICC» conductors of PF-1 coil into a single electrical loop. To qualify the design and technology of manufacturing of the electrical joint, a full-scale dummy joint sample was developed for fatigue tests at 77 K. The main design feature of the full-scale dummy joint sample for fatigue tests is a symmetrical model of two dummy joint samples with simultaneous loading to compensate the bending moment. Fatigue tests of the full-scale helium inlet sample at 77 K have been successfully conducted in 2013. Fatigue tests of the full-scale dummy joint sample will be conducted in 2014. This paper represents the results of calculating the stress-strain state of the symmetrical model of the full-scale dummy joint sample for fatigue tests with the prescribed loading and strain, the work on designing the symmetrical model of the dummy joint sample for fatigue tests and the test facility for conducting fatigue tests at 77 K. Also the results of the leak tightness tests and thermo-cycling of the full-scale helium inlet and the results of it fatigue tests at 77 K, are presented.

  9. Predicting Fatigue and Psychophysiological Test Performance from Speech for Safety-Critical Environments

    PubMed Central

    Baykaner, Khan Richard; Huckvale, Mark; Whiteley, Iya; Andreeva, Svetlana; Ryumin, Oleg

    2015-01-01

    Automatic systems for estimating operator fatigue have application in safety-critical environments. A system which could estimate level of fatigue from speech would have application in domains where operators engage in regular verbal communication as part of their duties. Previous studies on the prediction of fatigue from speech have been limited because of their reliance on subjective ratings and because they lack comparison to other methods for assessing fatigue. In this paper, we present an analysis of voice recordings and psychophysiological test scores collected from seven aerospace personnel during a training task in which they remained awake for 60 h. We show that voice features and test scores are affected by both the total time spent awake and the time position within each subject’s circadian cycle. However, we show that time spent awake and time-of-day information are poor predictors of the test results, while voice features can give good predictions of the psychophysiological test scores and sleep latency. Mean absolute errors of prediction are possible within about 17.5% for sleep latency and 5–12% for test scores. We discuss the implications for the use of voice as a means to monitor the effects of fatigue on cognitive performance in practical applications. PMID:26380259

  10. Predicting Fatigue and Psychophysiological Test Performance from Speech for Safety-Critical Environments.

    PubMed

    Baykaner, Khan Richard; Huckvale, Mark; Whiteley, Iya; Andreeva, Svetlana; Ryumin, Oleg

    2015-01-01

    Automatic systems for estimating operator fatigue have application in safety-critical environments. A system which could estimate level of fatigue from speech would have application in domains where operators engage in regular verbal communication as part of their duties. Previous studies on the prediction of fatigue from speech have been limited because of their reliance on subjective ratings and because they lack comparison to other methods for assessing fatigue. In this paper, we present an analysis of voice recordings and psychophysiological test scores collected from seven aerospace personnel during a training task in which they remained awake for 60 h. We show that voice features and test scores are affected by both the total time spent awake and the time position within each subject's circadian cycle. However, we show that time spent awake and time-of-day information are poor predictors of the test results, while voice features can give good predictions of the psychophysiological test scores and sleep latency. Mean absolute errors of prediction are possible within about 17.5% for sleep latency and 5-12% for test scores. We discuss the implications for the use of voice as a means to monitor the effects of fatigue on cognitive performance in practical applications. PMID:26380259

  11. Fatigue testing of corrugated and Teflon hoses

    NASA Technical Reports Server (NTRS)

    Benner, Steve M.; Swanson, Theodore D.; Costello, Frederick A.

    1990-01-01

    Single and two-phase heat transport systems for the thermal control of large space facilities require fluid lines that traverse joints and either rotate or move in some other manner. Flexible hoses are being considered as one means of traversing these joints. To test the resilience of flexible hoses to bending stress, a test assembly was constructed to determine the number of flexing cycles the hoses could withstand before losing their ability to maintain a constant pressure. Corrugated metal hoses and Teflon hoses were tested at different pressures with nitrogen gas. The metal hoses had lives ranging from 30,000 to 100,000 flexing cycles. But, even after 400,000 cycles, the Teflon hoses remained essentially intact, though some leakage in the convoluted Teflon is noted.

  12. Fatigue

    MedlinePlus

    ... chemotherapy and radiation Recovering from major surgery Anxiety, stress, or depression Staying up too late Drinking too much alcohol or too many caffeinated drinks Pregnancy One disorder that causes extreme fatigue is chronic ...

  13. Innovative vibration technique applied to polyurethane foam as a viable substitute for conventional fatigue testing

    NASA Astrophysics Data System (ADS)

    Peralta, Alexander; Just-Agosto, Frederick; Shafiq, Basir; Serrano, David

    2012-12-01

    Lifetime prediction using three-point bending (TPB) can at times be prohibitively time consuming and costly, whereas vibration testing at higher frequency may potentially save time and revenue. A vibration technique that obtains lifetimes that reasonably match those determined under flexural TPB fatigue is developed. The technique designs the specimen with a procedure based on shape optimization and finite element analysis. When the specimen is vibrated in resonance, a stress pattern that mimics the stress pattern observed under conventional TPB fatigue testing is obtained. The proposed approach was verified with polyurethane foam specimens, resulting in an average error of 4.5% when compared with TPB.

  14. The detection of fatigue cracks by nondestructive testing methods

    NASA Technical Reports Server (NTRS)

    Rummel, W. D.; Todd, P. H., Jr.; Frecska, S. A.; Rathke, R. A.

    1974-01-01

    X-radiographic penetrant, ultrasonic, eddy current, holographic, and acoustic emission techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens. One hundred eighteen specimens containing a total of 328 fatigue cracks were evaluated. The cracks ranged in length from 0.500 inch (1.27 cm) to 0.007 inch (0.018 cm) and in depth from 0.178 inch (0.451 cm) and 0.001 inch (0.003 cm). Specimen thicknesses were nominally 0.060 inch (0.152 cm) and 0.210 inch (0.532 cm) and surface finishes were nominally 32 and 125 rms and 64 and 200 rms respectively. Specimens were evaluated in the as-milled surface condition, in the chemically milled surface condition and, after proof loading, in a randomized inspection sequence. Results of the nondestructive test (NDT) evaluations were compared with actual crack size obtained by measurement of the fractured specimens. Inspection data was then analyzed to provide a statistical basis for determinating the threshold crack detection sensitivity (the largest crack size that would be missed) for each of the inspection techniques at a 95% probability and 95% confidence level.

  15. Power wheelchair range testing and energy consumption during fatigue testing.

    PubMed

    Cooper, R A; VanSickle, D P; Albright, S J; Stewart, K J; Flannery, M; Robertson, R N

    1995-10-01

    The range of a power wheelchair depends on many factors including: battery type, battery state, wheelchair/rider weight, terrain, the efficiency of the drive train, and driving behavior. The purpose of this study was to evaluate the feasibility of three methods of estimating power wheelchair range. Another significant purpose was to compare the current draw on pavement to current draw on an International Standards Organization (ISO) Double Drum tester at one m/sec. Tests were performed on seven different power wheelchairs unloaded, and loaded with an ISO 100 kg test dummy. Each chair was configured according to the manufacturer's specifications, and tires were properly inflated. Experienced test technicians were used for the tennis court tests, and treadmill tests. An ISO 100 kg test dummy was used for the ISO Double Drum test. Energy consumption was measured over a distance of 1500 m for each of the three test conditions. The rolling surface was level in all cases. Repeated measure analysis of variance (ANOVA) revealed a significant difference (p = 0.0001) between the predicted range at maximum speed for the three tests. Post hoc analysis demonstrated a significant difference (p < 0.01) in estimated range at maximum speed between the Double Drum test and the treadmill test, as well as between the Double Drum test and the tennis court test. Our results indicate no significant difference (p > 0.05) between the predicted range at maximal speed between the treadmill and tennis court tests. A simple relationship does not exist between the results of range testing with the Double Drum tester and the tennis court. An alternative would be to permit the use of a treadmill for range testing as simple relationships between all pertinent treadmill and tennis court range data were found. For the Double Drum tester used, the current demand is higher than under normal usage. This presents a problem as current is related to load torque in a power wheelchair. Hence, the Double

  16. GIRAFFE test results summary

    SciTech Connect

    Yokobori, S.; Arai, K.; Oikawa, H.

    1996-03-01

    A passive system can provide engineered safety features enhancing safety system reliability and plant simplicity. Toshiba has conducted the test Program to demonstrate the feasibility of the SBWR passive safety system using a full-height, integral system test facility GIRAFFE. The test facility GIRAFFE models the SBWR in full height to correctly present the gravity driving head forces with a 1/400 volume scale. The GIRAFFE test Program includes the certification tests of the passive containment cooling system (PCCS) to remove the post-accident decay heat and the gravity driven cooling system (GDCS) to replenish the reactor coolant inventory during a LOCA. The test results have confirmed the PCCS and GDCS design and in addition, have demonstrated the operation of the pCCS with the presence of a lighter-than-steam noncondensable as well as with the presence of a heavier-than-steam, noncondensable. The GIRAFFE test Program has also provided the database to qualify a best estimate thermal-hydraulic computer code TRAC. The post test analysis results have shown that TRAC can accurately predict the PCCS heat removal Performance and the containment pressure response to a LOCA. This paper summarizes the GIRAFFE test results to investigate post-LOCA PCCS heat removal performance and post-test analysis using TRAC.

  17. Your Kidney Test Results

    MedlinePlus

    ... Important Tests Blood Pressure Serum Albumin Bicarbonate Blood Urea Nitrogen (BUN) Potassium Calcium Phosphorus Results Goal: Your ... level in your blood. BUN checks how much urea, a waste product, is in your blood. Potassium ...

  18. Laser Cut Nitinol Tubing Fatigue Coupon: Design, Testing, and Endurance Limit

    NASA Astrophysics Data System (ADS)

    Forcucci, Stephen J.

    2014-07-01

    Nitinol medical device implants made from a laser cut tubing process (i.e., stents, valve structures, etc.) frequently require a fatigue durability assessment, which necessitates determining the material fatigue properties. Towards the goal of determining the strain-based endurance limit of medical grade superelastic Nitinol tubing, a coupon was designed and evaluated via FEA using Abaqus software, produced via laser cutting, shape setting, and electro-polishing processes, and then fatigue tested to 10 million cycles. FEA was used to determine the strain versus alternating displacement amplitude for the coupon. Error due to dimensional tolerances was determined. The coupons were then fatigue tested in a 37 °C temperature deionized water bath at alternating strain levels ranging from 0.75 to 4.0% at zero mean strain. Sample replication was greater than 90%, and the median alternating strain fatigue limit was determined via two methods. Confidence and reliability with maximum likelihood statistics are used to present a strain-based endurance limit for the material. The results seem to differ from previous published values.

  19. Effects of test sample shape and surface production method on the fatigue behaviour of PMMA bone cement.

    PubMed

    Sheafi, E M; Tanner, K E

    2014-01-01

    There is no consensus over the optimal criterion to define the fatigue life of bone cement in vitro. Fatigue testing samples have been made into various shapes using different surface preparation techniques with little attention being paid to the importance of these variations on the fatigue results. The present study focuses on the effect of test sample shape and surface production method on the fatigue results. The samples were manufactured with two cross sectional shapes: rectangular according to ISO 527 and circular according to ASTM F2118. Each shape was produced using two methods: direct moulding of the cement dough and machining from oversized rods. Testing was performed using two different bone cements: SmartSet GHV and DePuy CMW1. At least 10 samples of each category were tested, under fully reversed tension-compression fatigue stress at ±20MPa, to allow for Weibull analysis to compare results. The growth of fatigue cracks was observed by means of the changes in the absorbed energy and apparent modulus. It was found that fatigue crack growth can be altered by the sample shape and production method; however it is also dependent on the chemical composition of the cement. The results revealed that moulded samples, particularly those based on the ASTM F2118 standard, can lead to up to 5.5 times greater fatigue lives compared to the machined samples of the same cement. It is thus essential, when comparing the fatigue results of bone cement, to consider the effect of production method along with the shape of the test sample. PMID:24070780

  20. Fiber heart valve prosthesis: Early in vitro fatigue results.

    PubMed

    Vaesken, Antoine; Khoffi, Foued; Heim, Frederic; Dieval, Florence; Chakfe, Nabil

    2016-07-01

    Transcatheter aortic valve replacement has become today a largely considered alternative technique to surgical valve replacement in patients with high risk for open chest surgery. Biological valve tissue used in the transcatheter devices has shown success over 5 years now, but the procedure remains expensive. Moreover, different studies point out potential degradations that the tissue can undergo when folded to lower diameter and released in calcified environment with irregular geometry, which may jeopardize the durability of the device. The use of synthetic materials, like textile in particular, to replace biological valve leaflets would help reducing the procedure costs, and limit the degradations when the valve is crimped. Textile polyester material has been extensively used in the vascular surgery and is characterized by outstanding folding and strength properties combined with proven biocompatibility. However, the friction effects that occur between filaments and between yarns within a fabric under flexure loading could be critical for the resistance of the material on the long term. The purpose of this study was to assess the early fatigue performances of textile valve prototypes under accelerated cyclic loading up to 200 Mio cycles. Durability tests show that the fibrous material undergoes rearrangements between fibrous elements within the textile construction and the mechanical properties are modified on the long term. But testing is not complete with 200 Mio cycles. The material should be tested up to a higher number of cycles in future work to test the effective long-term durability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 986-992, 2016. PMID:25980361

  1. Closed-Loop Control for Sonic Fatigue Testing Systems

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Bossaert, Guido

    2001-01-01

    This article documents recent improvements to the acoustic control system of the Thermal Acoustic Fatigue Apparatus (TAFA), a progressive wave tube test facility at the NASA Langley Research Center, Hampton, VA. A brief summary of past acoustic performance is first given to serve as a basis of comparison with the new performance data using a multiple-input, closed-loop, narrow-band controller. Performance data in the form of test section acoustic power spectral densities and coherence are presented for a variety of input spectra including uniform, band-limited random and an expendable launch vehicle payload bay environment.

  2. Heating and cooling system. [for fatigue test specimens

    NASA Technical Reports Server (NTRS)

    Imig, L. A.; Gardner, M. R. (Inventor)

    1982-01-01

    A heating and cooling apparatus capable of cyclic heating and cooling of a test specimen undergoing fatigue testing is discussed. Cryogenic fluid is passed through a block clamped to the speciment to cool the block and the specimen. Heating cartridges penetrate the block to heat the block and the specimen to very hot temperaures. Control apparatus is provided to alternatively activate the cooling and heating modes to effect cyclic heating and cooling between very hot and very cold temperatures. The block is constructed of minimal mass to facilitate the rapid temperature changes.

  3. Thermal Fatigue Test Apparatus for Large Superconducting Coils

    NASA Astrophysics Data System (ADS)

    Kephart, J. T.; Fitzpatrick, B. K.; Chen, J.; Lopez, J.; Millar, M.; Wong, L.; Zimmerman, M.; Kostic, J.; Rakus, C.

    2008-03-01

    ABSTRACT The United States Navy has a continued interest in the development of High Temperature Superconductivity (HTS) to provide power dense, efficient propulsion and electrical power generation. These machines have large HTS rotor coils that will undergo many thermal cycles during the life of the ship. Thermal fatigue tests for large coils are necessary to understand any degradation and life issues that could arise. The Naval Surface Warfare Center Carderock Division (NSWCCD) has sponsored Rowan University to design and build a device that will assist in the thermal fatigue testing of a superconducting coil. It was designed to be autonomous with programmable cool down and warm-up rates and varying temperature from ambient temperature (300K) down to 77K. A typical test would include thermally cycling a coil a specified number of times, then performing a critical current test on the coil and repeating the test cycle as many times as desired. This paper introduces the thermal cycling test setup and presents preliminary calibration data.

  4. Evaluation of Creep-Fatigue Damage Based on Simplified Model Test Approach

    SciTech Connect

    Wang, Yanli; Li, Tianlei; Sham, Sam; Jetter, Robert I

    2013-01-01

    Current methods used in the ASME Code, Subsection NH for the evaluation of creep-fatigue damage are based on the separation of elevated temperature cyclic damage into two parts, creep damage and fatigue damage. This presents difficulties in both evaluation of test data and determination of cyclic damage in design. To avoid these difficulties, an alternative approach was identified, called the Simplified Model Test or SMT approach based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components of interest. A key feature of the methodology is the use of the results of elastic analysis directly in design evaluation similar to current methods in the ASME Code, Subsection NB. Although originally developed for current material included in Subsection NH, recent interest in the application of Alloy 617 for components operating at very high temperatures has caused renewed interest in the SMT approach because it provides an alternative to the proposed restriction on the use of current Subsection NH simplified methods at very high temperatures. A comprehensive review and assessment of five representative simplified methods for creep-fatigue damage evaluation is presented in Asayama [1]. In this review the SMT methodology was identified as the best long term approach but the need for test data precluded its near term implementation. Asayama and Jetter [2] is a summary of the more comprehensive report by Asayama [1] with a summary of the SMT approach presented by Jetter [3].

  5. Fatigue

    MedlinePlus

    ... Fatigue can be a symptom of anemia, particularly iron-deficiency anemia . Your body needs iron to make hemoglobin, the substance in red blood ... tissues and to your baby. Your need for iron increases during pregnancy because of the needs of ...

  6. Cognitive fatigue influences students' performance on standardized tests.

    PubMed

    Sievertsen, Hans Henrik; Gino, Francesca; Piovesan, Marco

    2016-03-01

    Using test data for all children attending Danish public schools between school years 2009/10 and 2012/13, we examine how the time of the test affects performance. Test time is determined by the weekly class schedule and computer availability at the school. We find that, for every hour later in the day, test performance decreases by 0.9% of an SD (95% CI, 0.7-1.0%). However, a 20- to 30-minute break improves average test performance by 1.7% of an SD (95% CI, 1.2-2.2%). These findings have two important policy implications: First, cognitive fatigue should be taken into consideration when deciding on the length of the school day and the frequency and duration of breaks throughout the day. Second, school accountability systems should control for the influence of external factors on test scores. PMID:26884183

  7. Cognitive fatigue influences students’ performance on standardized tests

    PubMed Central

    Sievertsen, Hans Henrik; Gino, Francesca; Piovesan, Marco

    2016-01-01

    Using test data for all children attending Danish public schools between school years 2009/10 and 2012/13, we examine how the time of the test affects performance. Test time is determined by the weekly class schedule and computer availability at the school. We find that, for every hour later in the day, test performance decreases by 0.9% of an SD (95% CI, 0.7–1.0%). However, a 20- to 30-minute break improves average test performance by 1.7% of an SD (95% CI, 1.2–2.2%). These findings have two important policy implications: First, cognitive fatigue should be taken into consideration when deciding on the length of the school day and the frequency and duration of breaks throughout the day. Second, school accountability systems should control for the influence of external factors on test scores. PMID:26884183

  8. Gigacycle Fatigue Properties of Hydrogen-Charged JIS-SCM440 Low-Alloy Steel Under Ultrasonic Fatigue Testing

    NASA Astrophysics Data System (ADS)

    Furuya, Yoshiyuki; Hirukawa, Hisashi; Hayakawa, Masao

    2010-09-01

    Gigacycle fatigue tests were conducted on hydrogen-charged low-alloy steel. In this study, high- and low-strength specimens were prepared to investigate the effects of hydrogen on internal and surface fractures, respectively. The fatigue tests were conducted mainly by ultrasonic fatigue testing at 20 kHz and additionally by conventional servohydraulic fatigue testing at 50 Hz. All high-strength specimens revealed internal fractures. The fatigue strength of the hydrogen-charged specimens was much lower than that of the uncharged specimens. In the low-strength specimens, the uncharged specimens revealed surface fractures in the short-life regions in addition to internal fractures in the long-life regions. However, the hydrogen-charged specimens revealed internal fractures only that were combined with a much lower fatigue strength. The difference in fracture surfaces was small between the hydrogen-charged and the uncharged specimens, whereas the optically dark areas of the hydrogen-charged specimens seemed smaller than those of the uncharged specimens.

  9. Design of a Compact Fatigue Tester for Testing Irradiated Materials

    SciTech Connect

    Hartsell, Brian; Campbell, Michael; Fitton, Michael; Hurh, Patrick; Ishida, Taku; Nakadaira, Takeshi

    2015-06-01

    A compact fatigue testing machine that can be easily inserted into a hot cell for characterization of irradiated materials is beneficial to help determine relative fatigue performance differences between new and irradiated material. Hot cell use has been carefully considered by limiting the size and weight of the machine, simplifying sample loading and test setup for operation via master-slave manipulator, and utilizing an efficient design to minimize maintenance. Funded from a US-Japan collaborative effort, the machine has been specifically designed to help characterize titanium material specimens. These specimens are flat cantilevered beams for initial studies, possibly utilizing samples irradiated at other sources of beam. The option to test spherically shaped samples cut from the T2K vacuum window is also available. The machine is able to test a sample to $10^7$ cycles in under a week, with options to count cycles and sense material failure. The design of this machine will be presented along with current status.

  10. Lithium cell test results

    NASA Technical Reports Server (NTRS)

    Bragg, B. J.

    1977-01-01

    Three lithium SO2 cells, two lithium CF cells, and a vinyl chloride cell, all with crimped seals, and all strictly experimental, were independently discharged on resistors. Three temperatures were used and several different storage temperatures. Discharge rate generally on the nominal discharges were 0.1 amp, 0.5 amp, and 1 amp. Tests results show that the crimp seals are inadequate, especially for the SO2 cells. Normal discharges present no hazards. All cells discharge to zero. The problem of lithium cell explosions, such as occurred during off-limits testing, is discussed.

  11. Full-scale fatigue tests of CX-100 wind turbine blades. Part I: testing

    NASA Astrophysics Data System (ADS)

    Farinholt, Kevin M.; Taylor, Stuart G.; Park, Gyuhae; Ammerman, Curtt M.

    2012-04-01

    This paper overviews the test setup and experimental methods for structural health monitoring (SHM) of two 9-meter CX-100 wind turbine blades that underwent fatigue loading at the National Renewable Energy Laboratory's (NREL) National Wind Technology Center (NWTC). The first blade was a pristine blade, which was manufactured to standard specifications for the CX-100 design. The second blade was manufactured for the University of Massachusetts, Lowell with intentional simulated defects within the fabric layup. Each blade was instrumented with piezoelectric transducers, accelerometers, acoustic emission sensors, and foil strain gauges. The blades underwent harmonic excitation at their first natural frequency using the Universal Resonant Excitation (UREX) system at NREL. Blades were initially excited at 25% of their design load, and then with steadily increasing loads until each blade reached failure. Data from the sensors were collected between and during fatigue loading sessions. The data were measured over multi-scale frequency ranges using a variety of acquisition equipment, including off-the-shelf systems and specially designed hardware developed at Los Alamos National Laboratory (LANL). The hardware systems were evaluated for their aptness in data collection for effective application of SHM methods to the blades. The results of this assessment will inform the selection of acquisition hardware and sensor types to be deployed on a CX-100 flight test to be conducted in collaboration with Sandia National Laboratory at the U.S. Department of Agriculture's (USDA) Conservation and Production Research Laboratory (CPRL) in Bushland, Texas.

  12. Detection of fatigue cracks by nondestructive testing methods

    NASA Technical Reports Server (NTRS)

    Anderson, R. T.; Delacy, T. J.; Stewart, R. C.

    1973-01-01

    The effectiveness was assessed of various NDT methods to detect small tight cracks by randomly introducing fatigue cracks into aluminum sheets. The study included optimizing NDT methods calibrating NDT equipment with fatigue cracked standards, and evaluating a number of cracked specimens by the optimized NDT methods. The evaluations were conducted by highly trained personnel, provided with detailed procedures, in order to minimize the effects of human variability. These personnel performed the NDT on the test specimens without knowledge of the flaw locations and reported on the flaws detected. The performance of these tests was measured by comparing the flaws detected against the flaws present. The principal NDT methods utilized were radiographic, ultrasonic, penetrant, and eddy current. Holographic interferometry, acoustic emission monitoring, and replication methods were also applied on a reduced number of specimens. Generally, the best performance was shown by eddy current, ultrasonic, penetrant and holographic tests. Etching provided no measurable improvement, while proof loading improved flaw detectability. Data are shown that quantify the performances of the NDT methods applied.

  13. The detection of tightly closed flaws by nondestructive testing (NDT) methods. [fatigue crack formation in aluminum alloy test specimens

    NASA Technical Reports Server (NTRS)

    Rummel, W. D.; Rathke, R. A.; Todd, P. H., Jr.; Mullen, S. J.

    1975-01-01

    Liquid penetrant, ultrasonic, eddy current and X-radiographic techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens in integrally stiffened panel, and weld panel configurations. Fatigue cracks in integrally stiffened panels, lack-of-fusion in weld panels, and fatigue cracks in weld panels were the flaw types used for evaluation. A 2319 aluminum alloy weld filler rod was used for all welding to produce the test specimens. Forty seven integrally stiffened panels containing a total of 146 fatigue cracks, ninety three lack-of-penetration (LOP) specimens containing a total of 239 LOP flaws, and one-hundred seventeen welded specimens containing a total of 293 fatigue cracks were evaluated. Nondestructive test detection reliability enhancement was evaluated during separate inspection sequences in the specimens in the 'as-machined or as-welded', post etched and post proof loaded conditions. Results of the nondestructive test evaluations were compared to the actual flaw size obtained by measurement of the fracture specimens after completing all inspection sequences. Inspection data were then analyzed to provide a statistical basis for determining the flaw detection reliability.

  14. Fracture mechanics analysis of composite microcracking - Experimental results in fatigue

    NASA Technical Reports Server (NTRS)

    Nairn, J. A.; Liu, S.

    1990-01-01

    The Nairn (1989) variational mechanics analysis, which yields the energy release rate of a microcrack's formation between two existing microcracks, has proven useful in the fracture mechanics interpretation of cross-ply laminates' microcracking. Attention is presently given to the application of this energy release rate analysis to a fracture mechanics-based interpretation of microcrack formation during fatigue loading, for the case of fatigue experiments on three layups of Avimid K/IM6 laminates and four layups of Fiberite 934/T300 laminates. The single master Paris-law plot onto which the data from all layups of a given material system fall is claimed to offer a complete characterization of that system's microcrack-formation resistance during fatigue loading.

  15. Conducting High Cycle Fatigue Strength Step Tests on Gamma TiAl

    NASA Technical Reports Server (NTRS)

    Lerch, Brad; Draper, Sue; Pereira, J. Mike

    2002-01-01

    High cycle fatigue strength testing of gamma TiAl by the step test method is investigated. A design of experiments was implemented to determine if the coaxing effect occurred during testing. Since coaxing was not observed, step testing was deemed a suitable method to define the fatigue strength at 106 cycles.

  16. Mechanical Fatigue Testing of High Burnup Fuel for Transportation Applications

    SciTech Connect

    Wang, Jy-An John; Wang, Hong

    2015-05-01

    This report describes testing designed to determine the ability of high burnup (HBU) (>45 GWd/MTU) spent fuel to maintain its integrity under normal conditions of transportation. An innovative system, Cyclic Integrated Reversible-bending Fatigue Tester (CIRFT), has been developed at Oak Ridge National Laboratory (ORNL) to test and evaluate the mechanical behavior of spent nuclear fuel (SNF) under conditions relevant to storage and transportation. The CIRFT system is composed of a U-frame equipped with load cells for imposing the pure bending loads on the SNF rod test specimen and measuring the in-situ curvature of the fuel rod during bending using a set up with three linear variable differential transformers (LVDTs).

  17. Flexure fatigue testing of 90 deg graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Peck, Ann Nancy W.

    1995-01-01

    A great deal of research has been performed characterizing the in-plane fiber-dominated properties, under both static and fatigue loading, of advanced composite materials. To the author's knowledge, no study has been performed to date investigating fatigue characteristics in the transverse direction. This information is important in the design of bonded composite airframe structure where repeated, cyclic out-of-plane bending may occur. Recent tests characterizing skin/stringer debond failures in reinforced composite panels where the dominant loading in the skin is flexure along the edge of the frame indicate failure initiated either in the skin or else the flange, near the flange tip. When failure initiated in the skin, transverse matrix cracks formed in the surface skin ply closest to the flange and either initiated delaminations or created matrix cracks in the next lower ply, which in turn initiated delaminations. When failure initiated in the flanges, transverse cracks formed in the flange angle ply closest to the skin and initiated delamination. In no configuration did failure propagate through the adhesive bond layer. For the examined skin/flange configurations, the maximum transverse tension stress at failure correlates very well with the transverse tension strength of the composites. Transverse tension strength (static) data of graphite epoxy composites have been shown to vary with the volume of material stressed. As the volume of material stressed increased, the strength decreased. A volumetric scaling law based on Weibull statistics can be used to predict the transverse strength measurements. The volume dependence reflects the presence of inherent flaws in the microstructure of the lamina. A similar approach may be taken to determine a volume scale effect on the transverse tension fatigue behavior of graphite/epoxy composites. The objective of this work is to generate transverse tension strength and fatigue S-N characteristics for composite materials using

  18. Microstructural changes induced near crack tip during corrosion fatigue tests in austenitic-ferritic steel.

    PubMed

    Gołebiowski, B; Swiatnicki, W A; Gaspérini, M

    2010-03-01

    Microstructural changes occurring during fatigue tests of austenitic-ferritic duplex stainless steel (DSS) in air and in hydrogen-generating environment have been investigated. Hydrogen charging of steel samples during fatigue crack growth (FCG) tests was performed by cathodic polarization of specimens in 0.1M H(2)SO(4) aqueous solution. Microstructural investigations of specimens after FCG tests were carried out using transmission electron microscopy to reveal the density and arrangement of dislocations formed near crack tip. To determine the way of crack propagation in the microstructure, electron backscatter diffraction investigations were performed on fatigue-tested samples in both kinds of environment. To reveal hydrogen-induced phase transformations the atomic force microscopy was used. The above investigations allowed us to define the character of fatigue crack propagation and microstructural changes near the crack tip. It was found that crack propagation after fatigue tests in air is accompanied with plastic deformation; a high density of dislocations is observed at large distance from the crack. After fatigue tests performed during hydrogen charging the deformed zone containing high density of dislocations is narrow compared to that after fatigue tests in air. It means that hydrogenation leads to brittle character of fatigue crack propagation. In air, fatigue cracks propagate mostly transgranularly, whereas in hydrogen-generating environment the cracks have mixed transgranular/interfacial character. PMID:20500395

  19. Fatigue testing of laser treated endosseous implants with an internal trilobe connection.

    PubMed

    Berg, Robert W; Kurtz, Kenneth S; Griggs, Jason A; Watanabe, Ikuya; Coelho, Paulo G

    2011-03-01

    This study investigated the effect of laser treatment on the fatigue resistance of a 3.5-mm diameter implant with an internal trilobe connection. Twenty two implants were embedded into acrylic resin blocks. Half the specimens were used as control group, and the other half were laser treated circumferentially around the 1.5-mm polished collar with argon shielding. Implants were fatigue tested using a step-stress accelerated lifetime test in a servo-hydraulic test machine. Despite the trend pointing towards higher fatigue resistance of laser treated specimens versus controls, step-stress analysis did not determine significant differences in the fatigue lifetimes. PMID:21528680

  20. Clinical utility of blood tests in elite athletes with short term fatigue

    PubMed Central

    Fallon, K E

    2006-01-01

    Objective To determine, in a population of elite athletes at their initial presentation with tiredness or fatigue, whether a set of haematological and biochemical investigations enhances the diagnostic process over and above the information gained from clinical history and examination. Methods A sequential series of 50 elite athletes were studied at the initial consultation for a primary complaint of fatigue, tiredness, or a synonym thereof. A standardised clinical history, physical examination, and series of haematological and biochemical test were performed. The effects of the results of the blood tests on the diagnosis made after the clinical history and examination were examined. Results In only one case did the test results lead to an alteration in diagnosis. Physical examination did not provide any findings that would not have been suspected from the history, except for a number of incidental findings not relevant to the presenting symptom. Discussion In cases of short term fatigue in elite athletes, a thorough clinical history is mandatory. Physical examination is unlikely to reveal any findings not suspected from the history. Routine ordering of a panel of blood tests at the initial consultation should be discouraged. Unless specifically indicated by the history and examination, investigations are not required at the initial consultation. PMID:16547143

  1. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue

    SciTech Connect

    Bosco, Nick; Silverman, Timothy J.; Wohlgemuth, John; Kurtz, Sarah; Inoue, Masanao; Sakurai, Keiichiro; Shioda, Tsuyoshi; Zenkoh, Hirofumi; Hirota, Kusato; Miyashita, Masanori; Tadanori, Tanahashi; Suzuki, Soh; Chen, Yifeng; Verlinden, Pierre J.

    2014-12-31

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours of testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  2. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue: Preprint

    SciTech Connect

    Bosco, N.; Silverman, T. J.; Wohlgemuth, J.; Kurtz, S.; Inoue, M.; Sakurai, K.; Shinoda, T.; Zenkoh, H.; Hirota, K.; Miyashita, M.; Tadanori, T.; Suzuki, S.

    2015-04-07

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours o testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  3. Tensile and fatigue qualification testing of ITER-CS conduit alloy JK2LB

    NASA Astrophysics Data System (ADS)

    Walsh, R. P.; McRae, D. M.; Han, K.; Martovetsky, N. N.

    2015-12-01

    The ITER Central Solenoid (CS) coils utilize cable-in-conduit conductor (CICC) and the conduit alloy is JK2LB. The production grade conduit alloy (and it's welds) must meet strict requirements for strength, toughness, fatigue crack resistance, and fabricability. The conduit alloy must retain good mechanical properties after additional fabrication steps such as welding, coil winding strain and exposure to the Nb3Sn superconductor's reaction heat treatment. Here we present data from cryogenic tensile, fracture toughness, fatigue crack growth rate, and axial fatigue tests of JK2LB alloy and conduit butt welds, before and after the exposure to the reaction heat treatment. The tests of specimens removed directly from the conduit provide confirmation of the materials properties and the effect of the cold work and aging. The 4 K fatigue performance is extremely important to the reliability of the CS and is covered both by axial cyclic fatigue tests and the fatigue crack growth rate measurements.

  4. The fracture morphology of nickel-base superalloys tested in fatigue and creep-fatigue at 650 C

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Miner, R. V.

    1981-01-01

    The fracture surfaces of compact tension specimens from seven nickel-base superalloys fatigue tested at 650 C were studied by scanning electron microscopy and optical metallography to determine the nature and morphology of the crack surface in the region of stable growth. Crack propagation testing was performed as part of an earlier study at 650 C in air using a 0.33 Hz fatigue cycle and a creep-fatigue cycle incorporating a 900 second dwell at maximum load. In fatigue, alloys with a grain size greater than 20 micrometers, HIP Astroloy, Waspaloy, and MERL 76, exhibited transgranular fracture. MERL 76 also displayed numerous fracture sites which were associated with boundaries of prior powder particles. The two high strength, fine grain alloys, IN 100 and NASA IIB-7, exhibited intergranular fracture. Rene 95 and HIP plus forged Astroloy displayed a mixed failure mode that was transgranular in the coarse grains and intergranular in the fine grains. Under creep-fatigue conditions, fracture was found to be predominantly intergranular in all seven alloys.

  5. Design and fabrication of a bending rotation fatigue test rig for in situ electrochemical analysis during fatigue testing of NiTi shape memory alloy wires.

    PubMed

    Neelakantan, Lakshman; Zglinski, Jenni Kristin; Frotscher, Matthias; Eggeler, Gunther

    2013-03-01

    The current investigation proposes a novel method for simultaneous assessment of the electrochemical and structural fatigue properties of nickel-titanium shape memory alloy (NiTi SMA) wires. The design and layout of an in situ electrochemical cell in a custom-made bending rotation fatigue (BRF) test rig is presented. This newly designed test rig allows performing a wide spectrum of experiments for studying the influence of fatigue on corrosion and vice versa. This can be achieved by performing ex situ and∕or in situ measurements. The versatility of the combined electrochemical∕mechanical test rig is demonstrated by studying the electrochemical behavior of NiTi SMA wires in 0.9% NaCl electrolyte under load. The ex situ measurements allow addressing various issues, for example, the influence of pre-fatigue on the localized corrosion resistance, or the influence of hydrogen on fatigue life. Ex situ experiments showed that a pre-fatigued wire is more susceptible to localized corrosion. The synergetic effect can be concluded from the polarization studies and specifically from an in situ study of the open circuit potential (OCP) transients, which sensitively react to the elementary repassivation events related to the local failure of the oxide layer. It can also be used as an indicator for identifying the onset of the fatigue failure. PMID:23556847

  6. Design and fabrication of a bending rotation fatigue test rig for in situ electrochemical analysis during fatigue testing of NiTi shape memory alloy wires

    NASA Astrophysics Data System (ADS)

    Neelakantan, Lakshman; Zglinski, Jenni Kristin; Frotscher, Matthias; Eggeler, Gunther

    2013-03-01

    The current investigation proposes a novel method for simultaneous assessment of the electrochemical and structural fatigue properties of nickel-titanium shape memory alloy (NiTi SMA) wires. The design and layout of an in situ electrochemical cell in a custom-made bending rotation fatigue (BRF) test rig is presented. This newly designed test rig allows performing a wide spectrum of experiments for studying the influence of fatigue on corrosion and vice versa. This can be achieved by performing ex situ and/or in situ measurements. The versatility of the combined electrochemical/mechanical test rig is demonstrated by studying the electrochemical behavior of NiTi SMA wires in 0.9% NaCl electrolyte under load. The ex situ measurements allow addressing various issues, for example, the influence of pre-fatigue on the localized corrosion resistance, or the influence of hydrogen on fatigue life. Ex situ experiments showed that a pre-fatigued wire is more susceptible to localized corrosion. The synergetic effect can be concluded from the polarization studies and specifically from an in situ study of the open circuit potential (OCP) transients, which sensitively react to the elementary repassivation events related to the local failure of the oxide layer. It can also be used as an indicator for identifying the onset of the fatigue failure.

  7. Design and fabrication of a bending rotation fatigue test rig for in situ electrochemical analysis during fatigue testing of NiTi shape memory alloy wires

    SciTech Connect

    Neelakantan, Lakshman; Zglinski, Jenni Kristin; Eggeler, Gunther; Frotscher, Matthias

    2013-03-15

    The current investigation proposes a novel method for simultaneous assessment of the electrochemical and structural fatigue properties of nickel-titanium shape memory alloy (NiTi SMA) wires. The design and layout of an in situ electrochemical cell in a custom-made bending rotation fatigue (BRF) test rig is presented. This newly designed test rig allows performing a wide spectrum of experiments for studying the influence of fatigue on corrosion and vice versa. This can be achieved by performing ex situ and/or in situ measurements. The versatility of the combined electrochemical/mechanical test rig is demonstrated by studying the electrochemical behavior of NiTi SMA wires in 0.9% NaCl electrolyte under load. The ex situ measurements allow addressing various issues, for example, the influence of pre-fatigue on the localized corrosion resistance, or the influence of hydrogen on fatigue life. Ex situ experiments showed that a pre-fatigued wire is more susceptible to localized corrosion. The synergetic effect can be concluded from the polarization studies and specifically from an in situ study of the open circuit potential (OCP) transients, which sensitively react to the elementary repassivation events related to the local failure of the oxide layer. It can also be used as an indicator for identifying the onset of the fatigue failure.

  8. Fatigue behavior of carbon fiber reinforced epoxy composites -[{+-}45]{sub 4s} laminate under tension-tension and tension - compression fatigue loading test

    SciTech Connect

    Ma, C.C.M.; Tai, N.H.; Wu, G.Y.; Lin, S.H.

    1996-12-31

    Fatigue behaviors of carbon fiber reinforced epoxy laminated composite have been investigated. The [{+-}45]4S laminates of T300/976 Carbon/Epoxy were utilized. The static tensile strength and tension-tension tension-compression fatigue loading tests at various levels of stress amplitude were measured. The median rank method was applied to predict the statistical probability of experimental data of fatigue life. The S-N curves for various survival probabilities were established using the pooled Weibull distribution function. The theoretical prediction methods could be applied to illustrate the fatigue behavior of thermoset matrix polymer composites. Furthermore, the fatigue behaviors under tension - tension and tension-compression fatigue loading test were investigated. Both the stiffness degradation and the surface temperature change during fatigue test are discussed.

  9. Construct Validation of a Multidimensional Computerized Adaptive Test for Fatigue in Rheumatoid Arthritis

    PubMed Central

    Nikolaus, Stephanie; Bode, Christina; Taal, Erik; Vonkeman, Harald E.; Glas, Cees A. W.; van de Laar, Mart A. F. J.

    2015-01-01

    Objective Multidimensional computerized adaptive testing enables precise measurements of patient-reported outcomes at an individual level across different dimensions. This study examined the construct validity of a multidimensional computerized adaptive test (CAT) for fatigue in rheumatoid arthritis (RA). Methods The ‘CAT Fatigue RA’ was constructed based on a previously calibrated item bank. It contains 196 items and three dimensions: ‘severity’, ‘impact’ and ‘variability’ of fatigue. The CAT was administered to 166 patients with RA. They also completed a traditional, multidimensional fatigue questionnaire (BRAF-MDQ) and the SF-36 in order to examine the CAT’s construct validity. A priori criterion for construct validity was that 75% of the correlations between the CAT dimensions and the subscales of the other questionnaires were as expected. Furthermore, comprehensive use of the item bank, measurement precision and score distribution were investigated. Results The a priori criterion for construct validity was supported for two of the three CAT dimensions (severity and impact but not for variability). For severity and impact, 87% of the correlations with the subscales of the well-established questionnaires were as expected but for variability, 53% of the hypothesised relations were found. Eighty-nine percent of the items were selected between one and 137 times for CAT administrations. Measurement precision was excellent for the severity and impact dimensions, with more than 90% of the CAT administrations reaching a standard error below 0.32. The variability dimension showed good measurement precision with 90% of the CAT administrations reaching a standard error below 0.44. No floor- or ceiling-effects were found for the three dimensions. Conclusion The CAT Fatigue RA showed good construct validity and excellent measurement precision on the dimensions severity and impact. The dimension variability had less ideal measurement characteristics

  10. Exploratory Thermal-mechanical Fatigue Results for Rene' 80 in Ultrahigh Vacuum

    NASA Technical Reports Server (NTRS)

    Sheinker, A. A.

    1978-01-01

    A limited study was conducted of the use of strainage partitioning for predicting the thermalmechanical fatigue life of cast nickel-base superalloy Rene' 80. The fatigue lives obtained by combined inphase thermal and mechanical strain cycling between 400 C (752 F) and 1000 C (1802 F) in an ultrahigh vacuum were considerably shorter than those represented by the four basic partitioned inelastic strainrange fatigue life relationships established previously for this alloy at 871 C (1600 F) and 1000 C (1832 F) in an ultrahigh vacuum. This behavior was attributed to the drastic decrease in ductility with decreasing temperature for this alloy. These results indicated that the prediction of the thermal-mechanical fatigue life of Rene' 80 by the method of strainrange partioning may be improved if based on the four basic fatigue life relationships determined at a lower temperature in the thermal-mechanical strain cycle.

  11. An engineering method for estimating notch-size effect in fatigue tests on steel

    NASA Technical Reports Server (NTRS)

    Kuhn, Paul; Hardrath, Herbert F

    1952-01-01

    Neuber's proposed method of calculating a practical factor of stress concentration for parts containing notches of arbitrary size depends on the knowledge of a "new material constant" which can be established only indirectly. In this paper, the new constant has been evaluated for a large variety of steels from fatigue tests reported in the literature, attention being confined to stresses near the endurance limit. Reasonably satisfactory results were obtained with the assumption that the constant depends only on the tensile strength of the steel. Even in cases where the notches were cracks of which only the depth was known, reasonably satisfactory agreement was found between calculated and experimental factors. It is also shown that the material constant can be used in an empirical formula to estimate the size effect on unnotched specimens tested in bending fatigue.

  12. Lamb wave ultrasonic evaluation of welded AA2024 specimens at tensile static and fatigue testing

    NASA Astrophysics Data System (ADS)

    Burkov, M. V.; Byakov, A. V.; Shah, R. T.; Lyubutin, P. S.; Panin, S. V.

    2015-10-01

    The paper deals with the investigation of Lamb waves ultrasonic testing technique applied for evaluation of different stress-strain and damaged state of aluminum specimens at static and fatigue loading in order to develop a Structural Health Monitoring (SHM) approach. The experimental results of tensile testing of AA2024T3 specimens with welded joints are presented. Piezoelectric transducers used as actuators and sensors were adhesively bonded to the specimen's surface using two component epoxy. The set of static and cyclic tensile tests with two frequencies of acoustic testing (50 kHz and 335 kHz) were performed. The recorded signals were processed to calculate the maximum envelope in order to evaluate the changes of the stress-strain state of the specimen and its microstructure during static tension. The registered data are analyzed and discussed in terms of signal attenuation due to the formation of fatigue defects during cyclic loading. Understanding the relations between acoustic signal features and fatigue damages will provide us the ability to determine the damage state of the structure and its residual lifetime in order to design a robust SHM system.

  13. Creep-Fatigue Interaction and Cyclic Strain Analysis in P92 Steel Based on Test

    NASA Astrophysics Data System (ADS)

    Ji, Dongmei; Zhang, Lai-Chang; Ren, Jianxing; Wang, Dexian

    2015-04-01

    This work focused on the interaction of creep and fatigue and cyclic strain analysis in high-chromium ferritic P92 steel based on load-controlled creep-fatigue (CF) tests and conventional creep test at 873 K. Mechanical testing shows that the cyclic load inhibits the propagation of creep damage in the P92 steel and CF interaction becomes more severe with the decrease in the holding period duration and stress ratio. These results are also verified by the analysis of cyclic strain. The fatigue lifetime reduces with the increasing of the holding period duration and it does not reduce much with the increasing stress ratio especially under the conditions of long holding period duration. The cyclic strains (i.e., the strain range and creep strain) of CF tests consist of three stages, which is the same as those for the conventional creep behavior. The microscopic fracture surface observations illustrated that two different kinds of voids are observed at the fracture surfaces and Laves phase precipitates at the bottom of the voids.

  14. Blood-Borne Markers of Fatigue in Competitive Athletes – Results from Simulated Training Camps

    PubMed Central

    Hecksteden, Anne; Skorski, Sabrina; Schwindling, Sascha; Hammes, Daniel; Pfeiffer, Mark; Kellmann, Michael; Ferrauti, Alexander; Meyer, Tim

    2016-01-01

    Assessing current fatigue of athletes to fine-tune training prescriptions is a critical task in competitive sports. Blood-borne surrogate markers are widely used despite the scarcity of validation trials with representative subjects and interventions. Moreover, differences between training modes and disciplines (e.g. due to differences in eccentric force production or calorie turnover) have rarely been studied within a consistent design. Therefore, we investigated blood-borne fatigue markers during and after discipline-specific simulated training camps. A comprehensive panel of blood-born indicators was measured in 73 competitive athletes (28 cyclists, 22 team sports, 23 strength) at 3 time-points: after a run-in resting phase (d 1), after a 6-day induction of fatigue (d 8) and following a subsequent 2-day recovery period (d 11). Venous blood samples were collected between 8 and 10 a.m. Courses of blood-borne indicators are considered as fatigue dependent if a significant deviation from baseline is present at day 8 (Δfatigue) which significantly regresses towards baseline until day 11 (Δrecovery). With cycling, a fatigue dependent course was observed for creatine kinase (CK; Δfatigue 54±84 U/l; Δrecovery -60±83 U/l), urea (Δfatigue 11±9 mg/dl; Δrecovery -10±10 mg/dl), free testosterone (Δfatigue -1.3±2.1 pg/ml; Δrecovery 0.8±1.5 pg/ml) and insulin linke growth factor 1 (IGF-1; Δfatigue -56±28 ng/ml; Δrecovery 53±29 ng/ml). For urea and IGF-1 95% confidence intervals for days 1 and 11 did not overlap with day 8. With strength and high-intensity interval training, respectively, fatigue-dependent courses and separated 95% confidence intervals were present for CK (strength: Δfatigue 582±649 U/l; Δrecovery -618±419 U/l; HIIT: Δfatigue 863±952 U/l; Δrecovery -741±842 U/l) only. These results indicate that, within a comprehensive panel of blood-borne markers, changes in fatigue are most accurately reflected by urea and IGF-1 for cycling and by CK

  15. Blood-Borne Markers of Fatigue in Competitive Athletes - Results from Simulated Training Camps.

    PubMed

    Hecksteden, Anne; Skorski, Sabrina; Schwindling, Sascha; Hammes, Daniel; Pfeiffer, Mark; Kellmann, Michael; Ferrauti, Alexander; Meyer, Tim

    2016-01-01

    Assessing current fatigue of athletes to fine-tune training prescriptions is a critical task in competitive sports. Blood-borne surrogate markers are widely used despite the scarcity of validation trials with representative subjects and interventions. Moreover, differences between training modes and disciplines (e.g. due to differences in eccentric force production or calorie turnover) have rarely been studied within a consistent design. Therefore, we investigated blood-borne fatigue markers during and after discipline-specific simulated training camps. A comprehensive panel of blood-born indicators was measured in 73 competitive athletes (28 cyclists, 22 team sports, 23 strength) at 3 time-points: after a run-in resting phase (d 1), after a 6-day induction of fatigue (d 8) and following a subsequent 2-day recovery period (d 11). Venous blood samples were collected between 8 and 10 a.m. Courses of blood-borne indicators are considered as fatigue dependent if a significant deviation from baseline is present at day 8 (Δfatigue) which significantly regresses towards baseline until day 11 (Δrecovery). With cycling, a fatigue dependent course was observed for creatine kinase (CK; Δfatigue 54±84 U/l; Δrecovery -60±83 U/l), urea (Δfatigue 11±9 mg/dl; Δrecovery -10±10 mg/dl), free testosterone (Δfatigue -1.3±2.1 pg/ml; Δrecovery 0.8±1.5 pg/ml) and insulin linke growth factor 1 (IGF-1; Δfatigue -56±28 ng/ml; Δrecovery 53±29 ng/ml). For urea and IGF-1 95% confidence intervals for days 1 and 11 did not overlap with day 8. With strength and high-intensity interval training, respectively, fatigue-dependent courses and separated 95% confidence intervals were present for CK (strength: Δfatigue 582±649 U/l; Δrecovery -618±419 U/l; HIIT: Δfatigue 863±952 U/l; Δrecovery -741±842 U/l) only. These results indicate that, within a comprehensive panel of blood-borne markers, changes in fatigue are most accurately reflected by urea and IGF-1 for cycling and by CK

  16. Residual strength and crack propagation tests on C-130 airplane center wings with service-imposed fatigue damage

    NASA Technical Reports Server (NTRS)

    Snider, H. L.; Reeder, F. L.; Dirkin, W. J.

    1972-01-01

    Fourteen C-130 airplane center wings, each containing service-imposed fatigue damage resulting from 4000 to 13,000 accumulated flight hours, were tested to determine their fatigue crack propagation and static residual strength characteristics. Eight wings were subjected to a two-step constant amplitude fatigue test prior to static testing. Cracks up to 30 inches long were generated in these tests. Residual static strengths of these wings ranged from 56 to 87 percent of limit load. The remaining six wings containing cracks up to 4 inches long were statically tested as received from field service. Residual static strengths of these wings ranged from 98 to 117 percent of limit load. Damage-tolerant structural design features such as fastener holes, stringers, doublers around door cutouts, and spanwise panel splices proved to be effective in retarding crack propagation.

  17. Fatigue of Self-Healing Nanofiber-based Composites: Static Test and Subcritical Crack Propagation.

    PubMed

    Lee, Min Wook; Sett, Soumyadip; Yoon, Sam S; Yarin, Alexander L

    2016-07-20

    Here, we studied the self-healing of composite materials filled with epoxy-containing nanofibers. An initial incision in the middle of a composite sample stretched in a static fatigue test can result in either crack propagation or healing. In this study, crack evolution was observed in real time. A binary epoxy, which acted as a self-healing agent, was encapsulated in two separate types of interwoven nano/microfibers formed by dual-solution blowing, with the core containing either epoxy or hardener and the shell being formed from poly(vinylidene fluoride)/ poly(ethylene oxide) mixture. The core-shell fibers were encased in a poly(dimethylsiloxane) matrix. When the fibers were damaged by a growing crack in this fiber-reinforced composite material because of static stretching in the fatigue test, they broke and released the healing agent into the crack area. The epoxy used in this study was cured and solidified for approximately an hour at room temperature, which then conglutinated and healed the damaged location. The observations were made for at least several hours and in some cases up to several days. It was revealed that the presence of the healing agent (the epoxy) in the fibers successfully prevented the propagation of cracks in stretched samples subjected to the fatigue test. A theoretical analysis of subcritical cracks was performed, and it revealed a jumplike growth of subcritical cracks, which was in qualitative agreement with the experimental results. PMID:27332924

  18. Physiological Interpretation of the Slope during an Isokinetic Fatigue Test.

    PubMed

    Bosquet, L; Gouadec, K; Berryman, N; Duclos, C; Gremeaux, V; Croisier, J-L

    2015-07-01

    To assess the relationship between selected measures (the slope and average performance) obtained during a high intensity isokinetic fatigue test of the knee (FAT) and relevant measures of anaerobic and aerobic capacities. 20 well-trained cyclists performed 3 randomly ordered sessions involving a FAT consisting in 30 reciprocal maximal concentric contractions of knee flexors and extensors at 180°.s(-1), a maximal continuous graded exercise test (GXT), and a Wingate anaerobic test (WAnT). The slope calculated from peak torque (PT) and total work (TW) of knee extensors was highly associated to maximal PT (r=-0.86) and maximal TW (r=-0.87) measured during FAT, and moderately associated to peak power output measured during the WAnT (r=-0.64 to -0.71). Average PT and average TW were highly associated to maximal PT (r=0.93) and maximal TW (r=0.96), to mean power output measured during WAnT (r=0.83-0.90) and moderately associated to maximal oxygen uptake (0.58-0.67). In conclusion, the slope is mainly determined by maximal anaerobic power, while average performance is a composite measure depending on both aerobic and anaerobic energy systems according to proportions that are determined by the duration of the test. PMID:25941926

  19. Prediction of Frequency for Simulation of Asphalt Mix Fatigue Tests Using MARS and ANN

    PubMed Central

    Fakhri, Mansour

    2014-01-01

    Fatigue life of asphalt mixes in laboratory tests is commonly determined by applying a sinusoidal or haversine waveform with specific frequency. The pavement structure and loading conditions affect the shape and the frequency of tensile response pulses at the bottom of asphalt layer. This paper introduces two methods for predicting the loading frequency in laboratory asphalt fatigue tests for better simulation of field conditions. Five thousand (5000) four-layered pavement sections were analyzed and stress and strain response pulses in both longitudinal and transverse directions was determined. After fitting the haversine function to the response pulses by the concept of equal-energy pulse, the effective length of the response pulses were determined. Two methods including Multivariate Adaptive Regression Splines (MARS) and Artificial Neural Network (ANN) methods were then employed to predict the effective length (i.e., frequency) of tensile stress and strain pulses in longitudinal and transverse directions based on haversine waveform. It is indicated that, under controlled stress and strain modes, both methods (MARS and ANN) are capable of predicting the frequency of loading in HMA fatigue tests with very good accuracy. The accuracy of ANN method is, however, more than MARS method. It is furthermore shown that the results of the present study can be generalized to sinusoidal waveform by a simple equation. PMID:24688400

  20. A high temperature fatigue and structures testing facility

    NASA Technical Reports Server (NTRS)

    Bartolotta, Paul A.; Mcgaw, Michael A.

    1987-01-01

    As man strives for higher levels of sophistication in air and space transportation, awareness of the need for accurate life and material behavior predictions for advanced propulsion system components is heightened. Such sophistication will require complex operating conditions and advanced materials to meet goals in performance, thrust-to-weight ratio, and fuel efficiency. To accomplish these goals will require that components be designed using a high percentage of the material's ultimate capabilities. This serves only to complicate matters dealing with life and material behavior predictions. An essential component of material behavior model development is the underlying experimentation which must occur to identify phenomena. To support experimentation, the NASA Lewis Research Center's High Temperature Fatigue and Structures Laboratory has been expanded significantly. Several new materials testing systems have been added, as well as an extensive computer system. The intent of this paper is to present an overview of the laboratory, and to discuss specific aspects of the test systems. A limited discussion of computer capabilities will also be presented.

  1. A New High-Speed, High-Cycle, Gear-Tooth Bending Fatigue Test Capability

    NASA Technical Reports Server (NTRS)

    Stringer, David B.; Dykas, Brian D.; LaBerge, Kelsen E.; Zakrajsek, Andrew J.; Handschuh, Robert F.

    2011-01-01

    A new high-speed test capability for determining the high cycle bending-fatigue characteristics of gear teeth has been developed. Experiments were performed in the test facility using a standard spur gear test specimens designed for use in NASA Glenn s drive system test facilities. These tests varied in load condition and cycle-rate. The cycle-rate varied from 50 to 1000 Hz. The loads varied from high-stress, low-cycle loads to near infinite life conditions. Over 100 tests were conducted using AISI 9310 steel spur gear specimen. These results were then compared to previous data in the literature for correlation. Additionally, a cycle-rate sensitivity analysis was conducted by grouping the results according to cycle-rate and comparing the data sets. Methods used to study and verify load-path and facility dynamics are also discussed.

  2. Pressure locking test results

    SciTech Connect

    DeWall, K.G.; Watkins, J.C.; McKellar, M.G.; Bramwell, D.

    1996-12-01

    The U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research, is funding the Idaho National Engineering Laboratory (INEL) in performing research to provide technical input for their use in evaluating responses to Generic Letter 95-07, {open_quotes}Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves.{close_quotes} Pressure locking and thermal binding are phenomena that make a closed gate valve difficult to open. This paper discusses only the pressure locking phenomenon in a flexible-wedge gate valve; the authors will publish the results of their thermal binding research at a later date. Pressure locking can occur when operating sequences or temperature changes cause the pressure of the fluid in the bonnet (and, in most valves, between the discs) to be higher than the pressure on the upstream and downstream sides of the disc assembly. This high fluid pressure presses the discs against both seats, making the disc assembly harder to unseat than anticipated by the typical design calculations, which generally consider friction at only one of the two disc/seat interfaces. The high pressure of the bonnet fluid also changes the pressure distribution around the disc in a way that can further contribute to the unseating load. If the combined loads associated with pressure locking are very high, the actuator might not have the capacity to open the valve. The results of the NRC/INEL research discussed in this paper show that the relationship between bonnet pressure and pressure locking stem loads appears linear. The results also show that for this valve, seat leakage affects the bonnet pressurization rate when the valve is subjected to thermally induced pressure locking conditions.

  3. Organic Separation Test Results

    SciTech Connect

    Russell, Renee L.; Rinehart, Donald E.; Peterson, Reid A.

    2014-09-22

    Separable organics have been defined as “those organic compounds of very limited solubility in the bulk waste and that can form a separate liquid phase or layer” (Smalley and Nguyen 2013), and result from three main solvent extraction processes: U Plant Uranium Recovery Process, B Plant Waste Fractionation Process, and Plutonium Uranium Extraction (PUREX) Process. The primary organic solvents associated with tank solids are TBP, D2EHPA, and NPH. There is concern that, while this organic material is bound to the sludge particles as it is stored in the tanks, waste feed delivery activities, specifically transfer pump and mixer pump operations, could cause the organics to form a separated layer in the tank farms feed tank. Therefore, Washington River Protection Solutions (WRPS) is experimentally evaluating the potential of organic solvents separating from the tank solids (sludge) during waste feed delivery activities, specifically the waste mixing and transfer processes. Given the Hanford Tank Waste Treatment and Immobilization Plant (WTP) waste acceptance criteria per the Waste Feed Acceptance Criteria document (24590-WTP-RPT-MGT-11-014) that there is to be “no visible layer” of separable organics in the waste feed, this would result in the batch being unacceptable to transfer to WTP. This study is of particular importance to WRPS because of these WTP requirements.

  4. Proof test and fatigue crack growth modeling on 2024-T3 aluminum alloy

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Poe, C. C., Jr.; Dawicke, D. S.

    1990-01-01

    Pressure proof testing of aircraft fuselage structures has been suggested as a means of screening critical crack sizes and of extending their useful life. The objective of this paper is to study the proof-test concept and to model the crack-growth process on a ductile material. Simulated proof and operational fatigue life tests have been conducted on cracked panels made of 2024-T3 aluminum alloy sheet material. A fatigue crack-closure model was modified to simulate the proof test and operational fatigue cycling. Using crack-growth rate and resistance-curve data, the model was able to predict crack growth during and after the proof load. These tests and analyses indicate that the proof test increases fatigue life; but the beneficial life, after a 1.33 or 1.5 proof, was less than a few hundred cycles.

  5. Can the Lamberts and Lambert Submaximal Cycle Test Indicate Fatigue and Recovery in Trained Cyclists?

    PubMed

    Hammes, Daniel; Skorski, Sabrina; Schwindling, Sascha; Ferrauti, Alexander; Pfeiffer, Mark; Kellmann, Michael; Meyer, Tim

    2016-04-01

    The Lamberts and Lambert Submaximal Cycle Test (LSCT) is a novel test designed to monitor performance and fatigue/recovery in cyclists. Studies have shown the ability to predict performance; however, there is a lack of studies concerning monitoring of fatigue/recovery. In this study, 23 trained male cyclists (age 29 ± 8 y, VO2max 59.4 ± 7.4 mL · min-1 · kg-1) completed a training camp. The LSCT was conducted on days 1, 8, and 11. After day 1, an intensive 6-day training period was performed. Between days 8 and 11, a recovery period was realized. The LSCT consists of 3 stages with fixed heart rates of 6 min at 60% and 80% and 3 min at 90% of maximum heart rate. During the stages, power output and rating of perceived exertion (RPE) were determined. Heart-rate recovery was measured after stage 3. Power output almost certainly (standardized mean difference: 1.0) and RPE very likely (1.7) increased from day 1 to day 8 at stage 2. Power output likely (0.4) and RPE almost certainly (2.6) increased at stage 3. From day 8 to day 11, power output possibly (-0.4) and RPE likely (-1.5) decreased at stage 2 and possibly (-0.1) and almost certainly (-1.9) at stage 3. Heart-rate recovery was likely (0.7) accelerated from day 1 to day 8. Changes from day 8 to day 11 were unclear (-0.1). The LSCT can be used for monitoring fatigue and recovery, since parameters were responsive to a fatiguing training and a following recovery period. However, consideration of multiple LSCT variables is required to interpret the results correctly. PMID:26263163

  6. A tension-torsional fatigue testing apparatus for micro-scale components

    NASA Astrophysics Data System (ADS)

    Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

    2016-01-01

    Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results.

  7. A tension-torsional fatigue testing apparatus for micro-scale components.

    PubMed

    Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

    2016-01-01

    Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results. PMID:26827357

  8. Creep-fatigue interaction in aircraft gas turbine components by simulation and testing at scaled temperatures

    NASA Astrophysics Data System (ADS)

    Sabour, Mohammad Hossein

    components in general, and specifically using thermal scaling for the first time for prototype and model with two different materials. (2) Developing 1-D creep ANSYS macro to study creep effects to get meaningful results for industrial applications of gas turbine blade. (3) Analyzing the curve veering and flattening phenomena in rotating blade at thermal environment, using Lagrange-Bhat method. (4) Simple constitutive models in creep-fatigue interaction are proposed that can predict the lifetime in complicated situations of creep-fatigue, using the pure creep and pure fatigue test data.

  9. Muscular Activity and Fatigue in Lower-Limb and Trunk Muscles during Different Sit-To-Stand Tests

    PubMed Central

    Roldán-Jiménez, Cristina; Bennett, Paul; Cuesta-Vargas, Antonio I.

    2015-01-01

    Sit-to-stand (STS) tests measure the ability to get up from a chair, reproducing an important component of daily living activity. As this functional task is essential for human independence, STS performance has been studied in the past decades using several methods, including electromyography. The aim of this study was to measure muscular activity and fatigue during different repetitions and speeds of STS tasks using surface electromyography in lower-limb and trunk muscles. This cross-sectional study recruited 30 healthy young adults. Average muscle activation, percentage of maximum voluntary contraction, muscle involvement in motion and fatigue were measured using surface electrodes placed on the medial gastrocnemius (MG), biceps femoris (BF), vastus medialis of the quadriceps (QM), the abdominal rectus (AR), erector spinae (ES), rectus femoris (RF), soleus (SO) and the tibialis anterior (TA). Five-repetition STS, 10-repetition STS and 30-second STS variants were performed. MG, BF, QM, ES and RF muscles showed differences in muscle activation, while QM, AR and ES muscles showed significant differences in MVC percentage. Also, significant differences in fatigue were found in QM muscle between different STS tests. There was no statistically significant fatigue in the BF, MG and SO muscles of the leg although there appeared to be a trend of increasing fatigue. These results could be useful in describing the functional movements of the STS test used in rehabilitation programs, notwithstanding that they were measured in healthy young subjects. PMID:26506612

  10. Electric Current Induced Thermomechanical Fatigue Testing of Interconnects

    NASA Astrophysics Data System (ADS)

    Keller, R. R.; Geiss, R. H.; Cheng, Y.-W.; Read, D. T.

    2005-09-01

    We demonstrate the use of electrical methods for evaluating the thermomechanical fatigue properties of patterned aluminum and copper interconnects on silicon-based substrates. Through a careful selection of alternating current frequency and current density, we used controlled Joule heating to simulate in an accelerated manner the type of low frequency thermal stress cycles that an interconnect structure may undergo. Sources of such stressing may include power cycling, energy-saving modes, or application-specific fluctuations, as opposed to stressing at chip operating frequencies. The thermal stresses are caused by differences in thermal expansion properties between the metal and constraining substrate or passivation. Test conditions included a frequency of 100 Hz and current density of 11 - 16 MA/cm2, which led to a cyclic temperature amplitude of approximately 100 K, and corresponding cyclic stress amplitude in excess of 100 MPa for Al-1Si and Cu lines on oxidized silicon. The failure mechanism differs from that observed in direct current electromigration studies, and involves formation of localized plasticity, which causes topography changes on the less-constrained surfaces of the interconnect. Open circuit eventually took place by melting at a region of severely reduced cross-sectional area. In these studies, both Al-1Si and Cu responded to power cycling by deforming in a manner that was highly dependent upon variations in grain size and orientation. Isolated patches of damage appeared early within the confines of individual grains or clusters of grains, as determined by automated electron backscatter diffraction. With increased cycling or with increased current density, the extent of damage became more severe and widespread. We discuss the utility of electrical methods for accelerated testing of mechanical reliability.

  11. High temperature, low-cycle fatigue of copper-base alloys for rocket nozzles. Part 2: Strainrange partitioning and low-cycle fatigue results at 538 deg C

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1976-01-01

    Low-cycle fatigue tests of 1/2 Hard AMZIRC Copper and NARloy Z were performed in argon at 538 C to determine partitioned strain range versus life relationships. Strain-controlled low-cycle fatigue tests of a Zr-Cr-Mg copper-base alloy were also performed. Strain ranges, lower than those employed in previous tests, were imposed in order to extend the fatigue life curve out to approximately 400,000 cycles. An experimental copper alloy and an experimental silver alloy were also studied. Tensile tests were performed in air at room temperature and in argon at 538 C. Strain-controlled low-cycle fatigue tests were performed at 538 C in argon to define the fatigue life over the regime from 300 to 3,000 cycles. For the silver alloy, three additional heat treatments were introduced, and a limited evaluation of the short-term tensile and low-cycle fatigue behavior at 538 C was performed.

  12. Fatigue acceptance test limit criteria for larger diameter rolled thread fasteners

    SciTech Connect

    Kephart, A.R.

    1999-05-19

    This document describes a fatigue lifetime acceptance test criterion by which studs having rolled threads, larger than 1.0 inches (25 mm) in diameter, can be assured to meet minimum quality attributes associated with a controlled rolling process.

  13. Low-cycle thermal fatigue

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1986-01-01

    A state-of-the-art review is presented of the field of thermal fatigue. Following a brief historical review, the concept is developed that thermal fatigue can be viewed as processes of unbalanced deformation and cracking. The unbalances refer to dissimilar mechanisms occurring in opposing halves of thermal fatigue loading and unloading cycles. Extensive data summaries are presented and results are interpreted in terms of the unbalanced processes involved. Both crack initiation and crack propagation results are summarized. Testing techniques are reviewed, and considerable discussion is given to a technique for thermal fatigue simulation, known as the bithermal fatigue test. Attention is given to the use of isothermal life prediction methods for the prediction of thermal fatigue lives. Shortcomings of isothermally-based life prediction methods are pointed out. Several examples of analyses and thermal fatigue life predictions of high technology structural components are presented. Finally, numerous dos and don'ts relative to design against thermal fatigue are presented.

  14. Fatigue Testing of Metallurgically-Bonded EBR-II Superheater Tubes

    SciTech Connect

    T.C. Totemeier; D.M. Wachs; D.L. Porter

    2008-05-01

    Fatigue crack growth and impact tests were performed on 2¼Cr-1Mo steel specimens machined from ex-service Experimental Breeder Reactor – II (EBR-II) superheater duplex tubes. The tubes had been metallurgically bonded with a 100 µm thick Ni layer; the specimens incorporated this bond layer. Impact tests were performed at temperatures from –50 to 400°C; cracks propagating from the V-notch were arrested by delamination at the bond layer for all tests with one exception at –50°C. Fatigue crack growth tests were performed at room temperature in air and at 400°C in air and humid Ar; cracks were grown at varied levels of constant ?K. In all conditions the presence of the Ni bond layer was found to result in a net retardation of growth as the crack passed through the layer. The mechanism of retardation was identified as a disruption of crack planarity and uniformity after passing through the porous bond layer. Full crack arrest was only observed in a single test performed at near-threshold ?K level (12 MPa?m) at 400°C. In this case the crack tip was blunted by oxidation of the base steel at the steel-nickel interface.

  15. Associations of fatigue from mid to late life with physical performance and strength in early old age: Results from a British prospective cohort study

    PubMed Central

    Mänty, Minna; Kuh, Diana; Cooper, Rachel

    2015-01-01

    OBJECTIVE To examine associations of fatigue in mid and later life with physical performance and strength in early old age. METHODS Data on approximately 1800 men and women from the UK Medical Research Council National Survey of Health and Development with data on fatigue at ages 43 and 60-64 years were used. Fatigue was defined as perceived tiredness and was assessed prospectively at ages 43 and 60-64. At both ages, participants were categorized as having no, occasional or frequent fatigue. Physical performance and strength were measured at age 60-64 using four objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests. RESULTS There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise and TUG performance at 60-64 years. Furthermore, individuals reporting frequent fatigue at both ages had weaker grip strength (β -4.09 kg, 95% CI -6.71, -1.48), and slower chair rise (β -4.65 rep./min, 95% CI -6.65, -2.64) and TUG (β -4.22 cm/s, 95% CI -12.16, -2.28) speeds when compared to those who reported no fatigue at both time points. These associations were robust and were maintained after adjustment for a range of covariates including physical activity and health status. CONCLUSIONS Reports of frequent fatigue were associated with poorer physical performance in early old age, especially if sustained from mid to later life. These findings indicate that it is not just fatigue but fatigue sustained across adulthood that has implications for later life functioning. PMID:26176776

  16. Reversal bending fatigue test system for investigating vibration integrity of spent nuclear fuel during transportation

    SciTech Connect

    Wang, Jy -An; Wang, Hong; Bevard, Bruce Balkcom; Howard, Rob L.; Flanagan, Michelle E.

    2014-09-01

    Transportation packages for spent nuclear fuel (SNF) must meet safety requirements under normal and accident conditions as specified by federal regulations. During transportation, SNF experiences unique conditions and challenges to cladding integrity due to the vibrational and impact loading during road or rail shipment. Oak Ridge National Laboratory (ORNL) has been developing testing capabilities that can be used to improve the understanding of the impacts on SNF integrity due to vibration loading, especially for high burn-up SNF in normal transportation operation conditions. This information can be used to meet the nuclear industry and U.S.Nuclear Regulatory Commission needs in the area of safety and security of SNF storage and transportation operations. The ORNL developed test system can perform reversal bending fatigue testing to evaluate both the static and dynamic mechanical response of SNF rods under simulated loads. The testing apparatus is also designed to meet the challenges of hot cell operation, including remote installation and detachment of the SNF test specimen, in situ test specimen deformation measurement, and implementation of a driving system suitable for use in a hot cell. The system contains a U frame set-up equipped with uniquely designed grip rigs to protect the SNF rod sample and to ensure valid test results, and uses three specially designed linear variable differential transformers to obtain the in situ curvature measurement. A variety of surrogate test rods have been used to develop and calibrate the test system as well as in performing a series of systematic cyclic fatigue tests. The surrogate rods include stainless steel (SS) cladding, SS cladding with cast epoxy and SS cladding with alumina pellet inserts simulating fuel pellets. Testing to date has shown that the interface bonding between the SS cladding and the alumina pellets has a significant impact on the bending response of the test rods as well as their fatigue strength. The

  17. Reversible Bending Fatigue Test System for Investigating Vibration Integrity of Spent Nuclear Fuel during Transportation

    SciTech Connect

    Wang, Jy-An John; Wang, Hong; Bevard, Bruce Balkcom; Howard, Rob L; Flanagan, Michelle

    2013-01-01

    Transportation packages for spent nuclear fuel (SNF) must meet safety requirements under normal and accident conditions as specified by federal regulations. During transportation, SNF experiences unique conditions and challenges to cladding integrity due to the vibrational and impact loading during road or rail shipment. Oak Ridge National Laboratory (ORNL) has been developing testing capabilities that can be used to improve the understanding of the impacts on SNF integrity due to vibration loading, especially for high burn-up SNF in normal transportation operation conditions. This information can be used to meet the nuclear industry and U.S. Nuclear Regulatory Commission needs in the area of safety and security of spent nuclear fuel storage and transport operations. The ORNL developed test system can perform reversible-bending fatigue testing to evaluate both the static and dynamic mechanical response of SNF rods under simulated loads. The testing apparatus is also designed to meet the challenges of hot-cell operation, including remote installation and detachment of the SNF test specimen, in-situ test specimen deformation measurement, and implementation of a driving system suitable for use in a hot cell. The system contains a U-frame set-up equipped with uniquely designed grip rigs, to protect SNF rod and to ensure valid test results, and use of 3 specially designed LVDTs to obtain the in-situ curvature measurement. A variety of surrogate test rods have been used to develop and calibrate the test system as well as in performing a series of systematic cyclic fatigue tests. The surrogate rods include stainless steel (SS) cladding, SS cladding with cast epoxy, and SS cladding with alumina pellets inserts simulating fuel pellets. Testing to date has shown that the interface bonding between the SS cladding and the alumina pellets has a significant impact on the bending response of the test rods as well as their fatigue strength. The failure behaviors observed from

  18. Reversal bending fatigue test system for investigating vibration integrity of spent nuclear fuel during transportation

    DOE PAGESBeta

    Wang, Jy -An; Wang, Hong; Bevard, Bruce Balkcom; Howard, Rob L.; Flanagan, Michelle E.

    2014-09-01

    Transportation packages for spent nuclear fuel (SNF) must meet safety requirements under normal and accident conditions as specified by federal regulations. During transportation, SNF experiences unique conditions and challenges to cladding integrity due to the vibrational and impact loading during road or rail shipment. Oak Ridge National Laboratory (ORNL) has been developing testing capabilities that can be used to improve the understanding of the impacts on SNF integrity due to vibration loading, especially for high burn-up SNF in normal transportation operation conditions. This information can be used to meet the nuclear industry and U.S.Nuclear Regulatory Commission needs in the areamore » of safety and security of SNF storage and transportation operations. The ORNL developed test system can perform reversal bending fatigue testing to evaluate both the static and dynamic mechanical response of SNF rods under simulated loads. The testing apparatus is also designed to meet the challenges of hot cell operation, including remote installation and detachment of the SNF test specimen, in situ test specimen deformation measurement, and implementation of a driving system suitable for use in a hot cell. The system contains a U frame set-up equipped with uniquely designed grip rigs to protect the SNF rod sample and to ensure valid test results, and uses three specially designed linear variable differential transformers to obtain the in situ curvature measurement. A variety of surrogate test rods have been used to develop and calibrate the test system as well as in performing a series of systematic cyclic fatigue tests. The surrogate rods include stainless steel (SS) cladding, SS cladding with cast epoxy and SS cladding with alumina pellet inserts simulating fuel pellets. Testing to date has shown that the interface bonding between the SS cladding and the alumina pellets has a significant impact on the bending response of the test rods as well as their fatigue strength

  19. Correlation of magnetic perturbation inspection data with rolling element bearing fatigue results

    NASA Technical Reports Server (NTRS)

    Parker, R. J.

    1973-01-01

    A magnetic perturbation technique was used to nondestructively detect subsurface nonmetallic inclusions in the inner races of 207-size, deep groove ball bearings. The bearings were fatigue tested at 2750 rpm under a radial load of. The inner races were subsequently sectioned at fatigue spall locations and at magnetic perturbation signal locations. Analyses of the data indicated good correlation between magnetic perturbation signals and inclusion size and location. Exclusion of those bearings that had significant magnetic perturbation signals did not alter the statistical life of the bearings.

  20. Fatigue life prediction of liquid rocket engine combustor with subscale test verification

    NASA Astrophysics Data System (ADS)

    Sung, In-Kyung

    Reusable rocket systems such as the Space Shuttle introduced a new era in propulsion system design for economic feasibility. Practical reusable systems require an order of magnitude increase in life. To achieve this improved methods are needed to assess failure mechanisms and to predict life cycles of rocket combustor. A general goal of the research was to demonstrate the use of subscale rocket combustor prototype in a cost-effective test program. Life limiting factors and metal behaviors under repeated loads were surveyed and reviewed. The life prediction theories are presented, with an emphasis on studies that used subscale test hardware for model validation. From this review, low cycle fatigue (LCF) and creep-fatigue interaction (ratcheting) were identified as the main life limiting factors of the combustor. Several life prediction methods such as conventional and advanced viscoplastic models were used to predict life cycle due to low cycle thermal stress, transient effects, and creep rupture damage. Creep-fatigue interaction and cyclic hardening were also investigated. A prediction method based on 2D beam theory was modified using 3D plate deformation theory to provide an extended prediction method. For experimental validation two small scale annular plug nozzle thrusters were designed, built and tested. The test article was composed of a water-cooled liner, plug annular nozzle and 200 psia precombustor that used decomposed hydrogen peroxide as the oxidizer and JP-8 as the fuel. The first combustor was tested cyclically at the Advanced Propellants and Combustion Laboratory at Purdue University. Testing was stopped after 140 cycles due to an unpredicted failure mechanism due to an increasing hot spot in the location where failure was predicted. A second combustor was designed to avoid the previous failure, however, it was over pressurized and deformed beyond repair during cold-flow test. The test results are discussed and compared to the analytical and numerical

  1. A Comparison of Zero Mean Strain Rotating Beam Fatigue Test Methods for Nitinol Wire

    NASA Astrophysics Data System (ADS)

    Norwich, Dennis W.

    2014-07-01

    Zero mean strain rotating beam fatigue testing has become the standard for comparing the fatigue properties of Nitinol wire. Most commercially available equipment consists of either a two-chuck or a chuck and bushing system, where the wire length and center-to-center axis distance determine the maximum strain on the wire. For the two-chuck system, the samples are constrained at either end of the wire, and both chucks are driven at the same speed. For the chuck and bushing system, the sample is constrained at one end in a chuck and rides freely in a bushing at the other end. These equivalent systems will both be herein referred to as Chuck-to-Chuck systems. An alternate system uses a machined test block with a specific radius to guide the wire at a known strain during testing. In either system, the test parts can be immersed in a temperature-controlled fluid bath to eliminate any heating effect created in the specimen due to dissipative processes during cyclic loading (cyclic stress induced the formation of martensite) Wagner et al. ( Mater. Sci. Eng. A, 378, p 105-109, 1). This study will compare the results of the same starting material tested with each system to determine if the test system differences affect the final results. The advantages and disadvantages of each system will be highlighted and compared. The factors compared will include ease of setup, operator skill level required, consistency of strain measurement, equipment test limits, and data recovery and analysis. Also, the effect of test speed on the test results for each system will be investigated.

  2. Comparison of uncertainty in fatigue tests obtained by the Monte Carlo method in two softwares

    NASA Astrophysics Data System (ADS)

    Trevisan, Lisiane; Kapper Fabricio, Daniel Antonio; Reguly, Afonso

    2016-07-01

    The Supplement 1 to the “Guide to the expression of uncertainty in measurement” indicates the Monte Carlo method for calculating the expanded measurement uncertainty. The objective of this work is to compare the measurement uncertainty values obtained via Monte Carlo method through two commercial softwares (Matlab® and Crystal Ball®) for the parameter ‘adjusted strain’, obtained from fatigue tests. Simulations were carried out using different number of iterations and different levels of confidence. The results showed that there are short differences between the measurement uncertainty values generated by different software.

  3. MER ARA pyroshock test results

    NASA Technical Reports Server (NTRS)

    Chang, Kurng Y.

    2004-01-01

    This paper presents the shock test results achieved in the MER ARA/brush motor pyroshock qualification. The results of MER flight system pyrofiring tests in comparison with the ARA shock test requirements are discussed herein. Alternate test methods were developed in an effort to qualify the critical MER equipment for adequate performance in the actual flight pyroshock condition.

  4. A computer-controlled automated test system for fatigue and fracture testing

    SciTech Connect

    Nanstad, R.K.; Alexander, D.J.; Swain, R.L.; Hutton, J.T.; Thomas, D.L.

    1989-01-01

    A computer-controlled system consisting of a servohydraulic test machine, an in-house designed test controller, and a desktop computer has been developed for performing automated fracture toughness and fatigue crack growth testing both in the laboratory and in hot cells for remote testing of irradiated specimens. Both unloading compliance and dc-potential drop can be used to monitor crack growth. The test controller includes a dc-current supply programmer, a function generator for driving the servohydraulic test machine to required test outputs, five measurement channels (each consisting of low-pass filter, track/hold amplifier, and 16-bit analog-to-digital converter), and digital logic for various control and data multiplexing functions. The test controller connects to the computer via a 16-bit wide photo-isolated bidirectional bus. The computer, a Hewlett-Packard series 200/300, inputs specimen and test parameters from the operator, configures the test controller, stores test data from the test controller in memory, does preliminary analysis during the test, and records sensor calibrations, specimen and test parameters, and test data on flexible diskette for later recall and analysis with measured initial and final crack length information. During the test, the operator can change test parameters as necessary. 24 refs., 6 figs.

  5. Fracture resistance of Zr-Nb alloys under low-cycle fatigue tests

    NASA Astrophysics Data System (ADS)

    Nikulin, S. A.; Rozhnov, A. B.; Gusev, A. Yu.; Nechaykina, T. A.; Rogachev, S. O.; Zadorozhnyy, M. Yu.

    2014-03-01

    Comparative low-cycle fatigue tests of small-scale specimens cut from the cladding tubes of E110, E125, E110opt zirconium alloys at temperatures of 25 and 350 °C using a dynamic mechanical analyzer have been carried out. It is shown that the limited cycles fatigue stress for all alloys is 50% less at temperature of 350 °C comparing to 25 °C. Besides it has been revealed that the limited cycles fatigue stress increases with increasing the strength of zirconium alloy.

  6. Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA's High Temperature, High Speed Turbine Seal Test Rig

    NASA Technical Reports Server (NTRS)

    Delgado, Irebert R.; Steinetz, Bruce M.; Rimnac, Clare M.; Lewandowski, John J.

    2008-01-01

    The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA s Turbine Seal Test Facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of the NASA disk bolt holes is found to be 367 cycles at a crack depth of 0.501 mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032 cycles at a crack depth of 0.501 mm. Eddy-current inspections are suggested starting at 665 cycles since eddy current detection thresholds are currently at 0.381 mm. Inspection intervals are recommended every 50 cycles when operated at maximum operating conditions.

  7. Characterization of wear debris generated in accelerated rolling-element fatigue tests

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Parker, R. J.

    1978-01-01

    A ferrographic analysis was used to determine the types and quantities of wear debris generated during accelerated rolling contact fatigue tests. The five-ball rolling contact fatigue tester was used. Ball specimens were made of a corrosion resistant, high-temperature bearing steel. The lubricant was a superrefined naphthenic mineral oil. Conditions included a maximum Hertz stress of 5.52 10 to the 9th power Pa and a shaft speed of 10,000 rpm. Four types of wear debris were observed: (1) normal rubbing wear particles, (2) fatigue microspall particles, (3) spheres, and (4) friction polymer deposits. The characterization of wear debris as a function of time was of limited use in predicting fatigue failures in these accelerated tests.

  8. The Boeing 747 fatigue integrity program

    NASA Technical Reports Server (NTRS)

    Spencer, M. M.

    1972-01-01

    The fatigue integrity program which was established to insure economic operations and to provide foundation data for inspection and maintenance is discussed. Significant features of the 747 fatigue integrity program are: (1) fatigue analyses which are continually updated to reflect design changes, fatigue test results, and static and flight load survey measurements; (2) material selection and detail design by using initial fatigue analyses, service experience, and testing; and (3) fatigue testing to check detail design quality and to verify the analyses, culminated by the test of a structurally complete airframe. Fatigue stress analyses were performed with the aid of experimental as well as analytical procedures. Extensive application was made of the stress severity factor, developed at Boeing, for evaluating peak stresses in complex joints. A frame of reference was established by families of structural fatigue performance curves (S-N curves) encompassing the range of materials and fatigue qualities anticipated for the 747 airplane design.

  9. Design and evaluation of a 3 million DN series-hybrid thrust bearing. [stability tests and fatigue tests

    NASA Technical Reports Server (NTRS)

    Scibbe, H. W.; Winn, L. W.; Eusepi, M.

    1976-01-01

    The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation.

  10. Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1989-01-01

    A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

  11. Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1988-01-01

    A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

  12. A unique elevated-temperature tension-torsion fatigue test rig

    NASA Astrophysics Data System (ADS)

    Jordan, E. H.; Chan, C. T.

    1987-06-01

    A unique tension-torsion fatigue test set up is described that allows strain-controlled tests at temperatures exceeding 649 C. The machine uses a large die set as a load frame resulting in lower cost and superior parallel positioning of the crossheads. Disposable weld-on grips were found to be cost effective for elevated-temperature testing. A new extensometer using commercially available capacitance probes was developed which can operate at the elevated temperature without cooling. Capacitance ring probes were utilized in an attempt to measure through-thickness strains. The characteristic behavior of the ring probes is discussed. Design modifications needed to make a successful measurement of through-thickness strains at elevated temperatures are presented.

  13. Fatigue life and performance testing of hybrid ceramic ball bearings

    SciTech Connect

    Chiu, Y.P.; Prason, P.K.; Dezzani, M.

    1996-03-01

    Hybrid ceramic ball bearings are finding increased applications in machine tool spindles and aerospace vehicles. Results of three types of testing hybrid ceramic ball bearing are presented and discussed. The first is the classical endurance testing of highly loaded hybrid bearings with good lubrication. The second is the endurance test of hybrid nitrided bearings after running in a contaminated lubricant which caused dented raceways. The third is the high-speed performance testing of spindle bearings lubricated with grease or an oil-air mixture. Recent material development, bearing temperature at high-speed and reliability considerations are discussed. 14 refs., 9 fig., 4 tab.

  14. Vacuum thermal-mechanical fatigue testing of two iron base high temperature alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.

    1974-01-01

    Ultrahigh vacuum elevated temperature low cycle fatigue and thermal fatigue tests of 304 stainless steel and A-286 alloy have shown significant effects of frequency and combined temperature-strain cycling on fatigue life. At constant temperature, the cyclic life of both alloys was lower at lower frequencies. Combined temperature-strain cycling reduced fatigue life with respect to isothermal life at the maximum temperature of the thermal cycle. Life reductions with in-phase thermal cycling (tension at high temperature, compression at low temperature) were attributed to grain boundary cavitation caused by unreversed tensile grain boundary sliding. The proposed mechanism for out-of-phase cavity generation involved accumulation of unreversed compressive grain boundary displacements which could not be geometrically accomodated by intragranular deformation in the low-ductility A-286 alloy.

  15. Full-scale fatigue tests of CX-100 wind turbine blades. Part II: analysis

    NASA Astrophysics Data System (ADS)

    Taylor, Stuart G.; Jeong, Hyomi; Jang, Jae Kyeong; Park, Gyuhae; Farinholt, Kevin M.; Todd, Michael D.; Ammerman, Curtt M.

    2012-04-01

    This paper presents the initial analysis results of several structural health monitoring (SHM) methods applied to two 9- meter CX-100 wind turbine blades subjected to fatigue loading at the National Renewable Energy Laboratory's (NREL) National Wind Technology Center (NWTC). The first blade was a pristine blade, manufactured to standard CX-100 design specifications. The second blade was manufactured for the University of Massachusetts, Lowell (UMass), with intentional simulated defects within the fabric layup. Each blade was instrumented with a variety of sensors on its surface. The blades were subject to harmonic excitation at their first natural frequency with steadily increasing loading until ultimately reaching failure. Data from the sensors were collected between and during fatigue loading sessions. The data were measured at multi-scale frequency ranges using a variety of data acquisition equipment, including off-the-shelf systems and prototype data acquisition hardware. The data were analyzed to identify fatigue damage initiation and to assess damage progression. Modal response, diffuse wave-field transfer functions in time and frequency domains, and wave propagation methods were applied to assess the condition of the turbine blade. The analysis methods implemented were evaluated in conjunction with hardware-specific performance for their efficacy in enabling the assessment of damage progression in the blade. The results of this assessment will inform the selection of specific data to be collected and analysis methods to be implemented for a CX-100 flight test to be conducted in collaboration with Sandia National Laboratory at the U.S. Department of Agriculture's (USDA) Conservation and Production Research Laboratory (CPRL) in Bushland, Texas.

  16. Ambient temperature fatigue tests of elements of an actively cooled honeycomb sandwich structural panel

    NASA Technical Reports Server (NTRS)

    Sharpe, E. L.; Elber, W.

    1977-01-01

    Elements of an actively cooled structural panel for a hypersonic aircraft have been investigated for fatigue characteristics. The study involved a bonded honeycomb sandwich panel with d-shaped coolant tubes. The curved portion of these tubes was embedded in the honeycomb, and the flat portion was bonded or soldered to the inner surface of the outer skin. The elements examined were two plain skin specimens (aluminum alloy); two specimens with skins attached to manifolds and tubes (one specimen was bonded, the other soldered); and a specimen representative of a corner section of the complete cooled sandwich. Sinusoidal loads were applied to all specimens. The honeycomb sandwich specimen was loaded in both tension and compression; the other specimens were loaded in tension only. The cooling tubes were pressurized with oil throughout the fatigue tests. The most significant results of these tests follow: All specimens exceeded their design life of 20,000 cycles without damage. Crack growth rates obtained in the plain skin specimens were used to determine the crack growth characteristics of aluminum alloy. Cracks in skins either bonded or soldered to cooling tubes propagated past the tubes without penetration. The coolant tubes served as crack arresters and temporarily stopped crack growth when a crack reached a tube-skin interface. The honeycomb core demonstrated that it could contain leakage from a tube.

  17. Implementation of a Biaxial Resonant Fatigue Test Method on a Large Wind Turbine Blade

    SciTech Connect

    Snowberg, D.; Dana, S.; Hughes, S.; Berling, P.

    2014-09-01

    A biaxial resonant test method was utilized to simultaneously fatigue test a wind turbine blade in the flap and edge (lead-lag) direction. Biaxial resonant blade fatigue testing is an accelerated life test method utilizing oscillating masses on the blade; each mass is independently oscillated at the respective flap and edge blade resonant frequency. The flap and edge resonant frequency were not controlled, nor were they constant for this demonstrated test method. This biaxial resonant test method presented surmountable challenges in test setup simulation, control and data processing. Biaxial resonant testing has the potential to complete test projects faster than single-axis testing. The load modulation during a biaxial resonant test may necessitate periodic load application above targets or higher applied test cycles.

  18. Influence of test specimen fabrication method and cross-section configuration on tension-tension fatigue life of PMMA bone cement.

    PubMed

    Sheafi, E M; Tanner, K E

    2015-11-01

    Different cyclic loading modes have been used in in vitro fatigue studies of PMMA bone cement. It is unclear which loading mode is most appropriate from the perspective of the in vivo loading experienced by the cement in a cemented arthroplasty. Also, in different in vitro fatigue studies, different test specimen configurations have been used. The present work considers the influence of test specimen fabrication method (direct moulding vs moulding followed by machining) and cross-section shape (rectangular vs circular) on the tension-tension fatigue performance of two bone cement brands (SmartSet GHV and CMW1), under force control conditions. Two trends were consistent: 1) for each of the cements, for moulded specimens, a longer fatigue life was obtained with circular cross-sectioned specimens and, 2) for either rectangular or circular CMW1 specimens, a longer fatigue life was obtained using machined specimens. A comparison of the present results to those reported in our previous work on fully-reversed tension-compression loading under force control showed that, regardless of the test specimen fabrication method or cross-section configuration used, the fatigue life was considerably shorter under tension-compression than tension-tension loading. This finding highlights the fact that the presence of the compression portion in the loading cycle accelerates fatigue failure. PMID:26295451

  19. Indentation hardness: A simple test that correlates with the dissipated-energy predictor for fatigue-life in bovine pericardium membranes for bioprosthetic heart valves.

    PubMed

    Tobaruela, Almudena; Rojo, Francisco Javier; García Paez, José María; Bourges, Jean Yves; Herrero, Eduardo Jorge; Millán, Isabel; Alvarez, Lourdes; Cordon, Ángeles; Guinea, Gustavo V

    2016-08-01

    The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue tests were performed in vitro on 24 pericardium specimens cut in a root-to-apex direction. The specimens were subjected to a maximum stress of 1MPa in blocks of 10, 25, 50, 100, 250, 500, 1000 and 1500 cycles. By means of a modified Shore A hardness test procedure, the hardness of the specimen was measured before and after fatigue tests. Results showed a significant correlation of such hardness with fatigue performance and with the energy dissipated in the first cycle of fatigue, a predictor of pericardium durability. The study showed indentation hardness as a simple and reliable indicator of mechanical performance, one which could be easily implemented in improving tissue selection. PMID:26849027

  20. A data acquisition and control program for axial-torsional fatigue testing

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Bonacuse, Peter J.

    1989-01-01

    A computer program was developed for data acquisition and control of axial-torsional fatigue experiments. The multitasked, interrupt-driven program was written in Pascal and Assembly. This program is capable of dual-channel control and six-channel data acquisition. It can be utilized to perform inphase and out-of-phase axial-torsional isothermal fatigue or deformation experiments. The program was successfully used to conduct inphase axial-torsional fatigue experiments on 304 stainless steel at room temperature and on Hastelloy X at 800 C. The details of the software and some of the results generated to date are presented.

  1. Stiffness reductions during tensile fatigue testing of graphite/epoxy angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Odom, E. M.; Adams, D. F.

    1982-01-01

    Tensile fatigue data was generated under carefully controlled test conditions. A computerized data acquisition system was used to permit the measurement of dynamic modulus without interrupting the fatigue cycling. Two different 8-ply laminate configurations, viz, + or - 45 (2s) and + or - 67.5 (2s), of a T300/5208 graphite/epoxy composite were tested. The + or - 45 (2s) laminate did exhibit some modulus decay, although there was no well-defined correlation with applied stress level or number of cycles. The + or - 67.5 (2s) laminate did not exhibit any measurable modulus decay. Secondary effects observed included a small but distinct difference between modulus as measured statically and dynamically, a slight recovery of the modulus decay after a test interruption, and a significant viscoelastic (creep) response of the + or - 45 (2s) laminate during fatigue testing.

  2. Evaluation of the New B-REX Fatigue Testing System for Multi-Megawatt Wind Turbine Blades: Preprint

    SciTech Connect

    White, D.; Musial, W.; Engberg, S.

    2004-12-01

    The National Renewable Energy Laboratory (NREL) recently developed a new hybrid fatigue testing system called the Blade Resonance Excitation (B-REX) test system. The new system uses 65% less energy to test large wind turbine blades in half the time of NREL's dual-axis forced-displacement test method with lower equipment and operating costs. The B-REX is a dual-axis test system that combines resonance excitation with forced hydraulic loading to reduce the total test time required while representing the operating strains on the critical inboard blade stations more accurately than a single-axis test system. The analysis and testing required to fully implement the B-REX was significant. To control unanticipated blade motion and vibrations caused by dynamic coupling between the flap, lead-lag, and torsional directions, we needed to incorporate additional test hardware and control software. We evaluated the B-REX test system under stable operating conditions using a combination of various sensors. We then compared our results with results from the same blade, tested previously using NREL's dual-axis forced-displacement test method. Experimental results indicate that strain levels produced by the B-REX system accurately replicated the forced-displacement method. This paper describes the challenges we encountered while developing the new blade fatigue test system and the experimental results that validate its accuracy.

  3. Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

    PubMed Central

    Feng, Aihen; Chen, Daolun; Li, Cheng; Gu, Xijia

    2010-01-01

    We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor. PMID:22163621

  4. DIC-aided biaxial fatigue tests of a 304L steel

    NASA Astrophysics Data System (ADS)

    Poncelet, M.; Barbier, G.; Raka, B.; Courtin, S.; Desmorat, R.; Le-Roux, J. C.; Vincent, L.

    2010-06-01

    Several biaxial fatigue tests are conducted up to 106 cycles at room temperature in the context of a collaboration LMT-Cachan / EDF / AREVA / SNECMA / CEA. Malteses cross specimens of 304L steel, designed to initiate crack in the bulk, are loaded by a triaxial testing machine. A Digital Image Correlation technique is used to measure strain during loading and detect crack initiation early. A special optical assembly and a stroboscopic sampling method are set up in this purpose. Several types of loadings are performed: equibiaxial with a loading ratio R = 0.1, equibiaxial with loading ratio R = -1, pseudo uniaxial (cyclic loading at R= 0.1 in one direction and constant loading in the other). First results are commented.

  5. A new method for dual-axis fatigue testing of large wind turbine blades using resonance excitation and spectral loading

    NASA Astrophysics Data System (ADS)

    White, Darris L.

    The demand for cost effective renewable energy sources has resulted in the continual refinement of modern wind turbine designs. These refinements generally result in larger wind turbines and wind turbine blades. In order to reduce maintenance expenses, and improve quality and reliability, each new blade design must be subjected to a high cycle fatigue test. With blades expected to soon reach 70 meters in length, traditional fatigue test systems and methods are becoming less practical. Additionally, the relationship between the flap and lead-lag bending moments has not been well understood. This work explores the accuracy of current test methods compared to service loads, presents a new method for fatigue testing larger blades and experimentally validates the analysis. A dynamic model of a generic wind turbine blade and test system has been developed to evaluate the strain profiles during testing, evaluate control strategies and optimize the test accuracy. The relationship between the flap and lead-lag strains resulting from service bending moments has been analyzed. A load spectrum based on the relationship between the flap and lead-lag loads has been developed and compared to traditional test conditions. The effect of using the load spectrum on the test system stability has been analyzed and a new state-space controller has been designed. A 3-D finite element model of a generic wind turbine blade has been used to evaluate the damage accumulation for current test load conditions and the proposed load spectrum. A nonlinear damage accumulation model has been derived to evaluate the effects of load sequencing. Additionally, a new method for applying the fatigue loads to the blades has been developed and implemented. A system that applies a harmonic force at the resonance frequency of the blade in the flap direction has been designed. The new system will reduce the costs and time associated with performing a fatigue test on wind turbine blades. The new system is also

  6. Misleading biochemical laboratory test results

    PubMed Central

    Nanji, Amin A.

    1984-01-01

    This article reviews the general and specific factors that interfere with the performance of common biochemical laboratory tests and the interpretation of their results. The clinical status of the patient, drug interactions, and in-vivo and in-vitro biochemical interactions and changes may alter the results obtained from biochemical analysis of blood constituents. Failure to recognize invalid laboratory test results may lead to injudicious and dangerous management of patients. PMID:6375845

  7. Biomechanical fatigue analysis of an advanced new carbon fiber/flax/epoxy plate for bone fracture repair using conventional fatigue tests and thermography.

    PubMed

    Bagheri, Zahra S; El Sawi, Ihab; Bougherara, Habiba; Zdero, Radovan

    2014-07-01

    The current study is part of an ongoing research program to develop an advanced new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite with a “sandwich structure” as a substitute for metallic materials for orthopedic long bone fracture plate applications. The purpose of this study was to assess the fatigue properties of this composite, since cyclic loading is one of the main types of loads carried by a femur fracture plate during normal daily activities. Conventional fatigue testing, thermographic analysis, and scanning electron microscopy (SEM) were used to analyze the damage progress that occurred during fatigue loading. Fatigue strength obtained using thermography analysis (51% of ultimate tensile strength) was confirmed using the conventional fatigue test (50–55% of ultimate tensile strength). The dynamic modulus (E⁎) was found to stay almost constant at 47 GPa versus the number of cycles, which can be related to the contribution of both flax/epoxy and CF/epoxy laminae to the stiffness of the composite. SEM images showed solid bonding at the CF/epoxy and flax/epoxy laminae, with a crack density of only 0.48% for the plate loaded for 2 million cycles. The current composite plate showed much higher fatigue strength than the main loads experienced by a typical patient during cyclic activities; thus, it may be a potential candidate for bone fracture plate applications. Moreover, the fatigue strength from thermographic analysis was the same as that obtained by the conventional fatigue tests, thus demonstrating its potential use as an alternate tool to rapidly evaluate fatigue strength of composite biomaterials. PMID:24918250

  8. MITG test procedure and results

    SciTech Connect

    Eck, M.B.; Mukunda, M.

    1983-01-01

    Elements and modules for Radioisotope Thermoelectric Generator have been performance tested since the inception of the RTG program. These test articles seldom resembled flight hardware and often lacked adequate diagnostic instrumentation. Because of this, performance problems were not identified in the early stage of program development. The lack of test data in an unexpected area often hampered the development of a problem solution. A procedure for conducting the MITG Test was developed in an effort to obtain data in a systematic, unambiguous manner. This procedure required the development of extensive data acquisition software and test automation. The development of a facility to implement the test procedure, the facility hardware and software requirements, and the results of the MITG testing are the subject of this paper.

  9. The Toronto Hospital Alertness Test scale: relationship to daytime sleepiness, fatigue, and symptoms of depression and anxiety

    PubMed Central

    Shahid, Azmeh; Chung, Sharon A; Maresky, Lance; Danish, Affan; Bingeliene, Arina; Shen, Jianhua; Shapiro, Colin M

    2016-01-01

    Objective The Toronto Hospital Alertness Test (THAT) scale was designed to measure alertness, defined as the capacity of the mind to respond appropriately to external and internal stimuli. The present study’s aim is to determine normative values of alertness on the THAT and to explore the relationship among excessive daytime sleepiness, fatigue, depressive symptoms, and alertness. Methods Normative data were collected from 60 healthy males and females. To explore the relationship among alertness, daytime sleepiness, fatigue, depression, and anxiety, data were collected from charts of sleep clinic patients. All study subjects completed measures for fatigue, sleepiness, depressive symptoms, and anxiety. Results The average score on the THAT was 34.9±7.2 (range 22–50) for the control group. The cutoff score for the THAT, indicative of clinically significant reduced alertness, was determined to be ≤20.5 (mean −2 SD). THAT alertness scores were found to be modestly, significantly, and negatively correlated with fatigue levels (r=−0.39, P<0.001), depressive symptoms (r=−0.53, P<0.001), and anxiety symptoms (r=−0.41, P<0.001). No correlations were found between alertness levels and daytime sleepiness. Regression analyses revealed a significant model (F=19.9, P<0.001, adjusted R2=0.35) with depressive symptoms (P<0.001) and fatigue (P=0.006) emerging as the only significant predictors of scores on the THAT. Conclusion The findings of this study support that sleepiness is not the same as poor alertness. Depressive symptoms and fatigue, but not sleepiness, were found to have a strong and significant impact on levels of alertness. This is the first study to link poor alertness to depressive symptoms. PMID:26855603

  10. State Test Results Are Predictable

    ERIC Educational Resources Information Center

    Tienken, Christopher H.

    2014-01-01

    Out-of-school, community demographic and family-level variables have an important influence on student achievement as measured by large-scale standardized tests. Studies described here demonstrated that about half of the test score is accounted for by variables outside the control of teachers and school administrators. The results from these…

  11. Procedures for evaluating filament cracking during fatigue testing of Nb3Sn strand

    NASA Astrophysics Data System (ADS)

    Sheth, M. K.; Lee, Peter; McRae, D. M.; Walsh, Robert; Starch, W. L.; Jewell, M. C.; Devred, A.; Larbalestier, D. C.

    2012-06-01

    In Tokamak fusion reactors, such as ITER, superconducting strands are subjected to repeated Lorentz force loading and unloading which may degrade performance over time. The Cu matrix which surrounds the brittle Nb3Sn filaments allows the possibility of some elastic-plastic deformation that can initiate filament cracking. We seek to understand if there are strand design variables that might ameliorate such degradation but before being able to do such experiments, we need to establish procedures that can unambiguously detect the cracking caused by loading, rather than by subsequent metallographic examination. Here we make a first report of our procedures after fatigue testing at 77K. Filament crack densities were quantified from large montages covering ≈20 mm length of strand. Three types of cracks were present. The most common were cracks transverse to the filament axis adjacent to voids. Cracks away from voids were of low density until close to the fracture strain. A third kind of crack which generally initiates at unreacted Nb cores of filaments extends radially and in the plane parallel to the wire axis. Example results on one bronze strand fatigued for 1000 loading cycles at axial strains from 0.4% to 1.14% are shown.

  12. Fatigue evaluation of composite-reinforced integrally stiffened metal panels: Summary

    NASA Technical Reports Server (NTRS)

    Dumesnil, C. E.

    1973-01-01

    The fatigue and fail-safe behavior of composite-reinforced, integrally stiffened metal panels was investigated. Test results consisting of conventional fatigue lives, fatigue-crack propagation rates, and residual static strength are presented and discussed.

  13. Method for testing shell materials for fatigue crack resistance under biaxial bending

    SciTech Connect

    Esiev, T.S.; Basiev, K.D.; Steklov, O.I. |

    1995-10-01

    A method for testing shell materials for fatigue crack resistance is proposed. A stressed state typically occurring in shells is simulated on a specimen with a surface notch by subjecting it to biaxial surface tension. The time of fatigue crack generation or the crack propagation rate is used to evaluate the crack resistance of a material. Cross-shaped test specimens cut out of a real shell had a size and a loading scheme that made it possible to vary the biaxial stress ratio over the range of 0.5 {<=} {lambda} {<=} 1.

  14. Inspection and monitoring of wind turbine blade-embedded wave defects during fatigue testing

    SciTech Connect

    Niezrecki, Christopher; Avitabile, Peter; Chen, Julie; Sherwood, James; Lundstrom, Troy; LeBlanc, Bruce; Hughes, Scott; Desmond, Michael; Beattie, Alan; Rumsey, Mark; Klute, Sandra M.; Pedrazzani, Renee; Werlink, Rudy; Newman, John

    2014-05-20

    The research we present in this article focuses on a 9-m CX-100 wind turbine blade, designed by a team led by Sandia National Laboratories and manufactured by TPI Composites Inc. The key difference between the 9-m blade and baseline CX-100 blades is that this blade contains fabric wave defects of controlled geometry inserted at specified locations along the blade length. The defect blade was tested at the National Wind Technology Center at the National Renewable Energy Laboratory using a schedule of cycles at increasing load level until failure was detected. Our researchers used digital image correlation, shearography, acoustic emission, fiber-optic strain sensing, thermal imaging, and piezoelectric sensing as structural health monitoring techniques. Furthermore, this article provides a comparison of the sensing results of these different structural health monitoring approaches to detect the defects and track the resultant damage from the initial fatigue cycle to final failure.

  15. Inspection and monitoring of wind turbine blade-embedded wave defects during fatigue testing

    DOE PAGESBeta

    Niezrecki, Christopher; Avitabile, Peter; Chen, Julie; Sherwood, James; Lundstrom, Troy; LeBlanc, Bruce; Hughes, Scott; Desmond, Michael; Beattie, Alan; Rumsey, Mark; et al

    2014-05-20

    The research we present in this article focuses on a 9-m CX-100 wind turbine blade, designed by a team led by Sandia National Laboratories and manufactured by TPI Composites Inc. The key difference between the 9-m blade and baseline CX-100 blades is that this blade contains fabric wave defects of controlled geometry inserted at specified locations along the blade length. The defect blade was tested at the National Wind Technology Center at the National Renewable Energy Laboratory using a schedule of cycles at increasing load level until failure was detected. Our researchers used digital image correlation, shearography, acoustic emission, fiber-opticmore » strain sensing, thermal imaging, and piezoelectric sensing as structural health monitoring techniques. Furthermore, this article provides a comparison of the sensing results of these different structural health monitoring approaches to detect the defects and track the resultant damage from the initial fatigue cycle to final failure.« less

  16. Site Testing Results and Automation

    NASA Astrophysics Data System (ADS)

    Ashley, Michael M.; Storey, John W.; Burton, Michael G.

    NOTE: this is highly preliminary just to get the abstract in by the deadline! - brief summary of the AASTO program - key points from the site testing results at South Pole - very brief introduction to ICECAM and the AASTINO - key results from ICECAM and the AASTINO instruments - next year's instrument plans at South Pole and Dome C including a brief mention of Doug Caldwell's experiment

  17. Fatigue and thermal fatigue of Pb-Sn solder joints

    SciTech Connect

    Frear, D.; Grivas, D.; McCormack, M.; Tribula, D.; Morris, J.W. Jr.

    1987-01-01

    This paper presents a fundamental investigation of the fatigue and thermal fatigue characteristics, with an emphasis on the microstructural development during fatigue, of Sn-Pb solder joints. Fatigue tests were performed in simple shear on both 60Sn-40Pb and 5Sn-95Pb solder joints. Isothermal fatigue tests show increasing fatigue life of 60Sn-40Pb solder joints with decreasing strain and temperature. In contrast, such behavior was not observed in the isothermal fatigue of 5Sn-95Pb solder joints. Thermal fatigue results on 60Sn-40Pb solder cycled between -55/sup 0/C and 125/sup 0/C show that a coarsened region develops in the center of the joint. Both Pb-rich and Sn-rich phases coarsen, and cracks form within these coarsened regions. The failure mode 60Sn-40Pb solder joints in thermal and isothermal fatigue is similar: cracks form intergranularly through the Sn-rich phase or along Sn/Pb interphase boundaries. Extensive cracking is found throughout the 5Sn-95Pb joint for both thermal and isothermal fatigue. In thermal fatigue the 5Sn-95Pb solder joints failed after fewer cycles than 60Sn-40Pb.

  18. The fatigue-crack propagation behavior of ASTM A533-B steel tested in vacuo at LWR operating temperatures

    SciTech Connect

    James, L.A.

    1987-01-01

    The fatigue-crack propagation (FCP) behavior of ASTM A533-B-1 steel was characterized in vacuo at 288/sup 0/C. Tests were conducted at two stress ratios: R = 0.05 and R = 0.7. Results of these tests were compared with results from previous studies for the same type of steel tested in an air environment, and FCP rates in vacuo were generally lower than those in air. Stress ratio effects in vacuo were not as great as those in air, and both stress ratio effects and environmental effects are discussed from the standpoint of crack closure concepts.

  19. Thermal Fatigue Evaluation of Pb-Free Solder Joints: Results, Lessons Learned, and Future Trends

    NASA Astrophysics Data System (ADS)

    Coyle, Richard J.; Sweatman, Keith; Arfaei, Babak

    2015-09-01

    Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements for eutectic SnPb. This paper discusses the results from Pb-free solder joint reliability programs sponsored by two industry consortia. The characteristic life in accelerated thermal cycling is reported for 12 different Pb-free solder alloys and a SnPb control in 9 different accelerated thermal cycling test profiles in terms of the effects of component type, accelerated thermal cycling profile and dwell time. Microstructural analysis on assembled and failed samples was performed to investigate the effect of initial microstructure and its evolution during accelerated thermal cycling test. A significant finding from the study is that the beneficial effect of Ag on accelerated thermal cycling reliability (measured by characteristic lifetime) diminishes as the severity of the accelerated thermal cycling, defined by greater ΔT, higher peak temperature, and longer dwell time increases. The results also indicate that all the Pb-free solders are more reliable in accelerated thermal cycling than the SnPb alloy they have replaced. Suggestions are made for future work, particularly with respect to the continued evolution of alloy development for emerging application requirements and the value of using advanced analytical methods to provide a better understanding of the effect of microstructure and its evolution on accelerated thermal cycling performance.

  20. Axial-Load Fatigue Tests on 17-7 PH Stainless Steel Under Constant-Amplitude Loading

    NASA Technical Reports Server (NTRS)

    Leybold, Herbert A.

    1960-01-01

    Axial-load fatigue tests were conducted at room temperature on notched and unnotched sheet specimens of 17-7 PH stainless steel in Condition TH 1050. The notched specimens had theoretical stress-concentration factors of 2.32, 4.00, and 5.00. All specimens were tested under completely reversed loading. S-N curves are presented for each specimen configuration and ratios of fatigue strengths of unnotched specimens to those of notched specimens are given. Predictions of the fatigue behavior of notched specimens near the fatigue limit were made.

  1. Bell Canyon test and results

    SciTech Connect

    Christensen, C. L.; Hunter, T. O.

    1980-01-01

    The purposes of the Borehold Plugging Program are: to identify issues associated with sealing boreholes and shafts; to establish a data base from which to assess the importance of these issues; and to develop sealing criteria, materials, and demonstrative test for the Waste Isolation Pilot Plant (WIPP). The Bell Canyon Test described in this report is one part of that program. Its purpose was to evaluate, in situ, the state of the art in borehole plugs and to identify and resolve problems encountered in evaluating a typical plug installation in anhydrite. The test results are summarized from the work of Peterson and Christensen and divided into two portions: system integrity and wellbore characterization tests prior to plug installation, and a series of tests to evaluate isolation characteristics of the 1.8-m-long plug. Conclusions of the Bell Canyon Test are: brine and fresh-water grouts, with acceptable physical properties in the fluid and hardened states, have been developed; the field data, taken together with laboratory data, suggest that the predominant flow into the test region occurs through the cement plug/borehold interface region, with lesser contributions occurring through the wellbore damage zone, the plug core, and the surrounding undisturbed anhydrite bed; and the 1.8-m-long by 20-cm-diameter grout plug, installed in anhydrite at a depth of 1370 m in the AEC-7 borehole, limits flow from the high pressure Bell Canyon aquifer to 0.6 liters/day.

  2. COLD TEST LOOP INTEGRATED TEST LOOP RESULTS

    SciTech Connect

    Abraham, TJ

    2003-10-22

    A testing facility (Cold Test Loop) was constructed and operated to demonstrate the efficacy of the Accelerated Waste Retrieval (AWR) Project's planned sluicing approach to the remediation of Silos 1 and 2 at the Fernald Environmental Management Project near Cincinnati, Ohio. The two silos contain almost 10,000 tons of radium-bearing low-level waste, which consists primarily of solids of raffinates from processing performed on ores from the Democratic Republic of Congo (commonly referred to as ''Belgium Congo ores'') for the recovery of uranium. These silos are 80 ft in diameter, 36 ft high to the center of the dome, and 26.75 ft to the top of the vertical side walls. The test facility contained two test systems, each designed for a specific purpose. The first system, the Integrated Test Loop (ITL), a near-full-scale plant including the actual equipment to be installed at the Fernald Site, was designed to demonstrate the sluicing operation and confirm the selection of a slurry pump, the optimal sluicing nozzle operation, and the preliminary design material balance. The second system, the Component Test Loop (CTL), was designed to evaluate many of the key individual components of the waste retrieval system over an extended run. The major results of the initial testing performed during July and August 2002 confirmed that the AWR approach to sluicing was feasible. The ITL testing confirmed the following: (1) The selected slurry pump (Hazleton 3-20 type SHW) performed well and is suitable for AWR application. However, the pump's motor should be upgraded to a 200-hp model and be driven by a 150-hp variable-frequency drive (VFD). A 200-hp VFD is not much more expensive and would allow the pump to operate at full speed. (2) The best nozzle performance was achieved by using 15/16-in. nozzles operated alternately. This configuration appeared to most effectively mine the surrogate. (3) The Solartron densitometer, which was tested as an alternative mass flow measurement

  3. Mobile evaporator corrosion test results

    SciTech Connect

    Rozeveld, A.; Chamberlain, D.B.

    1997-05-01

    Laboratory corrosion tests were conducted on eight candidates to select a durable and cost-effective alloy for use in mobile evaporators to process radioactive waste solutions. Based on an extensive literature survey of corrosion data, three stainless steel alloys (304L, 316L, AL-6XN), four nickel-based alloys (825, 625, 690, G-30), and titanium were selected for testing. The corrosion tests included vapor phase, liquid junction (interface), liquid immersion, and crevice corrosion tests on plain and welded samples of candidate materials. Tests were conducted at 80{degrees}C for 45 days in two different test solutions: a nitric acid solution. to simulate evaporator conditions during the processing of the cesium ion-exchange eluant and a highly alkaline sodium hydroxide solution to simulate the composition of Tank 241-AW-101 during evaporation. All of the alloys exhibited excellent corrosion resistance in the alkaline test solution. Corrosion rates were very low and localized corrosion was not observed. Results from the nitric acid tests showed that only 316L stainless steel did not meet our performance criteria. The 316L welded interface and crevice specimens had rates of 22.2 mpy and 21.8 mpy, respectively, which exceeds the maximum corrosion rate of 20 mpy. The other welded samples had about the same corrosion resistance as the plain samples. None of the welded samples showed preferential weld or heat-affected zone (HAZ) attack. Vapor corrosion was negligible for all alloys. All of the alloys except 316L exhibited either {open_quotes}satisfactory{close_quotes} (2-20 mpy) or {open_quotes}excellent{close_quotes} (<2 mpy) corrosion resistance as defined by National Association of Corrosion Engineers. However, many of the alloys experienced intergranular corrosion in the nitric acid test solution, which could indicate a susceptibility to stress corrosion cracking (SCC) in this environment.

  4. Ferrographic analysis of wear debris generated in accelerated rolling element fatigue tests

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Parker, R. J.

    1977-01-01

    The types and quantities of wear particles generated during accelerated ball rolling contact fatigue tests were determined. Ball specimens were made of AMS 5749, a corrosion resistant, high-temperature bearing steel. The lubricant was a super-refined naphthenic mineral oil. Conditions included a maximum Hertz stress of 5.215 times 10 to the 9th power Pa and a shaft speed of 10,000 rpm. Four types of wear particles were observed; normal rubbing wear particles, fatigue spall particles, spheres, and friction polymer.

  5. Fatigue testing of low-cost fiberglass composite wind turbine blade materials

    NASA Technical Reports Server (NTRS)

    Hofer, K. E.; Bennett, L. C.

    1981-01-01

    The static and fatigue behavior of transverse filament tape (TFT) fiberglass/epoxy and TFT/polyester composites was established by the testing of specimens cut from panels fabricated by a filament winding process used for the construction of large experimental wind turbine blades.

  6. Evaluation of advanced lubricants for aircraft applications using gear surface fatigue tests

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis P.; Shimski, John

    1991-01-01

    Surface pitting fatigue life tests were conducted with five lubricants, using spur gears made from a single lot of consumable-electrode vacuum melted (CVM) AISI 9310 steel. The gears were case carbonized and hardened to a Rockwell c-60 and finish ground. The gear pitch diameter was 8.89 cm. The lot of gears was divided into five groups, each of which was tested with a different lubricant. The test lubricants can be classified as synthetic polyol-esters with various viscosities and additive packages. Test conditions included bulk gear temperature of 350 K, a maximum Hertz stress of 1.71 GPa (248 ksi) at the pitch line, and a speed of 10,000 RPM. The lubricant with a viscosity that provided a specific film thickness greater than one and with an additive package produced far greater gear surface fatigue lives than lubricants with a viscosity that provided specific film thickness less than one. A low viscosity lubricant with an additive package produced gear surface fatigue lives equivalent to a similar base stock lubricant with 30 percent higher viscosity, but without an additive package. Lubricants with the same viscosity and similar additive packages gave equivalent gear surface fatigue lives.

  7. Acceptance of New Technology: A Usability Test of a Computerized Adaptive Test for Fatigue in Rheumatoid Arthritis

    PubMed Central

    Nikolaus, Stephanie; Taal, Erik; Vonkeman, Harald E; Glas, Cees AW; van de Laar, Mart AFJ

    2014-01-01

    Background Little is known about the acceptance and usability of computerized adaptive tests (CATs) among patients with rheumatoid arthritis (RA). The main difference between completing a CAT and a traditional questionnaire concerns item presentation. CATs only provide one item at a time on the screen, and skipping forward or backward to review and change already given answers is often not possible. Objective The objective of this study was to examine how patients with RA experience a Web-based CAT for fatigue. Methods In individual sessions, participants filled in the CAT while thinking aloud, and were subsequently interviewed about their experience with the new instrument. The technology acceptance model (TAM) was used to structure the results. Results The participants were 15 patients with RA. They perceived the CAT as clear, brief, and easy to use. They were positive about answering one question per screen, the changing response options, layout, progress bar, and item number. There were 40% (6/15) of the participants that also mentioned that they experienced the completion of the CAT as useful and pleasant, and liked the adaptive test mechanism. However, some participants noted that not all items were applicable to everybody, and that the wordings of questions within the severity dimension were often similar. Conclusions Participants perceived the “CAT Fatigue RA” as easy to use, and also its usefulness was expressed. A 2.0 version has been improved according to the participants’ comments, and is currently being used in a validation study before it will be implemented in daily clinical practice. Our results give a first indication that CAT methodology may outperform traditional questionnaires not merely on measurement precision, but also on usability and acceptance valuation. PMID:27025404

  8. Effects on fatigue life of gate valves due to higher torque switch settings during operability testing

    SciTech Connect

    Richins, W.D.; Snow, S.D.; Miller, G.K.; Russell, M.J.; Ware, A.G.

    1995-12-01

    Some motor operated valves now have higher torque switch settings due to regulatory requirements to ensure valve operability with appropriate margins at design basis conditions. Verifying operability with these settings imposes higher stem loads during periodic inservice testing. These higher test loads increase stresses in the various valve internal parts which may in turn increase the fatigue usage factors. This increased fatigue is judged to be a concern primarily in the valve disks, seats, yokes, stems, and stem nuts. Although the motor operators may also have significantly increased loading, they are being evaluated by the manufacturers and are beyond the scope of this study. Two gate valves representative of both relatively weak and strong valves commonly used in commercial nuclear applications were selected for fatigue analyses. Detailed dimensional and test data were available for both valves from previous studies at the Idaho National Engineering Laboratory. Finite element models were developed to estimate maximum stresses in the internal parts of the valves and to identity the critical areas within the valves where fatigue may be a concern. Loads were estimated using industry standard equations for calculating torque switch settings prior and subsequent to the testing requirements of USNRC Generic Letter 89--10. Test data were used to determine both; (1) the overshoot load between torque switch trip and final seating of the disk during valve closing and (2) the stem thrust required to open the valves. The ranges of peak stresses thus determined were then used to estimate the increase in the fatigue usage factors due to the higher stem thrust loads. The usages that would be accumulated by 100 base cycles plus one or eight test cycles per year over 40 and 60 years of operation were calculated.

  9. Decreased oxygen extraction during cardiopulmonary exercise test in patients with chronic fatigue syndrome

    PubMed Central

    2014-01-01

    Background The insufficient metabolic adaptation to exercise in Chronic Fatigue Syndrome (CFS) is still being debated and poorly understood. Methods We analysed the cardiopulmonary exercise tests of CFS patients, idiopathic chronic fatigue (CFI) patients and healthy visitors. Continuous non-invasive measurement of the cardiac output by Nexfin® (BMEYE B.V. Amsterdam, the Netherlands) was added to the cardiopulmonary exercise tests. The peak oxygen extraction by muscle cells and the increase of cardiac output relative to the increase of oxygen uptake (ΔQ’/ΔV’O2) were measured, calculated from the cardiac output and the oxygen uptake during incremental exercise. Results The peak oxygen extraction by muscle cells was 10.83 ± 2.80 ml/100ml in 178 CFS women, 11.62 ± 2.90 ml/100 ml in 172 CFI, and 13.45 ± 2.72 ml/100 ml in 11 healthy women (ANOVA: P=0.001), 13.66 ± 3.31 ml/100 ml in 25 CFS men, 14.63 ± 4.38 ml/100 ml in 51 CFI, and 19.52 ± 6.53 ml/100 ml in 7 healthy men (ANOVA: P=0.008). The ΔQ’/ΔV’O2 was > 6 L/L (normal ΔQ’/ΔV’O2 ≈ 5 L/L) in 70% of the patients and in 22% of the healthy group. Conclusion Low oxygen uptake by muscle cells causes exercise intolerance in a majority of CFS patients, indicating insufficient metabolic adaptation to incremental exercise. The high increase of the cardiac output relative to the increase of oxygen uptake argues against deconditioning as a cause for physical impairment in these patients. PMID:24456560

  10. Fatigue-test acceleration with flight-by-flight loading and heating to simulate supersonic-transport operation

    NASA Technical Reports Server (NTRS)

    Imig, L. A.; Garrett, L. E.

    1973-01-01

    Possibilities for reducing fatigue-test time for supersonic-transport materials and structures were studied in tests with simulated flight-by-flight loading. In order to determine whether short-time tests were feasible, the results of accelerated tests (2 sec per flight) were compared with the results of real-time tests (96 min per flight). The effects of design mean stress, the stress range for ground-air-ground cycles, simulated thermal stress, the number of stress cycles in each flight, and salt corrosion were studied. The flight-by-flight stress sequences were applied to notched sheet specimens of Ti-8Al-1Mo-1V and Ti-6Al-4V titanium alloys. A linear cumulative-damage analysis accounted for large changes in stress range of the simulated flights but did not account for the differences between real-time and accelerated tests. The fatigue lives from accelerated tests were generally within a factor of two of the lives from real-time tests; thus, within the scope of the investigation, accelerated testing seems feasible.

  11. Acoustic emission monitoring of a fatigue test of an F/A-18 bulkhead

    NASA Astrophysics Data System (ADS)

    Scala, C. M.; McCardle, J. F.; Bowles, S. J.

    This paper describes the application of acoustic emission (AE) to identify cracking in several fatigue-critical regions on the port and starboard sides of an l/A-18 aircraft bulkhead undergoing fatigue testing. AE data acquisition was carried out using an array of three sensors on each side of the bulkhead. AE features stored by each array included relative arrival times of AE events at the three sensors, event rise time at the first-hit sensor, and the load level and the position on the load cycle of event occurrence. AE data processing involved a comparison between the features of those AE events stored during the fatigue testing and predicted features for cracking in the complex-shaped bulkhead. Feature prediction was based on wave propagation characteristics obtained by Pentel-lead calibration, and the known load cycle dependence of crack-related AE events. The AE processing was completed following failure of the bulkhead, and gave the correct locations of all cracks, greater than about 1 mm in depth, present in the bulkhead during the fatigue testing. The study shows that AE associated with cracking can be distinguished, even when many extraneous sources are present, and demonstrates that AE is a promising technique for nondestructive evaluation of a complex structure such as the F/A-18 bulkhead.

  12. AXAF hypervelocity impact test results

    NASA Technical Reports Server (NTRS)

    Frost, Cynthia L.; Rodriguez, Pedro I.

    1997-01-01

    Composite and honeycomb panels are commonly used for spacecraft structural components. The impact test results and analysis of six different composite and honeycomb combinations for use on the advanced X-ray astrophysics facility (AXAF) are reported. The AXAF consists of an X-ray telescope and the associated detecting devices attached to an octagonal spacecraft with an internal propulsion system. The spacecraft's structural panels and optical bench are made of two different graphite fiber reinforced polyimides or composite panels bonded to either side of an aluminum honeycomb. The instrument is required to have at least a 0.92 probability of no failure of any of the critical elements due to meteoroids and debris. In relation to the no-failure probability determination in its low earth orbit environment, hypervelocity impact testing was performed to determine the ballistic limit range and the extent of damage due to impact. The test results for a power and signal cable bundle located behind a panel are presented. Tests planned for a multilayer insulation (MLI) blanket and four types of cable bundles are discussed.

  13. Experimental and Finite Element Modeling of Near-Threshold Fatigue Crack Growth for the K-Decreasing Test Method

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Seshadri, Banavara R.; Newman, John A.

    2015-01-01

    The experimental methods to determine near-threshold fatigue crack growth rate data are prescribed in ASTM standard E647. To produce near-threshold data at a constant stress ratio (R), the applied stress-intensity factor (K) is decreased as the crack grows based on a specified K-gradient. Consequently, as the fatigue crack growth rate threshold is approached and the crack tip opening displacement decreases, remote crack wake contact may occur due to the plastically deformed crack wake surfaces and shield the growing crack tip resulting in a reduced crack tip driving force and non-representative crack growth rate data. If such data are used to life a component, the evaluation could yield highly non-conservative predictions. Although this anomalous behavior has been shown to be affected by K-gradient, starting K level, residual stresses, environmental assisted cracking, specimen geometry, and material type, the specifications within the standard to avoid this effect are limited to a maximum fatigue crack growth rate and a suggestion for the K-gradient value. This paper provides parallel experimental and computational simulations for the K-decreasing method for two materials (an aluminum alloy, AA 2024-T3 and a titanium alloy, Ti 6-2-2-2-2) to aid in establishing clear understanding of appropriate testing requirements. These simulations investigate the effect of K-gradient, the maximum value of stress-intensity factor applied, and material type. A material independent term is developed to guide in the selection of appropriate test conditions for most engineering alloys. With the use of such a term, near-threshold fatigue crack growth rate tests can be performed at accelerated rates, near-threshold data can be acquired in days instead of weeks without having to establish testing criteria through trial and error, and these data can be acquired for most engineering materials, even those that are produced in relatively small product forms.

  14. Loading frequencies up to 20Hz as an alternative to accelerate fatigue strength tests in a Y-TZP ceramic.

    PubMed

    Fraga, Sara; Pereira, Gabriel Kalil Rocha; Freitas, Mariana; Kleverlaan, Cornelis Johannes; Valandro, Luiz Felipe; May, Liliana Gressler

    2016-08-01

    Considering the interest of the research community in the fatigue behavior of all-ceramic restorations and the time consumed in low-frequency cyclic fatigue tests, this study aimed to investigate the influence of the loading frequency on the zirconia fatigue strength. The biaxial flexural fatigue strength of Y-TZP discs was determined by the staircase approach after 500,000 cycles. The investigated frequencies were 2Hz (control-simulation of the chewing activity; n=20), 10Hz (n=20), 20Hz (n=20), and 40Hz (n=21). The fatigue strength data were analyzed using one-way ANOVA and post-hoc Tukey׳s test (α=0.05). Pearson coefficient (r) was calculated to assess the existence of a correlation between fatigue strength and loading frequency. X-ray diffraction analysis was used to determine the relative amount of monoclinic phase under each fatigue test condition. The fatigue strength was significantly higher for 40Hz group (630.7±62.1MPa) and did not differ among the groups 2Hz (550.3±89.7MPa), 10Hz (574.0±47MPa) and 20Hz (605.1±30.7MPa). Pearson correlation coefficient indicated a significantly moderate correlation (r=0.57) between fatigue strength and loading frequency. The percentage of monoclinic phase was similar among the groups. Therefore, the use of loading frequencies up to 20Hz seems a good alternative to expedite the cycling strength fatigue tests in polycrystalline ceramics without significantly changing the fatigue behavior showed by zirconia in tests employing the frequency of the masticatory cycle. PMID:26849030

  15. Fatigue Testing of Metallurgically-Bonded EBR-II Superheater Tubes

    SciTech Connect

    Terry C. Totemeier

    2006-12-01

    Fatigue crack growth tests were performed on 2¼Cr-1Mo steel specimens machined from ex-service Experimental Breeder Reactor – II (EBR-II) superheater duplex tubes. The tubes had been metallurgically bonded with a 100 µm thick Ni interlayer; the specimens incorporated this bond layer. Tests were performed at room temperature in air and at 400°C in air and humid Ar; cracks were grown at varied levels of constant ?K. Crack growth tests at a range of ?K were also performed on specimens machined from the shell of the superheater. In all conditions the presence of the Ni interlayer was found to result in a net retardation of growth as the crack passed through the interlayer. The mechanism of retardation was identified as a disruption of crack planarity and uniformity after passing through the porous interlayer. Full crack arrest was only observed in a single test performed at near-threshold ?K level (12 MPa?m) at 400°C. In this case the crack tip was blunted by oxidation of the base steel at the steel-interlayer interface.

  16. Fatigue of fiberglass beam substructures

    SciTech Connect

    Mandell, J.F.; Combs, D.W.; Samborsky, D.D.

    1995-09-01

    Composite material beams representative of wind turbine blade substructure have been designed, fabricated, and tested under constant amplitude flexural fatigue loading. Beam stiffness, strength, and fatigue life are predicted based on detailed finite element analysis and the materials fatigue database developed using standard test coupons and special high frequency minicoupons.Beam results are in good agreement with predictions when premature adhesive and delamination failures are avoided in the load transfer areas. The results show that fiberglass substructures can be designed and fabricated to withstand maximum strain levels on the order of 8,000 microstrain for about 10{sup 6} cycles with proper structural detail design and the use of fatigue resistant laminate constructions. The study also demonstrates that the materials fatigue database and accurate analysis can be used to predict the fatigue life of composite substructures typical of blades.

  17. Fatigue strength of high-temperature alloys under conditions of cyclic temperature variation. Communication 1: Experimental procedure and results

    NASA Astrophysics Data System (ADS)

    Troshchenko, V. T.; Gryaznov, B. A.; Yamshanov, Yu. B.

    1994-03-01

    Determination of the serviceability of the material of gas-turbine engine blades, one of the most loaded elements of the engine, critical for the reliability of the turbine, is discussed. The NUM-3 setup, intended for studying fatigue strength of high-temperature alloys under conditions simulating service ones, is briefly described. The results of the investigation into the fatigue of alloys EP962 and EI698 under isothermal conditions and complex thermal-mechanical loading are presented. The analysis of the findings revealed a number of regularities in the effect of thermal cycling and resulting varying thermal stresses on the fatigue strength of the materials studied.

  18. Space Shuttle Partial Stack Rollout Test Analytical Correlation In Support Of Fatigue Load Development

    NASA Technical Reports Server (NTRS)

    DelBasso, Steve; Dolenz, Jim; Wilson, Lee

    2005-01-01

    A rollout test with only the Solid Rocket Boosters was conducted in November 2003 to gather structural dynamic response data of the transportation environment from the Vehicle Assembly Building to the Launch Pad. The data was acquired to develop and validate analytical methods used to predict rollout Orbiter fatigue load spectra. Earlier predictions computed by a base drive approach with only 5 input drive degrees-of-freedom raised questions that commissioned the partial stack test. Not only was there a concern because of the input degree-of-freedom omission due to measurement limitations, but there was also a concern with the implementation of the "large mass" itself. Three methods were evaluated with the partial stack test data. The analytical correlations to measured strain derived SRB base loads and acceleration5 showed the earlier 5 degree-of-freedom base drive approach to yield the most conservative results for all quantities monitored except the SRB base moment about the axis in which the input drive was missing. This non-conservative shortcoming led to a recommendation to use either the 6 degree-of-freedom base drive or the 12 degree-of-freedom Craig-Bampton boundary drive methods whose results did not substantially differ.

  19. Cryogenic Brush Seal Test Results

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Walker, James F.

    1996-01-01

    Brush seals are compliant, contact seals that have long-life, low-leakage characteristics desirable for use in rocket engine turbopumps. 50.8-mm (2.0 inch) diameter brush seals with a nominal initial radial interference of 0.127-mm (0.005 inch) were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and differential pressure loads up to 1.21 MPa (175 psi) per brush. The measured leakage rate of a single brush was 2-3 times less than that measured for a 12-tooth, 0.127-mm (0.005 inch) radial clearance labyrinth seal used as a baseline. Stage effects were studied and it was found that two brush seals with a large separation distance leaked less than two brushes tightly packed together. The maximum measured groove depth on the Inconel 718 rotor was 25.4 (mu)m (0.001 inch) after 4.31 hours of shaft rotation. The Haynes-25 bristles wore approximately 25.4-76.2 (mu)m (0.001-0.003 inch) under the same conditions. Three seal runner coatings, chromium carbide, Teflon impregnated chromium, and zirconium oxide, were tested in liquid hydrogen at 35,000 and 65,000 rpm with separate 50.8 mm diameter brush seals made of Haynes-25 bristles and having a nominal initial radial interference of 129 rpm. Two bare Inconel-718 rotors were also tested as a baseline. The test results revealed significant differences between the wear characteristics of the uncoated and coated seal runners. At both speeds the brush seal with the bare Inconel-718 seal runner exhibited significant bristle wear with excessive material transferring to the runner surface. In contrast, the coated seal runners inhibited the transfer and deposit of bristle material. The chromium carbide coating showed only small quantities of bristle material transferring to its surface. The Teflon impregnated chromium coating also inhibited material transfer and provided some lubrication. This coating, however, is self-sacrificing. The Teflon remained present on the low speed runner, but it was completely removed from the

  20. RSG Deployment Case Testing Results

    SciTech Connect

    Owsley, Stanley L.; Dodson, Michael G.; Hatchell, Brian K.; Seim, Thomas A.; Alexander, David L.; Hawthorne, Woodrow T.

    2005-09-01

    The RSG deployment case design is centered on taking the RSG system and producing a transport case that houses the RSG in a safe and controlled manner for transport. The transport case was driven by two conflicting constraints, first that the case be as light as possible, and second that it meet a stringent list of Military Specified requirements. The design team worked to extract every bit of weight from the design while striving to meet the rigorous Mil-Spec constraints. In the end compromises were made primarily on the specification side to control the overall weight of the transport case. This report outlines the case testing results.

  1. Diagnostic Tests and Examination Results.

    ERIC Educational Resources Information Center

    Barker, Dennis

    1988-01-01

    A study of the usefulness of several diagnostic tests for selecting students to enter a civil engineering program found that the tests were not appropriate and that tests should be developed specifically for civil engineering. (MSE)

  2. Analysis of wear debris from full-scale bearing fatigue tests using the Ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Loewenthal, S. H.

    1980-01-01

    The Ferrograph was used to determine the types of quantities of wear particles generated during full-scale bearing fatigue tests. Deep-groove ball bearings made from AISI 52100 steel were used. A MIL-L-23699 tetraester lubricant was used in a recirculating lubrication system containing a 49-micron absolute filter. Test conditions included a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the Ferrograph was more sensitive (up to 23 h) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis (SOAP). Four particle types were observed: normal rubbing wear particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  3. Analysis of wear-debris from full-scale bearing fatigue tests using the ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Loewenthal, S. H.

    1980-01-01

    The ferrograph was used to determine the types and quantities of wear particles generated during full-scale bearing fatigue tests. Deep-groove ball bearings made from AISI 52100 steel were used. A MIL-L-23699 tetraester lubricant was used in a recirculating lubrication system containing a 49 mm absolute filter. Test conditions included a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm, and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the ferrograph was more sensitive (up to 23 hr) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis. Four particle types were observed: normal rubbing wear particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  4. Fatigue testing welded joints for P/M Al-matrix composites

    NASA Astrophysics Data System (ADS)

    Harrigan, William C.

    1994-07-01

    To meet their need for high stiffness, many bicycles currently rely on aluminum-matrix composites. The highest strength and highest stiffness form of these material, 6092/B4C/15p, is produced by powder metallurgy techniques. The bicycles are tungsten inert-gas welded and fully heat treated after welding. A test technique has been developed to assess the static and fatigue properties of welded joints. This test technique has revealed the increased stiffness and strength of a 6092/B4C/15p-T6P composite tube joint as compared with a 6061-T6 aluminum one. This test technique is currently being used to identify fatigue properties for both tube joints.

  5. Ferrographic analysis of wear debris from full-scale bearing fatigue tests

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Loewenthal, S. H.

    1979-01-01

    The Ferrograph was used to determine the types and quantities of wear particles generated during full scale bearing fatigue tests. Deep-groove ball bearings made from steel were used. A tetraester lubricant was used in a recirculating lubricant system containing a 49 micrometers absolute filter. Test conditions include a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm, and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the Ferrograph was more sensitive (up to 23 hr) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis. Four particle types were observed: normal rubbing weather particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  6. Cracking and Spalling Behavior of HVOF Thermally Sprayed WC-Co-Cr Coating in Bend and Axial Fatigue Tests

    NASA Astrophysics Data System (ADS)

    Gui, M.; Eybel, R.; Asselin, B.; Monerie-Moulin, F.

    2015-03-01

    In this work, WC-10Co-4Cr coating was sprayed by high-velocity oxygen fuel (HVOF) process on Almen strip and axial fatigue coupon. Three-point bend test was used to bend Almen strip coating specimens with tensile and compressive stress applied to the coating. Axial fatigue coating specimens were tested at a load stress of 1250 MPa and a stress ratio of R = -1. Process condition of Thermal spraying was found to have an effect on spalling performance of the coating in the fatigue test. The mechanism of cracking and spalling process in the coating was studied in bend and fatigue conditions. Based on deformation difference between the coating and the substrate, the factors, especially coating thickness, to impact the coating spalling behavior in axial fatigue test are discussed. HVOF-sprayed WC-10Co-4Cr coating matches the deformation of base substrate by cracking when tensile stress is applied in bend and fatigue tests because the coating has very limit deformation capability. In axial fatigue test of WC-10Co-4Cr coating specimen, the substrate works in a stress-to-strain manner; however the coating works in a strain-to-stress manner and is stressed due to the substrate deformation.

  7. Effects of Holding Time on Thermomechanical Fatigue Properties of Compacted Graphite Iron Through Tests with Notched Specimens

    NASA Astrophysics Data System (ADS)

    Ghodrat, Sepideh; Riemslag, Ton A. C.; Kestens, Leo A. I.; Petrov, Roumen H.; Janssen, Michael; Sietsma, Jilt

    2013-05-01

    In cylinder heads of compacted graphite iron (CGI), the heating and cooling cycles can lead to localized cracking due to thermomechanical fatigue (TMF). Traditionally, TMF behavior is studied by thermal cycling of smooth specimens. The resulting number of cycles to failure ( N f) constitutes a single parameter that can be used to predict actual service failures. Nevertheless, there are also some drawbacks of the conventional testing procedures, most noticeably the prolonged testing times and a considerable scatter in test results. To address these drawbacks, TMF tests were performed using notched specimens, resulting in shorter testing times with less scatter. In the case of cast iron, artificial notches do not necessarily change the TMF behavior since the inherent graphite particles behave as internal notches. Using a notch depth of 0.2 mm, the effect of prolonged holding times (HT) on TMF lifetime was studied and a clear effect was found. Extended holding times were also found to be accompanied by relaxation of compressive stresses, causing higher tensile stresses to develop in the subsequent low temperature stages of the TMF cycles. The lifetimes in notched CGI specimens can be predicted by the Paris' fatigue crack growth model. This model was used to differentiate between the individual effects of stress level and holding times on TMF lifetime. Microstructural changes were evaluated by analyzing quantitative data sets obtained by orientation contrast microscopy based on electron backscattered diffraction (EBSD).

  8. Strainrange partitioning life predictions of the long time metal properties council creep-fatigue tests

    NASA Technical Reports Server (NTRS)

    Saltsman, J. F.; Halford, G. R.

    1979-01-01

    The method of strainrange partitioning is used to predict the cyclic lives of the Metal Properties Council's long time creep-fatigue interspersion tests of several steel alloys. Comparisons are made with predictions based upon the time- and cycle-fraction approach. The method of strainrange partitioning is shown to give consistently more accurate predictions of cyclic life than is given by the time- and cycle-fraction approach.

  9. Nondestructive determination of fatigue crack damage in composites using vibration tests.

    NASA Technical Reports Server (NTRS)

    Dibenedetto, A. T.; Gauchel, J. V.; Thomas, R. L.; Barlow, J. W.

    1972-01-01

    The vibration response of glass reinforced epoxy and polyester laminates was investigated. The complex modulus and the damping capacity were measured as fatigue crack damage accumulated. Changes in the Young's modulus as well as the damping capacity correlated with the amount of crack damage. The damping was especially sensitive to debonding of the reinforcement from the resin matrix. Measurement of these vibration response changes shows promise as a means to nondestructively test the structural integrity of filament-reinforced composite structural members.

  10. Dynamic fatigue testing of Zerodur glass-ceramic

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.

    1988-01-01

    The inherent brittleness of glass invariably leads to a large variability in strength data and a time dependence in strength. Leading rate plays a large role in strength values. Glass is found to be weaker when supporting loads over long periods of time as compared to glass which undergoes rapid leading. These properties complicate the structural design allowables for the utilization of glass components in an application such as Advanced X-ray Astrophysics Facility (AXAF). The test methodology to obtain parameters which can be used to predict the reliability and life time of Zerodur glass-ceramic which is to be used for the mirrors in the AXAF is described.

  11. Progress Letter Report on Bending Fatigue Test System Development for Spent Nuclear Fuel Vibration Integrity Study (Out-of-cell fatigue testing development - Task 2.4)

    SciTech Connect

    Wang, Jy-An John; Wang, Hong; Cox, Thomas S; Baldwin, Charles A; Bevard, Bruce Balkcom

    2013-08-01

    Vibration integrity of high burn-up spent nuclear fuel in transportation remains to be a critical component of US nuclear waste management system. The structural evaluation of package for spent fuel transportation eventually will need to see if the content or spent fuel is in a subcritical condition. However, a system for testing and characterizing such spent fuel is still lacking mainly due to the complication involved with dealing radioactive specimens in a hot cell environment. Apparently, the current state-of-the-art in spent fuel research and development is quite far away from the delivery of reliable mechanical property data for the assessment of spent fuels in the transport package evaluation. Under the sponsorship of US NRC, ORNL has taken the challenge in developing a robust testing system for spent fuel in hot cell. An extensive literature survey was carried out and unique requirements of such testing system were identified. The U-frame setup has come to the top among various designs examined for reverse bending fatigue test of spent fuel rod. The U-frame has many features that deserve mentioned here: Easy to install spent fuel rod in test; Less linkages than in conventional bending test setup such as three-point or four-point bending; Target the failure mode relevant to the fracture of spent fuel rod in transportation by focusing on pure bending; The continuous calibrations and modifications resulted in the third generation (3G) U-frame testing setup. Rigid arms are split along the LBB axis at rod sample ends. For each arm, this results in a large arm body and an end piece. Mating halves of bushings were modified into two V-shaped surfaces on which linear roller bearings (LRB) are embedded. The rod specimen is installed into the test fixture through opening and closing slide end-pieces. The 3G apparently has addressed major issues of setup identified in the previous stage and been proven to be eligible to be further pursued in this project. On the other

  12. Applications of infrared thermography for nondestructive testing of fatigue cracks in steel bridges

    NASA Astrophysics Data System (ADS)

    Sakagami, Takahide; Izumi, Yui; Kobayashi, Yoshihiro; Mizokami, Yoshiaki; Kawabata, Sunao

    2014-05-01

    In recent years, fatigue crack propagations in aged steel bridge which may lead to catastrophic structural failures have become a serious problem. For large-scale steel structures such as orthotropic steel decks in highway bridges, nondestructive inspection of deteriorations and fatigue damages are indispensable for securing their safety and for estimating their remaining strength. As conventional NDT techniques for steel bridges, visual testing, magnetic particle testing and ultrasonic testing have been commonly employed. However, these techniques are time- and labor- consuming techniques, because special equipment is required for inspection, such as scaffolding or a truck mount aerial work platform. In this paper, a new thermography NDT technique, which is based on temperature gap appeared on the surface of structural members due to thermal insulation effect of the crack, is developed for detection of fatigue cracks. The practicability of the developed technique is demonstrated by the field experiments for highway steel bridges in service. Detectable crack size and factors such as measurement time, season or spatial resolution which influence crack detectability are investigated.

  13. CHARACTERIZATION OF A MOBILE OSCILLATORY FATIGUE OPERATOR FOR WIND TURBINE BLADE TESTING

    SciTech Connect

    Donohoo, P.E.; Cotrell, J.

    2008-01-01

    Laboratory testing of wind turbine blades is required to meet wind turbine design standards, reduce machine cost, and reduce the technical and fi nancial risks of deploying mass-produced wind turbine models. Fatigue testing at the National Wind Technology Center (NWTC) is currently conducted using Universal Resonance Excitation (UREX) technology. In a UREX test, the blade is mounted to a rigid stand and hydraulic exciters mounted to the blade are used to excite the blade to its resonant frequency. A drawback to UREX technology is that mounting hydraulic systems to the blade is diffi cult and requires a relatively long set-up period. An alternative testing technology called the Mobile Oscillatory Fatigue Operator (MOFO) has been analyzed. The MOFO uses an oscillating blade test-stand rather than a rigid stand, avoiding the need to place hydraulic systems on the blade. The MOFO will be demonstrated by converting an existing test-stand at the NWTC to an oscillating stand that can test blades up to 25 m in length. To obtain the loads necessary to design the MOFO, the system motion is modeled using rigid body and lumped mass dynamics models. Preliminary modeling indicates the existing stand can be converted to a MOFO relatively easily. However, the blade dynamic models suggest that blade bending moment distributions are signifi cantly different for UREX and MOFO testing; more sophisticated models are required to assess the implication of this difference on the accuracy of the test.

  14. Improvements in Depression and Changes in Fatigue: Results from the SLAM DUNC Depression Treatment Trial

    PubMed Central

    Bengtson, Angela M.; Gaynes, Bradley N.; McGuinness, Teena; Quinlivan, Evelyn B.; Ogle, Michelle; Heine, Amy; Thielman, Nathan M.; Pence, Brian W.

    2016-01-01

    Fatigue and depression are common co-morbid conditions among people with HIV infection. We analyzed a population of HIV-infected adults with depression, who were enrolled in a depression treatment trial, to examine the extent to which improvements in depression over time were associated with improvements in HIV-related fatigue. Data for this analysis come from a randomized controlled trial to evaluate the effectiveness of improved depression treatment on antiretroviral adherence. Fatigue was measured using the HIV-Related Fatigue Scale, and depressive symptoms were measured with the Hamilton Depression Rating Scale. Participants (n = 234) were on average nearly 44 years of age and predominantly male, black or African American, and unemployed. Individuals who experienced stronger depression response (i.e., greater improvement in depression score) had larger decreases in fatigue. However, even among those who demonstrated a full depression response, nearly three-quarters continued to have either moderate or severe fatigue at 6 and 12 months. PMID:26525221

  15. Crack propagation monitoring in a full-scale aircraft fatigue test based on guided wave-Gaussian mixture model

    NASA Astrophysics Data System (ADS)

    Qiu, Lei; Yuan, Shenfang; Bao, Qiao; Mei, Hanfei; Ren, Yuanqiang

    2016-05-01

    For aerospace application of structural health monitoring (SHM) technology, the problem of reliable damage monitoring under time-varying conditions must be addressed and the SHM technology has to be fully validated on real aircraft structures under realistic load conditions on ground before it can reach the status of flight test. In this paper, the guided wave (GW) based SHM method is applied to a full-scale aircraft fatigue test which is one of the most similar test status to the flight test. To deal with the time-varying problem, a GW-Gaussian mixture model (GW-GMM) is proposed. The probability characteristic of GW features, which is introduced by time-varying conditions is modeled by GW-GMM. The weak cumulative variation trend of the crack propagation, which is mixed in time-varying influence can be tracked by the GW-GMM migration during on-line damage monitoring process. A best match based Kullback–Leibler divergence is proposed to measure the GW-GMM migration degree to reveal the crack propagation. The method is validated in the full-scale aircraft fatigue test. The validation results indicate that the reliable crack propagation monitoring of the left landing gear spar and the right wing panel under realistic load conditions are achieved.

  16. Solder fatigue reduction in point focus photovoltaic concentrator modules

    SciTech Connect

    Hund, T.D.; Burchett, S.N.

    1991-01-01

    Solder fatigue tests have been conducted on point focus photovoltaic concentration cell assemblies to identify a baseline fatigue life and to quantify the fatigue life improvements that result using a copper-molybdenum-copper low-expansion insert between the solar cell and copper heat spreader. Solder microstructural changes and fatigue crack growth were identified using cross sections and ultrasonic scans of the fatigue solder joints. The Coffin-Manson and Total Strain fatigue models for low-cycle fatigue were evaluated for use in fatigue life predictions. Since both of these models require strain calculations, two strain calculation methods were compared: hand-calculated shear strain and a finite element method shear strain. At present, the available theoretical models for low-cycle solder fatigue are limited in their ability to predict failure; consequently, extensive thermal cycling is continuing to define the fatigue life for point focus photovoltaic cell assemblies. 9 refs., 9 figs., 2 tabs.

  17. Results of Deposition Scoping Tests

    SciTech Connect

    Hu, M.Z.

    2003-03-04

    The processes of crystallization and solid deposit formation that led to the shutdown of the 2H evaporator operation at the Savannah River Site (SRS) and that could possibly cause similar problems in the future or in other evaporators need to be better understood. Through experimentation, thermodynamic modeling, and correlation of scaling to historical tank farm operations, progress has been made in developing guidelines as to the concentrations of silicon and aluminum that can be processed by evaporators while avoiding unacceptable levels of scale formation. However, because of limitations of the thermodynamic model and an insufficient amount of operational data at slightly supersaturated concentration levels, uncertainty still exists regarding acceptable feed concentrations. The objective of this effort is to provide information that can be used in defining acceptable levels of silicon and aluminum in evaporator feed solutions. Data collected previously showed that particle formation reactions can be rapid at evaporator temperatures for elevated silicon and aluminum concentrations. However, insufficient data exists to estimate the silicon and aluminum concentrations above which solids will form in the time frame of evaporator processing. The work described in this report was designed to determine the induction period for solutions of decreasing aluminum and silicon concentration such that the supersaturation level corresponding to a 4-h induction time for particle nucleation/growth in bulk solution can be estimated. In addition, experiments were conducted to explore the supersaturation levels that can result in deposition of solids on metal surfaces at varying aluminum-to-silicon concentration ratios. Laboratory studies of particle growth in solution were conducted at relatively low supersaturation levels. Dynamic-light-scattering (DLS) studies and deposition tests, similar to those performed in FY 2001, were conducted with solutions at relatively low

  18. Elastic analysis of a mode II fatigue crack test specimen

    NASA Technical Reports Server (NTRS)

    Gross, B.; Buzzard, R. J.; Brown, W. F., Jr.

    1986-01-01

    Elastic displacements and stress intensity measurements for a mode II specimen have been obtained over a range of a/W values between 0.500 and 0.900 using the MARC general purpose finite element program. Stress intensity factors were experimentally determined using load point displacement values. Good general agreement between numerical and experimental results for crack mouth, crack surface, and load point displacements, and for stress intensity factors, demonstrates the accuracy of the present method.

  19. Fatigue-crack monitoring in-flight using acoustic emission - hardware, technique, and testing

    SciTech Connect

    Hutton, P.H.; Skorpik, J.R.; Lemon, D.K.

    1981-07-01

    The three programs described represent a logical evolutionary process toward effective flaw surveillance in aircraft using AE. The Macchi tests showed that an AE system can withstand extended in-flight service and collect meaningful information relative to fatigue crack growth at a single specific location. The MIrage aircraft work seeks to extend the methods demonstrated on the Macchi into a more complex circumstance. We are now attempting to detect and locate crack growth at any of twenty fastener locations in a relatively complex geometry. The DARPA pattern recognition program seeks to develop signal identification capability that would pave the way for general monitoring of aircraft structures using AE to detect fatigue crack growth. It appears that AE technology may be capable of enhancing aircraft safety assurance while reducing inspection requirements with the associated costs.

  20. Slow fatigue testing of titanium grade 29 in air and seawater

    SciTech Connect

    Atteraas, L.; Hersvik, G.; Solbakken, H.

    1999-07-01

    ASTM Grade 29 titanium has been fatigue tested in air and seawater at 110 C at a low frequency. The possible influence of seawater is completely masked by the fact that all the specimens of welded titanium, and most of the parent metal samples, had internal fracture initiations. Compared to the parent metal, the welded pipe specimens (5G orbital TIG) had a significantly lower fatigue life at the relatively high cyclic stress levels employed ({sigma}{sub max} = 0.85 {sigma}{sub y}). This is attributed to the presence of pores. Fractographic studies of failed weld metal specimens indicate that the fracture initiation takes place in the material immediately surrounding a pore, with an abrupt crack formation, marking the beginning of the crack growth phase. The duration of the crack initiation phase shows large variations, whereas the growth phase duration varies little.

  1. Characterization of a 14Cr ODS steel by means of small punch and uniaxial testing with regard to creep and fatigue at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Bruchhausen, M.; Turba, K.; de Haan, F.; Hähner, P.; Austin, T.; de Carlan, Y.

    2014-01-01

    A 14Cr ODS steel was characterized at elevated temperatures with regard to its behavior in small punch and uniaxial creep tests and in low cycle fatigue tests. A comparison of small punch and uniaxial creep tests at 650 °C revealed a strong anisotropy of the material when strained parallel and perpendicular to the extrusion direction with rupture times being several orders of magnitude lower for the perpendicular direction. The stress-rupture and Larson-Miller plots show a very large scatter of the creep data. This scatter is strongly reduced when rupture time is plotted against minimum deflection rate or minimum creep rate (Monkman-Grant plot). Fatigue tests have been carried out at 650 °C and 750 °C. The alloy is cyclically very stable with practically no hardening/softening. Results from the tests at both temperatures can be described by a common power law. An increase in the test temperature has little influence on the fatigue ductility exponent. For a given total strain level, the fatigue life of the alloy is reduced with increasing temperature.

  2. The high frequency light load fatigue testing machine based on giant magnetostrictive material and stroke multiplier

    NASA Astrophysics Data System (ADS)

    Wang, M. D.; Li, D. S.; Huang, Y.; Zhang, C.; Zhong, K. M.; Sun, L. N.

    2013-08-01

    In the notebook and clamshell mobile phone, data communication wire often requires repeated bending. Generally, communication wire with the actual application conditions, the test data cannot assess bending resistance performance of data communication wire is tested conventionally using wires with weights of 90 degree to test bending number, this test method and device is not fully reflect the fatigue performance in high frequency and light load application condition, at the same time it has a large difference between the test data of the long-term reliability of high frequency and low load conditions. In this paper, high frequency light load fatigue testing machine based on the giant magnetostrictive material and stroke multiplier is put forward, in which internal reflux stroke multiplier is driven by giant magnetostrictive material to realize the rapid movement of light load. This fatigue testing device has the following advantages: (1) When the load is far less than the friction, reducing friction is very effective to improve the device performance. Because the body is symmetrical, the friction loss of radial does not exist in theory, so the stress situation of mechanism is good with high transmission efficiency and long service life. (2) The installation position of the output hydraulic cylinder, can be arranged conveniently as ordinary cylinder. (3) Reciprocating frequency, displacement and speed of high frequency movement can be programmed easily to change with higher position precision. (4)Hydraulic oil in this device is closed to transmit, which does not produce any environment pollution. The device has no hydraulic pump and tank, and less energy conversion processes, so it is with the trend of green manufacturing.

  3. Deformation monitoring with off-the-shelf digital cameras for civil engineering fatigue testing

    NASA Astrophysics Data System (ADS)

    Detchev, I.; Habib, A.; He, F.; El-Badry, M.

    2014-06-01

    Deformation monitoring of civil infrastructure systems is important in terms of both their safety and serviceability. The former refers to estimating the maximum loading capacity during the design stages of a building project, and the latter means performing regularly scheduled maintenance of an already existing structure. Traditionally, large structures have been monitored using surveying techniques, while fine-scale monitoring of structural components such as beams and trusses has been done with strain gauge instrumentation. In the past decade, digital photogrammetric systems coupled with image processing techniques have also been used for deformation monitoring. The major advantage of this remote sensing method for performing deformation monitoring is that there is no need to access the object of interest while testing is in progress. The paper is a result of an experiment where concrete beams with polymer support sheets are subjected to dynamic loading conditions by a hydraulic actuator in a structures laboratory. This type of loading is also known as fatigue testing, and is used to simulate the typical use of concrete beams over a long period of time. From a photogrammetric point of view, the challenge for this type of experiment is to avoid motion artifacts by maximizing the sensor frame rate, and at the same time to have a good enough image quality in order to achieve satisfactory reconstruction precision. This research effort will investigate the optimal camera settings (e.g., aperture, shutter speed, sensor sensitivity, and file size resolution) in order to have a balance between high sensor frame rate and good image quality. The results will be first evaluated in terms of their repeatability, and then also in terms of their accuracy. The accuracy of the results will be checked against another set of results coming from high quality laser transducers.

  4. Chemical compatibility screening test results

    SciTech Connect

    Nigrey, P.J.; Dickens, T.G.

    1997-12-01

    A program for evaluating packaging components that may be used in transporting mixed-waste forms has been developed and the first phase has been completed. This effort involved the screening of ten plastic materials in four simulant mixed-waste types. These plastics were butadiene-acrylonitrile copolymer rubber, cross-linked polyethylene (XLPE), epichlorohydrin rubber, ethylene-propylene rubber (EPDM), fluorocarbon (Viton or Kel-F), polytetrafluoroethylene, high-density polyethylene (HDPE), isobutylene-isoprene copolymer rubber (butyl), polypropylene, and styrene-butadiene rubber (SBR). The selected simulant mixed wastes were (1) an aqueous alkaline mixture of sodium nitrate and sodium nitrite; (2) a chlorinated hydrocarbon mixture; (3) a simulant liquid scintillation fluid; and (4) a mixture of ketones. The testing protocol involved exposing the respective materials to 286,000 rads of gamma radiation followed by 14-day exposures to the waste types at 60{degrees}C. The seal materials were tested using vapor transport rate (VTR) measurements while the liner materials were tested using specific gravity as a metric. For these tests, a screening criterion of 0.9 g/hr/m{sup 2} for VTR and a specific gravity change of 10% was used. Based on this work, it was concluded that while all seal materials passed exposure to the aqueous simulant mixed waste, EPDM and SBR had the lowest VTRs. In the chlorinated hydrocarbon simulant mixed waste, only Viton passed the screening tests. In both the simulant scintillation fluid mixed waste and the ketone mixture simulant mixed waste, none of the seal materials met the screening criteria. For specific gravity testing of liner materials, the data showed that while all materials with the exception of polypropylene passed the screening criteria, Kel-F, HDPE, and XLPE offered the greatest resistance to the combination of radiation and chemicals.

  5. Thermal-mechanical fatigue test apparatus for metal matrix composites and joint attachments

    NASA Technical Reports Server (NTRS)

    Westfall, L. J.; Petrasek, D. W.

    1985-01-01

    Two thermal-mechanical fatigue (TMF) test facilities were designed and developed, one to test tungsten fiber reinforced metal matrix composite specimens at temperature up to 1430C (2600F) and another to test composite/metal attachment bond joints at temperatures up to 760C (1400 F). The TMF facility designed for testing tungsten fiber reinforced metal matrix composites permits test specimen temperature excursions from room temperature to 1430C (2600F) with controlled heating and loading rates. A strain-measuring device measures the strain in the test section of the specimen during each heating and cooling cycle with superimposed loads. Data is collected and recorded by a computer. The second facility is designed to test composite/metal attachment bond joints and to permit heating to a maximum temperature of 760C (1400F) within 10 min and cooling to 150C (300F) within 3 min. A computer controls specimen temperature and load cycling.

  6. Nitinol Fatigue Life for Variable Strain Amplitude Fatigue

    NASA Astrophysics Data System (ADS)

    Lin, Z.; Pike, K.; Schlun, M.; Zipse, A.; Draper, J.

    2012-12-01

    Nitinol fatigue testing results are presented for variable strain amplitude cycling. The results indicate that cycles smaller than the constant amplitude fatigue limit may contribute to significant fatigue damage when they occur in a repeating sequence of large and small amplitude cycles. The testing utilized two specimen types: stent-like diamond specimens and Z-shaped wire specimens. The diamond specimens were made from nitinol tubing with stent-like manufacturing processes and the Z-shaped wire specimens were made from heat set nitinol wire. The study explored the hypothesis that duty cycling can have an effect on nitinol fatigue life. Stent-like structures were subjected to different in vivo loadings in order to create more complex strain amplitudes. The main focus in this study was to determine whether a combination of small and large amplitudes causes additional damage that alters the fatigue life of a component.

  7. Three Dimensional Constraint Effects on the Estimated (Delta)CTOD during the Numerical Simulation of Different Fatigue Threshold Testing Techniques

    NASA Technical Reports Server (NTRS)

    Seshadri, Banavara R.; Smith, Stephen W.

    2007-01-01

    Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is

  8. Experimental electrochemical capacitor test results

    SciTech Connect

    Wright, R.B.; Murphy, T.C.; Rogers, S.A.; Sutula, R.A.

    1998-07-01

    Various electrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the Partnership for a New Generation of Vehicles (PNGV) fast-response engine. The envisioned primary functions of the ultracapacitor are to level the dynamic power loads on the primary propulsion device and recover available energy from regenerative breaking during off-peak power periods. This paper will present test data from selected US Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements. This paper will address the temperature dependence of test data obtained from a set of three devices provided from Maxwell Energy Products, Inc. These devices are rated at 2,300 F at 2.3 V. Constant-current, constant-power, and self-discharge testing as a function of temperature have been conducted. From these tests were determined the capacitance, equivalent series resistance, specific energy and power, and the self-discharge energy loss factor as a function of the device operating temperature.

  9. Ultrasonic Transducer Irradiation Test Results

    SciTech Connect

    Daw, Joshua; Palmer, Joe; Ramuhalli, Pradeep; Keller, Paul; Montgomery, Robert; Chien, Hual-Te; Kohse, Gordon; Tittmann, Bernhard; Reinhardt, Brian; Rempe, Joy

    2015-02-01

    Ultrasonic technologies offer the potential for high-accuracy and -resolution in-pile measurement of a range of parameters, including geometry changes, temperature, crack initiation and growth, gas pressure and composition, and microstructural changes. Many Department of Energy-Office of Nuclear Energy (DOE-NE) programs are exploring the use of ultrasonic technologies to provide enhanced sensors for in-pile instrumentation during irradiation testing. For example, the ability of small diameter ultrasonic thermometers (UTs) to provide a temperature profile in candidate metallic and oxide fuel would provide much needed data for validating new fuel performance models. Other ongoing efforts include an ultrasonic technique to detect morphology changes (such as crack initiation and growth) and acoustic techniques to evaluate fission gas composition and pressure. These efforts are limited by the lack of identified ultrasonic transducer materials capable of long term performance under irradiation test conditions. For this reason, the Pennsylvania State University (PSU) was awarded an ATR NSUF project to evaluate the performance of promising magnetostrictive and piezoelectric transducers in the Massachusetts Institute of Technology Research Reactor (MITR) up to a fast fluence of at least 1021 n/cm2. The goal of this research is to characterize and demonstrate magnetostrictive and piezoelectric transducer operation during irradiation, enabling the development of novel radiation-tolerant ultrasonic sensors for use in Material Testing Reactors (MTRs). As such, this test is an instrumented lead test and real-time transducer performance data is collected along with temperature and neutron and gamma flux data. The current work bridges the gap between proven out-of-pile ultrasonic techniques and in-pile deployment of ultrasonic sensors by acquiring the data necessary to demonstrate the performance of ultrasonic transducers. To date, one piezoelectric

  10. Fracture mechanics characterization of welds: Fatigue life analysis of notches at welds: J(sub Ic) fracture toughness tests for weld metal

    NASA Astrophysics Data System (ADS)

    Underwood, John H.

    1995-03-01

    In this report two methods of fracture analysis of welds will be emphasized, one addressing fatigue life testing and analysis of notches at welds, and the other addressing the final fracture of the welded component and the fracture toughness tests used to characterize final fracture. These fatigue and fracture methods will be described by referring to recent work from the technical literature and from the U.S. Army Armament Research, Development, and Engineering Center, primarily fracture case study and fracture test method development investigations. A brief general summary will be given of fatigue and fracture methods and concepts that have application to welded structures. Specific fatigue crack initiation tests and analysis methods will be presented, using example results from a welded stainless steel box beam of a cannon carriage. Recent improvements and simplifications in J.integral fracture toughness tests will be described, particularly those related to welds. Fracture toughness measurements for various stainless steel weld metals and heat treatments will also be described.

  11. Mars Balloon Flight Test Results

    NASA Technical Reports Server (NTRS)

    Hall, Jeffery L.; Pauken, Michael T.; Kerzhanovich, Viktor V.; Walsh, Gerald J.; Kulczycki, Eric A.; Fairbrother, Debora; Shreves, Chris; Lachenmeier, Tim

    2009-01-01

    This paper describes a set of four Earth atmosphere flight test experiments on prototype helium superpressure balloons designed for Mars. Three of the experiments explored the problem of aerial deployment and inflation, using the cold, low density environment of the Earth's stratosphere at an altitude of 30-32 km as a proxy for the Martian atmosphere. Auxiliary carrier balloons were used in three of these test flights to lift the Mars balloon prototype and its supporting system from the ground to the stratosphere where the experiment was conducted. In each case, deployment and helium inflation was initiated after starting a parachute descent of the payload at 5 Pa dynamic pressure, thereby mimicking the conditions expected at Mars after atmospheric entry and high speed parachute deceleration. Upward and downward looking video cameras provided real time images from the flights, with additional data provided by onboard temperature, pressure and GPS sensors. One test of a 660 cc pumpkin balloon was highly successful, achieving deployment, inflation and separation of the balloon from the flight train at the end of inflation; however, some damage was incurred on the balloon during this process. Two flight tests of 12 m diameter spherical Mylar balloons were not successful, although some lessons were learned based on the failure analyses. The final flight experiment consisted of a ground-launched 12 m diameter spherical Mylar balloon that ascended to the designed 30.3 km altitude and successfully floated for 9.5 hours through full noontime daylight and into darkness, after which the telemetry system ran out of electrical power and tracking was lost. The altitude excursions for this last flight were +/-75 m peak to peak, indicating that the balloon was essentially leak free and functioning correctly. This provides substantial confidence that this balloon design will fly for days or weeks at Mars if it can be deployed and inflated without damage.

  12. Rolling contact fatigue of surface modified 440C using a 'Ge-Polymet' type disc rod test rig

    NASA Technical Reports Server (NTRS)

    Thom, Robert L.

    1989-01-01

    Through hardened 440 C martensitic stainless steel test specimens were surface modified and tested for changes in rolling contact fatigue using a disc on rod test rig. The surface modifications consisted of nitrogen, boron, titanium, chromium, tantalum, carbon, or molybdenum ion implantation at various ion fluences and energies. Tests were also performed on specimens reactively sputtered with titanium nitride.

  13. Rolling contact fatigue of surface modified 440C using a 'Ge-Polymet' type disc rod test rig

    SciTech Connect

    Thom, R.L.

    1989-03-01

    Through hardened 440 C martensitic stainless steel test specimens were surface modified and tested for changes in rolling contact fatigue using a disc on rod test rig. The surface modifications consisted of nitrogen, boron, titanium, chromium, tantalum, carbon, or molybdenum ion implantation at various ion fluences and energies. Tests were also performed on specimens reactively sputtered with titanium nitride.

  14. Results of Neptunium Disposal Testing

    SciTech Connect

    Walker, D.D.

    2003-10-07

    Researchers investigated the neutralization of neptunium solution from H-Canyon Tank 16.4 and the properties of the resulting slurry. This work investigated slurry properties from a single neutralization protocol and limited storage times.

  15. Statistical characterization of the fatigue behavior of composite lamina

    NASA Technical Reports Server (NTRS)

    Yang, J. N.; Jones, D. L.

    1979-01-01

    A theoretical model was developed to predict statistically the effects of constant and variable amplitude fatigue loadings on the residual strength and fatigue life of composite lamina. The parameters in the model were established from the results of a series of static tensile tests and a fatigue scan and a number of verification tests were performed. Abstracts for two other papers on the effect of load sequence on the statistical fatigue of composites are also presented.

  16. Axial Fatigue Tests at Zero Mean Stress of 24S-T and 75S-T Aluminum-alloy Strips with a Central Circular Hole

    NASA Technical Reports Server (NTRS)

    Brueggeman, W C; Mayer, M JR

    1948-01-01

    Axial fatigue tests at zero mean stress have been made on 0.032- and 0.064-inch 24S-T and 0.032-inch 75S-T sheet-metal specimens 1/4, 1/2, 1, and 2 inches wide without a hole and with central holes giving a range of hole diameter D to specimen width W from 0.01 to 0.95. No systematic difference was noted between the results for the 0.032-inch and the 0.064-inch specimens although the latter seemed the more consistent. In general the fatigue strength based on the minimum section dropped sharply as the ration D/W was increased from zero to about 0.25. The plain specimens showed quite a pronounced decrease in fatigue strength with increasing width. The holed specimens showed only slight and rather inconclusive evidence of this size effect. The fatigue stress-concentration factor was higher for 75S-T than for 24S-T alloy. Evidence was found that a very small hole would not cause any reduction in fatigue strength.

  17. Wind turbine blade fatigue tests: lessons learned and application to SHM system development

    SciTech Connect

    Taylor, Stuart G.; Farinholt, Kevin M.; Jeong, Hyomi; Jang, JaeKyung; Park, Gyu Hae; Todd, Michael D.; Farrar, Charles R.; Ammerman, Curtt N.

    2012-06-28

    This paper presents experimental results of several structural health monitoring (SHM) methods applied to a 9-meter CX-100 wind turbine blade that underwent fatigue loading. The blade was instrumented with piezoelectric transducers, accelerometers, acoustic emission sensors, and foil strain gauges. It underwent harmonic excitation at its first natural frequency using a hydraulically actuated resonant excitation system. The blade was initially excited at 25% of its design load, and then with steadily increasing loads until it failed. Various data were collected between and during fatigue loading sessions. The data were measured over multiple frequency ranges using a variety of acquisition equipment, including off-the-shelf systems and specially designed hardware developed by the authors. Modal response, diffuse wave-field transfer functions, and ultrasonic guided wave methods were applied to assess the condition of the wind turbine blade. The piezoelectric sensors themselves were also monitored using a sensor diagnostics procedure. This paper summarizes experimental procedures and results, focusing particularly on fatigue crack detection, and concludes with considerations for implementing such damage identification systems, which will be used as a guideline for future SHM system development for operating wind turbine blades.

  18. Anti-fatigue effects of porcine placenta and its amino acids in a behavioral test on mice.

    PubMed

    Moon, Phil-Dong; Kim, Kyu-Yeob; Rew, Keun-Ho; Kim, Hyung-Min; Jeong, Hyun-Ja

    2014-11-01

    Placenta extracts are used for their health benefits; however, the anti-fatigue effects of placenta have not been elucidated. Thus, we investigated the anti-fatigue effects of porcine placenta extract (PE) and the amino acids present in the PE (glycine, Gly; proline, Pro; glutamic acid, GA; and arginine, Arg) using a forced swimming test (FST) and a tail-suspension test (TST) on mice. Whole PE or individual amino acids decreased immobility times in the FST. PE, Pro, and Arg all lowered blood levels of lactic acid and alanine aminotransferase (ALT). PE and Gly improved glycogen content and catalase activity. As determined from the serum after the FST: PE regulated the effects of interferon (IFN)-γ and tumor necrosis factor (TNF)-α; GA regulated the effects of IFN-γ; Gly and Arg regulated the effects of interleukin (IL)-6; and all of the amino acids present in PE regulated the effects of TNF-α. As determined from the spleen after the FST: Gly and Arg regulated the effects of IL-1β; Gly, Pro, and Arg regulated the effects of IL-6; PE and all of the amino acids present in PE regulated the effects of TNF-α. After the TST, PE and all of the amino acids present in PE reduced immobility duration as well as levels of aspartate aminotransferase and ALT. As determined from the serum after the TST: PE and Gly regulated the effects of TNF-α; Gly and Arg regulated the effects of IL-1β; Gly, Pro, and Arg regulated the effects of IL-6; PE and all of the amino acids present in PE regulated the effects of TNF-α. These results suggest that PE should be considered a candidate anti-fatigue agent. PMID:25347266

  19. Fitness for duty: A 3 minute version of the Psychomotor Vigilance Test predicts fatigue related declines in luggage screening performance

    PubMed Central

    Basner, Mathias; Rubinstein, Joshua

    2011-01-01

    Objective To evaluate the ability of a 3-min Psychomotor Vigilance Test (PVT) to predict fatigue related performance decrements on a simulated luggage screening task (SLST). Methods Thirty-six healthy non-professional subjects (mean age 30.8 years, 20 female) participated in a 4 day laboratory protocol including a 34 hour period of total sleep deprivation with PVT and SLST testing every 2 hours. Results Eleven and 20 lapses (355 ms threshold) on the PVT optimally divided SLST performance into high, medium, and low performance bouts with significantly decreasing threat detection performance A′. Assignment to the different SLST performance groups replicated homeostatic and circadian patterns during total sleep deprivation. Conclusions The 3 min PVT was able to predict performance on a simulated luggage screening task. Fitness-for-duty feasibility should now be tested in professional screeners and operational environments. PMID:21912278

  20. Thermal fatigue tests of a radiative heat shield panel for a hypersonic transport

    NASA Technical Reports Server (NTRS)

    Webb, Granville L.; Clark, Ronald K.; Sharpe, Ellsworth L.

    1985-01-01

    A pair of corrugation stiffened, beaded skin Rene 41 heat shield panels were exposed to 20,000 thermal cycles between room temperature and 1450 F to evaluate the thermal fatigue response of Rene 41 metallic heat shields for hypersonic cruise aircraft applications. At the conclusion of the tests, the panels retained substantial structural integrity; however, there were cracks and excessive wear in the vicinity of fastener holes and there was an 80-percent loss in ductility of the skin. Shrinkage of the panel which caused the cracks and wear must be considered in design of panels for Thermal Protection Systems (TPS) applications.

  1. Periodic Overload and Transport Spectrum Fatigue Crack Growth Tests of Ti62222STA and Al2024T3 Sheet

    NASA Technical Reports Server (NTRS)

    Phillips, Edward P.

    1999-01-01

    Variable amplitude loading crack growth tests have been conducted to provide data that can be used to evaluate crack growth prediction codes. Tests with periodic overloads or overloads followed by underloads were conducted on titanium alloy Ti-6Al-2Sn-2Zr-2Mo-2Cr solution treated and aged (Ti62222STA) material at room temperature and at 350 F. Spectrum fatigue crack growth tests were conducted on two materials (Ti62222STA and aluminum alloy 2024-T3) using two transport lower-wing test spectra at two temperatures (room temperature and 350 F (Ti only)). Test lives (growth from an initial crack half-length of 0.15 in. to failure) were recorded in all tests and the crack length against cycles (or flights) data were recorded in many of the tests. The following observations were made regarding the test results: (1) in tests of the Ti62222STA material, the tests at 350 F had longer lives than those at room temperature, (2) in tests to the MiniTwist spectrum, the Al2024T3 material showed much greater crack growth retardations due to the highest stresses in the spectrum than did the Ti62222STA material, and (3) comparisons of material crack growth performances on an "equal weight" basis were spectrum dependent.

  2. A pilot study to test psychophonetics methodology for self-care and empathy in compassion fatigue, burnout and secondary traumatic stress

    PubMed Central

    Butler, Nadine

    2013-01-01

    Abstract Background Home-based care is recognised as being a stressful occupation. Practitioners working with patients experiencing high levels of trauma may be susceptible to compassion fatigue, with the sustained need to remain empathic being a contributing factor. Objectives The aim of this research was to evaluate psychophonetics methodology for self-care and empathy skills as an intervention for compassion fatigue. Objectives were to measure levels of compassion fatigue pre-intervention, then to apply the intervention and retest levels one month and six months post-intervention. Method The research applied a pilot test of a developed intervention as a quasi-experiment. The study sample comprised home-based carers working with HIV-positive patients at a hospice in Grabouw, a settlement in the Western Cape facing socioeconomic challenge. Results The result of the pilot study showed a statistically-significant improvement in secondary traumatic stress, a component of compassion fatigue, measured with the ProQOL v5 instrument post-intervention. Conclusion The results gave adequate indication for the implementation of a larger study in order to apply and test the intervention. The study highlights a dire need for further research in this field.

  3. Refinements and Tests of an Advanced Controller to Mitigate Fatigue Loads in the Controls Advanced Research Turbine: Preprint

    SciTech Connect

    Wright, A.; Fleming, P.

    2010-12-01

    Wind turbines are complex, nonlinear, dynamic systems forced by aerodynamic, gravitational, centrifugal, and gyroscopic loads. The aerodynamics of wind turbines are nonlinear, unsteady, and complex. Turbine rotors are subjected to a complicated 3-D turbulent wind inflow field, with imbedded coherent vortices that drive fatigue loads and reduce lifetime. Design of control algorithms for wind turbines must account for multiple control objectives. Future large multi-megawatt turbines must be designed with lighter weight structures, using active controls to mitigate fatigue loads, while maximizing energy capture. Active damping should be added to these dynamic structures to maintain stability for operation in a complex environment. At the National Renewable Energy Laboratory (NREL), we have designed, implemented, and tested advanced controls to maximize energy extraction and reduce structural dynamic loads. These control designs are based on linear models of the turbine that are generated by specialized modeling software. In this paper, we present field test results of an advanced control algorithm to mitigate blade, tower, and drivetrain loads in Region 3.

  4. Surface fatigue life of carburized and hardened M50NiL and AISI 9310 spur gears and rolling-contact test bars

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis P.; Bamberger, Eric N.

    1989-01-01

    Spur gear endurance tests and rolling-element surface tests were conducted to investigate vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M50NiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIM-VAR AISI 9310 gear material. Tests were conducted with spur gears and rolling-contact bars manufactured from VIM-VAR M50NiL and VAR and VIM-VAR AISI 9310. The gear pitch diameter was 8.9 cm (3.5 in.). Gear test conditions were an inlet oil temperature of 320 K (116 F), and outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench rolling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPA (700 ksi). The VIM-VAR M50NiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR M50NiL rolling-contact bars was 13.2 and 21.6 times that for the VIM-VAR and VAR AISI 9310, respectively. The VIM-VAR M50NiL material was shown to have good resistance to fracture through a fatigue spall and to have fatigue life far superior to that of both VIM-VAR and VAR AISI 9310 gears and rolling-contact bars.

  5. Probabilistic Fatigue: Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2002-01-01

    Fatigue is a primary consideration in the design of aerospace structures for long term durability and reliability. There are several types of fatigue that must be considered in the design. These include low cycle, high cycle, combined for different cyclic loading conditions - for example, mechanical, thermal, erosion, etc. The traditional approach to evaluate fatigue has been to conduct many tests in the various service-environment conditions that the component will be subjected to in a specific design. This approach is reasonable and robust for that specific design. However, it is time consuming, costly and needs to be repeated for designs in different operating conditions in general. Recent research has demonstrated that fatigue of structural components/structures can be evaluated by computational simulation based on a novel paradigm. Main features in this novel paradigm are progressive telescoping scale mechanics, progressive scale substructuring and progressive structural fracture, encompassed with probabilistic simulation. These generic features of this approach are to probabilistically telescope scale local material point damage all the way up to the structural component and to probabilistically scale decompose structural loads and boundary conditions all the way down to material point. Additional features include a multifactor interaction model that probabilistically describes material properties evolution, any changes due to various cyclic load and other mutually interacting effects. The objective of the proposed paper is to describe this novel paradigm of computational simulation and present typical fatigue results for structural components. Additionally, advantages, versatility and inclusiveness of computational simulation versus testing are discussed. Guidelines for complementing simulated results with strategic testing are outlined. Typical results are shown for computational simulation of fatigue in metallic composite structures to demonstrate the

  6. Abnormal Resting-State Functional Connectivity in Patients with Chronic Fatigue Syndrome: Results of Seed and Data-Driven Analyses.

    PubMed

    Gay, Charles W; Robinson, Michael E; Lai, Song; O'Shea, Andrew; Craggs, Jason G; Price, Donald D; Staud, Roland

    2016-02-01

    Although altered resting-state functional connectivity (FC) is a characteristic of many chronic pain conditions, it has not yet been evaluated in patients with chronic fatigue. Our objective was to investigate the association between fatigue and altered resting-state FC in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Thirty-six female subjects, 19 ME/CFS and 17 healthy controls, completed a fatigue inventory before undergoing functional magnetic resonance imaging. Two methods, (1) data driven and (2) model based, were used to estimate and compare the intraregional FC between both groups during the resting state (RS). The first approach using independent component analysis was applied to investigate five RS networks: the default mode network, salience network (SN), left frontoparietal networks (LFPN) and right frontoparietal networks, and the sensory motor network (SMN). The second approach used a priori selected seed regions demonstrating abnormal regional cerebral blood flow (rCBF) in ME/CFS patients at rest. In ME/CFS patients, Method-1 identified decreased intrinsic connectivity among regions within the LFPN. Furthermore, the FC of the left anterior midcingulate with the SMN and the connectivity of the left posterior cingulate cortex with the SN were significantly decreased. For Method-2, five distinct clusters within the right parahippocampus and occipital lobes, demonstrating significant rCBF reductions in ME/CFS patients, were used as seeds. The parahippocampal seed and three occipital lobe seeds showed altered FC with other brain regions. The degree of abnormal connectivity correlated with the level of self-reported fatigue. Our results confirm altered RS FC in patients with ME/CFS, which was significantly correlated with the severity of their chronic fatigue. PMID:26449441

  7. Design and fabrication of a unique electromechanical machine for long-term fatigue testing

    SciTech Connect

    Boling, K.W.

    1984-12-01

    An electromechanical machine has been designed and fabricated for performing long-term fatigue tests under conditions that simulate those in modern plants. The machine is now commercially available. Its advantages over current electrohydraulic machines are lower initial cost, minimum maintenance requirements, and greater reliability especially when performing long tests. The machine operates in closed-loop fashion by utilizing continuous feedback signals from the specimen extensometer or load cell, it is programmable for testing in strain or load control. The maximum ram rate is 0.056 mm/s (0.134 in./min), maximum ram travel is 102 mm (4 in.) and load capacity is +-44 (+-10 kips). Induction heating controls speciment temperatures to 1000/sup 0/C.

  8. A novel noncontact electromagnetic field-based sensor for the monitoring of resonant fatigue tests

    NASA Astrophysics Data System (ADS)

    Nam, Si-Byung; Yun, Gun Jin; Carletta, Joan; Kim, Dong-Han; Binienda, Wieslaw

    2011-03-01

    In this paper, a prototype of an electromagnetic field-based (EFB) vibration sensor that uses a novel sensing technique to monitor the resonant fatigue testing of a conductive and/or ferromagnetic target specimen is presented. The distance from the target to a coil within the sensor affects the impedance of the coil. The electronic circuitry for the sensor consists of a relaxation oscillator, an embedded microprocessor module and a high-speed digital-to-analog converter. The impedance of the coil determines the frequency of oscillation of the relaxation oscillator's output, so that vibration of the target causes changes in the oscillation frequency. A timer in the embedded microprocessor module is used to count the oscillations, producing a digital signal that indicates the coil-to-target distance. The digital signal is instantaneously converted to an analog signal to produce the sensor's output. The key technologies proposed include: (1) a novel timer counting method using the input capture functionality and timer of the embedded microprocessor module and (2) significant simplification of the analog electronic circuitry. The performance of the proposed sensor has been verified using AISI 1095 carbon steel and Al6061-T6 aluminum alloy specimens during resonant fatigue tests. The sensor shows a good linearity between displacement amplitudes and output voltages.

  9. Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin

    2000-01-01

    A methodology is presented for determining the fatigue life of bonded composite skin/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange/skin specimens to verify the approach.

  10. 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.

  11. Fatigue loading of tendon

    PubMed Central

    Shepherd, Jennifer H; Screen, Hazel R C

    2013-01-01

    Tendon injuries, often called tendinopathies, are debilitating and painful conditions, generally considered to develop as a result of tendon overuse. The aetiology of tendinopathy remains poorly understood, and whilst tendon biopsies have provided some information concerning tendon appearance in late-stage disease, there is still little information concerning the mechanical and cellular events associated with disease initiation and progression. Investigating this in situ is challenging, and numerous models have been developed to investigate how overuse may generate tendon fatigue damage and how this may relate to tendinopathy conditions. This article aims to review these models and our current understanding of tendon fatigue damage. We review the strengths and limitations of different methodologies for characterizing tendon fatigue, considering in vitro methods that adopt both viable and non-viable samples, as well as the range of different in vivo approaches. By comparing data across model systems, we review the current understanding of fatigue damage development. Additionally, we compare these findings with data from tendinopathic tissue biopsies to provide some insights into how these models may relate to the aetiology of tendinopathy. Fatigue-induced damage consistently highlights the same microstructural, biological and mechanical changes to the tendon across all model systems and also correlates well with the findings from tendinopathic biopsy tissue. The multiple testing routes support matrix damage as an important contributor to tendinopathic conditions, but cellular responses to fatigue appear complex and often contradictory. PMID:23837793

  12. Static and fatigue testing of full-scale fuselage panels fabricated using a Therm-X(R) process

    NASA Technical Reports Server (NTRS)

    Dinicola, Albert J.; Kassapoglou, Christos; Chou, Jack C.

    1992-01-01

    Large, curved, integrally stiffened composite panels representative of an aircraft fuselage structure were fabricated using a Therm-X process, an alternative concept to conventional two-sided hard tooling and contour vacuum bagging. Panels subsequently were tested under pure shear loading in both static and fatigue regimes to assess the adequacy of the manufacturing process, the effectiveness of damage tolerant design features co-cured with the structure, and the accuracy of finite element and closed-form predictions of postbuckling capability and failure load. Test results indicated the process yielded panels of high quality and increased damage tolerance through suppression of common failure modes such as skin-stiffener separation and frame-stiffener corner failure. Finite element analyses generally produced good predictions of postbuckled shape, and a global-local modelling technique yielded failure load predictions that were within 7% of the experimental mean.

  13. Preliminary Fatigue Studies on Aluminum Alloy Aircraft Engines

    NASA Technical Reports Server (NTRS)

    1938-01-01

    Preliminary information on the complex subject of the fatigue strength of fabricated structural members for aircraft is presented in the test results obtained on several different types of airship girders subjected to axial tension and compression in a resonance fatigue machine. A description of this machine as well as numerous photographs of the fatigue failures are given. There is also presented an extended bibliography on the subject of fatigue strength.

  14. Thermal Fatigue and Fracture Behavior of Ceramic Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Choi, Sung R.; Miller, Robert A.

    2001-01-01

    Thermal fatigue and fracture behavior of plasma-sprayed ceramic thermal barrier coatings has been investigated under high heat flux and thermal cyclic conditions. The coating crack propagation is studied under laser heat flux cyclic thermal loading, and is correlated with dynamic fatigue and strength test results. The coating stress response and inelasticity, fatigue and creep interactions, and interface damage mechanisms during dynamic thermal fatigue processes are emphasized.

  15. Measurement of Deflection in Concrete Beams During Fatigue Loading Test Using the Microsoft Kinect 2.0

    NASA Astrophysics Data System (ADS)

    Lahamy, Herve; Lichti, Derek D.; Steward, Jeremy; El-Badry, Mamdouh; Moravvej, Mohammad

    2016-03-01

    This study focuses on 3 Hz fatigue load testing of a reinforced concrete beam in laboratory conditions. Three-dimensional (3D) image time series of the beam's top surface were captured with the Microsoft time-of-flight Kinect 2.0 sensor. To estimate the beam deflection, the imagery was first segmented to extract the top surface of the beam. The centre line was then modeled using third-order B-splines. The deflection of the beam as a function of time was estimated from the modeled centre line and, following past practice, also at several witness plates attached to the side of the beam. Subsequent correlation of the peak displacement with the applied loading cycles permitted estimation of fatigue in the beam. The accuracy of the deflections was evaluated by comparison with the measurements obtained using a Keyence LK-G407 laser displacement sensors. The results indicate that the deflections can be recovered with sub-millimetre accuracy using the centreline profile modelling method.

  16. 40 CFR 799.12 - Test results.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 33 2013-07-01 2013-07-01 false Test results. 799.12 Section 799.12...) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.12 Test results. Except as set forth in specific chemical test rules in subpart B of this part, a positive...

  17. 40 CFR 799.12 - Test results.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 32 2011-07-01 2011-07-01 false Test results. 799.12 Section 799.12...) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.12 Test results. Except as set forth in specific chemical test rules in subpart B of this part, a positive...

  18. 40 CFR 799.12 - Test results.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 32 2014-07-01 2014-07-01 false Test results. 799.12 Section 799.12...) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.12 Test results. Except as set forth in specific chemical test rules in subpart B of this part, a positive...

  19. Fatigue and creep to leak tests of proton exchange membranes using pressure-loaded blisters

    NASA Astrophysics Data System (ADS)

    Li, Yongqiang; Dillard, David A.; Case, Scott W.; Ellis, Michael W.; Lai, Yeh-Hung; Gittleman, Craig S.; Miller, Daniel P.

    In this study, three commercially available proton exchange membranes (PEMs) are biaxially tested using pressure-loaded blisters to characterize their resistance to gas leakage under either static (creep) or cyclic fatigue loading. The pressurizing medium, air, is directly used for leak detection. These tests are believed to be more relevant to fuel cell applications than quasi-static uniaxial tensile-to-rupture tests because of the use of biaxial cyclic and sustained loading and the use of gas leakage as the failure criterion. They also have advantages over relative humidity cycling test, in which a bare PEM or catalyst coated membrane is clamped with gas diffusion media and flow field plates and subjected to cyclic changes in relative humidity, because of the flexibility in allowing controlled mechanical loading and accelerated testing. Nafion ® NRE-211 membranes are tested at three different temperatures and the time-temperature superposition principle is used to construct stress-lifetime master curve. Tested at 90 °C, 2%RH extruded Ion Power ® N111-IP membranes have a longer lifetime than Gore™-Select ® 57 and Nafion ® NRE-211 membranes.

  20. Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

    2001-01-01

    Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high

  1. Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin; Minguet, Pierre J.

    2001-01-01

    A methodology is presented for determining the fatigue life of composite structures based on fatigue characterization data and geometric nonlinear finite element (FE) analyses. To demonstrate the approach, predicted results were compared to fatigue tests performed on specimens which represented a tapered composite flange bonded onto a composite skin. In a first step, tension tests were performed to evaluate the debonding mechanisms between the flange and the skin. In a second step, a 2D FE model was developed to analyze the tests. To predict matrix cracking onset, the relationship between the tension load and the maximum principal stresses transverse to the fiber direction was determined through FE analysis. Transverse tension fatigue life data were used to -enerate an onset fatigue life P-N curve for matrix cracking. The resulting prediction was in good agreement with data from the fatigue tests. In a third step, a fracture mechanics approach based on FE analysis was used to determine the relationship between the tension load and the critical energy release rate. Mixed mode energy release rate fatigue life data were used to create a fatigue life onset G-N curve for delamination. The resulting prediction was in good agreement with data from the fatigue tests. Further, the prediction curve for cumulative life to failure was generated from the previous onset fatigue life curves. The results showed that the methodology offers a significant potential to Predict cumulative fatigue life of composite structures.

  2. Low cycle thermal fatigue testing of beryllium grades for ITER plasma facing components

    SciTech Connect

    Watson, R.D.; Youchison, D.L.; Dombrowski, D.E.; Guiniatouline, R.N.; Kupriynov, I.B.

    1996-02-01

    A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ``spike`` of 750{degree}C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m{sup 2}. Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S- 65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HIP`d spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe{sub 12}. Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis.

  3. Nonlinear vibration caused by fatigue

    NASA Astrophysics Data System (ADS)

    Foong, Chee-Hoe; Wiercigroch, Marian; Pavlovskaia, Ekaterina; Deans, William F.

    2007-06-01

    The main aim of this work is to study the interactions between vibration and fatigue crack growth. In this paper, a detailed mathematical modelling of a newly designed fatigue-testing rig, description of the rig, experimental set-up and procedures, and sensor calibrations are presented. The test rig consists of two base-excited oscillators, one positioned above and the other below a single-edge-notched beam sample. The inertial forces of the oscillators act on the sample causing its bending and fatigue. Mathematically the fatigue crack sample is modelled as a discrete spring with piecewise nonlinear stiffness which is assumed to be constant when the crack closes and to decrease with crack length when it opens. The results from the modelling correlate well with the experimental tests.

  4. Low cycle fatigue

    NASA Technical Reports Server (NTRS)

    Solomon, H. D. (Editor); Kaisand, L. R. (Editor); Halford, G. R. (Editor); Leis, B. N. (Editor)

    1988-01-01

    The papers contained in this volume focus on various aspects of low cycle fatigue, including cyclic deformation, crack propagation, high-temperature low cycle fatigue, microstructural defects, multiaxial and variable amplitude loading, and life prediction. Papers are presented on the low cycle fatigue of some aluminum alloys, prediction of crack growth under creep-fatigue loading conditions, high-temperature low cycle fatigue behavior and lifetime prediction of a nickel-base ODS alloy, and an integrated approach to creep-fatigue life prediction. Other topics discussed include thermal fatigue testing of coated monocrystalline superalloys, low cycle fatigue of Al-Mg-Si alloys, and the effect of superimposed stresses at high frequency on low cycle fatigue.

  5. High temperature, low cycle fatigue of copper-base alloys in argon. Part 3: Zirconium-copper; thermal-mechanical strain cycling, hold-time and notch fatigue results

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1973-01-01

    The low-cycle fatigue characteristics of smooth bar and notched bar specimens (hourglass shape) of zirconium-copper, 1/2 Hard, material (R-2 Series) were evaluated at room temperature in axial strain control. Over the fatigue life range from about 300 to 3000 cycles the ratio of fatigue life for smooth bar to fatigue life for notched bar remained constant at a value of about 6.0. Some additional hold-time data for the R-2 alloy tested in argon at 538 C are reported. An analysis of the relaxation data obtained in these hold-time tests is also reported and it is shown that these data yield a fairly consistent correlation in terms of instantaneous stress rate divided by instantaneous stress. Two thermal-mechanical strain cycling tests were also performed using a cyclic frequency of 4.5 cycles per hour and a temperature cycling interval from 260 to 538 C. The fatigue life values in these tests were noticeably lower than that observed in isothermal tests at 538 C.

  6. Test 6, Test 7, and Gas Standard Analysis Results

    NASA Technical Reports Server (NTRS)

    Perez, Horacio, III

    2007-01-01

    This viewgraph presentation shows results of analyses on odor, toxic off gassing and gas standards. The topics include: 1) Statistical Analysis Definitions; 2) Odor Analysis Results NASA Standard 6001 Test 6; 3) Toxic Off gassing Analysis Results NASA Standard 6001 Test 7; and 4) Gas Standard Results NASA Standard 6001 Test 7;

  7. Random Vibration Tests for Prediction of Fatigue Life of Diffuser Structure for Gas Dynamic Laser

    NASA Astrophysics Data System (ADS)

    Maurer, O. F.; Banaszak, D. L.

    1980-01-01

    Static and dynamic strain measurements which were taken during test stand operations of the gas dynamic laser (GDL) for the AF Airborne Laser Laboratory indicated that higher than expected vibrational stress levels may possibly limit the fatigue life of the laser structure. Particularly the diffuser sidewall structure exhibited large amplitude random vibrations which were excited by the internal gas flow. The diffuser structure consists of two layers of brazed stainless steel, AISI-347, panels. Cooling ducts were milled into the outer face sheet. These in turn are backed by the inner face sheet. So called T-rail stiffeners silver-brazed to the outer face sheets add the required stiffness and divide the sidewall into smaller rectangular plate sections.

  8. Effect of Test Frequency on Fatigue Crack Growth Rates of Ti-6Al-4V ELI Alloy at Cryogenic Temperature

    SciTech Connect

    Yuri, T.; Ono, Y.; Ogata, T.

    2006-03-31

    In order to clarify the effect of test frequency on the fatigue crack growth rates (da/dN) of Ti-6Al-4V ELI alloy have been investigated at cryogenic temperature. The fatigue crack growth tests were conducted using the test frequencies of 5 and 20 Hz, respectively. At 4 K, the effects of the test frequencies on the fatigue crack growth rates of Ti-6Al-4V ELI alloy were not clear or significant. The fatigue crack growth rates in the low propagation rate region at 4 K were smaller than those at 293 K. On the other hand, those in the high propagation rate region at 4 K were bigger than those at 293 K. The former is considered that the crack closure level was higher as compared to that at 293 K and the latter is due to the difference values of the fracture toughness at 4 and 293 K, respectively. The fracture surfaces of compact tension (CT) specimens in the high propagation rate regions at each test temperature revealed the striations, and furthermore accompanied with the flute fracture surface at 4 K. On the other hand, those of CT specimens in the low propagation rate region at 4 K were found facet-like fracture surfaces corresponding with almost the {alpha}-grain size.

  9. Acoustic emission monitoring of a wind turbine blade during a fatigue test

    SciTech Connect

    Beattie, A.G.

    1997-01-01

    A fatigue test of a wind turbine blade was conducted at the National Renewable Energy Laboratory in the fall of 1994. Acoustic emission monitoring of the test was performed, starting with the second loading level. The acoustic emission data indicated that this load exceeded the strength of the blade. From the first cycle at the new load, an oil can type of deformation occurred in two areas of the upper skin of the blade. One of these was near the blade root and the other was about the middle of the tested portion of the blade. The emission monitoring indicated that no damage was taking place in the area near the root, but in the deforming area near the middle of the blade, damage occurred from the first cycles at the higher load. The test was stopped after approximately one day and the blade was declared destroyed, although no gross damage had occurred. Several weeks later the test was resumed, to be continued until gross damage occurred. The upper skin tore approximately one half hour after the cycling was restarted.

  10. An advanced test technique to quantify thermomechanical fatigue damage accumulation in composite materials

    NASA Technical Reports Server (NTRS)

    Castelli, Michael G.

    1993-01-01

    A mechanical test technique was developed to assist in quantifying the accumulation of damage in composite materials during thermomechanical fatigue (TMF) cycling. This was accomplished by incorporating definitive elastic mechanical property measurements into an ongoing load-controlled TMF test without disturbing the test specimen or significantly altering the test conditions. The technique allows two fundamental composite properties consisting of the isothermal elastic static moduli and the macroscopic coefficient of thermal expansion (CTE) to be measured and collected as functions of the TMF cycles. The specific implementation was incorporated into the commonly employed idealized in-phase and out-of-phase TMF cycles. However, the techniques discussed could be easily implemented into any form of load-controlled TMF mission cycle. By quantifying the degradations of these properties, tremendous insights are gained concerning the progression of macroscopic composite damage and often times the progression of damage within a given constituent. This information should also be useful for the characterization and essential for the verification of analytical damage modeling methodologies. Several examples utilizing this test technique are given for three different fiber lay-ups of titanium metal matrix composites.

  11. Probabilistic fatigue methodology for six nines reliability

    NASA Technical Reports Server (NTRS)

    Everett, R. A., Jr.; Bartlett, F. D., Jr.; Elber, Wolf

    1990-01-01

    Fleet readiness and flight safety strongly depend on the degree of reliability that can be designed into rotorcraft flight critical components. The current U.S. Army fatigue life specification for new rotorcraft is the so-called six nines reliability, or a probability of failure of one in a million. The progress of a round robin which was established by the American Helicopter Society (AHS) Subcommittee for Fatigue and Damage Tolerance is reviewed to investigate reliability-based fatigue methodology. The participants in this cooperative effort are in the U.S. Army Aviation Systems Command (AVSCOM) and the rotorcraft industry. One phase of the joint activity examined fatigue reliability under uniquely defined conditions for which only one answer was correct. The other phases were set up to learn how the different industry methods in defining fatigue strength affected the mean fatigue life and reliability calculations. Hence, constant amplitude and spectrum fatigue test data were provided so that each participant could perform their standard fatigue life analysis. As a result of this round robin, the probabilistic logic which includes both fatigue strength and spectrum loading variability in developing a consistant reliability analysis was established. In this first study, the reliability analysis was limited to the linear cumulative damage approach. However, it is expected that superior fatigue life prediction methods will ultimately be developed through this open AHS forum. To that end, these preliminary results were useful in identifying some topics for additional study.

  12. Fatigue of continuous fiber reinforced metallic materials

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Mirdamadi, M.; Bakuckas, J. G., Jr.

    1993-01-01

    The complex damage mechanisms that occur in fiber reinforced advanced metallic materials are discussed. As examples, results for several layups of SCS-6/Ti-15-3 composites are presented. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room and elevated temperatures. Test conditions included isothermal, non-isothermal, and simulated mission profile thermomechanical fatigue. Test results indicated that the stress in the 0 degree fibers is the controlling factor for fatigue life for a given test condition. An effective strain approach is presented for predicting crack initiation at notches. Fiber bridging models were applied to crack growth behavior.

  13. Fatigue: an overview.

    PubMed

    Rosenthal, Thomas C; Majeroni, Barbara A; Pretorius, Richard; Malik, Khalid

    2008-11-15

    Fatigue, a common presenting symptom in primary care, negatively impacts work performance, family life, and social relationships. The differential diagnosis of fatigue includes lifestyle issues, physical conditions, mental disorders, and treatment side effects. Fatigue can be classified as secondary to other medical conditions, physiologic, or chronic. The history and physical examination should focus on identifying common secondary causes (e.g., medications, anemia, pregnancy) and life-threatening problems, such as cancer. Results of laboratory studies affect management in only 5 percent of patients, and if initial results are normal, repeat testing is generally not indicated. Treatment of all types of fatigue should include a structured plan for regular physical activity that consists of stretching and aerobic exercise, such as walking. Caffeine and modafinil may be useful for episodic situations requiring alertness. Short naps are proven performance enhancers. Selective serotonin reuptake inhibitors, such as fluoxetine, paroxetine, or sertraline, may improve energy in patients with depression. Patients with chronic fatigue may respond to cognitive behavior therapy. Scheduling regular follow-up visits, rather than sporadic urgent appointments, is recommended for effective long-term management. PMID:19035066

  14. An unsupervised pattern recognition approach for AE data originating from fatigue tests on polymer-composite materials

    NASA Astrophysics Data System (ADS)

    Doan, D. D.; Ramasso, E.; Placet, V.; Zhang, S.; Boubakar, L.; Zerhouni, N.

    2015-12-01

    This work investigates acoustic emission generated during tension fatigue tests carried out on a carbon fiber reinforced polymer (CFRP) composite specimen. Since massive fatigue data processing, especially noise reduction, remains an important challenge in AE data analysis, a Mahalanobis distance-based noise modeling has been proposed in the present work to tackle this problem. A sequential feature selection based on Davies-Bouldin index has been implemented for fast dimensionality reduction. An unsupervised classifier offline-learned from quasi-static data is then used to classify the data to different AE sources with the possibility to dynamically accommodate with unseen ones. With an efficient proposed noise removal and automatic separation of AE events, this pattern discovery procedure provides an insight into fatigue damage development in composites in the presence of millions of AE events.

  15. Postural Balance Following Aerobic Fatigue Tests: A Longitudinal Study Among Young Athletes.

    PubMed

    Steinberg, Nili; Eliakim, Alon; Zaav, Aviva; Pantanowitz, Michal; Halumi, Monder; Eisenstein, Tamir; Meckel, Yoav; Nemet, Dan

    2016-01-01

    General fatigue can cause aggravation of postural balance, with increased risk for injuries. The present longitudinal study aimed to evaluate the postural balance of young athletes following field aerobic tests throughout 1 year of training. Thirty children from a sports center in Nazareth, participating in a 3 times/week training program (specific to basketball, soccer, or athletic training), were assessed. Postural balance parameters were taken before, immediately after, and 10 min after a 20 m shuttle-run aerobic test, at 3 time points during 1 training year (Start/Y, Mid/Y, and End/Y). Fitness improved at the Mid/Y and End/Y compared to Start/Y. Postural balance significantly deteriorated immediately after the aerobic test and improved significantly in the 10-min testing in all 3 time points, with significant deterioration in the End/Y compared with the Start/Y. In conclusions, postural balance deteriorates immediately after aerobic exercises, and at the end of the year. To better practice drills related to postural balance and possibly to prevent injuries, it is best for young athletes to properly rest immediately following aerobic exercises and to practice postural balance mainly at the beginning and at the middle of the training year. PMID:26731202

  16. A Review of Spectral Methods for Variable Amplitude Fatigue Prediction and New Results

    NASA Technical Reports Server (NTRS)

    Larsen, Curtis E.; Irvine, Tom

    2013-01-01

    A comprehensive review of the available methods for estimating fatigue damage from variable amplitude loading is presented. The dependence of fatigue damage accumulation on power spectral density (psd) is investigated for random processes relevant to real structures such as in offshore or aerospace applications. Beginning with the Rayleigh (or narrow band) approximation, attempts at improved approximations or corrections to the Rayleigh approximation are examined by comparison to rainflow analysis of time histories simulated from psd functions representative of simple theoretical and real world applications. Spectral methods investigated include corrections by Wirsching and Light, Ortiz and Chen, the Dirlik formula, and the Single-Moment method, among other more recent proposed methods. Good agreement is obtained between the spectral methods and the time-domain rainflow identification for most cases, with some limitations. Guidelines are given for using the several spectral methods to increase confidence in the damage estimate.

  17. High-Temperature, Low-Cycle Fatigue of Copper-Base Alloys for Rocket Nozzles. Part 1: Data Summary for Materials Tested in Prior Programs

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1975-01-01

    A more detailed analysis of the results obtained in 188 previously reported low-cycle fatigue tests of various candidate materials for regeneratively-cooled, reusable rocket nozzle liners was reported. Plots of load range versus cycles were reported for each test along with a stress-strain hysteresis loop near half-life. In addition, a summary table was provided to compare N5 (cycles to a five percent load range drop) and Nf (cycles to complete specimen separation) values for each test.

  18. Altitude Compensating Nozzle Cold Flow Test Results

    NASA Technical Reports Server (NTRS)

    Ruf, J. H.; McDaniels, D. M.

    2002-01-01

    A suite of four altitude compensating nozzle (ACN) concepts were evaluated by NASA MSFC in the Nozzle Test Facility. The ACN concepts were a dual bell, a dual expander, an annular plug nozzle and an expansion deflection nozzle. Two reference bell nozzles were also tested. Axial thrust and nozzle wall static pressures were measured for each nozzle over a wide range of nozzle pressure ratios. The nozzle hardware and test program are described. Sample test results are presented.

  19. Reproducibility of liquid oxygen impact test results

    NASA Technical Reports Server (NTRS)

    Gayle, J. B.

    1975-01-01

    Results for 12,000 impacts on a wide range of materials were studied to determine the reproducibility of the liquid oxygen impact test method. Standard deviations representing the overall variability of results were in close agreement with the expected values for a binomial process. This indicates that the major source of variability is due to the go - no go nature of the test method and that variations due to sampling and testing operations were not significant.

  20. Creep-fatigue of low cobalt superalloys

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1982-01-01

    Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.

  1. Using Test Results To Support Clinical Judgment.

    ERIC Educational Resources Information Center

    Silverman, Linda Kreger

    This paper recommends an evaluation procedure for gifted children which uses test results only to confirm the conclusions resulting from clinical evaluation that involves observation, discussion with the child, an interview with the parents, developmental milestones, and family history. It suggests that traditional test interpretation may lead to…

  2. Results of steel containment vessel model test

    SciTech Connect

    Luk, V.K.; Ludwigsen, J.S.; Hessheimer, M.F.; Komine, Kuniaki; Matsumoto, Tomoyuki; Costello, J.F.

    1998-05-01

    A series of static overpressurization tests of scale models of nuclear containment structures is being conducted by Sandia National Laboratories for the Nuclear Power Engineering Corporation of Japan and the US Nuclear Regulatory Commission. Two tests are being conducted: (1) a test of a model of a steel containment vessel (SCV) and (2) a test of a model of a prestressed concrete containment vessel (PCCV). This paper summarizes the conduct of the high pressure pneumatic test of the SCV model and the results of that test. Results of this test are summarized and are compared with pretest predictions performed by the sponsoring organizations and others who participated in a blind pretest prediction effort. Questions raised by this comparison are identified and plans for posttest analysis are discussed.

  3. Fatigue of concrete beams and slabs

    NASA Astrophysics Data System (ADS)

    Roesler, Jeffrey Raphael

    Traditionally, simply supported concrete beam (SSB) fatigue results have been used to characterize the fatigue resistance of fully supported concrete slabs (FSS). SSB concrete fatigue tests have been assumed to be equivalent to the fatigue resistance of concrete slabs in the field. The effect specimen size, boundary conditions, and loading configurations have on the fatigue of concrete beams and slabs have not been considered in the design of concrete pavements against fatigue. A laboratory study was undertaken to determine if the fatigue behavior of FSS and SSB were similar. A fully supported beam (FSB) was also tested under repeated loading, since it represented an intermediate specimen size and testing configuration between SSB and FSS. The best way to present fatigue results for all specimens was a stress ratio (S) to number of cycles to failure (N) curve (S-N curve). SSB fatigue behavior was similar to results obtained from the literature. FSB had similar fatigue behavior to SSB. The fatigue curve derived from repeated loading of FSS was 30 percent higher than the SSB fatigue curve. This suggested for a given number of cycles to failure, FSS could take a 30 percent higher bending stress as compared to SSB and FSB. The concrete modulus of rupture from a FSS test configuration was 30 percent greater than the concrete modulus of rupture from a SSB test setup. If the concrete modulus of rupture from a FSS test configuration was used in the slab's stress ratio, the slab's fatigue curve was the same as the SSB and FSB. This meant concrete behaved the same under fatigue loading, irrespective of specimen size and test configuration, as long as the correct concrete modulus of rupture was used in the stress ratio. Strain gages, attached to all specimens tested, indicated cracking in concrete occurred in a narrow band. Regions of high plastic strain were found in the plane of cracking, while adjacent areas experienced decreases in strain levels with cracking. Strain

  4. Superconducting solenoid model magnet test results

    SciTech Connect

    Carcagno, R.; Dimarco, J.; Feher, S.; Ginsburg, C.M.; Hess, C.; Kashikhin, V.V.; Orris, D.F.; Pischalnikov, Y.; Sylvester, C.; Tartaglia, M.A.; Terechkine, I.; /Fermilab

    2006-08-01

    Superconducting solenoid magnets suitable for the room temperature front end of the Fermilab High Intensity Neutrino Source (formerly known as Proton Driver), an 8 GeV superconducting H- linac, have been designed and fabricated at Fermilab, and tested in the Fermilab Magnet Test Facility. We report here results of studies on the first model magnets in this program, including the mechanical properties during fabrication and testing in liquid helium at 4.2 K, quench performance, and magnetic field measurements. We also describe new test facility systems and instrumentation that have been developed to accomplish these tests.

  5. Galileo spacecraft system level environmental test results

    NASA Technical Reports Server (NTRS)

    Hoffman, A. R.; Schlue, J. W.

    1986-01-01

    Project Galileo, the United States' next planetary mission, will be launched by the Shuttle/Centaur in May 1986. The Galileo spacecraft consists of both a planetary Orbiter and an atmospheric Probe. The spacecraft was environmentally tested as a system in the fall and winter of 1984/1985 at the Jet Propulsion Laboratory. The protoflight qualification program consisted of vibration, acoustics, pyrotechnic shock, Electromagnetic Compatibility (EMC) and Solar Thermal Vacuum (STV) tests. This test program was accomplished on a large, complex, dual-spin spacecraft without the benefit of precursor spacecraft prototype tests. This paper discusses the objectives of these tests and the implementation, and summarizes the results.

  6. The Zond 550 kW Z-40 wind turbine development status and test results

    SciTech Connect

    Mikhail, A.S.; Christenson, C.L.

    1995-09-01

    Zond Systems, Inc. initiated the development of the 500 kW Z-40 wind turbine in March 1993. After an accelerated 21 month development effort, an aileron controlled prototype was fabricated and subjected to an extensive series of tests. This prototype uses a unique partial span aileron system developed by Zond for regulation of power and control of rotor rpm. During development testing, the prototype was thoroughly evaluated. The testing of the Z-40 prototype has included power curve verification, evaluation of aileron performance, assessment of power quality, measurement of structural loads, and assessment of turbine noise emission. Turbine component testing includes blade fatigue, aileron and aileron linkage fatigue, a measurement of blade modal properties, static blade testing, and gearbox fatigue testing. This paper gives an update on the progress of the Z-40 development effort at Zond, a review of important test results, a comparison of measured performance vs predicted values, and the current status of the Z-40 production. Plans for the next generation of Zond wind turbines, incorporating increased rotor diameters and advanced design features, are also presented.

  7. Alternative filtration testing program: Pre-evaluation of test results

    SciTech Connect

    Georgeton, G.K.; Poirier, M.R.

    1990-09-28

    Based on results of testing eight solids removal technologies and one pretreatment option, it is recommended that a centrifugal ultrafilter and polymeric ultrafilter undergo further testing as possible alternatives to the Norton Ceramic filters. Deep bed filtration should be considered as a third alternative, if a backwashable cartridge filter is shown to be inefficient in separate testing.

  8. BWR Full Integral Simulation Test (FIST). Phase I test results

    SciTech Connect

    Hwang, W S; Alamgir, M; Sutherland, W A

    1984-09-01

    A new full height BWR system simulator has been built under the Full-Integral-Simulation-Test (FIST) program to investigate the system responses to various transients. The test program consists of two test phases. This report provides a summary, discussions, highlights and conclusions of the FIST Phase I tests. Eight matrix tests were conducted in the FIST Phase I. These tests have investigated the large break, small break and steamline break LOCA's, as well as natural circulation and power transients. Results and governing phenomena of each test have been evaluated and discussed in detail in this report. One of the FIST program objectives is to assess the TRAC code by comparisons with test data. Two pretest predictions made with TRACB02 are presented and compared with test data in this report.

  9. Different Aspects of Fatigue Experienced by Patients Receiving Maintenance Dialysis in Hemodialysis Units

    PubMed Central

    Biniaz, Vajihe; Tayybi, Ali; Nemati, Eghlim; Sadeghi Shermeh, Mehdi; Ebadi, Abbas

    2013-01-01

    Background Fatigue, a common symptom reported by patients receiving dialysis, is a multidimensional and subjective experience which is readily understood by individuals but difficult to measure. Objectives This study was performed to identify the prevalence of differential aspects of fatigue among patients receiving maintenance dialysis. Patients and Methods The cross-sectional study was conducted in two hemodialysis wards in Tehran with a sample of 163 participants. In this study, the multidimensional fatigue inventory was used to determine the level of fatigue. Demographic data were also collected with self-report survey. To analyze data with SPSS statistical software, test Chi square, T-test, and ANOVA were used. P- Value less than 0.05 was considered significant. Results All the patients experienced degrees of fatigue and 50 (30.7%) of the participants experienced a high level of fatigue. Fatigue scores arrangement was founded for physical fatigue followed by reduced activity and general fatigue. Lower levels of fatigue were reported for mental fatigue and reduced motivation. There was no diversity in this study in the levels of fatigue in respects of gender and marital status and employment status. Participants with diabetic nephropathy were the most fatigued. Conclusions People with chronic kidney disease regardless of their age, gender, state of health, and duration of hemodialysis experience high levels of fatigue; it is particularly important for health providers to understand this level of fatigue which affects the daily life of patients. PMID:24350089

  10. Salmonella mutagenicity test results for 250 chemicals

    SciTech Connect

    Haworth, S.; Lawlor, T.; Mortelmans, K.; Speck, W.; Zeiger, E.

    1983-01-01

    This publication is a presentation of Salmonella testing results on 250 coded chemicals, encompassing 370 tests. The majority of these results were previously summarized in issues of the National Toxicology Program Technical Bulletin. However, some interpretations were changed since publication in the NTP Bulletin, based upon a reevaluation of the data. The presentation here is designed both to summarize the results in the text and to present the data so that the reader has the opportunity of performing an independent evaluation of the data. The chemicals tested, their source, and purity (where known) are listed and their structures are given in Appendix 1.

  11. Preliminary Silver-hydrogen Cell Test Results

    NASA Technical Reports Server (NTRS)

    Lurie, C.

    1984-01-01

    Silver-hydrogen cells were tested. The objective of the test was to estimate useful life by operation at accelerated, simulated geosynchronous orbit conditions. Ten simulated seasons were run and are summarized. The results to-date reflect stable, trouble-free performance and indicate that the silver-hydrogen couple shows promise as a lightweight alternative to the nickel systems.

  12. High temperature fatigue behavior of Haynes 188

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Saltsman, James F.; Kalluri, Sreeramesh

    1988-01-01

    The high temperature, creep-fatigue behavior of Haynes 188 was investigated as an element in a broader thermomechanical fatigue life prediction model development program at the NASA-Lewis. The models are still in the development stage, but the data that were generated possess intrinsic value on their own. Results generated to date is reported. Data were generated to characterize isothermal low cycle fatigue resistance at temperatures of 316, 704, and 927 C with cyclic failure lives ranging from 10 to more than 20,000. These results follow trends that would be predicted from a knowledge of tensile properties, i.e., as the tensile ductility varies with temperature, so varies the cyclic inelastic straining capacity. Likewise, as the tensile strength decreases, so does the high cyclic fatigue resistance. A few two-minute hold-time cycles at peak compressive strain were included in tests at 760 C. These results were obtained in support of a redesign effort for the Orbital Maneuverable System engine. No detrimental effects on cyclic life were noted despite the added exposure time for creep and oxidation. Finally, a series of simulated thermal fatigue tests, referred to as bithermal fatigue tests, were conducted using 316 C as the minimum and 760 C as the maximum temperature. Only out-of-phase bithermal tests were conducted to date. These test results are intended for use as input to a more general thermomechanical fatigue life prediction model based on the concepts of the total strain version of Strainrange Partitioning.

  13. Module Hipot and ground continuity test results

    NASA Technical Reports Server (NTRS)

    Griffith, J. S.

    1984-01-01

    Hipot (high voltage potential) and module frame continuity tests of solar energy conversion modules intended for deployment into large arrays are discussed. The purpose of the tests is to reveal potentially hazardous voltage conditions in installed modules, and leakage currents that may result in loss of power or cause ground fault system problems, i.e., current leakage potential and leakage voltage distribution. The tests show a combined failure rate of 36% (69% when environmental testing is included). These failure rates are believed easily corrected by greater care in fabrication.

  14. Results of the HESSI Test Mishap Investigation

    NASA Technical Reports Server (NTRS)

    Worth, Daniel B.; Phillips, Rodney N.; Kross, Dennis A. (Technical Monitor)

    2000-01-01

    On March 21, 2000, the High-Energy Solar Spectroscopic Imager (HESSI) spacecraft was subjected to a series of vibration tests at the Jet Propulsion Laboratory (JPL) as a part of its flight certification program. The structural qualification test, denoted as the sineburst test, subjected the spacecraft to a major overtest that resulted in significant structural damage to the spacecraft. The HESSI Test Mishap Investigation Board (MIB) was formed on March 24, 2000, in response to a NASA headquarters request. Board membership included experts from NASA and the University of California at Berkeley. This paper will present the investigation methods, findings, and lessons learned from the HESSI mishap.

  15. Recent Radiation Test Results for Power MOSFETs

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie; Topper, Alyson D.; Casey, Megan C.; Wilcox, Edward P.; Phan, Anthony M.; Kim, Hak S.; LaBel, Kenneth A.

    2013-01-01

    Single-event effect (SEE) and total ionizing dose (TID) test results are presented for various hardened and commercial power metal-oxide-semiconductor field effect transistors (MOSFETs), including vertical planar, trench, superjunction, and lateral process designs.

  16. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  17. Low Emissions RQL Flametube Combustor Test Results

    NASA Technical Reports Server (NTRS)

    Chang, Clarence T.; Holdeman, James D.

    2001-01-01

    The overall objective of this test program was to demonstrate and evaluate the capability of the Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept for HSR applications. This test program was in support of the Pratt & Whitney and GE Aircraft Engines HSR low-NOx Combustor Program. Collaborative programs with Parker Hannifin Corporation and Textron Fuel Systems resulted in the development and testing of the high-flow low-NOx rich-burn zone fuel-to-air ratio research fuel nozzles used in this test program. Based on the results obtained in this test program, several conclusions can be made: (1) The RQL tests gave low NOx and CO emissions results at conditions corresponding to HSR cruise. (2) The Textron fuel nozzle design with optimal multiple partitioning of fuel and air circuits shows potential of providing an acceptable uniform local fuel-rich region in the rich burner. (3) For the parameters studied in this test series, the tests have shown T3 is the dominant factor in the NOx formation for RQL combustors. As T3 increases from 600 to 1100 F, EI(NOx) increases approximately three fold. (4) Factors which appear to have secondary influence on NOx formation are P4, T4, infinity(sub rb), V(sub ref,ov). (5) Low smoke numbers were measured for infinity(sub rb) of 2.0 at P4 of 120 psia.

  18. Simplification of Fatigue Test Requirements for Damage Tolerance of Composite Interstage Launch Vehicle Hardware

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.; Hodge, A. J.; Jackson, J. R.

    2010-01-01

    The issue of fatigue loading of structures composed of composite materials is considered in a requirements document that is currently in place for manned launch vehicles. By taking into account the short life of these parts, coupled with design considerations, it is demonstrated that the necessary coupon level fatigue data collapse to a static case. Data from a literature review of past studies that examined compressive fatigue loading after impact and data generated from this experimental study are presented to support this finding. Damage growth, in the form of infrared thermography, was difficult to detect due to rapid degradation of compressive properties once damage growth initiated. Unrealistically high fatigue amplitudes were needed to fail 5 of 15 specimens before 10,000 cycles were reached. Since a typical vehicle structure, such as the Ares I interstage, only experiences a few cycles near limit load, it is concluded that static compression after impact (CAI) strength data will suffice for most launch vehicle structures.

  19. Punch valve development testing: Low and high velocity test results

    SciTech Connect

    Replogle, W.C.; Brandon, S.L.

    1996-09-01

    This is a report on the use of quasi-static tests to predict fundamental parameters for punch valve development. This report summarizes the results from low and high velocity tests performed with 0.63 and 0.38 cm diameter plungers, 5 cm long penetrating aluminium and composite targets. The low velocity tests, 0.025 m/s, were performed to understand the effects and interactions of plunger diameter plunger tip shape, target material, and target support on penetration energy and plunger functionality. High velocity tests, 75 m/s, were compared to low velocity results.

  20. A multi-station machine for the fatigue testing of denture base materials.

    PubMed

    Manley, T R; Stonebanks, J A

    1980-07-01

    A multi-station machine has been designed and built to determine the resistance to fatigue failure of denture base materials. The machine has enabled complete S-N curves to be plotted for conventional and reinforced denture base materials involving many megacycles of operation. The resistance to fatigue failure of conventional denture base polymers is similar to that of 'Perspex'; that of PMMA reinforced with carbon fibre is of an order of magnitude greater. PMID:7470562

  1. Adaptive structures - Test hardware and experimental results

    NASA Technical Reports Server (NTRS)

    Wada, Ben K.; Fanson, James L.; Chen, Gun-Shing; Kuo, Chin-Po

    1990-01-01

    The facilities and procedures used at JPL to test adaptive structures such as the large deployable reflector (LDR) are described and preliminary results are reported. The applications of adaptive structures in future NASA missions are outlined, and the techniques which are employed to modify damping, stiffness, and isolation characteristics, as well as geometric changes, are listed. The development of adaptive structures is shown to be effective as a result of new actuators and sensors, and examples are listed for categories such as fiber optics, shape-memory materials, piezoelectrics, and electrorheological fluids. Some ground test results are described for laboratory truss structures and truss test beds, which are shown to be efficient and easy to assemble in space. Adaptive structures are shown to be important for precision space structures such as the LDR, and can alleviate ground test requirements.

  2. CEBAF'S New RF Separator Structure Test Results

    SciTech Connect

    Reza Kazimi; Jock Fugitt; A. Krycuk; Charles Sinclair; Larry Turlington

    1993-05-01

    Prototypes of the rf separator for CEBAF have been made and successfully beam tested. The structure is a new design which has a high transverse shunt impedance together with a small transverse dimension compared to more conventional rf deflecting structures. Five rf separators will be used at CEBAF to allow beam from any one of the five recirculation passes to be delivered to any of the three experimental halls. The authors have already described the basic design of the structure and theoretical calculations. They have also reported some results from rf measurements and beam tests. In this paper they present more beam test results, their final design parameters, and test results of coupling two 1/2 wavelength cavities together.

  3. Investigation of fatigue failure in bituminous base mixes

    NASA Astrophysics Data System (ADS)

    Maupin, G. W., Jr.

    1980-02-01

    A correlation between the results obtained with the fatigue test and those from the indirect tensile test on two base mixes was attempted in anticipation of the possible use of the latter test to design base mixes for maximum fatigue life. Two base mixes at several asphalt contents were tested at two test temperatures. Flexural fatigue tests and indirect tensile tests were performed for each mix and temperature condition. The asphalt content corresponding to the maximum fatigue life agreed generally with the asphalt content corresponding to maximum work in the indirect tensile test. The work computed from the indirect tensile test is useful in selecting the asphalt content for the maximum fatigue life of base mixes.

  4. Women's interpretation of cervical smear test results.

    PubMed

    Philips, Z; Avis, M; Whynes, D K

    2004-06-01

    Screening for cervical cancer using the Papanicolaou smear test has been available in England since the 1960s, yet very little is known about how women interpret their test results. This questionnaire study required women to explain, in their own words, the meaning of normal and abnormal test results. It was discovered that the use of the word cell as a description of findings was extremely common, and that a proportion of subjects equated abnormal results with technical inadequacy. The frequency of circularity in the interpretations, i.e. interpreting 'normal' as 'not abnormal' and vice versa, was striking. Contrary to previous research, we find that, whilst many women interpret normal results as indicating the current absence of cancer, few appear to believe that future cancer is thereby definitively ruled out. By the same token, only a very small minority interpret abnormal results as definitive of cancer. PMID:15165270

  5. NEXT Single String Integration Test Results

    NASA Technical Reports Server (NTRS)

    Soulas, George C.; Patterson, Michael J.; Pinero, Luis; Herman, Daniel A.; Snyder, Steven John

    2010-01-01

    As a critical part of NASA's Evolutionary Xenon Thruster (NEXT) test validation process, a single string integration test was performed on the NEXT ion propulsion system. The objectives of this test were to verify that an integrated system of major NEXT ion propulsion system elements meets project requirements, to demonstrate that the integrated system is functional across the entire power processor and xenon propellant management system input ranges, and to demonstrate to potential users that the NEXT propulsion system is ready for transition to flight. Propulsion system elements included in this system integration test were an engineering model ion thruster, an engineering model propellant management system, an engineering model power processor unit, and a digital control interface unit simulator that acted as a test console. Project requirements that were verified during this system integration test included individual element requirements ; integrated system requirements, and fault handling. This paper will present the results of these tests, which include: integrated ion propulsion system demonstrations of performance, functionality and fault handling; a thruster re-performance acceptance test to establish baseline performance: a risk-reduction PMS-thruster integration test: and propellant management system calibration checks.

  6. Fatigue behavior and recommended design rules for an automotive composite

    SciTech Connect

    Corum, J.M.; Battiste, R.L.; Ruggles, M.B.

    1998-11-01

    Fatigue curves (stress vs cycles to failure) were generated under a variety of conditions (temperatures, fluid environments, mean stresses, block loadings) for a candidate automotive structural composite. The results were used to (1) develop observations regarding basic fatigue behavioral characteristics and (2) establish fatigue design rules. The composite was a structural reaction injection-molded polyurethane reinforced with continuous strand, swirl-mat E-glass fibers. Tensile fatigue tests on specimens from a single plaque at {minus}40 F, room temperature, and 250 F provided the basic behavioral characteristics. It was found that when stress was normalized by the at-temperature ultimate tensile strength, the fatigue curves at the three temperatures collapsed into a single master curve. An assessment of the individual stress-strain loops throughout each test showed a progressive loss in stiffness and an increase in permanent strain, both of which are indicative of increasing damage. Fatigue tests on specimens from several plaques were used to develop a design fatigue curve, which was established by using a reduction factor of 20 on average cycles to failure. This factor assures that the stiffness loss during the design life is no greater than 10 percent. Fatigue reduction factors were established to account for various fluids. Reversed stress fatigue tests allowed a mean stress rule to be validated, and block loading tests were used to demonstrate the adequacy of Miner`s rule for cumulative fatigue damage.

  7. Test Result Management in Global Health Settings

    PubMed Central

    Palazuelos, Daniel; Payne, Jonathan D.

    2012-01-01

    OVERVIEW Across the globe, the ways in which patients' test results are managed are as varied as the many different types of healthcare systems that manage these data. The outcomes, however, are often not too dissimilar: too many clinically significant test results fall through the cracks. The consequences of not following up test results in a timely manner are serious and often devastating to patients: diagnoses are delayed, treatments are not initiated or altered in time, and diseases progress. In resource-poor settings, test results too commonly get filed away within the paper chart in ways that isolate them and prevent passage to future providers caring for a patient. To make matters worse, the onus to act upon these test results often rests on patients who need to return to the clinic within a specified timeframe in order to obtain their results but who may not have the means or are too ill to do so. Even in more developed healthcare settings that use electronic records, clinical data residing in the electronic medical record (EMR) are often stubbornly “static”—key pieces of clinical information are frequently not recognized, retrieved, or shared easily. In this way, EMRs are not unlike paper record systems, and therefore, EMRs alone will not solve this problem. To illustrate this problem, consider the case of a patient newly diagnosed with HIV in 3 different healthcare delivery settings. PMID:24278831

  8. Anti-buckling fatigue test assembly. [for subjecting metal specimen to tensile and compressive loads at constant temperature

    NASA Technical Reports Server (NTRS)

    Eichenbrenner, F. F.; Imig, L. A. (Inventor)

    1974-01-01

    An antibuckling fatigue test assembly is described for holding a metal specimen which is subjected to compression and to rapid cyclical heating and cooling while permitting visual observation. In an illustrative embodiment of this invention, the anti-buckling fatigue test apparatus includes first and second guide members between which the metal specimen is disposed and held, a heating assembly comprising a suitable heating source such as a quartz lamp and a reflecting assembly directing the heat onto the specimen, and a cooling assembly for directing a suitable cooling fluid such as air onto the specimen. The guide members each have a passage to permit the heat to be directed onto the specimen. An opening is provided in the reflecting assembly to permit visual inspection of that region of the specimen adjacent to the opening onto which the heat is directed.

  9. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    NASA Astrophysics Data System (ADS)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  10. Results and Analysis from Space Suit Joint Torque Testing

    NASA Technical Reports Server (NTRS)

    Matty, Jennifer

    2010-01-01

    A space suit's mobility is critical to an astronaut's ability to perform work efficiently. As mobility increases, the astronaut can perform tasks for longer durations with less fatigue. Mobility can be broken down into two parts: range of motion (ROM) and torque. These two measurements describe how the suit moves and how much force it takes to move. Two methods were chosen to define mobility requirements for the Constellation Space Suit Element (CSSE). One method focuses on range of motion and the second method centers on joint torque. A joint torque test was conducted to determine a baseline for current advanced space suit joint torques. This test utilized the following space suits: Extravehicular Mobility Unit (EMU), Advanced Crew Escape Suit (ACES), I-Suit, D-Suit, Enhanced Mobility (EM)- ACES, and Mark III (MK-III). Data was collected data from 16 different joint movements of each suit. The results were then reviewed and CSSE joint torque requirement values were selected. The focus of this paper is to discuss trends observed during data analysis.

  11. Friction drive characterization breadboard: test results

    NASA Astrophysics Data System (ADS)

    Sedghi, B.; Lucuix, C.; Tortolani, J. M.; Brunetto, E.; Delrez, C.; Gabriel, E.

    2010-07-01

    The drive and bearing technologies have a major impact on the static and dynamic performance of steerable structures such as telescope and dome. Merging drive and bearing system into friction drive mechanical devices (bogie) can reduce the complexity and cost of the design. In the framework of ELT design study (European FP6) a breadboard test setup was realized to test and evaluate the static and dynamic behavior of such bogies. In this paper some of the characterization test results are presented. Characterization of the bogies and the setup structure in the frequency domain, quantification and measure of the most important parameters of the friction forces, the control of the bogies and the tracking performance of the test setup are among the main results discussed in this paper.

  12. Experimental investigation of fatigue behavior of carbon fiber composites using fully-reversed four-point bending test

    NASA Astrophysics Data System (ADS)

    Amiri, Ali

    Carbon fiber reinforced polymers (CFRP) have become an increasingly notable material for use in structural engineering applications. Some of their advantages include high strength-to-weight ratio, high stiffness-to-weight ratio, and good moldability. Prediction of the fatigue life of composite laminates has been the subject of various studies due to the cyclic loading experienced in many applications. Both theoretical studies and experimental tests have been performed to estimate the endurance limit and fatigue life of composite plates. One of the main methods to predict fatigue life is the four-point bending test. In most previous works, the tests have been done in one direction (load ratio, R, > 0). In the current work, we have designed and manufactured a special fixture to perform a fully reversed bending test (R = -1). Static four-point bending tests were carried out on three (0°/90°)15 and (± 45°)15 samples to measure the mechanical properties of CFRP. Testing was displacement-controlled at the rate of 10 mm/min until failure. In (0°/90°)15 samples, all failed by cracking/buckling on the compressive side of the sample. While in (± 45°)15 all three tests, no visual fracture or failure of the samples was observed. 3.4 times higher stresses were reached during four-point static bending test of (0° /90°)15 samples compared to (± 45°)15. Same trend was seen in literature for similar tests. Four-point bending fatigue tests were carried out on (0° /90°)15 sample with stress ratio, R = -1 and frequency of 5 Hz. Applied maximum stresses were approximately 45%, 56%, 67%, 72% and 76% of the measured yield stress for (0° /90°)15 samples. There was visible cracking through the thickness of the samples. The expected downward trend in fatigue life with increasing maximum applied stress was observed in S-N curves of samples. There appears to be a threshold for ‘infinite’ life, defined as 1.7 million cycles in the current work, at a maximum stress of about

  13. JPL pyro shock test approaches and results

    NASA Technical Reports Server (NTRS)

    Chang, Kurng Y.

    1986-01-01

    This paper presents the overall approach at JPL in performing spacecraft pyrotechnic shock qualification testing. Initially, the assembly shock requirements are developed early in the program based on previous spacecraft test experience and data. Pyrotechnic device development testing firings and spacecraft Development Test Model (DTM) pyro firings are then conducted to verify the adequacy of the assembly shock requirements and to determine the subsystem test firing and the subsequent system level test firing requirements. The electro-dynamic shaker, through shock synthesis techniques, is utilized to qualify the shock sensitive flight equipment with margins applied. Actual pyrotechnic device firings on spacecraft equipment or science instruments are performed when the influence of the pyros is localized and can be ignored at the system level. Full spacecraft system level shock tests, which include multiple firings of certain critical pyro devices, are conducted to verify the spacecraft design structural integrity and functions as well as to qualify hardware items which have not been previously qualified. These tests also provide a source of data from which assembly level requirements can be evaluated and compared. For example, during the Galileo program, the results demonstrated that good agreement between predicted and measured shock environments and adequate qualification of the flight spacecraft was achieved.

  14. Fatigue of continuous fiber reinforced titanium matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1991-01-01

    Several lay-ups of SCS-6/Ti-15-3 composites were investigated. Static and fatigue tests were conducted for both notched and unnotched specimens at room and elevated temperatures. Test results indicated that the stress in the 0 fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be dependent on the level of residual stresses and the fiber/ matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fiber spacings in the matrix material without breaking fibers. These matrix cracks can significantly reduce the residual strength of notched composite.

  15. Fatigue experience from tests carried out with forged beam and frame structures in the development of the Saab aircraft Viggen

    NASA Technical Reports Server (NTRS)

    Larsson, S. E.

    1972-01-01

    A part of the lower side of the main wing at the joint of the main spar with the fuselage frame was investigated. This wing beam area was simulated by a test specimen consisting of a spar boom of AZ 74 forging (7075 aluminum alloy modified with 0.3 percent Ag) and a portion of a honeycomb sandwich panel attached to the boom flange with steel bolts. The cross section was reduced to half scale. However, the flange thickness, the panel height, and the bolt size were full scale. Further, left and right portions of the fuselage frame intended to carry over the bending moment of the main wing were tested. Each of these frame halves consisted of a forward and a rear forging (7079 aluminum alloy, overaged) connected by an outer and inner skin (Alclad 7075) creating a box beam. These test specimens were full scale and were constructed principally of ordinary aircraft components. The test load spectrum was common to both types of specimens with regard to percentage levels. It consisted of maneuver and gust loads, touchdown loads, and loads due to ground roughness. A load history of 200 hours of flight with 15,000 load cycles was punched on a tape. The loads were randomized in groups according to the flight-by-flight principle. The highest positive load level was 90 percent of limit load and the largest negative load was -27 percent. A total of 20 load levels were used. Both types of specimens were provided with strain gages and had a nominal stress of about 300 MN/sq m in some local areas. As a result of the tests, steps were taken to reduce the risk of fatigue damage in aircraft. Thus stress levels were lowered, radii were increased, and demands on surface finish were sharpened.

  16. Fatigue strength of adhesive bonded section beams under torsion

    SciTech Connect

    Tomioka, Noboru; Kakiage, Masashi; Niisawa, Junetsu; Kitagawa, Hideo

    1995-11-01

    Fatigue strength of adhesive bonded box beams was investigated. From results of the fatigue tests, it was seen that the fatigue strength of bonded beams was higher than that of spot welded beams. Fatigue strength of bonded beams was independent of plate thickness and partition. The flexural rigidity of the box beams in the plane of partition can increase without decrease of torsional rigidity and torsional fatigue strength, if the partition is jointed by adhesive bonding instead of spot welding. Since the fatigue strength and rigidity of adhesive bonded joints can be higher than the spot welded joints in the weight saving structures, it is expected that the structural adhesive joints will be employed more in the automobile body structure. For assuring the introduction of this joint more into the automobile body structures, it is necessary that the fatigue tests on the model members of the actual members used in the automobile body structure are conducted, in addition to those of the simple joints such as tension shear and T-type tension, and the property of the fatigue strength on the adhesive bonded members is known. But, the authors now have little data on fatigue tests of the adhesive bonded members. In the present research to be reported, the fatigue tests on adhesive bonded box beams under torsion, which are typical members in automobile body structure, were carried out and the effects of the presence of longitudinal partition and plate thickness on fatigue strength were investigated. Comparing the results of fatigue tests on adhesive bonded box beams with those on spot welded box beams, the property of fatigue strength on these adhesive bonded box beams was cleared.

  17. Cascade Distiller System Performance Testing Interim Results

    NASA Technical Reports Server (NTRS)

    Callahan, Michael R.; Pensinger, Stuart; Sargusingh, Miriam J.

    2014-01-01

    The Cascade Distillation System (CDS) is a rotary distillation system with potential for greater reliability and lower energy costs than existing distillation systems. Based upon the results of the 2009 distillation comparison test (DCT) and recommendations of the expert panel, the Advanced Exploration Systems (AES) Water Recovery Project (WRP) project advanced the technology by increasing reliability of the system through redesign of bearing assemblies and improved rotor dynamics. In addition, the project improved the CDS power efficiency by optimizing the thermoelectric heat pump (TeHP) and heat exchanger design. Testing at the NASA-JSC Advanced Exploration System Water Laboratory (AES Water Lab) using a prototype Cascade Distillation Subsystem (CDS) wastewater processor (Honeywell d International, Torrance, Calif.) with test support equipment and control system developed by Johnson Space Center was performed to evaluate performance of the system with the upgrades as compared to previous system performance. The system was challenged with Solution 1 from the NASA Exploration Life Support (ELS) distillation comparison testing performed in 2009. Solution 1 consisted of a mixed stream containing human-generated urine and humidity condensate. A secondary objective of this testing is to evaluate the performance of the CDS as compared to the state of the art Distillation Assembly (DA) used in the ISS Urine Processor Assembly (UPA). This was done by challenging the system with ISS analog waste streams. This paper details the results of the AES WRP CDS performance testing.

  18. Fatigue reliability based optimal design of planar compliant micropositioning stages

    NASA Astrophysics Data System (ADS)

    Wang, Qiliang; Zhang, Xianmin

    2015-10-01

    Conventional compliant micropositioning stages are usually developed based on static strength and deterministic methods, which may lead to either unsafe or excessive designs. This paper presents a fatigue reliability analysis and optimal design of a three-degree-of-freedom (3 DOF) flexure-based micropositioning stage. Kinematic, modal, static, and fatigue stress modelling of the stage were conducted using the finite element method. The maximum equivalent fatigue stress in the hinges was derived using sequential quadratic programming. The fatigue strength of the hinges was obtained by considering various influencing factors. On this basis, the fatigue reliability of the hinges was analysed using the stress-strength interference method. Fatigue-reliability-based optimal design of the stage was then conducted using the genetic algorithm and MATLAB. To make fatigue life testing easier, a 1 DOF stage was then optimized and manufactured. Experimental results demonstrate the validity of the approach.

  19. Fracture toughness results and preliminary analysis for International Cooperative Test Program on specimens containing surface cracks

    SciTech Connect

    Reuter, W.G.; Elfer, N.C.; Hull, D.A.; Newman, J.C. Jr.; Munz, D.; Panontin, T.L.

    1997-12-31

    Specimens containing surface cracks were tested in either tension or bending to compare the stress intensity factor at failure with plane strain fracture toughness (K{sub Ic}) in an International Cooperative Test Program. The material was heat treated to {sigma}{sub ys} = 1 587 MPa and K{sub Ic} = 54 MPa m{sub 1/2}. Because substantial stable crack growth occurred for some specimens, the test plan was modified to include detecting the onset of crack growth. It is shown that P{sub max} and the original fatigue precrack size cannot be employed to calculate K{sub max} for comparison with K{sub Ic} when significant stable crack growth occurs. However, using P{sub init} (load at which stable crack growth is initiated) and the original fatigue precrack size to calculate K{sub max} or K{sub {phi}=30{degree}} provides a very useful comparison with K{sub Ic}. The influence of variations in fatigue precrack configuration on test results are also discussed.

  20. Ball Aerospace SBMD Coating Test Results

    NASA Technical Reports Server (NTRS)

    Brown, Robert; Lightsey, Paul; Russell, J. Kevin (Technical Monitor)

    2002-01-01

    The Sub-scale Beryllium Mirror Demonstrator that was successfully tested to demonstrate cryogenic figuring of a bare mirror has been coated with a protected gold reflective surface and retested at cryogenic temperatures. Results showing less than 9 nm rms surface distortion attributable to the added coating are presented.

  1. SLD liquid argon calorimeter prototype test results

    SciTech Connect

    Dubois, R.; Eigen, G.; Au, Y.; Sleeman, J.; Breidenbach, M.; Brau, J.; Ludgate, G.A.; Oram, C.J.; Cook, V.; Johnson, J.

    1985-10-01

    The results of the SLD test beam program for the selection of a calorimeter radiator composition within a liquid argon system are described, with emphasis on the study of the use of uranium to obtain equalization of pion and electron responses.

  2. Low cycle fatigue and creep-fatigue behavior of Ni-based alloy 230 at 850 C

    SciTech Connect

    Chen, Xiang; Yang, Zhiqing; Sokolov, Mikhail A; ERDMAN III, DONALD L; Mo, Kun; Stubbins, James

    2013-01-01

    Strain-controlled low cycle fatigue (LCF) and creep-fatigue testing of Ni-based alloy 230 were carried out at 850 C. The material creep-fatigue life decreased compared with its low cycle fatigue life at the same total strain range. Longer hold time at peak tensile strain further reduced the material creep-fatigue life. Based on the electron backscatter diffraction, a novel material deformation characterization method was applied, which revealed that in low cycle fatigue testing as the total strain range increased, the deformation was segregated to grain boundaries since the test temperature was higher than the material equicohesive temperature and grain boundaries became weaker regions compared with grains. Creep-fatigue tests enhanced the localized deformation, resulting in material interior intergranular cracking, and accelerated material damage. Precipitation in alloy 230 helped slip dispersion, favorable for fatigue property, but grain boundary cellular precipitates formed after material exposure to the elevated temperature had a deleterious effect on the material low cycle fatigue and creep-fatigue property.

  3. Cardiac mechanics are impaired during fatiguing exercise and cold pressor test in healthy older adults

    PubMed Central

    Muller, Matthew D.; Mast, Jessica L.; Patel, Hardikkumar

    2013-01-01

    We sought to determine how the aging left ventricle (LV) responds to sympathetic nervous system (SNS) activation. Three separate echocardiographic experiments were conducted in 11 healthy young (26 ± 1 yr) and 11 healthy older (64 ± 1 yr) adults. Tissue Doppler imaging was used to measure systolic myocardial velocity (Sm), early diastolic myocardial velocity (Em), and late diastolic myocardial velocity (Am) during isometric fatiguing handgrip (IFHG), a 2-min cold pressor test (CPT), and 5 min of normobaric hypoxia. Heart rate (HR) and mean arterial pressure (MAP) were also monitored on a beat-by-beat basis; rate pressure product (RPP) was used as an index of myocardial oxygen demand. At peak IFHG, the groups had similar increases in RPP, but the ΔSm was significantly greater (i.e., larger impairment) in the older subjects (−0.82 ± 0.13 cm/s) compared with the young subjects (0.37 ± 0.30 cm/s). At peak IFHG, the ΔEm was similar between older (−1.59 ± 0.68 cm/s) and young subjects (−1.06 ± 0.76 cm/s). In response to the CPT, both Sm and Em were reduced in the older adults but did not change relative to baseline in the young subjects. Normobaric hypoxia elevated HR and RPP in both groups but did not alter Tissue Doppler parameters. These data indicate that Sm and Em are reduced in healthy older adults during IFHG and CPT. We speculate that suboptimal LV adaptations to SNS stress may partly explain why acute heavy exertion can trigger myocardial ischemia. PMID:23154996

  4. A modified PMMA cement (Sub-cement) for accelerated fatigue testing of cemented implant constructs using cadaveric bone.

    PubMed

    Race, Amos; Miller, Mark A; Mann, Kenneth A

    2008-10-20

    Pre-clinical screening of cemented implant systems could be improved by modeling the longer-term response of the implant/cement/bone construct to cyclic loading. We formulated bone cement with degraded fatigue fracture properties (Sub-cement) such that long-term fatigue could be simulated in short-term cadaver tests. Sub-cement was made by adding a chain-transfer agent to standard polymethylmethacrylate (PMMA) cement. This reduced the molecular weight of the inter-bead matrix without changing reaction-rate or handling characteristics. Static mechanical properties were approximately equivalent to normal cement. Over a physiologically reasonable range of stress-intensity factor, fatigue crack propagation rates for Sub-cement were higher by a factor of 25+/-19. When tested in a simplified 2 1/2-D physical model of a stem-cement-bone system, crack growth from the stem was accelerated by a factor of 100. Sub-cement accelerated both crack initiation and growth rate. Sub-cement is now being evaluated in full stem/cement/femur models. PMID:18774136

  5. Accurate diagnosis of myalgic encephalomyelitis and chronic fatigue syndrome based upon objective test methods for characteristic symptoms

    PubMed Central

    Twisk, Frank NM

    2015-01-01

    Although myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS) are considered to be synonymous, the definitional criteria for ME and CFS define two distinct, partially overlapping, clinical entities. ME, whether defined by the original criteria or by the recently proposed criteria, is not equivalent to CFS, let alone a severe variant of incapacitating chronic fatigue. Distinctive features of ME are: muscle weakness and easy muscle fatigability, cognitive impairment, circulatory deficits, a marked variability of the symptoms in presence and severity, but above all, post-exertional “malaise”: a (delayed) prolonged aggravation of symptoms after a minor exertion. In contrast, CFS is primarily defined by (unexplained) chronic fatigue, which should be accompanied by four out of a list of 8 symptoms, e.g., headaches. Due to the subjective nature of several symptoms of ME and CFS, researchers and clinicians have questioned the physiological origin of these symptoms and qualified ME and CFS as functional somatic syndromes. However, various characteristic symptoms, e.g., post-exertional “malaise” and muscle weakness, can be assessed objectively using well-accepted methods, e.g., cardiopulmonary exercise tests and cognitive tests. The objective measures acquired by these methods should be used to accurately diagnose patients, to evaluate the severity and impact of the illness objectively and to assess the positive and negative effects of proposed therapies impartially. PMID:26140274

  6. Accurate diagnosis of myalgic encephalomyelitis and chronic fatigue syndrome based upon objective test methods for characteristic symptoms.

    PubMed

    Twisk, Frank Nm

    2015-06-26

    Although myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS) are considered to be synonymous, the definitional criteria for ME and CFS define two distinct, partially overlapping, clinical entities. ME, whether defined by the original criteria or by the recently proposed criteria, is not equivalent to CFS, let alone a severe variant of incapacitating chronic fatigue. Distinctive features of ME are: muscle weakness and easy muscle fatigability, cognitive impairment, circulatory deficits, a marked variability of the symptoms in presence and severity, but above all, post-exertional "malaise": a (delayed) prolonged aggravation of symptoms after a minor exertion. In contrast, CFS is primarily defined by (unexplained) chronic fatigue, which should be accompanied by four out of a list of 8 symptoms, e.g., headaches. Due to the subjective nature of several symptoms of ME and CFS, researchers and clinicians have questioned the physiological origin of these symptoms and qualified ME and CFS as functional somatic syndromes. However, various characteristic symptoms, e.g., post-exertional "malaise" and muscle weakness, can be assessed objectively using well-accepted methods, e.g., cardiopulmonary exercise tests and cognitive tests. The objective measures acquired by these methods should be used to accurately diagnose patients, to evaluate the severity and impact of the illness objectively and to assess the positive and negative effects of proposed therapies impartially. PMID:26140274

  7. Comparing diagnostic tests: trials in people with discordant test results.

    PubMed

    Hooper, R; Díaz-Ordaz, K; Takeda, A; Khan, K

    2013-06-30

    Diagnostic tests are traditionally compared for accuracy against a gold standard but can also be compared prospectively in a trial. A conventional trial comparing two tests would randomize each participant to a testing strategy, but a more efficient alternative is to give both tests to all participants and follow up those with discordant results. Participants could be randomized before or after testing. The statistical analysis of such a trial has not previously been described. We investigated two estimates of the risk difference for a binary outcome: one based on analysing outcomes as if from a conventional trial and one combining estimates of different parameters in the manner of a decision analysis. We show that the trial estimate and decision analysis estimate are both unbiased and derive approximate formulae for their standard errors. By using the decision analysis estimate (but not the trial estimate), the same precision can be achieved by randomizing before testing as by randomizing after. To avoid destroying equipoise, and to allow consenting and randomizing to be carried out at the same visit, we recommend randomizing before testing. Giving both tests to all participants means fewer need to be recruited: in one example from the literature, the proposed design was nearly four times more efficient in this sense than a conventional trial design. PMID:23172716

  8. Dynamic response and acoustic fatigue of stiffened composite structure

    NASA Technical Reports Server (NTRS)

    Soovere, J.

    1984-01-01

    The results of acoustic fatigue and dynamic response tests performed on L-1011 graphite-epoxy (GrE) aileron and panel components are reported. The aileron featured glass microballoons between the GrE skins. Tests yielded random fatigue data from double and single cantilever coupons and modal data from impedance hammer and loudspeaker impulses. Numerical and sample test data were obtained on combined acoustic and shear loads, acoustic and thermal loads, random fatigue and damping of the integrally stiffened and secondary bonded panels. The fatigue data indicate a fatigue life beyond 10 million cycles. The acoustic data suggested that noise transmission could be enhanced in the integrally stiffened panels, which were more acoustic-fatigue resistant than were the secondary bonded panels.

  9. Implementation of a Two-Axis Servo-Hydraulic System for Full-Scale Fatigue Testing of Wind Turbine Blades

    SciTech Connect

    Hughes, S. D.; Musial, W. D.; Stensland, T.

    1999-09-09

    Recently, the blade fatigue testing capabilities at NREL were upgraded from single-axis to two-axis loading. To implement this, several practical challenges were addressed, as hardware complexity increased dramatically with two actuators applying the loads at right angles to each other. A custom bellcrank was designed and implemented to minimize the load angle errors and to prevent actuator side loading. The control system was upgraded to accept load and displacement feedback from two actuators. The inherent long strokes uniquely associated with wind turbine blade-tests required substantial real-time corrections for both the control and data systems. A custom data acquisition and control system was developed using a National Instruments LabVIEW platform that interfaces with proprietary servo-hydraulic software developed by MTS Corporation. Before testing, the program is run under quasi-static (slow speed) conditions and iterates to determine the correct operational control parameters for the controller, taking into consideration geometry, test speed, and phase angle errors between the two actuators. Comparisons are made between single-axis and two-axis test loads using actual test load data and load uncertainties are qualitatively described. To date, two fatigue tests have been completed and another is currently ongoing using NREL's two-axis capability.

  10. Cognitive Interviewing in the Evaluation of Fatigue Items: Results from the Patient-Reported Outcomes Measurement Information System (PROMIS)

    PubMed Central

    Christodoulou, Christopher; Junghaenel, Doerte U.; DeWalt, Darren A.; Rothrock, Nan; Stone, Arthur A.

    2010-01-01

    Objectives Cognitive Interviewing (CI) is a technique increasingly used to obtain respondent feedback on potential items during questionnaire development. No standard guidelines exist by which to incorporate CI feedback in deciding to retain, revise, or eliminate potential items. We used CI in developing fatigue items for the National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) Roadmap initiative. Our aims were to describe the CI process, formally evaluate the utility of decisions made on the basis of CI, and offer suggestions for future research. Methods Participants were 22 patients with a diverse range of chronic health conditions. During CI, each participant provided feedback on a series of items. We then reviewed the CI data and decided whether to retain, revise, or eliminate each potential item. Following this, we developed or adopted three quantitative methods to compare retained versus eliminated items. Results Retained items raised fewer serious concerns, were less likely to be viewed as non-applicable, and were less likely to display problems with clarity or to make incorrect assumptions about respondents. Conclusions CI was useful in developing the PROMIS fatigue items and the methods used to judge CI for the present item set may be useful for future investigations. PMID:18850327

  11. MIT 12 Tesla Coil test results

    NASA Astrophysics Data System (ADS)

    Steeves, M. M.; Hoenig, M. O.

    1985-07-01

    Test results from the MIT 12 Tesla Coil experiment are presented. The coil was tested in the High Field Test Facility (HFTF) of the Lawrence Livermore National Laboratory in October 1984 and January 1985. The experiment measured the performance of an Internally Cooled, Cabled Superconductor (ICCS) of practical size, intended for use in magnetic fusion experiments. The MIT coil carried 15 kA at 11 T for 5 min with no sign of instability. A half turn length in a 10 T field was able to absorb a heat load in 4 msec of more than 200 mJ sub cm of cable volume while carrying a current of 12 kA. The MIT coil successfully met the performance requirements of the Department of Energy's 12 Tesla Coil Program.

  12. Current activities in standardization of high-temperature, low-cycle-fatigue testing techniques in the United States

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Ellis, J. Rodney; Swindeman, Robert W.

    1990-01-01

    The American Society for Testing and Materials (ASTM) standard E606-80 is the most often used recommended testing practice for low-cycle-fatigue (LCF) testing in the United States. The standard was first adopted in 1977 for LCF testing at room temperature and was modified in 1980 to include high-temperature testing practices. Current activity within ASTM is aimed at extending the E606-80 recommended practices to LCF under thermomechanical conditions, LCF in high-pressure hydrogen, and LCF in metal-matrix composite materials. Interlaboratory testing programs conducted to generate a technical base for modifying E606-80 for the aforementioned LCF test types are discussed.

  13. Does Fatigue Complaint Reflect Memory Impairment in Multiple Sclerosis?

    PubMed Central

    Jougleux-Vie, Caroline; Duhin, Emeline; Deken, Valerie; Outteryck, Olivier; Vermersch, Patrick; Zéphir, Hélène

    2014-01-01

    Background and Purpose. Fatigue and memory impairment are common symptoms in multiple sclerosis (MS) and both may interact with cognition. This can contribute to making a complaint misrepresentative of the objective disorder. We sought to determine whether fatigue complaint in MS reflects memory impairment and investigated whether patients' subjective fatigue is associated with memory complaint. Methods. Fifty MS patients complaining of fatigue underwent subjective assessment of fatigue and memory complaint measured using self-assessment scales. Cognitive functions were assessed using a battery of neuropsychological tests, including a test of verbal episodic memory, the selective reminding test (SRT). Correlations were studied between subjective fatigue, memory complaint, and performance in verbal episodic memory. Results. Depression score, psychotropic and/or antiepileptic drug use, Expanded Disability Status Scale (EDSS) score, and MS form were confounding factors. After adjusting for these confounding factors, neither fatigue complaint nor memory complaint was correlated with SRT performance. Subjective fatigue was significantly associated with memory complaint. Conclusion. Although complaint of fatigue in MS was correlated with memory complaint, subjective fatigue was not the expression of memory impairment. PMID:24724029

  14. Interconnect fatigue design for terrestrial photovoltaic modules

    NASA Technical Reports Server (NTRS)

    Mon, G. R.; Moore, D. M.; Ross, R. G., Jr.

    1982-01-01

    The results of comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable (1) the prediction of cumulative interconnect failures during the design life of an array field, and (2) the unambiguous--ie., quantitative--interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field.

  15. Interconnect fatigue design for terrestrial photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Mon, G. R.; Moore, D. M.; Ross, R. G., Jr.

    1982-03-01

    The results of comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable (1) the prediction of cumulative interconnect failures during the design life of an array field, and (2) the unambiguous--ie., quantitative--interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field.

  16. Experimental research activities in dynamic response and sonic fatigue of hypersonic vehicle structures at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.

    1993-01-01

    This paper presents an overview of experimental research activities being pursued at the NASA Langley Research Center for dynamic response and sonic fatigue of hypersonic vehicle structures. The capabilities of the principle test facility, the Thermal Acoustic Fatigue Apparatus, are first given. Results from recent dynamic response and sonic fatigue tests on candidate hypersonic vehicle structures are then presented.

  17. Mechanical properties testing and results for thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Cruse, T. A.; Johnsen, B. P.; Nagy, A.

    1997-03-01

    Mechanical test data for thermal barrier coatings, including modulus, static strength, and fatigue strength data, are reviewed in support of the development of durability models for heat engine applica-tions. The materials include 7 and 8 wt % yttria partially stabilized zirconia (PSZ) as well as a cermet ma-terial (PSZ +10 wt % NiCoCrAlY). Both air plasma sprayed and electron beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  18. Hot fire test results of subscale tubular combustion chambers

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Jankovsky, Robert S.; Pavli, Albert J.

    1992-01-01

    Advanced, subscale, tubular combustion chambers were built and test fired with hydrogen-oxygen propellants to assess the increase in fatigue life that can be obtained with this type of construction. Two chambers were tested: one ran for 637 cycles without failing, compared to a predicted life of 200 cycles for a comparable smooth-wall milled-channel liner configuration. The other chamber failed at 256 cycles, compared to a predicted life of 118 cycles for a comparable smooth-wall milled-channel liner configuration. Posttest metallographic analysis determined that the strain-relieving design (structural compliance) of the tubular configuration was the cause of this increase in life.

  19. The Total Work Measured During a High Intensity Isokinetic Fatigue Test Is Associated With Anaerobic Work Capacity

    PubMed Central

    Bosquet, Laurent; Gouadec, Kenan; Berryman, Nicolas; Duclos, Cyril; Gremeaux, Vincent; Croisier, Jean Louis

    2016-01-01

    The purpose of the study was to determine whether total work measured during a high intensity isokinetic fatigue test (TWFAT) could be considered as a valid measure of anaerobic work capacity (AWC), such as determined by total work measured during a Wingate Anaerobic Test (TWWAnT). Twenty well-trained cyclists performed 2 randomly ordered sessions involving a high intensity isokinetic fatigue test consisting in 30 reciprocal maximal concentric contractions of knee flexors and extensors at 180°·s-1, and a Wingate Anaerobic Test. We found that TWFAT of knee extensors was largely lower than TWWAnT (4151 ± 691 vs 22313 ± 2901 J, respectively, p < 0.05, Hedge’s g = 4.27). Both measures were highly associated (r = 0.83), and the 95% limits of agreement (LoA) represented 24.5% of TWWAnT. TWFAT of knee flexors (2151 ± 540 J) was largely lower than TWWAnT (p < 0.05, g = 9.52). By contrast, both measures were not associated (r = 0.09), and the 95% LoA represented 31.1% of TWWAnT. Combining TWFAT of knee flexors and knee extensors into a single measure (6302 ± 818 J) did not changed neither improved these observations. We still found a large difference with TWWAnT (p < 0.05, g = 5.26), a moderate association (r = 0.65) and 95% LoA representing 25.5% of TWWAnT. We concluded that TWFAT of knee extensors could be considered as a valid measure of AWC, since both measure were highly associated. However, the mean difference between both measures and their 95% LoA were too large to warrant interchangeability. Key points Total work performed during a high intensity isokinetic fatigue test can be considered as a valid measure of anaerobic work capacity (as determined by total work performance during a 30-s Wingate anaerobic test). The 95% limits of agreement are two large to allow a direct comparison between both measures. In other words, it is not possible to estimate the magnitude of performance improvement during a 30-s Wingate anaerobic test from that observed during a

  20. The Total Work Measured During a High Intensity Isokinetic Fatigue Test Is Associated With Anaerobic Work Capacity.

    PubMed

    Bosquet, Laurent; Gouadec, Kenan; Berryman, Nicolas; Duclos, Cyril; Gremeaux, Vincent; Croisier, Jean Louis

    2016-03-01

    The purpose of the study was to determine whether total work measured during a high intensity isokinetic fatigue test (TWFAT) could be considered as a valid measure of anaerobic work capacity (AWC), such as determined by total work measured during a Wingate Anaerobic Test (TWWAnT). Twenty well-trained cyclists performed 2 randomly ordered sessions involving a high intensity isokinetic fatigue test consisting in 30 reciprocal maximal concentric contractions of knee flexors and extensors at 180°·s(-1), and a Wingate Anaerobic Test. We found that TWFAT of knee extensors was largely lower than TWWAnT (4151 ± 691 vs 22313 ± 2901 J, respectively, p < 0.05, Hedge's g = 4.27). Both measures were highly associated (r = 0.83), and the 95% limits of agreement (LoA) represented 24.5% of TWWAnT. TWFAT of knee flexors (2151 ± 540 J) was largely lower than TWWAnT (p < 0.05, g = 9.52). By contrast, both measures were not associated (r = 0.09), and the 95% LoA represented 31.1% of TWWAnT. Combining TWFAT of knee flexors and knee extensors into a single measure (6302 ± 818 J) did not changed neither improved these observations. We still found a large difference with TWWAnT (p < 0.05, g = 5.26), a moderate association (r = 0.65) and 95% LoA representing 25.5% of TWWAnT. We concluded that TWFAT of knee extensors could be considered as a valid measure of AWC, since both measure were highly associated. However, the mean difference between both measures and their 95% LoA were too large to warrant interchangeability. Key pointsTotal work performed during a high intensity isokinetic fatigue test can be considered as a valid measure of anaerobic work capacity (as determined by total work performance during a 30-s Wingate anaerobic test).The 95% limits of agreement are two large to allow a direct comparison between both measures. In other words, it is not possible to estimate the magnitude of performance improvement during a 30-s Wingate anaerobic test from that observed during a high

  1. CLSM bleed water reduction test results

    SciTech Connect

    Langton, C.A.; Rajendran, N.

    1997-04-21

    Previous testing by BSRI/SRTC/Raytheon indicated that the CLSM specified for the Tank 20 closure generates about 6 gallons (23 liters) of bleed water per cubic yard of material (0.76 m3).1 This amount to about 10 percent of the total mixing water. HLWE requested that the CLSM mix be optimized to reduce bleed water while maintaining flow. Elimination of bleed water from the CLSM mix specified for High-Level Waste Tank Closure will result in waste minimization, time savings and cost savings. Over thirty mixes were formulated and evaluated at the on-site Raytheon Test Laboratory. Improved low bleed water CLSM mixes were identified. Results are documented in this report.

  2. Fatigue Strengths of Aircraft Materials: Axial-Load Fatigue Tests on Edge-Notched Sheet Specimens of 2024-T3 and 7075-T6 Aluminum Alloys and of SAE 4130 Steel with Notch Radii of 0.004 and 0.070 inch

    NASA Technical Reports Server (NTRS)

    Grover, H. J.; Hyler, W. S.; Jackson, L. R.

    1959-01-01

    The present report gives results of axial-load fatigue tests on notched specimens of three sheet materials: 2024-T3 and 7075-T6 aluminum alloys and normalized SAE 4130 steel. Two edge-notched specimens were designed and tested, each having a theoretical stress-concentration factor K(sub t) = 4.0. The radii of the notches were 0.004 and 0.070 inch. Tests of these specimens were run at two levels of nominal mean stress: 0 and 20,000 psi. Results of these studies extended information previously reported on tests of specimens with varying notch severity. They afford data on the variation of fatigue-strength reduction with notch radius and on the potential usefulness of Neuber's technical stress-concentration factor K(sub n).

  3. Results from the final focus test beam

    SciTech Connect

    Burke, D.L.; Final Focus Test Beam Collaboration

    1994-07-01

    first experimental results from the Final Focus Test Beam (FFTB) are given in this report. The FFTB has been constructed as a prototype for the final focus system of a future TeV-scale electron-positron linear collider. The vertical dimension of the 47 GeV electron beam form the SLAC linac has been reduced at the focal point of the FFTB by a demagnification of 320 to a beam height of approximately 70 nanometers.

  4. Identifying Clinically Meaningful Fatigue with the Fatigue Symptom Inventory

    PubMed Central

    Donovan, Kristine A.; Jacobsen, Paul B.; Small, Brent J.; Munster, Pamela N.; Andrykowski, Michael A.

    2008-01-01

    The Fatigue Symptom Inventory (FSI) has been used extensively to assess and measure fatigue in a number of clinical populations. The purpose of the present study was to further establish its utility by examining its operating characteristics and determining the optimal cutoff score for identifying clinically meaningful fatigue. The SF-36 Vitality scale, a measure widely used to identify individuals with significant fatigue-related disability, was used to determine the sensitivity and specificity of the FSI. Results indicate that a score of 3 or greater on those items assessing fatigue in the past week is the optimal cutoff score for identifying clinically meaningful fatigue. Individuals who scored at or above the cutoff also reported significantly greater fatigue interference, more days of fatigue on average, and fatigue a greater proportion of each day in the past week. Findings suggest that the FSI can be used to discriminate effectively between individuals with and without clinically meaningful fatigue. PMID:18495413

  5. Application of Self Nulling Eddy Current Probe Technique to the Detection of Fatigue Crack Initiation and Control of Test Procedures

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Nath, S.; Wincheski, B.; Fulton, J. P.

    1994-01-01

    A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles and the knowledge of the precise location of the crack tip at any given time. One technique currently available for measuring fatigue crack length is the Potential Drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another popular approach is to optically view the crack using a high magnification microscope, but this entails a person constantly monitoring it. The present proposed technique uses an automated scheme, in order to eliminate the need for a person to constantly monitor the experiment. Another technique under development elsewhere is to digitize an optical image of the test specimen surface and then apply a pattern recognition algorithm to locate the crack tip. A previous publication showed that the self nulling eddy current probe successfully tracked a simulated crack in an aluminum sample. This was the impetus to develop an online real time crack monitoring system. An automated system has been developed which includes a two axis scanner mounted on the tensile testing machine, the probe and its instrumentation and a personal computer (PC) to communicate and control all the parameters. The system software controls the testing parameters as well as monitoring the fatigue crack as it propagates. This paper will discuss the experimental setup in detail and demonstrate its capabilities. A three dimensional finite element model is utilized to model the magnetic field distribution due to the probe and how the probe voltage changes as it scans the crack. Experimental data of the probe for different samples under zero load, static load and high cycle fatigue load will be discussed. The final section summarizes the major accomplishments

  6. Axial and torsional fatigue behavior of a cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1991-01-01

    In order to develop elevated temperature multiaxial fatigue life prediction models for the wrought cobalt-base alloy, Haynes 188, a multiaxial fatigue data base is required. To satisfy this need, an elevated temperature experimental program on Haynes 188 consisting of axial, torsional, inphase and out of phase axial-torsional fatigue experiments was designed. Elevated temperature axial and torsional fatigue experiments were conducted under strain control on thin wall tubular specimens of Haynes 188 in air. Test results are given.

  7. 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.

  8. Aquifer test results, Green Swamp area, Florida

    USGS Publications Warehouse

    Tibbals, C.H.; Grubb, Hayes F.

    1982-01-01

    An aquifer test conducted in the Green Swamp area December 15-16 , 1975 was designed to stress the uppermost part of the Floridan aquifer so that the leakage characteristics of the overlying confining bed could be determined. A well tapping the upper part of the Floridan aquifer was pumped at a rate of about 1,040 gallons per minute for 35 hours; drawdown was measured in the Floridan aquifer and in two horizons in the confining bed. Analysis of the data indicates that the transmissivity of the uppper 160 feet of the Floridan is 13,000 square feet per day, the storage coefficient is about 0.0002.5, and the overlying confining bed leakance coefficient is about 0.02 to 0.025 per day. The vertical hydraulic diffusivity of the confining bed ranged from 610 square feet per day to 16,000 square feet per day. Results of the test indicate that, in the area of the test site, a Floridan aquifer well field would induce additional recharge to the Floridan. As a result of that increased recharge , water levels in the surficial aquifer would tend to stand lower, runoff from the area would tend to be less, and, perhaps, evapotranspiration would be less than normal.(USGS)

  9. Flight qualification test results for violet cells

    NASA Technical Reports Server (NTRS)

    Gaddy, E. M.

    1974-01-01

    The violet solar cell has been submitted to a flight qualification program. The tasks included in this program were: to define the violet cell's electrical output from -100 C to +100 C; to determine the violet cell's degradation under 2 MeV, 1 MeV and .3 MeV proton irradiation, under a high humidity environment and under ultraviolet light; to thermal cycle two similar modules of violet cells; to flight qualify a full size violet cell panel for the IMP-J flight; and to obtain a primary balloon-flown standard of the violet cell type. The results of these tests demonstrate that the violet cell is fully qualified for space flight use with no further development work. The tests show that the violet cell offers a power increase of at least twenty-one per cent over presently available commercial cells.

  10. Highly Loaded Composite Strut Test Results

    NASA Technical Reports Server (NTRS)

    Wu, K. C.; Jegley, Dawn C.; Barnard, Ansley; Phelps, James E.; McKeney, Martin J.

    2011-01-01

    Highly loaded composite struts from a proposed truss-based Altair lunar lander descent stage concept were selected for development under NASA's Advanced Composites Technology program. Predicted compressive member forces during launch and ascent of over -100,000 lbs were much greater than the tensile loads. Therefore, compressive failure modes, including structural stability, were primary design considerations. NASA's industry partner designed and built highly loaded struts that were delivered to NASA for testing. Their design, fabricated on a washout mandrel, had a uniform-diameter composite tube with composite tapered ends. Each tapered end contained a titanium end fitting with facing conical ramps that are overlaid and overwrapped with composite materials. The highly loaded struts were loaded in both tension and compression, with ultimate failure produced in compression. Results for the two struts tested are presented and discussed, along with measured deflections, strains and observed failure mechanisms.

  11. Energy dissipation in Exosat tanks: Test results

    NASA Astrophysics Data System (ADS)

    Marce, J. L.; Torres, L.; Assemat, D.; Michel, S.

    1981-03-01

    Results of tests performed with inertia ratio and filling ratio scanning on Ariane tanks are presented. The Exosat launch requires the use of a fourth stage (P 0.7). The Exosat + P 0.7 assembly is spin stabilized with a spin rate of 50 rpm during transfer orbit. The unstable assembly is fitted with an active nutation damping system. To size this, it is necessary to know the time constant of nutation build up essentially due to fuel motion in the propane tanks and the hydrazine tank of Exosat. The major source of dissipation is the hydrazine tank for which an hysteresis phenomenon on diaphragm position was observed; the worst time constants of nutation build up, deduced from tests are 2.5 mn before P 0.7 and 1.9 mn after P 0.7 firing, taking into account the appropriate safety factors.

  12. GENIE Flight Test Results and System Overview

    NASA Technical Reports Server (NTRS)

    Brady, Tye; Paschall, Stephen, II; Crain, Timothy P., II; Demars, Kyle; Bishop, Robert

    2011-01-01

    NASA has envisioned a suite of lander test vehicles that will be flown in Earth s atmosphere to incrementally demonstrate applicable lunar lander performance in the terrestrial environment. As each terrestrial rocket progresses in maturity, relevant space flight technology matures to a higher technology readiness level, preparing it for inclusion on a future lunar lander design.. NASA s "Project M" lunar mission concept flew its first terrestrial rocket, RR1, in June 2010 in Caddo Mills, Texas. The Draper Laboratory built GENIE (Guidance Embedded Navigator Integration Environment) successfully demonstrated accurate, real time, embedded performance of Project M navigation and guidance algorithms in a highly dynamic environment. The RR1 vehicle, built by Armadillo Aerospace, performed a successful 60 second free flight and gave the team great confidence in Project M s highly reliable and robust GNC system design and implementation. This paper provides an overview of the GENIE system and describes recent flight performance test results onboard the RR1 terrestrial rocket.

  13. Results from the STAR TPC system test

    SciTech Connect

    Betts, W.; Bieser, F.; Bossingham, R.

    1996-12-31

    A system test of various components of the Solenoidal Tracker at RHIC (STAR) detector, operating in concern, has recently come on-line. Communication between a major sub-detector, a sector of the Time Projection Chamber (TPC), and the trigger, data acquisition and slow controls systems has been established, enabling data from cosmic ray muons to be collected. First results from an analysis of the TPC data are presented. These include measurements of system noise, electronic parameters such as amplifier gains and pedestal values, and tracking resolution for cosmic ray muons and laser induced ionization tracks. A discussion on the experience gained in integrating the different components for the system test is also given.

  14. PHASE I SINGLE CELL ELECTROLYZER TEST RESULTS

    SciTech Connect

    Steimke, J; Timothy Steeper, T

    2008-08-05

    This document reports the results of Phase I Single Cell testing of an SO{sub 2}-Depolarized Water Electrolyzer. Testing was performed primarily during the first quarter of FY 2008 at the Savannah River National Laboratory (SRNL) using an electrolyzer cell designed and built at SRNL. Other facility hardware were also designed and built at SRNL. This test further advances this technology for which work began at SRNL in 2005. This research is valuable in achieving the ultimate goal of an economical hydrogen production process based on the Hybrid Sulfur (HyS) Cycle. The focus of this work was to conduct single cell electrolyzer tests to further develop the technology of SO{sub 2}-depolarized electrolysis as part of the HyS Cycle. The HyS Cycle is a hybrid thermochemical cycle that may be used in conjunction with advanced nuclear reactors or centralized solar receivers to produce hydrogen by water-splitting. Like all other sulfur-based cycles, HyS utilizes the high temperature thermal decomposition of sulfuric acid to produce oxygen and regenerate sulfur dioxide. The unique aspect of HyS is the generation of hydrogen in a water electrolyzer that is operated under conditions where dissolved sulfur dioxide depolarizes the anodic reaction, resulting in substantial voltage reduction. Low cell voltage is essential for both thermodynamic efficiency and hydrogen cost. Sulfur dioxide is oxidized at the anode, producing sulfuric acid that is sent to the high temperature acid decomposition portion of the cycle. The electrolyzer cell uses the membrane electrode assembly (MEA) concept. The anode and cathode are formed by spraying platinum containing catalyst on both sides of a Proton Exchange Membrane (PEM). In most testing the material of the PEM was NafionR. The electrolyzer cell active area can be as large as 54.8 cm{sup 2}. Feed to the anode of the electrolyzer is a sulfuric acid solution containing sulfur dioxide. The partial pressure of sulfur dioxide could be varied in the

  15. Test Results From a High Power Linear Alternator Test Rig

    NASA Technical Reports Server (NTRS)

    Birchenough, Arthur G.; Hervol, David S.; Gardner, Brent G.

    2010-01-01

    Stirling cycle power conversion is an enabling technology that provides high thermodynamic efficiency but also presents unique challenges with regard to electrical power generation, management, and distribution. The High Power Linear Alternator Test Rig (HPLATR) located at the NASA Glenn Research Center (GRC) in Cleveland, Ohio is a demonstration test bed that simulates electrical power generation from a Stirling engine driven alternator. It implements the high power electronics necessary to provide a well regulated DC user load bus. These power electronics use a novel design solution that includes active rectification and power factor control, active ripple suppression, along with a unique building block approach that permits the use of high voltage or high current alternator designs. This report describes the HPLATR, the test program, and the operational results.

  16. Test Results from a High Power Linear Alternator Test Rig

    NASA Technical Reports Server (NTRS)

    Birchenough, Arthur G.; Hervol, David S.; Gardner, Brent G.

    2010-01-01

    Stirling cycle power conversion is an enabling technology that provides high thermodynamic efficiency but also presents unique challenges with regard to electrical power generation, management, and distribution. The High Power Linear Alternator Test Rig (HPLATR) located at the NASA Glenn Research Center (GRC) in Cleveland, OH is a demonstration test bed that simulates electrical power generation from a Stirling engine driven alternator. It implements the high power electronics necessary to provide a well regulated DC user load bus. These power electronics use a novel design solution that includes active rectification and power factor control, active ripple suppression, along with a unique building block approach that permits the use of high voltage or high current alternator designs. This presentation describes the HPLATR, the test program, and the operational results.

  17. Cancer related fatigue syndrome in neoplastic diseases.

    PubMed

    Franc, Magdalena; Michalski, Bogdan; Kuczerawy, Ilona; Szuta, Justyna; Skrzypulec-Plinta, Violetta

    2014-12-01

    Fatigue is one of the most important factors which has a considerable influence on treatment and the life quality of oncological patients. The fatigue syndrome is often diagnosed during cancer treatment and this syndrome is not related to the physical effort. Cancer related fatigue is a patient's subjective, psychologically, physically and emotionally based feeling. It is disproportionate to patient's daily activity. The pathogenesis of this syndrome remains still unknown. However, on the basis of various questionnaires, it is possible to test the disease's complex nature. Cancer related fatigue causes deterioration of patient's life along with lower motivation to struggle with the disease. It is thought that the factor which increases the incidence of cancer related fatigue is a long-term use of drugs such as opioids, benzodiazepine, and medicines containing codeine, tranquilizers, anxiolytics and antidepressants. On the basis of the results, one can choose an appropriate treatment method for cancer related fatigue such as rehabilitation, psychotherapy or public assistance. A great number of patients consider excessive fatigue a typical concomitant symptom in neoplastic disease; therefore, they do not report it. It is of a paramount importance to make patients aware of the fact that cancer related fatigue is a serious disease which can be treated. PMID:26327879

  18. Cancer related fatigue syndrome in neoplastic diseases

    PubMed Central

    Michalski, Bogdan; Kuczerawy, Ilona; Szuta, Justyna; Skrzypulec-Plinta, Violetta

    2014-01-01

    Fatigue is one of the most important factors which has a considerable influence on treatment and the life quality of oncological patients. The fatigue syndrome is often diagnosed during cancer treatment and this syndrome is not related to the physical effort. Cancer related fatigue is a patient's subjective, psychologically, physically and emotionally based feeling. It is disproportionate to patient's daily activity. The pathogenesis of this syndrome remains still unknown. However, on the basis of various questionnaires, it is possible to test the disease's complex nature. Cancer related fatigue causes deterioration of patient's life along with lower motivation to struggle with the disease. It is thought that the factor which increases the incidence of cancer related fatigue is a long-term use of drugs such as opioids, benzodiazepine, and medicines containing codeine, tranquilizers, anxiolytics and antidepressants. On the basis of the results, one can choose an appropriate treatment method for cancer related fatigue such as rehabilitation, psychotherapy or public assistance. A great number of patients consider excessive fatigue a typical concomitant symptom in neoplastic disease; therefore, they do not report it. It is of a paramount importance to make patients aware of the fact that cancer related fatigue is a serious disease which can be treated. PMID:26327879

  19. Prevalence of Walking-Related Motor Fatigue in Persons With Multiple Sclerosis: Decline in Walking Distance Induced by the 6-Minute Walk Test.

    PubMed

    Leone, Carmela; Severijns, Deborah; Doležalová, Vendula; Baert, Ilse; Dalgas, Ulrik; Romberg, Anders; Bethoux, Francois; Gebara, Benoit; Santoyo Medina, Carmen; Maamâgi, Heigo; Rasova, Kamila; Maertens de Noordhout, Benoît; Knuts, Kathy; Skjerbaek, Anders; Jensen, Ellen; Wagner, Joanne M; Feys, Peter

    2016-05-01

    Objective To investigate the individual occurrence of walking-related motor fatigue in persons with multiple sclerosis (PwMS), according to disability level and disease phenotype.Study design This was a cross-sectional, multinational study.Participants They were 208 PwMS from 11 centers with Expanded Disability Status Scale (EDSS) scores up to 6.5.Methods The percentage change in distance walked (distance walked index, DWI) was calculated between minute 6 and 1 (DWI6-1) of the 6-Minute Walk Test (6MWT). Its magnitude was used to classify participants into 4 subgroups: (1) DWI6-1[≥5%], (2) DWI6-1[5%; -5%], (3) DWI6-1[-5%; > -15%], and (4) DWI6-1[≤-15%]. The latter group was labeled as having walking-related motor fatigue. PwMS were stratified into 5 subgroups based on the EDSS (0-2.5, 3-4, 4.5-5.5, 6, 6.5) and 3 subgroups based on MS phenotype (relapsing remitting [RR], primary progressive [PP], and secondary progressive [SP]).Results The DWI6-1was ≥5% in 16 PwMS (7.7%), between 5% and -5% in 70 PwMS (33.6%), between -5% and -15% in 58 PwMS (24%), and ≤-15% in 64 PwMS (30.8%). The prevalence of walking-related motor fatigue (DWI6-1[≤-15%]) was significantly higher among the progressive phenotype (PP = 50% and SP = 39%; RR = 15.6%) and PwMS with higher disability level (EDSS 4.5-5.5 = 48.3%, 6 = 46.3% and 6.5 = 51.5%, compared with EDSS 0-2.5 = 7.8% and 3-4 = 16.7%;P< .05). Stepwise multiple regression analysis indicated that EDSS, but not MS phenotype, explained a significant part of the variance in DWI6-1(R(2)= 0.086;P< .001).Conclusion More than one-third of PwMS showed walking-related motor fatigue during the 6MWT, with its prevalence greatest in more disabled persons (up to 51%) and in those with progressive MS phenotype (up to 50%). Identification of walking-related motor fatigue may lead to better-tailored interventions. PMID:26216790

  20. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    SciTech Connect

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-21

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the potential development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a liquid metal cooled reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  1. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-01

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  2. Ultrasonic Attenuation Results of Thermoplastic Resin Composites Undergoing Thermal and Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.

    1998-01-01

    As part of an effort to obtain the required information about new composites for aviation use, materials and NDE researchers at NASA are jointly performing mechanical and NDE measurements on new composite materials. The materials testing laboratory at NASA is equipped with environmental chambers mounted on load frames that can expose composite materials to thermal and loading cycles representative of flight protocols. Applying both temperature and load simultaneously will help to highlight temperature and load interactions during the aging of these composite materials. This report highlights our initial ultrasonic attenuation results from thermoplastic composite samples that have undergone over 4000 flight cycles to date. Ultrasonic attenuation measurements are a standard method used to assess the effects of material degradation. Recently, researchers have shown that they could obtain adequate contrast in the evaluation of thermal degradation in thermoplastic composites by using frequencies of ultrasound on the order of 24 MHz. In this study, we address the relationship of attenuation measured at lower frequencies in thermoplastic composites undergoing both thermal and mechanical loading. We also compare these thermoplastic results with some data from thermoset composites undergoing similar protocols. The composite s attenuation is reported as the slope of attenuation with respect to frequency, defined as b = Da(f)/Df. The slope of attenuation is an attractive parameter since it is quantitative, yet does not require interface corrections like conventional quantitative attenuation measurements. This latter feature is a consequence of the assumption that interface correction terms are frequency independent. Uncertainty in those correction terms can compromise the value of conventional quantitative attenuation data. Furthermore, the slope of the attenuation more directly utilizes the bandwidth information and in addition, the bandwidth can be adjusted in the post

  3. Arc melter demonstration baseline test results

    SciTech Connect

    Soelberg, N.R.; Chambers, A.G.; Anderson, G.L.; Oden, L.L.; O`Connor, W.K.; Turner, P.C.

    1994-07-01

    This report describes the test results and evaluation for the Phase 1 (baseline) arc melter vitrification test series conducted for the Buried Waste Integrated Demonstration program (BWID). Phase 1 tests were conducted on surrogate mixtures of as-incinerated wastes and soil. Some buried wastes, soils, and stored wastes at the INEL and other DOE sites, are contaminated with transuranic (TRU) radionuclides and hazardous organics and metals. The high temperature environment in an electric arc furnace may be used to process these wastes to produce materials suitable for final disposal. An electric arc furnace system can treat heterogeneous wastes and contaminated soils by (a) dissolving and retaining TRU elements and selected toxic metals as oxides in the slag phase, (b) destroying organic materials by dissociation, pyrolyzation, and combustion, and (c) capturing separated volatilized metals in the offgas system for further treatment. Structural metals in the waste may be melted and tapped separately for recycle or disposal, or these metals may be oxidized and dissolved into the slag. The molten slag, after cooling, will provide a glass/ceramic final waste form that is homogeneous, highly nonleachable, and extremely durable. These features make this waste form suitable for immobilization of TRU radionuclides and toxic metals for geologic timeframes. Further, the volume of contaminated wastes and soils will be substantially reduced in the process.

  4. Preliminary test results for the SVX4

    SciTech Connect

    Christofek, L.; Hanagaki, K.; Rapidis, P.; Utes, M.; /Fermilab

    2005-06-01

    We present and summarize the preliminary test results for SVX4 chip testing. There are presently two versions of the SVX4. Version 2 has on-chip bypassing and Version 1 does not. The on-chip bypassing is a layer of transistors under the front-end analog pipeline that acts as a bypassing capacitor for the voltage supply. Its size is about a microfarad. We aggressively choose to test Version 2 because of this feature. The feature is advantageous for hybrid design because it eliminates the need for an additional passive component on the hybrid itself by placing it on the actual SVX4 die. Also, the SVX4 was designed to operate in two modes: D. and CDF. One can set which mode the chip will operate by placing a jumper in the proper position on the SVX4 chip carrier. In either mode, the chip can either use the operating parameters from the shift register or the shadow register. Similarly, this is selected by placing a jumper on the SVX4 chip carrier. This chip has this feature because it was unknown whether the new design of the shadow register would be operable. The shadow register is also call the SEU register or Single Event Upset register. An introduction into the functionality of the chip and an explanation on the difference between D. and CDF mode can be found in the SVX4 User's Manual [1].

  5. Strain Energy Approach for Axial and Torsional Fatigue Life Prediction in Aged NiCrMoV Steels

    NASA Astrophysics Data System (ADS)

    Song, Gee Wook; Hyun, Jung Seob; Ha, Jeong Soo

    Axial and torsional low cycle fatigue tests were performed for NiCrMoV steels serviced low-pressure turbine rotor of nuclear power plant. The results were used to evaluate multiaxial fatigue life models including Tresca, von Mises and Brown and Miller's critical plane. The fatigue life predicted by the multiaxial fatigue models didn't correspond with the experimental results in small strain range. We proposed the total strain energy density model to predict torsional fatigue life from axial fatigue data. The total strain energy density model was found to best correlate the experimental data with predictions being within a factor of 2.

  6. Etude de la resistance en fatigue des materiaux bitumineux

    NASA Astrophysics Data System (ADS)

    Touhara, Radouen

    The goal of this research program is to evaluate and characterize the fatigue behaviour of two GB20 hot mix asphalt made with two different bitumen. One of them is made in laboratory with a straight-run PG58-28 bitumen, while the second mix was made in an asphalt plant with a PG64-28 bitumen. Two characterization tests, in homogeneous conditions, done in traction/compression on cylindrical specimens are used in this study. First, a complex modulus test performed in the linear viscoelasticity (LVE) domain is used to characterize the mixes and second, a fatigue test is done to evaluate the mixes performances. The fatigue tests were done in strain controlled at different amplitude. All fatigue tests were performed at 10Hz, but at different temperatures (10, 20 and 30°C) in order to evaluate the effect of the temperature on the fatigue behaviour of those mixes. In this document, the results are presented, and the analysis of the results as a function of the grade of bitumen, the tests’ temperature and the dispersion of the results is performed. Also, the DGCB method is applied to the fatigue results to calculate the rate of damage per cycle followed by a study of the different failure criteria (Nf) to predict the fatigue life of asphalt mixes. Keywords: bituminous materials, fatigue, complex modulus, Damage.

  7. The NASA B-757 HIRF Test Series: Flight Test Results

    NASA Technical Reports Server (NTRS)

    Moeller, Karl J.; Dudley, Kenneth L.

    1997-01-01

    In 1995, the NASA Langley Research Center conducted a series of aircraft tests aimed at characterizing the electromagnetic environment (EME) in and around a Boeing 757 airliner. Measurements were made of the electromagnetic energy coupled into the aircraft and the signals induced on select structures as the aircraft was flown past known RF transmitters. These measurements were conducted to provide data for the validation of computational techniques for the assessment of electromagnetic effects in commercial transport aircraft. This paper reports on the results of flight tests using RF radiators in the HF, VHF, and UHF ranges and on efforts to use computational and analytical techniques to predict RF field levels inside the airliner at these frequencies.

  8. Results from the Cooler and Lead Tests

    SciTech Connect

    Green, Michael A

    2010-06-10

    The report presents the results of testing MICE spectrometer magnet current leads on a test apparatus that combines both the copper leads and the high temperature superconducting (HTS) leads with a single Cryomech PT415 cooler and liquid helium tank. The current is carried through the copper leads from 300 K to the top of the HTS leads. The current is then carried through the HTS leads to a feed-through from the vacuum space to the inside of a liquid helium tank. The experiment allows one to measure the performance of both cooler stages along with the performance of the leads. While the leads were powered we measured the voltage drops through the copper leads, through the HTS leads, through spliced to the feed-through, through the feed-through and through the low-temperature superconducting loop that connects one lead to the other. Measurements were made using the leads that were used in spectrometer magnet 1A and spectrometer magnet 2A. These are the same leads that were used for Superbend and Venus magnets at LBNL. The IL/A for these leads was 5.2 x 10{sup 6} m{sup -1}. The leads turned out to be too long. The same measurements were made using the leads that were installed in magnet 2B. The magnet 2B leads had an IL/A of 3.3 x 10{sup 6} A m{sup -1}. This report discusses the cooler performance and the measured electrical performance of the lead circuit that contains the copper leads and the superconducting leads. All of the HTS leads that were installed in magnet 2B were current tested using this apparatus.

  9. Results and Analysis from Space Suit Joint Torque Testing

    NASA Technical Reports Server (NTRS)

    Matty, Jennifer E.; Aitchison, Lindsay

    2009-01-01

    A space suit s mobility is critical to an astronaut s ability to perform work efficiently. As mobility increases, the astronaut can perform tasks for longer durations with less fatigue. The term mobility, with respect to space suits, is defined in terms of two key components: joint range of motion and joint torque. Individually these measures describe the path which in which a joint travels and the force required to move it through that path. Previous space suits mobility requirements were defined as the collective result of these two measures and verified by the completion of discrete functional tasks. While a valid way to impose mobility requirements, such a method does necessitate a solid understanding of the operational scenarios in which the final suit will be performing. Because the Constellation space suit system requirements are being finalized with a relatively immature concept of operations, the Space Suit Element team elected to define mobility in terms of its constituent parts to increase the likelihood that the future pressure garment will be mobile enough to enable a broad scope of undefined exploration activities. The range of motion requirements were defined by measuring the ranges of motion test subjects achieved while performing a series of joint maximizing tasks in a variety of flight and prototype space suits. The definition of joint torque requirements has proved more elusive. NASA evaluated several different approaches to the problem before deciding to generate requirements based on unmanned joint torque evaluations of six different space suit configurations being articulated through 16 separate joint movements. This paper discusses the experiment design, data analysis and results, and the process used to determine the final values for the Constellation pressure garment joint torque requirements.

  10. Advanced wing design survivability testing and results

    NASA Technical Reports Server (NTRS)

    Bruno, J.; Tobias, M.

    1992-01-01

    Composite wings on current operational aircraft are conservatively designed to account for stress/strain concentrations, and to assure specified damage tolerance. The technology that can lead to improved composite wing structures and associated structural efficiency is to increase design ultimate strain levels beyond their current limit of 3500 to 4000 micro-in/in to 6000 micro-in/in without sacrificing structural integrity, durability, damage tolerance, or survivability. Grumman, under the sponsorship of the Naval Air Development Center (NADC), has developed a high-strain composite wing design for a subsonic aircraft wing using novel and innovative design concepts and manufacturing methods, while maintaining a state-of-the-art fiber/resin system. The current advanced wing design effort addressed a tactical subsonic aircraft wing using previously developed, high-strain wing design concepts in conjunction with newer/emerging fiber and polymer matrix composite (PMC) materials to achieve the same goals, while reducing complexity. Two categories of advanced PMC materials were evaluated: toughened thermosets; and engineered thermoplastics. Advanced PMC materials offer the technological opportunity to take maximum advantage of improved material properties, physical characteristics, and tailorability to increase performance and survivability over current composite structure. Damage tolerance and survivability to various threats, in addition to structural integrity and durability, were key technical issues addressed during this study, and evaluated through test. This paper focuses on the live-fire testing, and the results performed to experimentally evaluate the survivability of the advanced wing design.

  11. Smart wing wind tunnel test results

    NASA Astrophysics Data System (ADS)

    Scherer, Lewis B.; Martin, Christopher A.; Appa, Kari; Kudva, Jayanth N.; West, Mark N.

    1997-05-01

    The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A-18 E/F for the on-going DARPA/WL Smart Materials and Structures-Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (Cm), increased rolling moment (Cl) and improved pressure distribution. These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16 ft Transonic Dynamic Tunnel. Among the benefits demonstrated are 8 - 12% increase in rolling moment due to wing twist, a 10 - 15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.

  12. The effects of mats on back and leg fatigue.

    PubMed

    Kim, J Y; Stuart-Buttle, C; Marras, W S

    1994-02-01

    Prolonged standing is common in many industrial workplaces. It is also quite common for workers to complain of discomfort in the back and legs as a result of prolonged standing. Mats are often provided for the worker to relieve this fatigue. However, there is no quantitative evidence that these mats relieve leg and back fatigue. Five subjects were asked to stand on a concrete surface and two mat surfaces for prolonged periods of time. Spectral electromyographic analyses indicated that mats reduced localized muscle fatigue in the erector spinae muscle only. Furthermore, this fatigue reduction occurred only with the more compressible of the two mats tested. These results imply that localized muscular fatigue in the leg may not be relieved with 'anti-fatigue' mats, and some of these mats only benefit the back. PMID:15676945

  13. Boeing's High Voltage Solar Tile Test Results

    NASA Technical Reports Server (NTRS)

    Reed, Brian J.; Harden, David E.; Ferguson, Dale C.; Snyder, David B.

    2002-01-01

    Real concerns of spacecraft charging and experience with solar array augmented electrostatic discharge arcs on spacecraft have minimized the use of high voltages on large solar arrays despite numerous vehicle system mass and efficiency advantages. Boeing's solar tile (patent pending) allows high voltage to be generated at the array without the mass and efficiency losses of electronic conversion. Direct drive electric propulsion and higher power payloads (lower spacecraft weight) will benefit from this design. As future power demand grows, spacecraft designers must use higher voltage to minimize transmission loss and power cable mass for very large area arrays. This paper will describe the design and discuss the successful test of Boeing's 500-Volt Solar Tile in NASA Glenn's Tenney chamber in the Space Plasma Interaction Facility. The work was sponsored by NASA's Space Solar Power Exploratory Research and Technology (SERT) Program and will result in updated high voltage solar array design guidelines being published.

  14. Lunar Water Resource Demonstration (LWRD) Test Results

    NASA Technical Reports Server (NTRS)

    Muscatello, Anthony C.; Captain, Janine E.; Quinn, Jacqueline W.; Gibson, Tracy L.; Perusich, Stephen A.; Weis, Kyle H.

    2009-01-01

    NASA has undertaken the In-Situ Resource Utilization (lSRU) project called RESOLVE (Regolith and Environment Science & Oxygen and Lunar Volatile Extraction). This project is an Earth-based lunar precursor demonstration of a system that could be sent to explore permanently shadowed polar lunar craters, where it would drill into regolith, quantify the volatiles that are present, and extract oxygen by hydrogen reduction of iron oxides. The RESOLVE chemical processing system was mounted within the CMU rover "Scarab" and successfully demonstrated on Hawaii's Mauna Kea volcano in November 2008. This technology could be used on Mars as well. As described at the 2008 Mars Society Convention, the Lunar Water Resource Demonstration (LWRD) supports the objectives of the RESOLVE project by capturing and quantifying water and hydrogen released by regolith upon heating. Field test results for the quantification of water using LWRD showed that the volcanic ash (tephra) samples contained 0.15-0.41% water, in agreement with GC water measurements. Reduction of the RH in the surge tank to near zero during recirculation show that the water is captured by the water beds as desired. The water can be recovered by heating the Water Beds to 230 C or higher. Test results for the capture and quantification of pure hydrogen have shown that over 90% of the hydrogen can be captured and 98% of the absorbed hydrogen can be recovered upon heating the hydride to 400 C and desorbing the hydrogen several times into the evacuated surge tank. Thus, the essential requirement of capturing hydrogen and recovering it has been demonstrated. ,

  15. A study of elevated temperature testing techniques for the fatigue behavior of PMCS: Application to T650-35/AMB21

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, Andrew L.; Gastelli, Michael G.; Ellis, John R.; Burke, Christopher S.

    1995-01-01

    An experimental study was conducted to investigate the mechanical behavior of a T650-35/AMB21 eight-harness satin weave polymer composite system. Emphasis was placed on the development and refinement of techniques used in elevated temperature uniaxial PMC testing. Issues such as specimen design, gripping, strain measurement, and temperature control and measurement were addressed. Quasi-static tensile and fatigue properties (R(sub sigma) = 0.1) were examined at room and elevated temperatures. Stiffness degradation and strain accumulation during fatigue cycling were recorded to monitor damage progression and provide insight for future analytical modeling efforts. Accomplishments included an untabbed dog-bone specimen design which consistently failed in the gage section, accurate temperature control and assessment, and continuous in-situ strain measurement capability during fatigue loading at elevated temperatures. Finally, strain accumulation and stiffness degradation during fatigue cycling appeared to be good indicators of damage progression.

  16. Field Lysimeter Test Facility: Second year (FY 1989) test results

    SciTech Connect

    Campbell, M.D.; Gee, G.W.; Kanyid, M.J.; Rockhold, M.L.

    1990-04-01

    The Record of Decision associated with the Hanford Defense Waste Environmental Impact Statement (53 FR 12449-53) commits to an evaluation of the use of protective barriers placed over near-surface wastes. The barrier must protect against wind and water erosion and limit plant and animal intrusion and infiltration of water. Successful conclusion of this program will yield the necessary protective barrier design for near-surface waste isolation. This report presents results from the second year of tests at the FLTF. The primary objective of testing protective barriers at the FLTF was to measure the water budgets within the various barriers and assess the effectiveness of their designs in limiting water intrusion into the zone beneath each barrier. Information obtained from these measurements is intended for use in refining barrier designs. Four elements of water budget were measured during the year: precipitation, evaporation, storage, and drainage. Run-off, which is a fifth element of a complete water budget, was made negligible by a lip on the lysimeters that protrudes 5 cm above the soil surface to prevent run-off. A secondary objective of testing protective barriers at the FLTF was to refine procedures and equipment to support data collection for verification of the computer model needed for long-term projections of barrier performance. 6 refs.

  17. A prototype tap test imaging system: Initial field test results

    NASA Astrophysics Data System (ADS)

    Peters, J. J.; Barnard, D. J.; Hudelson, N. A.; Simpson, T. S.; Hsu, D. K.

    2000-05-01

    This paper describes a simple, field-worthy tap test imaging system that gives quantitative information about the size, shape, and severity of defects and damages. The system consists of an accelerometer, electronic circuits for conditioning the signal and measuring the impact duration, a laptop PC and data acquisition and processing software. The images are generated manually by tapping on a grid printed on a plastic sheet laid over the part's surface. A mechanized scanner is currently under development. The prototype has produced images for a variety of aircraft composite and metal honeycomb structures containing flaws, damages, and repairs. Images of the local contact stiffness, deduced from the impact duration using a spring model, revealed quantitatively the stiffness reduction due to flaws and damages, as well as the stiffness enhancement due to substructures. The system has been field tested on commercial and military aircraft as well as rotor blades and engine decks on helicopters. Field test results will be shown and the operation of the system will be demonstrated.—This material is based upon work supported by the Federal Aviation Administration under Contract #DTFA03-98-D-00008, Delivery Order No. IA016 and performed at Iowa State University's Center for NDE as part of the Center for Aviation Systems Reliability program.

  18. Fatigue performance of welded aluminum deck structures

    SciTech Connect

    Haagensen, P.J.; Ranes, M.; Kluken, A.O.; Kvale, I.

    1996-12-01

    Aluminum alloys are used increasingly in load carrying structures where low weight and low maintenance costs are at a premium. Helicopter decks, structures for living quarters and personnel transfer bridges between platforms are examples of offshore applications. While these structures are not usually subjected to high fatigue loads, the increasing use of aluminum in high speed ships, and more recently in highway bridge structures, makes the question of fatigue performance more important. In this paper the fatigue properties of small scale weldments in an AA6005 alloy are compared with the results of fatigue tests on full scale sections of welded extrusions in the same material, which were used in an aluminum bridge deck structure. The fatigue performance is also compared with the fatigue clauses in the new British design code BS8118 for aluminium structures and the proposed Eurocode 9. The prospects of using a new joining technique, friction stir welding (FSW), in the production of large scale panels for deck and ship hull structures is discussed. The FSW process is described briefly, and some fatigue test data are presented.

  19. Results of a Cyclic Load Test of an RB-47E Airplane

    NASA Technical Reports Server (NTRS)

    Huston, Wilber B.

    1959-01-01

    Results of a cyclic load test made by NASA on an EB-47E airplane are given. The test reported on is for one of three B-47 airplanes in a test program set up by the U. S. Air Force to evaluate the effect of wing structural reinforcements on fatigue life. As a result of crack development in the upper fuselage longerons of the other two airplanes in the program, a longeron and fuselage skin modification was incorporated early in the test. Fuselage strain-gage measurements made before and after the longeron modification and wing strain-gage measurements made only after wing reinforcement are summarized. The history of crack development and repair is given in detail. Testing was terminated one sequence short of the planned end of the program with the occurrence of a major crack in the lower right wing skin.

  20. Characterization of micro-contact resistance between a gold nanocrystalline line and a tungsten electrode probe in interconnect fatigue testing.

    PubMed

    Ling, Xue; Wang, Yusheng; Li, Xide

    2014-10-01

    An electromechanically-coupled micro-contact resistance measurement system is built to mimic the contact process during fatigue testing of nanoscale-thickness interconnects using multiple probe methods. The design combines an optical microscope, high-resolution electronic balance, and micromanipulator-controlled electric probe, and is coupled with electrical measurements to investigate microscale contact physics. Experimental measurements are performed to characterize the contact resistance response of the gold nanocrystalline pad of a 35-nm-thick interconnect under mechanical force applied by a tungsten electrode probe. Location of a stable region for the contact resistance and the critical contact force provides better understanding of micro-contact behavior relative to the effects of the contact force and the nature of the contact surface. Increasing contact temperature leads to reduced contact resistance, softens the pad material, and modifies the contact surface. The stability of both contact resistance and interconnect resistance is studied under increasing contact force. Major fluctuations emerge when the contact force is less than the critical contact force, which shows that temporal contact resistance will affect interconnect resistance measurement accuracy, even when using the four-wire method. This performance is demonstrated experimentally by heating the Au line locally with a laser beam. Finally, the contact resistances are calculated using the LET (Li-Etsion-Talke) model together with combined Holm and Sharvin theory under various contact forces. Good agreement between the results is obtained. This research provides a way to measure change in interconnect line resistance directly under a stable contact resistance regime with a two-wire method that will greatly reduce the experimental costs. PMID:25362435

  1. Characterization of micro-contact resistance between a gold nanocrystalline line and a tungsten electrode probe in interconnect fatigue testing

    SciTech Connect

    Ling, Xue; Wang, Yusheng; Li, Xide

    2014-10-15

    An electromechanically-coupled micro-contact resistance measurement system is built to mimic the contact process during fatigue testing of nanoscale-thickness interconnects using multiple probe methods. The design combines an optical microscope, high-resolution electronic balance, and micromanipulator-controlled electric probe, and is coupled with electrical measurements to investigate microscale contact physics. Experimental measurements are performed to characterize the contact resistance response of the gold nanocrystalline pad of a 35-nm-thick interconnect under mechanical force applied by a tungsten electrode probe. Location of a stable region for the contact resistance and the critical contact force provides better understanding of micro-contact behavior relative to the effects of the contact force and the nature of the contact surface. Increasing contact temperature leads to reduced contact resistance, softens the pad material, and modifies the contact surface. The stability of both contact resistance and interconnect resistance is studied under increasing contact force. Major fluctuations emerge when the contact force is less than the critical contact force, which shows that temporal contact resistance will affect interconnect resistance measurement accuracy, even when using the four-wire method. This performance is demonstrated experimentally by heating the Au line locally with a laser beam. Finally, the contact resistances are calculated using the LET (Li–Etsion–Talke) model together with combined Holm and Sharvin theory under various contact forces. Good agreement between the results is obtained. This research provides a way to measure change in interconnect line resistance directly under a stable contact resistance regime with a two-wire method that will greatly reduce the experimental costs.

  2. The Effect of Porosity on Fatigue of Die Cast AM60

    NASA Astrophysics Data System (ADS)

    Yang, Zhuofei; Kang, Jidong; Wilkinson, David S.

    2016-07-01

    AM60 high-pressure die castings are known to contain significant porosity which can affect fatigue life. We have studied this using samples drawn from prototype AM60 shock towers by conducting strain-controlled fatigue tests accompanied by X-ray computed tomography analysis. The results show that the machined surface is the preferential location for fatigue crack development, with pores close to these surfaces serving as initiation sites. Fatigue life shows a strong inverse correlation with the size of the fatigue-crack-initiating pore. Pore shape and pore orientation also influence the response. A supplemental study on surface roughness shows that porosity is the dominant factor in fatigue. Tomography enables the link between porosity and fatigue crack initiation to be clearly identified. These data are complemented by SEM observations of the fracture surfaces which are generally flat and full of randomly oriented serration patterns but without long-range fatigue striations.

  3. The Effect of Porosity on Fatigue of Die Cast AM60

    NASA Astrophysics Data System (ADS)

    Yang, Zhuofei; Kang, Jidong; Wilkinson, David S.

    2016-04-01

    AM60 high-pressure die castings are known to contain significant porosity which can affect fatigue life. We have studied this using samples drawn from prototype AM60 shock towers by conducting strain-controlled fatigue tests accompanied by X-ray computed tomography analysis. The results show that the machined surface is the preferential location for fatigue crack development, with pores close to these surfaces serving as initiation sites. Fatigue life shows a strong inverse correlation with the size of the fatigue-crack-initiating pore. Pore shape and pore orientation also influence the response. A supplemental study on surface roughness shows that porosity is the dominant factor in fatigue. Tomography enables the link between porosity and fatigue crack initiation to be clearly identified. These data are complemented by SEM observations of the fracture surfaces which are generally flat and full of randomly oriented serration patterns but without long-range fatigue striations.

  4. Ex-situ tensile fatigue-creep testing: A powerful tool to simulate in-situ mechanical degradation in fuel cells

    NASA Astrophysics Data System (ADS)

    Sadeghi Alavijeh, A.; Venkatesan, S. V.; Khorasany, R. M. H.; Kim, W. H. J.; Kjeang, E.

    2016-04-01

    An ex-situ tensile fatigue and creep based accelerated stress test (TFC-AST) is proposed to evaluate the mechanical stability of catalyst coated membranes (CCMs) used in fuel cells. The fatigue-creep action of the TFC test is analyzed by tensile and hygrothermal expansion measurements on partially degraded specimens supplemented by microstructural characterization using transmission electron microscopy, revealing significant decay in mechanical properties as well as morphological rearrangement due to the combined fatigue and creep loading. Through comparison with in-situ hygrothermally degraded CCMs, the TFC-AST protocol is demonstrated to be an economical alternative to the costly in-situ mechanical accelerated stress tests that can reduce the test duration by more than 99%.

  5. Bithermal fatigue of a nickel-base superalloy single crystal

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.

    1988-01-01

    The thermomechanical fatigue behavior of a nickel-base superalloy single crystal was investigated using a bithermal test technique. The bithermal fatigue test was used as a simple alternative to the more complex thermomechanical fatigue test. Both in-phase and out-of-phase bithermal tests were performed on (100)-oriented coated and bare Rene N4 single crystals. In out-of-plane bithermal tests, the tensile and compressive halves of the cycle were applied isothermally at 760 and 982 C, respectively, while for the in-phase bithermal tests the temperature-loading sequence was reversed. The bithermal fatigue lives of bare specimens were shorter than the isothermal fatigue lives at either temperature extreme when compared on an inelastic strain basis. Both in-phase and out-of-phase bithermal fatigue life curves converged in the large strain regime and diverged in the small strain regime, out-of-phase resulting in the shortest lives. The coating had no effect on life for specimens cycled in-phase; however, the coating was detrimental for isothermal fatigue at 760 C and for out-of-phase fatigue under large strains.

  6. Summary of CPAS EDU Testing Analysis Results

    NASA Technical Reports Server (NTRS)

    Romero, Leah M.; Bledsoe, Kristin J.; Davidson, John.; Engert, Meagan E.; Fraire, Usbaldo, Jr.; Galaviz, Fernando S.; Galvin, Patrick J.; Ray, Eric S.; Varela, Jose

    2015-01-01

    The Orion program's Capsule Parachute Assembly System (CPAS) project is currently conducting its third generation of testing, the Engineering Development Unit (EDU) series. This series utilizes two test articles, a dart-shaped Parachute Compartment Drop Test Vehicle (PCDTV) and capsule-shaped Parachute Test Vehicle (PTV), both of which include a full size, flight-like parachute system and require a pallet delivery system for aircraft extraction. To date, 15 tests have been completed, including six with PCDTVs and nine with PTVs. Two of the PTV tests included the Forward Bay Cover (FBC) provided by Lockheed Martin. Advancements in modeling techniques applicable to parachute fly-out, vehicle rate of descent, torque, and load train, also occurred during the EDU testing series. An upgrade from a composite to an independent parachute simulation allowed parachute modeling at a higher level of fidelity than during previous generations. The complexity of separating the test vehicles from their pallet delivery systems necessitated the use the Automatic Dynamic Analysis of Mechanical Systems (ADAMS) simulator for modeling mated vehicle aircraft extraction and separation. This paper gives an overview of each EDU test and summarizes the development of CPAS analysis tools and techniques during EDU testing.

  7. Analyzing Educational Testing Service Graduate Major Field Test Results

    ERIC Educational Resources Information Center

    Thornton, Barry; Arbogast, Gordon

    2012-01-01

    The Educational Testing Service (ETS) created the Graduate Major Field Test in Business (GMFT-B) for MBA students. This test is administered to all MBA classes at Jacksonville University for the purpose of measuring student academic achievement and growth, as well as to assess educational outcomes. The test is given in the capstone course,…

  8. Fatigue of die cast zinc alloys

    SciTech Connect

    Schrems, K.K.; Dogan, O.N.; Goodwin, F.E.

    2006-04-01

    The rotating bending fatigue limit of die cast zinc alloy 2, alloy 3, alloy 5, AcuZinc 5, and ZA-8 were determined as a part of an on-going program by ILZRO into the mechanical properties of die cast zinc. The stress-life (S-N) curves of alloys 3, 5, AcuZinc 5, and ZA-8 were determined previously. This presentation reports the results of the S-N curve for Alloy 2 and the calculated fatigue limits for all five alloys. During the previous stress-life testing, the samples were stopped at 10 million cycles and the fatigue limit for alloy 3, alloy 5, and AcuZinc 5 appeared to be higher and the fatigue limit for ZA-8 appeared to be lower than the values reported in the literature. This was further investigated in alloy 5 and ZA-8 by testing continuous cast bulk alloy 5 and ZA-8.

  9. Testing a Theoretical Model of Perceived Self-Efficacy for Cancer-Related Fatigue Self-Management and Optimal Physical Functional Status

    PubMed Central

    Hoffman, Amy J.; von Eye, Alexander; Gift, Audrey G.; Given, Barbara A.; Given, Charles W.; Rothert, Marilyn

    2009-01-01

    Background Critical gaps exist in the understanding of cancer symptoms, particularly for cancer-related fatigue (CRF). Existing theories and models do not examine the key role perceived self-efficacy (PSE) plays in a person's ability to manage symptoms. Objectives To test the hypothesis that physical functional status (PFS) is predicted through patient characteristics, CRF, other symptoms, and PSE for fatigue self-management in persons with cancer. Methods This study is a secondary data analysis from the baseline observation of two randomized control trials. The combined data set includes 298 subjects who were undergoing a course of chemotherapy. Key variables included physiological and contextual patient characteristics, the severity from CRF and other symptoms, PSE, and PFS. Path analysis examined the relationships among the variables in the proposed theoretical model. Results Persons with cancer reported CRF as the most prevalent symptom among a mean of 7.4 other concurrent symptoms. The severity from CRF had a direct and indirect effect on PFS, with CRF having a direct adverse impact on PFS (t = -7.02) and an indirect adverse effect as part of the severity from the other symptoms (t = 9.69) which also adversely impacted PFS (t = -2.71). Consistent with the proposed theoretical model, PSE had a positive effect on the PFS (t = 2.87) of persons with cancer while serving as a mediator between CRF severity and PFS. Discussion Cancer-related fatigure is prevalent and related to the presence of other symptoms, and PSE for fatigue self-management is an important factor influencing CRF and PFS. A foundation is provided for future intervention studies to increase PSE to achieve optimal PFS in persons with cancer. PMID:19092553

  10. A fatigue study of electrical discharge machine (EDM) strain-gage balance materials

    NASA Technical Reports Server (NTRS)

    Rhew, Ray D.

    1989-01-01

    A fatigue study was undertaken to determine how much electrical-discharge-machine (EDM) processing affected the fatigue life of balance materials: EDM and regular milling-machine (MM) samples were compared. Simulation of a typical balance stress configuration was devised for the fatigue testing in order to obtain results more closely related to balance situations. The fatigue testing of the EDM and MM specimens has indicated that the EDM technique does indeed reduce the fatigue life of 15-5PH steel, the first balance material tested. This conclusion was based on comparisons of the specimen fatigue lives with theoretical and manufacturer's data. Hence the EDM surface effects are detrimental to the fatigue life of this balance material.

  11. Biobehavioral Factors Mediate Exercise Effects on Fatigue in Breast Cancer Survivors

    PubMed Central

    Rogers, Laura Q; Vicari, Sandra; Trammell, Rita; Hopkins-Price, Patricia; Fogleman, Amanda; Spenner, Allison; Rao, Krishna; Courneya, Kerry S; Hoelzer, Karen S; Robbs, Randall; Verhulst, Steven

    2015-01-01

    Purpose Examine mediators of fatigue response to an exercise intervention for breast cancer survivors (BCS) in a pilot randomized controlled trial. Methods Postmenopausal BCS (n=46; ≤ Stage II), off primary treatment, and reporting fatigue and/or sleep dysfunction were randomized to a 3-month exercise intervention (160 minutes/week of moderate intensity aerobic walking, twice weekly resistance training with resistance bands) or control group. Six discussion group sessions provided behavioral support to improve adherence. Fatigue, serum cytokines, accelerometer physical activity, cardiorespiratory fitness, sleep dysfunction, and psychosocial factors were assessed at baseline and 3 months. Results Exercise intervention effect sizes for fatigue were: fatigue intensity d=0.30 (p=.34), interference d=−0.38 (p=.22), and general fatigue d=−0.49 (p=.13). Using Freedman-Schatzkin difference-in-coefficients tests, increase in fatigue intensity was significantly mediated by interleukin (IL)-6 (82%), IL-10 (94%), IL-6:IL-10 (49%), and tumor necrosis factor (TNF)-alpha:IL-10 (78%) with reduced sleep dysfunction increasing the relationship between intervention and fatigue intensity rather than mediating intervention effects (−88%). Decrease in fatigue interference was mediated by sleep dysfunction (35%) while IL-10 and pro:anti-inflammatory cytokine ratios increased the relationship between intervention and interference (−25% to −40%). The reduction in general fatigue was significantly mediated by minutes of physical activity (76%), sleep dysfunction (45%), and physical activity enjoyment (40%) with IL-10 (−40%) and IL-6:IL-10 (−11%) increasing the intervention-fatigue relationship. In the intervention group, higher baseline fatigue, anxiety, depression, and perceived exercise barriers interference predicted a greater decline in fatigue interference and/or general fatigue during the intervention. Conclusions Biobehavioral factors mediated and enhanced

  12. The effect of potential upon the high-temperature fatigue crack growth response of low-alloy steels. Part 1: Crack growth results

    SciTech Connect

    James, L.A.; Moshier, W.C.

    1997-04-01

    Corrosion-fatigue crack propagation experiments were conducted on several low-alloy steels in elevated temperature aqueous environments, and experimental parameters included temperature, sulfur content of the steel, applied potential level, and dissolved hydrogen (and in one case, dissolved oxygen) concentration in the water. Specimen potentials were controlled potentiostatically, and the observation (or non-observation) of accelerated fatigue crack growth rates was a complex function of the above parameters. Electrochemical results and the postulated explanation for the complex behavior are given in Part II.

  13. What Do the Results of Genetic Tests Mean?

    MedlinePlus

    ... genetic tests mean? What do the results of genetic tests mean? The results of genetic tests are ... type of result. For more information about interpreting genetic test results: The National Cancer Institute fact sheet ...

  14. Surface topography and the impact on fatigue performance

    NASA Astrophysics Data System (ADS)

    Ardi, D. T.; Li, Y. G.; Chan, K. H. K.; Blunt, L.; Bache, M. R.

    2015-03-01

    Areal characterization was applied to plain fatigue specimens manufactured from a nickel-based superalloy, Alloy 720Li, to determine the impact of machined/finished surface topography on fatigue performance of this material. Samples were subjected to fatigue testing in the as-turned and shot peened conditions to study the interaction between residual stresses and topography in influencing the fatigue performance. The turning process was deliberately manipulated to produce three distinct finishes which were subsequently given an identical shot peening, resulting in six grades of surface topography. Surface topography was found to influence fatigue even in the presence of peened compressive residual stresses by promoting crack initiation at valley sites. Both the roughness amplitude and spatial characteristics of the surface were found to be important when correlating to fatigue performance.

  15. Effects of LWR coolant environments on fatigue lives of austenitic stainless steels.

    SciTech Connect

    Chopra, O. K.

    1998-01-13

    Fatigue tests have been conducted on Types 304 and 316NG stainless steels to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on the fatigue lives of these steels. The results confirm significant decreases in fatigue life in water. Unlike the situation with ferritic steels, environmental effects on Types 304 and 316NG stainless steel are more pronounced in low-DO than in high-DO water. Experimental results have been compared with estimates of fatigue life based on a statistical model. The formation and growth of fatigue cracks in air and water environments are discussed.

  16. Power Actuation and Switching Module Test Results

    NASA Technical Reports Server (NTRS)

    Carr, Greg; Deligiannis, Frank; Franco, Lauro; Jones, Loren; Lam, Barbara; Nelson, Ron; Pantaleon, Jose; Ruiz, Ian; Treichler, John; Wester, Gene

    2006-01-01

    The X2000 Power System Electronics (PSE) is a Jet Propulsion Laboratory (JPL) task to develop a new generation of power system building blocks for use on future deep-space missions. The effort includes the development of electronic components and modules that can be used as building blocks in the design of generic spacecraft power systems. All X2000 avionics components and modules are designed for use in centralized or distributed spacecraft architectures. The Power Actuation and Switching Module (PASM) has been developed under the X2000 program. This component enables a modular and scalable design approach for power switching applications, which can result in a wide variety of power switching architectures using this simple building block. The PASM is designed to provide most of the necessary power switching functions of spacecraft for various Deep Space missions including future missions to Mars, comets, Jupiter and its moons. It is fabricated using an ASIC process that is tolerant of high radiation. The development included two application specific integrated circuits (ASICs) and support circuitry all packaged using High Density Interconnect (HDI) technology. It can be operated in series or parallel with other PASMs. It can be used as a high-side or low-side switch and it can drive thruster valves, pyrotechnic devices such as NASA standard initiators, bus shunt resistors, and regular spacecraft component loads. Each PASM contains two independent switches with internal current limiting and over-current trip-off functions to protect the power subsystem from load faults. During turnon and turnoff each switch can limit the rate of current change (di/dt) to a value determined by the user. Three-way majority-voted On/Off commandability and full switch status telemetry (both analog and digital) are built into the module. This paper is a follow up to the one presented at he IECEC 2004 conference that will include the lessons learned and test results from the development.

  17. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

  18. Nickel hydrogen cell characterization test results

    NASA Technical Reports Server (NTRS)

    Otzinger, B.

    1980-01-01

    Charge control studies on nickel hydrogen cells are discussed. Characterization test data for the cells are presented in graphical form. The test areas covered were capacity versus temperature, ampere-hour cycling efficiency, and the charge method which involved voltage level with current limiting.

  19. Heaf test results after neonatal BCG.

    PubMed Central

    Crawshaw, P A; Thomson, A H

    1988-01-01

    Heaf testing was carried out on 98 preschool Asian children who had received a BCG vaccination. A strongly positive Heaf reaction (grade 3) occurred in only two children. Heaf testing can still be used in tuberculosis screening after neonatal BCG. PMID:3232997

  20. Honeycomb spacer crush stength test results

    SciTech Connect

    Leader, D.R.

    1993-09-15

    This report discusses aluminum honeycomb spacers, which are used as an energy absorbent material in shipping packages for off site shipment of radioactive materials and which were ordered in two crush strengths, 1,000 psi and 2,000 psi for use in drop tests requested by the Packaging and Transportation group as part of the shipping container rectification process. Both the group as part of the shipping container rectification process. Both the vendor and the SRTC Materials Laboratory performed crush strength measurements on test samples made from the material used to fabricate the actual spacers. The measurements of crush strength made in the SRTC Materials Laboratory are within 100 psi of the measurements made by the manufacturer for all samples tested and all test measurements are within 10% of the specified crush strength, which is acceptable to the P&T group for the planned tests.

  1. An Experimental Investigation of the Effects of Vacuum Environment on the Fatigue Life, Fatigue-Crack-Growth Behavior, and Fracture Toughness of 7075-T6 Aluminum Alloy. Ph.D. Thesis - North Carolina State Univ.

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.

    1972-01-01

    Axial load fatigue life, fatigue-crack propagation, and fracture toughness tests were conducted on 0.090-inch thick specimens made of 7075-T6 aluminum alloy. The fatigue life and fatigue-crack propagation experiments were conducted at a stress ratio of 0.02. Maximum stresses ranged from 33 to 60 ksi in the fatigue life experiments, and from 10 to 40 ksi in the fatigue-crack propagation experiments, and fatigue life experiments were conducted at gas pressures of 760, 0.5, 0.05, and 0.00000005 torr. Fatigue-crack-growth and fracture toughness experiments were conducted at gas pressures of 760 and 5 x 10 to the minus 8th power torr. Residual stress measurements were made on selected fatigue life specimens to determine the effect of such stresses on fatigue life. Analysis of the results from the fatigue life experiments indicated that fatigue life progressively increased as the gas pressure decreased. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue crack growth rates were approximately twice as high in air as in vacuum. Fracture toughness data showed there was essentially no difference in the fracture toughness of 7075-T6 in vacuum and in air.

  2. German bundle shear - cold test results

    SciTech Connect

    Kunze, P.

    1986-01-01

    In the planned Federal Republic of Germany (FRG) reprocessing plant, the mechanical decladding of the fuel elements will be done with a bundle shear. This shear was designed and built with Thyssen Henschel by adapting the experiences of the Wiederaufarbeitungsanlage Karlsruhe (WAK), the FRG reprocessing pilot plant. The tests included boiling water reactor (BWR) and pressurized water reactor (PWR) dummy elements filled with porcelain as well as steel fuel rod simulators. During the test period with prototype bundle shear, some technical improvements have been found that refer both to operating conditions and to remote handling. In 1987 the acceptance tests will be run.

  3. Ultrasonic Fatigue Endurance of Thin Carbon Fiber Sheets

    NASA Astrophysics Data System (ADS)

    Domínguez Almaraz, Gonzalo M.; Ruiz Vilchez, Julio A.; Dominguez, Aymeric; Meyer, Yann

    2016-04-01

    Ultrasonic fatigue tests were carried out on thin carbon fiber sheets (0.3 mm of thickness) to determine the fatigue endurance under very high-frequency loading (20 kHz). This material, called the gas diffusion layer (GDL), plays a major role in the overall performances of proton exchange membrane fuel cells (PEMFCs). The study of its physical-chemical properties is an on-going subject in the literature; nevertheless, no knowledge is available concerning the high-frequency fatigue endurance. A principal difficulty in carrying out ultrasonic fatigue tests on this material was to determine the dimensions of testing specimen to fit the resonance condition. This aspect was solved by modal numerical simulation: The testing specimen has been a combination of a low-strength steel frame (to facilitate the attachment to the ultrasonic machine and to increase the mass of the specimen), and the carbon fiber hourglass-shape profile. Under resonance condition, a stationary elastic wave is generated along the specimen that induces high stress at the neck section and high displacements at the ends. Results show that fatigue life was close to 3 × 108 cycles when the high Von Misses stress at the neck section was 170 MPa, whereas fatigue life attains the 4.5 × 109 cycles when stress decreases to 117 MPa. Crack initiation and propagation were analyzed, and conclusions were drawn concerning the fatigue endurance of these fiber carbon sheets under ultrasonic fatigue testing.

  4. The Effect of Osteoporosis Treatments on Fatigue Properties of Cortical Bone Tissue

    PubMed Central

    Brock, Garry R.; Chen, Julia T.; Ingraffea, Anthony R.; MacLeay, Jennifer; Pluhar, G. Elizabeth; Boskey, Adele L.; van der Meulen, Marjolein C.H.

    2015-01-01

    Bisphosphonates are commonly prescribed for treatment of osteoporosis. Long-term use of bisphosphonates has been correlated to atypical femoral fractures (AFF). AFFs arise from fatigue damage to bone tissue that cannot be repaired due to pharmacologic treatments. Despite fatigue being the primary damage mechanism of AFFs, the effects of osteoporosis treatments on fatigue properties of cortical bone are unknown. To examine if fatigue-life differences occur in bone tissue after different pharmacologic treatments for osteoporosis, we tested bone tissue from the femurs of sheep given a metabolic acidosis diet to induce osteoporosis, followed by treatment with a selective estrogen reception modulator (raloxifene), a bisphosphonate (alendronate or zoledronate), or parathyroid hormone (teriparatide, PTH). Beams of cortical bone tissue were created and tested in four-point bending fatigue to failure. Tissues treated with alendronate had reduced fatigue life and less modulus loss at failure compared to other treatments, while tissue treated with PTH had a prolonged fatigue life. No loss of fatigue life occurred with zoledronate treatment despite its greater binding affinity and potency compared to alendronate. Tissue mineralization measured by microCT did not explain the differences seen in fatigue behavior. Increased fatigue life with PTH suggests that current treatment methods for AFF could have beneficial effects for restoring fatigue life. These results indicate that fatigue life differs with each type of osteoporosis treatment. PMID:25642445

  5. X-48B Preliminary Flight Test Results

    NASA Technical Reports Server (NTRS)

    Taylor, Brian R.

    2009-01-01

    This slide presentation reviews the preliminary Flight tests of the X-48B development program. The X-48B is a blended wing body aircraft that is being used to test various features of the BWB concept. The research concerns the following: (1) Turbofan Development, (2) Intelligent Flight Control and Optimization, (3) Airdata Calibration (4) Parameter Identification (i.e., Determination of the parameters of a mathematical model of a system based on observation of the system inputs and response.)

  6. Stress distribution on a three-unit implant-supported zirconia framework. A 3D finite element analysis and fatigue test

    PubMed Central

    SANNINO, G.; POZZI, A.; SCHIAVETTI, R.; BARLATTANI, A.

    2012-01-01

    SUMMARY Purpose The purpose of this study was to investigate, by finite element analysis (FEA) and fatigue analysis, the influence of different loading conditions on the stress distribution in a 3-unit implant-supported Y-TZP fixed partial denture (FPD). Material and methods A three-dimensional FEM model was developed. The materials used in this study were assumed to be linearly elastic, homogeneous and isotropic. 100 N and 300 N loads over a 0,5 mm2 areas with different angles (0°, 15° and 35°) and locations were applied on the prosthesis and the distribution of equivalent von Mises stress was investigated. A fatigue analysis was carried out too. Results Maximum stresses were found at the connector region of the framework when the intermediate element is loaded (100 N load pattern: 32,9 MPa, 33 MPa and 51,8 MPa; 300 N load pattern: 98,6 MPa, 102,8 MPa and 155,7 MPa, respectively with 0°, 15° and 35° of inclination). Results confirmed the vulnerability of both connector areas even if just one pillar was loaded with an increase in stress when angle of load inclination is larger. The cyclic fatigue evaluation indicates a strong propensity for fatigue behavior, presenting a considerable range of loading conditions. No fracture fatigue occurred with a 100 N force. A 300 N force applied to the pontic produces no fatigue problems because the load is equally shared by whole system. A 300 N force applied to one of the two pillars, or to both implants generates fatigue problems. Conclusion F.E.M. analysis of a 3-unit implant-supported Y-TZPFPD, give accurate information about loading conditions for clinical success over time. Fatigue analysis results show structural reliability of the Y-TZP as framework material for 3-unit posterior FPDs. PMID:23285401

  7. Stereoscopic visual fatigue assessment and modeling

    NASA Astrophysics Data System (ADS)

    Wang, Danli; Wang, Tingting; Gong, Yue

    2014-03-01

    Evaluation of stereoscopic visual fatigue is one of the focuses in the user experience research. It is measured in either subjective or objective methods. Objective measures are more preferred for their capability to quantify the degree of human visual fatigue without being affected by individual variation. However, little research has been conducted on the integration of objective indicators, or the sensibility of each objective indicator in reflecting subjective fatigue. The paper proposes a simply effective method to evaluate visual fatigue more objectively. The stereoscopic viewing process is divided into series of sessions, after each of which viewers rate their visual fatigue with subjective scores (SS) according to a five-grading scale, followed by tests of the punctum maximum accommodation (PMA) and visual reaction time (VRT). Throughout the entire viewing process, their eye movements are recorded by an infrared camera. The pupil size (PS) and percentage of eyelid closure over the pupil over time (PERCLOS) are extracted from the videos processed by the algorithm. Based on the method, an experiment with 14 subjects was conducted to assess visual fatigue induced by 3D images on polarized 3D display. The experiment consisted of 10 sessions (5min per session), each containing the same 75 images displayed randomly. The results show that PMA, VRT and PERCLOS are the most efficient indicators of subjective visual fatigue and finally a predictive model is derived from the stepwise multiple regressions.

  8. The characterization of widespread fatigue damage in fuselage structure

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Willard, Scott A.; Miller, Matthew

    1994-01-01

    The characteristics of widespread fatigue damage (WSFD) in fuselage riveted structure were established by detailed nondestructive and destructive examinations of fatigue damage contained in a full size fuselage test article. The objectives of this were to establish an experimental data base for validating emerging WSFD analytical prediction methodology and to identify first order effects that contribute to fatigue crack initiation and growth. Detailed examinations were performed on a test panel containing four bays of a riveted lap splice joint. The panel was removed from a full scale fuselage test article after receiving 60,000 full pressurization cycles. The results of in situ examinations document the progression of fuselage skin fatigue crack growth through crack linkup. Detailed tear down examinations and fractography of the lap splice joint region revealed fatigue crack initiation sites, crack morphology, and crack linkup geometry. From this large data base, distributions of crack size and locations are presented and discussions of operative damage mechanisms are offered.

  9. Eddy current pulsed thermography for fatigue evaluation of gear

    NASA Astrophysics Data System (ADS)

    Tian, Gui Yun; Yin, Aijun; Gao, Bin; Zhang, Jishan; Shaw, Brian

    2014-02-01

    The pulsed eddy current (PEC) technique generates responses over a wide range of frequencies, containing more spectral coverage than traditional eddy current inspection. Eddy current pulsed thermography (ECPT), a newly developed non-destructive testing (NDT) technique, has advantages such as rapid inspection of a large area within a short time, high spatial resolution, high sensitivity and stand-off measurement distance. This paper investigates ECPT for the evaluation of gear fatigue tests. The paper proposes a statistical method based on single channel blind source separation to extract details of gear fatigue. The discussion of transient thermal distribution and patterns of fatigue contact surfaces as well as the non-contact surfaces have been reported. In addition, the measurement for gears with different cycles of fatigue tests by ECPTand the comparison results between ECPT with magnetic Barkhausen noise (MBN) have been evaluated. The comparison shows the competitive capability of ECPT in fatigue evaluation.

  10. Subrupture Tendon Fatigue Damage

    PubMed Central

    Laudier, Damien M.; Shine, Jean H.; Basta-Pljakic, Jelena; Jepsen, Karl J.; Schaffler, Mitchell B.; Flatow, Evan L.

    2016-01-01

    The mechanical and microstructural bases of tendon fatigue, by which damage accumulates and contributes to degradation, are poorly understood. To investigate the tendon fatigue process, rat flexor digitorum longus tendons were cyclically loaded (1–16 N) until reaching one of three levels of fatigue damage, defined as peak clamp-to-clamp strain magnitudes representing key intervals in the fatigue life: i) Low (6.0%–7.0%); ii) Moderate (8.5%–9.5%); and iii) High (11.0%–12.0%). Stiffness, hysteresis, and clamp-to-clamp strain were assessed diagnostically (by cyclic loading at 1–8 N) before and after fatigue loading and following an unloaded recovery period to identify mechanical parameters as measures of damage. Results showed that tendon clamp-to-clamp strain increased from pre- to post-fatigue loading significantly and progressively with the fatigue damage level (p≤0.010). In contrast, changes in both stiffness and hysteresis were significant only at the High fatigue level (p≤0.043). Correlative microstructural analyses showed that Low level of fatigue was characterized by isolated, transverse patterns of kinked fiber deformations. At higher fatigue levels, tendons exhibited fiber dissociation and localized ruptures of the fibers. Histomorphometric analysis showed that damage area fraction increased significantly with fatigue level (p≤0.048). The current findings characterized the sequential, microstructural events that underlie the tendon fatigue process and indicate that tendon deformation can be used to accurately assess the progression of damage accumulation in tendons. PMID:18683881

  11. Cryogenic optical testing results of JWST aspheric test plate lens

    NASA Astrophysics Data System (ADS)

    Smith, Koby Z.; Towell, Timothy C.

    2011-09-01

    The James Webb Space Telescope (JWST) Secondary Mirror Assembly (SMA) is a circular 740mm diameter beryllium convex hyperboloid that has a 23.5nm-RMS (λ/27 RMS) on-orbit surface figure error requirement. The radius of curvature of the SMA is 1778.913mm+/-0.45mm and has a conic constant of -1.6598+/-0.0005. The on-orbit operating temperature of the JWST SMA is 22.5K. Ball Aerospace & Technologies Corp. (BATC) is under contract to Northrop Grumman Aerospace Systems (NGAS) to fabricate, assemble, and test the JWST SMA to its on-orbit requirements including the optical testing of the SMA at its cryogenic operating temperature. BATC has fabricated and tested an Aspheric Test Plate Lens (ATPL) that is an 870mm diameter fused silica lens used as the Fizeau optical reference in the ambient and cryogenic optical testing of the JWST Secondary Mirror Assembly (SMA). As the optical reference for the SMA optical test, the concave optical surface of the ATPL is required to be verified at the same 20K temperature range required for the SMA. In order to meet this objective, a state-of-the-art helium cryogenic testing facility was developed to support the optical testing requirements of a number of the JWST optical testing needs, including the ATPL and SMA. With the implementation of this cryogenic testing facility, the ATPL was successfully cryogenically tested and performed to less than 10nm-RMS (λ/63 RMS) surface figure uncertainty levels for proper reference backout during the SMA optical testing program.

  12. Results from Grimethorpe PFBC turbine cascade tests

    SciTech Connect

    Not Available

    1986-12-01

    The test program at the Grimethorpe Pressurized Fluidized-Bed Combustion (PFBC) facility included an assessment of the potential for deposition, corrosion, and erosion of gas turbine blade materials when exposed to PFBC off gases. Flue gas from the combustor was fed through three stages of cyclones before entering the cascade. The impulse foils were approximately the size and shape of the first stage blades in the GE MS-1002 gas turbine. The cascade operated through three test series, accumulating a total of 649 hours. The conditions experienced are summarized. The paper lists the alloys tested, and discusses the efficiency of the cyclones, the particle size distribution of the dusts not removed by the cyclones, and corrosion of the turbine blades. 4 references, 1 figure, 2 tables.

  13. Flexible Ablators Char Depths LHMEL Test Results

    NASA Technical Reports Server (NTRS)

    White, Susan; Qu, Vince; Fan, Wendy; Stackpoole, Mairead; Thornton, Jeremy

    2012-01-01

    Char and pyrolysis zone depths give physical evidence of peak temperature reached in depth: The pyrolyzing material acts as a temperature indicator within its characteristic thermal decomposition range. A matrix of novel flexible ablators were laser tested in one component of material screening for NASA Entry, Descent and Landing research for future Mars missions. LHMEL tests were run both on virgin materials, and on previously charred materials for a dual pulse simulation of the heating due to aerocapture followed by atmospheric entry. The test models were machined to expose the cross-sections. Char measurements were made at three locations near the center of the exposed area. Data are presented showing the char depths developed in these flexible materials, grouped by reinforcing fiber and pyrolyzing material type.

  14. Avco Lycoming emission and flight test results

    NASA Technical Reports Server (NTRS)

    Duke, L. C.

    1976-01-01

    The Avco Lycoming flight test program for reduced emissions was conducted to determine and document the lean fuel schedule limits for current production aircraft based on flight safety. Based on analysis of the emissions profile, Avco Lycoming proposed to evaluate the effect of leaner schedules in the idle/taxi, climb, and approach modes. These modes were selected as areas where it was felt that possible improvements could be made with the greatest improvement in cyclic emissions reduction. The fuel systems to produce these leaner stepped fuel schedules were tailored specifically for the flight test.

  15. High temperature, low-cycle fatigue of copper-base alloys in argon. Part 1: Preliminary results for 12 alloys at 1000 F (538 C)

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1973-01-01

    Short-term tensile evaluations at room temperature and 538 C and low-cycle fatigue evaluations at 538 C are presented for the following materials: Zirconium copper-annealed, Zirconium copper-1/4 hard, Zirconium copper-1/2 hard, Tellurium copper-1/2 hard, Chromium copper-SA and aged, OFHC copper-hard, OFHC copper-1/4 hard, OFHC copper-annealed, Silver-as drawn, Zr-Cr-Mg copper-SA, CW and aged, Electroformed copper-30-35 ksi, and Co-Be-Zr- copper-SA, aged. A total of 50 tensile tests and 76 low-cycle fatigue tests were performed using a strain rate of 0.2 percent per second.

  16. Investigation of Gear and Bearing Fatigue Damage Using Debris Particle Distributions

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Lewicki, David G.; Decker, Harry J.

    2004-01-01

    A diagnostic tool was developed for detecting fatigue damage to spur gears, spiral bevel gears, and rolling element bearings. This diagnostic tool was developed and evaluated experimentally by collecting oil debris data from fatigue tests performed in the NASA Glenn Spur Gear Fatigue Rig, Spiral Bevel Gear Test Facility, and the 500hp Helicopter Transmission Test Stand. During each test, data from an online, in-line, inductance type oil debris sensor was monitored and recorded for the occurrence of pitting damage. Results indicate oil debris alone cannot discriminate between bearing and gear fatigue damage.

  17. Shear fatigue crack growth - A literature survey

    NASA Technical Reports Server (NTRS)

    Liu, H. W.

    1985-01-01

    Recent studies of shear crack growth are reviewed, emphasizing test methods and data analyses. The combined mode I and mode II elastic crack tip stress fields are considered. The development and design of the compact shear specimen are described, and the results of fatigue crack growth tests using compact shear specimens are reviewed. The fatigue crack growth tests are discussed and the results of inclined cracks in tensile panels, center cracks in plates under biaxial loading, cracked beam specimens with combined bending and shear loading, center-cracked panels and double edge-cracked plates under cyclic shear loading are examined and analyzed in detail.

  18. Gifted Adolescents: A Handbook of Test Results.

    ERIC Educational Resources Information Center

    Welsh, George S.

    The Governor's School of North Carolina is a residential summer program for talented and gifted juniors and seniors from all over the state. It is designed to provide a distinctive educational experience and to serve as an experimental laboratory for innovative instruction. This handbook reports on an extensive testing program carried out at the…

  19. Phase C Flygt Mixer Test Results

    SciTech Connect

    Poirier, M.R.

    1999-06-08

    The Savannah River Site (SRS) teamed with the Pacific Northwest National Laboratory (PNNL), Oak Ridge National Laboratory (ORNL), and ITT Flygt Corporation to conduct a test program evaluating shrouded axial propeller mixers (Flygt mixers) for heel removal in SRS Tank 19. SRS is identifying and investigating techniques to remove sludge heels from waste tanks such as Tank 19.

  20. Liquid Motion Experiment Flight Test Results

    NASA Technical Reports Server (NTRS)

    Chato David J.; Dalton, Penni J.; Dodge, Franklin T.; Green, Steve

    1998-01-01

    The Liquid Motion Experiment (LME), designed to study the effects of liquid motion in rotating tanks, was flown on STS 84. LME was essentially a spin table that created a realistic nutation motion of scale-model tanks containing liquid. TWo spherical and two cylindrical transparent tanks were tested simultaneously, and three sets of such tanks were employed to vary liquid viscosity, fill level, and propellant management device (PMD) design. All the tanks were approximately 4.5 inches diameter. The primary test measurements were the radial and tangential torques exerted on the tanks by the liquid. Resonant frequencies and damping of the liquid oscillations were determined by sine sweep tests. For a given tank shape, the resonant frequency depended on fill level. For the cylindrical tanks, the resonances had somewhat different frequencies for the tangential axis (0.55 to 0.75 times spin rate) and the radial axis (0.73 to 0.78 times spin rate), and the tangential axis resonance agreed more closely with available analytical models. For the spherical tanks, the resonant frequencies were between 0.74 to 0.77 times the spin rate and were the same for the tangential and radial axes. The damping coefficients varied from about I% to 3% of critical, depending on tank shape, fill level, and liquid viscosity. 'Me viscous energy dissipation rates of the liquid oscillations were determined from sine dwell tests. The LME energy dissipation rates varied from 0.3 to 0.5 times the estimates obtained from scaling previous ground tests and spacecraft flight data. The PNDs sometimes enhanced the resonances and energy dissipation rates and sometimes decreased them, which points out the need to understand better the effects of PMD on liquid motion as a function of PMD and tank design.

  1. Corrosion fatigue behavior and life prediction method under changing temperature condition

    SciTech Connect

    Kanasaki, Hiroshi; Hirano, Akihiko; Iida, Kunihiro; Asada, Yasuhide

    1997-12-01

    Axially strain controlled low cycle fatigue tests of a carbon steel in oxygenated high temperature water were carried out under changing temperature conditions. Two patterns of triangular wave were selected for temperature cycling. One was in-phase pattern synchronizing with strain cycling and the other was an out-of-phase pattern in which temperature was changed in anti-phase to the strain cycling. The fatigue life under changing temperature condition was in the range of the fatigue life under various constant temperature within the range of the changing temperature. The fatigue life of in-phase pattern was equivalent to that of out-of-phase pattern. The corrosion fatigue life prediction method was proposed for changing temperature condition, and was based on the assumption that the fatigue damage increased in linear proportion to increment of strain during cycling. The fatigue life predicted by this method was in good agreement with the test results.

  2. Comparison of ASME Code NB-3200 and NB-3600 results for fatigue analysis of B31.1 branch nozzles

    SciTech Connect

    Nitzel, M.E.; Ware, A.G.; Morton, D.K.

    1996-06-01

    Fatigue analyses wre conducted on two reactor coolant system branch nozzles in an operating PWR designed to the B31.1 Code, for which no explicit fatigue analysis was required by the licensing basis. These analyses were performed as part of resolving issues connected with NRC`s Fatigue Action Plan to determine if the cumulative usage factor (CUF) for these nozzles, using the 1992 ASME Code and representative PWR transients, were comparable to nozzles designed and analyzed to the ASME Code. Both NB-3200 and NB-3600 ASME Code methods were used. NB-3200 analyses included the development of finite element models for each nozzle. Although detailed thermal transients were not available for the plant analyzed, representative transients from similar PWRs were applied in each method. CUFs calculated using NB-3200 methods were significantly less than using NB-3600. The paper points out differences in analysis methods and highlights difficulties and unknowns in performing more detailed analyses to reduce conservative assumptions.

  3. Preliminary Results of Field Emission Cathode Tests

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Kovaleski, Scott D.

    2001-01-01

    Preliminary screening tests of field emission cathodes such as chemical vapor deposited (CVD) diamond, textured pyrolytic graphite, and textured copper were conducted at background pressures typical of electric thruster test facilities to assess cathode performance and stability. Very low power electric thrusters which provide tens to hundreds micronewtons of thrust may need field emission neutralizers that have a capability of tens to hundreds of microamperes. From current voltage characteristics, it was found that the CVD diamond and textured metals cathodes clearly satisfied the Fowler-Nordheim emission relation. The CVD diamond and a textured copper cathode had average current densities of 270 and 380 mA/sq cm, respectively, at the beginning-of-life. After a few hours of operation the cathode emission currents degraded by 40 to 75% at background pressures in the 10(exp -5) Pa to 10(exp -4) Pa range. The textured pyrolytic graphite had a modest current density at beginning-of-life of 84 mA/sq cm, but this cathode was the most stable of all. Extended testing of the most promising cathodes is warranted to determine if current degradation is a burn-in effect or whether it is a long-term degradation process. Preliminary experiments with ferroelectric emission cathodes, which are ceramics with spontaneous electric polarization, were conducted. Peak current densities of 30 to 120 mA/sq cm were obtained for pulse durations of about 500 ns in the 10(exp -4) Pa pressure range.

  4. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  5. Alarm fatigue: a patient safety concern.

    PubMed

    Sendelbach, Sue; Funk, Marjorie

    2013-01-01

    Research has demonstrated that 72% to 99% of clinical alarms are false. The high number of false alarms has led to alarm fatigue. Alarm fatigue is sensory overload when clinicians are exposed to an excessive number of alarms, which can result in desensitization to alarms and missed alarms. Patient deaths have been attributed to alarm fatigue. Patient safety and regulatory agencies have focused on the issue of alarm fatigue, and it is a 2014 Joint Commission National Patient Safety Goal. Quality improvement projects have demonstrated that strategies such as daily electrocardiogram electrode changes, proper skin preparation, education, and customization of alarm parameters have been able to decrease the number of false alarms. These and other strategies need to be tested in rigorous clinical trials to determine whether they reduce alarm burden without compromising patient safety. PMID:24153215

  6. Biomarkers of peripheral muscle fatigue during exercise

    PubMed Central

    2012-01-01

    Background Biomarkers of peripheral muscle fatigue (BPMFs) are used to offer insights into mechanisms of exhaustion during exercise in order to detect abnormal fatigue or to detect defective metabolic pathways. This review aims at describing recent advances and future perspectives concerning the most important biomarkers of muscle fatigue during exercise. Results BPMFs are classified according to the mechanism of fatigue related to adenosine-triphosphate-metabolism, acidosis, or oxidative-metabolism. Muscle fatigue is also related to an immunological response. impaired calcium handling, disturbances in bioenergetic pathways, and genetic responses. The immunological and genetic response may make the muscle susceptible to fatigue but may not directly cause muscle fatigue. Production of BPMFs is predominantly dependent on the type of exercise. BPMFs need to change as a function of the process being monitored, be stable without appreciable diurnal variations, correlate well with exercise intensity, and be present in detectable amounts in easily accessible biological fluids. The most well-known BPMFs are serum lactate and interleukin-6. The most widely applied clinical application is screening for defective oxidative metabolism in mitochondrial disorders by means of the lactate stress test. The clinical relevance of most other BPMFs, however, is under debate, since they often depend on age, gender, physical fitness, the energy supply during exercise, the type of exercise needed to produce the BPMF, and whether healthy or diseased subjects are investigated. Conclusions Though the role of BPMFs during fatigue is poorly understood, measuring BPMFs under specific, standardised conditions appears to be helpful for assessing biological states or processes during exercise and fatigue. PMID:23136874

  7. Test results for robotic manipulator EMMA

    SciTech Connect

    Ramsower, D.C.

    1996-07-30

    Testing was performed at the National Institute of Standards and Technology (NIST) headquarters in Gaithersburg, Maryland, where Grey Pilgrim has experimental space available under a Cooperative R & D Agreement (CRADA) with NIST. Under the CRADA, Grey Pilgrim is tasked with developing a version of EMMA suitable for deployment of a stereo camera on a NIST RoboCrane, a mobile platform with applications to several industrial environments (including hazardous materials) based on the concept of the Steward Platform, a structure with great strength and a minimum of material.

  8. Fatigue life prediction under service load considering strengthening effect of loads below fatigue limit

    NASA Astrophysics Data System (ADS)

    Zhao, Lihui; Zheng, Songlin; Feng, Jinzhi

    2014-11-01

    Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule (PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule (MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are -3.78% and -1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

  9. Fatigue life prediction under service load considering strengthening effect of loads below fatigue limit

    NASA Astrophysics Data System (ADS)

    Zhao, Lihui; Zheng, Songlin; Feng, Jinzhi

    2014-09-01

    Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule (PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule (MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are -3.78% and -1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

  10. The 757 NLF glove flight test results

    NASA Technical Reports Server (NTRS)

    Runyan, L. Jim; Bielak, G. W.; Behbehani, R. A.; Chen, A. W.; Rozendaal, Roger A.

    1987-01-01

    A major concern in the application of a laminar flow wing design to commercial transports is whether laminar flow can be sustained in the presence of the noise environment due to wing mounted turbofan engines. To investigate this issue, a flight test program was conducted using the Boeing 757 flight research airplane with a portion of the wing modified to obtain natural laminar flow. The flight test had two primary objectives. The first was to measure the noise levels on the upper and lower surface of the wing for a range of flight conditions. The second was to investigate the effect of engine noise on laminar boundary layer transition. The noise field on the wing and transition location on the glove were then measured as a function of the engine power setting at a given flight condition. The transition and noise measurement on the glove show that there is no apparent effect of engine noise on the upper surface transition location. On the lower surface, the transition location moved forward 2 to 3 percent chord. A boundary layer stability analysis to the flight data showed that cross flow disturbances were the dominant cause of transition at most flight conditions.

  11. Optical fiber fatigue behavior over very extended periods at low stress levels in the field and in laboratory tests

    NASA Astrophysics Data System (ADS)

    Stockton, David J.; Mayhew, Andi J.

    1999-12-01

    The reliability of optical fiber exposed to relatively high static strains (> 2%) has been extensively modelled and investigated by experiment. Fatigue `knees' have been demonstrated predicting the premature fracture of fiber particularly where elevated temperatures and relatively large volumes of water have been used to soak the samples. The cause has been attributed to simultaneous stress- assisted and stress-free corrosion of the fiber surface. In this paper we show that, a t more moderate strains (1 to 2%) and using a limited volume of water, there is evidence of a strength recovery caused either by a healing process or the observance of some form of lower strain threshold. The expected strength reduction of the fiber, from contemporary models is contrasted to that observed. The unusually high strength retention shown by the test fiber in water is shown to have important implications for optical cable design and for the bending of fiber within joint housings.

  12. Apparatus and method for fatigue testing of a material specimen in a high-pressure fluid environment

    DOEpatents

    Wang, Jy-An; Feng, Zhili; Anovitz, Lawrence M; Liu, Kenneth C

    2013-06-04

    The invention provides fatigue testing of a material specimen while the specimen is disposed in a high pressure fluid environment. A specimen is placed between receivers in an end cap of a vessel and a piston that is moveable within the vessel. Pressurized fluid is provided to compression and tension chambers defined between the piston and the vessel. When the pressure in the compression chamber is greater than the pressure in the tension chamber, the specimen is subjected to a compression force. When the pressure in the tension chamber is greater than the pressure in the compression chamber, the specimen is subjected to a tension force. While the specimen is subjected to either force, it is also surrounded by the pressurized fluid in the tension chamber. In some examples, the specimen is surrounded by hydrogen.

  13. Effects of LWR coolant environments on fatigue lives of austenitic stainless steels

    SciTech Connect

    Chopra, O.K.; Gavenda, D.J.

    1997-07-01

    The ASME Boiler and Pressure Vessel Code fatigue design curves for structural materials do not explicitly address the effects of reactor coolant environments on fatigue life. Recent test data indicate a significant decrease in fatigue life of pressure vessel and piping materials in light water reactor (LWR) environments. Fatigue tests have been conducted on Types 304 and 316NG stainless steel in air and LWR environments to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on fatigue lives of these steels. The results confirm the significant decrease in fatigue life in water. The environmentally assisted decrease in fatigue life depends both on strain rate and DO content in water. A decrease in strain rate from 0.4 to 0.004%/s decreases fatigue life by a factor of {approx} 8. However, unlike carbon and low-alloy steels, environmental effects are more pronounced in low-DO than in high-DO water. At {approx} 0.004%/s strain rate, reduction in fatigue life in water containing <10 ppb D is greater by a factor of {approx} 2 than in water containing {ge} 200 ppb DO. Experimental results have been compared with estimates of fatigue life based on the statistical model. The formation and growth of fatigue cracks in austenitic stainless steels in air and LWR environments are discussed.

  14. Effect of carbide distribution on rolling-element fatigue life of AMS 5749

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Bamberger, E. N.

    1983-01-01

    Endurance tests with ball bearings made of corrosion resistant bearing steel which resulted in fatigue lives much lower than were predicted are discussed. Metallurgical analysis revealed an undesirable carbide distribution in the races. It was shown in accelerated fatigue tests in the RC rig that large, banded carbides can reduce rolling element fatigue life by a factor of approximately four. The early spalling failures on the bearing raceways are attributed to the large carbide size and banded distribution.

  15. High-temperature reverse-bend fatigue strength of Inconel Alloy 625

    SciTech Connect

    Purohit, A.; Greenfield, I.G.; Park, K.B.

    1983-06-01

    Inconel 625 has been selected as the clad material for Upgraded Transient Reactor Test Facility (TREAT Upgrade or TU) fuel assemblies. The range of temperatures investigated is 900 to 1100/sup 0/C. A reverse-bend fatigue test program was selected as the most-effective method of determining the fatigue characteristics of Inconel alloy 625 sheet metal. The paper describes the reverse bend fatigue experiments, the results obtained, and the analysis of data.

  16. A comparison of fatigue loads of wind turbine resulting from a non-Gaussian turbulence model vs. standard ones

    NASA Astrophysics Data System (ADS)

    Gontier, H.; Schaffarczyk, A. P.; Kleinhans, D.; Friedrich, R.

    2007-07-01

    This project funded by the federal ministry of education and research from the research group 'Wind turbulence and its significance in the use of wind energy' handles a comparison between the load ranges for horizontal axis wind turbines resulting from different turbulence models, i.e. between the usual models as defined in the standards and a new model designed by Friedrich and Kleinhans. This should enable an evaluation of the relevance of this new model for wind modelling for wind turbines and if so, provide the community with new tools in wind simulation. Indeed, spectral models do not well reproduce extreme wind increments as met in gusts. Those models simulate using purely Gaussian statistics. However, measurements show that those increments do not follow normal statistics. The new model developed aims at correcting this problem. The turbulence models used are the Kaimal, von Karman and Mann models as defined in the IEC guidelines and the Friedrich-Kleinhans model, based on stochastic processes called Continuous Time Random Walks. The comparison is based on load ranges resulting from an RFC analysis of 100 time series obtained for 100 different seed numbers. Five wind speeds are investigated. The aeroelastic code used is FLEX5. The main conclusion that can be drawn from this study is that the non-Gaussian Friedrich-Kleinhans model produces loads that are significantly different from the loads obtained with the Kaimal model. That proves that the form of the tails of the increment distribution has a major influence on the loads of the wind turbine and should be considered when making fatigue calculations.

  17. Biaxial fatigue properties of thin-walled composite tubes

    NASA Technical Reports Server (NTRS)

    Krempl, E.; Elzey, D. M.; Ayar, T.; Loewy, R. G.

    1984-01-01

    A testing method for obtaining fatigue and fracture data under biaxial loading and for negative R-ratios is described. Thin-walled tubes of 1-in. outer nominal diameter with a tapered grip section were tested in an Axial-Torsion Servohydraulic Testing Machine with a 463 Data Control Processor at frequencies below 10 Hz up to the 1-million cycle range. Room temperature, uniaxial constant amplitude fatigue data for high temperature cure graphite-epoxy material are presented at R = -0.4 for a (+, - 5 deg) fiber orientation. The fatigue curve is almost horizontal. Tests on (+, - 5 deg) 'SP-328' resulted in failures which predominantly originated in the grip section. Presently, a new specimen design is being tested intended to eliminate cracking in the grip section. Biaxial in-phase loading of (0/+, - 45) tubes of Fiberite graphite-epoxy resulted in much steeper fatigue curves than observed under uniaxial loading.

  18. Determination of Rolling-Element Fatigue Life From Computer Generated Bearing Tests

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

    2003-01-01

    Two types of rolling-element bearings representing radial loaded and thrust loaded bearings were used for this study. Three hundred forty (340) virtual bearing sets totaling 31400 bearings were randomly assembled and tested by Monte Carlo (random) number generation. The Monte Carlo results were compared with endurance data from 51 bearing sets comprising 5321 bearings. A simple algebraic relation was established for the upper and lower L(sub 10) life limits as function of number of bearings failed for any bearing geometry. There is a fifty percent (50 percent) probability that the resultant bearing life will be less than that calculated. The maximum and minimum variation between the bearing resultant life and the calculated life correlate with the 90-percent confidence limits for a Weibull slope of 1.5. The calculated lives for bearings using a load-life exponent p of 4 for ball bearings and 5 for roller bearings correlated with the Monte Carlo generated bearing lives and the bearing data. STLE life factors for bearing steel and processing provide a reasonable accounting for differences between bearing life data and calculated life. Variations in Weibull slope from the Monte Carlo testing and bearing data correlated. There was excellent agreement between percent of individual components failed from Monte Carlo simulation and that predicted.

  19. Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions

    PubMed Central

    Rudroff, Thorsten; Kindred, John H.; Ketelhut, Nathaniel B.

    2016-01-01

    Fatigue is one of the most disabling side effects in people with multiple sclerosis. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this “perspective article” we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies, which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments. PMID:27531990

  20. Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions.

    PubMed

    Rudroff, Thorsten; Kindred, John H; Ketelhut, Nathaniel B

    2016-01-01

    Fatigue is one of the most disabling side effects in people with multiple sclerosis. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this "perspective article" we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies, which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments. PMID:27531990

  1. Psychosocial diagnoses occurring after patients present with fatigue

    PubMed Central

    MacKean, Peter Reagh; Stewart, Moira; Maddocks, Heather L.

    2016-01-01

    Abstract Objective To discover the frequency of psychosocial and other diagnoses occurring at the end of a visit when patients present to their FPs with concerns about fatigue. Design Cross-sectional study of patient-FP encounters for fatigue. Setting Ten FP practices in southwestern Ontario. Participants A total of 259 encounters involving 167 patients presenting to their FPs between March 1, 2006, and June 30, 2010, with concerns about fatigue. Main outcome measures The frequency of psychological and social diagnoses made at the end of visits, and whether diagnoses were made by FPs at the end of the visits versus whether the code for fatigue remained. The associations between patient age, sex, fatigue presenting with other symptoms, or the presence of previous chronic conditions and the outcomes was tested. Results Psychosocial diagnoses were made 23.9% of the time. Among psychosocial diagnoses made, depressive disorder and anxiety disorder or anxiety state were diagnosed more often in women (P = .048). Slightly less than 30% of the time, the cause of patients’ fatigue remained undiagnosed at the end of the encounter. A diagnosis was made more often in men. Conclusion Causes of fatigue frequently remain undiagnosed; however, when there is a diagnosis, psychosocial diagnoses are common. Therefore, it would be appropriate for FPs to screen for psychosocial issues when their patients present with fatigue, unless some other diagnosis is evident. Depression and anxiety could be considered particularly among female patients with fatigue. PMID:27521412

  2. Interconnect fatigue design for terrestrial photovoltaic modules

    SciTech Connect

    Mon, G. R.; Moore, D. M.; Ross, Jr., R. G.

    1982-03-01

    Fatigue of solar cell electrical interconnects due to thermal cycling has historically been a major failure mechanism in photovoltaic arrays; the results of a comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data gathered in this study indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable: (1) the prediction of cumulative interconnect failures during the design life of an array field; and (2) the unambiguous - i.e., quantitative - interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field. This procedure yields not only the minimum break-even cost of delivered energy, but also the required degree of interconnect redundancy and an estimate of array power degradation during the design life of the array field. The usefulness of the design algorithms is demonstrated with realistic examples of design optimization, prediction, and service qualification testing.

  3. Recent results of the GAINS test flight

    NASA Astrophysics Data System (ADS)

    Girz, C.

    A demonstration flight of the Global Atmosphere-ocean IN-situ System (GAINS) Prototype III balloon is scheduled to occur in early summer 2002. The 18-m diameter PIII superpressure balloon, built by GSSL, Inc., will float a 135-kg payload at 16 km. Performance of the SpectraTM envelope will be assessed over two day-night cycles. The payload consists of line-of-sight communications for transmitting GPS position, and monitored parameters on balloon and payload state and the internal and external thermal environments. Primary termination is by radio command with several independent backup termination systems. Safe operation of the balloon is ensured by an onboard transponder that keeps the balloon under active air traffic control. The balloon is tracked by an aircraft that will record communications from the balloon and instigate termination of the flight. Mobile ground stations positioned at the launch and recovery locations will also be capable of recording and terminating the flight. A suite of trajectory forecast tools has been developed based on radiosondes and winds from numerical weather models. A GPS surface reflection experiment for determining ocean surface winds will be tested on this platform. Physical and electronic integration of the radio and mechanical systems was completed over the last two years. Data and videos from the June flight will be presented.

  4. Airlift recirculation well test results -- Southern sector

    SciTech Connect

    White, R.M.; Hiergesell, R.A.

    1997-08-01

    Chlorinated solvents used in the A and M-Areas at the Savannah River Site (SRS) from 1952--1982 have contaminated the groundwater under the site. A plume of groundwater contaminated with trichloroethylene (TCE) and perchloroethylene (PCE) in the Lost Lake aquifer is moving generally southward with the natural flow of groundwater. To comply with the requirements of the current SCDHEC Part B Permit, a series of wells is being installed to contain and treat the plume. Airlift Recirculation Wells (ARW) are a new and innovative technology with potential for more cost effective implementation than conventional pump and treat systems. Two Airlift Recirculation Wells have been installed and tested to quantify performance parameters needed to locate a line of these wells along the leading edge of the contaminant plume. The wells proved to be very sensitive to proper development, but after this requirement was met, performance was very good. The Zone of Capture has been estimated to be within a radius of 130--160 ft. around the wells. Thus a line of wells spaced at 250 ft. intervals could intercept the contaminant plume. At SSR-012, TCE was stripped from the groundwater at approximately 1.2 lb./day. The longer term effect of the recirculation wells upon the plume and the degree of recirculation within the aquifer itself will require additional data over a longer time period for an accurate review. Data collection is ongoing.

  5. Panoramic night vision goggle flight test results

    NASA Astrophysics Data System (ADS)

    Franck, Douglas L.; Geiselman, Eric E.; Craig, Jeffrey L.

    2000-06-01

    The Panoramic Night Vision Goggle (PNVG) has begun operational test and evaluation with its 100-degree horizontal by 40-degree vertical field of view (FOV) on different aircraft and at different locations. Two configurations of the PNVG are being evaluated. The first configuration design (PNVG I) is very low in profile and fits underneath a visor. PNVG I can be retained by the pilot during ejection. This configuration is interchangeable with a day helmet mounted tracker and display through a standard universal connector. The second configuration (PNVG II) resembles the currently fielded 40-degree circular FOV Aviator Night Vision Imaging Systems (ANVIS) and is designed for non-ejection seat aircraft and ground applications. Pilots completed subjective questionnaires after each flight to compare the capability of the 100-degree horizontal by 40-degree vertical PNVG to the 40-degree circular ANVIS across different operational tasks. This paper discusses current findings and pilot feedback from the flight trials objectives of the next phase of the PNVG program are also discussed.

  6. Flight Test Results for the NICMOS Cryocooler

    NASA Technical Reports Server (NTRS)

    Dolan, F. X.; McCormick, J. A.; Nellis, G. F.; Sixsmith, H.; Swift, W. L.

    1999-01-01

    In October 1998 a mechanical cryocooler and cryogenic circulator loop were flown on NASA's STS-95 as part of the Hubble Orbital System Test (HOST). The system will be installed on the Hubble Space Telescope (HST) during Service Mission #3 in 2000 and will provide cooling to the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). It will extend the useful life of that instrument by 5 to 10 years. This was the first successful space demonstration of a turbobrayton cryocooler. The cooler is a single stage reverse Brayton type, using low-vibration high-speed miniature turbomachines for the compression and expansion functions. A miniature centrifugal cryogenic circulator is used to deliver refrigerated neon to the instrument. During the mission, the cooler operated without anomalies for approximately 185 hours over a range of conditions to verify its mechanical, thermodynamic and control functions. The cryocooler satisfied all mission objectives including maximum cooldown to near-design operating conditions, warm and cold starts and stops, operation at near-design temperatures, and demonstration of long-term temperature stability. This paper presents a description of the cooler and its operation during the HOST flight.

  7. J-integral values for cracks in conventional fatigue specimens

    SciTech Connect

    O`Donnell, T.P.; O`Donnell, W.J.

    1996-12-01

    Comprehensive S-N fatigue data has been developed worldwide using conventional low-cycle fatigue tests. Such tests use smooth unnotched specimens subjected to controlled axial deflection or strain ranges. The tests must be run in the plastic regime in order to achieve the required cycles-to-failure. Recent developments have highlighted the need to understand and interpret the significance of the resulting strain range vs. cycles to failure data in terms of crack initiation and propagation. Since conventional fatigue tests are conducted in the plastic regime, linear elastic fracture mechanics cannot be used to accurately quantify crack growth in such tests. Elastic-plastic J-integral theory, however, has been shown to provide excellent correlations of crack growth in the elastic, elastic-plastic and grossly-plastic regimes for a wide range of geometric and loading conditions. The authors are applying this theory to the low-cycle fatigue specimen crack behavior. As cracks progress in conventional fatigue specimens, bending becomes significant. Since fatigue testing machines are quite stiff relative to the small fatigue specimens, the ends of the specimen are constrained to remain parallel, and this reduces bending in the cracked cross-section. Three-dimensional finite element elastic-plastic analyses are required to include these constraints in the J-integral solutions.

  8. Shashlik calorimeter Beam-test results

    NASA Astrophysics Data System (ADS)

    Badier, J.; Busson, Ph.; Charlot, C.; Dobrzynski, L.; Tanaka, R.; Bordalo, P.; Ramos, S.; Bityukov, S.; Obraztsov, V.; Ostankov, A.; Zaitchenko, A.; Gninenko, S.; Guschin, E.; Issakov, V.; Mussienko, Y.; Semenjuk, I.

    1994-08-01

    Results from an extensive study of nonprojective Shashlik calorimeter prototypes are reported. Nine (47 × 47 mm 2) towers were exposed to a high energy electron beam at CERN SPS and read out by silicon photodiodes followed by low noise preamplifiers. The main results are the measurements of the energy and shower position resolution and the angular resolution of the electron shower direction. The shower direction measurement is encouraging being in agreement at the tower center with a resolution of σθ(mrad) = 70/√ E (10 mrad for 50 GeV electrons). The uniformity of the calorimeter response is found to be better than ± 1%. The mean light yield measured in Shashlik towers equipped with Kuraray Y7 WLS fibres and aluminized at the front end of the tower is of the order of 13 photons/MeV.

  9. Test results of a prototype dielectric microcalorimeter

    NASA Technical Reports Server (NTRS)

    Pfafman, T. E.; Silver, E.; Labov, S.; Beeman, J.; Goulding, F.; Hansen, W.; Landis, D.; Madden, N.

    1990-01-01

    The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa(1-x)Nb(x)O3 (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. A nonthermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported.

  10. Stability of external and internal implant connections after a fatigue test

    PubMed Central

    Feitosa, Paulo Cesar Pinheiro; de Lima, Ana Paula Barbosa; Silva-Concílio, Laís Regiane; Brandt, William Cunha; Neves, Ana Christina Claro

    2013-01-01

    Objective: The objective of this study was to compare the torque and detorque values of screw intermediates of external hexagon, internal hexagon, and Morse taper implants in single restorations before and after mechanical cycling. Materials and Methods: The study sample was divided into three groups (n = 10) as follows: group EH – external hexagon implant, group IH – internal hexagon implant, and group MT – Morse taper implant. Universal abutments were screwed on the implants, and metal crowns were cemented onto the abutment. The samples were submitted to a mechanical testing of 1 million cycles, with a frequency of 8 cycles per second under a 400 N load. The application and registration of the screw torque (T0) and detorque (T1) values of the intermediate were performed before and after the test. The results were statistically evaluated by analysis of variance (ANOVA) and Tukey's test (α = 0.05). Results: There was no difference between the values of T0 and T1 in the intra-group samples. However, the inter-group difference in T0 between the EH (12.8 N cm) and MT (18.6 N cm) groups and in T1 between the EH (10.4 N cm) and IH (13.8 N cm), EH and MT (19.4 N cm), and MT and IH (P = 0.001) groups were significant. The MT group showed a lower variation of T0 and T1. Conclusion: The internal implants, particularly MT, showed better stability in these cases when used for single restorations. PMID:24926204

  11. Test results of a prototype dielectric microcalorimeter

    SciTech Connect

    Pfafman, T.E.; Silver, E.; Labov, S. ); Beeman, J.; Goulding, F.; Hansen, W.; Landis, D.; Madden, N. )

    1990-08-13

    The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa{sub 1-x}Nb{sub x}O{sub 3} (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. a non-thermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported. 7 refs, 16 figs., 1 tab.

  12. Low-Cycle Fatigue Behavior of Die-Cast Mg Alloys AZ91 and AM60

    NASA Astrophysics Data System (ADS)

    Rettberg, Luke H.; Jordon, J. Brian; Horstemeyer, Mark F.; Jones, J. Wayne

    2012-07-01

    The influence of microstructure and artificial aging response (T6) on the low-cycle fatigue behavior of super vacuum die-cast (SVDC) AZ91 and AM60 has been investigated. Fatigue lifetimes were determined from the total strain-controlled fatigue tests for strain amplitudes of 0.2 pct, 0.4 pct, 0.6 pct, 0.8 pct, and 1.0 pct under fully reversed loading at a frequency of 5 Hz. Cyclic stress-strain behavior was determined using an incremental step test (IST) and compared with the more traditional constant amplitude test. Two locations in a prototype casting were investigated to examine the role of microstructure and porosity on fatigue behavior. At all total strain amplitudes microstructure refinement had a negligible impact on fatigue life because of significant levels of porosity. AM60 showed an improvement in fatigue life at higher strain amplitudes when compared with AZ91 because of higher ductility. T6 heat treatment had no impact on fatigue life. Cyclic stress-strain behavior obtained via the incremental step test varied from constant amplitude test results due to load history effects. The constant amplitude test is believed to be the more accurate test method. In general, larger initiation pores led to shorter fatigue life. The fatigue life of AZ91 was more sensitive to initiation pore size and pore location than AM60 at the lowest tested strain amplitude of 0.2 pct. Fatigue crack paths did not favor any specific phase, interdentritic structure or eutectic structure. A multistage fatigue (MSF) model showed good correlation to the experimental strain-life results. The MSF model reinforced the dominant role of inclusion (pore) size on the scatter in fatigue life.

  13. Fatigue of restorative materials.

    PubMed

    Baran, G; Boberick, K; McCool, J

    2001-01-01

    Failure due to fatigue manifests itself in dental prostheses and restorations as wear, fractured margins, delaminated coatings, and bulk fracture. Mechanisms responsible for fatigue-induced failure depend on material ductility: Brittle materials are susceptible to catastrophic failure, while ductile materials utilize their plasticity to reduce stress concentrations at the crack tip. Because of the expense associated with the replacement of failed restorations, there is a strong desire on the part of basic scientists and clinicians to evaluate the resistance of materials to fatigue in laboratory tests. Test variables include fatigue-loading mode and test environment, such as soaking in water. The outcome variable is typically fracture strength, and these data typically fit the Weibull distribution. Analysis of fatigue data permits predictive inferences to be made concerning the survival of structures fabricated from restorative materials under specified loading conditions. Although many dental-restorative materials are routinely evaluated, only limited use has been made of fatigue data collected in vitro: Wear of materials and the survival of porcelain restorations has been modeled by both fracture mechanics and probabilistic approaches. A need still exists for a clinical failure database and for the development of valid test methods for the evaluation of composite materials. PMID:11603506

  14. Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

    2011-01-01

    The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

  15. Evaluation of an Ultrasound-Aided Deep Rolling Process for Anti-Fatigue Applications

    NASA Astrophysics Data System (ADS)

    Zhu, You-Li; Wang, Kan; Li, Li; Huang, Yuan-Lin

    2009-11-01

    An ultrasound-aided deep rolling process (UADR) for anti-fatigue applications was developed and used for surface enhancement of titanium alloy specimens. The rotating bending fatigue test was performed for the UADR-treated and untreated fatigue specimens. Fractography of the fatigue-fractured specimens was investigated via scanning electronic microscopy (SEM). Surface and subsurface residual stress distributions after UADR treatment were measured by X-ray diffraction method. Surface morphology and roughness were observed and measured via SEM micrograph and a Talysurf roughness tester, respectively. The results showed that a deep layer of residual compressive stress developed and surface roughness was reduced after UADR treatment. Fatigue strength of the titanium alloy specimens was substantially improved. The fractographic examination of the fatigue-fractured specimens showed that the UADR-treated specimens developed finer fatigue striations than the untreated specimen.

  16. Effect of Electromagnetic Treatment on Fatigue Resistance of 2011 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Mohin, M. A.; Toofany, H.; Babutskyi, A.; Lewis, A.; Xu, Y. G.

    2016-08-01

    Beneficial effects of the electromagnetic treatment on fatigue resistance were reported on several engineering alloys. These could be linked to the dislocation activity and the rearrangement of the crystal structure of the material under the electromagnetic field (EMF), resulting in delayed crack initiation. This paper presents an experimental study on the effect of pulsed electromagnetic treatment on the fatigue resistance of 2011 aluminum alloy. Circular cantilever specimens with loads at their ends were tested on rotating fatigue machine SM1090. Fatigue lives of treated and untreated specimens were analyzed and compared systematically. It has been found that the effect of the pulsed electromagnetic treatment on the fatigue resistance is dependent on the intensity of the pulsed EMF and the number of the treatment applied. Clear beneficial effect of the pulsed electromagnetic treatment on the fatigue resistance of the aluminum alloys has been observed, demonstrating a potential new technique to industries for fatigue life extension.

  17. Bearing fatigue investigation 3

    NASA Technical Reports Server (NTRS)

    Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

    1982-01-01

    The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

  18. Extension of recovery time from fatigue by repeated rest with short-term sleep during continuous fatigue load: Development of chronic fatigue model.

    PubMed

    Kanzaki, Akinori; Okauchi, Takashi; Hu, Di; Shingaki, Tomotaka; Katayama, Yumiko; Koyama, Hidenori; Watanabe, Yasuyoshi; Cui, Yilong

    2016-05-01

    Homeostasis is known to be involved in maintaining the optimal internal environment, helping to achieve the best performance of biological functions. At the same time, a deviation from optimal conditions often attenuates the performance of biological functions, and such restricted performance could be considered as individual fatigue, including physical and mental fatigue. The present study seeks to develop an animal model of chronic or subacute fatigue in which the recovery time is extended through the gradual disruption of homeostasis. We show that repeated short-term rest periods with certain lengths of sleep during continuous fatigue loading extend recovery from spontaneous nighttime activity but not physical performance in comparison with a continuous fatigue-loading procedure. Furthermore, the immobility time in a forced swimming test was extended by repeated short-term rests. These results suggest that repeated short-term rest with certain lengths of sleep during continuous fatigue loading is able to extend the recovery from mental fatigue but not from physical fatigue and that this effect might occur via the disruption of a homeostatic mechanism that is involved in restoring the optimal internal environment. © 2016 Wiley Periodicals, Inc. PMID:26864568

  19. Corrosion fatigue of 2219-T87 aluminum alloy

    NASA Technical Reports Server (NTRS)

    Mcmillan, V. C.

    1986-01-01

    Corrosion fatigue studies were conducted on bare, chemical conversion coated, and anodized 2219-T87 aluminum alloy. These tests were performed using a rotating beam machine running at a velocity of 2500 rpm. The corrosive environments tested were distilled water, 100 ppm NaCl, and 3.5 percent NaCl. Results were compared to the endurance limit in air. An evaluation of the effect of protective coatings on corrosion fatigue was made by comparing the fatigue properties of specimens with coatings to those without.

  20. Creep-fatigue behavior of NiCoCrAlY coated PWA 1480

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Hebsur, M. G.

    1985-01-01

    This study of high-temperature fatigue and creep-fatigue behavior is part of a program to identify the basic features of the effects of temperature, creep, fatigue, and environment on the behavior of a single crystal superalloy, a bulk coating alloy, and a coated alloy system. A system was selected which has had considerable production experience: the Ni-base superalloy, PWA 1480, and the NiCoCrAlY coating, PWA 276. Isothermal behavior was studied first. A series of fatigue and creep fatigue tests of the types commonly designated as pp, cp, pc and cc were conducted. These tests were conducted at various constant total strain ranges. The creep-fatigue cycles employed constant stress dwells at the maximum and/or minimum load. Test results are given.

  1. Improving fatigue strength of welded joints

    NASA Astrophysics Data System (ADS)

    Takamori, Hiroyuki

    One series of fatigue tests was carried out on coverplated bridge girders with small fatigue cracks that had been treated in 1976. The treatment and preconditions were reported in NCHRP Report 206. The Category E' coverplated. beams that were removed from the Yellow Mill Pond Bridge in 1997 had been retrofitted in 1976 by either air hammer peening or GTA remelting the weld toe. Most of the details had small fatigue cracks at the time the retrofit was carried out. No detectable fatigue cracking was observed at the treated coverplate ends after 20 years of service on I-95 and an estimated 56 million truck passages. All beams were tested at a stress range of 69 MPa (10 ksi). Cracks eventually developed from the root of the transverse end welds and propagated through the weld throat and from there into the beam flange via the longitudinal welds. The fatigue resistance of the treated weld toe details was improved to Category C. The one GTA remelted detail that recracked at the weld toe exceeded Category D. The second series of tests was carried out on large scale HPS-485W steel plate girders with as-welded and ultrasonic impact treated (UIT) details. The UIT treatment was applied to the weld toe of transverse stiffeners welded to the web and flanges (Category C details) and to coverplated ends (Category E' details). The as-welded details cracked as expected at their corresponding fatigue resistance. All UIT treated details were improved. The treated transverse stiffeners achieved Category B fatigue resistance. The treated coverplated details achieved Category C. The third series of tests was conducted on large scale HPS-485W steel plate girders with undermatched groove welded details at flange transition. The objectives of using undermatched weld materials compared to the base material is to reduce the potentiality of hydrogen cracking at flange groove welds and to improve the fatigue strength of the welded joints. Fatigue strength of undermatched welded joints was

  2. Effect of mental fatigue on the central nervous system: an electroencephalography study

    PubMed Central

    2012-01-01

    Background Fatigue can be classified as mental and physical depending on its cause, and each type of fatigue has a multi-factorial nature. We examined the effect of mental fatigue on the central nervous system using electroencephalography (EEG) in eighteen healthy male volunteers. Methods After enrollment, subjects were randomly assigned to two groups in a single-blinded, crossover fashion to perform two types of mental fatigue-inducing experiments. Each experiment consisted of four 30-min fatigue-inducing 0- or 2-back test sessions and two evaluation sessions performed just before and after the fatigue-inducing sessions. During the evaluation session, the participants were assessed using EEG. Eleven electrodes were attached to the head skin, from positions F3, Fz, F4, C3, Cz, C4, P3, Pz, P4, O1, and O2. Results In the 2-back test, the beta power density on the Pz electrode and the alpha power densities on the P3 and O2 electrodes were decreased, and the theta power density on the Cz electrode was increased after the fatigue-inducing mental task sessions. In the 0-back test, no electrodes were altered after the fatigue-inducing sessions. Conclusions Different types of mental fatigue produced different kinds of alterations of the spontaneous EEG variables. Our findings provide new perspectives on the neural mechanisms underlying mental fatigue. PMID:22954020

  3. Thermomechanical and bithermal fatigue behavior of cast B1900 + Hf and wrought Haynes 188

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Verrilli, Michael J.; Kalluri, Sreeramesh; Ritzert, Frank J.; Duckert, Rob E.; Holland, Frederic A.

    1991-01-01

    High temperature thermomechanical and bithermal fatigue behavior was investigated for two superalloys: cast nickel-base B1900+Hf and wrought cobalt-base Haynes 188. Experimental results were generated to support development of an advanced thermal fatigue life prediction method. Strain controlled thermomechanical and load-controlled, strain-limited, bithermal fatigue tests were used to determine the fatigue crack initiation and cyclic stress-strain response characteristics of superalloys. Bithermal temperatures of 483 and 871 C were used for B1900+Hf, and 316 and 760 C for Haynes 188. Thermomechanical fatigue tests were conducted by using maximum and minimum temperatures corresponding to those for the bithermal experiments. Lives cover the range from about 10 to 3000 cycles to failure. Isothermal fatigue results obtained previously are also discussed.

  4. Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

    NASA Astrophysics Data System (ADS)

    Safaei, Farinaz; Castorena, Cassie; Kim, Y. Richard

    2016-08-01

    Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder's contribution to mixture fatigue and pavement fatigue cracking performance.

  5. Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

    NASA Astrophysics Data System (ADS)

    Safaei, Farinaz; Castorena, Cassie; Kim, Y. Richard

    2016-04-01

    Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder's contribution to mixture fatigue and pavement fatigue cracking performance.

  6. A Clinically Translatable Mouse Model for Chemotherapy-Related Fatigue

    PubMed Central

    Zombeck, Jonathan A; Fey, Edward G; Lyng, Gregory D; Sonis, Stephen T

    2013-01-01

    Fatigue is a debilitating and pervasive complication of cancer and cancer care. Clinical research investigating potential therapies is hindered by variability in patient histories, different metrics for measuring fatigue, and environmental factors that may affect fatigue. The purpose of this study was to establish an animal model of chemotherapy-related fatigue. Female HSD:ICR mice were treated with doxorubicin (2.5 mg/kg) or saline in 2 cycles (days 1 through 3 and 10 through 12). After treatment, mice were individually housed in cages equipped with running wheels. Open-field activity and motor coordination were examined after each cycle of treatment and after each week of wheel running. In a separate cohort, modafinil (50 mg/kg) was assessed as a potential treatment for fatigue. Doxorubicin administration resulted in greater than 30% less wheel running compared with that of saline controls. Activity differences were specific to wheel running: neither distance traveled in the open field nor motor coordination according to the rotarod test differed between groups. Compared with control values, RBC counts in the doxorubicin group were decreased on days 15 and 22 but recovered to control levels by study completion. Modafinil was efficacious in increasing wheel running in the doxorubicin group. The current results establish an animal model of chemotherapy-related fatigue that recapitulates the physical symptoms of cancer-related fatigue as manifested as decreased voluntary activity. This model is sensitive to pharmaceutical intervention and can be used to screen potential treatments for fatigue. PMID:24326224

  7. Dynamic Docking Test System (DDTS) active table frequency response test results. [Apollo Soyuz Test Project

    NASA Technical Reports Server (NTRS)

    Gates, R. M.

    1974-01-01

    Results are presented of the frequency response test performed on the dynamic docking test system (DDTS) active table. Sinusoidal displacement commands were applied to the table and the dynamic response determined from measured actuator responses and accelerometers mounted to the table and one actuator.

  8. Preliminary metallographic studies of ball fatigue under rolling-contact conditions

    NASA Technical Reports Server (NTRS)

    Bear, H Robert; Butler, Robert H

    1957-01-01

    The metallurgical results produced on balls tested in the rolling-contact fatigue spin rig were studied by metallographic examination. Origin and progression of fatigue failures were observed. These evaluations were made on SAE 52100 and AISI M-1 balls fatigue tested at room temperature (80 F) and 200 to 250 F. Most failures originated subsurface in shear; inclusions, structure changes, and directionalism adversely affected ball fatigue life. Structures in the maximum-shear-stress region of the balls of both materials were stable at room temperature and unstable at 200 to 250 F. Failures were of the same type as those found in full-scale bearings.

  9. Effects of LWR environments on fatigue life of carbon and low-alloy steels

    SciTech Connect

    Chopra, O.K.; Shack, W.J.

    1995-03-01

    SME Boiler and Pressure Vessel Code provides construction of nuclear power plant components. Figure I-90 Appendix I to Section III of the Code specifies fatigue design curves for structural materials. While effects of environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A 106-Gr B carbon steel and A533-Gr B low-alloy steel in water.

  10. Fatigue and Vitamin D Status in Iranian Female Nurses

    PubMed Central

    Alavi, Negin Masoudi; Madani, Mahla; Sadat, Zohre; Kashani, Hamed Haddad; Sharif, Mohammad Reza

    2016-01-01

    Introduction: Given that nurses are among professions with frequent problems of fatigue, and given the nature of their profession that provides little exposure to sunlight and the subsequent deficiency of vitamin D, the present study examined the relation between fatigue and circulating vitamin D levels in female nurses working in Shahid Beheshti Hospital, Kashan, Iran in 2013. Material and Methods: This cross-sectional study was conducted in 200 female nurses working in Shahid Beheshti Hospital. To measure fatigue, fatigue questionnaire containing 9 questions eliciting the subject’s feeling in scales of 1 to 7, getting a possible score of 9 to 63, and Visual Analogue Scale in which nurses specified their fatigue in a band of zero to 10 were used. The 25-hydroxyvitamin D, which is the most important vitamin D metabolite, also was determined. The data was analyzed by SPSS-16. The Pearson’s correlation of coefficients, t-test, and multiple regression analysis were used in this study. Results: The mean fatigue score of nurses was 38.76±12.66 in questionnaire and 5.73±2.12 in Visual Analog Scale. The 89 per cent of nurses suffered from vitamin D deficiency, 9.5 percent of them had normal level and 1.5 per cent had toxicity level of vitamin D. There was a significant relationship between vitamin D level and fatigue scores (P<0.0001), and visual fatigue scores (P<0.0001). According to multivariate regression analysis, vitamin D level accounted for 13 per cent of the fatigue based on data on questionnaire and 18.6 per cent of fatigue according to Visual Analog Scale. Conclusion: High prevalence of fatigue among nurses could be attributed to vitamin D deficiency. PMID:26755458

  11. Estimating mental fatigue based on electroencephalogram and heart rate variability

    NASA Astrophysics Data System (ADS)

    Zhang, Chong; Yu, Xiaolin

    2010-01-01

    The effects of long term mental arithmetic task on psychology are investigated by subjective self-reporting measures and action performance test. Based on electroencephalogram (EEG) and heart rate variability (HRV), the impacts of prolonged cognitive activity on central nervous system and autonomic nervous system are observed and analyzed. Wavelet packet parameters of EEG and power spectral indices of HRV are combined to estimate the change of mental fatigue. Then wavelet packet parameters of EEG which change significantly are extracted as the features of brain activity in different mental fatigue state, support vector machine (SVM) algorithm is applied to differentiate two mental fatigue states. The experimental results show that long term mental arithmetic task induces the mental fatigue. The wavelet packet parameters of EEG and power spectral indices of HRV are strongly correlated with mental fatigue. The predominant activity of autonomic nervous system of subjects turns to the sympathetic activity from parasympathetic activity after the task. Moreover, the slow waves of EEG increase, the fast waves of EEG and the degree of disorder of brain decrease compared with the pre-task. The SVM algorithm can effectively differentiate two mental fatigue states, which achieves the maximum classification accuracy (91%). The SVM algorithm could be a promising tool for the evaluation of mental fatigue. Fatigue, especially mental fatigue, is a common phenomenon in modern life, is a persistent occupational hazard for professional. Mental fatigue is usually accompanied with a sense of weariness, reduced alertness, and reduced mental performance, which would lead the accidents in life, decrease productivity in workplace and harm the health. Therefore, the evaluation of mental fatigue is important for the occupational risk protection, productivity, and occupational health.

  12. Simulation of Fatigue Crack Initiation at Corrosion Pits With EDM Notches

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Newman, John A.; Piascik, Robert S.

    2003-01-01

    Uniaxial fatigue tests were conducted to compare the fatigue life of laboratory produced corrosion pits, similar to those observed in the shuttle main landing gear wheel bolt-hole, and an electro-discharged-machined (EDM) flaw. EDM Jaws are used to simulate corrosion pits during shuttle wheel (dynamometer) testing. The aluminum alloy, (AA 7050) laboratory fatigue tests were conducted to simulate the local stress level contained in the wheel bolt-hole. Under this high local stress condition, the EDM notch produced a fatigue life similar to test specimens containing corrosion pits of similar size. Based on the laboratory fatigue test results, the EDM Jaw (semi-circular disc shaped) produces a local stress state similar to corrosion pits and can be used to simulate a corrosion pit during the shuttle wheel dynamometer tests.

  13. A New Multiaxial High-Cycle Fatigue Criterion Based on the Critical Plane for Ductile and Brittle Materials

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Shang, De-Guang; Wang, Xiao-Wei

    2015-02-01

    An improved high-cycle multiaxial fatigue criterion based on the critical plane was proposed in this paper. The critical plane was defined as the plane of maximum shear stress (MSS) in the proposed multiaxial fatigue criterion, which is different from the traditional critical plane based on the MSS amplitude. The proposed criterion was extended as a fatigue life prediction model that can be applicable for ductile and brittle materials. The fatigue life prediction model based on the proposed high-cycle multiaxial fatigue criterion was validated with experimental results obtained from the test of 7075-T651 aluminum alloy and some references.

  14. Fatigue life of laser cut metals

    NASA Technical Reports Server (NTRS)

    Martin, M. R.

    1986-01-01

    Fatigue tests were conducted to determine the actual reduction in fatigue life due to weight removal for balancing by: hand grinding, low power (20 watt) Nd:glass laser, and high power (400 watt) Nd:YAG laser.

  15. Initial test results using the GEOS-3 engineering model altimeter

    NASA Technical Reports Server (NTRS)

    Hayne, G. S.; Clary, J. B.

    1977-01-01

    Data from a series of experimental tests run on the engineering model of the GEOS 3 radar altimeter using the Test and Measurement System (TAMS) designed for preflight testing of the radar altimeter are presented. These tests were conducted as a means of preparing and checking out a detailed test procedure to be used in running similar tests on the GEOS 3 protoflight model altimeter systems. The test procedures and results are also included.

  16. Functional assessment of chronic illness therapy—the fatigue scale exhibits stronger associations with clinical parameters in chronic dialysis patients compared to other fatigue-assessing instruments

    PubMed Central

    Chao, Chia-Ter; Huang, Jenq-Wen

    2016-01-01

    Background. Patients with end-stage renal disease (ESRD) have a high symptom burden, among which fatigue is highly prevalent. Many fatigue-assessing instruments exist, but comparisons among instruments in this patient population have yet to be investigated. Methods. ESRD patients under chronic hemodialysis were prospectively enrolled and seven types of fatigue instruments were administered: Brief Fatigue Inventory (BFI), Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-F), Fatigue Severity Scale (FSS), Lee Fatigue Scale (LFS), Fatigue Questionnaire (FQ), Fatigue Symptom Inventory (FSI), and Short-Form 36-Vitality (SF36-V). Using these instruments, we investigated the correlation between fatigue severity and clinical/biochemical parameters, including demographic/comorbidity profile, dialysis-related complications, and frailty severity. We used regression analysis with serum albumin and frailty severity as the dependent variables to investigate the independent correlations. Results. A total of 46 ESRD patients were enrolled (average age of 67 ± 11.6 years), and 50% of them had type 2 diabetes mellitus. Results from the seven tested instruments showed high correlation with each other. We found that the fatigue severity by FACIT-F was significantly associated with age (p = 0.03), serum albumin (p = 0.003) and creatinine (p = 0.02) levels, while SF36-V scores were also significantly associated with age (p = 0.02) and serum creatinine levels (p = 0.04). However, the fatigue severity measured by the FSS, FSI, FQ, BFI, and LFS did not exhibit these associations. Moreover, regression analysis showed that only FACIT-F scores were independently associated with serum albumin levels and frailty severity in ESRD patients. Conclusion. Among the seven fatigue-assessing instruments, only the FACIT-F yielded results that demonstrated significant and independent associations with important outcome-related features in ESRD patients. PMID:26998414

  17. Thermal fatigue of beryllium

    SciTech Connect

    Deksnis, E.; Ciric, D.; Falter, H.

    1995-09-01

    Thermal fatigue life of S65c beryllium castellated to a geometry 6 x 6 x (8-10)mm deep has been tested for steady heat fluxes of 3 MW/m{sup 2} to 5 MW/m{sup 2} and under pulsed heat fluxes (10-20 MW/m{sup 2}) for which the time averaged heat flux is 5 MW/m{sup 2}. These tests were carried out in the JET neutral beam test facility A test sequence with peak surface temperatures {le} 600{degrees}C produced no visible fatigue cracks. In the second series of tests, with T{sub max} {le} 750{degrees}C evidence for fatigue appeared after a minimum of 1350 stress cycles. These fatigue data are discussed in view of the observed lack of thermal fatigue in JET plasma operations with beryllium PFC. JET experience with S65b and S65c is reviewed; recent operations with {Phi} = 25 MW/m{sup 2} and sustained melting/resolidification are also presented. The need for a failure criterion for finite element analyses of Be PFC lifetimes is discussed.

  18. Determining equivalent damage loading for full-scale wind turbine blade fatigue tests

    SciTech Connect

    Freebury, G.; Musial, W.

    2000-03-13

    This paper describes a simplified method for converting wind turbine rotor design loads into equivalent-damage, constant-amplitude loads and load ratios for both flap and lead-lag directions. It is an iterative method that was developed at the National Renewable Energy Laboratory (NREL) using Palmgren-Miner's linear damage principles. The general method is unique because it does not presume that any information about the materials or blade structural properties is precisely known. According to this method, the loads are never converted to stresses. Instead, a family of M-N curves (moment vs. cycles) is defined with reasonable boundaries for load-amplitude and slope. An optimization program iterates and converges on the constant amplitude test load and load ratio that minimizes the sensitivity to the range of M-N curves for each blade section. The authors constrained the general method to match the NedWind 25 design condition for the Standards, Measurements, and Testing (SMT) blade testing pro gram. SMT participants agreed to use the fixed S-N slope of m = 10 from the original design to produce consistent test-loads among the laboratories. Unconstrained, the general method suggests that slightly higher test loads should be used for the NedWind 25 blade design spectrum. NedWind 25 blade test loads were computed for lead-lag and flap under single-axis and two-axis loading.

  19. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

    PubMed Central

    Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture. PMID:25050406

  20. Evaluation of fatigue life of CRM-reinforced SMA and its relationship to dynamic stiffness.

    PubMed

    Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati; Koting, Suhana

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture. PMID:25050406