WorldWideScience

Sample records for thermal fatigue caused

  1. Simple Theory of Thermal Fatigue Caused by RF Pulse Heating

    CERN Document Server

    Kuzikov, S

    2004-01-01

    The projects of electron-positron linear colliders imply that accelerating structures and other RF components will undergo action of extremely high RF fields. Except for breakdown threat there is an effect of the damage due to multi-pulse mechanical stress caused by Ohmic heating of the skin layer. A new theory of the thermal fatigue is considered. The theory is based on consideration of the quasi-elastic interaction between neighbor grains of metal due to the expansion of the thermal skin-layer. The developed theory predicts a total number of the RF pulses needed for surface degradation in dependence on temperature rise, pulse duration, and average temperature. The unknown coefficients in the final formula were found, using experimental data obtained at 11.4 GHz for the copper. In order to study the thermal fatigue at higher frequencies and to compare experimental and theoretical results, the experimental investigation of degradation of the copper cavity exposed to 30 GHz radiation is carried out now, basing...

  2. Thermal Acoustic Fatigue Apparatus

    Data.gov (United States)

    Federal Laboratory Consortium — The Thermal Acoustic Fatigue Apparatus (TAFA) is a progressive wave tube test facility that is used to test structures for dynamic response and sonic fatigue due to...

  3. Thermal fatigue of beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Deksnis, E.; Ciric, D.; Falter, H. [JET Joint undertaking, Abingdon (United Kingdom)] [and others

    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.

  4. Muscle Deoxygenation Causes Muscle Fatigue

    Science.gov (United States)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D.

    1999-01-01

    Muscle fatigue is a common musculoskeletal disorder in the work place, and may be a harbinger for more disabling cumulative trauma disorders. Although the cause of fatigue is multifactorial, reduced blood flow and muscle oxygenation may be the primary factor in causing muscle fatigue during low intensity muscle exertion. Muscle fatigue is defined as a reduction in muscle force production, and also occurs among astronauts who are subjected to postural constraints while performing lengthy, repetitive tasks. The objectives of this research are to: 1) develop an objective tool to study the role of decreased muscle oxygenation on muscle force production, and 2) to evaluate muscle fatigue during prolonged glovebox work.

  5. Ischemia causes muscle fatigue

    Science.gov (United States)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D. M.

    2001-01-01

    The purpose of this investigation was to determine whether ischemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TO2) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation (1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 +/- 9.8 mm Hg) and systolic (106 +/- 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 min, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline (100% TO2) to 99 +/- 1.2% (SEM), 96 +/- 1.9%, 93 +/- 2.8%, 90 +/- 2.5%, and 86 +/- 2.7%, and mean twitch force decreased from resting baseline (100% force) to 99 +/- 0.7% (SEM), 96 +/- 2.7%, 93 +/- 3.1%, 88 +/- 3.2%, and 86 +/- 2.6%. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower (P muscle oxygenation (r = 0.78, P muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

  6. Fatigue in traffic : causes and effects.

    NARCIS (Netherlands)

    2006-01-01

    The role of fatigue must not be underestimated when studying the causes of crashes. Crashes in which driver fatigue plays a role are not only a matter of having spent too long behind the wheel; fatigue can also be caused by too little sleep, stress, or the time of the day. According to a

  7. Does Corruption Cause Aid Fatigue?

    DEFF Research Database (Denmark)

    Bauhr, Monika; Charron, Nicholas; Nasiritousi, Naghmeh

    2013-01-01

    Does perceived corruption in recipient countries reduce support for foreign aid in donor countries? This under-explored yet salient question is examined using the 2009 Eurobarometer survey for the 27 EU countries. We suggest that perceived corruption can cause aid fatigue but that this relationship...... is highly contextualized. The results show that perceptions about corruption in developing countries reduce overall support for aid among respondents in donor countries. However, this effect is mitigated by country and contextual-level effects and different understandings of what we call the “aid-corruption...... paradox,” namely that the need for foreign aid is often the greatest in corrupt environments. Three different dynamics of the aid-corruption paradox influence support for aid: moral, pragmatic, and strategic understandings. In EU-15 countries, the effect of perceived corruption in recipient states on aid...

  8. Thermal fatigue cracking of die-casting dies

    Directory of Open Access Journals (Sweden)

    Thermal fatigue cracking of die-casting dies

    2010-01-01

    Full Text Available Die-casting dies are exposed to high thermal and mechanical loads. Thermal fatigue cracking of dies due to thermal cycling may importantly shorten the life-time of the die. Cracks degrade the surface quality of dies and consequently the surface of castings. In this study, thermal fatigue cracking of dies was analyzed during the process of die casting aluminium alloys. During the process cracks were observed and measured and their location and size were determined. Thermal and mechanical loads cause high local stresses and consequently surface cracks. First cracks occur as early as after 2000 cycles and propagate progressively with cycles.

  9. Thermal fatigue of electrical fuses

    Directory of Open Access Journals (Sweden)

    Gelet Jean-Louis

    2014-06-01

    Full Text Available Electric Fuses have to respect different national or international standards such as IEC (International Electro-technical Commission 269. These standards define the characteristics of the fuses and describe the tests to be run in order to check fuse's ability to take up their main functions, i.e. current-conduction and operation under overloads and short-circuits. But fuses never carry current neither operate under standardized conditions. For example, rated current is evaluated under specified ambient temperature, without cooling air-flow, and with 1 meter-long connection-cables on both sides. In the field, temperature can reach up 80∘C, with or without air-flow and connection-parts are much more shorter. An issue is that current is never constant, often being cyclingly applied; equipments are frequently in use during the day and stopped in the night. ON-time and OFF-time generate alternative heating, then alternative stresses leading to thermal fatigue. MERSEN run many tests along the years, allowing to develop a method for choosing right fuses for each application. As a result, fuses don't melt unexpectedly in the field, but the method is supposed to be conservative and does not permit to get a better understanding of the phenomena neither an improvement of the products. The paper presents some specific ageing-tests run on conductive elements and tries to establish a correspondence between these tests and others carried out on complete fuses. Tests have been run on silver and copper, but their principle could be interesting for any structural material, especially because it underlines crack-opening.

  10. Compassion Fatigue: Description, Causes and Prevention

    Directory of Open Access Journals (Sweden)

    Duygu Hicdurmaz

    2015-09-01

    Full Text Available Nowadays, paralel to prolonging life time, illness experience can change life of everyone who takes care of the individual directly or indirectly. Prolonging of this time for patient, simultaneously causes prolonging of the time for the care and treatment providers and them to be with the patient more during illness and suffering process. Caring for chronically ill individuals by getting aware of that they won't be able to recover completely, causes them to experience various problems called compassion fatigue. Compasion fatigue is described as the natural feeling and behaviour arising from knowing the traumatizing events which a significant other has experienced; as the stress arising from helping or wanting to help a traumatized individual. The aim of this review is to describe compassion fatigue, explain the concepts with which it is related, and by this way to increase the awareness of professionals who work in helping professions. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2015; 7(3.000: 295-303

  11. Laser thermal shock and fatigue testing system

    Science.gov (United States)

    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

  12. SUSCEPTOBILITY TO THERMAL FATIGUE OF CLOSED DIE HOT FORGING DIES

    Directory of Open Access Journals (Sweden)

    Frederico de Castro Magalhães

    2014-06-01

    Full Text Available Hot forging dies providing high productive performance reduce production costs. The lifetime of the dies is expressed by the number of forgings (production cycle produced before being rejected by the presence of a failure mechanism, associated with unacceptable dimensions and or geometry of the end product or even breakage of the dies. One of the failure mechanisms of hot forging dies is thermal fatigue, caused by cyclic heating and cooling. A subroutine, based on the work of Maim and Norstrom [1], was developed for the DEFORM 2D numerical software, using the finite element method, in order to predict die regions susceptible to thermal fatigue. The use of adequate coefficients for the description of the heat transfer phenomena allowed the validation of the proposed subroutine.

  13. Fatigue

    Science.gov (United States)

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  14. Stochastic modeling of thermal fatigue crack growth

    CERN Document Server

    Radu, Vasile

    2015-01-01

    The book describes a systematic stochastic modeling approach for assessing thermal-fatigue crack-growth in mixing tees, based on the power spectral density of temperature fluctuation at the inner pipe surface. It shows the development of a frequency-temperature response function in the framework of single-input, single-output (SISO) methodology from random noise/signal theory under sinusoidal input. The frequency response of stress intensity factor (SIF) is obtained by a polynomial fitting procedure of thermal stress profiles at various instants of time. The method, which takes into account the variability of material properties, and has been implemented in a real-world application, estimates the probabilities of failure by considering a limit state function and Monte Carlo analysis, which are based on the proposed stochastic model. Written in a comprehensive and accessible style, this book presents a new and effective method for assessing thermal fatigue crack, and it is intended as a concise and practice-or...

  15. Thermal fatigue due to stratification and thermal shock loading of piping

    Energy Technology Data Exchange (ETDEWEB)

    Schuler, X.; Herter, K.H. [Materials Testing Inst. (MPA) Univ. of Stuttgart, Stuttgart (Germany)

    2004-07-01

    Most of the fatigue relevant stresses in piping systems are caused by thermal loading. The difference between the density of the fluid caused by the temperature gradient from bottom to top of the pipe cross section combined with low flow rates can result in thermal stratification in the horizontal portions of a piping system. The hot and cold fluid levels of the stratified flow conditions are separated by an interface or mixing layer. On the other hand high flow rates can cause a temperature gradient in pipe longitudinal direction (jump of temperature) and result in a thermal shock loading on the inside pipe surface constant throughout the pipe cross section. These loading conditions impact the secondary stress and the fatigue usage analysis typically performed for piping components by equations in the technical codes. Thermal stratification in piping system causes a circumferentially varying temperature distribution in the pipe wall resulting in local through wall axial stresses and global bending stresses in the piping system. Maximum local thermal stress is found when a thin interface (mixing) layer occurs in the upper or lower parts of the pipe cross section. Maximum global thermal bending stress is found when a thin interface layer occurs in the middle of the pipe cross section. (orig.)

  16. Thermal emission in fatigue described by power laws

    Directory of Open Access Journals (Sweden)

    Gallinatti A.E.

    2010-06-01

    Full Text Available In the present work, a theoretical model proposed by the literature and focused on the relationship between microplasticizations thermal behaviour and fatigue scatter is analysed and applied to fatigue test results of standard and notched steel specimens. The same experimental data are subjected to the TCM (Two Curves Method thermographic elaboration technique, in order to quickly evaluate fatigue limit values. TCM method has been modified, aiming at interpolating thermal data referred to the region of loads upper than fatigue limit with a non linear regression law having the same mathematical structure of the theoretical model equations (power laws.

  17. A review of typical thermal fatigue failure models for solder joints of electronic components

    Science.gov (United States)

    Li, Xiaoyan; Sun, Ruifeng; Wang, Yongdong

    2017-09-01

    For electronic components, cyclic plastic strain makes it easier to accumulate fatigue damage than elastic strain. When the solder joints undertake thermal expansion or cold contraction, different thermal strain of the electronic component and its corresponding substrate is caused by the different coefficient of thermal expansion of the electronic component and its corresponding substrate, leading to the phenomenon of stress concentration. So repeatedly, cracks began to sprout and gradually extend [1]. In this paper, the typical thermal fatigue failure models of solder joints of electronic components are classified and the methods of obtaining the parameters in the model are summarized based on domestic and foreign literature research.

  18. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Possible Causes

    Science.gov (United States)

    ... Controls Search Form Controls Cancel Submit Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Note: Javascript is disabled or is not supported ... have not yet identified what causes myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). It is possible that ME/CFS ...

  19. Thermal Fatigue of Die-Casting Dies: An Overview

    Directory of Open Access Journals (Sweden)

    Abdulhadi Hassan A.

    2016-01-01

    Full Text Available Coupled studies by experimental and numerical simulations are necessary for an increased understanding of the material behaviour as related to the interaction between the thermal and mechanical conditions. This paper focus on the mechanisms of thermal fatigue in the failure of dies and cores used in the die casting of aluminum alloys. The thermal fatigue resistance is expressed by two crack parameters which are the average maximum crack and the average cracked area. Samples of various types of H13 steel were compared with a standard H13 steel by testing under identical thermal fatigue cycles. To determine the thermal constraint developed in the sample during the test, a finite difference technique was used to obtain the temperature distribution, based on temperature measurements at the boundaries. The resulting stresses and strains were computed, and the strain calculated at the edge or weakest point of the sample was used to correlate the number of cycles to crack initiation. As the strain at the edge increased, the number of cycles to failure decreased. The influence of various factors on thermal fatigue behavior was studied including austenitizing temperature, surface condition, stress relieving, casting, vacuum melting, and resulfurization. The thermal fatigue resistance improved as the austenitizing temperature increased from 1750 to 2050ºF.

  20. Experimental investigation of high cycle thermal fatigue in a T-junction piping system

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, P. Karthick; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    High cycle thermal fatigue damage of structure in the vicinity of T-junction piping systems in nuclear power plants is of importance. Mixing of coolant streams at significant temperature differences causes thermal fluctuations near piping wall leading to gradual thermal degradation. Flow mixing in a T-junction is performed. The determined factors result in bending stresses being imposed on the piping system ('Banana effect').

  1. Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

    Directory of Open Access Journals (Sweden)

    Jie Chen

    2014-01-01

    Full Text Available Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. There were some studies on the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully developed to allow performing thermal-mechanical fatigue (TMF test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

  2. Causes and consequences of fatigue in rheumatoid arthritis.

    Science.gov (United States)

    Katz, Patricia

    2017-05-01

    To review current information on the causes, treatments, and consequences of fatigue in rheumatoid arthritis. Disease activity (inflammation, pain, joint symptoms) is associated with greater fatigue. However, disease activity per se accounts for only a small portion of fatigue, and rheumatoid arthritis medications that reduce disease activity have small effects on fatigue. Instead, factors outside the direct effects of rheumatoid arthritis, such as obesity, physical inactivity, sleep disturbance, and depression, explain the majority of variation in fatigue. Some of these factors may be indirect effects of disease (e.g. pain can lead to sleep disturbance). Rheumatoid arthritis has significant effects on the quality of life of individuals with rheumatoid arthritis. The most effective approaches to reducing rheumatoid arthritis fatigue appear to be behavioral, such as increasing physical activity, or cognitive, such as cognitive behavioral interventions. Fatigue in rheumatoid arthritis appears to be largely because of factors outside the direct effects of the disease, such as behavioral and psychological factors. In spite of the tremendous impact of fatigue on patient health and quality of life, effective treatments remain elusive, but existing data show that behavioral and cognitive approaches may be most effective.

  3. Vacuum thermal-mechanical fatigue behavior of two iron-base alloys

    Science.gov (United States)

    Sheffler, K. D.

    1976-01-01

    The present study extends the concept of in-phase grain boundary ratcheting to two iron-base alloys (Type 304 stainless steel and A286 alloy) and provides a clearer interpretation of out-of-phase grain boundary ratcheting effects observed in the A286 alloy which does not exhibit geometric instability. Elevated-temperature low-cycle thermal-mechanical fatigue tests in an ion-pumped ultrahigh vacuum chamber revealed significant effects of frequency and combined temperature-strain cycling on fatigue life. In-phase thermal cycling (tension at high temperature and compression at low temperature) caused large life reductions in both materials due to grain boundary cavitation caused by unreversed grain boundary sliding (grain boundary ratcheting). Out-of-phase thermal cycling (tension at low temperature and compression at high temperature) also caused large cyclic life reductions in both materials. In the A286 alloy, out-of-phase life reductions are attributed to compressive ratcheting.

  4. The Effect of Load Magnitude on Fatigue Life and Thermal Behavior of Notched Fatigue Specimen

    Directory of Open Access Journals (Sweden)

    Laith Hussain Al Najar

    2017-11-01

    Full Text Available Fatigue failure is an important phenomenon that occurred in the mechanical and structural systems. Furthermore, the failure due to fatigue load causes losing in that system. So many researches studying the fatigue behavior and improving the design of mechanical and structural systems in order to increase the fatigue resistance of these systems.  In this work, the effects of notch position and load magnitude on fatigue behavior were studied. In order to study the fatigue life of the test specimens due to make V- notched, the rotating cantilever beam samples were used. Also, the temperature distribution along testing specimens was monitoring of IR camera during the fatigue tests. Numerical model has been done by using ANSYS Workbench 15.0.  The comparison between experimental and numerical results was made, also the hardness of the fractured surfaces was measured. The results show that, the fatigue life of the test specimens can be increased by making a notch in the appropriate position. Also, there is a similarity between experimental and numerical results. IR camera gave a good expectance to the fracture position from changing in temperature distribution along the test specimens. Finally, the area of sudden fracture of the fractured surfaces reduced directly with load magnitude and inversely with notch shifting away from edge region.

  5. Microstructural analysis of thermal fatigue damage in 316L pipes

    OpenAIRE

    Gonzalez Sanchez, Sergio; Ruiz, Ana; Nilsson, Karl-Fredrik

    2013-01-01

    This report summarizes the data and main conclusions derived from microstructural characterisation of 316L pipes subjected to thermal fatigue with a peak temperature of 550°C. TOFD measurements are compared with measured crack depths from cut segments, and fracture mode and corrosion have been assessed by SEM and EDX, respectively.

  6. Hydrogen enhanced thermal fatigue of y-titanium aluminide

    NARCIS (Netherlands)

    Dunfee, William; Gao, Ming; Wei, Robert P.; Wei, W.

    1995-01-01

    A study of hydrogen enhanced thermal fatigue cracking was carried out for a gamma-based Ti-48Al-2Cr alloy by cycling between room temperature and 750 or 900 °C. The results showed that hydrogen can severely attack the gamma alloy, with resulting lifetimes as low as three cycles, while no failures

  7. Influence of grain orientation on evolution of surface features in fatigued polycrystalline copper: a comparison of thermal and uniaxial mechanical fatigue results

    CERN Document Server

    Aicheler, M

    2010-01-01

    Surface state plays a major role in the crack nucleation process of pure metals in the High-Cycle-Fatigue (HCF) as well as in the Ultra-High-Cycle-Fatigue (UHCF) regime. Therefore, in studies dealing with HCF or UHCF, special attention is paid to the evolution of surface degradation during fatigue life. The accelerating structures of the future Compact Linear Collider (CLIC) under study at CERN will be submitted to a high number of thermal-mechanical fatigue cycles, arising from Radio Frequency (RF) induced eddy currents, causing local superficial cyclic heating. The number of cycles during the foreseen lifetime of CLIC reaches 2x10(11). Fatigue may limit the lifetime of CLIC structures. In order to assess the effects of superficial fatigue, specific tests are defined and performed on polycrystalline Oxygen Free Electronic (OFE) grade Copper, a candidate material for the structures. Surface degradation depends on the orientation of near-surface grains. Copper samples thermally fatigued in two different fatigu...

  8. Chronic Fatigue Syndrome: Searching for the Cause and Treatment.

    Science.gov (United States)

    Eichner, Edward R.

    1989-01-01

    Chronic fatigue syndrome became known nationally in l985 with a pseudoepidemic in a Nevada resort community. Initially and erroneously linked to the Epstein-Barr virus, the cause of this puzzling syndrome and the mind-body connection are areas of controversy and research. (Author/SM)

  9. Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures

    CERN Document Server

    Heikkinen, Samuli; Wuensch, Walter

    2010-01-01

    In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

  10. Thermal Fatigue of Cast and Hot-Pressed Lead-Antimony-Silver-Tellurium (LAST) Thermoelectric Materials

    Science.gov (United States)

    Ni, Jennifer E.; Case, Eldon D.

    2013-07-01

    Lead-antimony-silver-tellurium (LAST) thermoelectric materials are candidates for waste-heat recovery applications. However, rapid heating and cooling (thermal shock) imposes thermomechanical stresses that can cause microcracking. Waste-heat recovery applications involve thermal fatigue, in which a series of hundreds or thousands of individual thermal shock events can lead to accumulation of microcrack damage in brittle thermoelectrics such as LAST. Microcracking in turn leads to a decrease in transport properties, such as electrical conductivity and thermal conductivity, and mechanical properties, including elastic modulus and strength. Thus, microcracking can affect both thermoelectric performance and mechanical integrity. In this study, LAST specimens were rapidly cooled (quenched) into a fluid (water or silicone oil) in order to compare the results with the vast majority of thermal shock studies of brittle materials that are quenched in a similar manner. Decreases in elastic modulus, E, with accumulating microcrack damage were measured using resonant ultrasound spectroscopy (RUS). The evolution of thermal fatigue damage observed in this study is also described well by an equation that successfully describes thermal fatigue damage in a variety of brittle materials.

  11. Thermal fatigue as the origin of regolith on small asteroids.

    Science.gov (United States)

    Delbo, Marco; Libourel, Guy; Wilkerson, Justin; Murdoch, Naomi; Michel, Patrick; Ramesh, K T; Ganino, Clément; Verati, Chrystele; Marchi, Simone

    2014-04-10

    Space missions and thermal infrared observations have shown that small asteroids (kilometre-sized or smaller) are covered by a layer of centimetre-sized or smaller particles, which constitute the regolith. Regolith generation has traditionally been attributed to the fall back of impact ejecta and by the break-up of boulders by micrometeoroid impact. Laboratory experiments and impact models, however, show that crater ejecta velocities are typically greater than several tens of centimetres per second, which corresponds to the gravitational escape velocity of kilometre-sized asteroids. Therefore, impact debris cannot be the main source of regolith on small asteroids. Here we report that thermal fatigue, a mechanism of rock weathering and fragmentation with no subsequent ejection, is the dominant process governing regolith generation on small asteroids. We find that thermal fragmentation induced by the diurnal temperature variations breaks up rocks larger than a few centimetres more quickly than do micrometeoroid impacts. Because thermal fragmentation is independent of asteroid size, this process can also contribute to regolith production on larger asteroids. Production of fresh regolith originating in thermal fatigue fragmentation may be an important process for the rejuvenation of the surfaces of near-Earth asteroids, and may explain the observed lack of low-perihelion, carbonaceous, near-Earth asteroids.

  12. Behaviour of Ti-doped CFCs under thermal fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Centeno, A. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Pintsuk, G.; Linke, J. [Forschungszentrum Juelich GmbH, EURATOM Association, 52425 Juelich (Germany); Gualco, C. [Ansaldo Energia, I-16152 Genoa (Italy); Blanco, C., E-mail: clara@incar.csic.es [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Santamaria, R.; Granda, M.; Menendez, R. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain)

    2011-01-15

    In spite of the remarkable progress in the design of in-vessel components for the divertor of the first International Thermonuclear Experimental Reactor (ITER), a great effort is still put into the development of manufacturing technologies for carbon armour with improved properties. Newly developed 3D titanium-doped carbon fibre reinforced composites and their corresponding undoped counterparts were brazed to a CuCrZr heat sink to produce actively cooled flat tile mock-ups. By exposing the mock-ups to thermal fatigue tests in an electron beam test facility, the material behaviour and the brazing between the individual constituents in the mock-up was qualified. The mock-ups with titanium-doped CFCs exhibited a significantly improved thermal fatigue resistance compared with those undoped materials. The comparison of these mock-ups with those produced using pristine NB31, one of the reference materials as plasma facing material for ITER, showed almost identical results, indicating the high potential of Ti-doped CFCs due to their improved thermal shock resistance.

  13. Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

  14. Using lamb waves tomonitor moisture absorption thermally fatigues composite laminates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Sun; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-06-15

    Nondestructive evaluation for material health monitoring is important in aerospace industries. Composite laminates are exposed to heat cyclic loading and humid environment depending on flight conditions. Cyclic heat loading and moisture absorption may lead to material degradation such as matrix breaking, debonding, and delamination. In this paper, the moisture absorption ratio was investigated by measuring the Lamb wave velocity. The composite laminates were manufactured and subjected to different thermal aging cycles and moisture absorption. For various conditions of these cycles, not only changes in weight and also ultrasonic wave velocity were measured, and the Lamb wave velocity at various levels of moisture on a carbon-epoxy plate was investigated. Results from the experiment show a linear correlation between moisture absorption ratio and Lamb wave velocity at different thermal fatigue stages. The presented method can be applied as an alternative solution in the online monitoring of composite laminate moisture levels in commercial flights.

  15. Thermal Fatigue Limitations of Continuous Fiber Metal Matrix Composites

    Science.gov (United States)

    Halford, Gary R.; Arya, Vinod K.

    1997-01-01

    The potential structural benefits of unidirectional, continuous-fiber, metal matrix composites (MMC's) are legendary. When compared to their monolithic matrices, MMC's possess superior properties such as higher stiffness and tensile strength, and lower coefficient of thermal expansion in the direction of the reinforcing fibers. As an added bonus, the MMC density will be lower if the fibers are less dense than the matrix matErial they replace. The potential has been demonstrated unequivocally both analytically and experimentally, especially at ambient temperatures. Successes prompted heavily-funded National efforts within the United States (USAF and NASA) and elsewhere to extend the promise of MMC's into the temperature regime wherein creep, stress relaxation, oxidation, and thermal fatigue damage mechanisms lurk. This is the very regime for which alternative high-temperature materials are becoming mandatory, since further enhancement of state- of-the-art monolithic alloys is rapidly approaching a point of diminishing returns.

  16. Thermal fatigue appears to be more damaging than uniaxial isothermal fatigue for the austentic stainless steels, and application of multiaxial fatigue criteria

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, Antoine; Gourdin, Cedric [DM2S/SEMT/LISN, Gif sur Yvette (France); Vincent, Ludovic [DMN/SRMA/LCD, Gif sur Yvette (France)

    2009-07-01

    For nuclear reactor components, uniaxial isothermal fatigue curves are used to estimate the crack initiation under thermal fatigue. However, such approach would be not sufficient in some cases where cracking was observed. To investigate differences between uniaxial and thermal fatigue damage, tests have been carried out at CEA using the thermal fatigue devices SPLASH and FAT3D: a bi-dimensional (2-D) loading status is obtained in SPLASH, whereas a tri-dimensional (3-D) loading status is obtained in FAT3D. All the analysed tests clearly show that crack initiation in thermal fatigue is faster than in uniaxial isothermal fatigue conditions: for identical levels of strain, the number of cycles required to achieve crack initiation is significantly lower. The enhanced damaging effect probably results from a pure mechanical origin: a nearly perfect biaxial state corresponds to an increased hydrostatic stress. Consequently, multiaxial fatigue criteria must be applied. The Zamrik's strain criterion and the energy criterion proposed by Ecole Polytechnique provide the best estimations. In that framework, the proposed new method coupling both RCC-MR strain estimations and Zamrik's criterion appears to be more promising for the designer. (orig.)

  17. Research and development studies for predicting the thermal fatigue; Etudes de R and D pour la prediction de la fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Moulin, D.; Garnier, J.; Fissolo, A.; Lejeail, Y. [CEA, 75 - Paris (France); Stephan, J.M.; Moinereau, D.; Masson, J. [Electricite de France, Les Renardieres, 77 - Moret sur Loing (France). Direction des Etudes et Recherches

    2001-07-01

    This paper presents some studies in development or realized in the EDF and CEA laboratories, concerning the thermal fatigue damage in nuclear reactor components. The first part presents the basic principles and the methods of lifetime prediction. The second part gives some examples on sodium loop, water loop, welded junctions resistance to thermal fatigue and tests on fatigue specimen. (A.L.B.)

  18. How Thermal Fatigue Cycles Change the Rheological Behavior of Polymer Modified Bitumen?

    NARCIS (Netherlands)

    Glaoui, B.; Merbouh, M.; Van de Ven, M.F.C.; Chailleux, E.; Youcefi, A.

    2013-01-01

    The paper deals with the problem of thermal fatigue cycles phenomenon, which affects the performance of flexible pavement. The purpose of the paper is to extent the knowledge on the rheology of polymer modified bitumen which was affected by cycles of thermal fatigue. The aim of this research is to

  19. Thermal Fatigue Behavior of Air-Plasma Sprayed Thermal Barrier Coating with Bond Coat Species in Cyclic Thermal Exposure

    Directory of Open Access Journals (Sweden)

    Ungyu Paik

    2013-08-01

    Full Text Available The effects of the bond coat species on the delamination or fracture behavior in thermal barrier coatings (TBCs was investigated using the yclic thermal fatigue and thermal-shock tests. The interface microstructures of each TBC showed a good condition without cracking or delamination after flame thermal fatigue (FTF for 1429 cycles. The TBC with the bond coat prepared by the air-plasma spray (APS method showed a good condition at the interface between the top and bond coats after cyclic furnace thermal fatigue (CFTF for 1429 cycles, whereas the TBCs with the bond coats prepared by the high-velocity oxygen fuel (HVOF and low-pressure plasma spray (LPPS methods showed a partial cracking (and/or delamination and a delamination after 780 cycles, respectively. The TBCs with the bond coats prepared by the APS, HVOF and LPPS methods were fully delaminated (>50% after 159, 36, and 46 cycles, respectively, during the thermal-shock tests. The TGO thickness in the TBCs was strongly dependent on the both exposure time and temperature difference tested. The hardness values were found to be increased only after the CFTF, and the TBC with the bond coat prepared by the APS showed the highest adhesive strength before and after the FTF.

  20. Effects of carbon content on high-temperature mechanical and thermal fatigue properties of high-boron austenitic steels

    Directory of Open Access Journals (Sweden)

    Xiang Chen

    2016-01-01

    Full Text Available High-temperature mechanical properties of high-boron austenitic steels (HBASs were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239 (0.19wt.% C to 302 (0.29wt.% C and 312 HV (0.37wt.% C; the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests (performed for 300 cycles from room temperature to 800 °C indicate that the degree of thermal fatigue of the HBAS with 0.29wt.% C (rating of 2–3 is superior to those of the alloys with 0.19wt.% (rating of 4–5 and 0.37wt.% (rating of 3–4 carbon. The main cause of this difference is the ready precipitation of M23(C,B6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.

  1. Environmental Assisted Fatigue Evaluation of Direct Vessel Injection Piping Considering Thermal Stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taesoon; Lee, Dohwan [KHNP CRI, Daejeon (Korea, Republic of)

    2016-10-15

    As the environmentally assisted fatigue (EAF) due to the primary water conditions is to be a critical issue, the fatigue evaluation for the components and pipes exposed to light water reactor coolant conditions has become increasingly important. Therefore, many studies to evaluate the fatigue life of the components and pipes in LWR coolant environments on fatigue life of materials have been conducted. Among many components and pipes of nuclear power plants, the direct vessel injection piping is known to one of the most vulnerable pipe systems because of thermal stratification occurred in that systems. Thermal stratification occurs because the density of water changes significantly with temperature. In this study, fatigue analysis for DVI piping using finite element analysis has been conducted and those results showed that the results met design conditions related with the environmental fatigue evaluation of safety class 1 pipes in nuclear power plants. Structural and fatigue integrity for the DVI piping system that thermal stratification occurred during the plant operation has conducted. First of all, thermal distribution of the piping system is calculated by computational fluid dynamic analysis to analyze the structural integrity of that piping system. And the fatigue life evaluation considering environmental effects was carried out. Our results showed that the DVI piping system had enough structural integrity and fatigue life during the design lifetime of 60 years.

  2. Root cause analysis of thermal sleeve separation

    Energy Technology Data Exchange (ETDEWEB)

    Jo, J. C.; Jhung, M. J.; Yu, S. O.; Kim, H. J.; Yune, Y. K.; Park, J. Y

    2006-01-15

    Thermal sleeves in the shape of thin wall cylinder seated inside the nozzle part of each Safety Injection (SI) line at Pressurized Water Reactors (PWRs) have such functions as prevention and relief of potential excessive transient thermal stress in the wall of SI line nozzle part which is initially heated up with hot water flowing in the primary coolant piping system when cold water is injected into the system through the SI nozzles during the SI operation mode. Recently, mechanical failures that the sleeves were separated from the SI branch pipe and fell into the connected cold leg main pipe occurred in sequence at some typical PWR plants in Korea. To find out the root cause of thermal sleeve breakaway failures, the flow situation in the junction of primary coolant main pipe and SI branch pipe, and the vibration modal characteristics of the thermal sleeve are investigated in detail by using both Computational Fluid Dynamic (CFD) code and structure analysis finite element code. As the results, the transient response in fluid force exerting on the local part of thermal sleeve wall surface to the primary coolant flow through the pipe junction area during the normal reactor operation mode shows oscillatory characteristics with frequencies ranging from 17 to 18, which coincide with one of the lower mode natural frequencies of thermal sleeve having a pinned support condition on the circumferential prominence on the outer surface of thermal sleeve which is put into the circumferential groove on the inner surface of SI nozzle at the mid-height of the thermal sleeve. In addition, the variation of force on the thermal sleeve surface yields alternating torques in the directions of two rectangular axes which are perpendicular to the longitudinal axis of cylindrical thermal sleeve, which cause rolling, pitching and rotating motions of the thermal sleeve. Consequently, it is seen that this flow situation surrounding the thermal sleeve during the normal reactor operation can

  3. Prediction of mechanical fatigue caused by multiple random excitations

    NARCIS (Netherlands)

    Bonte, M.H.A.; de Boer, Andries; Liebregts, R.

    2004-01-01

    A simulation method is presented for the fatigue analysis of automotive and other products that are subjected to multiple random excitations. The method is denoted as frequency domain stress-life fatigue analysis and was implemented in the automotive industry at DAF Trucks N.V. in Eindhoven, The

  4. Causes of extreme fatigue in underperforming athletes - a synthesis ...

    African Journals Online (AJOL)

    The underperformance syndrome (UPS), previously known as the overtraining syndrome (OTS), has been defined as a persistent decrement in athletic performance capacity despite 2 weeks of relative rest. Clinical research has suggested that cytokines play a key role in fatigue in disease and chronic fatigue syndrome.

  5. Basic thermal-mechanical properties and thermal shock, fatigue resistance of swaged + rolled potassium doped tungsten

    Science.gov (United States)

    Zhang, Xiaoxin; Yan, Qingzhi; Lang, Shaoting; Xia, Min; Ge, Changchun

    2014-09-01

    The potassium doped tungsten (W-K) grade was achieved via swaging + rolling process. The swaged + rolled W-K alloy exhibited acceptable thermal conductivity of 159.1 W/m K and ductile-to-brittle transition temperature of about 873 K while inferior mechanical properties attributed to the coarse pores and small deformation degree. Then the thermal shock, fatigue resistance of the W-K grade were characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities varied from 0.22 to 1.1 GW/m2 in a step of 0.22 GW/m2. The cracking threshold was in the range of 0.44-0.66 GW/m2. Furthermore, recrystallization occurred in the subsurface of the specimens tested at 0.66-1.1 GW/m2 basing on the analysis of microhardness and microstructure. Thermal fatigue tests were performed at 0.44 GW/m2 up to 1000 cycles and no cracks emerged throughout the tests. Moreover, recrystallization occurred after 1000 cycles.

  6. Formation of thermal fatigue cracks in periodic rapid quenching of metal

    Energy Technology Data Exchange (ETDEWEB)

    Ots, A. [Tallinn Technical University, Thermal Engineering Department, Tallinn (Estonia)

    1998-12-31

    Water lancing is an effective technique for cleaning boiler heating surfaces from ash deposits by burning low-grade fuels with complicated composition of mineral matter. In water cleaning cycles of boiler`s heat transfer surfaces due to rapid quenching destruction of corrosion protective oxide film and formation of thermal fatigue cracks on the outer surface of the tube`s metal occur. The criterion of the thermal fatigue cracks` formation and their growth intensity depend on the character of temperature field in the tube`s metal outer layer. The solution of non-stationary heat conductivity equation for metal rapid quenching conditions is given. The convective heat transfer coefficients from hot metal surface to water jet were established experimentally. Thermal fatigue crack growth intensity was investigated in real boilers` heat transfer surfaces` tubes as well as in laboratory conditions. The formula for predicting thermal fatigue cracks` depth depending on the number of cleaning cycles. (orig.) 5 refs.

  7. EXPERIMENTAL INVESTIGATIONS FOR MODELLING THE THERMAL FATIGUE PHENOMENON IN MACHINES PARTS OF AUTOMOTIVE ENGINES

    National Research Council Canada - National Science Library

    Camelia Pinca-Bretotean; Lucia Vîlceanu

    2013-01-01

      The purpose of this paper is to present some experimental investigations for validate an experimental plant designed and built for study the thermal fatigue phenomenon that occurs in machines parts...

  8. Thermal fatigue issues in high-gradient particle accelerators

    CERN Document Server

    Heikkinen, Samuli Tapio; Neupert, Holger

    2006-01-01

    The CLIC (Compact LInear Collider) is being studied at CERN (European Organization for Nuclear Research) as a possible future high-energy (0.5-5 TeV centre-of-mass) physics facility. The current aim of the CLIC Study Team is to demonstrate the key feasibility issues before 2010. CLIC will be about 33 kilometers long and will be buried 100 meters underground. The main linac of CLIC consists of accelerating structures with the following demanding performance requirements: accelerating gradients of about 150 MV/m, power flows of about 200 MW, 1-2 ìm dimensional tolerances, an optical-quality surface finish and ultimately a low mass production cost. About 80% of CLIC's 33 kilometer length will be filled with main beam accelerating structures, which will require of the order of ten thousand tons of raw material and millions of individual parts. One of the main limiting factors of the main linac accelerating structures is the thermal fatigue due to the pulsed surface heating. The accelerating RFpower pulses heat u...

  9. Causes, consequences and countermeasures to driver fatigue in the rail industry: The train driver perspective.

    Science.gov (United States)

    Filtness, A J; Naweed, A

    2017-04-01

    Fatigue is an important workplace risk management issue. Within the rail industry, the passing of a stop signal (signal passed at danger; SPAD) is considered to be one of the most major safety breaches which can occur. Train drivers are very aware of the negative consequences associated with a SPAD. Therefore, SPADs provide a practical and applied safety relevant context within which to structure a discussion on fatigue. Focus groups discussing contributing factors to SPADs were undertaken at eight passenger rail organisations across Australia and New Zealand (n = 28 drivers). Data relating to fatigue was extracted and inductively analysed identifying three themes: causes, consequences, and countermeasures (to fatigue). Drivers experienced negative consequences of fatigue, despite existing countermeasures to mitigate it. Organisational culture was a barrier to effective fatigue management. A fatigue assessment tool consistently informed rostering, however, shift swapping was commonplace and often unregulated, reducing any potential positive impact. In discussing fatigue countermeasure strategies, drivers talked interchangeably about mitigating task related fatigue (e.g. increasing cognitive load) and sleepiness (e.g. caffeine). Ensuring the concepts of fatigue and sleepiness are properly understood has the potential to maximise safety. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity

    Science.gov (United States)

    2011-01-01

    Background It is known that chronic fatigue is associated with sympathetic hyperactivity. However, the relationship between autonomic function and mental fatigue caused by a prolonged mental load in healthy humans is still unclear. Thus, in order to clarify the mechanisms underlying mental fatigue, we examined the association between mental fatigue and autonomic functions. Methods The study group comprised 10 healthy participants. To induce mental fatigue, participants performed mental tasks, which consisted of the advanced trail making test, kana pick-out test and mirror drawing test, for 8 hr, corresponding to a normal work day. Autonomic functions were measured by accelerated plethysmography before and after the fatigue-inducing mental tasks. As a control, the same participants completed an 8-hr relaxation session 4 weeks before the fatigue session. Results After the 8-hr relaxation session, low-frequency component power (LF), high-frequency component power (HF) and low-frequency component power/high-frequency component power ratio (LF/HF ratio) were not changed from baseline. In contrast, after the fatigue session, the HF and LF/HF ratio were significantly changed from baseline; specifically, the HF was lower and LF/HF ratio was higher as compared to those after the relaxation session. Conclusions Sympathetic hyperactivity based on decreased parasympathetic activity is associated with mental fatigue induced by prolonged cognitive load. PMID:21605411

  11. The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

    Full Text Available The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values: (wt-%: 18-40 %Ni, 17-30 %Cr, 1.2-1.6%Si and 0.05-0.6 %C. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

  12. Analysis of dominant factors affecting fatigue caused by soft-copy reading.

    Science.gov (United States)

    Ikushima, Yoichiro; Yabuuchi, Hidetake; Morishita, Junji; Honda, Hiroshi

    2013-11-01

    The aim of this study was to analyze the dominant factors affecting fatigue caused by soft-copy reading to identify a method for decreasing fatigue in clinical practice. Two types of fatigue-fatigue in the central nervous system and subjective visual fatigue-were evaluated using a critical fusion frequency test and a questionnaire administered to 17 male radiologists before and after soft-copy reading. Reading-induced fatigue was assumed to be affected by 20 hypothetical factors associated with personal characteristics, time required for reading, content or amount of reading, and the reading environment. We used multiple linear regression analysis with a variable selection method to detect the best combination of factors capable of expressing variations in each of the measured fatigue values. The effects of the detected (dominant) factors on fatigue were also examined based on coefficients of the dominant factors in multiple regression models. Fatigue in the central nervous system decreased with a higher corrected visual acuity and a higher ambient illuminance in the reading room and was also affected by the type of monitor used. Visual fatigue was relieved when there was a larger difference in the brightness of the monitor and the surfaces surrounding the monitor and tended to be more severe when glasses rather than contact lenses were worn. Increasing the ambient illuminance, using an appropriate type of monitor, improving the corrected visual acuity, and using contact lenses rather than eyeglasses could help decrease reading-induced fatigue in male radiologists. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

  13. Effects of frequency and temperature- and strain-wave form on thermal fatigue strength of type 316 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Tsunenari, Toshiyasu; Horikawa, Takeshi; Okada, Tomonobu; Take, Koji; Miyashita, Takuya (Kawasaki Heavy Industries Ltd., Akashi, Hyogo (Japan). Technical Inst.)

    1983-06-01

    The effects of frequency and temperature- and strain-wave form on thermal fatigue strength were examined by conducting out-of-phase and in-phase thermal fatigue tests with three kinds of temperature-wave forms (fast heating and fast cooling, slow heating and slow cooling, slow heating and fast cooling) under temperature cycling between 350 - 650/sup 0/C and by isothermal low-cycle fatigue tests at 650/sup 0/C under cyclic frequencies of 0.5 -- 0.039 cpm. The following results were obtained. (1) The effect of frequency on fatigue life in out-of-phase thermal fatigue was as small as in isothermal low-cycle fatigue, whereas in in-phase thermal fatigue it was much greater and the fatigue life reduction was more remarkable in low frequency. (2) The effect of temperature- and strain-wave form on thermal fatigue life was still smaller than the effect of frequency on out-of-phase thermal fatigue life. (3) The fracture mode of out-of-phase thermal fatigue was the transgranular type even at the lowest frequency tested, but that of in-phase thermal fatigue changed to the intergranular type at low frequency. (4) Out-of-phase and in-phase thermal fatigue data obtained at the test condition of such an extremely low frequency as 0.039 cpm were found to coincide well with ..delta..epsilon sub(PC) - N sub(PC) and ..delta..epsilon sub(CP) - N sub(CP) relations, respectively.

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

    Science.gov (United States)

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

    2001-01-01

    -cycle thermal fatigue behavior has been investigated on a flat Haynes 188 alloy specimen, under the test condition of 30-Hz cycle frequency (33-msec pulse period and 10-msec pulse width including a 0.2-msec pulse spike; ref. 4). Temperature distributions were calculated with one-dimensional finite difference models. The calculations show that that the 0.2-msec pulse spike can cause an additional 40 C temperature fluctuation with an interaction depth of 0.08 mm near the specimen surface region. This temperature swing will be superimposed onto the temperature swing of 80 C that is induced by the 10-msec laser pulse near the 0.53-mm-deep surface interaction region.

  15. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

    2013-07-01

    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  16. A Model of BGA Thermal Fatigue Life Prediction Considering Load Sequence Effects

    Directory of Open Access Journals (Sweden)

    Weiwei Hu

    2016-10-01

    Full Text Available Accurate testing history data is necessary for all fatigue life prediction approaches, but such data is always deficient especially for the microelectronic devices. Additionally, the sequence of the individual load cycle plays an important role in physical fatigue damage. However, most of the existing models based on the linear damage accumulation rule ignore the sequence effects. This paper proposes a thermal fatigue life prediction model for ball grid array (BGA packages to take into consideration the load sequence effects. For the purpose of improving the availability and accessibility of testing data, a new failure criterion is discussed and verified by simulation and experimentation. The consequences for the fatigue underlying sequence load conditions are shown.

  17. Damage evaluation under thermal fatigue of a vertical target full scale component for the ITER divertor

    Energy Technology Data Exchange (ETDEWEB)

    Missirlian, M. [Association Euratom-CEA, CEA/DSM/DRFC, CEA/Cadarache, F-13108 Saint Paul Lez Durance cedex (France)]. E-mail: missir@drfc.cad.cea.fr; Escourbiac, F. [Association Euratom-CEA, CEA/DSM/DRFC, CEA/Cadarache, F-13108 Saint Paul Lez Durance cedex (France); Merola, M. [EFDA Close Support Unit, Garching (Germany); Durocher, A. [Association Euratom-CEA, CEA/DSM/DRFC, CEA/Cadarache, F-13108 Saint Paul Lez Durance cedex (France); Bobin-Vastra, I. [FRAMATOME, Le Creusot (France); Schedler, B. [PLANSEE , Aktiengesellschaft-A-6600 Reutte (Austria)

    2007-08-01

    An extensive development programme has been carried out in the EU on high heat flux components within the ITER project. In this framework, a Full Scale Vertical Target (VTFS) prototype was manufactured with all the main features of the corresponding ITER divertor design. The fatigue cycling campaign on CFC and W armoured regions, proved the capability of such a component to meet the ITER requirements in terms of heat flux performances for the vertical target. This paper discusses thermographic examination and thermal fatigue testing results obtained on this component. The study includes thermal analysis, with a tentative proposal to evaluate with finite element approach the location/size of defects and the possible propagation during fatigue cycling.

  18. Fatigue

    Science.gov (United States)

    ... as systemic lupus erythematosus Cancer Heart failure Diabetes Fibromyalgia Infection, especially one that takes a long time ... Bennett RM. Fibromyalgia, chronic fatigue syndrome, and ... Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, ...

  19. The Influence of Laser Surface Alloying on the Thermal Fatigue Resistance of Hot Work Tool Steels

    Directory of Open Access Journals (Sweden)

    Jonda E.

    2016-09-01

    Full Text Available The paper presents results of the effect of laser surface remelting and alloying by carbides powders of NbC, TaC, TiC, VC and WC on the structure and thermal fatigue resistance of the surface layer of hot work tool steels X40CrMoV5-1 and 32CrMoV12-28. The laser surface alloying and remelting treatments was performed using a high power diode laser (HPDL ROFIN SINAR DL 020. In order to investigate the effect of applied laser treatments and used alloying powders on the microstructure and thermal fatigue resistance of processed surface layer of hot work tool steels, the microstructure evaluation by light microscopy, hardness test, and dedicated thermal fatigue resistance test were performed. The best results regarding fatigue cracks inhibition was obtained when the surface of hot work tool steels was alloyed with TiC and VC carbides at the laser beam power of 2.0 and 2.3 kW. The grain refinement effect of laser remelting has a lower impact on the thermal crack inhibition, than a strong strengthening effect of matrix saturation in alloying elements and precipitation of fine carbides in the steel matrix.

  20. Effect of mental fatigue caused by mobile 3D viewing on selective attention: an ERP study.

    Science.gov (United States)

    Mun, Sungchul; Kim, Eun-Soo; Park, Min-Chul

    2014-12-01

    This study investigated behavioral responses to and auditory event-related potential (ERP) correlates of mental fatigue caused by mobile three-dimensional (3D) viewing. Twenty-six participants (14 women) performed a selective attention task in which they were asked to respond to the sounds presented at the attended side while ignoring sounds at the ignored side before and after mobile 3D viewing. Considering different individual susceptibilities to 3D, participants' subjective fatigue data were used to categorize them into two groups: fatigued and unfatigued. The amplitudes of d-ERP components were defined as differences in amplitudes between time-locked brain oscillations of the attended and ignored sounds, and these values were used to calculate the degree to which spatial selective attention was impaired by 3D mental fatigue. The fatigued group showed significantly longer response times after mobile 3D viewing compared to before the viewing. However, response accuracy did not significantly change between the two conditions, implying that the participants used a behavioral strategy to cope with their performance accuracy decrement by increasing their response times. No significant differences were observed for the unfatigued group. Analysis of covariance revealed group differences with significant and trends toward significant decreases in the d-P200 and d-late positive potential (LPP) amplitudes at the occipital electrodes of the fatigued and unfatigued groups. Our findings indicate that mentally fatigued participants did not effectively block out distractors in their information processing mechanism, providing support for the hypothesis that 3D mental fatigue impairs spatial selective attention and is characterized by changes in d-P200 and d-LPP amplitudes. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Thermal fatigue and creep evaluation for the bed in tritium SDS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Woo-seok, E-mail: wschoi@kaeri.re.kr [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Park, Chang-gyu [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Ju, Yong-sun [KOASIS, Yuseong, Daejeon (Korea, Republic of); Kang, Hyun-goo; Jang, Min-ho; Yun, Sei-hun [National Fusion Research Institute, Yuseong, Daejeon (Korea, Republic of)

    2016-11-01

    Highlights: • To evaluate the integrity of the ITER tritium SDS bed, three kinds of assessments were conducted. • The structural analysis showed that the stress induced from the thermal load and the internal pressure is within the design stress intensity. • The combined fatigue and creep assessment was also performed according to the procedure of ASME code Subsection NH. • A new operation procedure to obtain more integrity margin was recommended. • The other operation procedure could be considered which makes the rapid operation possible giving up the marginal integrity. - Abstract: The primary vessel of ITER tritium SDS bed is made of stainless steel. It is heated beyond 500 °C to desorb tritium. During this process the primary vessel is subject to thermal stress. And it is also subject to thermal fatigue by the iterative process of absorption and desorption. In addition, its operation temperature range is in the thermal creep temperature region. Therefore, the tritium SDS bed should have sufficient design stress intensity under the high temperature operating conditions. It should also be free of damage due to fatigue during the design life. Thermal analysis and structural analysis was performed using a finite element method to calculate the temperature and the stress distribution of the ITER tritium SDS bed due to the internal pressure and thermal loads. The thermal fatigue and creep effects were also evaluated since the tritium SDS bed was heated to hot temperature region where creep occurs. Based on the distribution of the primary stress and secondary stress results, two evaluation cross-sections were selected. The evaluation showed that the calculated value on the cross-sections satisfied all of the limits of the design code requirements.

  2. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Kristin Halvorsen Hortemo

    Full Text Available Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an

  3. Workplace aggression as cause and effect: Emergency nurses' experiences of working fatigued.

    Science.gov (United States)

    Wolf, Lisa A; Perhats, Cydne; Delao, Altair M; Clark, Paul R

    2017-07-01

    Emergency nursing requires acute attention to detail to provide safe and effective care to potentially unstable or critically ill patients; this requirement may be significantly impaired by physical and mental fatigue. There is a lack of evidence regarding the effects of fatigue caused by factors other than a sleep deficit (e.g., emotional exhaustion). Fatigue affects nurses' ability to work safely in the emergency care setting and potentially impacts their health and quality of life outside of work. This was the qualitative arm of a mixed methods study; we used a qualitative exploratory design with focus group data from a sample of 16 emergency nurses. Themes were identified using an inductive approach to content analysis. The following themes were identified: "It's a weight on your back;" "Competitive nursing;" "It's never enough;" "You have to get away;" and "Engagement as a solution." Our participants reported high levels of fatigue, which compromised patient care, had a negative effect on their personal lives, and created a toxic unit environment. They reported lateral violence as both the cause and effect of mental and emotional fatigue, suggesting that unit culture affects nurses and the patients they care for. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Thermal fatigue crack nucleation in ferritic-martensitic steels before and after neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Belyaeva, L.A.; Zisman, A.A.; Petersen, C. E-mail: claus.petersen@imf.fzk.de; Potapova, V.A.; Rybin, V.V

    2000-12-01

    Thermal fatigue behaviour of the ferritic-martensitic steels MANET-II, 12Cr-1.5NiMo and F82H-mod. have been investigated in the temperature range from 50 deg. C to 350 deg. C and total strain range {<=}0.33%. Crack appearance has been checked after 3x10{sup 3}, 6x10{sup 3} and 10{sup 4} cycles and has been successively detected in these steels. The thermal fatigue cracks have a transgranular character; sometimes, intergranular cracks are observed in the F82H-mod. steel. A certain correlation of grain size and ferrite content with the thermal fatigue crack peculiarities has been noted. Specimens of MANET-II and 12Cr-1.5NiMo have been irradiated in a WWR-M reactor with a fluence of 1x10{sup 25} n m{sup -2} at a temperature of 300 deg. C and then subjected to thermocyclic loading. It has been established that the neutron irradiation does not significantly affect fatigue crack nucleation in both materials.

  5. Simulation and Experiment of Thermal Fatigue in the CPV Die Attach: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, N.; Silverman, T.; Kurtz, S.

    2012-05-01

    FEM simulation and accelerated thermal cycling have been performed for the CPV die attach. Trends in fatigue damage accumulation and equivalent test time are explored and found to be most sensitive to temperature ramp rate. Die attach crack growth is measured through cycling and found to be in excellent agreement with simulations of the inelastic strain energy accumulated. Simulations of an entire year of weather data provides for the relative ranking of fatigue damage between four cites as well as their equivalent accelerated test time.

  6. Thermal load effects on fatigue life of a cracked railway wheel

    Directory of Open Access Journals (Sweden)

    Azadeh Haidari

    Full Text Available AbstractIn this paper, fatigue life of a cracked railway wheel under thermo-mechanical loads is studied. For this purpose a FE model of a wheel, with two brake shoes and a portion of rail is created and suitable loads and boundary conditions are applied to the model. It is assumed that the wheel has contained an elliptical crack in the definite depth of the tread surface and thermalloads are determined by modeling the contact of the rail-wheel and two brake blocks. In order to investigate the thermalloads effect on the fatigue life of the cracked wheel, analyses areperformed in two cases: mechanical analysis and thermo-mechanical analysis; while difference between them, shows thermal load effects and its importance. In this work the wheel rotation on rail is modeled and a 3D FE model for determination of rail-wheel contact pressure is used while in many of the previous investigations, either rolling wasn't modeled or its effect was simplified as a translating pressure distribution along the rail-wheel contact region and also the Hertz contact theory had used for determination of contact pressure in wheel- rail interface. Finally, effects of angular velocity on fatigue life of a cracked wheel under -mechanical and mechanical loads are shown. The obtained results confirm the important influences of thermal loads on the wheel fatigue life in all mentioned cases that are studied in this article.

  7. Expanding of the fatigue life of thermal barrier coating by mixing MoSl{sub 2} to thermal sprayed layer

    Energy Technology Data Exchange (ETDEWEB)

    Sonoya, K. [Ishikawajima-Harima Heavy Industries Co. Ltd., Yokohama (Japan); Tobe, S. [Ashikaga Inst. of Tech., Ashikaga-shi, Tochigi-ken (Japan)

    2000-07-01

    Recent trends of turbine blades of advanced aircraft gas turbine engines are to increase output power of the engines, to increase engine efficiency and to reduce environmental emission, and thus, higher operating temperatures of the engines are required. One of the technologies for increasing the operating temperature is a thermal barrier splayed coating [1,2]. The coating usually consists of a bonding coating layer of an alloy of NiCrAlY on the turbine blade and a top layer of ZrO{sub 2}-Y{sub 2}O{sub 3}, namely, partially stabilized zirconia (PSZ). However, conventional coating systems deteriorate during turbine operation due to thermal and mechanical stresses imposed and corrosion actions by combustion gas coming from combustion chambers. Thus, the main issue is to develop measures against high oxidation rate and low fatigue life of the bonding coating layer. An idea for enhancing oxidation resistance and fatigue life as well of thermal barrier coatings consisting of a zirconia-based coating is to provide with a self-healing capability to the coating by diffusing a suitable substance to fatigue crack surfaces formed in the coating. Excessive oxidation of the NiCrAlY layer beneath is prevented for extending fatigue life of the splayed barrier coating. Several investigations have been conducted on the matter, and a research paper [3] claims that MoSi{sub 2} in a splayed coating has a self-healing capability for cracks formed in the coating by embedding the cracks with SiO{sub 2} formed from MoSi{sub 2} at high temperatures. Thus, a new coating system containing NiCrAlY, MoSi{sub 2}, and PSZ is expected to be developed instead of a two-layer coating system of NiCrAlY and PSZ.

  8. Comparison of experimental and theoretical thermal fatigue lives for five nickel base alloys

    Science.gov (United States)

    Spera, D. A.

    1972-01-01

    The alloys Nimonic 90, IN 100, coated IN 100, B 1900, coated B 1900, MAR M200, and MAR M200DS (directionally solidified) were studied. Maximum temperatures ranged from 770 C to 1120 C (1420 F to 2050 F). Specimen geometries included tapered disks, double-edged wedges, and cambered airfoils. The disks and wedges were heated and cooled in fluidized beds. The airfoil specimens were heated by a Mach 1 natural gas burner and rapid-air-cooled, with and without spanwise loading. Life calculations included two distinct failure modes: conventional low cycle fatigue and cyclic creep. Required material properties were limited to conventional thermal, tensile, and creep rupture data. The complete life calculation system included the calculation of transient temperature distributions, thermal strains, stresses, creep damage, fatigue damage, and cycles to first crack. Calculated lives were within a factor of two for 76 of the 86 data points analyzed. Cyclic creep accounted for 81% of all the calculated damage.

  9. Examination of high heat flux components for the ITER divertor after thermal fatigue testing

    Energy Technology Data Exchange (ETDEWEB)

    Missirlian, M., E-mail: marc.missirlian@cea.fr [CEA, IRFM, F-13108 Saint Paul lez Durance (France); Escourbiac, F., E-mail: frederic.escourbiac@cea.fr [CEA, IRFM, F-13108 Saint Paul lez Durance (France); Schmidt, A., E-mail: a.schmidt@fz-juelich.de [Forschungszentrum Juelich, IFE-2 (Germany); Riccardi, B., E-mail: Bruno.Riccardi@f4e.europa.eu [Fusion For Energy, E-08019 Barcelona (Spain); Bobin-Vastra, I., E-mail: isabelle.bobinvastra@areva.com [AREVA-NP, 71200 Le Creusot (France)

    2011-10-01

    An extensive development programme has been carried out in the EU on high heat flux components within the ITER project. In this framework, a full-scale vertical target (VTFS) prototype was manufactured with all the main features of the corresponding ITER divertor design. The fatigue cycling campaign on CFC and W armoured regions, proved the capability of such a component to meet the ITER requirements in terms of heat flux performances for the vertical target. This paper discusses metallographic observations performed on both CFC and W part after this intensive thermal fatigue testing campaign for a better understanding of thermally induced mechanical stress within the component, especially close to the armour-heat sink interface.

  10. Thermal and Fatigue Evaluation of Asphalt Mixtures Containing RAP Treated with a Bio-Agent

    Directory of Open Access Journals (Sweden)

    Karol J. Kowalski

    2017-02-01

    Full Text Available Environment conservation and diminishing natural resources caused an increase in popularity of the application of renewable bio-origin resources for the construction of road pavement. Currently, there are known additions of bio-origin materials for bitumen modification. Such material is also used as a flux additive for bitumen or as a rejuvenator once working with reclaimed asphalt pavement (RAP. This paper presents research dealing with asphalt mixtures with RAP modified with a bio-agent of rapeseed origin. The main idea of the conducted research was to apply more RAP content directly to the batch mix plant without extra RAP heating. The RAP used in this study was milled from a base asphalt layer; the addition of RAP stiffens new asphalt mixtures. A bio-agent, due to its fluxing action, was used to support the asphalt mixing process and to decrease the over-stiffening of the mixture caused by RAP addition. This research includes bitumen and mixture tests. For the bitumen study, three different bitumens (35/50, 50/70, and 70/100 were tested in a dynamic shear rheometer (DSR for complex modulus G* and for phase angle |δ| in the temperature range 0–100 °C. The reference mixture and mixtures with 2.5% bio-agent were tested to assess the influence of RAP and the bio-agent addition on the asphalt mixture properties. Low temperature behavior (TSRST, stiffness, and fatigue resistance (4PB were tested. Based on the bitumen test, it was determined that even a low rate of bio-agent (2.5% beneficially changes bitumen properties at a low temperature; moreover, polymerization processes occurring in the second stage of the process improves bitumen properties at a high operational temperature. The research with these asphalt mixtures demonstrates that the bio-origin flux acts as a rejuvenator and allows for an application of 30% cold RAP. Thermal cracking resistance of the mixture with RAP and 2.5% bio-agent improved. The bio-agent removes unfavorable

  11. Numerical simulation of long-period fluid temperature fluctuation at a mixing tee for the thermal fatigue problem

    Energy Technology Data Exchange (ETDEWEB)

    Utanohara, Yoichi, E-mail: utanohara@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Nakamura, Akira, E-mail: a-naka@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Miyoshi, Koji, E-mail: miyoshi.koji@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Kasahara, Naoto, E-mail: kasahara@n.t.u-tokyo.ac.jp [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-08-15

    Highlights: • A large eddy simulation of a mixing tee was carried out. • Fluid temperature fluctuation could be predicted qualitatively. • Grid convergence was almost attained and the simulation continued until 100 s. • A longer-period temperature fluctuation than the well-known St = 0.2 appeared. • Prediction of long-period temperature fluctuations improves the thermal fatigue assessment. - Abstract: Thermal fatigue cracks may be initiated at mixing tees where high and low temperature fluids flow in and mix. According to a previous study, damage by thermal fatigue depends on the frequency of the fluid temperature fluctuation near the wall surface. Structures have the time constant of structural response that depends on physical properties of the structure and the gain of the frequency response tends to become maximum at the frequency lower than the typical frequency of fluid temperature fluctuation. Hence the effect of the lower frequency, that is, long-period temperature fluctuation is important for the thermal fatigue assessment. The typical frequency of fluid temperature fluctuation is about St = 0.2 (nearly 6 Hz), where St is Strouhal number and means non-dimensional frequency. In the experimental study by Miyoshi et al. (2014), a longer-period fluctuation than St = 0.2 was also observed. Results of a fluid–structure coupled analysis by Kamaya et al. (2011) showed this long-period temperature fluctuation causes severer damage to piping. In the present study, a large eddy simulation was carried out to investigate the predictive performance of the long-period fluid temperature fluctuation more quantitatively. Numerical simulation was conducted for the WATLON experiment which was the water experiment of a mixing tee performed at the Japan Atomic Energy Agency. Four computational grids were used to confirm grid convergence. In the short time (9 s) simulations, tendencies of time-averaged and fluctuated velocities could be followed. Time

  12. Effect of thermal fatigue on the wear resistance of graphite cast iron with bionic units processed by laser cladding WC

    Science.gov (United States)

    Jing, Zhengjun; Zhou, Hong; Zhang, Peng; Wang, Chuanwei; Meng, Chao; Cong, Dalong

    2013-04-01

    Thermal fatigue and wear exist simultaneously during the service life of brake discs. Previous researchers only studied thermal fatigue resistance or abrasion resistance of compact graphite cast iron (CGI), rather than combining them together. In this paper, wear resistance after thermal fatigue of CGI was investigated basing on the principle of bionics, which was close to actual service condition of the brake discs. In the meanwhile, the effect of thermal fatigue on wear resistance was also discussed. Non-smooth bionic units were fabricated by laser cladding WC powder with different proportions (50 wt.%, 60 wt.%, 70 wt.%). Microstructure and microhardness of the units were investigated, and wear mass losses of the samples were also compared. The results indicate that thermal fatigue has a negative effect on the wear resistance. After the same thermal fatigue cycles times, the wear resistance of laser cladding WC samples is superior to that of laser remelting ones and their wear resistance enhances with the increase of WC content.

  13. Effect of autoclave sterilization on the cyclic fatigue resistance of thermally treated Nickel-Titanium instruments.

    Science.gov (United States)

    Zhao, D; Shen, Y; Peng, B; Haapasalo, M

    2016-10-01

    To compare the cyclic fatigue resistance of HyFlex CM, Twisted Files (TF), K3XF, Race, and K3, and evaluate the effect of autoclave sterilization on the cyclic fatigue resistance of these instruments both before and after the files were cycled. Five types of NiTi instruments with similar size 30, .06 taper were selected: HyFlex CM, TF, K3XF, Race and K3. Files were tested in a simulated canal with a curvature of 60° and a radius of 3 mm. The number of cycles to failure of each instrument was determined to evaluate cyclic fatigue resistance. Each type of instruments was randomly divided into four experimental groups: group 1 (n = 20), unsterilized instruments; group 2 (n = 20), pre-sterilized instruments subjected to 10 cycles of autoclave sterilization; group 3 (n = 20), instruments tested were sterilized at 25%, 50% and 75% of the mean cycles to failure as determined in group 1, and then cycled to failure; group 4 (n = 20), instruments cycled in the same manner as group 3 but without sterilization. The fracture surfaces of instruments were examined by scanning electron microscopy (SEM). HyFlex CM, TF and K3XF had significantly higher cyclic fatigue resistance than Race and K3 in the unsterilized group 1 (P HyFlex CM and K3XF (P HyFlex CM, TF and K3XF instruments composed of new thermal-treated alloy were more resistant to fatigue failure than Race and K3. Autoclaving extended the cyclic fatigue life of HyFlex CM and K3XF. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  14. Effect of unit size on thermal fatigue behavior of hot work steel repaired by a biomimetic laser remelting process

    Science.gov (United States)

    Cong, Dalong; Li, Zhongsheng; He, Qingbing; Chen, Dajun; Chen, Hanbin; Yang, Jiuzhou; Zhang, Peng; Zhou, Hong

    2018-01-01

    AISI H13 hot work steel with fatigue cracks was repaired by a biomimetic laser remelting (BLR) process in the form of lattice units with different sizes. Detailed microstructural studies and microhardness tests were carried out on the units. Studies revealed a mixed microstructure containing martensite, retained austenite and carbide particles with ultrafine grain size in units. BLR samples with defect-free units exhibited superior thermal fatigue resistance due to microstructure strengthening, and mechanisms of crack tip blunting and blocking. In addition, effects of unit size on thermal fatigue resistance of BLR samples were discussed.

  15. Lifetime prediction of structures submitted to thermal fatigue loadings; Prediction de duree de vie de structures sous chargement de fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Amiable, S

    2006-01-15

    The aim of this work is to predict the lifetime of structures submitted to thermal fatigue loadings. This work lies within the studies undertaken by the CEA on the thermal fatigue problems from the french reactor of Civaux. In particular we study the SPLASH test: a specimen is heated continuously and cyclically cooled down by a water spray. This loading generates important temperature gradients in space and time and leads to the initiation and the propagation of a crack network. We propose a new thermo-mechanical model to simulate the SPLASH experiment and we propose a new fatigue criterion to predict the lifetime of the SPLASH specimen. We propose and compare several numerical models with various complexity to estimate the mechanical response of the SPLASH specimen. The practical implications of this work are the reevaluation of the hypothesis used in the French code RCC, which are used to simulate thermal shock and to interpret the results in terms of fatigue. This work leads to new perspectives on the mechanical interpretation of the fatigue criterion. (author)

  16. Cyclic impulsive compression loading along the radial and tangential wood directions causes localized fatigue

    Science.gov (United States)

    Salmi, Ari; Montonen, Risto; Salminen, Lauri I.; Suuronen, Jussi-Petteri; Serimaa, Ritva; Hæggström, Edward

    2012-12-01

    We report for the first time on the existence of a localized reduction in elasticity caused by repeated compression impaction applied along the tangential wood direction. Previous research indicates that localized strain profiles are generated by such cyclic impacting on wood along its radial direction. This finding is significant for the paper/board-making industry where wood is exposed to cyclic unipolar compression during grinding. However, the effect of the impacting direction, with respect to the orientation of the annual rings, on the localization phenomenon is unknown. In addition, the shape of the developing fatigue layer is unclear. We revisit the localization phenomenon with a focus on tangential impacting. We employed ultrasonics and x-ray tomography to quantify the induced fatigue. An interlacing technique increased the precision of the ultrasonic stiffness depth profiling technique. We studied both radial and tangential wood annual ring geometries. We used ultrasound to quantify the drop in shear modulus resulting from impacting. Both radial and tangential geometries featured strain localization, but the shape of the fatigued layer was different in the radial and tangential wood geometries (steeper profile in the radial geometry). The fatiguing reduced the shear modulus. These results tell us about the ratio of the number of hits that need to be delivered along the radial and tangential direction of the ground wood, respectively. This insight may translate into a design pattern for an energy saving grind stone surface.

  17. The predictive value of fatigue for nonfatal ischemic heart disease and all-cause mortality

    DEFF Research Database (Denmark)

    Ekmann, Anette; Osler, Merete; Avlund, Kirsten

    2012-01-01

    Objective To investigate whether fatigue predicts nonfatal ischemic heart disease (IHD) and all-cause mortality in middle-aged men. Methods The study population consisted of 5216 middle-aged men born in the Copenhagen metropolitan area in 1953. At baseline, men free of angina pectoris and previou...... is a potential risk indicator for IHD and mortality. Further research is needed to establish the role of smoking and other life-style characteristics....

  18. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    Science.gov (United States)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  19. Study of the neuroendocrine and immunologic mechanism of fatigue caused by military operations

    Directory of Open Access Journals (Sweden)

    Xin LI

    2012-01-01

    Full Text Available Objective  To observe the regularity of the changes in neuroendocrine-immune system caused by fatigue due to military operations, and explore the mechanism by which fatigue occurs in military operations. Methods  The subjects were 240 soldiers belonging to a field artillery force. The medical history and physical examination were taken before military operations, and fatigue assessment scale was accomplished as well. The following variables were measured in all the subjects: pituitary-adrenal [adrenocorticotropic hormone (ACTH, cortical hormone (B, 24-h urinary free cortisol (UFC], pituitary-gonadal [luteinizing hormone (LH, testosterone (T, estradiol (E2], pituitary-thyroid functions [serum thyroid stimulating hormone (TSH, tetraiodothyronine (TT4, triiodothyronine (TT3, free thyroxine (FT4, and free triiodothyronine (FT3], and cellular immune parameters (CD3+, CD4+, CD8+, CD4+/CD8+, B, NK. After 7 d of large-scale and high-intensity field exercises, the above variables were again measured in all the subjects. Results  After high-intensity military operations, the unpleasant feelings were significantly increased, and the compulsive and psychotic scores significantly decreased in the soldiers. In addition, the pituitary-adrenal and pituitary-gonadal hormone levels also decreased (all PPPConclusion  The depressed psychological tolerance in soldiers is the psychological factor of fatigue after a high-intensity military operation. The hypocorticoidism and inhibition of hypothalamic-pituitary-gonadal axis are the pathophysiological basis of military operation fatigue. Suppression of immune function is an important reason for an increase of susceptibility to disease after high-intensity military operations.

  20. Influence of test parameters on the thermal-mechanical fatigue behavior of a superalloy

    Science.gov (United States)

    Malpertu, J. L.; Rémy, L.

    1990-01-01

    The thermal-mechanical fatigue (TMF) behavior of IN-100, a cast nickel-base superalloy, was investigated with a basic mechanical strain-temperature loop applied in a temperature range from 600 °C to 1050 °C (873 to 1323 K). Peak strains were applied at intermediate temperatures, giving a faithful simulation of real component parts. Tests with or without a mean strain were used; other tests involved a longer period or a tensile hold time, and they were compared with conventional “in-phase” TMF cycles. An interrupted test procedure was used with a plastic replication technique to define a conventional TMF life to 0.3-mm crack depth, as well as a life to 50-µm, crack depth, to characterize the crack initiation period. Some stress-strain hysteresis loops were reported. Thermal-mechanical fatigue life was found to be dependent upon test parameters, while the life to crack initiation was not. Oxidation of specimens and micro-cracks was found to be important in all the tests. These results were then discussed and compared with those under low cycle fatigue at high temperature.

  1. Comparison of experimental and theoretical thermal fatigue lives for five nickel-base alloys.

    Science.gov (United States)

    Spera, D. A.

    1972-01-01

    Alloys investigated were Nimonic 90, IN 100, coated IN 100, B 1900, coated B 1900, MAR M200, and MAR M200DS (directionally solidified). Maximum temperatures ranged from 770 to 1120 C. Specimen geometries included tapered disks, double-edged wedges, and cambered airfoils. The disks and wedges were heated and cooled in fluidized beds. The airfoil specimens were heated by a Mach 1 natural gas burner and rapid-air cooled, with and without spanwise loading. Life calculations included two distinct failure modes: conventional low-cycle fatigue and cyclic creep. The complete life calculation system included the calculation of transient temperature distributions, thermal strains, stresses, creep damage, fatigue damage, and finally cycles to first crack. Calculated lives were within a factor of two for 76 of the 86 data points analyzed.

  2. Advanced Failure Determination Measurement Techniques Used in Thermal Fatigue Life Testing of Electronic Packaging

    Science.gov (United States)

    Wallace, A. P.; Cornford, S. L.; Gross, M. A.

    1996-01-01

    Thermal fatigue life testing of various electronic packaging technologies is being performed by the Reliability Technology Group at the Jet Propulsion Laboratory. These testing efforts are in progress to improve uderstanding of the reliability issues associated with low volume packaging technologies for space applications and to develop qualification and acceptance approaches for these technologies. The work described here outlines the electrical failure detection techniques used during testing by documenting the circuits and components used to make these measurements, the sensitivity of the measurements, and the applicability of each specific measurement.

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

    Science.gov (United States)

    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.

  4. Microdamage Caused by Fatigue Loading in Human Cancellous Bone: Relationship to Reductions in Bone Biomechanical Performance

    Science.gov (United States)

    Lambers, Floor M.; Bouman, Amanda R.; Rimnac, Clare M.; Hernandez, Christopher J.

    2013-01-01

    Vertebral fractures associated with osteoporosis are often the result of tissue damage accumulated over time. Microscopic tissue damage (microdamage) generated in vivo is believed to be a mechanically relevant aspect of bone quality that may contribute to fracture risk. Although the presence of microdamage in bone tissue has been documented, the relationship between loading, microdamage accumulation and mechanical failure is not well understood. The aim of the current study was to determine how microdamage accumulates in human vertebral cancellous bone subjected to cyclic fatigue loading. Cancellous bone cores (n = 32) from the third lumbar vertebra of 16 donors (10 male, 6 female, age 76±8.8, mean ± SD) were subjected to compressive cyclic loading at σ/E0 = 0.0035 (where σ is stress and E0 is the initial Young’s modulus). Cyclic loading was suspended before failure at one of seven different amounts of loading and specimens were stained for microdamage using lead uranyl acetate. Damage volume fraction (DV/BV) varied from 0.8±0.5% (no loading) to 3.4±2.1% (fatigue-loaded to complete failure) and was linearly related to the reductions in Young’s modulus caused by fatigue loading (r2 = 0.60, pfatigue life was nonlinear and suggests that most microdamage generation occurs late in fatigue loading, during the tertiary phase. Our results indicate that human vertebral cancellous bone tissue with a DV/BV of 1.5% is expected to have, on average, a Young’s modulus 31% lower than the same tissue without microdamage and is able to withstand 92% fewer cycles before failure than the same tissue without microdamage. Hence, even small amounts of microscopic tissue damage in human vertebral cancellous bone may have large effects on subsequent biomechanical performance. PMID:24386247

  5. Fatigue life of fibre reinforced plastics at 295 K after thermal cycling between 295 K and 77 K

    Science.gov (United States)

    Belisario, G.; Caproni, F.; Marchetti, E.

    Results of low cycle three-point end fatigue tests at 295 K are reported. These were obtained from fibre reinforced plastics (FRP) flat specimens made of epoxy matrix reinforced with glass rovings only or glass rovings and Kevlar cloth. It is shown that previous thermal cycles between 295 K and 77 K exert an influence on the fatigue life as well on the acoustic emission results.

  6. Imposed Thermal Fatigue and Post-Thermal-Cycle Wear Resistance of Biomimetic Gray Cast Iron by Laser Treatment

    Science.gov (United States)

    Sui, Qi; Zhou, Hong; Zhang, Deping; Chen, Zhikai; Zhang, Peng

    2017-08-01

    The present study aims to create coupling biomimetic units on gray cast iron substrate by laser surface treatment (LST). LSTs for single-step (LST1) and two-step (LST2) processes, were carried out on gray cast iron in different media (air and water). Their effects on microstructure, thermal fatigue, and post-thermal-cycle wear (PTW) resistance on the specimens were studied. The tests were carried out to examine the influence of crack-resistance behavior as well as the biomimetic surface on its post-thermal-cycle wear behavior and different units, with different laser treatments for comparison. Results showed that LST2 enhanced the PTW behaviors of gray cast iron, which then led to an increase in its crack resistance. Among the treated cast irons, the one treated by LST2 in air showed the lowest residual stress, due to the positive effect of the lower steepness of the thermal gradient. Moreover, the same specimen showed the best PTW performance, due to its superior crack resistance and higher hardness as a result of it.

  7. Thermal fatigue of a 304L austenitic stainless steel: simulation of the initiation and of the propagation of the short cracks in isothermal and aniso-thermal fatigue; Fatigue thermique d'un acier inoxydable austenitique 304L: simulation de l'amorcage et de la croissance des fissures courtes en fatigue isotherme et anisotherme

    Energy Technology Data Exchange (ETDEWEB)

    Haddar, N

    2003-04-01

    The elbow pipes of thermal plants cooling systems are submitted to thermal variations of short range and of variable frequency. These variations bound to temperature changes of the fluids present a risk of cracks and leakages. In order to solve this problem, EDF has started the 'CRECO RNE 808' plan: 'thermal fatigue of 304L austenitic stainless steels' to study experimentally on a volume part, the initiation and the beginning of the propagation of cracks in thermal fatigue on austenitic stainless steels. The aim of this study is more particularly to compare the behaviour and the damage of the material in mechanic-thermal fatigue (cycling in temperature and cycling in deformation) and in isothermal fatigue (the utmost conditions have been determined by EDF for the metal: Tmax = 165 degrees C and Tmin = 90 degrees C; the frequency of the thermal variations can reach a Hertz). A lot of experimental results are given. A model of lifetime is introduced and validated. (O.M.)

  8. Fatigue failure kinetics and structural changes in lead-free interconnects due to mechanical and thermal cycling

    Science.gov (United States)

    Fiedler, Brent Alan

    Environmental and human health concerns drove European parliament to mandate the Reduction of Hazardous Substances (RoHS) for electronics. This was enacted in July 2006 and has practically eliminated lead in solder interconnects. There is concern in the electronics packaging community because modern lead-free solder is rich in tin. Presently, near-eutectic tin-silver-copper solders are favored by industry. These solders are stiffer than the lead-tin near-eutectic alloys, have a higher melting temperature, fewer slip systems, and form intermetallic compounds (IMC) with Cu, Ni and Ag, each of which tend to have a negative effect on lifetime. In order to design more reliable interconnects, the experimental observation of cracking mechanisms is necessary for the correct application of existing theories. The goal of this research is to observe the failure modes resulting from mode II strain and to determine the damage mechanisms which describe fatigue failures in 95.5 Sn- 4.0 Ag - 0.5 Cu wt% (SAC405) lead-free solder interconnects. In this work the initiation sites and crack paths were characterized for SAC405 ball-grid array (BGA) interconnects with electroless-nickel immersion-gold (ENIG) pad-finish. The interconnects were arranged in a perimeter array and tested in fully assembled packages. Evaluation methods included monotonic and displacement controlled mechanical shear fatigue tests, and temperature cycling. The specimens were characterized using metallogaphy, including optical and electron microscopy as well as energy dispersive spectroscopy (EDS) and precise real-time electrical resistance structural health monitoring (SHM). In mechanical shear fatigue tests, strain was applied by the substrates, simulating dissimilar coefficients of thermal expansion (CTE) between the board and chip-carrier. This type of strain caused cracks to initiate in the soft Sn-rich solder and grow near the interface between the solder and intermetallic compounds (IMC). The growth near

  9. The Influence of PV Module Materials and Design on Solder Joint Thermal Fatigue Durability

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, Nick; Silverman, Timothy J.; Kurtz, Sarah

    2016-11-01

    Finite element model (FEM) simulations have been performed to elucidate the effect of flat plate photovoltaic (PV) module materials and design on PbSn eutectic solder joint thermal fatigue durability. The statistical method of Latin Hypercube sampling was employed to investigate the sensitivity of simulated damage to each input variable. Variables of laminate material properties and their thicknesses were investigated. Using analysis of variance, we determined that the rate of solder fatigue was most sensitive to solder layer thickness, with copper ribbon and silicon thickness being the next two most sensitive variables. By simulating both accelerated thermal cycles (ATCs) and PV cell temperature histories through two characteristic days of service, we determined that the acceleration factor between the ATC and outdoor service was independent of the variables sampled in this study. This result implies that an ATC test will represent a similar time of outdoor exposure for a wide range of module designs. This is an encouraging result for the standard ATC that must be universally applied across all modules.

  10. Thermal Fatigue Testing of ZrO2-Y2O3 Thermal Barrier Coating Systems using a High Power CO2 Laser

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    1997-01-01

    In the present study, the mechanisms of fatigue crack initiation and propagation, and of coating failure, under thermal loads that simulate diesel engine conditions, are investigated. The surface cracks initiate early and grow continuously under thermal Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) stresses. It is found that, in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures. Significant LCF and HCF interactions have been observed in the thermal fatigue tests. The fatigue crack growth rate in the ceramic coating strongly depends on the characteristic HCF cycle number, N*(sub NCF), which is defined as the number of HCF cycles per LCF cycle. The crack growth rate is increased from 0.36 microns/LCF cycle for a pure LCF test to 2.8 microns/LCF cycle for a combined LCF and HCF test at N*(sub NCF) about 20,000. A surface wedging model has been proposed to account for the HCF crack growth in the coating systems. This mechanism predicts that HCF damage effect increases with increasing surface temperature swing, the thermal expansion coefficient and the elastic modulus of the ceramic coating, as well as with the HCF interacting depth. A good agreement has been found between the analysis and experimental evidence.

  11. Chronic Fatigue Syndrome

    Science.gov (United States)

    Chronic fatigue syndrome (CFS) is a disorder that causes extreme fatigue. This fatigue is not the kind of tired feeling that ... activities. The main symptom of CFS is severe fatigue that lasts for 6 months or more. You ...

  12. Thermal fatigue behaviour of a 2014/Al{sub 2}O{sub 3}-SiO{sub 2} (Saffil{trademark}fibers) composite processed by squeeze casting

    Energy Technology Data Exchange (ETDEWEB)

    Badini, C.; Fino, P. [Politecnico di Torino (Italy). Dipt. di Scienza dei Materiali e Ingegneria Chimica; Musso, M. [Stampal, Via Lombardia 6,10071 Borgaro Torinese, Torino (Italy); Dinardo, P. [Consorzio Ricerche Compositi, Via Bona 85, 00156, Rome (Italy)

    2000-05-15

    Thermal fatigue behaviour of a 2014/Saffil composite has been investigated. This composite was produced by infiltration of preforms of Saffil fibers (Al{sub 2}O{sub 3}-SiO{sub 2} fibers) with a 2014 aluminium alloy (Al-4.7Cu-1.0Si-0.6 Mg). The composite samples, containing 13 vol.% of fibers, were sectioned and their microstructure was investigated by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Tensile tests, hardness and microhardness measurements were carried out. The fracture surfaces were examined by SEM. Dilatometry was used in order to measure the thermal expansion coefficient (CTE) and to evaluate the strength of matrix/fiber bonds. Thermal cycling tests were performed on specimens (either as fabricated or in the T6 temper) in the temperature range between 25 and 220 C. After 1000 cycles both the microstructure and the mechanical characteristics of the composite samples were investigated. The thermal fatigue resulted in a damage of the composite because of the partial fragmentation of the fibers. In addition, other phenomena involving the modification of composite matrix microstructure, such as over-aging of T6 treated samples and precipitation of strengthening phases within the matrix of as-cast samples, were observed. Thermal cycling also resulted in interfacial matrix/fiber reaction, which probably strengthened the composite and caused a CTE decrease. All these phenomena concurred to change both tensile behaviour and material hardness. (orig.)

  13. Effects of thermal fatigue on shear punch strength of tooth-colored restoratives

    Science.gov (United States)

    Melody, Fam Mei Shi; U-Jin, Yap Adrian; Natalie, Tan Wei Min; Elizabeth, Tay Wan Ling; Chien, Jessica Yeo Siu

    2016-01-01

    Aims: This study investigated the effect of thermal fatigue on the shear strength of a range of tooth-colored restorative materials including giomers, zirconia-reinforced glass ionomer cement (GIC), nano-particle resin-modified GIC, highly viscous GICs, and composite resin. Materials and Methods: Twenty specimens of each material were fabricated in standardized washers (17 mm outer diameter, 9 mm internal diameter, 1 mm thick). The specimens were cured, stored in 100% humidity at 37.5°C for 24 h, and randomly divided into two groups of 10. Group A specimens were nonthermocycled (NT) and stored in distilled water at 37°C for 168 h. Group B specimens were thermocycled (TC) for 10,000 cycles (168 h) with baths X, Y, and Z adjusted to 35°C, 15°C, and 45°C, respectively. Each cycle had dwell times of 28 s in X, and 2s in Y/Z in the order XYXZ. Specimens then underwent shear punch testing at a crosshead speed of 0.5 mm/min with a 2 kN load cell. Statistical analysis of shear strength was done using t-test and two-way ANOVA/Scheffe's post hoc test at significance level P < 0.05. Results: The effect of thermal fatigue on shear strength was material dependent. Except for the “sculptable” giomer (Beautifil II) and a highly viscous GIC (Fuji IX GP Fast), no significant differences in shear strength were generally observed between the NT and TC groups. For both groups, the composite resin (Filtek Z250XT) had the highest shear strength while the zirconia-reinforced (zirconomer) and a highly viscous GIC (Ketac Molar Quick) had the lowest. Conclusions: The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The “sculptable” composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the “flowable” injectable hybrid giomer was intermediate between the composite and GICs. PMID:27563182

  14. Thermal fatigue life evaluation of SnAgCu solder joints in a multi-chip power module

    Science.gov (United States)

    Barbagallo, C.; Malgioglio, G. L.; Petrone, G.; Cammarata, G.

    2017-05-01

    For power devices, the reliability of thermal fatigue induced by thermal cycling has been prioritized as an important concern. The main target of this work is to apply a numerical procedure to assess the fatigue life for lead-free solder joints, that represent, in general, the weakest part of the electronic modules. Starting from a real multi-chip power module, FE-based models were built-up by considering different conditions in model implementation in order to simulate, from one hand, the worst working condition for the module and, from another one, the module standing into a climatic test room performing thermal cycles. Simulations were carried-out both in steady and transient conditions in order to estimate the module thermal maps, the stress-strain distributions, the effective plastic strain distributions and finally to assess the number of cycles to failure of the constitutive solder layers.

  15. Heat losses in power boilers caused by thermal bridges

    Directory of Open Access Journals (Sweden)

    Kocot Monika

    2017-01-01

    Full Text Available In this article the analysis of heat losses caused by thermal bridges that occur in the steam boiler OP-140 is presented. Identification of these bridges were conducted with use of thermographic camera. Heat losses were evaluated based on methodology of VDI 4610 standard, but instead of its simplified equations, criterial equations based on Nusselt number were used. Obtained values of annual heat losses and heat flux density corresponding to the fully insulated boiler surfaces were compared to heat losses generated by thermal bridges located in the same areas. The emphasis is put on the role of industrial insulation in heat losses reduction.

  16. Effects of MC-Type Carbide Forming and Graphitizing Elements on Thermal Fatigue Behavior of Indefinite Chilled Cast Iron Rolls

    Science.gov (United States)

    Ahiale, Godwin Kwame; Choi, Won-Doo; Suh, Yongchan; Lee, Young-Kook; Oh, Yong-Jun

    2015-11-01

    The thermal fatigue behavior of indefinite chilled cast iron rolls with various V+Nb contents and Si/Cr ratios was evaluated. Increasing the ratio of Si/Cr prolonged the life of the rolls by reducing brittle cementites. Higher V+Nb addition also increased the life through the formation of carbides that refined and toughened the martensite matrix and reduced the thermal expansion mismatch in the microstructure.

  17. Cyclic fatigue and torsional strength of three different thermally treated reciprocating nickel-titanium instruments.

    Science.gov (United States)

    Alcalde, Murilo Priori; Duarte, Marco Antonio Hungaro; Bramante, Clovis Monteiro; de Vasconselos, Bruno Carvalho; Tanomaru-Filho, Mario; Guerreiro-Tanomaru, Juliane Maria; Pinto, Jader Camilo; Só, Marcus Vinicius Reis; Vivan, Rodrigo Ricci

    2017-12-09

    The aim of this study was to evaluate the cyclic and torsional fatigue resistance of the reciprocating single-file systems Reciproc Blue 25.08 (VDW GmbH, Munich, Germany), Prodesign R 25.06 (Easy Dental Equipment, Belo Horizonte, Brazil), and WaveOne Gold 25.07 (Dentsply/Tulsa Dental Specialties, Tulsa, OK, USA). Sixty reciprocating instruments of the systems Reciproc Blue R25 (RB #25 .08 taper), Prodesign R (PDR #25 .06 taper), and WaveOne Gold (WOG #25 .07 taper) (n = 20) were used. Cyclic fatigue resistance testing was performed by measuring the time to failure in an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius located 5 mm from the tip (n = 10). The torsional test (ISO 3630-1) evaluated the torque and angle of rotation at failure of new instruments (n = 10) in the portion 3 mm from the tip. The fractured surface of each fragment was also observed using scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area of each instrument 3 and 5 mm from the tip. The data were analyzed using one-way ANOVA and Tukey's test, and the level of significance was set at 5%. The cyclic fatigue resistance values of PDR 25.06 were significantly higher (P  0.05). PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07 (P < 0.05). RB 25.08 presented higher angular rotation than WOG 25.07 (P < 0.05). The cross-sectional area analysis showed that PDR 25.06 presented the smallest cross-sectional areas at 3 and 5 mm from the tip (P < 0.05). PDR 25.06 presented the highest cyclic fatigue resistance and angular rotation until fracture compared to RB 25.08 and WOG 25.07. In addition, RB 25.08 and WOG 25.07 had higher torsional strength than PDR 25.06. In endodontic practice, thermally treated reciprocating instruments have been used for the root canal preparation of curved and constricted canals; therefore, these instruments should

  18. Study of the damage processes induced by thermal fatigue in stainless steels F17TNb and R20-12 for automobile application; Etude de l'endommagement en fatigue thermique des aciers inoxydables F17TNb et R20-12 pour application automobile

    Energy Technology Data Exchange (ETDEWEB)

    Bucher, L.

    2004-12-15

    Thermal cycling is the main cause of fatigue failure in automobile exhaust manifolds for which the use of stainless steel now rivals that of cast iron which has been traditionally used. An original fatigue test has been developed by Ugine and ALZ, a stainless steel producer, so as to be able to compare different grades of stainless steel alloys. This test is representative of the thermal conditions encountered in the critical zones of exhaust manifolds. However, it has revealed significant differences in damage processes in the ferritic and austenitic grades tested. The subject of this thesis is the damage processes induced by thermal fatigue in stainless steels used for automotive exhaust manifolds. Two stainless steels were studied: a ferritic grade, F17TNb (17%Cr and stabilized with Ti and Nb), and an austenitic grade, R20-12, containing 20% Cr and 12% Ni. The first objective was to understand the different damage processes induced by thermal fatigue in the ferritic and austenitic grades. The second was to develop a numerical design tool of the thermally tested structures. (author)

  19. Towards the prediction of thermal fatigue cracks networks development; Vers la prediction de l'apparition de reseau de fissures en fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Osterstock, St. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMA), 91 - Gif-sur-Yvette (France)

    2008-07-01

    In the framework of the influence of the surface and the structure of materials used in the cooling system of reactor, Depres studied in 2004 at the CEA, the evolution of the microstructure inside the surface grains under a thermal fatigue loading, from dynamic of dislocations calculation. In this context the aim of this study is to bring experimental elements of validation of the numerical results obtained by Depres and to verify if these elements allow the prediction of cracks networks apparition. (A.L.B.)

  20. Structural Technology Evaluation Analysis Program (STEAP). Task Order 0029: Thermal Stability of Fatigue Life-Enhanced Structures

    Science.gov (United States)

    2012-01-01

    thermal and mechanical effects. When studying the residual stress relaxation behavior of AISI 4140 steel under conventional fatigue at elevated...Vohringer and 28. E. Macherauch, “Residual stress relaxation in an AISI 4140 steel due to quasistatic and cyclic loading at higher temperatures...temperature,” Mater. Sci. Engr., A366, 412- 420 (2004). 30. W. Cao, M. Khadhraoui, B. Brenier, J.Y. Guedou and L. Castex, “Thermomechanical relaxation

  1. Subjective sensation on sleep, fatigue, and thermal comfort in winter shelter-analogue settings

    Science.gov (United States)

    Maeda, Kazuki; Mochizuki, Yosuke; Tsuzuki, Kazuyo; Nabeshima, Yuki

    2017-10-01

    We aimed to examine sleep in shelter-analogue settings in winter to determine the subjective sensation and environmental conditions in evacuation shelters. Twelve young healthy students took part in the sleep study of two nights for seven hours from Midnight to 7 AM in the gymnasium. One night the subject used a pair of futons and on the other the subject used the emergency supplies of four blankets and a set of portable partitions. During the night, air temperature, humidity and air velocity were measured in the area around the sleeping subjects. Sleep parameters measured by actigraphy, skin temperature, microclimate temperature, rectal temperature, and the heart rates of the subjects were continuously measured and recorded during the sleeping period. The subjects completed questionnaires regarding their thermal comfort and subjective sleep before and after the sleep. The subjects felt more coldness on their head and peripheral parts of the body using the emergency blankets than the futon during the sleep. Moreover, fatigue was felt more on the lower back and lower extremities from using emergency blankets than the futon after sleep. However, the sleep efficiency index and subjective sleep evaluation by OSA questionnaire did not reveal any good correlationship. The emergency supplies should be examined for their suitability to provide comfortable and healthy sleep in the shelter-analogue settings.

  2. Effect of composition and processing on the thermal fatigue and toughness of high performance die steels. Year 1 report

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, J.F.; Wang, Yumin; Schwam, D.

    1996-06-01

    The goal of this project is to extend the lifetime of dies for die casting by 20%. Since the die contributes about 10% to the cost of die cast parts, such an improvement in lifetime would result in annual savings of over $200 Million dollars. This is based on the estimated annual die production of one Billion dollars in the US. The major tasks of this two year project are: (1) Evaluate NEW DIE STEEL COMPOSITIONS that have been developed for demanding applications and compare them to Premium Grade H-13 die steel. (2) Optimize the AUSTENITIZING TREATMENT of the new composition. Assess the effects of fast, medium and slow COOLING RATES DURING HEAT TREATMENT, on the thermal fatigue resistance and toughness of the die steel. (3) Determine the effect of ELECTRO-DISCHARGE MACHINING (EDM) on the thermal fatigue resistance and impact properties of the steel. (4) Select demanding components and conduct IN-PLANT TESTING by using the new steel. Compare the performance of the new steel with identical components made of Premium Grade H-13. The immersion thermal fatigue specimen developed at CWRU is being used to determine resistance to heat checking, and the Charpy V-notch test for evaluating the toughness. The overall result of this project will be identification of the best steel available on the market and the best processing methods for aluminum die casting dies. This is an interim report for year 1 of the project.

  3. Estimate of thermal fatigue lifetime for the INCONEL 625lCF plate while exposed to concentrated solar radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Morin, A.; Fernandez-Reche, J.

    2011-07-01

    A system for testing the thermal cycling of materials and components has been developed and installed at the DISTAL-I parabolic dish facility located at the Plataforma Solar de Almeria (PSA) in Spain. This system allows us to perform abrupt heating/cooling tests by exposing central solar receiver materials to concentrated solar radiation. These tests are performed to simulate both the normal and critical operational conditions of the central solar receiver. The thermal fatigue life for the INCONEL 625LCF plate when subjected to concentrated solar radiation has been estimated with this system. We have also developed a numerical model that evaluates the thermal behavior of the plate material; additionally, the model yields the tensile-compressive stresses on the plate, which allow the estimation of the Stress-Life (S-N) fatigue curves. These curves show that the lifetime of the plate is within the High Cycle Fatigue (HCF) region at the operational temperatures of both 650 degree centigrade and 900 degree centigrade. (Author) 20 refs.

  4. Side Effects: Fatigue

    Science.gov (United States)

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  5. Effect of viewing distance on 3D fatigue caused by viewing mobile 3D content

    Science.gov (United States)

    Mun, Sungchul; Lee, Dong-Su; Park, Min-Chul; Yano, Sumio

    2013-05-01

    With an advent of autostereoscopic display technique and increased needs for smart phones, there has been a significant growth in mobile TV markets. The rapid growth in technical, economical, and social aspects has encouraged 3D TV manufacturers to apply 3D rendering technology to mobile devices so that people have more opportunities to come into contact with many 3D content anytime and anywhere. Even if the mobile 3D technology leads to the current market growth, there is an important thing to consider for consistent development and growth in the display market. To put it briefly, human factors linked to mobile 3D viewing should be taken into consideration before developing mobile 3D technology. Many studies have investigated whether mobile 3D viewing causes undesirable biomedical effects such as motion sickness and visual fatigue, but few have examined main factors adversely affecting human health. Viewing distance is considered one of the main factors to establish optimized viewing environments from a viewer's point of view. Thus, in an effort to determine human-friendly viewing environments, this study aims to investigate the effect of viewing distance on human visual system when exposing to mobile 3D environments. Recording and analyzing brainwaves before and after watching mobile 3D content, we explore how viewing distance affects viewing experience from physiological and psychological perspectives. Results obtained in this study are expected to provide viewing guidelines for viewers, help ensure viewers against undesirable 3D effects, and lead to make gradual progress towards a human-friendly mobile 3D viewing.

  6. System-Level Heat Transfer Analysis, Thermal- Mechanical Cyclic Stress Analysis, and Environmental Fatigue Modeling of a Two-Loop Pressurized Water Reactor. A Preliminary Study

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish [Argonne National Lab. (ANL), Argonne, IL (United States); Soppet, William [Argonne National Lab. (ANL), Argonne, IL (United States); Majumdar, Saurin [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, Ken [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-01-03

    This report provides an update on an assessment of environmentally assisted fatigue for light water reactor components under extended service conditions. This report is a deliverable in April 2015 under the work package for environmentally assisted fatigue under DOE's Light Water Reactor Sustainability program. In this report, updates are discussed related to a system level preliminary finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent thermal-mechanical stress analysis were performed for typical design-basis thermal-mechanical fatigue cycles. The in-air fatigue lives of components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described in NUREG-6909. The discussed models and results are very preliminary. Further advancement of the discussed model is required for more accurate life prediction of reactor components. This report only presents the work related to finite element modelling activities. However, in between multiple tensile and fatigue tests were conducted. The related experimental results will be presented in the year-end report.

  7. Postdialysis fatigue.

    Science.gov (United States)

    Sklar, A H; Riesenberg, L A; Silber, A K; Ahmed, W; Ali, A

    1996-11-01

    To clarify the demographic and clinicolaboratory features of postdialysis fatigue (PDF), we enrolled 85 patients on maintenance hemodialysis in a cross-sectional study using validated questionnaires and chart review. Forty-three patients complained of fatigue after dialysis. On formal testing using the Kidney Disease Questionnaire, the PDF group had statistically greater severity of fatigue and somatic complaints than the group of patients without subjective fatigue (P = 0.03 and 0.04, respectively). On a scale measuring intensity of fatigue (1 = least to 5 = worst), the PDF group average was 3.4 +/- 1.2. PDF subjects reported that 80% +/- 25% of dialysis treatments were followed by fatigue symptoms. In 28 (65%) of patients, the symptoms started with the first dialysis treatment. They reported needing an average of 4.8 hours of rest or sleep to overcome the fatigue symptoms (range, 0 to 24 hours). There were no significant differences between patients with and without PDF in the following parameters: age; sex; type of renal disease; presence of diabetes mellitus, heart disease (congestive, ischemic), or chronic obstructive lung disease; blood pressure response to dialysis; type or adequacy of dialysis regimen; hematocrit; electrolytes; blood urea nitrogen; creatinine; cholesterol; albumin; parathyroid hormone; ejection fraction; and use of antihistamines, benzodiazepines, and narcotics. In the fatigue group, there was significantly greater use of antihypertensive medications known to have fatigue as a side effect (P = 0.007). Depression was more common in the fatigue group by Beck Depression score (11.6 +/- 8.0 v 7.8 +/- 6.3; P = 0.02). We conclude that (1) postdialysis fatigue is a common, often incapacitating symptom in patients on chronic extracorporeal dialysis; (2) no routinely measured parameter of clinical or dialytic function appears to predict postdialysis fatigue; and (3) depression is highly associated with postdialysis fatigue, but the cause

  8. A hydro-thermo-mechanics analyze of the thermal fatigue in the mixing tee junction

    Energy Technology Data Exchange (ETDEWEB)

    Gourdin, C.; Chapuliot, S. [CEA Saclay, Dir. de l' Energie Nucleaire, (DEN/DM2S/SEMT/LISN), 91 - Gif sur Yvette (France); Magnaud, J.P. [CEA Saclay, Dir. de l' Energie Nucleaire (DEN/DM2S/SFME/LTMF), 91 - Gif sur Yvette (France); Payen, T. [Institut de Radioprotection et de Surete Nucleaire (IRSN/DES/SAMS), 92 - 92 - Fontenay aux Roses (France)

    2003-07-01

    Work presented here, has been achieved at Cea, and is related to the comprehension of the mechanisms leading to cracking under thermal loading in the zones of mixing. The main objective of this work is to analyze, by computation, the thermal loading induced by the turbulent mixing following a tee junction and to explain how it can create cracking, from the internal skin of the component to a leakage, as it was observed in Civaux Power Plant in 1998. The phenomenon is still today not completely understood. One of the principal reasons to this partial incomprehension undoubtedly resides in the multi-field aspect of the loading and of the associated damage, utilizing three different and complementary scientific disciplines: thermohydraulics, thermomechanics and material science. The presentation proposed here, consists in connecting the analyses resulting from these various fields. The first part concentrates on thermohydraulics simulations. The choice of an adequate modeling is discussed on the basis of observed cracking in order to highlight phenomena of large scale beats, which are supposed one of the major causes leading to the failure of the structures. The second part deals with the use of the temperature fields obtained in the first part in order to carry out thermomechanical simulations. All these simulations are 3-dimensional and represent the complex geometry of Civaux RRA piping line, including a tee junction and elbows, water flow velocity. Mean and temperatures variations, mean and stresses variations are also presented. As final results make it possible to determine a map of the damage associated with these complex thermal loading. (authors)

  9. A heavy heart; A massive right atrial myxoma causing fatigue and shortness of breath.

    LENUS (Irish Health Repository)

    Leonard, S

    2010-03-01

    Cardiac myxomas are rare. The clinical diagnosis of an atrial myxoma may occur in an asymptomatic patient but may also present with cardiac failure, syncope, arrythmias, or with vascular evidence of tumour embolisation. The delay in diagnosis from presentation is approximately ten months. We present the case of a 53-year-old woman who attended our Emergency Department with dyspnoea, fatigue and left sided chest pain. Investigations revealed a massive right atrial myxoma. The tumour was resected successfully. Emergency Physicians should be aware of the subtle ways in which an atrial myxoma can present because of the potential for fatal outcomes.

  10. Thermal bridges. Causes and impacts, information on reduction and avoidance; Waermebruecken. Ursachen und Auswirkungen, Hinweise zur Verringerung und Vermeidung

    Energy Technology Data Exchange (ETDEWEB)

    Feist, Wolfgang; Born, Rolf

    2012-11-15

    Thermal bridges increase the heat demand, affect the thermal comfort, facilitate mould cultures and cause structural damage. Many thermal bridges can be avoided by proper building construction details. At least the impact of thermal bridges can be avoided.

  11. Comparison between FEM and high heat flux thermal fatigue testing results of ITER divertor plasma facing mock-ups

    Energy Technology Data Exchange (ETDEWEB)

    Crescenzi, F., E-mail: fabio.crescenzi@enea.it; Roccella, S.; Visca, E.; Moriani, A.

    2014-10-15

    Highlights: • Divertor is an important part of the ITER machine. • Finite element analysis allows designers to explore multiple design options, reducing physical prototypes and optimizing design performance. • The hydraulic thermal-mechanical analysis performed by ANSYS and the test results on small-scale mock-ups manufactured by HRP were compared. • FEA results confirmed many experimental data, then it could be very useful for next design optimization. - Abstract: The divertor is one of the most challenging components of “DEMO” the next step ITER machine, so many tasks regarding modeling and experiments have been made in the past years to assess manufacturing processes, materials and thus the life-time of the components. In this context the finite element analysis (FEA) allows designers to explore multiple design options, to reduce physical prototypes and to optimize design performance. The comparison between the hydraulic thermal-mechanical analysis performed by ANSYS WORKBENCH 14.5 and the test results [1] on small-scale mock-ups manufactured with the Hot Radial Pressing (HRP) [2] technology is presented in this paper. During the thermal fatigue testing in the Efremov TSEFEY facility to assess the heat flux load-carrying capability of the mock-ups, only the surface temperature was measured, so the FEA was important because it allowed to know any other information (temperature inside the materials, local water temperature, local stress, etc.). FEA was performed coupling the thermal-hydraulic analysis, that calculated the temperature distributions on the components and the heat transfer coefficient (HTC) between water and heat sink tube, with the mechanical analysis. The comparison between analysis and testing results was based on the temperature maps of the loaded surface and on number of the cycles supported during the testing and those predicted by the mechanical analysis using the experimental fatigue curves for CuCrZr-IG, that is the structural

  12. Study of the quantitative assessment method for high-cycle thermal fatigue of a T-pipe under turbulent fluid mixing based on the coupled CFD-FEM method and the rainflow counting method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Lu, T., E-mail: likesurge@sina.com

    2016-12-01

    Highlights: • Two characteristic parameters of the temperature fluctuations are used for qualitative analysis. • A quantitative assessment method for high-cycle thermal fatigue of a T-pipe is proposed. • The time-dependent curves for the temperature and thermal stress are not always “in-phase”. • Large magnitude of thermal stresses may not mean large number of fatigue cycles. • The normalized fatigue damage rate and normalized RMS temperature are positively related. - Abstract: With the development of nuclear power and nuclear power safety, high-cycle thermal fatigue of the pipe structures induced by the flow and heat transfer of the fluid in pipes have aroused more and more attentions. Turbulent mixing of hot and cold flows in a T-pipe is a well-recognized source of thermal fatigue in piping system, and thermal fatigue is a significant long-term degradation mechanism. It is not an easy work to evaluate thermal fatigue of a T-pipe under turbulent flow mixing because of the thermal loads acting at fluid–structure interface of the pipe are so complex and changeful. In this paper, a one-way Computational Fluid Dynamics-Finite Element Method (CFD-FEM method) coupling based on the ANSYS Workbench 15.0 software has been developed to calculate transient thermal stresses with the temperature fields of turbulent flow mixing, and thermal fatigue assessment has been carried out with this obtained fluctuating thermal stresses by programming in the software platform of Matlab based on the rainflow counting method. In the thermal analysis, the normalized mean temperatures and the normalized root mean square (RMS) temperatures are obtained and compared with the experiment of the test case from the Vattenfall benchmark facility to verify the accuracy of the CFD calculation and to determine the position which thermal fatigue is most likely to occur in the T-junction. Besides, more insights have been obtained in the coupled CFD-FEM analysis and the thermal fatigue

  13. Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes

    Directory of Open Access Journals (Sweden)

    Aoki Kosuke

    2012-07-01

    Full Text Available Abstract Background Muscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW on oxidative stress and muscle fatigue in response to acute exercise. Methods Ten male soccer players aged 20.9 ± 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO2 for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured. Results Although acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn’t decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP or creatine kinease after exercise. Conclusion Adequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes.

  14. Estimate of thermal fatigue lifetime for the INCONEL 625lCF plate while exposed to concentrated solar radiation

    Directory of Open Access Journals (Sweden)

    Rojas-Morín, A.

    2011-04-01

    Full Text Available A system for testing the thermal cycling of materials and components has been developed and installed at the DISTAL-I parabolic dish facility located at the Plataforma Solar de Almería (PSA in Spain. This system allows us to perform abrupt heating/cooling tests by exposing central solar receiver materials to concentrated solar radiation. These tests are performed to simulate both the normal and critical operational conditions of the central solar receiver. The thermal fatigue life for the INCONEL 625LCF® plate when subjected to concentrated solar radiation has been estimated with this system. We have also developed a numerical model that evaluates the thermal behavior of the plate material; additionally, the model yields the tensile-compressive stresses on the plate, which allow the estimation of the Stress-Life (S-N fatigue curves. These curves show that the lifetime of the plate is within the High Cycle Fatigue (HCF region at the operational temperatures of both 650 °C and 900 °C.

    En el concentrador solar de disco parabólico DISTAL-I, situado en la Plataforma Solar de Almería (PSA, en España, se ha instalado un sistema para pruebas de ciclado térmico de materiales. Este sistema permite realizar pruebas abruptas de calentamiento y enfriamiento, en materiales para receptores solares de torre central, al exponerlos a radiación solar concentrada. Estas pruebas se realizan para simular las condiciones de operación de un receptor solar, las condiciones críticas y las condiciones normales. Con este sistema se ha estimado el tiempo de vida bajo fatiga térmica, en una placa de INCONEL 626LCF®, cuando es sometida a radiación solar concentrada. Asimismo, hemos desarrollado un modelo numérico que evalúa el desarrollo térmico en el material de la placa: adicionalmente, el modelo obtiene los esfuerzos de tensión-compresión en la placa, los cuales permiten la estimaciónde las curvas de fatiga vidaesfuerzo (S-N. Estas curvas

  15. Four-wall turbine airfoil with thermal strain control for reduced cycle fatigue

    Science.gov (United States)

    Cambell, Christian X

    2013-09-17

    A turbine airfoil (20B) with a thermal expansion control mechanism that increases the airfoil camber (60, 61) under operational heating. The airfoil has four-wall geometry, including pressure side outer and inner walls (26, 28B), and suction side outer and inner walls (32, 34B). It has near-wall cooling channels (31F, 31A, 33F, 33A) between the outer and inner walls. A cooling fluid flow pattern (50C, 50W, 50H) in the airfoil causes the pressure side inner wall (28B) to increase in curvature under operational heating. The pressure side inner wall (28B) is thicker than walls (26, 34B) that oppose it in camber deformation, so it dominates them in collaboration with the suction side outer wall (32), and the airfoil camber increases. This reduces and relocates a maximum stress area (47) from the suction side outer wall (32) to the suction side inner wall (34B, 72) and the pressure side outer wall (26).

  16. Thermal-structural Analysis and Fatigue Life Evaluation of a Parallel Slide Gate Valve in Accordance with ASME B and PVC

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Ho; Han, Jeong Sam [Andong Nat’l Univ., Andong (Korea, Republic of); Jae Seung Choi [Key Valve Technologies Ltd., Siheung (Korea, Republic of)

    2017-02-15

    A parallel slide gate valve (PSGV) is located between the heat recovery steam generator (HRSG) and the steam turbine in a combined cycle power plant (CCPP). It is used to control the flow of steam and runs with repetitive operations such as startups, load changes, and shutdowns during its operation period. Therefore, it is necessary to evaluate the fatigue damage and the structural integrity under a large compressive thermal stress due to the temperature difference through the valve wall thickness during the startup operations. In this paper, the thermal-structural analysis and the fatigue life evaluation of a 16-inch PSGV, which is installed on the HP steam line, is performed according to the fatigue life assessment method described in the ASME B and PVC VIII-2; the method uses the equivalent stress from the elastic stress analysis.

  17. The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure

    Science.gov (United States)

    Rizzi, Stephen A.; Behnke, marlana N.; Przekop, Adam

    2010-01-01

    High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.

  18. Less is more: standard warm-up causes fatigue and less warm-up permits greater cycling power output.

    Science.gov (United States)

    Tomaras, Elias K; MacIntosh, Brian R

    2011-07-01

    The traditional warm-up (WU) used by athletes to prepare for a sprint track cycling event involves a general WU followed by a series of brief sprints lasting ≥ 50 min in total. A WU of this duration and intensity could cause significant fatigue and impair subsequent performance. The purpose of this research was to compare a traditional WU with an experimental WU and examine the consequences of traditional and experimental WU on the 30-s Wingate test and electrically elicited twitch contractions. The traditional WU began with 20 min of cycling with a gradual intensity increase from 60% to 95% of maximal heart rate; then four sprints were performed at 8-min intervals. The experimental WU was shorter with less high-intensity exercise: intensity increased from 60% to 70% of maximal heart rate over 15 min; then just one sprint was performed. The Wingate test was conducted with a 1-min lead-in at 80% of optimal cadence followed by a Wingate test at optimal cadence. Peak active twitch torque was significantly lower after the traditional than experimental WU (86.5 ± 3.3% vs. 94.6 ± 2.4%, P track cyclist's WU results in significant fatigue, which corresponds with impaired peak power output. A shorter and lower-intensity WU permits a better performance.

  19. Study on sand particles creep model and open pit mine landslide mechanism caused by sand fatigue liquefaction

    Science.gov (United States)

    Du, Dong-Ning; Wang, Lai-Gui; Zhang, Xiang-Dong; Zhang, Shu-Kun

    2017-06-01

    The sand particles in the sand - rock composite slope of the open pit mine occurs creep deformation and fatigue liquefaction under the action of vehicle load vibration and hydraulic gradient, which causes landslide geological disasters and it destroys the surface environment. To reveal the mechanism, a mechanics model based on the model considering the soil structural change with a new “plastic hinge” element is developed, to improve its constitutive and creep curve equations. Data from sand creep experiments are used to identify the parameters in the model and to validate the model. The results show that the mechanical model can describe the rotation progress between the sand particles, disclose the negative acceleration creep deformation stage during the third phase, and require fewer parameters while maintaining accuracy. It provides a new creep model considering rotation to analyze sand creep mechanism, which provides a theoretical basis for revealing the open pit mine landslide mechanism induced by creep deformation and fatigue liquefaction of sandy soil.

  20. 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

    Science.gov (United States)

    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.

  1. Impacts of weld residual stresses and fatigue crack growth threshold on crack arrest under high-cycle thermal fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, Said, E-mail: Said.taheri@edf.fr [EDF-LAB, IMSIA, 7 Boulevard Gaspard Monge, 91120 Palaiseau Cedex (France); Julan, Emricka [EDF-LAB, AMA, 7 Boulevard Gaspard Monge, 91120 Palaiseau Cedex (France); Tran, Xuan-Van [EDF Energy R& D UK Centre/School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom); Robert, Nicolas [EDF-DPN, UNIE, Strategic Center, Saint Denis (France)

    2017-01-15

    Highlights: • For crack growth analysis, weld residual stress field must be considered through its SIF in presence of a crack. • Presence of cracks of same depth proves their arrest, where equal depth is because mean stress acts only on crack opening. • Not considering amplitudes under a fatigue crack growth threshold (FCGT) does not compensate the lack of FGCT in Paris law. • Propagation rates are close for axisymmetric and circumferential semi-elliptical cracks. - Abstract: High cycle thermal crazing has been observed in some residual heat removal (RHR) systems made of 304 stainless steel in PWR nuclear plants. This paper deals with two types of analyses including logical argumentation and simulation. Crack arrest in networks is demonstrated due to the presence of two cracks of the same depth in the network. This identical depth may be proved assuming that mean stress acts only on crack opening and that cracks are fully open during the load cycle before arrest. Weld residual stresses (WRS) are obtained by an axisymmetric simulation of welding on a tube with a chamfer. Axisymmetric and 3D parametric studies of crack growth on: representative sequences for variable amplitude thermal loading, fatigue crack growth threshold (FCGT), permanent mean stress, cyclic counting methods and WRS, are performed with Code-Aster software using XFEM methodology. The following results are obtained on crack depth versus time: the effect of WRS on crack growth cannot be determined by the initial WRS field in absence of crack, but by the associated stress intensity factor. Moreover the relation between crack arrest depth and WRS is analyzed. In the absence of FCGT Paris’s law may give a significant over-estimation of crack depth even if amplitudes of loading smaller than FCGT have not been considered. Appropriate depth versus time may be obtained using different values of FCGT, but axisymmetric simulations do not really show a possibility of arrest for shallow cracks in

  2. Inhaled β-agonist therapy and respiratory muscle fatigue as under-recognised causes of lactic acidosis.

    Science.gov (United States)

    Lau, Emily; Mazer, Jeffrey; Carino, Gerardo

    2013-10-14

    A 49-year-old man with chronic obstructive pulmonary disease (COPD) presented with significant tachypnoea, fevers, productive cough and increased work of breathing for the previous 4 days. Laboratory data showed elevated lactate of 3.2 mEq/L. Continuous inhaled ipratropium and albuterol nebuliser treatments were administered. Lactate levels increased to 5.5 and 3.9 mEq/L, at 6 and 12 h, respectively. No infectious source was found and the lactic acidosis cleared as the patient improved. The lactic acidosis was determined to be secondary to respiratory muscle fatigue and inhaled β-agonist therapy, two under-recognised causes of lactic acidosis in patients presenting with respiratory distress. Lactic acidosis is commonly used as a clinical marker for sepsis and shock, but in the absence of tissue hypoperfusion and severe hypoxia, alternative aetiologies for elevated levels should be sought to avoid unnecessary and potentially harmful medical interventions.

  3. Fatigue limit by thermal analysis of specimen surface in mono axial traction test

    Science.gov (United States)

    Risitano, A.; Giacomo, R.; Clienti, C.

    2010-06-01

    In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest) to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported. The corresponding value of stress was a good approximation of the fatigue limit for R = - 1, determined by the conventional method. The aim of the reported examples in this paper must be interpreted as support to the basic principle of the method and not as the results of a complete experimental planning of which we will comment in an another occasion.

  4. Fatigue limit by thermal analysis of specimen surface in mono axial traction test

    Directory of Open Access Journals (Sweden)

    Clienti C.

    2010-06-01

    Full Text Available In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported. The corresponding value of stress was a good approximation of the fatigue limit for R = - 1, determined by the conventional method. The aim of the reported examples in this paper must be interpreted as support to the basic principle of the method and not as the results of a complete experimental planning of which we will comment in an another occasion.

  5. Effect of Cyclic Thermal Loads on Fatigue Reliability in Polymer Matrix Composites

    Science.gov (United States)

    Chamis, Christos C.

    1997-01-01

    Technological solutions that will ensure the economic viability and environmental compatibility of a future High Speed Civil Transport plane are currently being sought. Lighter structural materials for both airframe primary structures and engine structure components are being investigated. We believe that such objectives can be achieved through the use of high-temperature composites as well as other conventional, lighter weight alloys. One of the prime issues for these structural components is assured long-term behavior with a specified reliability. An investigation was conducted to describe a computational simulation methodology for predicting fatigue life, reliability, and probabilistic long-term behavior of polymer matrix composites. A unified time-, stress-, and load-dependent Multi- Factor Interaction Equation (MFIE) model developed at the NASA Lewis Research Center was used to simulate the long-term behavior of polymer matrix composites.

  6. IMPACT OF THERMAL FATIGUE ON YOUNG’S MODULUS OF EPOXY ADHESIVES

    Directory of Open Access Journals (Sweden)

    Mariusz Kłonica

    2015-11-01

    Full Text Available The following paper presents a comparative analysis of two epoxy-based adhesives: Hysol 9466 and Hysol 3421, prior to and after thermal shock testing. The tests focused on determining Young’s modulus. Epoxy-based materials are among the most widespread adhesive materials used as universal structural adhesives. The prepared epoxy samples (Hysol 9466 and Hysol 3421 were subjected to thermal shock cycling tests, according to a specified programme, in a thermal shock testing chamber, at a temperature range –40 °C to +60 °C and in the number of 200 cycles. Conclusions from the tests are presented at the final stage of the paper.

  7. [Auditory fatigue].

    Science.gov (United States)

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

    Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.

  8. Thermal Behaviour and Fatigue Estimation of the Switching Regulator for the BTF Power Supply of DAFNE Injector

    CERN Document Server

    Chiusano, F

    2006-01-01

    The BTF power supply is used to extract from the beam transfer line the particles pulses coming from the LINAC which normally fill the DAFNE collider at Frascati INFN Lab. This new power converter has been designed to feed a bending magnet with 447 A at nominal conditions and with a total ramp up and down of 20 ms. This power converter can run either in pulsed mode or in a conventional DC current mode. In pulsed mode the flat top can be streched from 5  ms up to 960 ms allowing a multi-pulse extraction. The heart of the system is based on a static converter with an H bridge topology made of IGBTs with integrated free wheel diodes. On one hand this paper presents the analysis of the thermal behaviour, the fatigue estimation and the impact on the power converter life time. On the other hand the design of a forced air cooling system is presented with the final results.

  9. Deficiency of slow skeletal muscle troponin T causes atrophy of type I slow fibres and decreases tolerance to fatigue

    Science.gov (United States)

    Wei, Bin; Lu, Yingru; Jin, J-P

    2014-01-01

    The total loss of slow skeletal muscle troponin T (ssTnT encoded by TNNT1 gene) due to a nonsense mutation in codon Glu180 causes a lethal form of recessively inherited nemaline myopathy (Amish nemaline myopathy, ANM). To investigate the pathogenesis and muscle pathophysiology of ANM, we studied the phenotypes of partial and total loss of ssTnT in Tnnt1 gene targeted mice. An insertion of neomycin resistance cassette in intron 10 of Tnnt1 gene caused an approximately 60% decrease in ssTnT protein expression whereas cre-loxP-mediated deletion of exons 11–13 resulted in total loss of ssTnT, as seen in ANM muscles. In diaphragm and soleus muscles of the knockdown and knockout mouse models, we demonstrated that ssTnT deficiency resulted in significantly decreased levels of other slow fibre-specific myofilament proteins whereas fast fibre-specific myofilament proteins were increased correspondingly. Immunohistochemical studies revealed that ssTnT deficiency produced significantly smaller type I slow fibres and compensatory growth of type II fast fibres. Along with the slow fibre atrophy and the changes in myofilament protein isoform contents, ssTnT deficiency significantly reduced the tolerance to fatigue in soleus muscle. ssTnT-deficient soleus muscle also contains significant numbers of small-sized central nuclei type I fibres, indicating active regeneration. The data provide strong support for the essential role of ssTnT in skeletal muscle function and the causal effect of its loss in the pathology of ANM. This observation further supports the hypothesis that the function of slow fibres can be restored in ANM patients if a therapeutic supplement of ssTnT is achieved. PMID:24445317

  10. Full-Scale 3-D Finite Element Modeling of a Two-Loop Pressurized Water Reactor for Heat Transfer, Thermal-Mechanical Cyclic Stress Analysis, and Environmental Fatigue Life Estimation

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurindranath; Natesan, Krishnamurti

    2015-12-15

    This paper discusses a system-level finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent sequentially coupled thermal-mechanical stress analysis were performed for typical thermal-mechanical fatigue cycles. The in-air fatigue lives of example components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described in US-NRC report: NUREG-6909.

  11. Thermal fatigue behavior of C/C composites modified by SiC-MoSi{sub 2}-CrSi{sub 2} coating

    Energy Technology Data Exchange (ETDEWEB)

    Chu Yanhui [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Fu Qiangang, E-mail: fuqiangang@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Li Hejun; Li Kezhi [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China)

    2011-08-04

    Highlights: > The low-density C/C composites were modified by SiC-MoSi{sub 2}-CrSi{sub 2} multiphase coating by pack cementation. > The thermal fatigue behavior of the modified C/C composites was studied after undergoing thermal cycling for 20 times under the different environments. > The decrease of the flexural strength of the modified C/C composites during thermal cycle in air was primarily attributed to the partial oxidation of the modified C/C samples. - Abstract: Carbon/carbon (C/C) composites were modified by SiC-MoSi{sub 2}-CrSi{sub 2} multiphase coating by pack cementation, and their thermal fatigue behavior under thermal cycling in Ar and air environments was investigated. The modified C/C composites were characterized by scanning electron microscopy and X-ray diffraction. Results of tests show that, after 20-time thermal cycles between 1773 K and room temperature in Ar environment, the flexural strength of modified C/C samples decreased lightly and the percentage of remaining strength was 94.92%. While, after thermal cycling between 1773 K and room temperature in air for 20 times, the weight loss of modified C/C samples was 5.1%, and the flexural strength of the modified C/C samples reduced obviously and the percentage of remaining strength was only 75.22%. The fracture mode of modified C/C samples changed from a brittle behavior to a pseudo-plastic one as the service environment transformed from Ar to air. The decrease of the flexural strength during thermal cycle in air was primarily attributed to the partial oxidation of modified C/C samples.

  12. Fatigue damage in 20% cold-worked type 316L stainless steel under deuteron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, R. (CEC, Joint Research Centre, 21020, Ispra (Vatican City State, Holy See) (Italy))

    1994-09-01

    Type 316L stainless steel samples in 20% cold-worked conditions were exposed to fully reversed fatigue cycling in torsion at 400 C during an irradiation with 19 MeV deuterons. Fatigue tests were performed in the high cycle fatigue (HCF) range under continuous cycling and in the low cycle fatigue (LCF) range by imposing a hold-time at the minimum strain value. In comparison with tests under thermal conditions, an increase in the number of cycles to failure N[sub f] by a factor of 6 is observed for the HCF tests and a decrease in N[sub f], by more than an order of magnitude, for the LCF tests. The data are analyzed using a fatigue damage model: a fatigue damage parameter is defined and the change in this parameter caused by the different irradiation or loading conditions shows directly the effect of changed experimental conditions on the fatigue life. ((orig.))

  13. A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

    Science.gov (United States)

    Chan, Jacky Chi-Hung; Lam, Wai Han; Yam, Vivian Wing-Wah

    2014-12-10

    Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

  14. Impact of casing rotation on premium connection service life in horizontal thermal wells

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J.; Fan, C.; Tao, G.; Matthews, C.M. [C-FER Technologies (Canada)

    2011-07-01

    In the heavy oil industry, thermal recovery methods are often used to enhance oil recovery but thermal cycle loading can cause failure of casing connections. With thermal recovery methods, casing connections are submitted to bending cycles during casing installation and to thermal cycles thereafter and this results in fatigue damage to the connections. The aim of this paper is to review casing connection rotation bending fatigue assessments and relevant fatigue life prediction theorems. A methodology is presented herein for predicting connection fatigue damage under casing bending rotation loading conditions and is then applied to a design example. Results showed that the limited casing rotation occurring in the installation process had a small impact on the connection fatigue life and that the connections could withstand several under thermal cycles. This paper presented and applied a method to predict connection fatigue damage under casing bending rotation loading conditions.

  15. Study on the deterioration origin of thermomechanical contact fatigue

    Science.gov (United States)

    Tudose-Sandu-Ville, O. F.

    2016-08-01

    Thermomechanical wear is a complex phenomenon present in a number of industrial domains, such as rolling bearings, gears, friction wheels, rolling mill rollers. In this type of surface tribological deterioration, both fundamental and some peculiar wears are combined (abrasive, adhesive, corrosive wear and contact fatigue), with mechanical ant thermal causes. The present paper takes into account the contact fatigue type of deterioration, with both causes in mechanical variable load and the thermal tide action on the contact surface. There are some theories synthetically presented regarding the location of critical stresses in rolling contact fatigue. The Jacq thermal effect is briefly presented with some considerations concerning the temperature gradient in the metallic wall. The connection between the Jacq thermal anomaly and the thermomechanical contact fatigue is considered to be a new approach. Also, the same location for both mechanical and thermal critical stresses gives a strong support for the thermomechanical contact fatigue primary deterioration, according to the results obtained during the author's PhD research.

  16. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals.

    Science.gov (United States)

    Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M; Koike, Kazuhiko

    2014-01-01

    The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  17. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium from Corals.

    Directory of Open Access Journals (Sweden)

    Lisa Fujise

    Full Text Available The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium. Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae in aquaria under non-thermal stress (27°C and moderate thermal stress conditions (30°C, and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  18. Entropy analysis of flow and heat transfer caused by a moving plate with thermal radiation

    Energy Technology Data Exchange (ETDEWEB)

    Butt, Adnan Saeed; Ali, Asif [Quaid-i-Azam University, Islamabad (Pakistan)

    2014-01-15

    This study examines the effects of thermal radiation on entropy generation in flow and heat transfer caused by a moving plate. The equations that govern the flow and heat transfer phenomenon are solved numerically. Velocity and temperature profiles are obtained for the parameters involved in the problem. The expressions for the entropy generation number and the Bejan number are obtained based on the profiles. Graphs for velocity, temperature, the entropy generation number, and the Bejan number are plotted and discussed qualitatively.

  19. Seafarer fatigue

    DEFF Research Database (Denmark)

    Jepsen, Jørgen Riis; Zhao, Zhiwei; van Leeuwen, Wessel M. A.

    2015-01-01

    Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating...... and metabolic pathways to the development of chronic diseases that are particularly prevalent in seafarers. Conclusions: Taking into account the frequency of seafarer fatigue and the severity of its consequences, one should look into the efficacy of the current legislative framework and the industry’s...... compliance, the manning of the international merchant fleet, and optimised working, living and sleeping conditions at sea. Considering circumstances at sea, e.g. working in shifts and crossing time zones, that cannot be altered, further assessment of the potentials of preventive interventions including...

  20. Chemotherapy Necessitates Increased Immune Control of HHVs: A Cause of Persistent Inflammation Enabling Protracted Fatigue in Breast Cancer Survivors

    Science.gov (United States)

    2015-06-01

    We hypothesized that chemotherapy would iuduce a shift iu control of chronic luunan he1pes viruses (HHVs) iu breast cancer patients and that this...previously banked frozen PBMC and data from frozen samples proved unreliable given a lack of positive cytokine signal from positive conu·ol u·eated... Virus -Specific T Serum Fatigue Sta tus Sta tus ceU responses Cvtokines Score Cohort 1 14 Active Active X X X NIA Cohort 2 20 Active Previously r

  1. Accelerated fatigue testing of LM 19.1 blades

    Energy Technology Data Exchange (ETDEWEB)

    Dahl Kristensen, O.J.; Joergensen, E.R.

    2003-04-01

    A series of 19.1 metre wind turbine blades manufactured by LM Glasfiber A/S of Lunderskov, Denmark were subjected to a series of flapwise fatigue tests. The object of these fatigue tests is to evaluate the impact of an increased load on the blade in a fatigue test and to give information if it is possible to increase the load in fatigue test to shorten test time. The tests were carried out as a part of a project financed by the Danish Energy Agency. During the fatigue tests the blades have been surveyed with thermal imaging equipment to determine how an increase in fatigue load affects the blade material. In addition to the thermal imaging surveillance the blades were instrumented with strain gauges. This report presents the temperature during test, calibration test results, moment range measurements, strain statistics, thermal imaging registrations and a determination of the size and cause of the damages. The report is also giving information on the blade-to-blade variation. (au)

  2. Discrimination of plant stress caused by oil pollution and waterlogging using hyperspectral and thermal remote sensing

    Science.gov (United States)

    Emengini, Ebele Josephine; Blackburn, George Alan; Theobald, Julian Charles

    2013-01-01

    Remote sensing of plant stress holds promise for detecting environmental pollution by oil. However, in oil-rich delta regions, waterlogging is a frequent source of plant stress that has similar physiological effects to oil pollution. This study investigated the capabilities of remote sensing for discriminating between these two sources of plant stress. Bean plants were subjected to oil pollution, waterlogging, and combined oil and waterlogging treatments. Canopy physiological, hyperspectral, and thermal measurements were taken every two to three days after treatment to follow the stress responses. For plants treated with oil, spectral and thermal responses were evident six days before symptoms could be observed visually. In waterlogged plants, only spectral responses were observed, but these were present up to eight days before visual symptoms. A narrowband reflectance ratio was efficient in detecting stress caused by oil and waterlogging. Canopy temperature and a thermal index were good indicators of oil and combined oil and waterlogging stress, but insensitive to waterlogging alone. Hence, this study provides evidence that combined hyperspectral and thermal remote sensing of vegetation has potential for monitoring oil pollution in environments that are also subjected to waterlogging.

  3. STRESSES IN CEMENT-CONCRETE PAVEMENT SURFACING CAUSED BY THERMAL SHOCK

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2016-01-01

    Full Text Available It is necessary to mention specially so-called thermal shock among various impacts on highway surface. Ice layer is formed on a concrete surface during the winter period of pavement surfacing operation. Sodium chloride which lowers temperature of water-ice transition temperature and causes ice thawing at negative temperature is usually used to remove ice from the pavement surface. Consequently, temperature in the concrete laying immediately under a thawing ice layer is coming down with a run that leads to significant stresses. Such phenomenon is known as a thermal shock with a meaning of local significant change in temperature. This process is under investigation, it has practical importance for an estimation of strength and longevity of a cement-concrete pavement surfacing and consequently it is considered as rather topical issue. The purpose of investigations is to develop a mathematical model and determination of shock blow permissible gradients for a cementconcrete road covering. Finite difference method has been used in order to determine stressed and deformed condition of the cement-concrete pavement surfacing of highways. A computer program has been compiled and it permits to carry out calculation of a road covering at various laws of temperature distribution in its depth. Regularities in distribution of deformation and stresses in the cement-concrete pavement surfacing of highways at thermal shock have been obtained in the paper. A permissible parameter of temperature distribution in pavement surfacing thickness has been determined in the paper. A strength criterion based on the process of micro-crack formation and development in concrete has been used for making calculations. It has been established that the thermal shock causes significant temperature gradients on the cement-concrete surfacing that lead to rather large normal stresses in the concrete surface layer. The possibility of micro-crack formation in a road covering is

  4. Research on pollution caused by thermal power plants in Muğla

    OpenAIRE

    YOKAŞ, İbrahim; TUNA, A. Levent; BÜRÜN, Betül; Hakerlerler, Hüseyin; Kılınç, Rafet; Bülent, Yağmur; Sultan, Köşkeroğlu

    2009-01-01

    The paper studies the heavy metal pollution caused by Gökova (210 MWx3), Yeniköy (210 MWx2) and Yatagan (210 MWx3) Thermal Power Plants in Mugla. For this purpose, the heavy metal level of the leave and soil samples taken in each season from olives is stated. The minimum heavy metal level is found in Yatagan, and the maximum in Yeniköy. The heavy metal level of the soil samples generally increases in autumn. The level of the leave samples has generally its highest levels in winter...

  5. Prevalence, causes and consequences of compassion satisfaction and compassion fatigue in emergency care: a mixed-methods study of UK NHS Consultants.

    Science.gov (United States)

    Dasan, Sunil; Gohil, Poonam; Cornelius, Victoria; Taylor, Cath

    2015-08-01

    To estimate prevalence and explore potential causes and consequences of compassion satisfaction and compassion fatigue in UK emergency medicine consultants. A sequential mixed-methods design. Cross-sectional e-survey to all UK NHS emergency medicine consultants (n=1317) including Professional Quality of Life (ProQOL) (compassion satisfaction/fatigue), followed by interviews with consultants scoring above (n=6) and below (n=6) predefined ProQOL thresholds. 681 (52%) consultants responded. Most (98%) reported at least 'average' compassion satisfaction. Higher scores were associated with type of workplace (designated trauma centres faring better) and number of years worked as a consultant (gradually worsen over time, except 20 years onwards when it improves). Consultants with lower (worse) compassion satisfaction scores were more likely to report being irritable with patients or colleagues and reducing their standards of care (a third reported these behaviours at least monthly) and were more likely to intend to retire early (59% had such plans). Key features distinguishing 'satisfied' from 'fatigued' interviewed consultants included having strategies to deal with the high work intensities associated with their role and having positive views of the team within which they worked. The degree of variety in their roles and the ability to maintain empathy for their patients were also distinguishing features between these groups. Findings support an urgent review of workforce and resources in emergency medicine and suggest that a multifactorial approach to identification, prevention and treatment of occupational stress in the workforce is required that considers individual, job and organisational factors, particularly those that impact on perceived control and support at work. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  6. Analysis of the consumption of useful life by thermal fatigue in the gas turbine nozzles during the operation at continuous load and transients; Analisis de consumo de vida por fatiga termica en las toberas de turbina de gas durante operacion con carga continua y transitorios

    Energy Technology Data Exchange (ETDEWEB)

    Perez Hernandez, Efrain Betuel

    2007-08-15

    The gas turbines operate at extremely high temperatures, with high thermal and mechanical stresses, causing that the life of the involved components diminishes. In the present thesis the temperature distribution on the nozzle obtained in other investigation as a result of heat transfer and fluid flow analysis applying CDF code Star-CD was used. Next, the program NISA was used to perform the analysis of thermal stresses by means of finite element method. Finally, the results of stress analysis were introduced to the program nCode to accomplish the nozzle remaining useful life assessment due to thermal fatigue in critical location on the nozzle by means of the CLF module (Critical Location Fatigue). The full methodology used to determine the nozzle operational conditions, load history, material properties and the fatigue model used to determine the number of cycles to failure of the nozzle during constant load and transients operation is presented. [Spanish] Las turbinas de gas operan a temperaturas extremadamente altas, a elevados esfuerzos termicos y mecanicos, ocasionando que la vida de los componentes involucrados se reduzca. En la presente tesis se presentan los resultados realizados por otras investigaciones de temperaturas obtenidas a partir de un analisis de transferencia de calor y flujo de fluidos de la tobera mediante el programa Star-CD basado en volumenes finitos. Posteriormente, se utilizo el programa NISA para realizar el analisis de esfuerzos mediante elementos finitos. Finalmente, se llevaron los resultados al programa nCode para realizar la estimacion de vida util por fatiga termica en un punto critico de la tobera mediante el modulo CLF (Critical Location Fatigue). Se muestra la metodologia empleada para determinar las condiciones de operacion, historial de carga, propiedades del material y el modelo de dano por fatiga para determinar el numero de ciclo para falla de la tobera durante operacion con carga continua y transitorios.

  7. Effect of mouth-motion fatigue and thermal cycling on the marginal accuracy of partial coverage restorations made of various dental materials.

    Science.gov (United States)

    Stappert, Christian F J; Chitmongkolsuk, Somsak; Silva, Nelson R F A; Att, Wael; Strub, Joerg R

    2008-09-01

    To investigate the influence of mouth-motion fatigue on marginal-accuracy of partial-coverage-restorations-(PCRs) of various dental materials. Eighty molars were prepared equally and divided into five groups (n=16). PCRs were fabricated of following dental materials: Group-GO=Gold-Pontor-MPF(double dagger), Group-TA=Targis*, Group-EX=IPS-e.max-Press*, Group-EM=IPS-Empress*, Group-PC=ProCAD*/Cerec 3(dagger) ((double dagger)Metalor/*Ivoclar-Vivadent/(dagger)Sirona-Dental-System). Gold-PCRs were cemented conventionally. Residual 64 PCRs were adhesively luted and subjected to masticatory loading (1.2million-cycles, 1.6Hz, 49N) and thermal cycling (5 degrees C/55 degrees C, 60s, dwell-time, 5500cycles). Discrepancies in marginal-accuracy were examined on epoxy replicas (200 x magnification). Statistical analysis was performed by unpaired and paired t-tests (alpha=0.05). After cementing, marginal-accuracy (geometrical mean)[95% confidence limits] was recorded: GO-47[43-51]microm, TA-42[38-45]microm, EX-60[52-67]microm, EM-52[45-60]microm and PC-75[59-94]microm. No significant differences were found between groups GO, TA and EM. Values of Group-EX were significantly higher compared to Group-TA (p=0.04). Group-PC demonstrated significantly decreased marginal-accuracy towards groups GO (p=0.03) and TA (p=0.02). Except for Group-GO (p=0.01), no significant changes in marginal-accuracy were observed after mouth-motion fatigue and thermal cycling (GO-42[38-45]microm, TA-42[38-47]microm, EX-56[49-65]microm, EM-54[46-64]microm and PC-71[59-84]microm). However, Group-GO and Group-EM showed significant deviations in marginal-accuracy after aging (p=0.04). Marginal discrepancies of groups EX and EM were similar (p=1.0). Values of Group-PC were significantly higher when compared to groups GO (p=0.01) and TA (p=0.02). Buccal-lingual marginal discrepancies were significantly higher than mesial-distal in all groups and stages. Cast-gold-PCRs demonstrated superior marginal

  8. Digenean larvae--the cause and beneficiaries of the changes in host snails' thermal behavior.

    Science.gov (United States)

    Żbikowska, Elżbieta; Żbikowski, Janusz

    2015-03-01

    Parasite-induced changes in host's thermal preferences not only can be interpreted as a physiological defense response of the host but also can represent a pathological manifestation of the parasite. Both may become established in host-parasite relationships if they are beneficial for at least one of the counterparts. This study investigates parasite-induced changes in the thermoregulatory behavior of first intermediate hosts of Digenea (i.e. Lymnaea stagnalis and Planorbarius corneus), infected with Notocotylidae or Echinostomatidae larvae. The investigated parasite species developed different transmission strategies outside the body of a snail, which may imply a different effect on the behavior of their hosts. Notocotylus attenuatus in L. stagnalis and Notocotylus ephemera in P. corneus produce symptoms of anapyrexia, prolonging the lifespan of their hosts. By contrast, Echinoparyphium aconiatum in L. stagnalis and Echinostoma spiniferum in P. corneus interfere with defensive thermoregulatory behavior of host snails, causing their accelerated death. The results of laboratory research indicate that thermal preferences of the snails infected with all investigated trematodes facilitate the transmission of the parasites in environment.

  9. Fatigue of internal combustion engines

    Science.gov (United States)

    Dumanois, P

    1924-01-01

    The above conditions enable the employment of a criterion of general fatigue which simultaneously takes account of both mechanical and thermal conditions, for the sake of comparing any projected engine with engines of the same type already in use.

  10. Fatigue damage assessment of recycled metals and alloys | Ayensu ...

    African Journals Online (AJOL)

    Fatigue damage assessment obeyed Paris law, fatigue limit was inversely proportional to grain size, fatigue strength decreased as tempera-ture increased, while fatigue life cycles increased with temperature decrease. The fatigue failure resulted from residual stresses which caused crack opening and propagation leading ...

  11. Thermal-Fatigue Analysis of W-coated Ferritic-Martensitic Steel Mockup for Fusion Reactor Components

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Won; Kim, Suk Kwon; Park, Seong Dae; Kim, Dong Jun [KAERI, Daejeon (Korea, Republic of); Moon, Se Yeon; Hong, Bong Guen [Chonbuk University, Jeonju (Korea, Republic of)

    2016-05-15

    In this study, commercial ANSYS-CFX for thermalhydraulic analysis and ANSYS-mechanical for the thermo-mechanical analysis are used to evaluate the thermal-lifetime of the mockup to determine the test conditions. Also, the Korea Heat Load Test facility with an Electron Beam (KoHLT-EB) will be used and its water cooling system is considered to perform the thermal-hydraulic analysis especially for considering the two-phase analysis with a higher heat flux conditions. Through the ITER blanket first wall (BFW) development project in Korea, the joining methods were developed with a beryllium (Be) layer as a plasma-facing material, a copper alloy (CuCrZr) layer as a heat sink, and type 316L austenitic stainless steel (SS316L) as a structural material. And joining methods were developed such as Be as an armor and FMS as a structural material, or W as an armor and FMS as a structural material were developed through the test blanket module (TBM) program. As a candidate of PFC for DEMO, a new W/FMS joining methods, W coating with plasma torch, have been developed. The HHF test conditions are found by performing a thermal-hydraulic and thermo-mechanical analysis with the conventional codes such as ANSYSCFX and .mechanical especially for considering the two-phase condition in cooling tube.

  12. Fatigue evaluation algorithms: Review

    Energy Technology Data Exchange (ETDEWEB)

    Passipoularidis, V.A.; Broendsted, P.

    2009-11-15

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Puck, to model the degradation caused by failure events in ply level. Residual strength is incorporated as fatigue damage accumulation metric. Once the typical fatigue and static properties of the constitutive ply are determined,the performance of an arbitrary lay-up under uniaxial and/or multiaxial load time series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a wind turbine rotor blade construction. Two versions of the algorithm, the one using single-step and the other using incremental application of each load cycle (in case of ply failure) are implemented and compared. Simulation results confirm the ability of the algorithm to take into account load sequence effects. In general, FADAS performs well in predicting life under both spectral and block loading fatigue. (author)

  13. Proximal and distal muscle fatigue differentially affect movement coordination.

    Science.gov (United States)

    Cowley, Jeffrey C; Gates, Deanna H

    2017-01-01

    Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proximal (shoulder flexor) or distal (finger flexor) muscles. Pre/Post changes in trunk, shoulder, elbow, and wrist kinematics were compared to determine how proximal and distal fatigue affected multi-joint movement patterns and variability. Proximal fatigue caused a significant increase (7°, p fatigue caused small but significant changes in trunk angles (2°, p fatigue protocols (p fatigue at either proximal or distal joints. The identified differences between proximal and distal muscle fatigue adaptations could facilitate risk assessment of occupational tasks.

  14. Proximal and distal muscle fatigue differentially affect movement coordination

    Science.gov (United States)

    Cowley, Jeffrey C.

    2017-01-01

    Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proximal (shoulder flexor) or distal (finger flexor) muscles. Pre/Post changes in trunk, shoulder, elbow, and wrist kinematics were compared to determine how proximal and distal fatigue affected multi-joint movement patterns and variability. Proximal fatigue caused a significant increase (7°, p fatigue caused small but significant changes in trunk angles (2°, p fatigue protocols (p fatigue at either proximal or distal joints. The identified differences between proximal and distal muscle fatigue adaptations could facilitate risk assessment of occupational tasks. PMID:28235005

  15. FUV quantum efficiency degradation of cesium iodide photocathodes caused by exposure to thermal atomic oxygen

    Science.gov (United States)

    McPhate, Jason; Anne, Joshi; Bacinski, John; Banks, Bruce; Cates, Carey; Christensen, Paul; Cruden, Brett; Dunham, Larry; Graham, Eric; Hughes, David; Kimble, Randy; Lupie, Olivia; Niedner, Malcolm; Osterman, Steven; Penton, Steven; Proffitt, Charles; Pugel, Diane; Siegmund, Oswald; Wheeler, Thomas

    2011-09-01

    The color dependence of the measured decline of the on-orbit sensitivity of the FUV channel of the HST Cosmic Origins Spectrograph (HST-COS) indicated the principal loss mechanism to be degradation of the cesium iodide (CsI) photocathode of the open-faced FUV detector. A possible cause of this degradation is contamination by atomic oxygen (AO), prompting an investigation of the interaction of AO with CsI. To address this question, opaque CsI photocathodes were deposited on stainless steel substrates employing the same deposition techniques and parameters used for the photocathodes of the HST-COS FUV detector. The as-deposited FUV quantum efficiency of these photocathodes was measured in the 117-174 nm range. Several of the photocathodes were exposed to varying levels of thermalized, atomic oxygen (AO) fluence (produced via an RF plasma). The post AO exposure QE's were measured and the degradation of sensitivity versus wavelength and AO fluence are presented.

  16. Effect of Cyclic Thermo-Mechanical Loads on Fatigue Reliability in Polymer Matrix Composites

    Science.gov (United States)

    Shah, A. R.; Murthy, P. L. N.; Chamis, C. C.

    1996-01-01

    A methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects caused by long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multi-factor interaction relationship developed at NASA Lewis Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability- based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/- 45/90)(sub s) graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.

  17. Hydrogen effects on Ni-Ti fatigue performance by self -heating method

    Science.gov (United States)

    Rokbani, M.; Saint-Sulpice, L.; Arbab Chirani, S.; Bouraoui, T.

    2017-10-01

    Ni-Ti superelastic alloys are extensively used in manufacturing biomedical devices because of their high mechanical performance, good fatigue durability and biocompatibility compared to traditional metallic materials. During clinical use, most of these devices are intended to work under cyclic or repetitive loadings and may be in contact with corrosive environments leading to unexpected failures. It is however recognized that the fatigue-environment interaction, especially fatigue-hydrogen absorption, can be the main cause of these failures. The aim of this work is to investigate the fatigue behavior of superelastic Ni-Ti intended for manufacturing medical devices at high number of cycles (HCF) with a particular emphasis to the effect of hydrogen on fatigue properties. Fatigue tests were analyzed using self-heating measurements based on observing thermal effects during cyclic loadings. The results obtained with self-heating approach showed a trend of a decrease in the fatigue life of Ni-Ti alloys after hydrogen absorption and the fatigue limit extrapolated will be compared with the results obtained with the classical S-N curves method.

  18. Fatigue tests on big structure assemblies of concorde aircraft

    Science.gov (United States)

    Nguyen, V. P.; Perrais, J. P.

    1972-01-01

    Fatigue tests on structural assemblies of the Concorde supersonic transport aircraft are reported. Two main sections of the aircraft were subjected to pressure, mechanical load, and thermal static tests. The types of fatigue tests conducted and the results obtained are discussed. It was concluded that on a supersonic aircraft whose structural weight is a significant part of the weight analysis, many fatigue and static strength development tests should be made and fatigue and thermal tests of the structures are absolutely necessary.

  19. Proximal and distal muscle fatigue differentially affect movement coordination

    OpenAIRE

    Cowley, Jeffrey C.; Gates, Deanna H.

    2017-01-01

    Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proxim...

  20. Biomarkers for chronic fatigue.

    Science.gov (United States)

    Klimas, Nancy G; Broderick, Gordon; Fletcher, Mary Ann

    2012-11-01

    Fatigue that persists for 6 months or more is termed chronic fatigue. Chronic fatigue (CF) in combination with a minimum of 4 of 8 symptoms and the absence of diseases that could explain these symptoms, constitute the case definition for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Inflammation, immune system activation, autonomic dysfunction, impaired functioning in the hypothalamic-pituitary-adrenal axis, and neuroendocrine dysregulation have all been suggested as root causes of fatigue. The identification of objective markers consistently associated with CFS/ME is an important goal in relation to diagnosis and treatment, as the current case definitions are based entirely on physical signs and symptoms. This review is focused on the recent literature related to biomarkers for fatigue associated with CFS/ME and, for comparison, those associated with other diseases. These markers are distributed across several of the body's core regulatory systems. A complex construct of symptoms emerges from alterations and/or dysfunctions in the nervous, endocrine and immune systems. We propose that new insight will depend on our ability to develop and deploy an integrative profiling of CFS/ME pathogenesis at the molecular level. Until such a molecular signature is obtained efforts to develop effective treatments will continue to be severely limited. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. BIOMARKERS for CHRONIC FATIGUE

    Science.gov (United States)

    Broderick, Gordon; Fletcher, Mary Ann

    2012-01-01

    Fatigue that persists for 6 months or more is termed chronic fatigue. Chronic fatigue (CF) in combination with a minimum of 4 of 8 symptoms and the absence of diseases that could explain these symptoms, constitute the case definition for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Inflammation, immune system activation, autonomic dysfunction, impaired functioning in the hypothalamic-pituitary-adrenal axis, and neuroendocrine dysregulation have all been suggested as root causes of fatigue. The identification of objective markers consistently associated with CFS/ME is an important goal in relation to diagnosis and treatment, as the current case definitions are based entirely on physical signs and symptoms. This review is focused on the recent literature related to biomarkers for fatigue associated with CFS/ME and, for comparison, those associated with other diseases. These markers are distributed across several of the body’s core regulatory systems. A complex construct of symptoms emerges from alterations and/or dysfunctions in the nervous, endocrine and immune systems. We propose that new insight will depend on our ability to develop and deploy an integrative profiling of CFS/ME pathogenesis at the molecular level. Until such a molecular signature is obtained efforts to develop effective treatments will continue to be severely limited. PMID:22732129

  2. Chronic fatigue syndrome: diagnosis and treatment | Revelas ...

    African Journals Online (AJOL)

    Chronic fatigue syndrome (CFS) refers to marked and prolonged fatigue, for which no indentifiable cause can be found. Despite the presence of extensive symptoms, diagnosis is made when there is profound fatigue, lasting for a duration of six months, or longer. CFS is frequently seen in association with psychiatric ...

  3. Experienced and physiological fatigue in neuromuscular disorders.

    NARCIS (Netherlands)

    Schillings, M.L.; Kalkman, J.S.; Janssen, H.M.; Engelen, B.G.M. van; Bleijenberg, G.; Zwarts, M.J.

    2007-01-01

    OBJECTIVE: Fatigue has been described as a typical symptom of neurological diseases. It might be caused both by changes at the peripheral and at the central level. This study measured the level of experienced fatigue and physiological correlates of fatigue in three genetically defined neuromuscular

  4. Heat storage rate and acute fatigue in rats

    Directory of Open Access Journals (Sweden)

    L.O.C. Rodrigues

    2003-01-01

    Full Text Available Thermal environmental stress can anticipate acute fatigue during exercise at a fixed intensity (%VO2max. Controversy exists about whether this anticipation is caused by the absolute internal temperature (Tint, ºC, by the heat storage rate (HSR, cal/min or by both mechanisms. The aim of the present study was to study acute fatigue (total exercise time, TET during thermal stress by determining Tint and HSR from abdominal temperature. Thermal environmental stress was controlled in an environmental chamber and determined as wet bulb globe temperature (ºC, with three environmental temperatures being studied: cold (18ºC, thermoneutral (23.1ºC or hot (29.4ºC. Six untrained male Wistar rats weighing 260-360 g were used. The animals were submitted to exercise at the same time of day in the three environments and at two treadmill velocities (21 and 24 m/min until exhaustion. After implantation of a temperature sensor and treadmill adaptation, the animals were submitted to a Latin square experimental design using a 2 x 3 factorial scheme (velocity and environment, with the level of significance set at P<0.05. The results showed that the higher the velocity and the ambient temperature, the lower was the TET, with these two factors being independent. This result indicated that fatigue was independently affected by both the increase in exercise intensity and the thermal environmental stress. Fatigue developed at different Tint and HSR showed the best inverse relationship with TET. We conclude that HSR was the main anticipating factor of fatigue.

  5. Fatigue (PDQ)

    Science.gov (United States)

    ... home. Depression. Anxiety. Trouble sleeping. Younger age. Being underweight. Having advanced cancer or other medical conditions. Fatigue ... detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health ...

  6. Microstructural evolution during the thermomechanical fatigue of solder joints

    Energy Technology Data Exchange (ETDEWEB)

    Frear, D R

    1991-01-01

    Solder joints in electronic packages are electrical interconnections that also function as mechanical bonds. The solder often constrains materials of different coefficients of thermal expansion that, when thermal fluctuations are encountered, causes the solder joint to experience cyclical deformation. Due to the catastrophic consequences of electrical or mechanical failure of solder joints, a great deal of work has been performed to develop a better understanding of the metallurgical response of solder joints subjected to thermomechanical fatigue. This work reviews the microstructural and mechanical evolution that occurs in solder joints during thermomechanical fatigue. The eutectic Sn-Pb solder alloy is highlighted. Unlike most materials that experience thermomechanical fatigue, solder is commonly used at temperatures of up to nine-tenths of its melting point. Therefore extensive creep, solid state diffusion, recrystallization and grain growth occur in this alloy resulting in the evolution of a heterogeneous coarsened band through which failure eventually takes place. Two other solder alloys are compared with the Sn-Pb eutectic, a Pb-rich Sn-Pb alloy and a ternary near eutectic (40In-40Sn-20Pb, all alloys are given in wt. %). The Pb-rich alloy is a precipitated single phase matrix that does not evolve during thermomechanical fatigue and subsequently has a shorter lifetime. Conversely, the 40In-40Sn-20Pb solder is a two phase eutectic in which the microstructures refines during thermomechanical fatigue giving it a longer lifetime than the eutectic Sn-Pb solder. The microstructural processes that occur during thermomechanical fatigue and final fracture behavior are discussed for the three solder alloys. 47 refs., 14 figs.

  7. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    in the game: (1) after short-term intense periods in both halves; (2) in the initial phase of the second half; and (3) towards the end of the game. Temporary fatigue after periods of intense exercise in the game does not appear to be linked directly to muscle glycogen concentration, lactate accumulation...... temperatures compared with the end of the first half. Thus, when players perform low-intensity activities in the interval between the two halves, both muscle temperature and performance are preserved. Several studies have shown that fatigue sets in towards the end of a game, which may be caused by low glycogen...... concentrations in a considerable number of individual muscle fibres. In a hot and humid environment, dehydration and a reduced cerebral function may also contribute to the deterioration in performance. In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different...

  8. Nitinol Fatigue Life for Variable Strain Amplitude Fatigue

    Science.gov (United States)

    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.

  9. Destruction of Moulding Sands with Chemical Binders Caused by the Thermal Radiation of Liquid Metal

    Directory of Open Access Journals (Sweden)

    Zych J.

    2015-12-01

    Full Text Available The obtained results of heating of sand moulds with binders by means of a thermal radiation of liquid metal are presented in this study. Standard samples for measuring Rg made of the tested moulding sands were suspended at the lower part of the cover which was covering the crucible with liquid metal (cast iron, placed in the induction furnace. The authors own methodology was applied in investigations. The progressing of the samples surface layers heating process was determined as the heating time function. Samples of a few kinds of moulding sands with chemical binders were tested. Samples without protective coatings as well as samples with such coatings were tested. The influence of the thermal radiation on bending resistance of samples after their cooling was estimated. The influence of several parameters such as: time of heating, distance from the metal surface, metal temperature, application of coatings, were tested. A very fast loss of strength of moulding sands with organic binders was found, especially in cases when the distance between metal and sample surfaces was small and equaled to 10÷15 mm. Then, already after app. 15 seconds of the radiation (at Tmet=1400°C, the resistance decreases by nearly 70%. Generally, moulding sands with organic binders are losing their strength very fast, while moulding sands with water glass at first increase their strength and later slightly lose. The deposition of protective coatings increases the strength of the mould surface layers, however does not allow to retain this strength after the metal thermal radiation.

  10. Thermomechanical fatigue damage evolution in SAC solder joints

    NARCIS (Netherlands)

    Matin, M. A.; Vellinga, W. P.; D Geers, M. G.

    2007-01-01

    Thermornechanical fatigue in lab-type Sn-Ag-Cu solder interconnections between two copper plates has been investigated under cyclic thermal loading within a number of temperature ranges. Fatigue mechanisms have been studied using optical and scanning electron microscopy. Among the various fatigue

  11. Examination of the CLIC drive beam pipe design for thermal distortion caused by distributed beam loss

    CERN Document Server

    Johnson, C D

    1997-01-01

    Beam transport programs are widely used to estimate the distribution of power deposited in accelerator structures by particle beams, either intentionally as for targets or beam dumps or accidentally owing to beam loss incidents. While this is usually adequate for considerations of radiation safety, it does not reveal the expected temperature rise and its effect on structural integrity. To find this, thermal diffusion must be taken into account, requiring another step in the analysis. The method that has been proposed is to use the output of a transport program, perhaps modified, as input for a finite element analysis program that can solve the thermal diffusion equation. At CERN, the design of the CLIC drive beam pipe has been treated in this fashion. The power distribution produced in the walls by a distributed beam loss was found using the electron gamma shower code EGS4. The distribution of power density was then used to form the input for the finite element analysis program ANSYS, which was able to find t...

  12. [Fatigue among nursing undergraduate students].

    Science.gov (United States)

    Amaducci, Camila de Moraes; Mota, Dálete Delalibera Faria de Correa; Pimenta, Cibele Andrucioli de Mattos

    2010-12-01

    Fatigue among students may harm their learning. This study evaluated the fatigue of nursing undergraduate students and its relations to their graduation year, participation in extracurricular activities, people with whom they lived, depression and their body mass index (BMI)). The study had the participation of 189 (60.2%) students from the EEUSP, from which 96.2% were women with the average age of 21.6 years old, 80.9% lived with their parents, 43.9% performed extracurricular activities, 24.8% had varied BMI and 22.2% presented dysphoria or depression (Beck Depression Inventory). Fatigue was moderate/intense for 83.5% of the students (Piper Fatigue Scale--Revised and Fatigue Pictogram) and 59.8% reported moderate/intense impairment in their habitual activities. Fatigue presented a positive correlation to the graduation year, to the BMI and to depression (p academic activity was the main cause of fatigue, whereas sleep and leisure were the most frequent strategies to handle it. Fatigue was significant and intense, but there was an irregularity between its frequency, magnitude and impact in the daily life activities.

  13. Thermal Stratification in Small Solar Domestic Storage Tanks caused by Draw-offs

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Furbo, Simon

    2005-01-01

    in the storage tank. Furthermore, for theoretical investigations of the flow patterns in the storage tank, calculations were carried out by means of the Computational Fluid Dynamics (CFD) tool Fluent. Based on the experimental and theoretical results, the sizes of fully mixed zones in the bottom part...... behaviour is not taken into account sufficiently. Two typical Danish domestic water storage tanks, each with a volume of about 150 l, were investigated. In both tanks the inlet pipes are placed at the bottom and hot water is drawn from the upper part of tank. Above the inlet pipes, differently shaped plates...... are placed in order to reduce the mixing of the incoming cold water with the warmer storage water. To measure the thermal stratification thermocouples were placed in a vertical glass tube inside the tank. Measurements were carried out with different draw-off volumes, flow rates, and initial temperatures...

  14. THERMAL STRATIFICATION IN SOLAR DOMESTIC STORAGE TANKS CAUSED BY DRAW-OFFS

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Furbo, Simon

    2003-01-01

    in the storage tank. Furthermore, for theoretical investigations of the flow patterns in the storage tank, calculations were carried out by means of the Computational Fluid Dynamics (CFD) tool Fluent. Based on the experimental and theoretical results, the sizes of fully mixed zones in the bottom part...... behaviour is not taken into account sufficiently. Two typical Danish domestic water storage tanks, each with a volume of about 150 l, were investigated. In both tanks the inlet pipes are placed at the bottom and hot water is drawn from the upper part of tank. Above the inlet pipes, differently shaped plates...... are placed in order to reduce the mixing of the incoming cold water with the warmer storage water. To measure the thermal stratification thermocouples were placed in a vertical glass tube inside the tank. Measurements were carried out with different draw-off volumes, flow rates, and initial temperatures...

  15. Simulation of Fatigue Behavior of High Temperature Metal Matrix Composites

    Science.gov (United States)

    Tong, Mike T.; Singhal, Suren N.; Chamis, Christos C.; Murthy, Pappu L. N.

    1996-01-01

    A generalized relatively new approach is described for the computational simulation of fatigue behavior of high temperature metal matrix composites (HT-MMCs). This theory is embedded in a specialty-purpose computer code. The effectiveness of the computer code to predict the fatigue behavior of HT-MMCs is demonstrated by applying it to a silicon-fiber/titanium-matrix HT-MMC. Comparative results are shown for mechanical fatigue, thermal fatigue, thermomechanical (in-phase and out-of-phase) fatigue, as well as the effects of oxidizing environments on fatigue life. These results show that the new approach reproduces available experimental data remarkably well.

  16. Evolution of a typical ion-scale magnetic flux rope caused by thermal pressure enhancement

    Science.gov (United States)

    Teh, W.-L.; Nakamura, T. K. M.; Nakamura, R.; Baumjohann, W.; Russell, C. T.; Pollock, C.; Lindqvist, P.-A.; Ergun, R. E.; Burch, J. L.; Torbert, R. B.; Giles, B. L.

    2017-02-01

    With high time-resolution field and plasma measurements by the Magnetospheric Multiscale spacecraft, interior fine structures of two ion-scale magnetic flux ropes ( 5 and 11 ion inertial length radius) separated by 14 s are resolved. These two ion-scale flux ropes (FR1 and FR2) show non-frozen-in ion behavior and consist of a strong axial magnetic field at the reversal of the negative-then-positive bipolar field component. The negative bipolar field component of the FR2 is found to be depressed, where magnetic pressure and total pressure decrease, but ion and electron thermal pressures increase, a feature akin to a crater-like flux rope. The pressure enhancement is due to the magnetosheath plasma feeding into the flux rope along the field lines. Magnetic field draping and energetic electrons are also observed in the trailing part of the FR2. The ratio of perpendicular and parallel currents indicates that the FR1 appears force-free but the FR2 seems not. Moreover, the FR2 is time-dependent as a result of a low correlation coefficient (CC = 0.75) for the derivation of the deHoffmann-Teller frame using the direct measured electric fields, while the FR1 is in quasi-steady conditions (CC = 0.94). It is concluded that the crater formation within the FR2 can be interpreted by the analytical flux rope simulation as the evolution of typical flux rope to crater-like one due to the thermal pressure enhancement, which could be induced by the depression of transverse magnetic fields of the flux rope.

  17. Human survival in volcanic eruptions: Thermal injuries in pyroclastic surges, their causes, prognosis and emergency management.

    Science.gov (United States)

    Baxter, Peter J; Jenkins, Susanna; Seswandhana, Rosadi; Komorowski, Jean-Christophe; Dunn, Ken; Purser, David; Voight, Barry; Shelley, Ian

    2017-08-01

    This study of burns patients from two eruptions of Merapi volcano, Java, in 1994 and 2010, is the first detailed analysis to be reported of thermal injuries in a large series of hospitalised victims of pyroclastic surges, one of the most devastating phenomena in explosive eruptions. Emergency planners in volcanic crises in populated areas have to integrate the health sector into disaster management and be aware of the nature of the surge impacts and the types of burns victims to be expected in a worst scenario, potentially in numbers and in severity that would overwhelm normal treatment facilities. In our series, 106 patients from the two eruptions were treated in the same major hospital in Yogyakarta and a third of these survived. Seventy-eight per cent were admitted with over 40% TBSA (total body surface area) burns and around 80% of patients were suspected of having at least some degree of inhalation injury as well. Thirty five patients suffered over 80% TBSA burns and only one of these survived. Crucially, 45% of patients were in the 40-79% TBSA range, with most suspected of suffering from inhalation injury, for whom survival was most dependent on the hospital treatment they received. After reviewing the evidence from recent major eruptions and outlining the thermal hazards of surges, we relate the type and severity of the injuries of these patients to the temperatures and dynamics of the pyroclastic surges, as derived from the environmental impacts and associated eruption processes evaluated in our field surveys and interviews conducted by our multi-disciplinary team. Effective warnings, adequate evacuation measures, and political will are all essential in volcanic crises in populated areas to prevent future catastrophes on this scale. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

  18. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09); Amorcage et propagation de reseaux de fissures de fatigue thermique dans un acier inoxydable austenitique de type X2 CrNi18-09 (AISI 304 L)

    Energy Technology Data Exchange (ETDEWEB)

    Maillot, V

    2004-07-01

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, {delta}T between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some

  19. Fatigue in cancer: A review of literature

    Directory of Open Access Journals (Sweden)

    Vijayakumar Narayanan

    2009-01-01

    Full Text Available Fatigue is a common symptom of advanced cancer limiting one′s activity and affecting the quality of life. It is a multidimensional symptom complex with subjective and objective components. Hence, its definition and assessment seems arbitrary, incomplete, and elusive. Components of fatigue often merge with other ′disease states′ as anemia, depression and so on, compounding difficulty to assess it separately. Fatigue has a high prevalence rate, and lasts longer in chronic diseases like cancer. Its association with treatment modalities like chemotherapy, radiotherapy alongside the primary disease process makes it seemingly ubiquitous in many cases. Systemic manifestation of cancer causes excess demand on body resources on cell repair, uncontrolled growth with metabolite accumulation causing fatigue. Co-morbid conditions of organic and psychological nature causes fatigue. There are many assessment tools for fatigue with different uses and objectives, simple and reproducible tools like Brief Fatigue Inventory, Edmonton Symptom assessment scale seem feasible in everyday practice. Management of fatigue is not straightforward and rewarding. Although treatment of cause appears to be an attractive option, it is not possible in all cases. Therapeutic agents targeting cytokine load is in early stages of study and available results are not favorable. Specific measures aimed at pain relief, prevention/treatment of sepsis, management of depression, avoidance of drugs causing fatigue, restoring the metabolic profile are important. Methyl phenidate, megestrol, and modafinil are some drugs with promising effect to treat fatigue, though confirmatory studies are yet to be established. Non-pharmacological methods are also helpful. Forewarning patients on upcoming fatigue, active regular exercise, and stress management are some of them. Fatigue being a multidimensional entity, single mode of therapy is insufficient. Combined modality tailored to individual

  20. Effects of irradiation on low cycle fatigue properties for reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.W. [Kyoto Univ., Graduate School of Energy Science (Japan); Tanigawa, H. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Kohyama, A. [Kyoto Univ., lnstitute of Advanced Energy (Japan)

    2007-07-01

    Full text of publication follows: In materials life decision for a commercial blanket, thermal fatigue property of materials is a particularly important. The loading of structural materials in fusion reactor is, besides the plasma surface interactions, a combined effect of high heat fluxes and neutron irradiation. Depending on the pulse lengths, the operating conditions, and the thermal conductivity, these oscillating temperature gradients will cause elastic and elastic-plastic cyclic deformation giving rise to (creep-) fatigue in structural first wall and blanket components. Especially, investigation of the fatigue property in Reduced Activation Ferritic/Martensitic (RAF/M) steel and establishment of the evaluation technology are demanded in particular immediately for design/manufacturing of ITER-TBM. And also, fatigue testing after irradiation will be carried out in hot cells with remote control system. Considering limited ability of specimen manipulation in the cells, the specimen and the test method need to be simple for operation. The existing data bases of RAF/M steel provide baseline data set including post-irradiation fatigue data. However, to perform the accurate fatigue lifetime assessment for ITER-TBM and beyond utilizing the existing data base, the mechanical understanding of fatigue fracture is mandatory. It has been previously reported by co-authors that dislocation cell structure was developed on low cycle fatigued RAF/M steel, and led the fatigue crack to develop along prior austenitic grain boundary. In this work, the effects of nuclear irradiation on low cycle fatigue properties for RAF/M steels and its fracture mechanisms were examined based on the flow stress analysis and detailed microstructure analysis. Fracture surfaces and crack initiation site were investigated by scanning electron microscope (SEM). Transmission electron microscopy (TEM) was also applied to clarify the microstructural features of fatigue behavior. It is also important to

  1. The application of RBI-concept to ultrasonic measurement of fatigue cracks

    Energy Technology Data Exchange (ETDEWEB)

    Pitkaenen, J.; Saerkiniemi, P.; Kauppinen, P. [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    In many power plants there are problem areas, which are not included in the official inspection programs. Flaws can be induced during service due to the service conditions in components and welded joints. These can lead to failures, which cause unforeseen shutdowns during operation and unscheduled repairs have to be earned out. The basic idea of Risk Based Inspection (RBI) methodology is to include this kind of objects in the inspection program. In this presentation two possible objects for RBI are described - thermal fatigue cracking in process piping and fatigue cracking in spinning fly wheel. (orig.) 4 refs.

  2. Marine heatwave causes unprecedented regional mass bleaching of thermally resistant corals in northwestern Australia.

    Science.gov (United States)

    Le Nohaïc, Morane; Ross, Claire L; Cornwall, Christopher E; Comeau, Steeve; Lowe, Ryan; McCulloch, Malcolm T; Schoepf, Verena

    2017-11-03

    In 2015/16, a marine heatwave associated with a record El Niño led to the third global mass bleaching event documented to date. This event impacted coral reefs around the world, including in Western Australia (WA), although WA reefs had largely escaped bleaching during previous strong El Niño years. Coral health surveys were conducted during the austral summer of 2016 in four bioregions along the WA coast (~17 degrees of latitude), ranging from tropical to temperate locations. Here we report the first El Niño-related regional-scale mass bleaching event in WA. The heatwave primarily affected the macrotidal Kimberley region in northwest WA (~16°S), where 4.5-9.3 degree heating weeks (DHW) resulted in 56.6-80.6% bleaching, demonstrating that even heat-tolerant corals from naturally extreme, thermally variable reef environments are threatened by heatwaves. Some heat stress (2.4 DHW) and bleaching (coral communities at Ningaloo Reef (23°9'S) and Bremer Bay (34°25'S) were not impacted. The only other major mass bleaching in WA occurred during a strong La Niña event in 2010/11 and primarily affected reefs along the central-to-southern coast. This suggests that WA reefs are now at risk of severe bleaching during both El Niño and La Niña years.

  3. Development of a thermal fatigue test method for thermal barrier coatings by laser excitation using a laser thermal shock facility; Entwicklung eines Pruefverfahrens zur laserinduzierten thermischen Ermuedung thermischer Schutzschichten mittels einer Laser-Thermoschockpruefeinrichtung

    Energy Technology Data Exchange (ETDEWEB)

    Nies, Daniel

    2012-07-13

    The finite nature of fossil fuel supply and the growing environmental awareness become increasingly stronger motivations for the development of efficient gas turbines and jet engines for power generation or as engines for land-, sea- and water-based vehicles. One concept developed for this purpose are thermal barrier coatings, where the thermal load of components is reduced by applying a ceramic coating onto the components. In this work the possibility to use a laser thermal shock facility for thermo-cyclic testing of thermal barrier coatings is examined. A focused laser beam is used for heating the sample and a homogeneous temperature distribution on the sample surface is achieved by the used trajectory and radial adjusted laser power. The required improvements of the existing testing facility are explained, including the development of a new sample holder and of the testing and evaluation routines for the experiments. For the assessment of the initiation and evolution of damages, acoustic emission and thermographic methods are used. The possibilities and limits of these methods are assessed during the experiments. The work also includes an extensive temperature dependent characterisation of the ceramic material used for the thermal barrier coating. In this part, the measurement of the Young's modulus by a dynamic method is to be highlighted, as this is a rarely used technique. The characterisations show the expected values, except for a lower porosity as expected by the manufacturer and no significant phase changes during isothermal heat treatments. To reach sample surface temperatures above 1000 C, it is necessary to increase the absorption by an additional coating of magnetite. The temperature distribution on the surface is measured by an infrared camera, which is calibrated for this purpose. With the incorporated active air cooling of the sample backside, the temperature gradient can be controlled, but still leaves room for improvements. Already without

  4. Measurement of thermally induced changes in the refractive index of glass caused by laser processing.

    Science.gov (United States)

    Sullivan, James; Zhao, Jian; Bennett, Ted D

    2005-11-20

    The effects of CO2 laser heating of pure fused silica are investigated. Studies show that the laser heating process causes a small volume of glass to be left in an altered microstructural state. To measure the refractive index of this altered region, a process was developed to create a thin film of altered glass. Samples were measured with a prism coupler, and a theoretical model was developed to predict the intensity values collected during the measurement. A least-squares routine was used to determine the refractive index that results in the best fit between the experimental and predicted intensity data. The refractive index in the altered glass was found to increase by approximately 0.07%.

  5. Exploring Neuro-Physiological Correlates of Drivers' Mental Fatigue Caused by Sleep Deprivation Using Simultaneous EEG, ECG, and fNIRS Data

    Science.gov (United States)

    Ahn, Sangtae; Nguyen, Thien; Jang, Hyojung; Kim, Jae G.; Jun, Sung C.

    2016-01-01

    Investigations of the neuro-physiological correlates of mental loads, or states, have attracted significant attention recently, as it is particularly important to evaluate mental fatigue in drivers operating a motor vehicle. In this research, we collected multimodal EEG/ECG/EOG and fNIRS data simultaneously to develop algorithms to explore neuro-physiological correlates of drivers' mental states. Each subject performed simulated driving under two different conditions (well-rested and sleep-deprived) on different days. During the experiment, we used 68 electrodes for EEG/ECG/EOG and 8 channels for fNIRS recordings. We extracted the prominent features of each modality to distinguish between the well-rested and sleep-deprived conditions, and all multimodal features, except EOG, were combined to quantify mental fatigue during driving. Finally, a novel driving condition level (DCL) was proposed that distinguished clearly between the features of well-rested and sleep-deprived conditions. This proposed DCL measure may be applicable to real-time monitoring of the mental states of vehicle drivers. Further, the combination of methods based on each classifier yielded substantial improvements in the classification accuracy between these two conditions. PMID:27242483

  6. A fibre-optic UV system for H(2)SO(4) production in aerosol chambers causing minimal thermal effects

    CERN Document Server

    Kupc, A; Onnela, A; Duplissy, J; Mathot, S; Danielczok, A; Walther, H; Minginette, P; Rondo, L; Ickes, L; Curtius, J; Wagner, P E; Amorim, A; Lima, J M; Ehrhart, S; Kurten, A

    2011-01-01

    A novel fibre-optic UV illumination system for sulphuric acid (H(2)SO(4)) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light (UV) power while causing practically no thermal effect on the aerosol chamber (temperature variation <0.005 degrees C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H(2)SO(4) were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application. (C) 2011 Elsevier Ltd. All rights reserved.

  7. Migration of titanium cable into spinal cord and spontaneous C2 and C3 fusion: Case report of possible causes of fatigue failure after posterior atlantoaxial fixation.

    Science.gov (United States)

    Li, Huibo; Lou, Jigang; Liu, Hao

    2016-12-01

    Atlantoaxial instability is a common and serious injury of the upper cervical spine. Brooks' procedure is widely used to reconstruct the unstable atlantoaxial joint. The migration into spinal cord of titanium cable and spontaneous fusion between C2 and C3 has been little reported and the management of such a patient is difficult. We describe an unusual case of fatigue failure of posterior titanium atlantoaxial cable fixation with migration into the spinal cord and spontaneous fusion between C2 and C3. A 16-year-old girl complained of cervico-occipital pain with numbness and weakness of extremities 3 months ago. The girl underwent posterior C1-C2 arthrodesis with titanium cables and autogenous iliac crest bone grafting when she was 6 years old. When presented to our emergency department, imaging revealed the cracked titanium atlantoaxial cable and the spontaneous fusion between C2 and C3. Computed tomography demonstrated a broken wire with anterior migration of the cable into the spinal cord. The patient underwent posterior approach cervical spinal surgery to remove the broken cables. She remains neurologically intact a year following the posterior approach cervical spine surgery. Brooks' posterior stabilization could not effectively control rotation at the atlantoaxial articulation, so surgeons must be aware of the potential of fatigue failure of cables as well as the possibility of its migration into the spinal cord when using Brooks' posterior stabilization. Bilateral C1 lateral mass and C2 pedicle screw fixation or transarticular screw fixation are recommended by the authors in the event of rotatory instability.

  8. Vertical jump coordination: fatigue effects.

    Science.gov (United States)

    Rodacki, André Luiz Felix; Fowler, Neil E; Bennett, Simon J

    2002-01-01

    The aim of this study was to investigate the segmental coordination of vertical jumps under fatigue of the knee extensor and flexor muscles. Eleven healthy and active subjects performed maximal vertical jumps with and without fatigue, which was imposed by requesting the subjects to extend/flex their knees continuously in a weight machine, until they could not lift a load corresponding to approximately 50% of their body weight. Knee extensor and flexor isokinetic peak torques were also measured before and after fatigue. Video, ground reaction forces, and electromyographic data were collected simultaneously and used to provide several variables of the jumps. Fatiguing the knee flexor muscles did not reduce the height of the jumps or induce changes in the kinematic, kinetic, and electromyographic profiles. Knee extensor fatigue caused the subjects to adjust several variables of the movement, in which the peak joint angular velocity, peak joint net moment, and power around the knee were reduced and occurred earlier in comparison with the nonfatigued jumps. The electromyographic data analyses indicated that the countermovement jumps were performed similarly, i.e., a single strategy was used, irrespective of which muscle group (extensor or flexors) or the changes imposed on the muscle force-generating characteristics (fatigue or nonfatigue). The subjects executed the movements as if they scaled a robust template motor program, which guided the movement execution in all jump conditions. It was speculated that training programs designed to improve jump height performance should avoid severe fatigue levels, which may cause the subjects to learn and adopt a nonoptimal and nonspecific coordination solution. It was suggested that the neural input used in the fatigued condition did not constitute an optimal solution and may have played a role in decreasing maximal jump height achievement.

  9. Crack initiation and propagation on the polymeric material ABS (Acrylonitrile Butadiene Styrene), under ultrasonic fatigue testing

    National Research Council Canada - National Science Library

    G M Domínguez Almaraz; E Correa Gómez; JC Verduzco Juárez; JL Avila Ambriz

    2015-01-01

    ... (Acrylonitrile Butadiene Styrene), under ultrasonic fatigue testing. Three controlled actions were implemented in order to carry out fatigue tests at very high frequency on this material of low thermal conductivity, they are: a...

  10. The importance of fatigue cognitions in chronic hepatitis C infection.

    Science.gov (United States)

    Zalai, Dora; Sherman, Morris; McShane, Kelly; Shapiro, Colin M; Carney, Colleen E

    2015-02-01

    Chronic Hepatitis C virus (HCV) infection is a source of significant public health burden worldwide. Fatigue is a cardinal patient reported consequence of the disease. HCV infection associated fatigue leads to significant impairment in the quality of life and day-to-day functioning. Despite its clinical significance, the factors that contribute to adverse impact of fatigue in HCV infection are largely unknown. This study evaluated the contributions of insomnia, depression symptoms, and fatigue-specific cognitions to fatigue-related functional impairment. Fatigue, insomnia, depression symptoms, as well as fatigue cognitions were assessed in participants (36% females; age>18 years, N=115) with chronic HCV infection at a tertiary hepatitis clinic. Sixty percent of participants reported clinically significant fatigue (Fatigue Severity Index FSS ≥ 4). Comorbidities and fatigue perceptions accounted for 61% of the variation of fatigue. Fatigue perceptions were the main predictors of adverse fatigue outcomes (B=.114, 95% CI=.054-.154). Patients with clinically significant fatigue were four-times more likely than less fatigued patients to believe that the main cause of their fatigue was the infection. Patients' beliefs about their fatigue were the main predictors of adverse fatigue outcomes. These results suggest that fatigue associated with chronic hepatitis C infection can be conceptualized using a cognitive behavioral approach. This was the first study to evaluate the role of both comorbid mood/sleep and cognitive predictors of fatigue in a single model. Integrating the findings into existing treatment strategies could improve patient reported outcomes in chronic hepatitis C infection. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Comparison of the Fatigue Behavior of Copper Alloys

    Science.gov (United States)

    Lerch, Brad; Ellis, David

    2006-01-01

    This presentation is about the development of advanced copper alloys with high thermal conductivity, good creep strength, and adequate fatigue strength for rocket engine applications. It also focuses on the commercial availability of the advanced alloy-GRCop-84 developed at NASA-GRC. The presentation's conclusions are that GRCop-84 has equivalent or better isothermal fatigue lives compared to other commercially available copper alloys, that GRCop-84 can be fabricated in various forms with minimal change in the fatigue lives, that it is equivalent in sothermal, fatigue to AMZIRC at moderate temperatures, and that Narloy-Z is equivalent in fatigue capabilities to GRCop-84 at 400C and below.

  12. Chronic Fatigue Syndrome: How Vulnerable Are Athletes?

    Science.gov (United States)

    Eichner, Edward R.

    1989-01-01

    Discusses chronic fatigue syndrome as it affects elite athletes, noting that overtraining may mimic it. In some cases, athletes who have it perform exceedingly well in the face of debilitating fatigue. Among athletes and nonathletes, the cause and the mind-body connection are areas of controversy and research. (Author/SM)

  13. Neuromuscular frequency-coding and fatigue

    NARCIS (Netherlands)

    Kernell, D; Gandevia, SC; Enoka, RM; McComas, AJ; Stuart, DG; Thomas, CK

    1995-01-01

    In daily life, muscle fatigue often becomes noticeable as an apparent decline in the efficiency of force production by central commands, making it necessary to increase drive (or ''effort'') to produce a constant motor output. Such aspects of fatigue may be caused by changes in the way in which

  14. Thermal inertia and radiating average Temperature. A brief analysis of some causes of discomfort; Inercia Termica y Temperatura media radiante. Un breve analisis de algunas causas de disconfort

    Energy Technology Data Exchange (ETDEWEB)

    Arroba, M.

    2008-07-01

    Radiant average temperature in walls is as important as dry air temperature to achieve thermal comfort of users of a local. An excessive discrepancy between these levels, or an asymmetric distribution of the surface temperature of fences, may cause localized thermal discomfort, an effect impossible to compensate by rising dry air temperature. Thermal inertia and its concentration must be properly studied in order to handle this parameters, inside or outside the building, on both sides of the cladding or none depending on the weather, the bio climatic strategies used, heating and air conditioning systems and planned use of the building. (Author)

  15. Neuromuscular fatigue in racquet sports.

    Science.gov (United States)

    Girard, Olivier; Millet, Grégoire P

    2008-02-01

    This article describes the physiologic and neural mechanisms that cause neuromuscular fatigue in racquet sports: table tennis, tennis, squash, and badminton. In these intermittent and dual activities, performance may be limited as a match progresses because of a reduced central activation, linked to changes in neurotransmitter concentration or in response to afferent sensory feedback. Alternatively, modulation of spinal loop properties may occur because of changes in metabolic or mechanical properties within the muscle. Finally, increased fatigue manifested by mistimed strokes, lower speed, and altered on-court movements may be caused by ionic disturbances and impairments in excitation-contraction coupling properties. These alterations in neuromuscular function contribute to decrease in racquet sports performance observed under fatigue.

  16. Is there a cognitive signature for MS-related fatigue?

    NARCIS (Netherlands)

    Hanken, K.; Eling, P.A.T.M.; Hildebrandt, H.

    2015-01-01

    The compensatory approach of fatigue argues that it is a state caused by task load. The neuropsychiatric approach argues that fatigue is a trait (like depression), unrelated to environmental challenges. We propose that fatigue is an internal state that can be measured behaviorally only by applying

  17. Cancer Fatigue: Why It Occurs and How to Cope

    Science.gov (United States)

    Cancer fatigue: Why it occurs and how to cope The exact causes of cancer fatigue and how best to treat it aren't ... clear. Find out what doctors know about cancer fatigue and what you can do about it. By ...

  18. 1-year course of fatigue in patients on chronic hemodialysis.

    Science.gov (United States)

    Bossola, Maurizio; Di Stasio, Enrico; Antocicco, Manuela; Pepe, Gilda; Marzetti, Emanuele; Vulpio, Carlo

    2017-04-01

    Fatigue is common in end-stage renal disease patients receiving hemodialysis, reduces significantly their quality of life and is associated with all-cause and cardiac-related mortality. Unfortunately, little is known about the course of fatigue in patients on chronic hemodialysis. The Vitality Subscale of the SF-36 (SF-36 VS), Short-Form Health Survey, was administered to 45 patients in January (T1), June (T2) and November (T3) 2015. The score of the SF-36 VS did not differ significantly among T1, T2 and T3. Similarly, the 1-year course of the SF-36 Vitality Subscale score did not differ significantly among T1, T2 and T3 after stratification of patients for sex, age, BMI, IADL and Charlson. Between T1 and T2, 21 out of 45 patients (46.6%) changed their fatigue status: 8 fatigued patients became not-fatigued and 13 not-fatigued patients became fatigued. Between T2 and T3, 12 out of 45 (26.6%) patients changed their fatigue status: 5 fatigued patients became not-fatigued and 7 not-fatigued patients became fatigued. Between T1 and T3, 19 out of 45 patients (42.2%) changed their fatigue status: 6 fatigued patients became not-fatigued and 13 not-fatigued became fatigued. The present study is the first to identify variations in fatigue status among patients on chronic hemodialysis during 1-year course. These findings suggest to frequently assess the presence and severity of fatigue in patients on chronic hemodialysis.

  19. Thermo-elastic-plastic analysis for elastic component under high temperature fatigue crack growth rate

    Science.gov (United States)

    Ali, Mohammed Ali Nasser

    transient thermal stresses superimposed on cyclic mechanical loading results in hollow cylinder under thermal shock in heating case and down shock cooling case. The combination of stress and strain intensity factor theoretical calculations with the experimental output recorded data shows a similar behaviour with increasing temperature, and there is a fair correlation between the profiles at the beginning and then divergence with increasing the crack length. The transient influence of high temperature in case two, giving a very high thermal shock stress as a heating or cooling effects, shifting up the combined stress, when applied a cyclic mechanical load in fraction of seconds, and the reputations of these shocks, causing a fast failure under high thermal shock stress superimposed with mechanical loading.Finally, the numerical modelling analyses three cases studied were solved due to the types of loading and types of specimen geometry by using finite element models constructed through the ANSYS Workbench version 13.0. The first case is a low cyclic fatigue case for a solid cylinder specimen simulated by applying a cyclic mechanical loading. The second is an isothermal fatigue case for solid cylinder specimen simulated by supplying different constant temperatures on the outer surface with cyclic mechanical loading, where the two cases are similar to the experimental tests and the third case, is a thermo-mechanical fatigue for a hollow cylinder model by simulating a thermal up-shock generated due to transient heating on the outer surface of the model or down shock cooling on the inner surface with the cyclic mechanical loading. The results show a good agreement with the experimental data in terms of alternative stress and life in the first case. In case two results show the strain intensity factor is increases with increasing temperature similar to the theoretical solution due to the influence of the modulus of elasticity and the difference in life estimation with the

  20. Thermal histories causing low hardness and the minimum hardness requirement in a modified 9Cr1Mo steel for boiler

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Byeong Ook; Ryu, Seog Hyeon; Lee, Yeon Soo; Kim, Jeong Tae [Doosna Heavy Industries and Construction Co. Ltd., Changwon (Korea, Republic of)

    2005-11-15

    In a Mod.9Cr1Mo steel widely applied to boiler components, low hardness problem related with manufacturing and fabrication processes has become a critical issue recently. In this study, hardness, microstructure, tensile and creep rupture tests have been performed using specimens experienced various thermal cycles to investigate the detailed mechanism causing low hardness values of 150 to 170 Hv and the minimum hardness requirement from a standpoint of tensile and allowable stresses. Low hardness values were mainly attributed to the formation of ferrite structure on cooling after heating at intercritical temperature just above the Ac1, 850 .deg. C. Ferrite transformation on cooling after intercritical heating occurred even at the relatively faster cooling compared to normal heating above the Ac3 since the nose of ferrite transformation in the CCT curve moved to the left due to the very low carbon content in austenite phase formed at intercritical temperature. Low hardness value of 160's Hv occurred occasionally in practical applications was observed at a cooling rate of below 0.167 deg. C/sec(10 .deg. C/min) after intercritical heating. At least 190 Hv of hardness values or more were needed to satisfy tensile properties and maximum allowable stresses specified in ASME B and PV code.

  1. CHRONIC FATIGUE SYNDROME

    Directory of Open Access Journals (Sweden)

    Manabendra Nayak

    2017-11-01

    Full Text Available BACKGROUND Chronic Fatigue Syndrome (CFS is a complicated disorder characterized by extreme fatigue which worsens the physical or mental activity. Of all chronic illnesses, CFS is one of the most mysterious, unlike infections, it has no clear cause. The large majority of cases are said to occur between the age of 18 and 60 years, the mean age being 35 years. Cases are recognised all over the world. Most are sporadically found, but many clusters have also been reported. Chronic fatigue syndrome is a disorder of unknown etiology, which probably has an infectious basis with immunological manifestation. One or more viruses have been implicated as the cause of CFS excluding Epstein-Barr virus (EBV, but no causal relationship between any virus and CFS has been proven. It is now believed that CFS is not specific to one pathogenic agent but could be a state of chronic immune activation, possibly of polyclonal activity of B-lymphocytes, initiated by virus. Diagnostic imaging studies have also provided preliminary data to suggest that patients with CFS may have neurologic abnormalities. Magnetic resonance imaging has shown the presence of cerebral lesion in white matter, predominantly in frontal lobe. Patients with CFS presents with signs and symptoms similar to those of most common viral infections. The signs and symptoms of CFS can last for months or years. Since there is no known cure for CFS, treatment is supportive. Numerous clinical trials of pharmacologic agents have been conducted but no definitive therapeutic benefit has been identified. To date, no type of therapy has been shown to attenuate the cause of the disease. Instead, treatment protocol tends to focus on ameliorating the symptoms of the condition rather than seeking to cure the condition.

  2. The role of human fatigue factor towards maritime casualties

    OpenAIRE

    Xhelilaj Ermal; Lapa Kristofor

    2010-01-01

    The international studies on maritime accidents has shown that fatigue is continuing to be either the main cause or a contributory factor in a considerable number of casualties at sea resulting in the loss of life and damage to the environment and property. In fact, fatigue??s detrimental role toward performance at work is leading to errors being made and consequently resulting in fatalities. In light of these considerations, fatigue issue is of great importance to seafarers, the shipping ind...

  3. X-ray computed microtomography characterizes the wound effect that causes sap flow underestimation by thermal dissipation sensors.

    Science.gov (United States)

    Marañón-Jiménez, S; Van den Bulcke, J; Piayda, A; Van Acker, J; Cuntz, M; Rebmann, C; Steppe, K

    2018-02-01

    Insertion of thermal dissipation (TD) sap flow sensors in living tree stems causes damage of the wood tissue, as is the case with other invasive methods. The subsequent wound formation is one of the main causes of underestimation of tree water-use measured by TD sensors. However, the specific alterations in wood anatomy in response to inserted sensors have not yet been characterized, and the linked dysfunctions in xylem conductance and sensor accuracy are still unknown. In this study, we investigate the anatomical mechanisms prompting sap flow underestimation and the dynamic process of wound formation. Successive sets of TD sensors were installed in the early, mid and end stage of the growing season in diffuse- and ring-porous trees, Fagus sylvatica (Linnaeus) and Quercus petraea ((Mattuschka) Lieblein), respectively. The trees were cut in autumn and additional sensors were installed in the cut stem segments as controls without wound formation. The wounded area and volume surrounding each sensor was then visually determined by X-ray computed microtomography (X-ray microCT). This technique allowed the characterization of vessel anatomical transformations such as tyloses formation, their spatial distribution and quantification of reduction in conductive area. MicroCT scans showed considerable formation of tyloses that reduced the conductive area of vessels surrounding the inserted TD probes, thus causing an underestimation in sap flux density (SFD) in both beech and oak. Discolored wood tissue was ellipsoidal, larger in the radial plane, more extensive in beech than in oak, and also for sensors installed for longer times. However, the severity of anatomical transformations did not always follow this pattern. Increased wound size with time, for example, did not result in larger SFD underestimation. This information helps us to better understand the mechanisms involved in wound effects with TD sensors and allows the provision of practical recommendations to reduce

  4. Investigating Potential Causes for An Abrupt Change of Thermal State in Earth's Upper Mantle During the Great Oxygenation Event

    Science.gov (United States)

    Li, M.; McNamara, A. K.

    2014-12-01

    The oxygenic photosynthesis might have well evolved about 3 billion years ago, but there seems no great increase of atmospheric oxygen until the great oxygenation event (GOE) at about 2.4 Ga. One possibility for the suppressing of atmospheric oxygen level before the GOE is through consumption of oxygen by reduced volcanic gasses. The amount of atmospheric oxygen that could be consumed by volcanic gases depends on the absolute amount of volcanic gases as well as the redox state of the upper mantle. Evidence from the redox sensitive V/Sc ratio have shown that the redox state of the upper mantle have remained constant for the last 3.5 billion years (e.g., Li and Lee, 2004). If so, abrupt changes in thermal state of Earth's upper mantle could explain the rapid changes of degassing rate at the time of GOE. The Earth's lowermost mantle has been shown to be compositionally heterogeneous, which could be caused by the presence of dense, primordial material resulting from early differentiation processes. An important question is how do chemical heterogeneities in the lowermost mantle influence the secular cooling of the upper mantle. Here, we performed numerical calculations to explore the effects of themochemical convection on the thermal evolution of Earth's upper mantle. A large parameter space is explored, with varying Rayleigh number, viscosity, internal heating and density of chemical heterogeneities. We start with an initially hot mantle with a layer of dense material in the lowermost mantle. We found that when the mantle is hot, the dense material remains layered and covers the entire CMB, leading to low CMB heat flux. In this stage, the upper mantle cools down rapidly. However, as the mantle cools, the dense material is swept into discrete thermochemical piles by cold downwellings, leading to increasing CMB heat flux. The cooling rate of the mantle is temporarily reduced as this transition occurs. This occurs at a time consistent with the GOE event. Li, Z. X. A. and

  5. Proximal and distal muscle fatigue differentially affect movement coordination.

    Directory of Open Access Journals (Sweden)

    Jeffrey C Cowley

    Full Text Available Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proximal (shoulder flexor or distal (finger flexor muscles. Pre/Post changes in trunk, shoulder, elbow, and wrist kinematics were compared to determine how proximal and distal fatigue affected multi-joint movement patterns and variability. Proximal fatigue caused a significant increase (7°, p < 0.005 in trunk lean and velocity, reduced humeral elevation (11°, p < 0.005, and increased elbow flexion (4°, p < 0.01. In contrast, distal fatigue caused small but significant changes in trunk angles (2°, p < 0.05, increased velocity of wrench movement relative to the hand (17°/s, p < 0.001, and earlier wrist extension (4%, p < 0.005. Movement variability increased at proximal joints but not distal joints after both fatigue protocols (p < 0.05. Varying movements at proximal joints may help people adapt to fatigue at either proximal or distal joints. The identified differences between proximal and distal muscle fatigue adaptations could facilitate risk assessment of occupational tasks.

  6. Estimation of consumption of the useful life in the nozzles of a gas turbine by the phenomenon of thermal fatigue; Estimacion de consumo de vida util en las toberas de una turbina de gas por el fenomeno de fatiga termica

    Energy Technology Data Exchange (ETDEWEB)

    Perez Hernandez, Efrain [Centro Nacional de Investigacion y Desarrollo Tecnologico (Cenidet), Cuernavaca, Morelos (Mexico); Mazur C, Zdzislaw; Garcia Illescas, R. [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2007-11-15

    The estimation of the useful life in the hot components of the gas turbines such as nozzles and blades is important since they undergo critical temperature changes which produce thermo-mechanical fatigue during the starts, stops and load changes for estimation of the useful life in the nozzles of a gas turbine made of a cobalt base alloy FSX-414 on which cracks have been developed during the operation. The visual inspection and metallography of the nozzle revealed many cracks by thermo-mechanical fatigue in the blade surface besides the deterioration of the alloy. In the grain boundaries it was also found a continuous carbide film and also increment of the fraction of carbides within grains. This dense and continuous carbide network reduces the ductility and increases the fragility, along with the reduction of impact energy (Charpy), facilitates the initiation and crack propagation. The initiation and crack propagation in the alloy were due to a mechanism of thermal fatigue and termofluency that was facilitated by fragility of the material due to the deterioration previously mentioned and at significant levels of thermo-mechanical efforts. In the present article the results of thermal stress analysis from the results of temperature obtained of previous studies of an analysis of heat transference and flow of fluids by means of the Star-CD program based on finite volume. It is presented the used methodology and the stress distribution, which were used for the fatigue analysis for the estimation of the useful life. For that purpose a model of finite elements in program NISA, as well as the program of fatigue analysis nCode was used. For the counting of the cycle the method of Rainflow was used and the models of life by fatigue of Manson-Coffin, Basquin, Morrow and Smih-Watson-Topper were compared. The variation of the mechanical properties with the temperature of the super alloy used in those hot components showed its great influence in the results of the fatigue

  7. On a possible bias in elemental carbon measurements with the Sunset thermal/optical carbon analyser caused by unstable laser signal

    NARCIS (Netherlands)

    Ammerlaan, B.A.J.; Jedynska, A.D.; Henzing, J.S.; Holzinger, R.

    2015-01-01

    We present results that demonstrate a possible bias in the fractioning of total carbon (TC) into elemental carbon (EC) and organic carbon (OC) for measurements with the Sunset Laboratory Inc. Thermal/Optical Carbon Aerosol Analyser. The bias is caused by an unstable laser transmission signal. The

  8. Lactic acid – the innocent culprit of muscle fatigue | Shalayel | Sudan ...

    African Journals Online (AJOL)

    What causes muscle fatigue? Is lactic acid considered to be a major culprit in the underlying mechanisms of muscle fatigue? These are very important questions and the answers are difficult and sophisticated. For decades, lactic acid was the major culprit of muscle fatigue. This review reveals that muscle fatigue would occur ...

  9. Fatigue and radiotherapy. A literature review; Fatigue et radiotherapie. Revue de la litterature

    Energy Technology Data Exchange (ETDEWEB)

    Dilhuydy, J.M.; Ouhtatou, F.; Laporte, C.; Nguyen, T.V.F.; Vendrely, V. [Institut Bergonie Centre Regional de Lutte Contre le Cancer, 33 - Bordeaux (France); Dilhuydy, J.M. [Federation Nationale des Centres de Lutte Contre le Cancer, FNCLCC, Groupe Rehabilitation, 75 - Paris (France); Dilhuydy, M.S. [Hopital Saint-Andre, Service de Medecine Interne, 33 - Bordeaux (France)

    2001-11-01

    Fatigue is a common complaint for the cancer patient during and after radiotherapy, according to the published studies. Fatigue is a subjective symptom mostly underestimated by oncologists and other care givers. Etiology is complex, poorly understood in spite of obvious causes like insomnia, nausea, pain, depression, psychological distress, anemia, hypothyroidism, menopause disturbances, treatment adverse effects. Fatigue presents multi-factorial and multidimensional aspects. To evaluate it, many tools can be used as single-item, unidimensional and multidimensional instruments. Practically, the open discussion with the patient throughout radiotherapy is essential to define it. Taking charge fatigue requires its acknowledgement by radiotherapist, treatment of associated symptoms with a multidisciplinary approach. (authors)

  10. [Therapy of fatigue in multiple sclerosis : A treatment algorithm].

    Science.gov (United States)

    Veauthier, C; Paul, F

    2016-12-01

    Fatigue is one of the most frequent symptoms of multiple sclerosis (MS) and one of the main reasons for underemployment and early retirement. The mechanisms of MS-related fatigue are unknown but comorbid disorders play a major role. Anemia, diabetes, side effects of medication and depression should be ruled out. Moreover, excessive daytime sleepiness (EDS) should be differentiated from fatigue. No approved medicinal therapy of MS fatigue is currently available. Presentation of current treatment strategies with a particular focus on secondary fatigue due to sleep disorders. A review of the literature was carried out. All MS patients suffering from fatigue should be questioned with respect to EDS and if necessary sleep medical investigations should be carried out; however, pure fatigue without accompanying EDS can also be caused by a sleep disorder. Medications, particularly freely available antihistamines, can also increase fatigue. Furthermore, anemia, iron deficits, diabetes and hypothyroidism should be excluded. Self-assessment questionnaires show an overlap between depression and fatigue. Several studies have shown that cognitive behavioral therapy and various psychotherapeutic measures, such as vertigo training, progressive exercise training and individualized physiotherapy as well as fatigue management interventions can lead to a significant improvement of MS-related fatigue. There is currently no medication which is suitable for treatment of fatigue, with the exception of fampridine for the treatment of motor functions and motor fatigue.

  11. Evaluating cyclic fatigue of sealants during outdoor testing

    Science.gov (United States)

    R. Sam Williams; Steven Lacher; Corey Halpin; Christopher White

    2009-01-01

    A computer-controlled test apparatus (CCTA) and other instrumentation for subjecting sealant specimens to cyclic fatigue during outdoor exposure was developed. The CCTA enables us to use weather-induced conditions to cyclic fatigue specimens and to conduct controlled tests in-situ during the outdoor exposure. Thermally induced dimensional changes of an aluminum bar...

  12. Fatigue and factors related to fatigue in rheumatoid arthritis: a systematic review

    NARCIS (Netherlands)

    Nikolaus, Stephanie; Bode, Christina; Taal, Erik; van de Laar, Mart A F J

    2013-01-01

    Objective Although patients with rheumatoid arthritis (RA) experience fatigue, little is known about its causes and consequences, and a fully developed theoretical model explaining the experience of fatigue in RA is lacking. Our goal was to systematically review studies in RA that examined factors

  13. Fluid-structure interaction analysis for pressurizer surge line subjected to thermal stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong Gu [Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338 (Korea, Republic of); Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Jhung, Myung Jo, E-mail: mjj@kins.re.k [Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338 (Korea, Republic of); Chang, Soon Heung [Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2011-01-15

    Research highlights: Temperature of surge line due to stratified flow is defined using CFD analysis. Fluid-structure interaction analysis is performed to investigate the response characteristics due to thermal stress. Fatigue usage factors due to thermal stratification are relatively low. Simplifying temperature distribution in surge line is not always conservative. - Abstract: Serious mechanical damages such as cracks and plastic deformations due to excessive thermal stress caused by thermal stratification have been experienced in several nuclear power plants. In particular, the thermal stratification in the pressurizer surge line has been addressed as one of the significant safety and technical issues. In this study, a detailed unsteady computational fluid dynamics (CFD) analysis involving conjugate heat transfer analysis is performed to obtain the transient temperature distributions in the wall of the pressurizer surge line subjected to stratified internal flows either during out-surge or in-surge operation. The thermal loads from CFD calculations are transferred to the structural analysis code which is employed for the thermal stress analysis to investigate the response characteristics, and the fatigue analysis is ultimately performed. In addition, the thermal stress and fatigue analysis results obtained by applying the realistic temperature distributions from CFD calculations are compared with those by assuming the simplified temperature distributions to identify some requirements for a realistic and conservative thermal stress analysis from a safety point of view.

  14. Techniques for Mitigating Thermal Fatigue Degradation, Controlling Efficiency, and Extending Lifetime in a ZnO Thermoelectric Using Grain Size Gradient FGMs

    Science.gov (United States)

    Cramer, Corson L.; Li, Wenjie; Jin, Zhi-He; Wang, Jue; Ma, Kaka; Holland, Troy B.

    2018-01-01

    A functionally graded material (FGM) in terms of grain size gradation is fabricated using zinc oxide (ZnO) with spark plasma sintering and an additive manufacturing technique by diffusion bonding layers of material sintered at different temperatures to achieve a thermoelectric generator (TEG) material that can dissipate heat well and retain high energy conversion efficiency for longer-lasting and comparably efficient TEGs. This FGM is compared to a previously made FGM with continuous grain size gradation. Uniform and graded grain size conditions are modeled for thermoelectric output by using thermoelectric properties of the uniform grain size as well as the varying properties seen in the FGMs. The actual thermoelectric output of the samples is measured and compared to the simulations. The grain size has a large effect on the efficiency and efficiency range. The samples are thermally cycled with a fast heating rate to test the thermal stress robustness and degradation, and the resistance at the highest temperature is measured to indicate degradation from thermal stress. The measured efficiency after cycling shows that the FGMs survive longer lifetime than that with uniform small grains.

  15. A Review on Fatigue Driving Detection

    Directory of Open Access Journals (Sweden)

    Shi Sheng-Yang

    2017-01-01

    Full Text Available The socialization of automobile development has brought great convenience to people’s travel. However, the rapid increase in the number of vehicles has also caused a series of problems. The increase in traffic accidents has brought great social casualties and economic losses. Fatigue driving, which is an important factor in the traffic accident, has aroused people’s attention. This paper reviews all kinds of fatigue driving detection methods at present; compares various fatigue driving detection methods in terms of accuracy, real-time and cost; analyses the advantages and disadvantages of various methods; introduces the application of fatigue detection system in automobile; summarizes the current deficiencies and future development trends in the field of fatigue driving detection. The future research of this field will be more to the data fusion, computer vision and deep learning.

  16. Continuous fatigue crack monitoring of bridges: Long-Term Electrochemical Fatigue Sensor (LTEFS)

    Science.gov (United States)

    Moshier, Monty A.; Nelson, Levi; Brinkerhoff, Ryan; Miceli, Marybeth

    2016-04-01

    Fatigue cracks in steel bridges degrade the load-carrying capacity of these structures. Fatigue damage accumulation caused by the repetitive loading of everyday truck traffic can cause small fatigue cracks initiate. Understanding the growth of these fatigue cracks is critical to the safety and reliability of our transportation infrastructure. However, modeling fatigue in bridges is difficult due to the nature of the loading and variations in connection integrity. When fatigue cracks reach critical lengths failures occur causing partial or full closures, emergency repairs, and even full structural failure. Given the aging US highway and the trend towards asset management and life extension, the need for reliable, cost effective sensors and monitoring technologies to alert bridge owners when fatigue cracks are growing is higher than ever. In this study, an innovative Long-Term Electrochemical Fatigue Sensor (LTEFS) has been developed and introduced to meet the growing NDT marketplace demand for sensors that have the ability to continuously monitor fatigue cracks. The performance of the LTEFS has been studied in the laboratory and in the field. Data was collected using machined specimens with different lengths of naturally initiated fatigue cracks, applied stress levels, applied stress ratios, and for both sinusoidal and real-life bridge spectrum type loading. The laboratory data was evaluated and used to develop an empirically based algorithm used for crack detection. Additionally, beta-tests on a real bridge structure has been completed. These studies have conclusively demonstrated that LTEFS holds great potential for long-term monitoring of fatigue cracks in steel structures

  17. Cancer related fatigue syndrome in neoplastic diseases

    Directory of Open Access Journals (Sweden)

    Magdalena Franc

    2014-12-01

    Full Text Available 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.

  18. Ultrahigh lattice thermal conductivity in topological semimetal TaN caused by large acoustic-optical gap.

    Science.gov (United States)

    Guo, San-Dong; Liu, Bang-Gui

    2018-01-29

    Topological semimetal may have potential applications like topological qubits, spintronics and quantum computations. Efficient heat dissipation is a key factor for the reliability and stability of topological semimetal-based nano-electronics devices, which is closely related to high thermal conductivity. In this work, the elastic properties and lattice thermal conductivity of TaN are investigated by first-principles calculations and the linearized phonon Boltzmann equation within the single-mode relaxation time approximation (RTA). According to the calculated bulk modulus, shear modulus and $C_{44}$, TaN can be regarded as a potential incompressible and hard material. The room-temperature lattice thermal conductivity is predicted to be 838.62 $\\mathrm{W m^{-1} K^{-1}}$ along a axis and 1080.40 $\\mathrm{W m^{-1} K^{-1}}$ along c axis, showing very strong anisotropy. It is found that the lattice thermal conductivity of TaN is several tens of times higher than one of other topological semimetal, such as TaAs, MoP and ZrTe, which is due to very longer phonon lifetimes for TaN than other topological semimetal. The very different atomic masses of Ta and N atoms lead to a very large acoustic-optical band gap, and then prohibits the scattering between acoustic and optical phonon modes, which gives rise to very long phonon lifetimes. Calculated results show that isotope scattering has little effect on lattice thermal conductivity, and that phonon with mean free path(MFP) larger than 20 (80) $\\mathrm{\\mu m}$ along a (c) direction at 300 K has little contribution to the total lattice thermal conductivity. This work implies that TaN-based nano-electronics devices may be more stable and reliable due to efficient heat dissipation, and motivate further experimental works to study lattice thermal conductivity of TaN. © 2018 IOP Publishing Ltd.

  19. Chronic fatigue syndrome

    National Research Council Canada - National Science Library

    Gonthier, Ariane; Favrat, Bernard

    2015-01-01

    Chronic fatigue syndrome (CFS) is a debilitating disorder, characterized by a severe, persistant and unexplained fatigue, which can be associated with diffuse pain, sleep difficulties, neurocognitive and neurovegetative troubles...

  20. Insomnia and Fatigue

    Science.gov (United States)

    ... in turn leads to fatigue, may affect your self-esteem, mood, emotions, relationships and work. But you don’ ... Loss Insomnia and Fatigue Menopausal Symptoms Secondary Cancers Sexual Side Effects Living With HR-Positive Breast Cancer ...

  1. Work fatigue in urban bus drivers

    Directory of Open Access Journals (Sweden)

    Teresa Makowiec-Dąbrowska

    2015-10-01

    Full Text Available Background: Bus drivers are a special group of professional drivers who are at a very high risk of fatigue. The aim of the study was to examine whether the driver’s subjective assessment of fatigue allows for the determination of its level and identification of its causes. Material and Methods: The study group comprised 45 randomly selected bus drivers (mean age – 43.7±7.9 years, period of employment as drivers – 14.7±8.6 years. Examinations were performed in all subjects four times – before and after work on the “easy” route (outside the city center, small traffic intensity and before and after work on the “difficult” route (city center, heavy traffic. The fatigue test questionnaire, based on the list of symptoms of fatigue prepared by the Japan Research Committee of Fatigue, was used in the study. Results: The rating of fatigue after the work was significantly higher than that before the work. The profile of fatigue after work was not influenced by the type of route, but the assessment of most symptoms of fatigue reached a higher level after the “difficult” routes and the differences were statistically significant for 7 symptoms. Only the ratings of leg fatigue, feeling of heaviness, and the necessity to squint eyes and gaze with effort reached the higher levels after driving the “easy” routes. It has been found that the level of fatigue was significantly correlated with the job characteristics (driving time, the length of the route, number of stops, etc. and with the abundance of food ingested and type of beverage (coffee vs. others drunk prior to driving. Conclusions: The questionnaire used in our study to assess the subjective feeling of fatigue has proved to be a sensitive and useful tool for indicating the level and causes of fatigue. The relationship between the symptoms of fatigue and the characteristics of job and lifestyle shows that actions must be taken by both the employers and employees to prevent fatigue

  2. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, Michael Havbro; Sørensen, John Dalsgaard; Kroon, I. B.

    1993-01-01

    This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue ...

  3. Patients' perceptions of fatigue in rheumatoid arthritis: overwhelming, uncontrollable, ignored.

    Science.gov (United States)

    Hewlett, Sarah; Cockshott, Zoë; Byron, Margaret; Kitchen, Karen; Tipler, Sue; Pope, Denise; Hehir, Maggie

    2005-10-15

    Fatigue is commonly reported by patients with rheumatoid arthritis (RA) but is rarely a treatment target. The aim of this study was to explore the concept of fatigue as experienced by patients with RA. Fifteen patients with RA and fatigue (> or =7 on a 10-cm visual analog scale) were individually interviewed and asked about the description, cause, consequence, and management of fatigue. Transcripts were systematically analyzed by 2 researchers independently, relevant phrases were coded, and earlier transcripts were checked for the emerging codes. A random sample of analyses were independently reviewed. A total of 191 codes arising from the data were grouped into 46 categories and overarching themes. Vivid descriptions reflect 2 types of fatigue: severe weariness and dramatic overwhelming fatigue. RA fatigue is different from normal tiredness because it is extreme, often not earned, and unresolving. Participants described physical, cognitive, and emotional components and attributed fatigue to inflammation, working the joints harder, and unrefreshing sleep. Participants described far-reaching effects on physical activities, emotions, relationships, and social and family roles. Participants used self-management strategies but with limited success. Most did not discuss fatigue with clinicians but when they did, they felt it was dismissed. Participants held negative views on the management of fatigue. The data show that RA fatigue is important, intrusive, and overwhelming, and patients struggle to manage it alone. These data on the complexity of fatigue experiences will help clinicians design measures, interventions, and self-managment guidance.

  4. Conditioning monitoring by microstructural evaluation of cumulative fatigue damage

    Science.gov (United States)

    Fukuoka, C.; Nakagawa, Y. G.; Lance, J. J.; Pangborn, R. N.

    1996-12-01

    The objective of this work is to evaluate the damage induced below and above the fatigue limit (Δ σ t =360 MPa) in pressure vessel steels, such as SA508. Fatigue damage was induced in samples taken from an SA508 steel plate by various loading histories in order to examine the influence of prior cyclic loading below the fatigue limit. Cell-to-cell misorientation differences were measured by the selected area diffraction (SAD) method. Surface cracking was also studied by the replication method. Small cracks were observed after precycling both below and above the fatigue limit. It was, however, found that fatigue test bars had a longer lifetime after precycling below the fatigue limit, while precycling above the fatigue limit caused other specimens to fail even when subsequently cycled below the fatigue limit. Cell-to-cell misorientation usually increases with accumulation of fatigue damage, but it was found that the misorientations measured after precycling below the fatigue limit decreased again at the beginning of the subsequent cycling above the fatigue limit. It should be noted that the misorientation at failure was always about 4 to 5 deg, regardless of loading histories. Misorientation showed good correlation with the fatigue lifetime of the samples.

  5. Development and characterization of fatigue resistant Aramid reinforced aluminium laminates (ARALL) for fatigue Critical aircraft components

    Science.gov (United States)

    Qaiser, M. H.; Umar, S.; Nauman, S.

    2014-06-01

    The structural weight of an aircraft has always been a controlling parameter that governs its fuel efficiency and transport capacity. In pursuit of achieving light-weight aircraft structures, high design stress levels have to be adopted and materials with high specific strength such as Aluminum etc. are to be deployed. However, an extensive spectrum of fatigue load exists at the aircraft wings and other aerodynamic components that may cause initiation and propagation of fatigue cracks and concludes in a catastrophic rupture. Fatigue is therefore the limiting design parameter in such cases and materials with high fatigue resistance are then required. A major improvement in the fatigue behavior was observed by laminating Kevlar fibers with Aluminum using epoxy. ARALL (Aramid Reinforced ALuminum Laminates) is a fatigue resistant hybrid composite that consists of layers of thin high strength aluminum alloy sheets surface bonded with aramid fibers. The intact aramid fibers tie up the fatigue cracks, thus reducing the stress intensity factor at the crack tip as a result of which the fatigue properties of can be enhanced with orders of magnitude as compared to monolithic high strength Aluminum alloy sheets. Significant amount of weight savings can be achieved in fatigue critical components in comparison with the traditional materials used in aircraft.

  6. Velocity-specific fatigue: quantifying fatigue during variable velocity cycling.

    Science.gov (United States)

    Gardner, A Scott; Martin, David T; Jenkins, David G; Dyer, Iain; Van Eiden, Jan; Barras, Martin; Martin, James C

    2009-04-01

    Previous investigators have quantified fatigue during short maximal cycling trials ( approximately 30 s) by calculating a fatigue index. Other investigators have reported a curvilinear power-pedaling rate relationship during short fatigue-free maximal cycling trials (track bicycles. Data from the initial portion of maximal acceleration were used to establish maximal power-pedaling rate relationships. Fatigue was quantified three ways: 1) traditional fatigue index, 2) fatigue index modified to account for the power-pedaling rate relationship (net fatigue index), and 3) work deficit, the difference between actual work done and work that might have been accomplished without fatigue. Fatigue index (55.4% +/- 6.4%) was significantly greater than net fatigue index (41.0% +/- 7.9%, P cycling. These measures can be used to compare fatigue during different fatigue protocols, including world-class sprint cycling competition. Precise quantification of fatigue during elite cycling competition may improve evaluation of training status, gear ratio selection, and fatigue resistance.

  7. The comparison of thermal tissue injuries caused by ultrasonic scalpel and electrocautery use in rabbit tongue tissue

    Directory of Open Access Journals (Sweden)

    Guclu Kaan Beriat

    2012-08-01

    Full Text Available The aim of this study compares to the increase in tissue temperature and the thermal histological effects of ultrasonic scalpel, bipolar and unipolar electrosurgery incisions in the tongue tissue of rabbits. This study evaluates the histopathological changes related to thermal change and the maximum temperature values in the peripheral tissue brought about by the incisions carried out by the three methods in a comparative way. To assess thermal tissue damage induced by the three instruments, maximum tissue temperatures were measured during the surgical procedure and tongue tissue samples were examined histopathologically following the surgery. The mean maximum temperature values of the groups were 93.93±2.76 C° for the unipolar electrocautery group, whereas 85.07±5.95 C° for the bipolar electrocautery group, and 108.23±7.64 C° for the ultrasonic scalpel group.There was a statistically significant relationship between the increase in maximum temperature values and the separation among tissue layers, edema, congestion, necrosis, hemorrhage, destruction in blood vessel walls and fibrin accumulation, and between the existence of fibrin thrombus and tissue damage depth (p<0.05.It was concluded that the bipolar electrocautery use gives way to less temperature increase in the tissues and less thermal tissue damage in comparison to the other methods.

  8. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1996-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Fatigue failure is found to depend both on the total time under load and on the number of cycles.Recent accelerated fatigue research on wood is reviewed, and a discrepancy between...... to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation between stiffness reduction...

  9. Fatigue in healthy and diseased individuals.

    Science.gov (United States)

    Finsterer, Josef; Mahjoub, Sinda Zarrouk

    2014-08-01

    Although fatigue is experienced by everyone, its definition and classification remains under debate. A review of the previously published data on fatigue. Fatigue is influenced by age, gender, physical condition, type of food, latency to last meal, mental status, psychological conditions, personality type, life experience, and the health status of an individual. Fatigue may not only be a symptom but also a measurable and quantifiable dimension, also known as fatigability. Additionally, it may be classified as a condition occurring at rest or under exercise or stress, as physiologic reaction or pathologic condition, as spontaneous phenomenon or triggerable state, as resistant or irresistant to preconditioning, training, or attitude, as prominent or collateral experience, and as accessible or inaccessible to any type of treatment or intervention. Fatigue may be the sole symptom of a disease or one among others. It may be also classified as acute or chronic. Quantification of fatigability is achievable by fatigue scores, force measurement, electromyography, or other means. Fatigue and fatigability need to be delineated from conditions such as sleepiness, apathy, exhaustion, exercise intolerance, lack of vigor, weakness, inertia, or tiredness. Among neurological disorders, the prevalence of fatigue is particularly increased in multiple sclerosis, amyotrophic lateral sclerosis, Parkinson disease, traumatic brain injury, stroke, and bleeding and also in neuromuscular disorders. Fatigue may be influenced by training, mental preconditioning, or drugs. Fatigue needs to be recognized as an important condition that is not only a symptom but may also be quantified and can be modified by various measures depending on the underlying cause. © The Author(s) 2013.

  10. Determinants of seafarers’ fatigue

    DEFF Research Database (Denmark)

    Bøggild Dohrmann, Solveig; Leppin, Anja

    2017-01-01

    Purpose: Fatigue jeopardizes seafarer’s health and safety. Thus, knowledge on determinants of fatigue is of great importance to facilitate its prevention. However, a systematic analysis and quality assessment of all empirical evidence specifically for fatigue are still lacking. The aim...... in the review. The main reason for exclusion was fatigue not being the outcome variable. Results: Most evidence was available for work time-related factors suggesting that working nights was most fatiguing, that fatigue levels were higher toward the end of watch or shift, and that the 6-h on–6-h off watch...... system was the most fatiguing. Specific work demands and particularly the psychosocial work environment have received little attention, but preliminary evidence suggests that stress may be an important factor. A majority of 12 studies were evaluated as potentially having a high risk of bias. Conclusions...

  11. Basic mechanisms of tendon fatigue damage

    OpenAIRE

    Neviaser, Andrew; Andarawis-Puri, Nelly; Flatow, Evan

    2012-01-01

    Pathologic processes intrinsic and extrinsic to the tendons have been proposed as the underlying cause of rotator cuff disease, but the precise etiology is not known. Tear formation is, in part, attributable to the accumulation of subrupture tendon fatigue damage. We review the molecular, mechanical, and structural changes induced in tendons subjected to controlled amounts of fatigue loading in an animal model of early tendinopathy. The distinct tendon responses to low and moderate levels of ...

  12. Material fatigue in high pressure piping

    Energy Technology Data Exchange (ETDEWEB)

    Brunne, W.C. [Pro Novum, Research and Technological Services, Ltd, Katowice, (Poland)

    1998-12-31

    The present paper describes a type of damage to four-way cross pieces on live steam and reheated steam pipelines. The results of metallographic examination and strength tests are presented. The occurring mechanisms of material degradation, i.e. low-cycle fatigue and hydrogen corrosion are discussed. The both mechanisms result in the corrosion fatigue of the material causing the failure of cross pieces. A new design of cross piece was proposed. (orig.) 5 refs.

  13. Fatigue in chronic inflammation - a link to pain pathways.

    Science.gov (United States)

    Louati, Karine; Berenbaum, Francis

    2015-10-05

    Fatigue is a frequent symptom in several inflammatory diseases, particularly in rheumatic diseases. Elements of disease activity and cognitive and behavior aspects have been reported as causes of fatigue in patients with rheumatoid arthritis. Fatigue could be associated with activity of inflammatory rheumatism. Indeed, biologic agents targeting inflammatory cytokines are effective in fatigue. Fatigue is also associated with pain and depressive symptoms. Different pathways could be involved in fatigue and interact: the immune system with increased levels of pro-inflammatory cytokines (interleukin-1 and -6 and tumor necrosis factor alpha), dysregulation of the hypothalamic-pituitary-adrenal axis and neurological phenomena involving the central and autonomic nervous systems. A pro-inflammatory process could be involved in pain and behavioral symptoms. Inflammation could be a common link between fatigue, pain, and depression.

  14. Construction Worker Fatigue Prediction Model Based on System Dynamic

    Directory of Open Access Journals (Sweden)

    Wahyu Adi Tri Joko

    2017-01-01

    Full Text Available Construction accident can be caused by internal and external factors such as worker fatigue and unsafe project environment. Tight schedule of construction project forcing construction worker to work overtime in long period. This situation leads to worker fatigue. This paper proposes a model to predict construction worker fatigue based on system dynamic (SD. System dynamic is used to represent correlation among internal and external factors and to simulate level of worker fatigue. To validate the model, 93 construction workers whom worked in a high rise building construction projects, were used as case study. The result shows that excessive workload, working elevation and age, are the main factors lead to construction worker fatigue. Simulation result also shows that these factors can increase worker fatigue level to 21.2% times compared to normal condition. Beside predicting worker fatigue level this model can also be used as early warning system to prevent construction worker accident

  15. Chronic fatigue syndrome: A review

    Directory of Open Access Journals (Sweden)

    Srinivas Balachander

    2014-01-01

    Full Text Available Chronic fatigue syndrome is a disorder that is characterized by severe and debilitating fatigue of at least 6 months duration not explained on the basis of medical and psychiatric illnesses and has other associated characteristics. The disorder has a resemblance to many other disorders described in the past including myalgic encephalitis and post-infective fatigue; however, the term itself and the criteria for diagnosing this disorder were first laid out in 1988. The disorder has received attention from a wide range of clinicians and researchers. The mechanism of causation of this disorder has been poorly understood, though biological, psychological and social factors seem to play a role. The disorder causes significant impairment and is highly comorbid with other disorders. Non-pharmacological measures like graded exercise therapy and cognitive behavior therapy seem to work better for treatment than pharmacological measures. This narrative review takes an overview of chronic fatigue syndrome from a generalist standpoint and looks into the clinical features, etiopathogenesis and management of this disorder.

  16. Muscular fatigue: considerations for dance.

    Science.gov (United States)

    Wyon, Matthew A; Koutedakis, Yiannis

    2013-01-01

    Muscular fatigue can be defined as the failure to maintain an expected power output. It is a multifaceted phenomenon that incorporates metabolic, neural and neuromuscular components, among others. Metabolic causes of fatigue are associated with the ability to maintain energy supply during exercise, the speed at which homeostasis is achieved post-exercise, and the effects of high intensity exercise by-products on the peripheral neuromuscular system. Research has indicated that the central nervous system plays a protective role in preventing catastrophic muscle damage by reducing the intensity and frequency of propagation founded on biofeedback from the muscle cells. The duration and particularly the type of physical activity play a role in the development of muscle fatigue, with impact or weightbearing exercises, such as dance, producing increased symptoms compared to non-impact or non-weightbearing equivalents. The effects of prolonged exercise and the associated increased levels of muscle fatigue that may lead to compromises in neuromuscular propagation need to be considered in dance.

  17. Evaluating the Thermal Pollution Caused by Wastewaters Discharged from a Chain of Coal-Fired Power Plants along a River

    Directory of Open Access Journals (Sweden)

    Marc A. Rosen

    2015-05-01

    Full Text Available Reliable and safe operation of a coal-fired power plant is strongly linked to freshwater resources, and environmental problems related to water sources and wastewater discharge are challenges for power station operation. In this study, an evaluation on the basis of a wastewater thermal pollution vector is reported for the environmental impact of residual water generated and discharged in the Jiu River during the operation of thermoelectric units of the Rovinari, Turceni and Craiova coal-fired power plants in Romania. Wastewater thermal pollutant vector Plane Projection is applied for assessing the water temperature evolution in the water flow lane created downstream of each power plant wastewater outlet channel. Simulation on the basis of an Electricity of France model, and testing validation of the results for thermoelectric units of 330 MW of these power plants are presented.

  18. Influence de la fatigue thermique et des chocs thermiques sur la ...

    African Journals Online (AJOL)

    13 nov. 2007 ... T.I.G welding process on specimens made out of 42CD4 ferritic steel. The study concerns tree different ... of the test. Key words: thermal fatigue; thermal shocks; austenitic stainless steel; friction; wear; welding. 1. INTRODUCTION ..... Michaud, Simulation expérimentale de la fatigue thermique d'un cylindre ...

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

    Science.gov (United States)

    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 (pfatigue 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

  20. Manipulation specific effects of mental fatigue: evidence from novelty processing and simulated driving.

    Science.gov (United States)

    Massar, Stijn A A; Wester, Anne E; Volkerts, Edmund R; Kenemans, J Leon

    2010-11-01

    Mental fatigue has a wide range of effects on cognitive, behavioral, and motivational measures. It can be expected that specific effects in which fatigue becomes manifest is dependent on the nature of fatigue-inducing activity (e.g., level of control and working memory demands). This study examined how fatigue caused by tasks that differ on the level of working memory demands (0-Back, 2-Back) affects brain function (novelty processing, P3a) and performance (driving). Results showed that fatigue did not affect driving performance. Fatigue did reduce P3a amplitude, but only after 2-Back. P3a was also reduced during driving. The effects of fatigue and driving on P3a were additive. In summary, both driving and fatigue reduced P3a amplitude. Driving effects were always present. Fatigue effects on novelty processing were dependent on the cognitive demands of the fatigue-inducing task. Copyright © 2010 Society for Psychophysiological Research.

  1. Research advances in pathogenesis and management of fatigue in patients with primary biliary cirrhosis

    Directory of Open Access Journals (Sweden)

    ZHAO Jian

    2016-11-01

    Full Text Available Fatigue is one of the most common symptoms of primary biliary cirrhosis (PBC and greatly affects patients′ quality of life. The pathogenesis of fatigue in PBC remains unknown and there are no effective therapeutic methods. This article reviews the latest advances in the pathogenesis and treatment of fatigue in PBC. Studies have shown that the causes of fatigue in PBC include various central and peripheral factors, such as the changes in the brain, sleep disorders, depression, autonomic nervous dysfunction, and abnormal muscle metabolism. Modafinil does not have a definite therapeutic effect in fatigue in PBC. The causes and treatment of fatigue in PBC still need in-depth systematic studies.

  2. Investigation of thermal decomposition as the kinetic process that causes the loss of crystalline structure in sucrose using a chemical analysis approach (part II).

    Science.gov (United States)

    Lee, Joo Won; Thomas, Leonard C; Jerrell, John; Feng, Hao; Cadwallader, Keith R; Schmidt, Shelly J

    2011-01-26

    High performance liquid chromatography (HPLC) on a calcium form cation exchange column with refractive index and photodiode array detection was used to investigate thermal decomposition as the cause of the loss of crystalline structure in sucrose. Crystalline sucrose structure was removed using a standard differential scanning calorimetry (SDSC) method (fast heating method) and a quasi-isothermal modulated differential scanning calorimetry (MDSC) method (slow heating method). In the fast heating method, initial decomposition components, glucose (0.365%) and 5-HMF (0.003%), were found in the sucrose sample coincident with the onset temperature of the first endothermic peak. In the slow heating method, glucose (0.411%) and 5-HMF (0.003%) were found in the sucrose sample coincident with the holding time (50 min) at which the reversing heat capacity began to increase. In both methods, even before the crystalline structure in sucrose was completely removed, unidentified thermal decomposition components were formed. These results prove not only that the loss of crystalline structure in sucrose is caused by thermal decomposition, but also that it is achieved via a time-temperature combination process. This knowledge is important for quality assurance purposes and for developing new sugar based food and pharmaceutical products. In addition, this research provides new insights into the caramelization process, showing that caramelization can occur under low temperature (significantly below the literature reported melting temperature), albeit longer time, conditions.

  3. External cardiac defibrillation does not cause acute histopathological changes typical of thermal injuries in pigs with in situ cerebral stimulation electrodes.

    Science.gov (United States)

    Kolbitsch, Christian; Eisner, Wilhelm; Kleinsasser, Axel; Biebl, Matthias; Fiegele, Thomas; Löckinger, Alexander; Lorenz, Ingo H; Mikuz, Gregor; Moser, Patrizia L

    2004-02-01

    Parkinson's disease patients with long-term L-dopa syndrome may benefit from an implanted cerebral stimulation device. When advanced life support demands cardioversion or defibrillation in these patients, undesired effects of monophasic electroshocks might occur in brain tissue adjacent to the stimulation electrodes (e.g., thermal injury), but also in the stimulation device itself. Thus, in this animal study (n = 6 pigs), we investigated the effects of repeated defibrillation (2 x 200 J [n = 1] and 2 x 360 J [n = 5]) at the implantation site of cerebral stimulation electrodes and on stimulation device function. Repeated external cardiac defibrillation did not cause acute histopathologic changes typical of thermal injury to brain tissue adjacent to the cerebral stimulation electrodes. Functionality of the stimulator device after defibrillation, however, ranged from normal to total loss of function. Therefore, when defibrillation is performed, the greatest possible distance between the defibrillation site and the stimulator device implantation site should be considered. Subsequent testing of the stimulator device's function is mandatory. Repeated cardiac defibrillation did not cause histopathologic changes typical of thermal injury at the implantation site of cerebral stimulation electrodes. The function of the stimulator device after defibrillation, however, ranged from normal to total loss of function.

  4. Train driving efficiency and safety: examining the cost of fatigue.

    Science.gov (United States)

    Dorrian, Jillian; Hussey, Frank; Dawson, Drew

    2007-03-01

    This study investigated the effects of fatigue on train driving using data loggers on 50 locomotives operated by pairs of male train drivers (24-56 years) on an Adelaide-Melbourne corridor. Drivers' work history was used to calculate a fatigue score using Fatigue Audit Interdyne Software. Trains were assigned to one of three groups, based on drivers' maximum fatigue score: low (n = 15), moderate (n = 22) or high (n = 13) fatigue. Changes in driving parameters at different fatigue levels were investigated. A significant (P high group used 9% more fuel than drivers in the low group. As these trains run daily, taking horsepower into account, this represents an approximate extra weekly cost of AUD$3512 using high compared with low fatigue drivers. High fatigue-group drivers used less throttle and dynamic brake and engaged in more heavy brake and maximum speed violations. Comparison of three, 100 km track sub-sections with undulating, flat, and hilly grade indicated that fuel use increases occurred primarily during the undulating sub-section, and heavy brake and maximum speed violations occurred primarily in the flat sub-section. Fatigued driving becomes less well-planned, resulting in reduced efficiency (e.g. increased fuel consumption) and safety (e.g. braking and speeding violations). Fatigue may manifest differentially depending on track grade. In certain areas, fatigue will cause increased fuel use and economic cost, and in others, reduced safety through driving violations. These factors should be carefully examined in future railway operator research.

  5. Radiative heating of carbonaceous near-Earth objects as a cause of thermal metamorphism for CK chondrites

    Science.gov (United States)

    Chaumard, Noël; Devouard, Bertrand; Delbo, Marco; Provost, Ariel; Zanda, Brigitte

    2012-07-01

    Metamorphic CK carbonaceous chondrites display matrix textures that are best explained by a transient thermal event with temperatures in the 550-950 K range and durations in the order of days to years, longer than what is commonly admitted for shock events but shorter than what is required for nuclide decay. We propose that radiative heating of small carbonaceous meteoroids with perihelia close to the Sun could account for the petrological features observed in CK chondrites. Numerical thermal modeling, using favorable known NEOs orbital parameters (perihelion distances between 0.07 and 0.15 AU) and physical properties of CV and CK chondrites (albedo in the range 0.01-0.1, 25% porosity, thermal diffusivity of 0.5-1.5 W m-1 K-1), shows that radiative heating can heat carbonaceous meteoroids in the meter size range to core temperatures up to 1050 K, consistent with the metamorphic temperatures estimated for CK chondrites. Sizes of known CV and CK chondrites indicate that all these objects were small meteoroids (radii from a few cm to 2.5 m) prior to their atmospheric entry. Simulations of dynamic orbits for NEO objects suggest that there are numerous such bodies with suitable orbits and properties, even if they are only a small percentage of all NEOs. Radiative heating would be a secondary process (superimposed on parent-body processes) affecting meteoroids formed by the disruption of an initially homogeneous CV3-type parent body. Different petrologic types can be accounted for depending on the sizes and heliocentric distances of the objects in such a swarm.

  6. Residual Stress and Fatigue Strength of Hybrid Laser-MIG-Welded A7N01P-T4

    Science.gov (United States)

    Wang, Qiuying; Chen, Hui; Qiu, Peixian; Zhu, Zongtao

    2017-02-01

    A7N01P-T4 aluminum alloy is widely used in some important welded components of high-speed trains. The hybrid laser-metal inert gas (MIG) welding process was studied to solve problems associated with the MIG welding process, such as low welding efficiency, high residual stress and deformation, and serious loss of strength. A high-speed camera, a voltage and current collection system, and NI DAQ were used to acquire arc profiles, welding voltage, and welding current simultaneously. Thermal cycle tests were carried out. Residual stresses induced by the welding process and fatigue strength of the joint were investigated. Large-size fatigue specimens were used in fatigue tests. The results show that the energy of the hybrid welding process is focused, and the power density of hybrid welding process is intense. The heat input per unit of the hybrid welding process is only half of that of the MIG welding process. Compared with the MIG welded joint, the overall residual stress level of the hybrid-welded joint is lower. The peak longitudinal stress of the hybrid-welded joint is reduced by 20 pct. The fatigue strength of hybrid joints is 14 pct higher than that of MIG-welded joints. Narrow weld and HAZ, weak softening behavior, and low residual stress level are the causes of the improvement of fatigue strength.

  7. Creep-fatigue damage characteristics for a welded cylindrical structure of austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeo Yeon; Kim, Jong Bum; Kim, Seok Hoon; Joo, Young Sang; Lee, Jae Han [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2004-07-01

    In the design and assessment of a high temperature structure, it is important to ensure the structural integrity for the welded joint subjected to a creep-fatigue load because a statistical investigation shows that 29 events out of 46 leaks in liquid metal reactors were caused at the welded joints. As for the structural integrity due to thermal ratchet load at the welded joint, KAERI has performed the test and analysis work for a cylindrical structure with welded joints. As a continuation of the study on welded joints at a high temperature structure, a creep-fatigue structural test and analysis work is now on-going and this paper present the interim findings for the structural test and analysis work. Recently the structural and analysis work for the Y-piece made of a 316L stainless steel structure has been carried out. The objectives of the present structural creep-fatigue test with the welded cylindrical specimen are to compare the creep-fatigue damage mechanisms for the 304 and 316L stainless steels, to compare the different behavior of the welding methods in a high temperature austenitic structures and to quantify the conservatism of the design guidelines for a high temperature structure.

  8. Re-examination of the cause of the Paleocene-Eocene thermal maximum, based on global carbon-cycle modeling

    National Research Council Canada - National Science Library

    Yasukawa, Kazutaka; Nakamura, Kentaro; Kato, Yasuhiro

    2010-01-01

    .... To provide some constraints on the cause of the PETM, we re-examined the observed magnitude of the CIE, and then reconstructed the perturbation of the global carbon cycle during the PETM, using...

  9. Chronic fatigue syndrome: aetiology, diagnosis and treatment

    Science.gov (United States)

    Avellaneda Fernández, Alfredo; Pérez Martín, Álvaro; Izquierdo Martínez, Maravillas; Arruti Bustillo, Mar; Barbado Hernández, Francisco Javier; de la Cruz Labrado, Javier; Díaz-Delgado Peñas, Rafael; Gutiérrez Rivas, Eduardo; Palacín Delgado, Cecilia; Rivera Redondo, Javier; Ramón Giménez, José Ramón

    2009-01-01

    Chronic fatigue syndrome is characterised by intense fatigue, with duration of over six months and associated to other related symptoms. The latter include asthenia and easily induced tiredness that is not recovered after a night's sleep. The fatigue becomes so severe that it forces a 50% reduction in daily activities. Given its unknown aetiology, different hypotheses have been considered to explain the origin of the condition (from immunological disorders to the presence of post-traumatic oxidative stress), although there are no conclusive diagnostic tests. Diagnosis is established through the exclusion of other diseases causing fatigue. This syndrome is rare in childhood and adolescence, although the fatigue symptom per se is quite common in paediatric patients. Currently, no curative treatment exists for patients with chronic fatigue syndrome. The therapeutic approach to this syndrome requires a combination of different therapeutic modalities. The specific characteristics of the symptomatology of patients with chronic fatigue require a rapid adaptation of the educational, healthcare and social systems to prevent the problems derived from current systems. Such patients require multidisciplinary management due to the multiple and different issues affecting them. This document was realized by one of the Interdisciplinary Work Groups from the Institute for Rare Diseases, and its aim is to point out the main social and care needs for people affected with Chronic Fatigue Syndrome. For this, it includes not only the view of representatives for different scientific societies, but also the patient associations view, because they know the true history of their social and sanitary needs. In an interdisciplinary approach, this work also reviews the principal scientific, medical, socio-sanitary and psychological aspects of Chronic Fatigue Syndrome. PMID:19857242

  10. Chronic fatigue syndrome: aetiology, diagnosis and treatment

    Directory of Open Access Journals (Sweden)

    Palacín Delgado Cecilia

    2009-10-01

    Full Text Available Abstract Chronic fatigue syndrome is characterised by intense fatigue, with duration of over six months and associated to other related symptoms. The latter include asthenia and easily induced tiredness that is not recovered after a night's sleep. The fatigue becomes so severe that it forces a 50% reduction in daily activities. Given its unknown aetiology, different hypotheses have been considered to explain the origin of the condition (from immunological disorders to the presence of post-traumatic oxidative stress, although there are no conclusive diagnostic tests. Diagnosis is established through the exclusion of other diseases causing fatigue. This syndrome is rare in childhood and adolescence, although the fatigue symptom per se is quite common in paediatric patients. Currently, no curative treatment exists for patients with chronic fatigue syndrome. The therapeutic approach to this syndrome requires a combination of different therapeutic modalities. The specific characteristics of the symptomatology of patients with chronic fatigue require a rapid adaptation of the educational, healthcare and social systems to prevent the problems derived from current systems. Such patients require multidisciplinary management due to the multiple and different issues affecting them. This document was realized by one of the Interdisciplinary Work Groups from the Institute for Rare Diseases, and its aim is to point out the main social and care needs for people affected with Chronic Fatigue Syndrome. For this, it includes not only the view of representatives for different scientific societies, but also the patient associations view, because they know the true history of their social and sanitary needs. In an interdisciplinary approach, this work also reviews the principal scientific, medical, socio-sanitary and psychological aspects of Chronic Fatigue Syndrome.

  11. Chronic fatigue syndrome: aetiology, diagnosis and treatment.

    Science.gov (United States)

    Avellaneda Fernández, Alfredo; Pérez Martín, Alvaro; Izquierdo Martínez, Maravillas; Arruti Bustillo, Mar; Barbado Hernández, Francisco Javier; de la Cruz Labrado, Javier; Díaz-Delgado Peñas, Rafael; Gutiérrez Rivas, Eduardo; Palacín Delgado, Cecilia; Rivera Redondo, Javier; Ramón Giménez, José Ramón

    2009-10-23

    Chronic fatigue syndrome is characterised by intense fatigue, with duration of over six months and associated to other related symptoms. The latter include asthenia and easily induced tiredness that is not recovered after a night's sleep. The fatigue becomes so severe that it forces a 50% reduction in daily activities. Given its unknown aetiology, different hypotheses have been considered to explain the origin of the condition (from immunological disorders to the presence of post-traumatic oxidative stress), although there are no conclusive diagnostic tests. Diagnosis is established through the exclusion of other diseases causing fatigue. This syndrome is rare in childhood and adolescence, although the fatigue symptom per se is quite common in paediatric patients. Currently, no curative treatment exists for patients with chronic fatigue syndrome. The therapeutic approach to this syndrome requires a combination of different therapeutic modalities. The specific characteristics of the symptomatology of patients with chronic fatigue require a rapid adaptation of the educational, healthcare and social systems to prevent the problems derived from current systems. Such patients require multidisciplinary management due to the multiple and different issues affecting them. This document was realized by one of the Interdisciplinary Work Groups from the Institute for Rare Diseases, and its aim is to point out the main social and care needs for people affected with Chronic Fatigue Syndrome. For this, it includes not only the view of representatives for different scientific societies, but also the patient associations view, because they know the true history of their social and sanitary needs. In an interdisciplinary approach, this work also reviews the principal scientific, medical, socio-sanitary and psychological aspects of Chronic Fatigue Syndrome.

  12. Biomarkers of peripheral muscle fatigue during exercise

    Directory of Open Access Journals (Sweden)

    Finsterer Josef

    2012-11-01

    Full Text Available Abstract 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.

  13. Laser ultrasonic absorption measurement in fatigue-damaged materials.

    Science.gov (United States)

    Luxenburger, S; Arnold, W

    2002-05-01

    Changes in the materials microstructure caused by fatigue processes affect the ultrasonic absorption. Thus, quantitative measurement of the ultrasonic absorption should provide an indirect measure of fatigue damage. In this paper we present a study of the ultrasonic absorption in fatigue-damaged metals using the reverberation technique in combination with laser-based ultrasound. The reverberation technique allows one to measure absorption independently of scattering.

  14. Comparative Physiology of Fatigue

    National Research Council Canada - National Science Library

    JONES, JAMES H

    2016-01-01

    ABSTRACTThis review attempts to provide insights into factors associated with fatigue in human and nonhuman animals by using the two fundamental approaches of comparative physiologydetermining common...

  15. Neurobiological studies of fatigue

    Science.gov (United States)

    Harrington, Mary E.

    2012-01-01

    Fatigue is a symptom associated with many disorders, is especially common in women and in older adults, and can have a huge negative influence on quality of life. Although most past research on fatigue uses human subjects instead of animal models, the use of appropriate animal models has recently begun to advance our understanding of the neurobiology of fatigue. In this review, results from animal models using immunological, developmental, or physical approaches to study fatigue are described and compared. Common across these animal models is that fatigue arises when a stimulus induces activation of microglia and/or increased cytokines and chemokines in the brain. Neurobiological studies implicate structures in the ascending arousal system, sleep executive control areas, and areas important in reward. In addition, the suprachiasmatic nucleus clearly plays an important role in homeostatic regulation of the neural network mediating fatigue. This nucleus responds to cytokines, shows decreased amplitude firing rate output in models of fatigue, and responds to exercise, one of our few treatments for fatigue. This is a young field but very important as the symptom of fatigue is common across many disorders and we do not have effective treatments. PMID:22841649

  16. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...

  17. Muscle glycogen stores and fatigue

    DEFF Research Database (Denmark)

    Ørtenblad, Niels; Westerblad, Håkan; Nielsen, Joachim

    2013-01-01

    function during fatigue is not well understood and a direct cause-and-effect relationship between glycogen and muscle function remains to be established. The use of electron microscopy has revealed that glycogen is not homogeneously distributed in skeletal muscle fibres, but rather localized in distinct......  Studies performed at the beginning of the last century revealed the importance of carbohydrate as a fuel during exercise, and the importance of muscle glycogen on performance has subsequently been confirmed in numerous studies. However, the link between glycogen depletion and impaired muscle...... the sarcoplasmic reticulum (SR). We and others have provided experimental evidence in favour of a direct role of decreased glycogen, localized within the myofibrils, for the reduction in SR Ca2+ release during fatigue. This is consistent with compartmentalized energy turnover and distinctly localized glycogen...

  18. Improvement on the Fatigue Performance of 2024-T4 Alloy by Synergistic Coating Technology.

    Science.gov (United States)

    Wang, Xi-Shu; Guo, Xing-Wu; Li, Xu-Dong; Ge, Dong-Yun

    2014-05-06

    In this paper, rotating bending fatigue tests of 2024-T4 Al alloy with different oxide coatings were carried out. Compared to the uncoated and previously reported oxide coatings of aluminum alloys, the fatigue strength is able to be enhanced by using a novel oxide coating with sealing pore technology. These results indicate that the better the coating surface quality is, the more excellent the fatigue performance under rotating bending fatigue loading is. The improvement on the fatigue performance is mainly because the fatigue crack initiation and the early stage of fatigue crack growth at the coating layer can be delayed after PEO coating with pore sealing. Therefore, it is a so-called synergistic coating technology for various uses, including welding thermal cracks and filling micro-pores. The effects of different oxide coatings on surface hardness, compressive residual stress, morphology and fatigue fracture morphology are discussed. A critical compressive residual stress of about 95-100 MPa is proposed.

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

    Science.gov (United States)

    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.

  20. A Green's function approach for assessing the thermal disturbance caused by drilling deep boreholes in rock or ice

    Science.gov (United States)

    Clow, Gary D.

    2015-01-01

    A knowledge of subsurface temperatures in sedimentary basins, fault zones, volcanic environments and polar ice sheets is of interest for a wide variety of geophysical applications. However, the process of drilling deep boreholes in these environments to provide access for temperature and other measurements invariably disturbs the temperature field around a newly created borehole. Although this disturbance dissipates over time, most temperature measurements are made while the temperature field is still disturbed. Thus, the measurements must be ‘corrected’ for the drilling-disturbance effect if the undisturbed temperature field is to be determined. This paper provides compact analytical solutions for the thermal drilling disturbance based on 1-D (radial) and 2-D (radial and depth) Green's functions (GFs) in cylindrical coordinates. Solutions are developed for three types of boundary conditions (BCs) at the borehole wall: (1) prescribed temperature, (2) prescribed heat flux and (3) a prescribed convective condition. The BC at the borehole wall is allowed to vary both with depth and time. Inclusion of the depth dimension in the 2-D solution allows vertical heat-transfer effects to be quantified in situations where they are potentially important, that is, near the earth's surface, at the bottom of a well and when considering finite-drilling rates. The 2-D solution also includes a radial- and time-dependent BC at the earth's surface to assess the impact of drilling-related infrastructure (drilling pads, mud pits, permanent shelters) on the subsurface temperature field. Latent-heat effects due to the melting and subsequent refreezing of interstitial ice while drilling a borehole through ice-rich permafrost can be included in the GF solution as a moving-plane heat source (or sink) located at the solid–liquid interface. Synthetic examples are provided illustrating the 1-D and 2-D GF solutions. The flexibility of the approach allows the investigation of thermal

  1. Computing Thermal Performances Of Shafts And Bearings

    Science.gov (United States)

    Woods, Claudia M.

    1992-01-01

    SHABERTH computer program developed to predict steady-state and transient thermal performance of multi-bearing shaft system operating with either wet or dry friction. Calculates loads, torques, temperatures, and fatigue lives for ball and/or roller bearings on single shaft. Enables study of many causes of instabilities in bearings. Also provides for analysis of reaction of system to termination of supply of lubricant to bearings and other lubricated mechanical elements. Valuable software tool in design and analysis of shaft bearing systems. Written in FORTRAN IV.

  2. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Pu...

  3. Thermal and sedimentation stress are unlikely causes of brown spot syndrome in the coral reef sponge, Ianthella basta.

    Directory of Open Access Journals (Sweden)

    Heidi M Luter

    Full Text Available BACKGROUND: Marine diseases are being increasingly linked to anthropogenic factors including global and local stressors. On the Great Barrier Reef, up to 66% of the Ianthella basta population was recently found to be afflicted by a syndrome characterized by brown spot lesions and necrotic tissue. METHODOLOGY/PRINCIPAL FINDINGS: Manipulative experiments were undertaken to ascertain the role of environmental stressors in this syndrome. Specifically, the effects of elevated temperature and sedimentation on sponge health and symbiont stability in I. basta were examined. Neither elevated temperature nor increased sedimentation were responsible for the brown spot lesions, but sponges exposed to 32°C developed substantial discoloration and deterioration of their tissues, resulting in death after eight days and a higher microbial diversity in those samples. No shifts in the microbial community of I. basta were observed across a latitudinal gradient or with increased sedimentation, with three previously described symbionts dominating the community of all sponges (Alphaproteobacteria, Gammaproteobacteria and Thaumarchaea. CONCLUSIONS/SIGNIFICANCE: Results from this study highlight the stable microbial community of I. basta and indicate that thermal and sedimentation stress are not responsible for the brown spot lesions currently affecting this abundant and ecologically important sponge species.

  4. Selected issues concerning calculations and experimental tests of transport means construction elements fatigue life

    Directory of Open Access Journals (Sweden)

    Bogdan LIGAJ

    2014-12-01

    Full Text Available Development of an algorithm of fatigue life of structural components of road and rail vehicles as well as sea vessels and aircrafts involves three groups of activities connected with: development of fatigue load spectra on the basis measurement of service loads, determination of the construction material fatigue properties and a selection of the best hypothesis for estimating the fatigue damage to be used for a phenomenological description of the fatigue process. The above listed groups of problems include the main causes of differences that occur between the calculation results and the results of fatigue life experimental tests. Evaluation of these differences is the main goal of this article.

  5. Optimal Inspection Planning for Fatigue Damage of Offshore Structures

    DEFF Research Database (Denmark)

    Madsen, H.O.; Sørensen, John Dalsgaard; Olesen, R.

    1990-01-01

    A formulation of optimal design, inspection and maintenance against damage caused by fatigue crack growth is formulated. A stochastic model for fatigue crack growth based on linear elastic fracture mechanics Is applied. Failure is defined by crack growth beyond a critical crack size. The failure......, inspection, repair and failure is minimized with a constraint on the life time reliability....

  6. Depression, Fatigue, and Pre-Sleep Arousal: A Mediation Model

    Science.gov (United States)

    Karlson, Cynthia W.; Stevens, Natalie R.; Olson, Christy A.; Hamilton, Nancy A.

    2010-01-01

    Fatigue is a common and debilitating symptom of clinical depression; however, the causes are not well understood. The present study was designed to test the hypotheses that subjective sleep, objective sleep, and arousal in the pre-sleep state would mediate the relationship between depression status and fatigue. Sleep, pre-sleep arousal, and…

  7. Probabilistic Fatigue Model for Reinforced Concrete Onshore Wind Turbine Foundations

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2013-01-01

    Reinforced Concrete Slab Foundation (RCSF) is the most common onshore wind turbine foundation type installed by the wind industry around the world. Fatigue cracks in a RCSF are an important issue to be considered by the designers. Causes and consequences of the cracks due to fatigue damage in RCSFs...

  8. Examining fatigue in COPD

    DEFF Research Database (Denmark)

    Al-Shair, Khaled; Muellerova, Hana; Yorke, Janelle

    2012-01-01

    ABSTRACT: INTRODUCTION: Fatigue is a disruptive symptom that inhibits normal functional performance of COPD patients in daily activities. The availability of a short, simple, reliable and valid scale would improve assessment of the characteristics and influence of fatigue in COPD. METHODS......: At baseline, 2107 COPD patients from the ECLIPSE cohort completed the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) scale. We used well-structured classic method, the principal components analysis (PCA) and Rasch analysis for structurally examining the 13-item FACIT-F. RESULTS: Four items...... were less able to capture fatigue characteristics in COPD and were deleted. PCA was applied to the remaining 9 items of the modified FACIT-F and resulted in three interpretable dimensions: i) general (5 items); ii) functional ability (2 items); and iii) psychosocial fatigue (2 items). The modified...

  9. Fatigue Symptom Management in People Living With Human Immunodeficiency Virus.

    Science.gov (United States)

    Perazzo, Joseph D; Webel, Allison R; Voss, Joachim G; Prince-Paul, Maryjo

    2017-04-01

    Fatigue is a subjective, unpleasant, potentially disabling symptom rooted in physiological, psychological, and behavioral causes. People living with HIV are a population highly affected by fatigue due to risk factors associated with HIV-infection, treatment, and psychosocial disease burden. People with HIV are living longer, and are facing the challenge of a longer disease trajectory. Palliative nurses with expertise in symptom management can play a crucial role in helping people with HIV to engage in health behaviors that prevent or mitigate fatigue. In this paper we present a definition and overview of fatigue, describe the problem of fatigue in people living with HIV, and present a case study that illustrates the role of the palliative nurse in helping a person with HIV to cope with fatigue.

  10. Fatigue analysis of the pressurizer surge line nozzle in KKP2; Ermuedungsanalyse des Druckhalterstutzens der VAL in KKP2

    Energy Technology Data Exchange (ETDEWEB)

    Heyder, Michael [KAE GmbH, Hausen (Germany); Tulke, Klaus-Dieter [EnBW Kraftwerke AG, Philippsburg (Germany). Kernkraftwerk Philippsburg

    2008-07-01

    Materials fatigue is an important safety relevant topic for mechanical and thermal cycling behavior of reactor components and thus a substantial part of serious aging management. Operational stability and endurance strength of the components and failure preclusion can only be demonstrated by fatigue analyses. The authors describe the fundamentals of fatigue processes, the method for elastic-plastic fatigue analysis according KTA 3201.2 and exercise the fatigue analysis for the pressurizer surge line nozzle for the NPP KKP2. The results are compared with other fatigue analysis techniques according KTA 3201.2 and FAMOS-3.

  11. Chronic fatigue syndrome: identifying zebras amongst the horses

    Directory of Open Access Journals (Sweden)

    Wessely Simon

    2009-10-01

    Full Text Available Abstract There are currently no investigative tools or physical signs that can confirm or refute the presence of chronic fatigue syndrome (CFS. As a result, clinicians must decide how long to keep looking for alternative explanations for fatigue before settling on a diagnosis of CFS. Too little investigation risks serious or easily treatable causes of fatigue being overlooked, whilst too many increases the risk of iatrogenic harm and reduces the opportunity for early focused treatment. A paper by Jones et al published this month in BMC Medicine may help clinicians in deciding how to undertake such investigations. Their results suggest that if clinicians look for common psychiatric and medical conditions in those complaining of prolonged fatigue, the rate of detection will be higher than previously estimated. The most common co-morbid condition identified was depression, suggesting a simple mental state examination remains the most productive single investigation in any new person presenting with unexplained fatigue. Currently, most diagnostic criteria advice CFS should not be diagnosed when an active medical or psychiatric condition which may explain the fatigue is identified. We discuss a number of recent prospective studies that have provided valuable insights into the aetiology of chronic fatigue and describe a model for understanding chronic fatigue which may be equally relevant regardless of whether or not an apparent medical cause for fatigue can be identified. See the associated research paper by Jones et al: http://www.biomedcentral.com/1741-7015/7/57

  12. Effects of Pulse Current on Endurance Exercise and Its Anti-Fatigue Properties in the Hepatic Tissue of Trained Rats

    OpenAIRE

    Qi Chang; Xinfang Miao; Xiaowei Ju; Lvgang Zhu; Changlin Huang; Tao Huang; Xincheng Zuo; Chunfang Gao

    2013-01-01

    Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or en...

  13. Fatigue Management in Spaceflight Operations

    Science.gov (United States)

    Whitmire, Alexandra

    2011-01-01

    Sleep loss and fatigue remain an issue for crewmembers working on the International Space Station, and the ground crews who support them. Schedule shifts on the ISS are required for conducting mission operations. These shifts lead to tasks being performed during the biological night, and sleep scheduled during the biological day, for flight crews and the ground teams who support them. Other stressors have been recognized as hindering sleep in space; these include workload, thinking about upcoming tasks, environmental factors, and inadequate day/night cues. It is unknown if and how other factors such as microgravity, carbon dioxide levels, or increased radiation, may also play a part. Efforts are underway to standardize and provide care for crewmembers, ground controllers and other support personnel. Through collaborations between research and operations, evidenced-based clinical practice guidelines are being developed to equip flight surgeons with the tools and processes needed for treating circadian desynchrony (and subsequent sleep loss) caused by jet lag and shift work. The proper implementation of countermeasures such as schedules, lighting protocols, and cognitive behavioral education can hasten phase shifting, enhance sleep and optimize performance. This panel will focus on Fatigue Management in Spaceflight Operations. Speakers will present on research-based recommendations and technologies aimed at mitigating sleep loss, circadian desynchronization and fatigue on-orbit. Gaps in current mitigations and future recommendations will also be discussed.

  14. Causes of Early-Age Thermal Cracking of Concrete Foundation Slabs and their Reinforcement to Control the Cracking

    Science.gov (United States)

    Bilčík, Juraj; Sonnenschein, Róbert; Gažovičová, Natália

    2017-09-01

    This paper focuses on the causes and consequences of early-age cracking of mass concrete foundation slabs due to restrained volume changes. Considering the importance of water leaking through cracks in terms of the serviceability, durability and environmental impact of watertight concrete structures, emphasis is placed on the effect of temperature loads on foundation slabs. Foundation slabs are usually restrained to some degree externally or internally. To evaluate the effect of external restraints on foundation slabs, friction and interaction models are introduced. The reinforcement of concrete cannot prevent the initiation of cracking, but when cracking has occurred, it may act to reduce the spacing and width of cracks. According to EN 1992-1-1, results of calculating crack widths with local variations included in National Annexes (NAs) vary considerably. A comparison of the required reinforcement areas according to different NAs is presented.

  15. Causes of Early-Age Thermal Cracking of Concrete Foundation Slabs and their Reinforcement to Control the Cracking

    Directory of Open Access Journals (Sweden)

    Bilčík Juraj

    2017-09-01

    Full Text Available This paper focuses on the causes and consequences of early-age cracking of mass concrete foundation slabs due to restrained volume changes. Considering the importance of water leaking through cracks in terms of the serviceability, durability and environmental impact of watertight concrete structures, emphasis is placed on the effect of temperature loads on foundation slabs. Foundation slabs are usually restrained to some degree externally or internally. To evaluate the effect of external restraints on foundation slabs, friction and interaction models are introduced. The reinforcement of concrete cannot prevent the initiation of cracking, but when cracking has occurred, it may act to reduce the spacing and width of cracks. According to EN 1992-1-1, results of calculating crack widths with local variations included in National Annexes (NAs vary considerably. A comparison of the required reinforcement areas according to different NAs is presented.

  16. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

    Akkerman, Moniek; Mouton, Leonora J.; Dijkstra, Froukje; Niemeijer, Anuschka S.; van Brussel, Marco; van der Woude, Lucas H. V.; Disseldorp, Laurien M.; Nieuwenhuis, Marianne K.

    2017-01-01

    Purpose: Fatigue is a common consequence of numerous pediatric health conditions. In adult burn survivors, fatigue was found to be a major problem. The current cross-sectional study is aimed at determining the levels of perceived fatigue in pediatric burn survivors. Methods: Perceived fatigue was

  17. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

    Akkerman, Moniek; Mouton, Leonora J.; Dijkstra, Froukje; Niemeijer, Anuschka S.; van Brussel, Marco|info:eu-repo/dai/nl/30481962X; Van der Woude, Lucas H. V.; Disseldorp, Laurien M.; Nieuwenhuis, Marianne K.

    2017-01-01

    Purpose Fatigue is a common consequence of numerous pediatric health conditions. In adult burn survivors, fatigue was found to be a major problem. The current cross-sectional study is aimed at determining the levels of perceived fatigue in pediatric burn survivors. Methods Perceived fatigue was

  18. Prolonged unexplained fatigue in paediatrics

    NARCIS (Netherlands)

    Bakker, R.J.

    2010-01-01

    Prolonged Unexplained Fatigue in Paediatrics. Fatigue, as the result of mental or physical exertion, will disappear after rest, drinks and food. Fatigue as a symptom of illness will recover with the recovering of the illness. But when fatigue is ongoing for a long time, and not the result of

  19. Experiences of Fatigue at Sea

    DEFF Research Database (Denmark)

    Zhao, Zhiwei; Jepsen, Jørgen Riis; Chen, Zhonglong

    2016-01-01

    Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T...

  20. The urban heat island effect, its causes, and mitigation, with reference to the thermal properties of asphalt concrete.

    Science.gov (United States)

    Mohajerani, Abbas; Bakaric, Jason; Jeffrey-Bailey, Tristan

    2017-07-15

    The Urban Heat Island (UHI) is a phenomenon that affects many millions of people worldwide. The higher temperatures experienced in urban areas compared to the surrounding countryside has enormous consequences for the health and wellbeing of people living in cities. The increased use of manmade materials and increased anthropogenic heat production are the main causes of the UHI. This has led to the understanding that increased urbanisation is the primary cause of the urban heat island. The UHI effect also leads to increased energy needs that further contribute to the heating of our urban landscape, and the associated environmental and public health consequences. Pavements and roofs dominate the urban surface exposed to solar irradiation. This review article outlines the contribution that pavements make to the UHI effect and analyses localized and citywide mitigation strategies against the UHI. Asphalt Concrete (AC) is one of the most common pavement surfacing materials and is a significant contributor to the UHI. Densely graded AC has low albedo and high volumetric heat capacity, which results in surface temperatures reaching upwards of 60 °C on hot summer days. Cooling the surface of a pavement by utilizing cool pavements has been a consistent theme in recent literature. Cool pavements can be reflective or evaporative. However, the urban geometry and local atmospheric conditions should dictate whether or not these mitigation strategies should be used. Otherwise both of these pavements can actually increase the UHI effect. Increasing the prevalence of green spaces through the installation of street trees, city parks and rooftop gardens has consistently demonstrated a reduction in the UHI effect. Green spaces also increase the cooling effect derived from water and wind sources. This literature review demonstrates that UHI mitigation techniques are best used in combination with each other. As a result of the study, it was concluded that the current mitigation

  1. Fatigue in breast cancer patients on adjuvant treatment: Course and prevalence

    Directory of Open Access Journals (Sweden)

    Kazi S Manir

    2012-01-01

    Full Text Available Introduction: Fatigue is a major complain in breast cancer patients and survivors. Patterns and degree varies with schedule and type of the treatment. Different co-factors may aggravate fatigue. Multimodal approach is helpful in managing fatigue. Aim: To quantify prevalence, course and degree of fatigue in breast cancer patients on adjuvant treatment and effectiveness of different management approach. Materials and Methods: One Hundred and ten post-mastectomy breast cancer patients (Stage I to Stage III were assessed. Patients on chemotherapy were assessed one week before, day after chemotherapy and two weeks later in every cycle. Patients on External Beam Radiation Therapy (EBRT were assessed one week before and every week during radiation. Assessment was continued on second and fourth week of follow up. Functional Assessment of Chronic Illness Therapy - Fatigue subscale (FACIT-F was used for assessment. Significant cofactors were also searched for. Results: Eighty four percent patients experienced fatigue. Fatigue was more prevalent during chemotherapy (91% than EBRT (77%. Patients on Chemotherapy exhibit peak fatigue day after Chemotherapy and decreased level until the next cycle. Significant increase of fatigue was seen only in first cycle. Patient on EBRT had gradually increased fatigue during the course of treatment. Lower degree of fatigue was present in post treatment period. Anemia was a significant cofactor causing fatigue (P < 0.05. Blood Transfusion improved fatigue scores. Conclusion: Fatigue increases during chemotherapy and or EBRT. Different intervention strategies are needed to address the issue.

  2. Effect of Grain Size on Ultrasonic Fatigue Properties of Ni-Base Super Alloy Inconel 718

    OpenAIRE

    皮籠石, 紀雄; 前村, 英史; 陳, 強; 後藤, 真宏; 森野, 数博

    2008-01-01

    Ultrasonic fatigue tests of plain specimens with different grain sizes were carried out for Ni-base super alloy, Inconel 718, in ambient air in order to investigate the effect of grain size on fatigue properties. Fatigue strength was increased with decrease in grain size. The increase in fatigue strength by refining grain size was mainly caused by the suppression of crack initiation. That is, the effect of grain size on crack growth rate was hardly recognized, though crack morphology was roug...

  3. Fatigue 󈨛. Volume 2,

    Science.gov (United States)

    1987-06-01

    boundary. 638 FATIGUE 87 The bulk bismuth concentrations of the bicrystals were measured by Chicago Spectro Laboratory and Charles C. Kawin Company both...645. B.M. Strauss and W.H. Cullen , Jr., editors, ASTM, Philadelphia, 1978, pp. 164-175. (4) Meakin. J.D. and Wilsdorf, H.G.F.. Trans. TMS-AIME, Vol... Edmunds , 1986. 785 FATIGUE 87 (7) James, M.N. and Knott, J.F., Fatigue Fract. Engng Mater. Struct., Vol.8, 1985, pp.177-191. (8) Breat, J.L., Mudry, F

  4. Fatigue life prediction under service load considering strengthening effect of loads below fatigue limit

    Science.gov (United States)

    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.

  5. Fluid-Structure Interaction Analysis for Pressurizer Surge Line subjected to Thermal Stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong Gu; Jhung, Myung Jo; Yang, Chae Yong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2012-05-15

    Fluid-Structure Interactions (FSIs) occurring inevitably in operating reactor component systems can cause excessive force or stress to the structures resulting in mechanical damages that may eventually threaten the structural integrity of components. To solve FSI problems, results from one field (fluid-thermal) analysis are applied as loads in other fields (structural) analysis. If two media with different densities flow inside a pipe, thermal stratification can occur. Warm water is lighter than cool water and therefore tends to float on top of the cooler and heavier water, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, differential thermal expansion of the pipe metal can cause the pipe to deflect significantly. Unexpected piping movements are highly undesirable because of potential high piping stress that may exceed design limits for fatigue and stress. In PWRs, there are great possibilities of occurrence of thermal stratification at the feed water lines of the steam generator, at the pressurizer surge line and at the injection pipes of the emergency core cooling systems. The most affected pipe by the thermal stratification is reported to be the pressurizer surge line. Therefore in this study, a thermal-stress simulation is performed using ANSYS FSI. For the pressurizer surge line, thermal loads are transferred from ANSYS CFX to ANSYS Multiphysics in order to determine the heat transfer between the fluid and the solid body. From this information, stresses are determined and ultimately a fatigue analysis is performed

  6. Contact fatigue in rolling-element bearings

    CSIR Research Space (South Africa)

    Fernandes, PJL

    1997-06-01

    Full Text Available Surface contact fatigue is a common cause of failure in rolling-element bearings. The extent of damage observed depends on the contact loads, the curvature of the rolling elements, and the relative motion between the contacting surfaces...

  7. Fatigue crack growth in Aluminium Alloys

    NARCIS (Netherlands)

    Van Kranenburg, C.

    2010-01-01

    Fatigue is a gradual process of local strength reduction. It is a phenomenon of damage accumulation at stress concentrations caused by fluctuating stresses and/or strains. In metals this results in microscopic cracks. These will start to grow under continued cyclic loading until final failure

  8. Sonic Fatigue Design Guide for Military Aircraft

    Science.gov (United States)

    1975-05-01

    Center Stress x tor supported Edoes 0.50 ---- 04 9 SPanpl I q , Stress 0.40 , for Clarmped Edqes .2 E 0.30030-8 I I I -. J for Supported Edqc E0 06...for us, on the NASA Space Shuttle Orbiter . The latter program has recently caused a renewed interest in the sonic fatigue design cri- teria for

  9. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Symptoms

    Science.gov (United States)

    ... Controls Search Form Controls Cancel Submit Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Note: Javascript is disabled or is not supported ... message, please visit this page: About CDC.gov . ME/CFS What is ME/CFS Possible Causes Symptoms and ...

  10. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Diagnosis

    Science.gov (United States)

    ... Controls Search Form Controls Cancel Submit Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Note: Javascript is disabled or is not supported ... message, please visit this page: About CDC.gov . ME/CFS What is ME/CFS Possible Causes Symptoms and ...

  11. Chronic fatigue in Ehlers-Danlos syndrome-Hypermobile type.

    Science.gov (United States)

    Hakim, Alan; De Wandele, Inge; O'Callaghan, Chris; Pocinki, Alan; Rowe, Peter

    2017-03-01

    Chronic fatigue is an important contributor to impaired health-related quality of life in Ehlers-Danlos syndrome. There is overlap in the symptoms and findings of EDS and chronic fatigue syndrome. A proportion of those with CFS likely have EDS that has not been identified. The evaluation of chronic fatigue in EDS needs to include a careful clinical examination and laboratory testing to exclude common causes of fatigue including anemia, hypothyroidisim, and chronic infection, as well as dysfunction of major physiological or organ systems. Other problems that commonly contribute to fatigue in EDS include sleep disorders, chronic pain, deconditioning, cardiovascular autonomic dysfunction, bowel and bladder dysfunction, psychological issues, and nutritional deficiencies. While there is no specific pharmacological treatment for fatigue, many medications are effective for specific symptoms (such as headache, menstrual dysfunction, or myalgia) and for co-morbid conditions that result in fatigue, including orthostatic intolerance and insomnia. Comprehensive treatment of fatigue needs to also evaluate for biomechanical problems that are common in EDS, and usually involves skilled physical therapy and attention to methods to prevent deconditioning. In addition to managing specific symptoms, treatment of fatigue in EDS also needs to focus on maintaining function and providing social, physical, and nutritional support, as well as providing on-going medical evaluation of new problems and review of new evidence about proposed treatments. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. Mental fatigue detection based on the functional near infrared spectroscopy

    Science.gov (United States)

    Zhang, Zhen; Xu, Fenggang; Yang, Hanjun; Jiang, Jin; Cao, Yong; Jiao, Xuejun

    2017-02-01

    Mental fatigue can be induced by long time mental work, mental fatigue caused worse performance and accidents. As a non-invasive technique, functional near-infrared spectroscopy (fNIRS) can measure blood oxygen activity in the cerebral cortex which reflect the cognitive function of brain indirectly. Aiming at investigating whether fNIRS can measure the mental fatigue and study the spatial pattern of hemodynamic response for mental fatigue, we used three sessions of verbal 2-back working memory task for a total of 120 minutes to induce mental fatigue, 15 healthy subjects were recruited and 30 channels including prefrontal cortex (PFC) and motor cortex (MC) were measured by fNIRS. The mean oxyhemoglobin feature for 20s was extracted as well as subjective fatigue level and performance. The results showed significant increase of subjected fatigue level as well as significant decrease performance from session one to three task. With the increased level of fatigue, oxyhemoglobin in PFC increase significantly and the spatial pattern of hemodynamic response in the all 30 channels varied with task duration as well. These findings indicated the potential of fNIRS measured hemodynamic as a mental fatigue indicator.

  13. Chronic Fatigue Syndrome

    Science.gov (United States)

    ... light, eye pain) Psychological symptoms (irritability, mood swings, panic attacks, anxiety) Chills and night sweats Low grade ... Research Phone Number: 775-682-8250 Chronic fatigue syndrome > A-Z Health Topics The Office on Women's ...

  14. Hyperthermia and fatigue

    DEFF Research Database (Denmark)

    Nybo, Lars

    2008-01-01

    of the cardiovascular function, which eventually reduces arterial oxygen delivery to the exercising muscles. Accordingly, aerobic energy turnover is impaired and anaerobic metabolism provokes peripheral fatigue. In contrast, metabolic disturbances of muscle homeostasis are less important during prolonged exercise......The present review addresses mechanisms of importance for hyperthermia-induced fatigue during short intense activities and prolonged exercise in the heat. Inferior performance during physical activities with intensities that elicit maximal oxygen uptake is to a large extent related to perturbation...... in the heat, because increased oxygen extraction compensates for the reduction in systemic blood flow. The decrease in endurance seems to involve changes in the function of the central nervous system (CNS) that lead to fatigue. The CNS fatigue appears to be influenced by neurotransmitter activity...

  15. Chronic Fatigue Syndrome

    Science.gov (United States)

    ... people with CFS should avoid heavy meals, alcohol, caffeine, and large quantities of junk food. Some people ... to address problems. Write it down. If your memory and concentration are affected by chronic fatigue, it ...

  16. The Recognition Of Fatigue

    DEFF Research Database (Denmark)

    Elsass, Peter; Jensen, Bodil; Mørup, Rikke

    2007-01-01

    Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87......Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87...

  17. Fatigue mechanisms during physical exercise

    Directory of Open Access Journals (Sweden)

    Monique Gevaerd

    2006-03-01

    Full Text Available Fatigue can be defined as incapacity to maintain the required power output, with concomitant impairment of exercise performance, and it can be divided into chronic or acute. In acute fatigue a subdivision has been used to delimitate experimental studies. Thus, acute fatigue can be central or peripheral. We began the review process with a search on the Pubmed database, followed by selection of classical and more recent articles. As the fatigue mechanisms are linked to the predominant energy metabolism in the activity, the purpose of this paper was to review the main acute fatigue theories in activities with different metabolic demands. From this literature review, it was possible to infer that important metabolic alterations occurring during exercise, impair normal cellular activities,therefore, decreasing the speed of contraction and as well as energy replenishment. Many of those alterations give information to the central nervous system, limiting the time length of exercise. Theoretically, the elongation of exercise beyond biological limits can cause irreversible damages to the organism. RESUMO Fadiga pode ser definida como uma incapacidade na manutenção de uma determinada potência, com conseqüente redução no desempenho, podendo ser considerada como crônica ou aguda. Na fadiga aguda, uma subdivisão vem sendo utilizada para maior delimitação dos estudos experimentais. Nesse sentido, fadiga aguda pode ser descrita como central ou periférica. Nós iniciamos o processo de revisão sobre o assunto com uma busca no banco de dados Pubmed, seguido da seleção dos artigos clássicos e mais recentes. Como os mecanismos de fadiga estão intimamente ligados ao metabolismo energético predominante da atividade, a presente revisão destinou-se a levantar as principais teorias sobre fadiga aguda em atividades com diferentes exigências metabólicas. A partir desse apanhado bibliográfico podemos inferir que importantes alterações metab

  18. [Chronic fatigue syndrome: biochemical examination of blood].

    Science.gov (United States)

    Hakariya, Yukiko; Kuratsune, Hirohiko

    2007-06-01

    Though patients with chronic fatigue syndrome (CFS) have lots of complaints, abnormal findings cannot be detected by biochemical screening tests. However, some specialized blood tests have revealed neuroendocrine immune axis abnormalities, which is closely associated with each other. Recent studies indicate that CFS can be understood as a special condition based on abnormality of the psycho-neuro-endocrino-immunological system, with the distinguishing feature of CFS seeming to be the secondary brain dysfunction caused by several cytokines and/or autoantibodies. In this paper, we summarize these abnormalities found in CFS and show the neuro-molecular mechanism leading to chronic fatigue.

  19. [Chronic fatigue syndrome in cancer patients. Diagnostic and treatment options].

    Science.gov (United States)

    Jedlicka, F; Elbl, L; Vásová, I; Tomásková, I; Vorlícek, J; Spinar, J

    2007-09-01

    Fatigue is the most frequent symptom accompanying a cancer disease and its treatment according to the visual analogue scale. Fatigue is reported by as many as 100% of patients in the course of cancer treatment and still by 40 to 70% of patients one year after the treatment has finished. This symptom has become known under the designation of "cancer-related fatigue" in the English language literature on the subject. The knowledge of the causes and mechanisms of fatigue is relatively limited. Based on practical guidelines, an algorithm has been used to detect, evaluate and influence by treatment the syndrome of fatigue caused by a cancer disease. Research in the field has been focused on both pharmacological and non-pharmacological approach. The highest efficiency in the treatment of fatigue syndrome has been recorded for the treatment of anaemia with erythropoietin, while aerobic exercise programmes have proven to be most efficient among the behavioural measures. In spite of a dramatically growing interest in the above problem in the past decade, a number of issues continue unresolved with respect to chronic fatigue syndrome related to a cancer disease or to its treatment. Based on their own experience and on the relevant literature, the authors deal with issues of chronic fatigue syndrome and the options for its diagnosing and treatment in patients undergoing cancer treatment.

  20. Biomarkers of Fatigue: Ranking Mental Fatigue Susceptibility

    Science.gov (United States)

    2010-12-10

    Effectiveness ( SAFTE ), described in Hursh et al. 2004) holds that performance declines steeply after midnight until mid-morning where it levels off to...Meals occurred during the daylight portion of the protocol with greater frequency than the night time portion; however, participants were allowed...Vigilance Task) SAFTE (Sleep Activity Fatigue Task Effectiveness) SD (standard deviation) T (training) 28 Distribution A: Approved for

  1. Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainless Steel

    Science.gov (United States)

    Chen, Xingyang; Zhou, Chengshuang; Cai, Xiao; Zheng, Jinyang; Zhang, Lin

    2017-10-01

    The effects of external hydrogen on hydrogen transportation and distribution around the fatigue crack tip in type 304 stainless steel were investigated by using hydrogen microprint technique (HMT) and thermal desorption spectrometry. HMT results show that some silver particles induced by hydrogen release are located near the fatigue crack and more silver particles are concentrated around the crack tip, which indicates that hydrogen accumulates in the vicinity of the crack tip during the crack growth in hydrogen gas environment. Along with the crack propagation, strain-induced α' martensite forms around the crack tip and promotes hydrogen invasion into the matrix, which will cause the crack initiation and propagation at the austenite/ α' martensite interface. In addition, the hydrogen content in the vicinity of the crack tip is higher than that at the crack edge far away from the crack tip, which is related to the stress state and strain-induced α' martensite.

  2. Thermal cycling tests of actively cooled beryllium copper joints

    Energy Technology Data Exchange (ETDEWEB)

    Roedig, M.; Duwe, R.; Linke, J.; Schuster, A.; Wiechers, B. [Forschungszentrum Juelich GmbH (Germany)

    1998-01-01

    Screening tests (steady state heating) and thermal fatigue tests with several kinds of beryllium-copper joints have been performed in an electron beam facility. Joining techniques under investigation were brazing with silver containing and silver-free braze materials, hot isostatic pressing (HIP) and diffusion bonding (hot pressing). Best thermal fatigue performance was found for the brazed samples. (author)

  3. Fatigue mechanisms in unidirectional glass-fibre-reinforced polypropylene

    DEFF Research Database (Denmark)

    Gamstedt, E.K.; Berglund, L.A.; Peijs, T.

    1999-01-01

    Polypropylene (PP) and polypropylene modified with maleic anhydride (MA-PP) reinforced by continuous longitudinal glass fibres have been investigated. The most prominent effect of the modification with maleic anhydride in the composite is a stronger fibre/matrix interface. The effects...... of interfacial strength on fatigue performance and on the underlying micromechanisms have been studied for these composite systems. Tension-tension fatigue tests (R = 0.1) were carried out on 0 degrees glass-fibre/PP and glass-fibre/ MA-PP coupons. The macroscopic fatigue behaviour was characterized in terms...... of stiffness reduction and fatigue-life curves. The results showed that the longitudinal Young's modulus degraded more rapidly for glass-fibre/PP, which was caused by a higher degree of damage growth and accumulation. The improvement in monotonic strength was negligible, but the fatigue life was prolonged...

  4. Multiple sclerosis-related fatigue and possibilities of its correction

    Directory of Open Access Journals (Sweden)

    N. Yu. Lashch

    2016-01-01

    Full Text Available Multiple sclerosis (MS-related fatigue is encountered in 75–92% of patients and it is one of the key symptoms that affect quality of life. Physicians and patients' relatives frequently underestimate MS-related fatigue; the latter may occur at any disease stage, its degree is inadequate to physical exercise and reduces after a short-term daytime rest. Fatigue due to MS is not directly related to the degree of paresis; however, it is more common in patients with pyramidal insufficiency. Overfatigue may be the first symptom of an MS exacerbation. The genesis of fatigue in MS is not known with certainty. The development of this symptom is associated with impairments in neuroimmune responses and biochemical processes and with the administration of some drugs. Special tests and scales are used to objectify the degree of fatigue. The most commonly used questionnaires are the Fatigue Severity Scores to rate physical and mental fatigue, as well as the Modified Fatigue Impact Scale in patients having MS. When a patient with MS complains about fatigue, it is necessary to rule out its other possible causes and to specify its relation to MS and the necessity of fatigue correction. Аmantadine is one of the drugs used for the symptomatic therapy of MS. This paper presents the data of randomized clinical trials evaluating the efficacy and safety of this drug for the symptomatic treatment of MS. Correction of MS-related fatigue requires a multidisciplinary approach that involves a combination of drug therapy, therapeutic exercises, active lifestyle, and relatives' understanding.

  5. Fatigue susceptibility of an endodontic fibre post material.

    Science.gov (United States)

    Barbizam, J V B; White, S N

    2014-02-01

    To evaluate effects of ageing and fatigue on the elastic modulus and short-beam shear strength of a quartz fibre/epoxy resin post material. Cylindrical specimens (25 × 2.2 mm) were made. Elastic moduli were dynamically measured before immersion in water; after immersion in water; periodically during storage in water for up to 7 years; periodically during thermal cycling in water for up to 10 000 cycles to produce thermo-mechanical fatigue; and periodically during boiling in water for up to 100 h. After ageing, the specimens underwent short-beam shear strength testing. Elastic modulus was significantly decreased by thermal cycling and by immersion in boiling water, but not by water storage. Short-beam shear strength was profoundly decreased by all three ageing processes. Short-beam shear strength was much more sensitive than elastic modulus to the ageing or fatigue processes applied in this study. A representative endodontic fibre post material was susceptible to a variety of ageing and fatigue processes. The effects of ageing and fatigue had a more pronounced impact on short-beam shear strength than on elastic modulus. The effects of boiling in water and thermal cycling in water were considerably larger than those of simple storage in water. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  6. Environmental fatigue evaluation for Kori unit 1 surge line

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jun Seog [Korea Electric Power Research Institue, Daejeon (Korea, Republic of); Park, Chi Yong; Kang, Seon Ye [Korea Power Engineering Company, Inc., Yongin (Korea, Republic of)

    2009-07-01

    The original design of Kori Unit 1 did not consider the thermal stratification phenomena in the surge line piping and the insurge / outsurge out of limit in the pressurizer lower head during plant heat up and cooldown condition. For the plant life extension over 20 years, the metal fatigue evaluation considering the effects of reactor water environment was performed to determine the impact of the insurge / outsurge out of transients and thermal stratification transients, in conjunction with design transient effects, on the environmental fatigue usage factors at the critical locations of the surge line and pressurizer surge nozzle. In this paper, the effects of the environmental fatigue were evaluated and discussed by confining to the thermal stratification transients in the surge line and insurge / outsurge transients in the pressurizer surge nozzle. Also, the use of fatigue life correction factor to incorporate the effects of environment into the ASME Code fatigue evaluation for the surge line piping and pressurizer surge nozzle was discussed in this paper.

  7. The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

    Science.gov (United States)

    2008-05-01

    normalized and compared 38 to normalized SAFTE predictions. See text for details. Figure 3 Fatigue plots for fatigue susceptible vs. fatigue...has 5 seconds to press the button to get points for successful signal detections. Lower tones are given with greater frequency and responses to...address the first question, and we use predictions of the Sleep Activity Fatigue Task Effectiveness, or SAFTE model (Hursh, Redmond, Johnson, Thorne

  8. Smoother Turbine Blades Resist Thermal Shock Better

    Science.gov (United States)

    Czerniak, Paul; Longenecker, Kent; Paulus, Don; Ullman, Zane

    1991-01-01

    Surface treatment increases resistance of turbine blades to low-cycle fatigue. Smoothing removes small flaws where cracks start. Intended for blades in turbines subject to thermal shock of rapid starting. No recrystallization occurs at rocket-turbine operating temperatures.

  9. Damage and service life of nickel-base alloys under thermal-mechanical fatigue stress at different phase positions; Schaedigung und Lebensdauer von Nickelbasislegierungen unter thermisch-mechanischer Ermuedungsbeanspruchung bei verschiedenen Phasenlagen

    Energy Technology Data Exchange (ETDEWEB)

    Guth, Stefan

    2016-07-01

    This work considers the behaviour of two nickel-base alloys (NiCr22Co12Mo9 and MAR-M247 LC) under thermo-mechanical fatigue loading with varying phase angles between mechanical strain and temperature. The investigations focus on the characterisation of microstructures and damage mechanisms as a function of the phase angle. Based on the results, a life prediction model is proposed.

  10. Analysis on nondestructive temperature distribution of tire tread part in a running using infrared thermal vision camera

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Yeol; Yang, Dong Jo; Ma, Sang Dong [Mechanical Engineeering Division, Chosun University, Kwangju (Korea, Republic of); Park, Byoung Gu; Lee, Ju Wan [Kumho Industrial Tire Bussiness Unit, Seoul (Korea, Republic of)

    2001-11-15

    The experimental method which investigates validity of numerical simulation for wheeling tires has not developed until now. Separation of belt caused by sudden temperature increase is the most serious problem with wheeling tires. Actually, separation of belt is closely related with the life cycle and design of tires. It is important to investigate the temperature history of tires because sudden temperature increase on belt accelerates the thermal fatigue and then causes the destruction of bending area in the radial direction. Therefore, in the present study, finite element method (FEM) was used to obtain the accurate temperature distribution of tire. Its results were compared with experimental data acquired by infrared thermal camera.

  11. Fatigue strength degradation of metals in corrosive environments

    Science.gov (United States)

    Adasooriya, N. D.; Hemmingsen, T.; Pavlou, D.

    2017-12-01

    Structures exposed to aggressive environmental conditions are often subjected to time-dependent loss of coating and loss of material due to corrosion; this causes reduction in the cross-sectional properties of the members, increased surface roughness, surface irregularities and corrosion pits, and degradation of material strengths. These effects have been identified and simulated in different research studies. However, time and corrosive media dependent fatigue strength curves for materials have not been discussed in the design or assessment guidelines for structures. This paper attempts to review the corrosion degradation process and available approaches/models used to determine the fatigue strength of corroded materials and to interpolate corrosion deterioration data. High cycle fatigue and full range fatigue life formulae for fatigue strength of corroded materials are proposed. The above formulae depend on the endurance limit of corroded material, in addition to the stress-life fatigue curve parameters of the uncorroded material. The endurance limit of corroded material can either be determined by a limited number of tests in the very high-cycle fatigue region or predicted by an analytical approach. Comparison with experimentally measured corrosion fatigue behavior of several materials is provided and discussed.

  12. Fatigue life estimation in welded joints under multiaxial loadings

    Directory of Open Access Journals (Sweden)

    Sabrina Vantadori

    2009-07-01

    Full Text Available Welded joints are frequently locations for cracks initiation and propagation that may cause fatigue failure of engineering structures. Biaxial or triaxial stress-strain states are present in the vicinity of welded joints, due to local geometrical constraints, welding processes and/or multiaxial external loadings. Fatigue life evaluation of welded joints under multiaxial proportional (in-phase cyclic loading can be performed by using conventional hypotheses (e.g. see the von Mises criterion or the Tresca criterion on the basis of local approaches. On the contrary, the fatigue life predictions of welded joints under non-proportional (out-ofphase cyclic loading are generally unsafe if these conventional hypotheses are used. A criterion initially proposed by the authors for smooth and notched structural components has been extended to the fatigue assessment of welded joints. In more detail, fatigue life of welded joints under multiaxial stress states can be evaluated by considering a nonlinear combination of the shear stress amplitude (acting on the critical plane and the amplitude and the mean value of the normal stress (acting on the critical plane. In the present paper, fatigue lifetimes predicted through the proposed criterion are compared with experimental fatigue life data available in the literature, related to fatigue biaxial tests.

  13. Medial Orbitofrontal Cortex Is Associated with Fatigue Sensation

    Directory of Open Access Journals (Sweden)

    Seiki Tajima

    2010-01-01

    Full Text Available Fatigue is an indispensable bioalarm to avoid exhaustive state caused by overwork or stresses. It is necessary to elucidate the neural mechanism of fatigue sensation for managing fatigue properly. We performed H2O  15 positron emission tomography scans to indicate neural activations while subjects were performing 35-min fatigue-inducing task trials twice. During the positron emission tomography experiment, subjects performed advanced trail-making tests, touching the target circles in sequence located on the display of a touch-panel screen. In order to identify the brain regions associated with fatigue sensation, correlation analysis was performed using statistical parametric mapping method. The brain region exhibiting a positive correlation in activity with subjective sensation of fatigue, measured immediately after each positron emission tomography scan, was located in medial orbitofrontal cortex (Brodmann's area 10/11. Hence, the medial orbitofrontal cortex is a brain region associated with mental fatigue sensation. Our findings provide a new perspective on the neural basis of fatigue.

  14. Fatigue design 1998

    Energy Technology Data Exchange (ETDEWEB)

    Marquis, G.; Solin, J. [eds.] [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    These preprints contain the presentations to be delivered at the Fatigue Design 1998 symposium held on May 26-29, 1998 in Espoo. Fatigue Design 1998 is the tenth in a series of VTT symposia addressing the challenge of fatigue of materials, components and structures. Previous international events were in 1992 and 1995. The key theme of the current meeting is `RELIABILITY`. The two volumes (VTT symposium 181-182) represent 56 contributions by authors representing 26 countries. Emphasis has been given to application oriented research topics that report new technologies, new uses of existing methods and case studies. The objective of the symposium is to bring together researchers and engineers to share experiences and new innovations in designing reliable components to resist alternating loads. (orig.)

  15. Myth vs. Fact: Adrenal Fatigue

    Science.gov (United States)

    ... Endocrinologist Search Featured Resource New Mobile App DOWNLOAD Adrenal Fatigue October 2017 Download PDFs English Editors Irina Bancos, MD Additional Resources Mayo Clinic What is adrenal fatigue? The term “adrenal fatigue” has been used ...

  16. Modafinil May Alleviate Poststroke Fatigue

    DEFF Research Database (Denmark)

    Poulsen, Mai Bang; Damgaard, Bodil; Zerahn, Bo

    2015-01-01

    was randomized, double-blinded, and placebo-controlled. Patients were treated with 400-mg modafinil or placebo for 90 days. Assessments were done at inclusion, 30, 90, and 180 days. The primary end point was fatigue at 90 days measured by the Multidimensional Fatigue Inventory-20 general fatigue domain......BACKGROUND AND PURPOSE: Poststroke fatigue is common and reduces quality of life. Current evidence for intervention is limited, and this is the first placebo-controlled trial to investigate treatment of poststroke fatigue with the wakefulness promoting drug modafinil. METHODS: The trial....... Secondary end points included the Fatigue Severity Scale, the Montreal Cognitive Assessment, the modified Rankin Scale and the Stroke-specific quality of Life questionnaire. Adult patients with a recent stroke achieving a score of ≥12 on the Multidimensional Fatigue Inventory-20 general fatigue domain were...

  17. Coping with cancer -- managing fatigue

    Science.gov (United States)

    ... Fatigue is a feeling of tiredness, weakness, or exhaustion. It is different from drowsiness, which can be ... chap 45. National Cancer Institute. Fatigue (PDQ) - Health professional version. Cancer.gov Web site. Updated January 13, ...

  18. Treatments for chronic fatigue syndrome

    National Research Council Canada - National Science Library

    Rimes, K A; Chalder, T

    2005-01-01

    To review studies evaluating the treatment of chronic fatigue and chronic fatigue syndrome, to describe predictors of response to treatment and to discuss the role of the occupational health physician...

  19. Determinants of fatigue and stress.

    Science.gov (United States)

    Kocalevent, Rüya D; Hinz, Andreas; Brähler, Elmar; Klapp, Burghard F

    2011-07-20

    Fatigue can be triggered by previous perceived stress which may lead to impairment of performance and function. The purpose of the study was to investigate the relationship between fatigue and perceived stress. Health determinants including sociodemographic factors for associations between fatigue and perceived stress in the general population (N = 2,483) are outlined. Fatigue and stress were assessed with the Chalder Fatigue Scale (CFS) and the Perceived Stress Questionnaire (PSQ). Within the general population, 25.9% of male and 34.5% of female respondents reported moderate fatigue during the last six months; 9.7% of subjects reported substantial fatigue lasting six months or longer. An adjusted regression analysis (R2corr = .28, p rates of fatigue and perceived stress: female gender, divorce/separation, low social class and poor health status. We conclude that the two conditions overlap most in terms of socio-economic status and self-perceived health status.

  20. The relationship between fatigue and light exposure during chemotherapy

    Science.gov (United States)

    Liu, Lianqi; Marler, Matthew R.; Parker, Barbara A.; Jones, Vicky; Johnson, Sherella; Cohen-Zion, Mairav; Fiorentino, Lavinia; Sadler, Georgia Robins; Ancoli-Israel, Sonia

    2006-01-01

    Background Fatigue is one of the most common and distressing complaints among cancer patients, not only during radiation and chemotherapy, but also for months to years after the completion of treatment. Fatigue interferes with patients’ daily lives, reduces their quality of life, and is often a significant reason why patients discontinue treatment. We hypothesized that some of the fatigue may be related to disrupted circadian rhythms and low light exposure. The main objective of this study therefore was to investigate the association between fatigue and light exposure among patients with breast cancer. Methods As part of a larger, ongoing prospective study on fatigue, sleep, and circadian rhythms in patients with breast cancer, an analysis of 63 women newly diagnosed with stage I–IIIA breast cancer and scheduled to receive four cycles of adjuvant or neoadjuvant anthracycline-based chemotherapy was conducted. Data were collected before and during weeks 1, 2, and 3 of cycle 1 and cycle 4. Fatigue was assessed using the Short Form of Multidimensional Fatigue Symptom Inventory. Light exposure was recorded with a wrist actigraph. Results There were significant correlations between fatigue levels and light exposure (r=−0.28 to −0.45) within both cycle 1 and cycle 4, such that higher levels of fatigue were associated with less light exposure. There were also significant correlations between changes in light exposure and changes in fatigue within the first 2 weeks of each cycle (r=−0.28 to −0.52). Conclusions Increased fatigue was significantly correlated with decreased light exposure among patients with breast cancer. Although the cause and effect of exacerbated fatigue and decreased light exposure cannot be confirmed by the current study, and lower light exposure may just in part be due to the fatigued patients spending less time outdoors in bright light, two hypotheses are proposed about the mechanisms by which light may alleviate the fatigue of patients

  1. Impact of cognitive fatigue on gait and sway among older adults: A literature review

    Directory of Open Access Journals (Sweden)

    Stephanie Grobe

    2017-06-01

    Full Text Available Cognitive fatigue is an alteration in central nervous system (CNS processing due to prolonged performance of mentally demanding tasks. Decreased gait speed and increased stride length variability have been noted in cognitively fatigued older adults (≥65 years. Further, cognitive fatigue may weaken the visual, vestibular, and proprioceptive systems of the CNS, contributing to increased postural sway. Detriments in gait and sway caused by cognitive fatigue could increase fall risk. The objective of this literature review was to evaluate the impact of cognitive fatigue on changes in gait and postural sway and its role in fall risk.

  2. Fatigue Load Modeling and Control for Wind Turbines based on Hysteresis Operators

    DEFF Research Database (Denmark)

    Barradas Berglind, Jose de Jesus; Wisniewski, Rafal; Soltani, Mohsen

    2015-01-01

    method based on hysteresis operators, which can be used in control loops. Furthermore, we propose a model predictive control (MPC) strategy that incorporates the online fatigue estimation through the objective function, where the ultimate goal in mind is to reduce the fatigue load of the wind turbine......The focus of this work is on fatigue load modeling and controller design for the wind turbine level. The main purpose is to include a model of the damage effects caused by the fatigue of the wind turbine components in the controller design process. This paper addresses an online fatigue estimation...

  3. Influence of defects on the very high cycle fatigue behaviour of forged aeronautic titanium alloy

    Directory of Open Access Journals (Sweden)

    Nikitin Alexander

    2014-06-01

    Full Text Available This paper is focused on fatigue failure of forged aeronautic titanium alloy Ti-6Al-4Mo under VHCF loading. Continuous fatigue tests were carried out in gigacycle fatigue regime (up to on 1010 cycles on specimens machined from real aircraft compressor disk produced by forging. It has been shown, that crack initiation site shifts from surface to subsurface location with stress amplitude decreasing and fatigue life increasing. Microstructural inhomogeneities so that “hard” alpha particles, borders of large alpha lamella clusters and TiN particles are the cause of fatigue crack nucleation in forged Ti-6Al-4Mo titanium alloy under VHCF loading.

  4. Interventions for fatigue in peripheral neuropathy.

    Science.gov (United States)

    White, Claire M; van Doorn, Pieter A; Garssen, Marcel P J; Stockley, Rachel C

    2014-12-18

    a favourable outcome six weeks post-intervention (odds ratio (OR) 0.56 (95% confidence interval (CI) 0.22 to 1.35, N = 74, P = 0.16). We assessed the quality of this evidence as low. Two parallel-group randomised double-blind, placebo-controlled trials comparing the effects of two doses of ascorbic acid with placebo for reducing fatigue in adults with Charcot-Marie-Tooth disease type 1A (CMT1A) showed that the effects of ascorbic acid at either dose are probably small (standardised mean difference (SMD) -0.12 (95% CI -0.32 to 0.08, n = 404, P = 0.25)) for change in fatigue after 12 to 24 months (moderate quality evidence). Neither ascorbic acid study measured fatigue at four to 12 weeks, which was our primary outcome measure. No serious adverse events were reported with amantadine. Serious adverse events were reported in the trials of ascorbic acid. However,risk of serious adverse events was similar with ascorbic acid and placebo. One small imprecise study in people with GBS showed uncertain effects of amantadine on fatigue. In two studies in people with CMT1A there is moderate-quality evidence that ascorbic acid has little meaningful benefit on fatigue. Information about adverse effects was limited, although both treatments appear to be well tolerated and safe in these conditions.There was no evidence available from RCTs to evaluate the effect of other drugs or other interventions for fatigue in either GBS, CMT1A or other causes of peripheral neuropathy. The cost effectiveness of different interventions should also be considered in future randomised clinical trials.

  5. Fatigue strength testing of LTCC and alumina ceramics bonds

    Science.gov (United States)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  6. [Chronic fatigue syndrome: more than fatigue].

    Science.gov (United States)

    Royes, Badía; Alvarez, Carballo; Lalinde, Sevillano; Vidal, Llinas; Martín, Alegre

    2010-12-01

    Chronic fatigue syndrome (CFS) is a disease recognized by all international medical organizations and WHO, and is classified under the code G93.3 of the International Classification of Diseases. Its prevalence is estimated around 2.54% being more common in women than in men (8/2) aged between 20 and 40 Is defined as a chronic new description characterized by the presence of subjective feeling of fatigue and exhaustion long disabling of more than 6 months duration that is not relieved by rest. It is a multisystem disorder that often presents a significant number of comorbid phenomena. Not known until specific tests to confirm the diagnosis, nor is there a cure to solve this health problem definitively The strongest evidence is based on the multidisciplinary approach for the symptomatic treatment of pain, sleep disorders, neurocognitive dysfunction, autonomic and control of depression and anxiety. The specific contribution of nursing to care for the person who lives and live with the SFC should be developed primarily in the field of health education and supportive care, support and assistance to help the patient and their relatives are an adaptive response to changes in health.

  7. Fatigue and acute/chronic anaemia.

    Science.gov (United States)

    Bager, Palle

    2014-04-01

    Fatigue in patients with gastrointestinal (GI) diseases can be caused by several conditions and anaemia is one of them. Anaemia can be caused by acute GI bleeding, or it can appear in relation to more chronic conditions: iron deficiency anaemia (IDA) and/or anaemia of chronic disease (ACD). Acute anaemia due to acute upper GI bleedings (AUGIB) is often treated with blood transfusions and/or oral iron supplementations. The need for blood transfusions prior to endoscopic intervention has been well described in guidelines. However, guidelines for the monitoring and treatment of anaemia in patients after nonvariceal AUGIB are generally lacking. A retrospective study showed that more than 80% of patients were discharged from hospital with anaemia and less than 20% of them were recommended iron supplementations. Chronic anaemia in inflammatory bowel diseases (IBD) is well known. Anaemia can be caused by deficiency conditions (iron, folic acid or vitamin B12); chronic bleeding; inflammation or medication (or a combination of these). Fatigue in IBD is found in 40% of IBD patients, even with disease in remission. The PhD dissertation is based on two studies. 1. A randomised placebo controlled trial where patients were allocated to iron supplementation (oral or intravenous) or placebo. Patients with nonvariceal AUGIB and anaemia were included in the study (N = 97). The primary follow-up time was 13 weeks, followed by additional three months follow-up. 2. A cross-sectional study including Scandinavian outpatients with IBD. Five hospitals in Denmark, Norway and Sweden included consecutively 5% of their cohort of patients with IBD (N = 429). The aims were: 1. To investigate the effect of iron supplementation in patients who had anaemia after endoscopic intervention for AUGIB. Furthermore, to investigate the health-related quality of life (HRQoL) and fatigue in these patients. 2. To determine the prevalence and type of anaemia, iron deficiency (ID) and fatigue in an unselected

  8. Research on Fatigue Strain and Fatigue Modulus of Concrete

    Directory of Open Access Journals (Sweden)

    Fangping Liu

    2017-01-01

    Full Text Available Concrete fatigue strain and fatigue modulus evolution play a vital role in the evaluation of the material properties. In this paper, by analyzing the advantages and disadvantages of existing concrete strain analysis methods, the level-S nonlinear fatigue strain model was proposed. The parameters’ physical meaning, the ranges, and the impact on the shape of the curve were all discussed. Then, the evolution model of fatigue modulus was established based on the fatigue strain evolution model and the hypothesis of fatigue modulus inversely related fatigue strain amplitude. The results indicate that the level-S model covered all types of fatigue strain evolution. It is very suitable for the description of strain evolution of concrete for its strong adaptability and high accuracy. It was found that the fitting curves coincided with the experimental curves very well, and the correlation coefficients were all above 0.98. The evolution curves of fatigue strain modulus both have three stages, namely, variation phase, linear change stage, and convergence stage. The difference is that the fatigue strain evolution curve is from the lower left corner to the upper right corner, but the fatigue modulus evolution curve is from the upper left corner to the right lower corner.

  9. The Nature of Fatigue in Chronic Fatigue Syndrome.

    Science.gov (United States)

    Olson, Karin; Zimka, Oksana; Stein, Eleanor

    2015-10-01

    In this article, we report the findings of our study on the nature of fatigue in patients diagnosed with chronic fatigue syndrome. Using ethnoscience as a design, we conducted a series of unstructured interviews and card sorts to learn more about how people with chronic fatigue syndrome describe fatigue. Participants (N = 14) described three distinct domains: tiredness, fatigue, and exhaustion. Most participants experienced tiredness prior to diagnosis, fatigue during daily life, and exhaustion after overexertion. We also discuss participants' ability to adapt to a variety of stressors and prevent shifts to exhaustion, and relate our findings to stress theory and other current research. Primary strategies that promoted adaptation to stressors included pacing and extended rest periods. These findings can aid health care professionals in detecting impending shifts between tiredness, fatigue, and exhaustion and in improving adaptive strategies, thereby improving quality of life. © The Author(s) 2015.

  10. Fatigue approach for addressing environmental effects in fatigue usage calculation

    Energy Technology Data Exchange (ETDEWEB)

    Wilhelm, Paul; Rudolph, Juergen [AREVA GmbH, Erlangen (Germany); Steinmann, Paul [Erlangen-Nuremberg Univ., erlangen (Germany). Chair of Applied Mechanics

    2015-04-15

    Laboratory tests consider simple trapezoidal, triangle, and sinusoidal signals. However, actual plant components are characterized by complex loading patterns and periods of holds. Fatigue tests in water environment show, that the damage from a realistic strain variation or the presence of hold-times within cyclic loading results in an environmental reduction factor (Fen) only half that of a simple waveform. This study proposes a new fatigue approach for addressing environmental effects in fatigue usage calculation for class 1 boiler and pressure vessel reactor components. The currently accepted method of fatigue assessment has been used as a base model and all cycles, which have been comparable with realistic fatigue tests, have been excluded from the code-based fatigue calculation and evaluated directly with the test data. The results presented show that the engineering approach can successfully be integrated in the code-based fatigue assessment. The cumulative usage factor can be reduced considerably.

  11. Investigation of casing connection failure mechanisms in thermal wells

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J. [C-FER Technologies, Edmonton, AB (Canada)

    2009-07-01

    Thermal well technologies use casing strings that consist of casing joints linked by threaded connections that are cemented over the wellbore's length in order to provide structural support and hydraulic isolation to the wellbore. Studies have demonstrated that over 80 per cent of uphole casing failures occur at the casing joint connections, and are caused by thread rupture or structural damage. This study discussed thermal well failures related to casing connection damage. Finite element analyses (FEA) were then conducted to consider various critical load conditions with a generic premium casing connection. The study considered structural integrity losses, fatigue, and leakage during connection installation. Results of the study were then used to optimize casing connection designs. The study showed that thermal cycle and curvature loading can have an impact on the structural and sealing performance of premium connections. Connection structural performance should be evaluated in order to determine appropriate designs for thermal well applications. It was concluded that the connection shoulder region is a critical area for material fatigue failure. 12 refs., 9 figs.

  12. [Review of driver fatigue/drowsiness detection methods].

    Science.gov (United States)

    Wang, Lei; Wu, Xiaojuan; Yu, Mengsun

    2007-02-01

    Driver fatigue/drowsiness is one of the important causes of serious traffic accidents and results in so many people deaths or injuries, but also substantial directly and indirectly economic expenses. Therefore, many countries make great effort on how to detect drowsiness during driving. In this paper, we introduce the recent developments of driver fatigue/drowsiness detection technology of world wide and try to classify the existing methods into several kinds according to different features measured, and analyzed. Finally, the challenges faced to fatigue/drowsiness detection technology and the development trend are presented.

  13. Fatigue and fatigue crack growth processes in hard tissues: The importance of age and surface integrity

    Science.gov (United States)

    Majd, Hessam

    With the progressive increase in partially and fully dentate seniors, fracture has become an increasingly common form of restored tooth failure. Dentin undergoes progressive changes in microstructure with patient age, and studies are now suggesting that there is a reduction in fatigue strength and fatigue crack growth resistance of this tissue. This dissertation explores aging of dentin, the influence of flaws that are introduced during restorative processes on the fatigue properties of dentin, and proposes models for characterizing the damage initiation and growth process during fatigue of dentin. Results from this investigation show that the fatigue crack growth properties (Paris Law parameters (C, m) andDeltaKth) of human dentin undergo the most significant changes at a patient age of 42 years. Based on the fatigue crack growth responses, three age groups were established including young (age≤33), aged (34≤age ≤49) and old (50≤age) patients for further analysis. There were significant differences in the initiation and growth behavior between the tissues of patients from the three age groups. With regards to the influence of restorative processes, there was no influence on the quasi-static responses of dentin. However, the endurance limit of dentin treated with the dental burs (28 MPa) and abrasive air jet (35 MPa) were approximately 36% and 20% lower than that of the control (44 MPa), respectively. Both cutting processes caused a significant reduction (p≤0.0001) in fatigue strength. An accumulative damage model was developed to characterize fatigue of the control and bur treated dentin as well as provide a model for fatigue life prediction. The damage models were derived as a function of number of loading cycles (N), and ratio of applied stress to ultimate strength (r). The developed models provide estimations for the initial state of damage, the state of damage during the life, as well as the damage accumulation rate for cyclic loading of dentin

  14. Fatigue in Multidirectional Composites

    Science.gov (United States)

    Ramani, S. V.; Williams, D. P.

    1982-01-01

    Data in new report on fatique properties of graphite/epoxy composites prove valuable to designers of aircraft, space vehicles, and automobiles. Graphite/epoxy composites are being used increasingly in lightweight load-bearing structures, and fatigue of such structures is always major concern of designers.

  15. Control of Fretting Fatigue

    Science.gov (United States)

    1977-07-01

    Effect of Room Temperature Pre-Strain on Grain Boundary Cavitation in Nimonic 80A," J. Microscopy, 97, pp. 165-170, 1973. 48. Eden, E. M., W. N. Rose...Academic Press, New York, 1971. ♦ 115 . Milestone, W. D., An Investigation of the Basic Mechanisms of Mechanical Fretting and Fretting-Fatigue at

  16. Incompatibility and Mental Fatigue

    Science.gov (United States)

    Herzog, Thomas R.; Hayes, Lauren J.; Applin, Rebecca C.; Weatherly, Anna M.

    2011-01-01

    A straightforward prediction from attention restoration theory is that the level of incompatibility in a person's life should be positively correlated with that person's level of mental (or directed attention) fatigue. The authors tested this prediction by developing a new self-report measure of incompatibility in which they attempted to isolate…

  17. Fatigue 󈨛. Volume 1,

    Science.gov (United States)

    1987-06-01

    are constants in the cyclic Ramberg Osgood represen- tation of material stress-strain curve as in (14), Po is the re- ference load of EPRI limit load...MPa) ci, n = Ramberg -Osgood’s coefficient and strain exponent = Strain rate (s - 1) Tend = Fatigue endurance limit (MPa) &LtdlD = Total and plastic

  18. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, M.M.; Tops, M.

    2003-01-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support

  19. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Committee for Science and Education, Medical. Association of South Africa. Objective. To acknowledge the dinical syndrome chronic fatigue syndrome (CFS) and outline the diagnostic criteria and reasonable management. Outcomes. Attempt at containment of treatmentcost and improvement of the quality of care of patients ...

  20. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Unexplained generalised muscle weakness. 5. Muscle discomfort or myalgia. 6. Prolonged (24 hours or more) generalised fatigue after levels of exercise that would have been tolerated easily in the patient's premorbid state. "7. Generalised headaches (or a type, severity or pattern different from headaches in the premorbid ...

  1. Are nurses able to assess fatigue, exertion fatigue and types of fatigue in residential home patients?

    NARCIS (Netherlands)

    Tiesinga, L.J.; Dijkstra, Ate; Dassen, T.W.N.; Halfens, R.J.G.; van den Heuvel, W.J.A.

    Although fatigue is recognized as a subjective, generalized, extensive and disabling health care problem with a relatively high prevalence among the chronically ill, there have been no studies to show whether nurses caring for fatigued subjects are able to accurately assess the level of fatigue that

  2. Cavitation fatigue and its reversal in sunflower (Helianthus annuus L.).

    Science.gov (United States)

    Stiller, Volker; Sperry, John S

    2002-05-01

    "Cavitation fatigue" is the increased susceptibility of a xylem conduit to cavitation as a result of its prior cavitation. It was investigated whether cavitation fatigue induced in vivo could be repaired in intact plants. Sunflowers (Helianthus annuus L.) were subjected to soil drought in the greenhouse. Native embolism and vulnerability to cavitation was measured in well-watered controls and after 5 d and 10 d of controlled drought. A dramatic cavitation fatigue was observed where droughted xylem that was refilled in the laboratory developed up to 60 PLC (percentage loss of hydraulic conductivity) at -1 MPa versus only 5.2 PLC in non-droughted controls. Rewatered plants showed the complete reversal of cavitation fatigue over 4 d. Reversal of fatigue was correlated with the refilling of embolized vessels in the intact plants (r(2)=0.91, P<0.01), suggesting that xylem transport to fatigued vessels was required for their repair. The in vivo reversal of fatigue was partially duplicated in excised stem segments by perfusing them with root exudates from droughted (DR) and well-watered (WW) plants. The DR exudate had a greater effect, and this was associated with a greater pH in the DR versus WW saps, but there was no difference in total cation concentration. Perfusions with 2 mM CaCl(2) and KCl solutions also partially reversed cavitation fatigue as opposed to no effect with deionized water, suggesting a role of ions in addition to a pH effect. It is suspected that fatigue is caused by stretching and partial disruption of linkages between cellulose microfibrils in inter-conduit pit membranes during air seeding, and that the reversal of fatigue involves restoring these linkages by ingredients in xylem sap.

  3. Determinants of fatigue and stress

    Directory of Open Access Journals (Sweden)

    Brähler Elmar

    2011-07-01

    Full Text Available Abstract Background Fatigue can be triggered by previous perceived stress which may lead to impairment of performance and function. The purpose of the study was to investigate the relationship between fatigue and perceived stress. Method Health determinants including sociodemographic factors for associations between fatigue and perceived stress in the general population (N = 2,483 are outlined. Fatigue and stress were assessed with the Chalder Fatigue Scale (CFS and the Perceived Stress Questionnaire (PSQ. Results Within the general population, 25.9% of male and 34.5% of female respondents reported moderate fatigue during the last six months; 9.7% of subjects reported substantial fatigue lasting six months or longer. An adjusted regression analysis (R2corr = .28, p Conclusion We conclude that the two conditions overlap most in terms of socio-economic status and self-perceived health status.

  4. Fatigue during high-intensity intermittent exercise: application to bodybuilding.

    Science.gov (United States)

    Lambert, Charles P; Flynn, Michael G

    2002-01-01

    Resistance exercise is an activity performed by individuals interested in competition, those who wish to improve muscle mass and strength for other sports, and for individuals interested in improving their strength and physical appearance. In this review we present information suggesting that phosphocreatine depletion, intramuscular acidosis and carbohydrate depletion are all potential causes of the fatigue during resistance exercise. In addition, recommendations are provided for nutritional interventions, which might delay muscle fatigue during this type of activity.

  5. Size effect caused significant reduction of thermal conductivity of GaAs/AlAs distributed Bragg reflector used in semiconductor disk laser

    Science.gov (United States)

    Zhang, Peng; Zhu, Renjiang; Jiang, Maohua; Song, Yanrong; Zhang, Dingke; Cui, Yuting

    2017-11-01

    Thermal properties of the distributed Bragg reflector (DBR) used in the semiconductor gain element are crucial for the performance of a semiconductor disk laser (SDL). For the purpose of more reasonable semiconductor wafer design, so as to improve the thermal management of SDLs, accurate thermal conductivity value of a DBR is under considerable requirement. By the use of equilibrium molecular dynamics method, thermal conductivities of GaAs/AlAs DBRs, which are widely employed in 1 μm waveband SDLs, are calculated, and simulated results are compared with the reported experimental data. Influences of the layer thickness on the thermal conductivities of the DBR structure and the effects of Al composition on the AlxGa1-xAs ternary alloy values are focused and analyzed.

  6. On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

    Energy Technology Data Exchange (ETDEWEB)

    Bhanu Sankara Rao, K.; Halford, G.R. (National Aeronautics Space Agency, Cleveland, OH (United States). Lewis Research Center); Schuster, H. (KFA, Juelich (Germany). Inst. for Reactor Materials)

    1994-08-15

    Alloys engineered for high-temperature application are frequently put into use in a thermodynamically unstable condition. Subsequent exposure to service temperatures may promote many thermally-assisted reactions such as formation, coarsening, and/or coalescence of precipitates. Superposition of cyclic straining may accelerate the kinetics of these reactions but also may cause reaction products having specific features not observed under simple thermal exposure. The influence of cyclic strain-induced microstructural changes on the fatigue behavior has to be considered in terms of their effects on both cyclic strength and life. The occurrence of massive (cellular) precipitation of M[sub 23]C[sub 6] on grain boundaries during elevated temperature low cycle fatigue testing has been reported in Type 304 stainless steel, Type 316 stainless steel, and Inconel 617 superalloy, and its presence has already been linked with reduction in high temperature ductility, an important engineering property on which low cycle fatigue (LCF) life depends to a large extent. Massive precipitation may render the austenitic engineering alloys susceptible to corrosion, which would have important bearing on the performance of these alloys in the oxidizing environments. Furthermore, the long term stability of massive M[sub 23]C[sub 6] particles is particularly important since the transformation of such a large structure into a brittle intermetallic phase (such as sigma) could produce a detrimental effect on the mechanical properties. The conditions and the mechanisms responsible for the occurrence of massive precipitation during LCF have not yet been established. This investigation is specifically aimed at understanding the influence of strain rate on massive precipitation and the mechanism responsible for the occurrence of massive M[sub 23]C[sub 6] precipitation in Alloy 800H during elevated temperature LCF testing.

  7. ISOTHERMAL AND THERMOMECHANICAL FATIGUE OF A NICKEL-BASE SUPERALLOY

    Directory of Open Access Journals (Sweden)

    Carlos Carvalho Engler-Pinto Júnior

    2014-06-01

    Full Text Available Thermal gradients arising during transient regimes of start-up and shutdown operations produce a complex thermal and mechanical fatigue loading which limits the life of turbine blades and other engine components operating at high temperatures. More accurate and reliable assessment under non-isothermal fatigue becomes therefore mandatory. This paper investigates the nickel base superalloy CM 247LC-DS under isothermal low cycle fatigue (LCF and thermomechanical fatigue (TMF. Test temperatures range from 600°C to 1,000°C. The behavior of the alloy is strongly affected by the temperature variation, especially in the 800°C-1,000°C range. The Ramberg-Osgood equation fits very well the observed isothermal behavior for the whole temperature range. The simplified non-isothermal stress-strain model based on linear plasticity proposed to represent the thermo-mechanical fatigue behavior was able to reproduce the observed behavior for both in-phase and out-of-phase TMF cycling.

  8. Finite element simulation of asphalt fatigue testing

    DEFF Research Database (Denmark)

    Ullidtz, Per; Kieler, Thomas Lau; Kargo, Anders

    1997-01-01

    The traditional interpretation of fatigue tests on asphalt mixes has been in terms of a logarithmic linear relationship between the constant stress or strain amplitude and the number of load repetitions to cause failure, often defined as a decrease in modulus to half the initial value. To accomod...... tests are that the extrapolation from laboratory tests to insitu conditions is facilitated and that the gradual deterioration of the asphalt may be predicted, which is useful for pavement management purposes....

  9. The Case for Addressing Operator Fatigue

    OpenAIRE

    Duffy, Jeanne F.; Zitting, Kirsi-Marja; Czeisler, Charles A.

    2015-01-01

    Sleep deficiency, which can be caused by acute sleep deprivation, chronic insufficient sleep, untreated sleep disorders, disruption of circadian timing, and other factors, is endemic in the U.S., including among professional and non-professional drivers and operators. Vigilance and attention are critical for safe transportation operations, but fatigue and sleepiness compromise vigilance and attention by slowing reaction times and impairing judgment and decision-making abilities. Research stud...

  10. High pulse number thermal shock tests on tungsten with steady state particle background

    Science.gov (United States)

    Wirtz, M.; Kreter, A.; Linke, J.; Loewenhoff, Th; Pintsuk, G.; Sergienko, G.; Steudel, I.; Unterberg, B.; Wessel, E.

    2017-12-01

    Thermal fatigue of metallic materials, which will be exposed to severe environmental conditions e.g. plasma facing materials in future fusion reactors, is an important issue in order to predict the life time of complete wall components. Therefore experiments in the linear plasma device PSI-2 were performed to investigate the synergistic effects of high pulse number thermal shock events (L = 0.38 GW m‑2, Δt = 0.5 ms) and stationary D/He (6%) plasma particle background on the thermal fatigue behavior of tungsten. Similar to experiments with pure thermal loads, the induced microstructural and surface modifications such as recrystallization and roughening as well as crack formation become more pronounced with increasing number of thermal shock events. However, the amount of damage significantly increases for synergistic loads showing severe surface roughening, plastic deformation and erosion resulting from the degradation of the mechanical properties caused by bombardment and diffusion of D/He to the surface and the bulk of the material. Additionally, D/He induced blistering and bubble formation were observed for all tested samples, which could change the thermal and mechanical properties of near surface regions.

  11. Evaluation of Work Fatigue in Loading Workers Using Muscle Fatigue Assessment Method (MFA: A Case Study in a Brick Factory

    Directory of Open Access Journals (Sweden)

    Haji Omid Kalte

    2016-09-01

    Full Text Available Introduction and purpose: Work fatigue is one of the main causes of workrelated musculoskeletal disorders and reduced productivity in industry. Therefore, it is vital to evaluate work fatigue, especially muscle fatigue, to determine the permissible workload. This study aimed to evaluate muscle fatigue of brick field workers. Methods: This cross-sectional study was conducted on transportation sector workers in Pey Dezh Brick Production Company, Golestan, Iran in 2015. In this research, the qualitative of Muscle Fatigue Assessment (MFA method was used to assess the level of fatigue. Duration of each task and frequency of efforts were determined using the level of effort to obtain a numerical result for comparison with the standard level. Results: The evaluated task was to remove paired bricks from the conveyor and transfer them to trailer truck by workers. The final results revealed that lower back tolerated the most amount of pressure (score=323, followed by the shoulders and wrist of the right hand (scores=313, which were assigned to the fatigue level. Therefore, the highest total fatigue of workload was imposed on these body parts. Conclusion: According to the results of this study, the upper limbs of workers incurred the highest burden in lifting bricks, and there was a in risk of WMSDS due to high workload. Therefore, it is recommended that working systems be improved through rotating work and reducing the number of transferred bricks to avoid risks caused by accumulation of fatigue.

  12. Different types of fatigue in patients with facioscapulohumeral dystrophy, myotonic dystrophy and HMSN-I. Experienced fatigue and physiological fatigue.

    NARCIS (Netherlands)

    Kalkman, J.S.; Zwarts, M.J.; Schillings, M.L.; Engelen, B.G.M. van; Bleijenberg, G.

    2008-01-01

    Although fatigue is a common symptom in neuromuscular disorders, little is known about different types of fatigue. Sixty-five FSHD, 79 adult-onset MD and 73 HMSN type I patients were studied. Experienced fatigue was assessed with the CIS-fatigue subscale. Physiological fatigue was measured during a

  13. ANSYS Creep-Fatigue Assessment tool for EUROFER97 components

    Directory of Open Access Journals (Sweden)

    M. Mahler

    2016-12-01

    Full Text Available The damage caused by creep-fatigue is an important factor for materials at high temperatures. For in-vessel components of fusion reactors the material EUROFER97 is a candidate for structural application where it is subjected to irradiation and cyclic thermo-mechanical loads. To be able to evaluate fusion reactor components reliably, creep-fatigue damage has to be taken into account. In the frame of Engineering Data and Design Integration (EDDI in EUROfusion Technology Work Programme rapid and easy design evaluation is very important to predict the critical regions under typical fusion reactor loading conditions. The presented Creep-Fatigue Assessment (CFA tool is based on the creep-fatigue rules in ASME Boiler Pressure Vessel Code (BPVC Section 3 Division 1 Subsection NH which was adapted to the material EUROFER97 and developed for ANSYS. The CFA tool uses the local stress, maximum elastic strain range and temperature from the elastic analysis of the component performed with ANSYS. For the assessment design fatigue and stress to rupture curves of EUROFER97 as well as isochronous stress vs. strain curves determined by a constitutive model considering irradiation influence are used to deal with creep-fatigue damage. As a result allowable number of cycles based on creep-fatigue damage interaction under given hold times and irradiation rates is obtained. This tool can be coupled with ANSYS MAPDL and ANSYS Workbench utilizing MAPDL script files.

  14. Fatigue-induced adaptive changes of anticipatory postural adjustments.

    Science.gov (United States)

    Strang, Adam J; Berg, William P

    2007-03-01

    To examine the fatigue-induced adaptive changes (e.g., timing) of anticipatory postural adjustments (APAs), APAs of 30 research participants were recorded before (baseline) and after (post-test) conditions of either rest (control group, n=15) or fatigue (fatigue group, n=15). Muscle fatigue was generated using a dead-lift exercise performed to exhaustion. Self-initiated postural perturbations were induced using a rapid unilateral arm-raising maneuver (focal movement), and APAs were obtained using electromyography (EMG) recorded bilaterally in the lumbar and thoracic paraspinal muscles as well as the hamstring muscles. Postural stability during the focal movement was assessed using a force plate. Results showed that fatigue had no effect on postural stability during the focal movement, and yet caused earlier APA onsets in three of the six muscles evaluated. In spite of early APA activation, the APA EMG integrals of two of the three postural control muscles which exhibited fatigue-induced early APA onsets (T9 and L4 contralateral paraspinals) did not differ between baseline and post-test measures. The findings suggest that early APA onset may enhance postural stability by permitting a longer duration APA which can counteract fatigue-induced decreases in the force-producing capability of muscles that contribute to postural stability.

  15. Variable Amplitude Fatigue

    Science.gov (United States)

    Ranganathan, Narayanaswami; Joly, Damien; Leroy, René

    Fatigue crack growth behavior of selected aluminum alloys under variable amplitude loading is discussed in this study, based principally on experimental observations. The tests include single overloads tests in different environments, block load tests and tests using an aircraft wing loading spectrum. It is shown that conditions favoring a planar slip behavior lead to very high delays as opposed to conditions leading to multiple slip behavior. The Aluminium Liithium alloy studied here, has the best fatigue crack growth resistance in almost all test conditions studied here as compared to other conventional alloys. Under the spectrum loading studied here, the same alloy exhibits a change in micromechanism leading to a four fould acceleration of growth rates. Acceptable life predictions can be made, by taking into account this crack acceleration effect.

  16. Effect of functional fatigue on vertical ground-reaction force in individuals with flat feet.

    Science.gov (United States)

    Boozari, Sahar; Jamshidi, Ali Ashraf; Sanjari, Mohammad Ali; Jafari, Hassan

    2013-08-01

    Flat foot is one of the lower extremity deformities that might change kinetic variables of gait. Fatigue is one of the factors that can alter the vertical ground-reaction force (GRF). The effect of a fatiguing condition on vertical GRF has not been documented in individuals with flat feet. To examine the fatigue effect on vertical GRF in individuals with flat feet compared with a normal group during barefoot walking. Repeated-measure ANOVA for the effects of fatigue on individuals with flat feet and normal feet. Biomechanics laboratory. 17 subjects with flat feet and 17 normal subjects (recruited according to their arch-height ratio). Three vertical GRF measures (F1, the first peak force; F2, minimum force; and F3, the second peak force) were extracted before and after a functional fatigue protocol. No significant interaction between fatigue and group was observed for the 3 vertical GRF measures. For F2, fatigue and group effects were significant (P = .001 and P = .02, respectively). Furthermore, F2 was higher in the flat-feet group than in the normal group; F2 also increased after fatigue. For F3, only a significant fatigue effect was observed (P = .004). F3 decreased after fatigue in both groups. In the flat-feet group, a decrease in the variation of vertical GRF might be due to more flexible foot joints. After fatigue, muscles might lose their ability to control the foot joints and cause higher F2 in the flat-feet group.

  17. Fatigue 󈨛. Volume 3,

    Science.gov (United States)

    1987-06-01

    are given above. Sal and Sar were de- termined by tensile tests on single layers. Sad was based on an estimation of the thickness of the inter- facial...effective stress R = gas constart T = absol,,te temperature This apparent activation energy for the fatigue proceos in PVC is approximately half that...in distilled water could be de- termined . The temperature dependence of thus determined Kie is presented in Fig. 6 as a function of reciprocal of the

  18. Biaxial fatigue behavior of a powder metallurgical TRIP steel

    Directory of Open Access Journals (Sweden)

    S. Ackermann

    2015-10-01

    Full Text Available Multiaxial fatigue behavior is an important topic in critical structural components. In the present study the biaxial-planar fatigue behavior of a powder metallurgical TRIP steel (Transformation Induced Plasticity was studied by taking into account martensitic phase transformation and crack growth behavior. Biaxial cyclic deformation tests were carried out on a servo hydraulic biaxial tension-compression test rig using cruciform specimens. Different states of strain were studied by varying the strain ratio between the axial strain amplitudes in the range of -1 (shear loading to 1 (equibiaxial loading. The investigated loading conditions were proportional due to fixed directions of principal strains. The studied TRIP steel exhibits martensitic phase transformation from -austenite via ε-martensite into α‘- martensite which causes pronounced cyclic hardening. The α‘-martensite formation increased with increasing plastic strain amplitude. Shear loading promoted martensite formation and caused the highest α‘-martensite volume fractions at fatigue failure in comparison to uniaxial and other biaxial states of strain. Moreover, the fatigue lives of shear tests were higher than those of uniaxial and other biaxial tests. The von Mises equivalent strain hypothesis was found to be appropriate for uniaxial and biaxial fatigue, but too conservative for shear fatigue, according to literature for torsional fatigue. The COD strain amplitude which is based on crack opening displacement gave a better correlation of the investigated fatigue lives, especially those for shear loading. Different types of major cracks were observed on the sample surfaces after biaxial cyclic deformation by using electron monitoring in an electron beam universal system and scanning electron microscopy (SEM. Specimens with strain ratios of 1, 0.5, -0.1 and -0.5 showed mode I major cracks (perpendicular to the axis of maximum principal strain. Major cracks after shear fatigue

  19. Chronic fatigue syndrome

    Directory of Open Access Journals (Sweden)

    Brkić Snežana

    2011-01-01

    Full Text Available Chronic fatigue syndrome (CFS is defined by a profound, debilitating fatigue, lasting for at least 6 months and resulting in a substantial reduction of occupational, personal, social and educational status. CFS is a relatively poorly recognized clinical entity, although everyday experience shows that there are many patients with CFS symptoms. The incidence and prevalence of CFS remain unknown in most countries; however, the working population is most affected with predominantly female patients in generative period. Although, CFS was first mentioned four centuries ago, mysterious aethiopathogensis of CFS still intrigues scientists as hundreds of studies are still published every year on the subject. About 80 different aetiological CFS factors are mentioned, which can be classified into five basic groups: genetics, immunology, infectious diseases, endocrinology and neuropsychiatry-psychology. Even today the condition is passed established based on the diagnosis by exclusion of organic and psychiatric disorders, which demands u multidisciplinary approach. As the syndrome is often misdiagnosed and mistreated, self-medication is not uncommon in CFS patients’. In addition, such patients usually suffer for years tolerating severe fatigue. Thus, at the moment there are three priorities regarding CFS; understanding pathogenesis, development of diagnostic tests and creating efficient treatment program.

  20. Fatigue syndrome in sarcoidosis.

    Science.gov (United States)

    Górski, Witold; Piotrowski, Wojciech J

    2016-01-01

    Sarcoidosis is an inflammatory disease of unknown etiology. Most commonly it results in the formation of non-caseating granulomas in intrathoracic lymph nodes and lung parenchyma, but the clinical course and picture may be complicated by extrapulmonary involvement and many non-respiratory signs and symptoms which are directly related to the disease. In addition, sarcoidosis patients may suffer from a plethora of symptoms of uncertain or unknown origin. Fatigue is one of these symptoms, and according to some authors it is reported by the majority of patients with active sarcoidosis, but also by a smaller proportion of patients with inactive sarcoidosis, or even with complete clinical and radiological remission. Therefore the term fatigue syndrome is frequently used to name this clinical problem. The definition of fatigue syndrome in sarcoidosis is imprecise and the syndrome is usually recognized by use of validated questionnaires. In this review the uptodate knowledge in this field was presented and different challenges connected with this syndrome were described.

  1. DEGRADATION OF SM2ZR2O7 THERMAL BARRIER COATING CAUSED BY CALCIUM-MAGNESIUM-ALUMINUM-SILICON OXIDE (CMAS) DEPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Honglong; Sheng, Zhizhi; Tarwater, Emily; Zhang, Xingxing; Dasgupta, Sudip; Fergus, Jeffrey

    2015-03-16

    Rare earth zirconates are promising materials for use as thermal barrier coatings in gas turbine engines. Among the lanthanide zirconate materials, Sm2Zr2O7 with the pyrochlore structure has lower thermal conductivity and better corrosion resistance against calcium-magnesium-aluminum-silicon oxide (CMAS). In this work, after reaction with CMAS, the pyrochlore structure transforms to the cubic fluorite structure and Ca2Sm8(SiO4)6O2 forms in elongated grain.

  2. Probabilistic Fatigue Damage Program (FATIG)

    Science.gov (United States)

    Michalopoulos, Constantine

    2012-01-01

    FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes. This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user. It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

  3. Aspects of respiratory muscle fatigue in a mountain ultramarathon race.

    Science.gov (United States)

    Wüthrich, Thomas U; Marty, Julia; Kerherve, Hugo; Millet, Guillaume Y; Verges, Samuel; Spengler, Christina M

    2015-03-01

    Ultramarathon running offers a unique possibility to investigate the mechanisms contributing to the limitation of endurance performance. Investigations of locomotor muscle fatigue show that central fatigue is a major contributor to the loss of strength in the lower limbs after an ultramarathon. In addition, respiratory muscle fatigue is known to limit exercise performance, but only limited data are available on changes in respiratory muscle function after ultramarathon running and it is not known whether the observed impairment is caused by peripheral and/or central fatigue. In 22 experienced ultra-trail runners, we assessed respiratory muscle strength, i.e., maximal voluntary inspiratory and expiratory pressures, mouth twitch pressure (n = 16), and voluntary activation (n = 16) using cervical magnetic stimulation, lung function, and maximal voluntary ventilation before and after a 110-km mountain ultramarathon with 5862 m of positive elevation gain. Both maximal voluntary inspiratory (-16% ± 13%) and expiratory pressures (-21% ± 14%) were significantly reduced after the race. Fatigue of inspiratory muscles likely resulted from substantial peripheral fatigue (reduction in mouth twitch pressure, -19% ± 15%; P fatigue. Forced vital capacity remained unchanged, whereas forced expiratory volume in 1 s, peak inspiratory and expiratory flow rates, and maximal voluntary ventilation were significantly reduced (P muscle strength for inspiratory muscles shown to result from significant peripheral muscle fatigue with only little contribution of central fatigue. This is in contrast to findings in locomotor muscles. Whether this difference between muscle groups results from inherent neuromuscular differences, their specific pattern of loading or other reasons remain to be clarified.

  4. Depth of tissue ablation and residual thermal damage caused by a pixilated 2,940 nm laser in a swine skin model.

    Science.gov (United States)

    Regan, Thomas D; Uebelhoer, Nathan S; Satter, Elizabeth; Ross, E Victor

    2010-07-01

    The purpose of this study was to assess the effects of fluence, pulse stacking, and multiple passes on the depth of injury caused by a fractionated Er:YAG laser in an in vivo farm pig model. DESIGN/MATERIAL/METHODS: A fractionated 2,940 nm Er:YAG laser (Pixel, Alma Lasers, Caesarea, Israel) was applied to the flank skin of a Yorkshire cross pig. The 11 mmx11 mm handpiece was comprised of either 49 or 81 microbeams (200 microm diameter), depending on the tip configuration. There were six different parameter sets divided according to total energy per pulse (150, 285, and 500 mJ) and tip type (81 or 49 microbeams per 11 mmx11 mm macrospot). Each of these six groups was subdivided according to number of stacked pulses (1, 3, and 6) and number of passes (1, 3, and 6). This resulted in a total of 36 treatment parameters. With the 49 microbeam configuration, a single pulse resulted in partial epidermal ablation at 150 mJ, complete epidermal ablation at 285 mJ and partial dermal ablation at 500 mJ to a depth of 90 microm. Stacking the pulses resulted in a significant increase in ablation with each fluence with the maximal depth of ablation measured at 140 microm after six stacked pulses at 500 mJ. Increasing the number of passes did not result in a significant increase in ablative depth, but did create a larger surface area of ablation. Residual thermal damage (RTD) was minimal and remained between 10 and 20 microm. The fractionated Er:YAG laser exhibited some of the same tissue interactions as its fully ablative counterparts. An increase in fluence resulted in an increase in ablative depth with minimal RTD. Additionally, RTD was unaffected by pulse stacking or by additional passes. Differences were that pulse stacking appeared to yield a more rapid decrease in ablation efficiency and additional passes did not seem to increase the depth of ablation.

  5. Graphite nodules in fatigue-tested cast iron characterized in 2D and 3D

    DEFF Research Database (Denmark)

    Mukherjee, Krishnendu; Fæster, Søren; Hansen, Niels

    2017-01-01

    Thick-walled ductile iron casts have been studied by applying (i) cooling rate calculations by FVM, (ii) microstructural characterization by 2D SEM and 3D X-ray tomography techniques and (iii) fatigue testing of samples drawn from components cast in sand molds and metal molds. An analysis has shown...... correlations between cooling rate, structure and fatigue strengths demonstrating the benefit of 3D structural characterization to identify possible causes of premature fatigue failure of ductile cast iron....

  6. Seasonality of cavitation and frost fatigue in Acer mono Maxim.

    Science.gov (United States)

    Zhang, Wen; Feng, Feng; Tyree, Melvin T

    2017-12-08

    Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity (PLC) versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle while frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. This article is protected by copyright. All rights reserved.

  7. Analysis of fatigue life for tube trailer cylinders

    Directory of Open Access Journals (Sweden)

    Xinqi YU

    2015-08-01

    Full Text Available Risk of fatigue failure exists in the tube trailer cylinders under the condition of internal pressure variation and inertial load caused through road transport. In order to estimate the safety state of the cylinders under the action of alternating load, the model of certain geometry sizes is built based on the widely used tube trailer cylinders. The fatigue analysis of tube trailer gas cylinders is made aiming at the action of the internal pressure and the inertial load. The fatigue life distribution of cylinders is obtained under the condition of different loads through the numerical simulation by ANSYS Workbench. The analysis results show that under internal pressure, gas cylinders have limited fatigue life, but can satisfy the requirements; when the inertial load exceeds a certain value, natural gas cylinders of tube trailer is under finite life state, which does not meet the requirements of strength, therefore the inertial load should be controlled.

  8. Transient modelling of loss and thermal dynamics in power semiconductor devices

    DEFF Research Database (Denmark)

    Ma, Ke; Yang, Yongheng; Blaabjerg, Frede

    2014-01-01

    until achieving the steady-state. As a result, a systematic modelling approach is proposed in this paper, which includes the large signal models of the converter system with both electrical and thermal parts, and the corresponding transient models under frequency domain are also extracted. Based...... on the proposed models, the bandwidths of the loss or thermal response to major disturbances in the converter system can be analytically mapped, enabling more advanced tools to investigate the transient characteristics of loss and thermal dynamics in the power electronics devices.......The dynamical behavior of temperature is becoming a critical design consideration for the power electronics, because they are referred as “thermal cycling” which is the root cause of fatigues in the power electronics devices, and thus is closely related to the reliability of the converter...

  9. Fatigue and Muscle Strength Involving Walking Speed in Parkinson’s Disease: Insights for Developing Rehabilitation Strategy for PD

    Directory of Open Access Journals (Sweden)

    Ying-Zu Huang

    2017-01-01

    Full Text Available Background. Problems with gait in Parkinson’s disease (PD are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods. We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC, twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI and Fatigue Severity Scale (FSS. Results. The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion. Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force.

  10. Fatigue and Muscle Strength Involving Walking Speed in Parkinson's Disease: Insights for Developing Rehabilitation Strategy for PD.

    Science.gov (United States)

    Huang, Ying-Zu; Chang, Fang-Yu; Liu, Wei-Chia; Chuang, Yu-Fen; Chuang, Li-Ling; Chang, Ya-Ju

    2017-01-01

    Background . Problems with gait in Parkinson's disease (PD) are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods . We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC), twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI) and Fatigue Severity Scale (FSS). Results . The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion . Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force.

  11. Perceived fatigue following pediatric burns.

    Science.gov (United States)

    Akkerman, Moniek; Mouton, Leonora J; Dijkstra, Froukje; Niemeijer, Anuschka S; van Brussel, Marco; van der Woude, Lucas H V; Disseldorp, Laurien M; Nieuwenhuis, Marianne K

    2017-12-01

    Fatigue is a common consequence of numerous pediatric health conditions. In adult burn survivors, fatigue was found to be a major problem. The current cross-sectional study is aimed at determining the levels of perceived fatigue in pediatric burn survivors. Perceived fatigue was assessed in 23 children and adolescents (15 boys and 8 girls, aged 6-18 years, with burns covering 10-46% of the total body surface area, 1-5 years post burn) using both child self- and parent proxy reports of the Pediatric Quality of Life Inventory Multidimensional Fatigue Scale. Outcomes were compared with reference values of non-burned peers. At group level, pediatric burn survivors did not report significantly more symptoms of fatigue than their non-burned peers. Individual assessments showed, however, that four children experienced substantial symptoms of fatigue according to the child self-reports, compared to ten children according to the parent proxy reports. Furthermore, parents reported significantly more symptoms of fatigue than the children themselves. Age, gender, extent of burn, length of hospital stay, and number of surgeries could not predict the level of perceived fatigue post-burn. Our results suggest that fatigue is prevalent in at least part of the pediatric burn population after 1-5 years. However, the fact that parents reported significantly more symptoms of fatigue then the children themselves, hampers evident conclusions. It is essential for clinicians and therapists to consider both perspectives when evaluating pediatric fatigue after burn and to determine who needs special attention, the pediatric burn patient or its parent. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

  12. Translating Fatigue to Human Performance.

    Science.gov (United States)

    Enoka, Roger M; Duchateau, Jacques

    2016-11-01

    Despite flourishing interest in the topic of fatigue-as indicated by the many presentations on fatigue at the 2015 Annual Meeting of the American College of Sports Medicine-surprisingly little is known about its effect on human performance. There are two main reasons for this dilemma: 1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and 2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. On the basis of the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to suggest the locus of the changes responsible for an observed level of fatigue. Rather, mechanistic studies should be performed with validated experimental models to identify the changes responsible for the reported fatigue. As indicated by three examples (walking endurance in old adults, time trials by endurance athletes, and fatigue in persons with multiple sclerosis) discussed in the review, however, it has proven challenging to develop valid experimental models of fatigue. The proposed framework provides a foundation to address the many gaps in knowledge of how laboratory measures of fatigue and fatigability affect real-world performance.

  13. Fatigue Performance under Multiaxial Loading

    Science.gov (United States)

    1990-01-01

    Fatigue Strength (Study fatigue strength in cor. connect, in box struc.)." Prog. Rpt. 1, Res. Inst. Ishikawajima - Harima Heavy Ind. Co., Ltd., Tokyo, Japan...1," Ishikawajima - Harima Heavy Ind. Co., Ltd. Research Inst., Tokyo, Japan, IIW Doc. No XIII-573-70. Mall, G., and R. Zirn, "Load Carrying Behavior of...1972. Anonymous, "Application of Program Fatigue Test to Member Joints of Hulls," Mitsubishi Heavy Industries LTD, Mitsubishi Technical Bulletin No

  14. Oligocyclic fatigue of the thermo chemically nitrided Ti6AI4V alloys; Fatiga oligociclicade la aleacion Ti6AI4V niturrada termoquimicamente

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, D.; Manero, J. M.; Gil, F. J.; Planell, J. A.

    2001-07-01

    The use of titanium and its alloys in applications with the presence of friction is limited due to low hardness and reduced tribological properties. Some surface treatments are available in order to correct these problems, like the thermal surface treatment by means of nitrogen gaseous diffusion at high temperature. Nitrogen enters into the materials by diffusion, creating a surface layers of increased hardness. Oligocyclic fatigue behaviour in air of Ti6Al4V alloy has been studied. Results show a reduction of oligocyclic fatigue loads up to 10% compared to the not-treated materials. Studies suggest it is not related to the titanium nitride surface layer, but to microstructural changes caused by the high temperature treatment. (Author) 7 refs.

  15. How Chronic Fatigue Syndrome Wears Patients Out

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_167452.html How Chronic Fatigue Syndrome Wears Patients Out Study suggests body amplifies fatigue ... what it's like for those who struggle with chronic fatigue syndrome, and researchers suggest in a new report that ...

  16. Driver fatigue and road safety on Poland's national roads.

    Science.gov (United States)

    Jamroz, Kazimierz; Smolarek, Leszek

    2013-01-01

    This paper presents an overview of factors causing driver fatigue as described in the literature. Next, a traffic crash database for 2003-2007 is used to identify the causes, circumstances and consequences of accidents caused by driver fatigue on Poland's national roads. The results of the study were used to build a model showing the relationship between the concentration of road accidents and casualties, and the time of day. Finally, the level of relative accident risk at night-time versus daytime is defined. A map shows the risk of death and severe injury on the network of Poland's national roads. The paper suggests to road authorities steps to reduce fatigue-related road accidents in Poland.

  17. Exploring the patient perspective of fatigue in adults with visual impairment: a qualitative study.

    Science.gov (United States)

    Schakel, Wouter; Bode, Christina; van der Aa, Hilde P A; Hulshof, Carel T J; Bosmans, Judith E; van Rens, Gerardus H M B; van Nispen, Ruth M A

    2017-08-03

    Fatigue is an often mentioned symptom by patients with irreversible visual impairment. This study explored the patient perspective of fatigue in visually impaired adults with a focus on symptoms of fatigue, causes, consequences and coping strategies. Two large Dutch low vision multidisciplinary rehabilitation organisations. 16 visually impaired adults with severe symptoms of fatigue selected by purposive sampling. A qualitative study involving semistructured interviews. A total of four first-level codes were top-down predetermined in correspondence with the topics of the research question. Verbatim transcribed interviews were analysed with a combination of a deductive and inductive approach using open and axial coding. Participants often described the symptoms of fatigue as a mental, daily and physical experience. The most often mentioned causes of fatigue were a high cognitive load, the intensity and amount of activities, the high effort necessary to establish visual perception, difficulty with light intensity and negative cognitions. Fatigue had the greatest impact on the ability to carry out social roles and participation, emotional functioning and cognitive functioning. The most common coping strategies were relaxation, external support, socialising and physical exercise and the acceptance of fatigue. Our results indicate that low vision-related fatigue is mainly caused by population specific determinants that seem different from the fatigue experience described in studies with other patient populations. Fatigue may be central to the way patients react, adapt and compensate to the consequences of vision loss. These findings indicate a need for future research aimed at interventions specifically tailored to the unique aspects of fatigue related to vision loss. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  18. Multidimensional fatigue and its correlates in hospitalised advanced cancer patients.

    NARCIS (Netherlands)

    Echteld, M.A.; Passchier, J.; Teunissen, S.; Claessen, S.; Wit, R. de; Rijt, C.C.D. van der

    2007-01-01

    Although fatigue is a multidimensional concept, multidimensional fatigue is rarely investigated in hospitalised cancer patients. We determined the levels and correlates of multidimensional fatigue in 100 advanced cancer patients admitted for symptom control. Fatigue dimensions were general fatigue

  19. Combining Passive Thermography and Acoustic Emission for Large Area Fatigue Damage Growth Assessment of a Composite Structure

    Science.gov (United States)

    Zalameda, Joseph N.; Horne, Michael R.; Madaras, Eric I.; Burke, Eric R.

    2016-01-01

    Passive thermography and acoustic emission data were obtained for improved real time damage detection during fatigue loading. A strong positive correlation was demonstrated between acoustic energy event location and thermal heating, especially if the structure under load was nearing ultimate failure. An image processing routine was developed to map the acoustic emission data onto the thermal imagery. This required removing optical barrel distortion and angular rotation from the thermal data. The acoustic emission data were then mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. This technology provides improved real time inspections of advanced composite structures during fatigue testing.Keywords: Thermal nondestructive evaluation, fatigue damage detection, aerospace composite inspection, acoustic emission, passive thermography

  20. Fatigue crack propagation and cyclic deformation at a crack tip

    Science.gov (United States)

    Kang, T. S.; Liu, H. W.

    1974-01-01

    The fatigue crack propagation relation da/dN = f(R) Delta K squared can be derived with three assumptions: small-scale yielding, material homogeneity, and that crack tip stresses and strains are not strongly affected by plate thickness. The function f(R) is a constant at a given stress ratio, R. The effects of plate thickness and stress ratio on crack tip deformation and fatigue crack growth in 2024-T351 aluminum alloy were studied. High Delta K level in a thin specimen causes crack tip necking. Necking is more pronounced at high stress ratio. Necking causes high maximum strain near a crack tip and fast crack growth rate.

  1. Fatigue, depression and sleep disturbances in Iranian patients with multiple sclerosis.

    Science.gov (United States)

    Ghajarzadeh, Mahsa; Sahraian, Mohammad Ali; Fateh, Rouzbeh; Daneshmand, Ali

    2012-01-01

    Fatigue is one of the most frequent symptoms in patients with multiple sclerosis (MS) and it is difficult to clarify the nature of this symptom and manage it. This study was aimed to evaluate the frequency of fatigue, depression and sleep disturbances in Iranian patients with MS. 100 patients from the outpatient MS clinic of Sina hospital were asked to complete Beck Depression Inventory (BDI), Pittsburg Sleep Quality Index (PSQI), Sleep Disorder Questionnaire (SDQ), Modified Fatigue Impact Scale (MFIS) and Epworth Sleepiness Scale (ESS) questionnaires. Student's t-test, ANOVA, Spearman correlation and Stepwise multiple linear regressions by SPSS version 15.0 were used for data analysis. From participants, 64 had fatigue complaint during day time and 36 did not feel fatigued. BDI, PSQI, MFIS and SDQ scores were significantly higher in fatigued patients than non-fatigued group but there were no statistically significant differences in ESS, EDSS and duration of disease between fatigued and non-fatigued cases. There were significant correlations between MFIS and BDI scores (r=0.49, P=0.01), MFIS and PSQI scores (r=0.399, P=0.01) and MFIS and ESS (r=0.25, P=0.01). This study demonstrates that depression is not the only cause of fatigue in patients with MS and it is also associated with sleep disorders, so this complaint should be carefully evaluated and managed in these patients. © 2012 Tehran University of Medical Sciences. All rights reserved.

  2. Fatigue, Depression and Sleep Disturbances in Iranian Patients with Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Rouzbeh Fateh

    2012-04-01

    Full Text Available Fatigue is one of the most frequent symptoms in patients with multiple sclerosis (MS and it is difficult to clarify the nature of this symptom and manage it. This study was aimed to evaluate the frequency of fatigue, depression and sleep disturbances in Iranian patients with MS. 100 patients from the outpatient MS clinic of Sina hospital were asked to complete Beck Depression Inventory (BDI, Pittsburg Sleep Quality Index (PSQI, Sleep Disorder Questionnaire (SDQ, Modified Fatigue Impact Scale (MFIS and Epworth Sleepiness Scale (ESS questionnaires. Student's t-test, ANOVA, Spearman correlation and Stepwise multiple linear regressions by SPSS version 15.0 were used for data analysis. From participants, 64 had fatigue complaint during day time and 36 did not feel fatigued. BDI, PSQI, MFIS and SDQ scores were significantly higher in fatigued patients than non-fatigued group but there were no statistically significant differences in ESS, EDSS and duration of disease between fatigued and non-fatigued cases. There were significant correlations between MFIS and BDI scores (r=0.49, P=0.01, MFIS and PSQI scores (r=0.399, P=0.01 and MFIS and ESS (r=0.25, P=0.01. This study demonstrates that depression is not the only cause of fatigue in patients with MS and it is also associated with sleep disorders, so this complaint should be carefully evaluated and managed in these patients.

  3. Evaluation of Mechanical Properties and Fatigue Behavior of STS 304L due to Plastic Working

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyun-Bo [Yeungnam Univ., Daegu (Korea, Republic of); Kim, Young-Kyun [KOGAS Research Institute, Seoul (Korea, Republic of); Suh, Chang-Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of)

    2017-07-15

    The purpose of this study is to investigate the influence of the cold reduction rate and an ultrasonic fatigue test (UFT) on the fatigue behaviors of STS 304L. The tensile strength, yield strength, hardness value and fatigue limit in the UFT fatigue test linearly increased as thickness decreased from 1.5 mm to 1.1 mm, as the cold reduction rate of STS 304L increased. As a result of the UFT fatigue test (R = -1) of four specimens, the fatigue limit of the S-N curve formed a knee point in the region of 10{sup 6}, and the 2nd fatigue limit caused by giga cycle fatigue did not appeared. In the case of t = 1.1 mm, the highest fatigue limit was 345 MPa, which was 64.3% higher than the original material (t = 1.5 mm). As a result of the UFT fatigue test of STS 304L, many small surface cracks occurred, grown, coalesced while tearing.

  4. Fatigue tests on aluminium bridges

    NARCIS (Netherlands)

    Maljaars, J.; Soetens, F.; Straalen, IJ.J. van

    2004-01-01

    Traffic bridges are subjected to variable loads and should therefore be checked on fatigue. Especially low weight materials, like aluminium, are sensitive to fatigue, because the variable load is a substantial part of the total load. This paper shows the structural design of an aluminium bridge

  5. Fatigue of Concrete Armour Units

    DEFF Research Database (Denmark)

    Sørensen, N. B.; Burcharth, H. F.; Liu, Z.

    1995-01-01

    In the present article fatigue as a possible reason for failure of Dolosse armour units made of plain concrete is discussed.......In the present article fatigue as a possible reason for failure of Dolosse armour units made of plain concrete is discussed....

  6. Fatigue Criterion for System Design

    Science.gov (United States)

    Zeretsky, E. V.

    1986-01-01

    Report discusses principles of structural-life prediction. Generalized methodology developed for structural life prediction, design, and reliability, based upon fatigue criterion. Approach incorporates computed life of elemental stress volumes of complex machine elements to predict system life. Results of coupon fatigue testing incorporated into analysis, allowing for life prediction and component or structural renewal rates, with reasonable statistical certainty.

  7. Fatigue Properties of Layered Double Hydroxides Modified Asphalt and Its Mixture

    Directory of Open Access Journals (Sweden)

    Xing Liu

    2014-01-01

    Full Text Available This study investigated the influence of layered double hydroxides (LDHs on the fatigue properties of asphalt mixture. In this paper, different aging levels (thin film oven test (TFOT and ultraviolet radiation aging (UV aging for short of bitumen modified with various mass ratios of the LDHs were investigated. The TFOT and UV aging process were used to simulate short-term field thermal-oxidative aging and long-term field light UV aging of bitumen, respectively. The influences of LDHs on the fatigue properties of LDHs were evaluated by dynamic shear rheometer (DSR and indirect tensile fatigue test. Results indicated that the introduction of LDHs could change the fatigue properties of bitumen under a stress control mode. The mixture with modified bitumen showed better fatigue resistance than the mixture with base bitumen. The results illustrated that the LDHs would be alternative modifiers used in the bitumen to improve the lifetime of asphalt pavements.

  8. Increase in Prefrontal Cortical Volume following Cognitive Behavioural Therapy in Patients with Chronic Fatigue Syndrome

    Science.gov (United States)

    de Lange, Floris P.; Koers, Anda; Kalkman, Joke S.; Bleijenberg, Gijs; Hagoort, Peter; van der Meer, Jos W. M.; Toni, Ivan

    2008-01-01

    Chronic fatigue syndrome (CFS) is a disabling disorder, characterized by persistent or relapsing fatigue. Recent studies have detected a decrease in cortical grey matter volume in patients with CFS, but it is unclear whether this cerebral atrophy constitutes a cause or a consequence of the disease. Cognitive behavioural therapy (CBT) is an…

  9. Increase in prefrontal cortical volume following cognitive behavioural therapy in patients with chronic fatigue syndrome

    NARCIS (Netherlands)

    Lange, F.P. de; Koers, A.; Kalkman, J.S.; Bleijenberg, G.; Hagoort, Peter; Meer, J.W.M. van der; Toni, I.

    2008-01-01

    Chronic fatigue syndrome (CFS) is a disabling disorder, characterized by persistent or relapsing fatigue. Recent studies have detected a decrease in cortical grey matter volume in patients with CFS, but it is unclear whether this cerebral atrophy constitutes a cause or a consequence of the disease.

  10. Structural health monitoring in end-of-life prediction for steel bridges subjected to fatigue cracking

    NARCIS (Netherlands)

    Attema, T.; Courage, W.M.G.; Maljaars, J.; Meerveld, H. van; Paulissen, J.H.; Pijpers, R.J.M.; Slobbe, A.T.

    2015-01-01

    This paper presents a monitoring and modelling methodology to assess the current and future conditions of steel bridges subjected to fatigue cracking. Steel bridges are subjected to fatigue cracking as a result of fluctuating stresses caused by the crossing of heavy vehicles. Specifically for

  11. Applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures

    NARCIS (Netherlands)

    Zou, T.; Kaminski, M.L.

    2016-01-01

    In design and operation of floating offshore structures, one has to avoid fatigue failures caused by action of ocean waves. The aim of this paper is to investigate the applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures. The applicability was investigated

  12. Mechanism of fatigue in micron-scale films of polycrystalline silicon for microelectromechanical applications

    Energy Technology Data Exchange (ETDEWEB)

    Muhlstein, C.L.; Stach, E.A.; Ritchie, R.O.

    2001-08-02

    Reported nearly a decade ago, cyclic fatigue failure in silicon thin films has remained a mystery. Silicon does not display the room temperature plasticity or extrinsic toughening mechanisms necessary to cause fatigue in either ductile (e.g., metals) or brittle (e.g., ceramics and ordered mintermetallic) materials.

  13. Effect of muscular fatigue on fractal upper limb coordination dynamics and muscle synergies.

    Science.gov (United States)

    Bueno, Diana R; Lizano, J M; Montano, L

    2015-01-01

    Rehabilitation exercises cause fatigue because tasks are repetitive. Therefore, inevitable human motion performance changes occur during the therapy. Although traditionally fatigue is considered an event that occurs in the musculoskeletal level, this paper studies whether fatigue can be regarded as context that influences lower-dimensional motor control organization and coordination at neural level. Non Negative Factorization Matrix (NNFM) and Detrended Fluctuations Analysis (DFA) are the tools used to analyze the changes in the coordination of motor function when someone is affected by fatigue. The study establishes that synergies remain fairly stable with the onset of fatigue, but the fatigue affects the dynamical coordination understood as a cognitive process. These results have been validated with 9 healthy subjects for three representative exercises for upper limb: biceps, triceps and deltoid.

  14. A Study on the VHCF Fatigue Behaviors of Hydrogen Attacked Inconel 718 Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang-Min [Kyungpook National Univ., DMI Senior Fellow, Daegu (Korea, Republic of); Nahm, Seung-Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Kim, Jun-Hyong; Pyun, Young-Sik [Sun Moon Univ., Chunan (Korea, Republic of)

    2016-07-15

    This study is to investigate the influence of hydrogen attack and UNSM on fatigue behaviors of the Inconel 718 alloy. The decrease of the fatigue life between the untreated and the hydrogen attacked material is 10-20%. The fatigue lives of hydrogen attacked specimen decreased without a fatigue limit, similar to those of nonferrous materials. Due to hydrogen embrittlement, about 80% of the surface cracks were smaller than the average grain size of 13 μm. Many small surface cracks caused by the embrittling effect of hydrogen attack were initiated at the grain boundaries and surface scratches. Cracks were irregularly distributed, grew, and then coalesced through tearing, leading to a reduction of fatigue life. Results revealed that the fatigue lives of UNSM-treated specimens were longer than those of the untreated specimens.

  15. Effects of Yoga in Managing Fatigue in Breast Cancer Patients: A Randomized Controlled Trial.

    Science.gov (United States)

    Vadiraja, H S; Rao, Raghavendra Mohan; Nagarathna, R; Nagendra, H R; Patil, Shekhar; Diwakar, Ravi B; Shashidhara, H P; Gopinath, K S; Ajaikumar, B S

    2017-01-01

    Cancer-related fatigue is widely prevalent in cancer patients and affects quality of life in advanced cancer patients. Fatigue is caused due to both psychologic distress and physiological sequel following cancer progression and its treatment. In this study, we evaluate the effects of yogic intervention in managing fatigue in metastatic breast cancer patients. Ninety-one patients with metastatic breast cancer were randomized to receive integrated yoga program (n = 46) or supportive therapy and education (n = 45) over a 3-month period. Assessments such as perceived stress, fatigue symptom inventory, diurnal salivary cortisol, and natural killer cell counts were carried out before and after intervention. Analysis was done using an intention-to-treat approach. Postmeasures for the above outcomes were assessed using ANCOVA with respective baseline measure as a covariate. The results suggest that yoga reduces perceived stress (P = 0.001), fatigue frequency (P yoga reduces fatigue in advanced breast cancer patients.

  16. Acupuncture for chronic fatigue syndrome and idiopathic chronic fatigue: a multicenter, nonblinded, randomized controlled trial.

    Science.gov (United States)

    Kim, Jung-Eun; Seo, Byung-Kwan; Choi, Jin-Bong; Kim, Hyeong-Jun; Kim, Tae-Hun; Lee, Min-Hee; Kang, Kyung-Won; Kim, Joo-Hee; Shin, Kyung-Min; Lee, Seunghoon; Jung, So-Young; Kim, Ae-Ran; Shin, Mi-Suk; Jung, Hee-Jung; Park, Hyo-Ju; Kim, Sung-Phil; Baek, Yong-Hyeon; Hong, Kwon-Eui; Choi, Sun-Mi

    2015-07-26

    The causes of chronic fatigue syndrome (CFS) and idiopathic chronic fatigue (ICF) are not clearly known, and there are no definitive treatments for them. Therefore, patients with CFS and ICF are interested in Oriental medicine or complementary and alternative medicine. For this reason, the effectiveness of complementary and alternative treatments should be verified. We investigated the effectiveness of two forms of acupuncture added to usual care for CFS and ICF compared to usual care alone. A three-arm parallel, non-blinded, randomized controlled trial was performed in four hospitals. We divided 150 participants into treatment and control groups at the same ratio. The treatment groups (Group A, body acupuncture; Group B, Sa-am acupuncture) received 10 sessions for 4 weeks. The control group (Group C) continued usual care alone. The primary outcome was the Fatigue Severity Scale (FSS) at 5 weeks after randomization. Secondary outcomes were the FSS at 13 weeks and a short form of the Stress Response Inventory (SRI), the Beck Depression Inventory (BDI), the Numeric Rating Scale (NRS), and the EuroQol-5 Dimension (EQ-5D) at 5 and 13 weeks. Group A showed significantly lower FSS scores than Group C at 5 weeks (P = 0.023). SRI scores were significantly lower in the treatment groups than in the control group at 5 (Group A, P = 0.032; B, P fatigue in CFS and ICF patients. Clinical Research Information Service (CRIS) KCT0000508; Registered on 12 August 2012.

  17. Detection of localized fatigue damage in steel by thermography

    Science.gov (United States)

    Medgenberg, Justus; Ummenhofer, Thomas

    2007-04-01

    Fatigue damage of unalloyed steels in the high cycle regime is governed by localized cyclic plastic deformations and subsequent crack initiation. The extent of early microplastic deformations depends on the applied stress level, stress concentration at macroscopic notches, surface treatment, residual stresses etc. The onset of a nonlinear material response can be regarded as an early indicator of fatigue damage. During fatigue loading thermoelastic coupling and thermoplastic dissipation cause characteristic temperature variations in tested specimens which have been assessed by a highly sensitive infrared camera. A specialized data processing method in the time domain has been developed which allows to separate the different contributions to the measured temperature signal. In contrast to other methods - as e.g. measuring the rise of mean temperature during fatigue loading - the proposed methodology is based on measurements during the stabilized temperature regimen and offers very high spatial resolution of localized phenomena. Investigations have been made on mildly notched cylindrical and also on welded specimens. The results confirm the close relation between the local temperature signal and typical fatigue phenomena. The new methodology allows for a much better localization and quantification of effects as cyclic plasticity, crack initiation, crack growth etc. The following paper presents considerations and experimental results of an application of thermography to the local assessment of fatigue damage.

  18. Neural correlates of central inhibition during physical fatigue.

    Directory of Open Access Journals (Sweden)

    Masaaki Tanaka

    Full Text Available Central inhibition plays a pivotal role in determining physical performance during physical fatigue. Classical conditioning of central inhibition is believed to be associated with the pathophysiology of chronic fatigue. We tried to determine whether classical conditioning of central inhibition can really occur and to clarify the neural mechanisms of central inhibition related to classical conditioning during physical fatigue using magnetoencephalography (MEG. Eight right-handed volunteers participated in this study. We used metronome sounds as conditioned stimuli and maximum handgrip trials as unconditioned stimuli to cause central inhibition. Participants underwent MEG recording during imagery of maximum grips of the right hand guided by metronome sounds for 10 min. Thereafter, fatigue-inducing maximum handgrip trials were performed for 10 min; the metronome sounds were started 5 min after the beginning of the handgrip trials. The next day, neural activities during imagery of maximum grips of the right hand guided by metronome sounds were measured for 10 min. Levels of fatigue sensation and sympathetic nerve activity on the second day were significantly higher relative to those of the first day. Equivalent current dipoles (ECDs in the posterior cingulated cortex (PCC, with latencies of approximately 460 ms, were observed in all the participants on the second day, although ECDs were not identified in any of the participants on the first day. We demonstrated that classical conditioning of central inhibition can occur and that the PCC is involved in the neural substrates of central inhibition related to classical conditioning during physical fatigue.

  19. Mechanism of polarization fatigue in BiFeO3.

    Science.gov (United States)

    Zou, Xi; You, Lu; Chen, Weigang; Ding, Hui; Wu, Di; Wu, Tom; Chen, Lang; Wang, Junling

    2012-10-23

    Fatigue in ferroelectric oxides has been a long lasting research topic since the development of ferroelectric memory in the late 1980s. Over the years, different models have been proposed to explain the fatigue phenomena. However, there is still debate on the roles of oxygen vacancies and injected charges. The main difficulty in the study of fatigue in ferroelectric films is that the conventional vertical sandwich structure prevents direct observation of the microscopic evolution through the film thickness during the electric field cycling. To circumvent this problem, we take advantage of the large in-plane polarization of BiFeO(3) and conduct direct domain and local electrical characterizations using a planar device structure. The combination of piezoresponse force microscopy and scanning kelvin probe microscopy allows us to study the local polarization and space charges simultaneously. It is observed that charged domain walls are formed during the electrical cycling, but they do not cause polarization fatigue. After prolonged cycling, injected charges appear at the electrode/film interfaces, where domains are pinned. When the pinned domains grow across the channel, macroscopic fatigue appears. The role of injected charges in polarization fatigue of BiFeO(3) is clearly demonstrated.

  20. Antioxidant and Anti-Fatigue Constituents of Okra.

    Science.gov (United States)

    Xia, Fangbo; Zhong, Yu; Li, Mengqiu; Chang, Qi; Liao, Yonghong; Liu, Xinmin; Pan, Ruile

    2015-10-26

    Okra (Abelmoschus esculentus (L.) Moench), a healthy vegetable, is widely spread in tropical and subtropical areas. Previous studies have proven that okra pods possess anti-fatigue activity, and the aim of this research is to clarify the anti-fatigue constituents. To achieve this, we divided okra pods (OPD) into seeds (OSD) and skins (OSK), and compared the contents of total polysaccharides, total polyphenols, total flavonoids, isoquercitrin, and quercetin-3-O-gentiobiose and the antioxidant activity in vitro and anti-fatigue activity in vivo between OSD and OSK. The contents of total polyphenols and total polysaccharides were 29.5% and 14.8% in OSD and 1.25% and 43.1% in OSK, respectively. Total flavonoids, isoquercitrin and quercetin-3-O-gentiobiose (5.35%, 2.067% and 2.741%, respectively) were only detected in OSD. Antioxidant assays, including 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, ferric reducing antioxidant power (FRAP) and reducing power test, and weight-loaded swimming test showed OSD possessed significant antioxidant and anti-fatigue effects. Moreover, biochemical determination revealed that that anti-fatigue activity of OSD is caused by reducing the levels of blood lactic acid (BLA) and urea nitrogen (BUN), enhancing hepatic glycogen storage and promoting antioxidant ability by lowering malondialdehyde (MDA) level and increasing superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) levels. These results proved okra seeds were the anti-fatigue part of okra pods and polyphenols and flavonoids were active constituents.

  1. Analysis of acoustic emission waveforms from fatigue cracks

    Science.gov (United States)

    Bhuiyan, Md. Yeasin; Bao, Jingjing; Poddar, Banibrata; Giurgiutiu, Victor

    2017-04-01

    Acoustic emission (AE) monitoring technique is a well-known approach in the field of NDE/SHM. AE monitoring from the defect formation and failure in the materials were well studied by the researchers. However, conventional AE monitoring techniques are predominantly based on statistical analysis. In this study we focus on understanding the AE waveforms from the fatigue crack growth using physics based approach. The growth of the fatigue crack causes the acoustic emission in the material that propagates in the structure. One of the main challenges of this approach is to develop the physics based understanding of the AE source itself. The acoustic emission happens not only from the crack growth but also from the interaction of the crack lips during fatigue loading of the materials. As the waveforms are generated from the AE event, they propagate and create local vibration modes along the crack faces. Fatigue experiments were performed to generate the fatigue cracks. Several test specimens were used in the fatigue experiments and corresponding AE waveforms were captured. The AE waveforms were analyzed and distinguished into different groups based on the similar nature on both time domain and frequency domain. The experimental results are explained based on the physical observation of the specimen.

  2. Assessing Fatigue in Late-Midlife

    DEFF Research Database (Denmark)

    Fieo, Robert A; Mortensen, Erik Lykke; Lund, Rikke

    2014-01-01

    Previous methods examining the Multiple Fatigue Inventory-20 (MFI-20) fatigue questionnaire have been limited to classical test theory, for example, factor analytic approaches. We employed modern test theory to further strengthen the construct validity of the MFI-20 fatigue in a sample of healthy...... late-midlife subjects. Five subdimensions of perceived fatigue were examined in n = 7,233 subjects: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Fatigue burden was compared across age groups (aged 48-52 vs. 57-63) and gender. Mokken item response theory...... were observed in the General Fatigue domain. However, the General Fatigue domain did not meet the property of IIO. Two domains (for all groupings) did meet the minimum criteria for the property of IIO: Physical Fatigue and Activity. Introducing model parameters for items served to enhance...

  3. Fatigue - an underestimated symptom in psoriatic arthritis.

    Science.gov (United States)

    Krajewska-Włodarczyk, Magdalena; Owczarczyk-Saczonek, Agnieszka; Placek, Waldemar

    2017-01-01

    The nature of fatigue is very complex and involves physiological, psychological and social phenomena at the same time, and the mechanisms leading to occurrence and severity of fatigue are still poorly understood. The condition of chronic inflammation associated with psoriatic arthritis can be regarded as a potential factor affecting development of fatigue. Only a few studies so far have focused on the occurrence of fatigue in psoriatic arthritis. The problem of chronic fatigue is underestimated in everyday clinical practice. Identification and analysis of subjective fatigue components in each patient can provide an objective basis for optimal fatigue treatment in daily practice. This review presents a definition of chronic fatigue and describes mechanisms that may be associated with development of fatigue, highlighting the role of chronic inflammation, selected fatigue measurement methods and relations of fatigue occurrence with clinical aspects of psoriatic arthritis.

  4. Development of wearable muscle fatigue detection system using capacitance coupling electrodes.

    Science.gov (United States)

    Kobayshi, Takahiro; Okada, Shima; Makikawa, Masaaki; Shiozawa, Naruhiro; Kosaka, Manabu

    2017-07-01

    Bio-information is important to confirm the body condition. Especially, the muscle fatigue is related to injury or decrease of concentration. Therefore, it is required to evaluate muscle fatigue to make subject enjoy sports. In previous study, muscle fatigue is evaluated by using electromyogram (EMG). However, the electrode for EMG measurement is generally used for contact manor. The electrodes are disposable and it might cause the irritation of skin. Therefore, it isn't fitted for measurement of muscle fatigue. We developed wearable muscle fatigue detection system using capacitance coupling electrodes. Developed system isn't caused the irritation by electrodes and can reuse it. We compared the conventional system using disposable electrode system and our system to evaluate performance. We evaluated muscle fatigue from electromyogram before and after futsal. An integrated electromyogram and an intermediate frequency were used for the evaluation of muscle fatigue. As a result, half of subjects showed tendency of muscle fatigue. Therefore, we showed the possibility as muscle fatigue detection system using the capacity coupling electrodes.

  5. Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications

    Science.gov (United States)

    Prevey, Paul S.; Shepard, Michael; Ravindranath, Ravi A.; Gabb, Timothy

    2003-01-01

    Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The X-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: * The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing fatigue benefit of thermal stability at engine temperatures. * An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. * Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. * Corrosion fatigue mitigation with LPB in Carpenter 450 steel. *Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine

  6. IAEA coordinated research program on `harmonization and validation of fast reactor thermomechanical and thermohydraulic codes using experimental data`. 1. Thermohydraulic benchmark analysis on high-cycle thermal fatigue events occurred at French fast breeder reactor Phenix

    Energy Technology Data Exchange (ETDEWEB)

    Muramatsu, Toshiharu [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1997-06-01

    A benchmark exercise on `Tee junction of Liquid Metal Fast Reactor (LMFR) secondary circuit` was proposed by France in the scope of the said Coordinated Research Program (CRP) via International Atomic Energy Agency (IAEA). The physical phenomenon chosen here deals with the mixture of two flows of different temperature. In a LMFR, several areas of the reactor are submitted to this problem. They are often difficult to design, because of the complexity of the phenomena involved. This is one of the major problems of the LMFRs. This problem has been encountered in the Phenix reactor on the secondary loop, where defects in a tee junction zone were detected during a campaign of inspections after an operation of 90,000 hours of the reactor. The present benchmark is based on an industrial problem and deal with thermal striping phenomena. Problems on pipes induced by thermal striping phenomena have been observed in some reactors and experimental facilities coolant circuits. This report presents numerical results on thermohydraulic characteristics of the benchmark problem, carried out using a direct numerical simulation code DINUS-3 and a boundary element code BEMSET. From the analysis with both the codes, it was confirmed that the hot sodium from the small pipe rise into the cold sodium of the main pipe with thermally instabilities. Furthermore, it was indicated that the coolant mixing region including the instabilities agrees approximately with the result by eye inspections. (author)

  7. Muscle fatigue during football match-play.

    Science.gov (United States)

    Reilly, Thomas; Drust, Barry; Clarke, Neil

    2008-01-01

    One of the consequences of sustaining exercise for 90 minutes of football match-play is that the capability of muscle to generate force declines. This impairment is reflected in the decline of work-rate towards the late part of the game. Causes of this phenomenon, which is known as fatigue, and some of its consequences are considered in this article. The stores of muscle glycogen may be considerably reduced by the end of the game, especially if there has not been a tapering of the training load. Thermoregulatory strain may also be encountered, resulting in a fall in physical performance, or there may be a reduced central drive from the nervous system. The decline in muscle strength may increase the predisposition to injury in the lower limbs. Central fatigue may also occur with implications for muscle performance. Strategies to offset fatigue include astute use of substitutions, appropriate nutritional preparation and balancing pre-cooling and warm-up procedures. There is also a role for endurance training and for a pacing strategy that optimizes the expenditure of energy during match-play.

  8. Genioglossus fatigue in obstructive sleep apnea.

    LENUS (Irish Health Repository)

    McSharry, David

    2012-08-15

    Obstructive sleep apnea (OSA) is a prevalent disorder that may cause cardiovascular disease and fatal traffic accidents but the pathophysiology remains incompletely understood. Increased fatigability of the genioglossus (the principal upper airway dilator muscle) might be important in OSA pathophysiology but the existing literature is uncertain. We hypothesized that the genioglossus in OSA subjects would fatigue more than in controls. In 9 OSA subjects and 9 controls during wakefulness we measured maximum voluntary tongue protrusion force (Tpmax). Using surface electromyography arrays we measured the rate of decline in muscle fiber conduction velocity (MFCV) during an isometric fatiguing contraction at 30% Tpmax. The rate of decline in MFCV provides an objective means of quantifying localized muscle fatigue. Linear regression analysis of individual subject data demonstrated a significantly greater decrease in MFCV in OSA subjects compared to control subjects (29.2 ± 20.8% [mean ± SD] versus 11.2 ± 20.8%; p=0.04). These data support increased fatigability of the genioglossus muscle in OSA subjects which may be important in the pathophysiology of OSA.

  9. A thermography-based method for fatigue behavior evaluation of coupling beam damper

    Directory of Open Access Journals (Sweden)

    Zhe Zhang

    2017-04-01

    Full Text Available Under cyclic load, local fatigue damage will occur in the metal damper widely used in the shear wall. This will deteriorate the stiffness of damper and weaken the hysteresis behaviour. The present paper proposed a new and easy method to manufacture kinds of coupling beam dampers. A thermography-based experiment was used to study the energy dissipation and damage accumulation during fatigue process of the metal damper. Based on the temperature variation related to fatigue damage process, the relationship between the plastic deformation and thermal energy dissipation was quantitatively established. Besides, the relationships between the temperature increase to damage accumulation and mechanical load were analyzed systematically.

  10. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial

    NARCIS (Netherlands)

    Prinsen, Hetty; van Dijk, Johannes P.; Zwarts, Machiel J.; Leer, Jan Willem H.; Bleijenberg, Gijs; van Laarhoven, Hanneke W. M.

    2015-01-01

    Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle fatigue. The

  11. Mental Fatigue Affects Visual Selective Attention

    NARCIS (Netherlands)

    Faber, Leon G.; Maurits, Natasha M.; Lorist, Monicque M.

    2012-01-01

    Mental fatigue is a form of fatigue, induced by continuous task performance. Mentally fatigued people often report having a hard time keeping their attention focussed and being easily distracted. In this study, we examined the relation between mental fatigue, as induced by time on task, and

  12. Mechanisms of Fatigue in Everyday Life

    OpenAIRE

    Dörr, Johanna M.; Nater, Urs M.

    2016-01-01

    The aim of this thesis was to find out which factors predict and increase fatigue in everyday life with the aim of shedding light on mechanisms relevant for the chronification of fatigue. We expected stress to (prospectively) predict fatigue. Also, we expected fatigue to (prospectively) predict stress because it diminishes subjective coping abilities. Further, we expected hypoactivity of the Hypothalamic Pituitary Adrenal (HPA) ax...

  13. Equi-biaxial loading effect on austenitic stainless steel fatigue life

    Directory of Open Access Journals (Sweden)

    C. Gourdin

    2016-10-01

    Full Text Available Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equibiaxial tension. Two calibration tests (with strain gauges and image correlation were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to -1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components

  14. Improvement on the Fatigue Performance of 2024-T4 Alloy by Synergistic Coating Technology

    Directory of Open Access Journals (Sweden)

    Xi-Shu Wang

    2014-05-01

    Full Text Available In this paper, rotating bending fatigue tests of 2024-T4 Al alloy with different oxide coatings were carried out. Compared to the uncoated and previously reported oxide coatings of aluminum alloys, the fatigue strength is able to be enhanced by using a novel oxide coating with sealing pore technology. These results indicate that the better the coating surface quality is, the more excellent the fatigue performance under rotating bending fatigue loading is. The improvement on the fatigue performance is mainly because the fatigue crack initiation and the early stage of fatigue crack growth at the coating layer can be delayed after PEO coating with pore sealing. Therefore, it is a so-called synergistic coating technology for various uses, including welding thermal cracks and filling micro-pores. The effects of different oxide coatings on surface hardness, compressive residual stress, morphology and fatigue fracture morphology are discussed. A critical compressive residual stress of about 95–100 MPa is proposed.

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

    Science.gov (United States)

    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

  16. Thermally-related safety issues associated with thermal batteries.

    Energy Technology Data Exchange (ETDEWEB)

    Guidotti, Ronald Armand

    2006-06-01

    Thermal batteries can experience thermal runaway under certain usage conditions. This can lead to safety issues for personnel and cause damage to associated test equipment if the battery thermally self destructs. This report discusses a number of thermal and design related issues that can lead to catastrophic destruction of thermal batteries under certain conditions. Contributing factors are identified and mitigating actions are presented to minimize or prevent undesirable thermal runaway.

  17. Measuring fatigue in people with multiple sclerosis.

    Science.gov (United States)

    Chipchase, S Y; Lincoln, N B; Radford, K A

    2003-07-22

    To compare methods of assessing fatigue. Cross sectional. Community. Forty Multile Sclerosis (MS) patients and 20 healthy controls. Fatigue questionnaires, SDSA dot cancellation test, finger tapping test, TEA Lottery. The MS patients had significantly higher levels of fatigue than the controls on the Task Induced Fatigue Scale, Fatigue Severity Scale and Fatigue Impact Scale. The Task Induced Fatigue Scale completed whilst imagining oneself driving and the Fatigue Assessment Instrument did not differentiate between MS patients and controls. Finger tapping differentiated between MS patients and controls but there was no significant difference between MS patients and controls on visual and auditory concentration tests. A factor analysis indicated that questionnaire measures of fatigue were interrelated but independent of objective test performance. Questionnaire measures can be used to assess fatigue in people with MS. The FSS differentiated MS patients from controls and is relatively short. It was therefore recommended for clinical use.

  18. Development of reduced-variable master curves for estimating tensile stresses of encapsulated solar cells caused by module deflection or thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Cuddihy, E.F.

    1981-10-01

    Complex computer programs are being used by Spectrolab, Inc., to achieve encapsulation engineering optimization of photovoltaic modules. Optimization involves structural adequacy, electrical isolation (safety), maximum optical transmission, and minimum module temperature, at the lowest life-cycle energy cost. A goal of this activity is the generation, where possible, of encapsulation engineering generalities, principles, and design aids (tables or graphs) that would permit a ready, desktop capability of an engineering evaluation of encapsulation options involving materials or designs. The first efforts to generate reduced-variable mater curves for thermal expansion and deflection stress to serve as structural-analysis design aids are reported.

  19. Damage Analysis of CFRP under Impact Fatigue

    Directory of Open Access Journals (Sweden)

    George Tsigkourakos

    2012-01-01

    Full Text Available In recent years carbon fibre reinforced polymers (CFRPs have become some of the most important structural materials in the aerospace industry due to their excellent stiffness and strength to weight ratios. The real-life loading histories of aerospace composite components and structures involve the generation of transient loads that can propagate as cyclic impacts. This phenomenon is known as impact fatigue (IF. Such loads can cause various types of damage in composites, including fibre breakage, transverse matrix cracking, de-bonding between fibres and matrix and delamination, resulting in a reduction of residual stiffness and a loss of functionality.

  20. Climate specific thermomechanical fatigue of flat plate photovoltaic module solder joints

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, Nick; Silverman, Timothy J.; Kurtz, Sarah

    2016-07-01

    FEM simulations of PbSn solder fatigue damage are used to evaluate seven cities that represent a variety of climatic zones. It is shown that the rate of solder fatigue damage is not ranked with the cities' climate designations. For an accurate ranking, the mean maximum daily temperature, daily temperature change and a characteristic of clouding events are all required. A physics-based empirical equation is presented that accurately calculates solder fatigue damage according to these three factors. An FEM comparison of solder damage accumulated through service and thermal cycling demonstrates the number of cycles required for an equivalent exposure. For an equivalent 25-year exposure, the number of thermal cycles (-40 degrees C to 85 degrees C) required ranged from roughly 100 to 630 for the cities examined. It is demonstrated that increasing the maximum cycle temperature may significantly reduce the number of thermal cycles required for an equivalent exposure.

  1. Muscle fatigue: general understanding and treatment

    Science.gov (United States)

    Wan, Jing-jing; Qin, Zhen; Wang, Peng-yuan; Sun, Yang; Liu, Xia

    2017-01-01

    Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments. PMID:28983090

  2. Muscle fatigue: general understanding and treatment

    OpenAIRE

    Wan, Jing-jing; Qin, Zhen; Wang, Peng-yuan; Sun, Yang; Liu, Xia

    2017-01-01

    Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.

  3. Remarkable improvements in the stability and thermal conductivity of graphite/ethylene glycol nanofluids caused by a graphene oxide percolation structure.

    Science.gov (United States)

    Wang, Baogang; Hao, Jingcheng; Li, Hongguang

    2013-04-28

    Versatile efforts have been made to improve the stability of graphite/ethylene glycol (EG) nanofluids. Primitively, non-dispersible graphite nanoparticles were converted to graphite oxide nanoparticles (GONs) by acid treatment. Although GONs could be well dispersed in EG, the GONs/EG nanofluids exhibited limited stability up to less than 1 day. And then, a GO (2 wt%) percolation structure formed in EG was used to anchor and support GONs by common non-covalent interactions including hydrogen bonds, van der Waals forces and π-π conjugation. Transmission electron microscopy observations revealed that a GON-GO hybrid forms in the GON-GO (2 wt%)/EG nanofluids with evenly distributed GONs on the GO sheets, which accounted for the high stability of nanofluids up to at least 4 weeks obtained from stability tests, in sharp contrast to that of the GONs/EG nanofluids. In addition, due to the better dispersed state of GONs induced by the GO percolation structure, thermal conductivity (TC) tests demonstrated that the TC enhancements of the GON-GO (2 wt%)/EG nanofluids were also strengthened compared to that of GONs/EG nanofluids. Excitingly, the GONs-GO (2 wt%)/EG nanofluids presented here exhibited anomalous thermal conductivity enhancements up to 123% at 21 wt% GONs content and were highly stable, which might have potential applications in engineering field and energy systems.

  4. The effect of muscle fatigue and low back pain on lumbar movement variability and complexity.

    Science.gov (United States)

    Bauer, C M; Rast, F M; Ernst, M J; Meichtry, A; Kool, J; Rissanen, S M; Suni, J H; Kankaanpää, M

    2017-04-01

    Changes in movement variability and complexity may reflect an adaptation strategy to fatigue. One unresolved question is whether this adaptation is hampered by the presence of low back pain (LBP). This study investigated if changes in movement variability and complexity after fatigue are influenced by the presence of LBP. It is hypothesised that pain free people and people suffering from LBP differ in their response to fatigue. The effect of an isometric endurance test on lumbar movement was tested in 27 pain free participants and 59 participants suffering from LBP. Movement variability and complexity were quantified with %determinism and sample entropy of lumbar angular displacement and velocity. Generalized linear models were fitted for each outcome. Bayesian estimation of the group-fatigue effect with 95% highest posterior density intervals (95%HPDI) was performed. After fatiguing %determinism decreased and sample entropy increased in the pain free group, compared to the LBP group. The corresponding group-fatigue effects were 3.7 (95%HPDI: 2.3-7.1) and -1.4 (95%HPDI: -2.7 to -0.1). These effects manifested in angular velocity, but not in angular displacement. The effects indicate that pain free participants showed more complex and less predictable lumbar movement with a lower degree of structure in its variability following fatigue while participants suffering from LBP did not. This may be physiological responses to avoid overload of fatigued tissue, increase endurance, or a consequence of reduced movement control caused by fatigue. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Fatigue life prediction in composites

    CSIR Research Space (South Africa)

    Huston, RJ

    1994-01-01

    Full Text Available Because of the relatively large number of possible failure mechanisms in fibre reinforced composite materials, the prediction of fatigue life in a component is not a simple process. Several mathematical and statistical models have been proposed...

  6. Fatigue and Corrosion in Metals

    CERN Document Server

    Milella, Pietro Paolo

    2013-01-01

    This textbook, suitable for students, researchers and engineers, gathers the experience of more than 20 years of teaching fracture mechanics, fatigue and corrosion to professional engineers and running experimental tests and verifications to solve practical problems in engineering applications. As such, it is a comprehensive blend of fundamental knowledge and technical tools to address the issues of fatigue and corrosion. The book initiates with a systematic description of fatigue from a phenomenological point of view, since the early signs of submicroscopic damage in few surface grains and continues describing, step by step, how these precursors develop to become mechanically small cracks and, eventually, macrocracks whose growth is governed by fracture mechanics. But fracture mechanics is also introduced to analyze stress corrosion and corrosion assisted fatigue in a rather advanced fashion. The author dedicates a particular attention to corrosion starting with an electrochemical treatment that mechanical e...

  7. Fatigue in primary Sjogren's syndrome

    NARCIS (Netherlands)

    P.J. Barendregt (Pieternella); M.R. Visser (Mechteld); E.M.A. Smets (Ellen); J.H.M. Tulen (Joke); A.H. van den Meiracker (Anton); F. Boomsma (Frans); H.M. Markusse

    1998-01-01

    textabstractOBJECTIVE: To assess fatigue in relation to depression, blood pressure, and plasma catecholamines in patients with primary Sjogren's syndrome (SS), in comparison with healthy controls and patients with rheumatoid arthritis. METHODS: For the assessment of

  8. Fatigue of Chinese railway employees and its influential factors: Structural equation modelling.

    Science.gov (United States)

    Tsao, Liuxing; Chang, Jing; Ma, Liang

    2017-07-01

    Fatigue is an identifiable and preventable cause of accidents in transport operations. Regarding the railway sector, incident logs and simulation studies show that employee fatigue leads to lack of alertness, impaired performance, and occurrence of incidents. China has one of the largest rail systems in the world, and Chinese railway employees work under high fatigue risks; therefore, it is important to assess their fatigue level and find the major factors leading to fatigue. We designed a questionnaire that uses Multidimensional Fatigue Instrument (MFI-20), NASA-TLX and subjective rating of work overtime feelings to assess employee fatigue. The contribution of each influential factor of fatigue was analysed using structural equation modelling. In total, 297 employees from the rail maintenance department and 227 employees from the locomotive department returned valid responses. The average scores and standard deviations for the five subscales of MFI-20, namely General Fatigue, Physical Fatigue, Reduced Activity, Reduced Motivation, and Mental Fatigue, were 2.9 (0.8), 2.8 (0.8), 2.5 (0.8), 2.5 (0.7), and 2.4 (0.8) among the rail maintenance employees and 3.5 (0.8), 3.5 (0.7), 3.3 (0.7), 3.0 (0.6), and 3.1 (0.7), respectively, among the locomotive employees. The fatigue of the locomotive employees was influenced by feelings related to working overtime (standardized r = 0.22) and workload (standardized r = 0.27). The work overtime control and physical working environment significantly influenced subjective feelings (standardized r = -0.25 and 0.47, respectively), while improper work/rest rhythms and an adverse physical working environment significantly increased the workload (standardized r = 0.48 and 0.33, respectively). Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Relationship between static chemical and cyclic mechanical fatigue in a feldspathic porcelain.

    Science.gov (United States)

    White, S N; Li, Z C; Yu, Z; Kipnis, V

    1997-03-01

    The goal of this study was to determine if static chemical and cyclic mechanical fatigue are independent, or if they interact to produce greater than additive strength loss in a feldspathic porcelain. A blunt indentation technique was used to investigate the response of a feldspathic dental porcelain to cyclic mechanical fatigue and static chemical fatigue. All specimens were fabricated in a dry inert environment and then mechanically fatigued by cyclic loading and strength-tested in dry inert nitrogenous, ambient or wet environments. A series of experiments were performed to evaluate the effects of chemical and mechanical fatigue, and their interaction on strength loss; to determine the effects of, and interaction between, the factors of cyclic fatigue environment and strength test environment on strength; to ascertain if the type of environment during strength testing influenced specimen strength; and to distinguish between chemical damage caused by exposure to moisture alone and stress corrosion damage resulting from the strength testing environment, using a pair of two-way analysis of variance, a single one-way analysis of variance and a t-test (p fatigue and cyclic mechanical fatigue significantly reduced specimen strength, but they did not interact to produce greater than summative effects. It was also learned that chemical fatigue was not detected on initial exposure to moisture and that it occurred to a small extent during mechanical fatigue cycling, and primarily occurred during strength testing through a stress-corrosion phenomenon. Micrographs visually evaluated the effects of mechanical and chemical fatigue on surface contact damage. As both static chemical and cyclic mechanical fatigue influenced porcelain strength, they should both be considered in future evaluations. However, because they largely acted independently, they can be studied separately.

  10. Giardia-specific cellular immune responses in post-giardiasis chronic fatigue syndrome.

    Science.gov (United States)

    Hanevik, Kurt; Kristoffersen, Einar; Mørch, Kristine; Rye, Kristin Paulsen; Sørnes, Steinar; Svärd, Staffan; Bruserud, Øystein; Langeland, Nina

    2017-01-28

    The role of pathogen specific cellular immune responses against the eliciting pathogen in development of post-infectious chronic fatigue syndrome (PI-CFS) is not known and such studies are difficult to perform. The aim of this study was to evaluate specific anti-Giardia cellular immunity in cases that developed CFS after Giardia infection compared to cases that recovered well. Patients reporting chronic fatigue in a questionnaire study three years after a Giardia outbreak were clinically evaluated five years after the outbreak and grouped according to Fukuda criteria for CFS and idiopathic chronic fatigue. Giardia specific immune responses were evaluated in 39 of these patients by proliferation assay, T cell activation and cytokine release analysis. 20 Giardia exposed non-fatigued individuals and 10 healthy unexposed individuals were recruited as controls. Patients were clinically classified into CFS (n = 15), idiopathic chronic fatigue (n = 5), fatigue from other causes (n = 9) and recovered from fatigue (n = 10). There were statistically significant antigen specific differences between these Giardia exposed groups and unexposed controls. However, we did not find differences between the Giardia exposed fatigue classification groups with regard to CD4 T cell activation, proliferation or cytokine levels in 6 days cultured PBMCs. Interestingly, sCD40L was increased in patients with PI-CFS and other persons with fatigue after Giardia infection compared to the non-fatigued group, and correlated well with fatigue levels at the time of sampling. Our data show antigen specific cellular immune responses in the groups previously exposed to Giardia and increased sCD40L in fatigued patients.

  11. Are There Any Natural Remedies That Reduce Chronic Fatigue Associated with Chronic Fatigue Syndrome?

    Science.gov (United States)

    ... natural remedies that reduce chronic fatigue associated with chronic fatigue syndrome? Answers from Brent A. Bauer, M.D. Researchers ... a variety of natural products for effectiveness against chronic fatigue syndrome. Most results have been disappointing. A few remedies — ...

  12. Fatigue, burnout, and chronic fatigue syndrome among employees on sick leave: do attributions make the difference?

    NARCIS (Netherlands)

    Huibers, M.J.H.; Beurskens, A.J.H.M.; Prins, J.B.; Kant, I.J.; Bazelmans, H.M.; Schayck, C.P. van; Knottnerus, J.A.; Bleijenberg, G.

    2003-01-01

    BACKGROUND: Persistent fatigue among employees, burnout, and chronic fatigue syndrome (CFS) are three fatigue conditions that share some characteristics in theory. However, these conditions have not been compared in empirical research, despite conceptual similarities. METHODS: This cross sectional

  13. Fatigue Perceived by Multiple Sclerosis Patients Is Associated With Muscle Fatigue

    NARCIS (Netherlands)

    Steens, Anneke; de Vries, Astrid; Hemmen, Jolien; Heersema, Thea; Heerings, Marco; Maurits, Natasha; Zijdewind, Inge

    Background. Fatigue is a debilitating symptom in multiple sclerosis (MS). Previous studies showed no association between fatigue as perceived by the patient and physiological measures of fatigability. Objective. The authors investigated associations between perceived fatigue and measures of

  14. Fatigue and fracture of fibre metal laminates

    CERN Document Server

    Alderliesten, René

    2017-01-01

    This book contributes to the field of hybrid technology, describing the current state of knowledge concerning the hybrid material concept of laminated metallic and composite sheets for primary aeronautical structural applications. It is the only book to date on fatigue and fracture of fibre metal laminates (FMLs). The first section of the book provides a general background of the FML technology, highlighting the major FML types developed and studied over the past decades in conjunction with an overview of industrial developments based on filed patents. In turn, the second section discusses the mechanical response to quasi-static loading, together with the fracture phenomena during quasi-static and cyclic loading. To consider the durability aspects related to strength justification and certification of primary aircraft structures, the third section discusses thermal aspects related to FMLs and their mechanical response to various environmental and acoustic conditions.

  15. Fatigue and the criminal law.

    Science.gov (United States)

    Jones, Christopher B; Dorrian, Jillian; Rajaratnam, Shanthakumar M W

    2005-01-01

    Fatigue is an increasingly recognised risk factor for transportation accidents. In light of this, there is the question of whether driving whilst fatigued should be a criminal offence. This paper discusses the current legal position, including the problems of voluntary conduct and self awareness. Three models for reform are proposed. The manner in which scientific research can inform legal consideration and future directions for research are discussed.

  16. Biaxial Fatigue Cracking from Notch

    Science.gov (United States)

    2013-03-04

    of the central notch. BIAXIAL FATIGUE TEST The biaxial fatigue test was conducted in a MTS 793.10 Multiaxial Purpose Test-Ware with two pairs...of servo -hydraulic actuators and two pairs of load cells, arranged perpendicular to each other on a horizontal plane in a rigid frame, Figure A-1...TR-2009/12, of 19 Feb 2009. NAWCADPAX/TR-2013/32 15 APPENDIX A FIGURES 1. MTS Machine and Cruciform Specimen 2. Effect of Biaxiality

  17. Supervised exercise reduces cancer-related fatigue: a systematic review

    Directory of Open Access Journals (Sweden)

    José F Meneses-Echávez

    2015-01-01

    Full Text Available Question: Does supervised physical activity reduce cancer-related fatigue? Design: Systematic review with meta-analysis of randomised trials. Participants: People diagnosed with any type of cancer, without restriction to a particular stage of diagnosis or treatment. Intervention: Supervised physical activity interventions (eg, aerobic, resistance and stretching exercise, defined as any planned or structured body movement causing an increase in energy expenditure, designed to maintain or enhance health-related outcomes, and performed with systematic frequency, intensity and duration. Outcome measures: The primary outcome measure was fatigue. Secondary outcomes were physical and functional wellbeing assessed using the Functional Assessment of Cancer Therapy Fatigue Scale, European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire, Piper Fatigue Scale, Schwartz Cancer Fatigue Scale and the Multidimensional Fatigue Inventory. Methodological quality, including risk of bias of the studies, was evaluated using the PEDro Scale. Results: Eleven studies involving 1530 participants were included in the review. The assessment of quality showed a mean score of 6.5 (SD 1.1, indicating a low overall risk of bias. The pooled effect on fatigue, calculated as a standardised mean difference (SMD using a random-effects model, was –1.69 (95% CI –2.99 to –0.39. Beneficial reductions in fatigue were also found with combined aerobic and resistance training with supervision (SMD = –0.41, 95% CI –0.70 to –0.13 and with combined aerobic, resistance and stretching training with supervision (SMD = –0.67, 95% CI –1.17 to –0.17. Conclusion: Supervised physical activity interventions reduce cancer-related fatigue. These findings suggest that combined aerobic and resistance exercise regimens with or without stretching should be included as part of rehabilitation programs for people who have been diagnosed with cancer

  18. Meta-Analysis of Three Different Types of Fatigue Management Interventions for People with Multiple Sclerosis: Exercise, Education, and Medication

    Directory of Open Access Journals (Sweden)

    Miho Asano

    2014-01-01

    Full Text Available Fatigue is a common symptom of multiple sclerosis (MS with negative impacts extending from general functioning to quality of life. Both the cause and consequences of MS fatigue are considered multidimensional and necessitate multidisciplinary treatment for successful symptom management. Clinical practice guidelines suggest medication and rehabilitation for managing fatigue. This review summarized available research literature about three types of fatigue management interventions (exercise, education, and medication to provide comprehensive perspective on treatment options and facilitate a comparison of their effectiveness. We researched PubMed, Embase, and CINAHL (August 2013. Search terms included multiple sclerosis, fatigue, energy conservation, Amantadine, Modafinil, and randomized controlled trial. The search identified 230 citations. After the full-text review, 18 rehabilitation and 7 pharmacological trials targeting fatigue were selected. Rehabilitation interventions appeared to have stronger and more significant effects on reducing the impact or severity of patient-reported fatigue compared to medication. Pharmacological agents, including fatigue medication, are important but often do not enable people with MS to cope with their existing disabilities. MS fatigue affects various components of one’s health and wellbeing. People with MS experiencing fatigue and their healthcare providers should consider a full spectrum of effective fatigue management interventions, from exercise to educational strategies in conjunction with medication.

  19. Poststroke fatigue: the patient perspective.

    Science.gov (United States)

    Young, C A; Mills, R J; Gibbons, C; Thornton, E W

    2013-01-01

    Fatigue is reported as a prevalent symptom post stroke. The purpose of this study is to explore the patent perspective of this symptom, how it is experienced, and its subjective impact on the patient. The qualitative procedure of interpretative phenomenological analysis (IPA) was used to analyze the narratives of 10 subjects with previous stroke, who each undertook a single, semi-structured interview. Fatigue was a salient symptom for all the patients. Six main themes were identified. Tiredness/sleep was recognized in all the narratives, and themes of restriction, frustration, and determination/coping reflected varying degrees of physical, cognitive, and psychological dimensions to fatigue. Depression/motivation was also identified, reflecting low mood and helplessness. The remaining theme support indicated a social dimension, with patients recognizing the need for professional and familial support. Further subthemes were identified, and the thematic descriptions of the physical and psychosocial aspects indicated the complexity of fatigue and unique patient profiles. A holistic overview of each narrative furthered an understanding of the dynamic interrelationships between these aspects and their impact on the patient. There were prevalent patterns, but these were different for each patient. A better understanding of the varied dimensions or themes elaborated for poststroke fatigue, and their interrelationships, should help in mitigating its impact. The analysis cautions against giving any simplistic and unitary advice to patients about dealing with fatigue.

  20. Improving fatigue performance of rail thermite welds

    Directory of Open Access Journals (Sweden)

    Winiar L.

    2010-06-01

    Full Text Available Rail transport development offers economic and ecological interests. Nevertheless, it requires heavy investments in rolling material and infrastructure. To be competitive, this transportation means must rely on safe and reliable infrastructure, which requires optimization of all implemented techniques and structure. Rail thermite (or aluminothermic welding is widely used within the railway industry for in-track welding during re-rail and defect replacement. The process provides numerous advantages against other welding technology commonly used. Obviously, future demands on train traffic are heavier axle loads, higher train speeds and increased traffic density. Thus, a new enhanced weld should be developed to prevent accidents due to fracture of welds and to lower maintenance costs. In order to improve such assembly process, a detailed metallurgical study coupled to a thermomechanical modelling of the phenomena involved in the thermite welding process is carried out. Obtained data enables us to develop a new improved thermite weld (type A. This joint is made by modifying the routinely specified procedure (type B used in a railway rail by a standard gap alumino-thermic weld. Joints of type A and B are tested and compared. Based on experimental temperature measurements, a finite element analysis is used to calculate the thermal residual stresses induced. In the vicinity of the weld, the residual stress patterns depend on the thermal conditions during welding as it also shown by litterature [1, 2]. In parallel, X-Ray diffraction has been used to map the residual stress field that is generated in welded rail of types A and B. Their effect on fatigue crack growth in rail welds is studied. An experimental study based on fatigue tests of rails welded by conventional and improved processes adjudicates on the new advances and results will be shown.

  1. Bone fatigue and its implications for injuries in racehorses.

    Science.gov (United States)

    Martig, S; Chen, W; Lee, P V S; Whitton, R C

    2014-07-01

    Musculoskeletal injuries are a common cause of lost training days and wastage in racehorses. Many bone injuries are a consequence of repeated high loading during fast work, resulting in chronic damage accumulation and material fatigue of bone. The highest joint loads occur in the fetlock, which is also the most common site of subchondral bone injury in racehorses. Microcracks in the subchondral bone at sites where intra-articular fractures and palmar osteochondral disease occur are similar to the fatigue damage detected experimentally after repeated loading of bone. Fatigue is a process that has undergone much study in material science in order to avoid catastrophic failure of engineering structures. The term 'fatigue life' refers to the numbers of cycles of loading that can be sustained before failure occurs. Fatigue life decreases exponentially with increasing load. This is important in horses as loads within the limb increase with increasing speed. Bone adapts to increased loading by modelling to maintain the strains within the bone at a safe level. Bone also repairs fatigued matrix through remodelling. Fatigue injuries develop when microdamage accumulates faster than remodelling can repair. Remodelling of the equine metacarpus is reduced during race training and accelerated during rest periods. The first phase of remodelling is bone resorption, which weakens the bone through increased porosity. A bone that is porous following a rest period may fail earlier than a fully adapted bone. Maximising bone adaptation is an important part of training young racehorses. However, even well-adapted bones accumulate microdamage and require ongoing remodelling. If remodelling inhibition at the extremes of training is unavoidable then the duration of exposure to high-speed work needs to be limited and appropriate rest periods instituted. Further research is warranted to elucidate the effect of fast-speed work and rest on bone damage accumulation and repair. © 2014 EVJ Ltd.

  2. A new hypothesis of chronic fatigue syndrome: co-conditioning theory.

    Science.gov (United States)

    Tanaka, Masaaki; Watanabe, Yasuyoshi

    2010-08-01

    Chronic fatigue syndrome is an illness characterized by a profound, disabling, and unexplained sensation of fatigue lasting at least 6 months, which severely impairs daily functioning and is accompanied by a combination of non-specific symptoms. Many potential causes of chronic fatigue syndrome have been investigated, including viral infections, immune dysfunctions, abnormal neuroendocrine responses, central nervous system abnormalities, autonomic dysfunctions, impaired exercise capacities, sleep disruptions, genetic backgrounds, psychiatric abnormalities, personality, and abnormal psychological processes. However, no etiology, specific physical signs or laboratory test abnormalities have been found. It is essential to establish a conceptual theory of chronic fatigue syndrome that can explain its pathophysiology in order to identify the clinical entity and to develop effective treatment methods. In this article, a new conceptual hypothesis about the pathophysiology of chronic fatigue syndrome, the co-conditioning theory, is presented: after repetitive overwork and/or stress, alarm signal to rest and fatigue sensation may cause in response to an unconditioned stimulus (impaired homeostasis and function) that has been paired with a conditioned stimulus (overwork and/or stress). In the future, a new treatment strategy for patients with chronic fatigue syndrome, re-co-conditioning therapy, may be developed on the basis of the co-conditioning theory. In addition, this theory will likely contribute to a better understanding of the pathophysiology of chronic fatigue syndrome. Copyright 2010 Elsevier Ltd. All rights reserved.

  3. Biaxial fatigue of metals the present understanding

    CERN Document Server

    Schijve, Jaap

    2016-01-01

    Problems of fatigue under multiaxial fatigue loads have been addressed in a very large number of research publications. The present publication is primarily a survey of biaxial fatigue under constant amplitude loading on metal specimens. It starts with the physical understanding of the fatigue phenomenon under biaxial fatigue loads. Various types of proportional and non-proportional biaxial fatigue loads and biaxial stress distributions in a material are specified. Attention is paid to the fatigue limit, crack nucleation, initial micro crack growth and subsequent macro-crack in different modes of crack growth. The interference between the upper and lower surfaces of a fatigue crack is discussed. Possibilities for predictions of biaxial fatigue properties are analysed with reference to the similarity concept. The significance of the present understanding for structural design problems is considered. The book is completed with a summary of major observations.

  4. Piezomagnetism and fatigue

    Science.gov (United States)

    Erber, T.; Guralnick, S. A.; Desai, R. D.; Kwok, W.

    1997-10-01

    Piezomagnetism refers to a change in the intrinsic magnetization of a material subjected to mechanical actions such as tension or compression. In a ferromagnet such as a mild steel these effects are easily measured: typically a stress of 0022-3727/30/20/008/img6 or 140 MPa induces a magnetic moment of the order of 0022-3727/30/20/008/img7 emu or 0022-3727/30/20/008/img8, resulting in flux densities in the range 10 mG or 0022-3727/30/20/008/img9T in the vicinity of the specimen. Since piezomagnetic effects are due to interactions between the mechanical and magnetic mesostructure of materials microplastic processes that alter the arrangement of the ferromagnetic domain structure affect the intensity of the associated magnetic fields. The progressive degradation of such materials under cyclic loading can therefore be tracked by following the evolution of the piezomagnetic field. Specifically, if the measurements are displayed as loci in a three-dimensional stress 0022-3727/30/20/008/img10 - strain 0022-3727/30/20/008/img11 - field (B) space, the approach to fatigue failure is paralleled by a series of conspicuous geometric transformations of these curves. Complementary information also appears in continuous-time records of B(t): these magnetograms clearly show the abrupt incidence of `infarcts' (microcracks) and the cumulation of phase shifts as the material degrades.

  5. Fatigue, General Health, and Ischemic Heart Disease in Older Adults

    DEFF Research Database (Denmark)

    Ekmann, Anette; Petersen, Inge; Mänty, Minna Regina

    2013-01-01

    Backgrounds.Fatigue has been shown to predict ischemic heart disease (IHD) and mortality in nonsmoking middle-aged men free of cardiovascular disease. The aim of this study was to investigate the predictive value of fatigue for IHD and general health in nondisabled individuals free...... of cardiovascular disease and older than 70 years. METHODS: The study population was drawn from The Longitudinal Study of Aging Danish Twins. In total, 1,696 participants were followed up for 2-10 years by questionnaires and 10-16 years through registries. Kaplan Meier, Cox Proportional Hazard and logistic......-related diagnoses, no use of heart medication, sustained good mobility, and participation at follow-up. IHD was defined as first hospitalization due to IHD (ICD10: I20-I25) or death due to IHD as primary cause. RESULTS: Participants without fatigue had higher chances of a sustained good general health at 2 (odds...

  6. Assessment of fatigue in cancer patients.

    Science.gov (United States)

    Jacobsen, Paul B

    2004-01-01

    Increased recognition of the problem of fatigue in cancer patients can be attributed, in part, to the development of measures that have provided researchers with the tools necessary for quantifying and characterizing fatigue and exploring its etiology and treatment. Although a consensus regarding the definition of fatigue is lacking, there is general agreement that it is a subjective and multidimensional phenomenon whose assessment requires the use of self-report methods. Consistent with this view, several multidimensional measures of fatigue have been developed and validated for use with cancer patients. These measures differ considerably in their format and content and, as with the definition of fatigue, there is no consensus at the present time regarding the dimensional structure of fatigue. In addition to measuring fatigue on a continuum along one or more dimensions, it may also be possible to assess a clinical syndrome of cancer-related fatigue. Criteria for assessing fatigue in this manner have been proposed and are currently undergoing evaluation. Despite the progress that has been made, there are several important unresolved issues in the assessment of fatigue in cancer patients. These include how to distinguish fatigue from depression, how to use self-reports of fatigue in clinical decision-making, how to capture temporal changes in fatigue, and how best to address the continuing lack of consensus regarding the conceptualization and measurement of fatigue.

  7. Influence of dental restorations and mastication loadings on dentine fatigue behaviour: Image-based modelling approach.

    Science.gov (United States)

    Vukicevic, Arso M; Zelic, Ksenija; Jovicic, Gordana; Djuric, Marija; Filipovic, Nenad

    2015-05-01

    The aim of this study was to use Finite Element Analysis (FEA) to estimate the influence of various mastication loads and different tooth treatments (composite restoration and endodontic treatment) on dentine fatigue. The analysis of fatigue behaviour of human dentine in intact and composite restored teeth with root-canal-treatment using FEA and fatigue theory was performed. Dentine fatigue behaviour was analysed in three virtual models: intact, composite-restored and endodontically-treated tooth. Volumetric change during the polymerization of composite was modelled by thermal expansion in a heat transfer analysis. Low and high shrinkage stresses were obtained by varying the linear shrinkage of composite. Mastication forces were applied occlusally with the load of 100, 150 and 200N. Assuming one million cycles, Fatigue Failure Index (FFI) was determined using Goodman's criterion while residual fatigue lifetime assessment was performed using Paris-power law. The analysis of the Goodman diagram gave both maximal allowed crack size and maximal number of cycles for the given stress ratio. The size of cracks was measured on virtual models. For the given conditions, fatigue-failure is not likely to happen neither in the intact tooth nor in treated teeth with low shrinkage stress. In the cases of high shrinkage stress, crack length was much larger than the maximal allowed crack and failure occurred with 150 and 200N loads. The maximal allowed crack size was slightly lower in the tooth with root canal treatment which induced somewhat higher FFI than in the case of tooth with only composite restoration. Main factors that lead to dentine fatigue are levels of occlusal load and polymerization stress. However, root canal treatment has small influence on dentine fatigue. The methodology proposed in this study provides a new insight into the fatigue behaviour of teeth after dental treatments. Furthermore, it estimates maximal allowed crack size and maximal number of cycles for a

  8. Early Life Stress and Inflammatory Mechanisms of Fatigue in the Coronary Artery Risk Development in Young Adults (CARDIA) Study

    OpenAIRE

    Cho, Hyong Jin; Bower, Julienne E.; Kiefe, Catarina I.; Seeman, Teresa E.; Irwin, Michael R.

    2012-01-01

    Fatigue is highly prevalent and causes serious disruption in quality of life. Although cross-sectional studies suggest childhood adversity is associated with adulthood fatigue, longitudinal evidence of this relationship and its specific biological mechanisms have not been established. This longitudinal study examined the association between early life stress and adulthood fatigue and tested whether this association was mediated by low-grade systemic inflammation as indexed by circulating C-re...

  9. Normalizing effect on fatigue crack propagation at the heat-affected zone of AISI 4140 steel shielded metal arc weldings

    OpenAIRE

    B. Vargas-Arista; J. Teran-Guillen; Solis, J.; García-Cerecero,G.; Martínez-Madrid,M.

    2013-01-01

    The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ) of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughne...

  10. Improving Fatigue Performance of GFRP Composite Using Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Moneeb Genedy

    2015-01-01

    Full Text Available Glass fiber reinforced polymers (GFRP have become a preferable material for reinforcing or strengthening reinforced concrete structures due to their corrosion resistance, high strength to weight ratio, and relatively low cost compared with carbon fiber reinforced polymers (CFRP. However, the limited fatigue life of GFRP hinders their use in infrastructure applications. For instance, the low fatigue life of GFRP caused design codes to impose stringent stress limits on GFRP that rendered their use non-economic under significant cyclic loads in bridges. In this paper, we demonstrate that the fatigue life of GFRP can be significantly improved by an order of magnitude by incorporating Multi-Wall Carbon Nanotubes (MWCNTs during GFRP fabrication. GFRP coupons were fabricated and tested under static tension and cyclic tension with mean fatigue stress equal to 40% of the GFRP tensile strength. Microstructural investigations using scanning electron microscopy (SEM and Fourier Transform Infrared (FTIR spectroscopy were used for further investigation of the effect of MWCNTs on the GFRP composite. The experimental results show the 0.5 wt% and the 1.0 wt% MWCNTs were able to improve the fatigue life of GFRP by 1143% and 986%, respectively, compared with neat GFRP.

  11. Psychiatric caregiver stress: clinical implications of compassion fatigue.

    Science.gov (United States)

    Franza, Francesco; Del Buono, Gianfranco; Pellegrino, Ferdinando

    2015-09-01

    The capacity to work productively is a key component of health and emotional well-being. People who work in health care can be exposed to the fatigue of care. Compassion fatigue has been described as an occupational hazard specific to clinical work related severe emotional distress. In our study, we have evaluated compassion fatigue in a mental health group (47 psychiatric staff) and its relationship with inpatients (237 inpatients) affected by some psychiatric disorders. At baseline, the more significant data indicate a high percentage of Job Burnout and Compassion Fatigue in psychiatric nurses (respectively, 39.28%, 28.57%). Significant Compassion Fatigue percentage is present also in psychologist group (36.36%). Finally, in psychiatrists, the exposure to patients increased vicarious trauma (28.57%), but not job burnout. After a year of participation in Balint Groups, the psychiatric staff presented an overall reduction in total mean score in any administered scale (CBI: pBurnout: pfatigue causes concern among mental health professionals, and Balint Groups may represent a therapeutic strategy to help health professionals to face difficulties in challenging work environments.

  12. [Pharmacological treatment of patients with chronic fatigue syndrome].

    Science.gov (United States)

    Glazachev, O S; Dudnik, Е N; Zagaynaya, E E

    2017-01-01

    To evaluate the efficacy and safety of human placenta extract - laennec infusions in the treatment of patients with confirmed diagnosis of 'Chronic fatigue syndrome' (CFS). The study included 38 patients with CFS, randomized into 2 groups: patients of the experimental group (EG, n=24) were treated with 10 intravenous laennec infusions, 4 ml each, 2 times/week, for 5 weeks. The control group (CG) consisted of 14 patients. Treatment efficacy evaluated by the severity of chronic fatigue ('The degree of chronic fatigue' questionnaire), state anxiety, depression and anger (Spilberger test) and quality of life (SF-36v2), exercise tolerance (cardiopulmonary exercise test with gas analysis), blood parameters were assessed before, after, and 5 weeks of follow-up. The EG patients showed a significant reduction in the index of chronic fatigue, which was accompanied by the significant decrease in state depression, anxiety, improvements in subjective assessment of quality of life, as well as a significant increase in physical performance indices (maximal oxygen consumption, anaerobic threshold, load time to failure, normalization of the lipid 'profile' immediately after course of infusions and in 5 weeks follow-up). No changes in chronic fatigue index and other recorded indicators were identified in CG. Laennec did not cause side effects, was well tolerated by all patients.

  13. Investigation of Cyclic Deformation and Fatigue of Polycrystalline Cu under Pure Compression Cyclic Loading Conditions

    Science.gov (United States)

    Hsu, Tzu-Yin Jean

    , it was suggested that the plastic strain accommodated within the samples was not in any major way related to dislocation activities. Instead, the cyclic stress-strain response for pure compression fatigue was correlated with surface morphology evolution. In other words, cyclic creep under pure compression fatigue was caused mainly by the mechanism of grain boundary extrusion. Such phenomenon was found to eventually lead to crack nucleation. Furthermore, from symmetrical fatigue testing, it was noted that depending on the polarity of the loading spectrum in the first half cycle, i.e. compression or tension, either regular Bauschinger effect or anti-Bauschinger effect was observed, respectively. Such observations further elucidate the role of compression loading spectrum versus tension loading in fatigue.

  14. Fatigue and somatic symptoms

    National Research Council Canada - National Science Library

    Viner, Russell; Christie, Deborah

    2005-01-01

    ... appendicitis, pelvic inflammatory disease, gastro-oesophageal reflux, peptic ulcer disease, mittelschmerz Rare causes-Inflammatory bowel disease, renal calculi, ovarian cyst, biliary calculi, sickle cell...

  15. Vibration fatigue using modal decomposition

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2018-01-01

    Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.

  16. Probabilistic multiscale models and measurements of self-heating under multiaxial high cycle fatigue

    Science.gov (United States)

    Poncelet, M.; Doudard, C.; Calloch, S.; Weber, B.; Hild, F.

    2010-04-01

    Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as "self-heating tests." This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multiaxiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of microplasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach.

  17. Fatigue analysis of aluminum drill pipes

    Directory of Open Access Journals (Sweden)

    João Carlos Ribeiro Plácido

    2005-12-01

    Full Text Available An experimental program was performed to investigate the fundamental fatigue mechanisms of aluminum drill pipes. Initially, the fatigue properties were determined through small-scale tests performed in an optic-mechanical fatigue apparatus. Additionally, full-scale fatigue tests were carried out with three aluminum drill pipe specimens under combined loading of cyclic bending and constant axial tension. Finally, a finite element model was developed to simulate the stress field along the aluminum drill pipe during the fatigue tests and to estimate the stress concentration factors inside the tool joints. By this way, it was possible to estimate the stress values in regions not monitored during the fatigue tests.

  18. An analysis of factors causing the occurrence of off-design thermally induced force effects in the zone of weld joint no. 111-1 in a PGV-1000M steam generator and recommendations on excluding them

    Science.gov (United States)

    Bakirov, M. B.; Levchuk, V. I.; Povarov, V. P.; Gromov, A. F.

    2014-08-01

    Inadmissible operational flaws occurring in the critical zones of heat-transfer and mechanical equipment are commonly revealed in all nuclear power plant units both in Russia and abroad. The number of such flaws will only grow in the future because the majority of nuclear power plants have been in operation for a time that is either close to or even exceeds the assigned service life. In this connection, establishing cause-and-effect relations with regard to accelerated incipience and growth of flaws, working out compensating measures aimed at reducing operational damageability, and setting up monitoring of equipment integrity degradation of during operation are becoming the matters of utmost importance. There is a need to introduce new approaches to comprehensive diagnostics of the technical state of important nuclear power plant equipment, including continuous monitoring of its operational damageability and the extent of its loading in the most critical zones. Starting from 2011, such a monitoring system has successfully been used for the Novovoronezh NPP Unit 5 in the zone of weld joint no. 111-1 of steam generator no. 4. Based on the results from operation of this system in 2011-2013, unsteady thermally induced force effects (periodic thermal shocks and temperature abnormalities) were reveled, which had not been considered in the design, and which have an essential influence on the operational loading of this part. Based on an analysis of cause-and-effect relations pertinent to temperature abnormalities connected with technological operations, a set of measures aimed at reducing the thermally induced force loads exerted on pipeline sections was developed, which includes corrections to the process regulations for safe operation and to the operating manuals (involving changes in the algorithms for manipulating with the stop and control valves in the steam generator blowdown system).

  19. A qualitative exploration of physical, mental and ocular fatigue in patients with primary Sjögren's Syndrome.

    Directory of Open Access Journals (Sweden)

    Rebecca J Stack

    Full Text Available Primary Sjögren's Syndrome (pSS affects exocrine glands such as those producing the tear film, leading to dry and painful eyes, but is also associated with fatigue. The experience of fatigue in pSS, and its relationship with sicca symptoms, is poorly understood.Twenty people diagnosed with pSS were recruited to participate in a semi-structured qualitative interview about their symptoms experience. Interviews were audio-recorded, transcribed verbatim and analysed using thematic analysis.People with pSS described physical tiredness, mental fatigue and ocular fatigue. Mental fatigue was characterised by difficulties in attention, particularly, the ability to follow conversations and short-term memory problems. Participants linked their experience of fatigue to feeling of depression, frustration, irritation and anxiety, and therefore, fatigue was suggested to have had a large impact on their psychological well-being. People with pSS also described a range of ocular symptoms including pain, dryness, and itching, which were compounded by fatigue. For some, eye fatigue was pervasive, and daily activities involving the eyes such as reading, using the computer and driving were impaired. In some cases, the level of ocular discomfort was so severe it prevented sleep, which in turn impacted on general fatigue levels.People with pSS experience fatigue in a range of ways; physical, mental and ocular fatigue were described. Fatigue was suggested to exacerbate other ocular symptoms, posed serious physical limitations and caused psychological distress. Further research into the nature of fatigue and ocular symptoms in pSS is required.

  20. A survey of the prevalence of fatigue, its precursors and individual coping mechanisms among U.S. manufacturing workers.

    Science.gov (United States)

    Lu, Lin; Megahed, Fadel M; Sesek, Richard F; Cavuoto, Lora A

    2017-11-01

    Advanced manufacturing has resulted in significant changes on the shop-floor, influencing work demands and the working environment. The corresponding safety-related effects, including fatigue, have not been captured on an industry-wide scale. This paper presents results of a survey of U.S. manufacturing workers for the: prevalence of fatigue, its root causes and significant factors, and adopted individual fatigue coping methods. The responses from 451 manufacturing employees were analyzed using descriptive data analysis, bivariate analysis and Market Basket Analysis. 57.9% of respondents indicated that they were somewhat fatigued during the past week. They reported the ankles/feet, lower back and eyes were frequently affected body parts and a lack of sleep, work stress and shift schedule were top selected root causes for fatigue. In order to respond to fatigue when it is present, respondents reported coping by drinking caffeinated drinks, stretching/doing exercises and talking with coworkers. Frequent combinations of fatigue causes and individual coping methods were identified. These results may inform the design of fatigue monitoring and mitigation strategies and future research related to fatigue development. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Fatigue technology assessment and strategies for fatigue avoidance in marine structures. Appendices

    Science.gov (United States)

    Capanoglu, Cuneyt C.

    This report provides an up-to-date assessment of fatigue technology, directed specifically toward the marine industry. A comprehensive overview of fatigue analysis and design, a global review of fatigue including rules and regulations and current practices, and a fatigue analysis and design criteria are provided as a general guideline to fatigue assessment. A detailed discussion of all fatigue parameters is grouped under three analysis blocks: fatigue stress model, covering environmental forces, structure response and loading, stress response amplitude operations (RAO's) and hot-spot stresses; fatigue stress history model covering long-term distribution of environmental loading; and fatigue resistance of structures and damage assessment methodologies. The analyses and design parameters that affect fatigue assessment are discussed together with uncertainties and research gaps, to provide a basis for developing strategies for fatigue avoidance. Additional in-depth discussions of wave environment, stress concentration factors, etc. are presented in the appendixes. Assessment of fatigue technology, fatigue stress models, fatigue stress history models, fatigue resistance, fatigue parameters, and fatigue avoidance strategies.

  2. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial.

    Science.gov (United States)

    Prinsen, Hetty; van Dijk, Johannes P; Zwarts, Machiel J; Leer, Jan Willem H; Bleijenberg, Gijs; van Laarhoven, Hanneke W M

    2015-02-01

    Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle fatigue. The aims of this study were to examine whether central and peripheral muscle fatigue differ between fatigued and non-fatigued cancer survivors and to examine the effect of cognitive behavioral therapy (CBT) on peripheral and central muscle fatigue of fatigued cancer survivors in a randomized controlled trial. Sixteen fatigued patients in the intervention group (CBT) and eight fatigued patients in the waiting list group were successfully assessed at baseline and six months later. Baseline measurements of 20 fatigued patients were compared with 20 non-fatigued patients. A twitch interpolation technique and surface electromyography were applied, respectively, during sustained contraction of the biceps brachii muscle. Muscle fiber conduction velocity (MFCV) and central activation failure (CAF) were not significantly different between fatigued and non-fatigued patients. Change scores of MFCV and CAF were not significantly different between patients in the CBT and waiting list groups. Patients in the CBT group reported a significantly larger decrease in fatigue scores than patients in the waiting list group. Postcancer fatigue is neither characterized by abnormally high central muscle fatigue nor by low peripheral muscle fatigue. These findings suggest a difference in the underlying physiological mechanism of postcancer fatigue vs. other fatigue syndromes. Copyright © 2015 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

  3. A Novel Method for the Prediction of Critical Inclusion Size Leading to Fatigue Failure

    Science.gov (United States)

    Saberifar, S.; Mashreghi, A. R.

    2012-06-01

    The fatigue behavior of two commercial 30MnVS6 steels with similar microstructure and mechanical properties containing inclusions of different sizes were studied in the 107 cycles fatigue regime. The scanning electron microscopy (SEM) investigations of the fracture surfaces revealed that the nonmetallic inclusions are the main sources of fatigue crack initiation. Calculated according to the Murakami's model, the stress intensity factors were found to be suitable for the assessment of fatigue behavior. In this article, a new method is proposed for the prediction of the critical inclusion size, using Murakami's model. According to this method, a critical stress intensity factor was determined for the estimation of the critical inclusion size causing the fatigue failure.

  4. [Fatigue-related risk: what are the consequences for professionals and health-care organizations?].

    Science.gov (United States)

    Ventrucci, C; Zangheri, L; Fersini, F; Gnucci, V; Ingravallo, F

    2012-01-01

    Many studies have investigated the influence of fatigue on healthcare professionals' safety and clinical performances, showing associations between prolonged work shifts, sleep deprivation and both injuries and errors. Even in the absence of conclusive evidence, after the death of a girl under the care of two fatigued residents, New York State promulgated in 1989 rules to cap residents' duty hours, afterwards adopted by the Accrediting Council for Graduate Medical Education. Italian data on fatigue-related medical errors are still lacking, and no legal cases have raised public awareness of this topic. The authors explored medical-legal issues potentially arising from cases of fatigue-related errors, and proposed two interventions from a risk management perspective: 1. review of events reported through the incident reporting system in which at least one contributing factor was fatigue-related, and 2: root cause analysis of events and accidents reported during night shifts.

  5. An Investigation of the Combined Effect of Stress, Fatigue and Workload on Human Performance: Position Paper

    Science.gov (United States)

    Mock, Jessica

    2005-01-01

    Stress, fatigue, and workload affect worker performance. NSF reported that 61% of respondents state losing concentration at work while 79% occasionally or frequently made errors as a result of being fatigued. Shift work, altered work schedules, long hours of continuous wakefulness, and sleep loss can create sleep and circadian disruptions that degrade waking fundions causing stress and fatigue. Review of the literature has proven void of information that links the combined effects of fatigue, stress, and workload to human performance. This paper will address which occupational factors within stress, fatigue, and workload were identified as occupational contributors to performance changes. The results of this research will be apglied to underlying models and algorithms that will help predict performance changes in control room operators.

  6. Corrosion fatigue of magnesium alloys in oil

    Energy Technology Data Exchange (ETDEWEB)

    Eliezer, A.; Haddad, J. [Sami Shamoon College of Engineering, Corrosion Research Center, P.O.B. 45, Beer-Sheva 84100 (Israel); Medlinsky, O. [N.Z.M-Israel Chevron Texaco Agency (Israel)

    2004-07-01

    has a high ductility giving it an advantage when energy absorption is needed during service. The results show the influence between white oil, gear oil and others. It has been observed that different environments caused difference in the life time of the specimen. The white oil environment caused best life time comparing to the gear oil in all of the alloys. The AM50 alloy showed excellent life time in the oil comparing to other environment. AZ91 presented large change in life time among the difference environments. In order to acquire scientific experience in different industries, it is very important to learn about the corrosion fatigue of magnesium alloys and to investigate their resistance corrosion fatigue together with the consideration of parts under stress.This research proves that the use of such methods is important to predict the lifetime of engines, tanks, pipes and other devices. (authors)

  7. Fracture mechanics parameters for small fatigue cracks

    Science.gov (United States)

    Newman, J. C., Jr.

    1992-01-01

    This paper presents a review of some common small-crack test specimens, the underlying causes of the small-crack effect, and the fracture-mechanics parameters that have been used to correlate or predict their growth behavior. This review concentrates on continuum mechanics concepts and on the nonlinear behavior of small cracks. The paper reviews some stress-intensity factor solutions for small-crack test specimens and develops some simple elastic-plastic J integral and cyclic J integral expressions that include the influence of crack-closure. These parameters were applied to small-crack growth data on two aluminum alloys, and a fatigue life prediction methodology is demonstrated. For these materials, the crack-closure transient from the plastic wake was found to be the major factor in causing the small-crack effect.

  8. Fatigue as it Affects Nursing.

    Science.gov (United States)

    2016-08-01

    : Editor's note: From its first issue in 1900 through to the present day, AJN has unparalleled archives detailing nurses' work and lives over more than a century. These articles not only chronicle nursing's growth as a profession within the context of the events of the day, but they also reveal prevailing societal attitudes about women, health care, and human rights. Today's nursing school curricula rarely include nursing's history, but it's a history worth knowing. To this end, From the AJN Archives highlights articles selected to fit today's topics and times.In this month's article from the January 1935 issue, Lillian M. Gilbreth, a highly respected psychologist and industrial engineer, examines the problem of fatigue in nursing. A nonnurse expert, Gilbreth notes the negative effects of fatigue on skills, a problem "enormously more serious when the product of the work is human comfort and sometimes even human life, as it often is with the work of the nurse." In their article in this issue, "Health Care Worker Fatigue," Lea Anne Gardner and Deborah Dubeck of the Pennsylvania Patient Safety Authority share examples of fatigue-related adverse events and discuss the need for both personal and institutional fatigue risk management strategies.

  9. Impact of shoulder position and fatigue on the flexion-relaxation response in cervical spine.

    Science.gov (United States)

    Nimbarte, Ashish D; Zreiqat, Majed; Ning, Xiaopeng

    2014-03-01

    Neck pain is common among general population with a high prevalence among the people who are routinely exposed to prolonged use of static head-neck postures. Prolonged static loading can cause localized muscle fatigue which may impact the stability of the cervical spine. In this study, flexion-relaxation phenomenon was used to study the post fatigue changes in the stability of cervical spine by evaluating the synergistic load sharing between muscles and viscoelastic elements. Thirteen male participants were recruited for data collection. The variables that influence cervical flexion-relaxation were studied pre- and post-fatigue using neutral and shrugged shoulder postures. The Sorensen protocol was used to induce neck extensor fatigue. Surface electromyography and optical motion capture systems were used to record neck muscle activation and head posture, respectively. Findings The flexion-relaxation phenomenon was observed only in the neutral shoulder position pre- and post-fatigue. The flexion relaxation ratio decreased significantly post-fatigue in neutral shoulder position but remained unchanged in shrugged shoulder position. The onset and offset angles and the corresponding durations of the silence period were significantly affected by the fatigue causing a post-fatigue expansion of silence period. Interpretation The muscular fatigue of neck extensors and shoulder position was found to modulate the cervical flexion-relaxation phenomenon. Early shifting of load sharing under fatigued condition indicates increased demands on the passive tissues to stabilize the cervical spine. Shrugging of shoulder seems to alter muscular demands of neck extensors and make cervical flexion-relaxation phenomenon disappear due to continuous activation of the neck extensors. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Long-term assessment of fatigue in patients with culture-confirmed Lyme disease.

    Science.gov (United States)

    Wormser, Gary P; Weitzner, Erica; McKenna, Donna; Nadelman, Robert B; Scavarda, Carol; Nowakowski, John

    2015-02-01

    Fatigue is a common symptom with numerous causes. Severe fatigue is thought to be an important manifestation of post-treatment Lyme disease syndrome. The frequency with which severe fatigue occurs as a long-term sequela in prospectively followed patients with Lyme disease is unknown. Patients with culture-confirmed Lyme disease who originally presented with erythema migrans have been evaluated annually in a prospective study to determine their long-term outcome. In 2011-2013, subjects were evaluated for fatigue using an 11-item Fatigue Severity Scale (FSS-11) that has been used in studies of post-treatment Lyme disease syndrome. An FSS-11 score of ≥4.0 is indicative of severe fatigue. A total of 100 subjects were assessed, 52% of whom were male; the mean age was 64.9 years (range, 42-86 years). The mean duration of follow-up was 15.4 years (range, 11-20 years). Nine subjects had severe fatigue but in none as a consequence of Lyme disease. Only 3 subjects were thought to possibly have persistent fatigue from Lyme disease. The FSS-11 value for these 3 individuals was less than 4, averaging 2.27, and none had functional impairment. Severe fatigue was found in 9 patients (9%) with culture-confirmed early Lyme disease at 11 to 20 years after presentation, but was due to causes other than Lyme disease. Fatigue of lesser severity was possibly due to Lyme disease, but was found in only 3% of 100 patients, and therefore is rarely a long-term complication of this infection. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Are significant others able accurately to assess fatigue, exertion fatigue and types of fatigue in domiciliary heart patients?

    NARCIS (Netherlands)

    Tiesinga, L J; Dassen, T W N; Halfens, RJG; Bernink, PJLM; Niemeijer, M G; van den Heuvel, W.J.A.

    2001-01-01

    Although fatigue is recognized as a subjective and person-elated diagnosis both in patients and in healthy subjects, there have been no studies performed to show whether 'significant others' surrounding fatigued subjects are able to assess accurately the level of fatigue that exists in patients. The

  12. Fatigue and Multiple Sclerosis

    Science.gov (United States)

    ... navigation Skip to content Menu Navigation National Multiple Sclerosis Society Sign In In Your Area Donate Donate ... MS What Causes MS? Who Gets MS? Multiple Sclerosis FAQs Types of MS Related Conditions Symptoms & Diagnosis ...

  13. Fatigue mechanism of yttrium-doped hafnium oxide ferroelectric thin films fabricated by pulsed laser deposition.

    Science.gov (United States)

    Huang, Fei; Chen, Xing; Liang, Xiao; Qin, Jun; Zhang, Yan; Huang, Taixing; Wang, Zhuo; Peng, Bo; Zhou, Peiheng; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Liu, Ming; Liu, Qi; Tian, He; Bi, Lei

    2017-02-01

    Owing to their prominent stability and CMOS compatibility, HfO2-based ferroelectric films have attracted great attention as promising candidates for ferroelectric random-access memory applications. A major reliability issue for HfO2 based ferroelectric devices is fatigue. So far, there have been a few studies on the fatigue mechanism of this material. Here, we report a systematic study of the fatigue mechanism of yttrium-doped hafnium oxide (HYO) ferroelectric thin films deposited by pulsed laser deposition. The influence of pulse width, pulse amplitude and temperature on the fatigue behavior of HYO during field cycling is studied. The temperature dependent conduction mechanism is characterized after different fatigue cycles. Domain wall pinning caused by carrier injection at shallow defect centers is found to be the major fatigue mechanism of this material. The fatigued device can fully recover to the fatigue-free state after being heated at 90 °C for 30 min, confirming the shallow trap characteristic of the domain wall pinning defects.

  14. Effects of yoga in managing fatigue in breast cancer patients: A randomized controlled trial

    Directory of Open Access Journals (Sweden)

    H S Vadiraja

    2017-01-01

    Full Text Available Background: Cancer-related fatigue is widely prevalent in cancer patients and affects quality of life in advanced cancer patients. Fatigue is caused due to both psychologic distress and physiological sequel following cancer progression and its treatment. In this study, we evaluate the effects of yogic intervention in managing fatigue in metastatic breast cancer patients. Methods: Ninety-one patients with metastatic breast cancer were randomized to receive integrated yoga program (n = 46 or supportive therapy and education (n = 45 over a 3-month period. Assessments such as perceived stress, fatigue symptom inventory, diurnal salivary cortisol, and natural killer cell counts were carried out before and after intervention. Analysis was done using an intention-to-treat approach. Postmeasures for the above outcomes were assessed using ANCOVA with respective baseline measure as a covariate. Results: The results suggest that yoga reduces perceived stress (P = 0.001, fatigue frequency (P < 0.001, fatigue severity (P < 0.001, interference (P < 0.001, and diurnal variation (P < 0.001 when compared to supportive therapy. There was a positive correlation of change in fatigue severity with 9 a.m. salivary cortisol levels. Conclusion: The results suggest that yoga reduces fatigue in advanced breast cancer patients.

  15. Association of Leukocyte Telomere Length with Fatigue in Nondisabled Older Adults

    Directory of Open Access Journals (Sweden)

    Laila Bendix

    2014-01-01

    Full Text Available Introduction. Fatigue is often present in older adults with no identified underlying cause. The accruing burden of oxidative stress and inflammation might be underlying factors of fatigue. We therefore hypothesized that leukocyte telomere length (LTL is relatively short in older adults who experience fatigue. Materials and Methods. We assessed 439 older nondisabled Danish twins. LTL was measured using Southern blots of terminal restriction fragments. Fatigue was measured by the Mob-T Scale based on questions on whether the respondents felt fatigued after performing six mobility items. Results. LTL was significantly associated with fatigue (P=0.023, showing an increase of 0.038 kb/fatigue score unit. Aging-related diseases and mental health did not explain the association, while lifestyle factors slightly attenuated the estimates. Conclusion. Our results support an association between LTL and fatigue. Further studies are required to confirm this finding and the link of LTL with oxidative stress/inflammation over the life course.

  16. Muscle fatigue evaluation of astronaut upper limb based on sEMG and subjective assessment

    Science.gov (United States)

    Zu, Xiaoqi; Zhou, Qianxiang; Li, Yun

    2012-07-01

    All movements are driven by muscle contraction, and it is easy to cause muscle fatigue. Evaluation of muscle fatigue is a hot topic in the area of astronaut life support training and rehabilitation. If muscle gets into fatigue condition, it may reduce work efficiency and has an impact on psychological performance. Therefore it is necessary to develop an accurate and usable method on muscle fatigue evaluation of astronaut upper limb. In this study, we developed a method based on surface electromyography (sEMG) and subjective assessment (Borg scale) to evaluate local muscle fatigue. Fifteen healthy young male subjects participated in the experiment. They performed isometric muscle contractions of the upper limb. sEMG of the biceps brachii were recorded during the entire process of isotonic muscle contraction and Borg scales of muscle fatigue were collected in certain times. sEMG were divided into several parts, and then mean energy of each parts were calculated by the one-twelfth band octave method. Equations were derived based on the relationship between the mean energy of sEMG and Borg scale. The results showed that cubic curve could describe the degree of local muscle fatigue, and could be used to evaluate and monitor local muscle fatigue during the entire process.

  17. Relationship between neuromuscular fatigue and spasticity in chronic stroke patients: a pilot study.

    Science.gov (United States)

    Boudarham, Julien; Roche, Nicolas; Teixeira, Mickael; Hameau, Sophie; Robertson, Johanna; Bensmail, Djamel; Zory, Raphael

    2014-04-01

    The aim of this study was to assess the effects of neuromuscular fatigue on stretch reflex-related torque and electromyographic activity of spastic knee extensor muscles in hemiplegic patients. The second aim was to characterize the time course of quadriceps muscle fatigue during repetitive concentric contractions. Eighteen patients performed passive, isometric and concentric isokinetic evaluations before and after a fatigue protocol using an isokinetic dynamometer. Voluntary strength and spasticity were evaluated following the simultaneous recording of torque and electromyographic activity of rectus femoris (RF), vastus lateralis (VL) and biceps femoris (BF). Isometric knee extension torque and the root mean square (RMS) value of VL decreased in the fatigued state. During the fatigue protocol, the normalized peak torque decreased whereas the RMS of RF and BF increased between the first five and last five contractions. There was a linear decrease in the neuromuscular efficiency-repetitions relationships for RF and VL. The peak resistive torque and the normalized RMS of RF and VL during passive stretching movements were not modified by the fatigue protocol for any stretch velocity. This study showed that localized quadriceps muscle fatigue caused a decrease in voluntary strength which did not modify spasticity intensity. Changes in the distribution of muscle fiber type, with a greater number of slow fibers on the paretic side, may explain why the stretch reflex was not affected by fatigue. Copyright © 2014. Published by Elsevier Ltd.

  18. Advanced methods of fatigue assessment

    CERN Document Server

    Radaj, Dieter

    2013-01-01

    The book in hand presents advanced methods of brittle fracture and fatigue assessment. The Neuber concept of fictitious notch rounding is enhanced with regard to theory and application. The stress intensity factor concept for cracks is extended to pointed and rounded corner notches as well as to locally elastic-plastic material behaviour. The averaged strain energy density within a circular sector volume around the notch tip is shown to be suitable for strength-assessments. Finally, the various implications of cyclic plasticity on fatigue crack growth are explained with emphasis being laid on the DJ-integral approach.   This book continues the expositions of the authors’ well known reference work in German language ‘Ermüdungsfestigkeit – Grundlagen für Ingenieure’ (Fatigue strength – fundamentals for engineers).

  19. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  20. Reactive Oxygen Species as Agents of Fatigue

    National Research Council Canada - National Science Library

    REID, MICHAEL B

    2016-01-01

    ...) generated in exercising muscle and the potential role that ROS may play in fatigue. METHODSReports in the peer-reviewed literature were analyzed and published findings integrated to synthesize an overview of ROS as agents of fatigue...

  1. Fatigue In Teenagers on the interNET--the FITNET Trial. A randomized clinical trial of web-based cognitive behavioural therapy for adolescents with chronic fatigue syndrome: study protocol. [ISRCTN59878666

    NARCIS (Netherlands)

    Nijhof, S.L.; Bleijenberg, G.; Uiterwaal, C.S.; Kimpen, J.L.L.; Putte, E.M. van de

    2011-01-01

    BACKGROUND: Chronic Fatigue Syndrome (CFS) is increasingly recognized as a cause of disability and inactivity in adolescents in the Netherlands. CFS is characterized by unexplained fatigue lasting more than 6 months. Cognitive Behavioural Therapy (CBT) has proven to be effective. However, CBT

  2. Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

    OpenAIRE

    Lian, B.; Ueno, A; Iwashita, T

    2016-01-01

    To substitute for a traditional replication technique, an in-situ fatigue crack observing system for rotating bending testing machine has been newly developed. For verifying performance of this observing system, fatigue tests were carried out by using fatigue specimen having a small artificial defect. It is proved that this system can be detect a small fatigue crack and its propagation behavior.

  3. Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

    OpenAIRE

    Lian, B.; Ueno, A; Iwashita, T

    2015-01-01

    To substitute for a traditional replication technique, an in-situ fatigue crack observing system for rotating bending testing machine has been newly developed. For verifying performance of this observing system, fatigue tests were carried out by using fatigue specimen having a small artificial defect. It is proved that this system can be detect a small fatigue crack and its propagation behavior.

  4. Fatigue behavior of the magnesium alloy ZK60 in high cycle fatigue

    NARCIS (Netherlands)

    Constantinescu, D.M.; Moldovan, P.; Sillekens, W.H.; Sandu, M.; Apostol, D.A.; Miron, M.C.

    2009-01-01

    Not too much information is available in the literature for establishing fatigue properties of magnesium alloys. A compilation of existing fatigue and fatigue crack growth data of different Mg-alloys has been published by ASM International. One can underline that fatigue properties of some of the

  5. The role of central and peripheral muscle fatigue in postcancer fatigue: a randomized controlled trial

    NARCIS (Netherlands)

    Prinsen, H.; Dijk, J.P. van; Zwarts, M.J.; Leer, J.W.H.; Bleijenberg, G.; Laarhoven, H.W.M. van

    2015-01-01

    CONTEXT: Postcancer fatigue is a frequently occurring problem, impairing quality of life. Little is known about (neuro)physiological factors determining postcancer fatigue. It may be hypothesized that postcancer fatigue is characterized by low peripheral muscle fatigue and high central muscle

  6. Fatigue Strain and Damage Analysis of Concrete in Reinforced Concrete Beams under Constant Amplitude Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Fangping Liu

    2016-01-01

    Full Text Available Concrete fatigue strain evolution plays a very important role in the evaluation of the material properties of concrete. To study fatigue strain and fatigue damage of concrete in reinforced concrete beams under constant amplitude bending fatigue loading, constant amplitude bending fatigue experiments with reinforced concrete beams with rectangular sections were first carried out in the laboratory. Then, by analyzing the shortcomings and limitations of existing fatigue strain evolution equations, the level-S nonlinear evolution model of fatigue strain was constructed, and the physical meaning of the parameters was discussed. Finally, the evolution of fatigue strain and fatigue damage of concrete in the compression zone of the experimental beam was analyzed based on the level-S nonlinear evolution model. The results show that, initially, fatigue strain grows rapidly. In the middle stages, fatigue strain is nearly a linear change. Because the experimental data for the third stage are relatively scarce, the evolution of the strain therefore degenerated into two phases. The model has strong adaptability and high accuracy and can reflect the evolution of fatigue strain. The fatigue damage evolution expression based on fatigue strain shows that fatigue strain and fatigue damage have similar variations, and, with the same load cycles, the greater the load level, the larger the damage, in line with the general rules of damage.

  7. Comparison of the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy young women.

    Science.gov (United States)

    Shirazi, Zahra Rojhani; Jahromi, Fatemeh Nikhalat

    2013-09-01

    The maintenance of balance is an essential requirement for the performance of daily tasks and sporting activities and muscular fatigue is a factor to impair postural control, so this study was done to compare the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy subjects. Fifteen healthy female students (24.3 ± 2.6 years) completed three testing session with a break period of at least 2 days. During each session, postural control was assessed during two 30-s trials of bipedal stance with eyes close before and after the fatigue protocol. Fatigue protocols were performed by 60% of their unfatigued Maximum Voluntary Contraction of unilateral ankle plantar flexors, bilateral lumbar extensors and bilateral neck extensors. One of the three fatigue protocols was performed on each session. The result showed that fatigue had a significant effect on COP velocity and it increase COP velocity but there was not found any difference in postural sway between muscle groups. Localized muscle fatigue caused deficits in postural control regardless of the location of fatigue. Authors suggest the possibility of the contributions of central mechanisms to postural deficits due to fatigue and it seems that difference was not between muscle groups due to central fatigue.

  8. Fatigue of LMFBR piping due to flow stratification

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, W.S.

    1983-01-01

    Flow stratification due to reverse flow was simulated in a 1/5-scale water model of a LMFBR primary pipe loop. The stratified flow was observed to have a dynamic interface region which oscillated in a wave pattern. The behavior of the interface was characterized in terms of location, local temperature fluctuation and duration for various reverse flow conditions. A structural assessment was performed to determine the effects of stratified flow on the fatigue life of the pipe. Both the static and dynamic aspects of flow stratification were examined. The dynamic interface produces thermal striping on the inside of the pipe wall which is shown to have the most deleterious effect on the pipe wall and produce significant fatigue damage relative to a static interface.

  9. Fracture probability along a fatigue crack path

    Energy Technology Data Exchange (ETDEWEB)

    Makris, P. [Technical Univ., Athens (Greece)

    1995-03-01

    Long experience has shown that the strength of materials under fatigue load has a stochastic behavior, which can be expressed through the fracture probability. This paper deals with a new analytically derived law for the distribution of the fracture probability along a fatigue crack path. The knowledge of the distribution of the fatigue fracture probability along the crack path helps the connection between stress conditions and the expected fatigue life of a structure under stochasticly varying loads. (orig.)

  10. Fatigue Among Older Advanced Cancer Patients

    OpenAIRE

    Su, Wen-Hao; Yeh, En-Tien; Chen, Hong-Wen; Wu, Meng-Hao; Lai, Yuen-Liang

    2011-01-01

    Background: Fatigue among older patients and cancer patients is often reported in the literatures. However, relatively few studies can conclude whether fatigue happens more frequently in older patients with advanced cancer. We designed our study to examine the prevalence and features of fatigue among older advanced cancer patients in Taiwan. Methods: Because self-reporting from patients is the most effective method to measure fatigue, the instrument of International Classification of Disea...

  11. Simulation of Stochastic Loads for Fatigue Experiments

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Brincker, Rune

    A simple direct simulation method for stochastic fatigue load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load...... second using an IBM PC. Finally the proposed simulation method for fatigue load generation is tested by comparing some fatigue damage measures obtained by the simulation methods....

  12. Cancer-Related Fatigue: a multidimensional approach

    OpenAIRE

    Raaf, Pleun

    2013-01-01

    textabstractFatigue is experienced by cancer patients in all stages of the disease trajectory: from before diagnosis to years after completing treatment and also in advanced cancer. Fatigue has a greater negative influence on quality of life and daily activities than any other cancer-related symptom. Although both national and international guidelines have been developed to enhance the management of cancer-related fatigue, cancer-related fatigue is still poorly understood. This thesis describ...

  13. Fatigue Among Spanish and English Speaking Latinos

    OpenAIRE

    Torres-Harding, Susan R.; Mason-Shutter, Jennifer; Jason, Leonard A.

    2008-01-01

    The present study investigated sociodemographic differences, fatigue severity, and the occurrence of prolonged or chronic fatigue reported by Spanish speaking and English speaking Latinos. The sample included 2,102 English speaking Latinos and 1,348 Spanish speaking Latinos interviewed as part of an epidemiological study of persons with chronic fatigue syndrome in the Chicago area. Results indicated that English speaking Latinos scored higher on measure of fatigue than Spanish speaking Latino...

  14. Risk Based Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, M.H.; Kroon, I.B.

    1992-01-01

    Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value of the maxi......Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value...

  15. Modeling Creep-Fatigue-Environment Interactions in Steam Turbine Rotor Materials for Advanced Ultra-supercritical Coal Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen [General Electric Global Research, Niskayuna, NY (United States)

    2014-04-01

    The goal of this project is to model creep-fatigue-environment interactions in steam turbine rotor materials for advanced ultra-supercritical (A-USC) coal power Alloy 282 plants, to develop and demonstrate computational algorithms for alloy property predictions, and to determine and model key mechanisms that contribute to the damages caused by creep-fatigue-environment interactions.

  16. Prediction of corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints

    Science.gov (United States)

    An, J.; Chen, J.; Gou, G.; Chen, H.; Wang, W.

    2017-07-01

    Through investigating the corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints in 3.5 wt.% NaCl solution, corrosion fatigue crack initiation life is formulated as Ni = 6.97 × 1012[Δσeqv1.739 - 491.739]-2 and the mechanism of corrosion fatigue crack initiation is proposed. SEM and TEM tests revealed that several corrosion fatigue cracks formed asynchronously and the first crack does not necessarily develop into the leading crack. The uneven reticular dislocations produced by fatigue loading are prone to piling up and tangling near the grain boundaries or the second phases and form the “high dislocation-density region” (HDDR), which acts as an anode in microbatteries and dissolved to form small crack. Thus the etching pits, HDDR near the grain boundaries and second phases are confirmed as the main causes inducing the initiation of fatigue crack.

  17. Pilot fatigue survey: exploring fatigue factors in air medical operations.

    Science.gov (United States)

    Gregory, Kevin B; Winn, William; Johnson, Kent; Rosekind, Mark R

    2010-01-01

    Humans confront significant physiological challenges with sleep and alertness when working in 24/7 operations. A web-based national survey of air medical pilots examined issues relevant to fatigue and sleep management. Six hundred ninety-seven responses were received, with a majority of rotor wing pilots working 3/3/7 and 7/7 duty schedules. Over 84% of the pilots reported that fatigue had affected their flight performance; less than 28% reported "nodding off" during flight. More than 90% reported a separate work site "rest" room with a bed available. Over 90% reported no company policies restricting on-duty sleep. Approximately half of the pilots reported getting 4 hours or more sleep during a typical night shift. Approximately half reported that sleep inertia had never compromised flight safety. Over 90% reported that it was better to sleep during the night and overcome sleep inertia if necessary. Survey results reflected practices that can mitigate the degrading effects of fatigue, including the availability of designated work-site sleep rooms. As demands continue to evolve, the need remains for sustained efforts to address fatigue-related risks in the air medical transport industry. This includes further study of sleep inertia issues and the need for alertness management programs. Copyright © 2010 Air Medical Journal Associates. Published by Elsevier Inc. All rights reserved.

  18. [Dutch language area definition of chronic fatigue].

    NARCIS (Netherlands)

    Korenromp, I.H.; Meeus, M.; Bleijenberg, G.

    2012-01-01

    Chronic fatigue is a frequent but unspecific characteristic of many diseases. However, a clear definition of 'chronic fatigue' is still lacking. The Flemish-Dutch Research Group - Chronic Fatigue (VNO-CHROVER) has taken the opportunity to formulate such a definition that can be widely applied. This

  19. Compassion Fatigue in the Military Caregiver

    Science.gov (United States)

    2009-03-01

    alternative or additional programs, process or intervention to address compassion fatigue , burnout , stress disorder or other debilitating post-traumatic...Combat Trauma, Shared Trauma, Posttraumatic Stress Disorder, Burnout CLASSIFICATION: Unclassified Compassion Fatigue (CF) is a critical problem with...alternative or additional programs, process or intervention to address compassion fatigue , burnout , stress disorder or other debilitating post-traumatic

  20. How do women with lupus manage fatigue?

    DEFF Research Database (Denmark)

    Kier, Anne Ørnholt; Midtgaard, Julie; Hougaard, Karin Sørig

    2016-01-01

    Objective: Half of patients with systemic lupus erythematosus (SLE) consider fatigue to be the most disabling disease symptom. To develop and promote strategies to prevent and control fatigue, this study aimed to describe how women with SLE manage the experience of fatigue. Methods: Four focus...