WorldWideScience

Sample records for biological fatigue

  1. Biologic interventions for fatigue in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Almeida, Celia; Choy, Ernest H S; Hewlett, Sarah;

    2016-01-01

    BACKGROUND: Fatigue is a common and potentially distressing symptom for patients with rheumatoid arthritis (RA), with no accepted evidence-based management guidelines. Evidence suggests that biologic interventions improve symptoms and signs in RA as well as reducing joint damage. OBJECTIVES: To...... evaluate the effect of biologic interventions on fatigue in rheumatoid arthritis. SEARCH METHODS: We searched the following electronic databases up to 1 April 2014: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, Current Controlled Trials...... contacted key authors. SELECTION CRITERIA: We included randomised controlled trials if they evaluated a biologic intervention in people with rheumatoid arthritis and had self reported fatigue as an outcome measure. DATA COLLECTION AND ANALYSIS: Two reviewers selected relevant trials, assessed methodological...

  2. 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, ...

  3. Fatigue

    Science.gov (United States)

    ... enough sleep, good nutrition, or a low-stress environment, it should be evaluated by your doctor. ... relax. Try yoga or meditation. Maintain a reasonable work and ... or depression, treating it often helps the fatigue. Be aware ...

  4. Fatigue

    Science.gov (United States)

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

  5. Fatigue

    Science.gov (United States)

    ... organs. Your body also changes the way it processes foods and nutrients. All of these changes are stressful for your body and may lead to fatigue. Physical and psychological changes during pregnancy can also cause mental and emotional stress. This stress can add to your feelings ...

  6. Brain Tumors and Fatigue

    Science.gov (United States)

    ... for e-updates Please leave this field empty Fatigue SHARE Home > Treatment and Care > Side Effects and ... One of the most common side effects is fatigue. Fatigue may accompany surgery, radiation, chemotherapy or biologic ...

  7. Fatigue management in the workplace

    OpenAIRE

    Khosro Sadeghniiat-Haghighi; Zohreh Yazdi

    2015-01-01

    Workers′ fatigue is a significant problem in modern industry, largely because of high demand jobs, long duty periods, disruption of circadian rhythms, and accumulative sleep debt that are common in many industries. Fatigue is the end result of integration of multiple factors such as time awake, time of day, and workload. Then, the full understanding of circadian biologic clock, dynamics of transient and cumulative sleep loss, and recovery is required for effective management of workplace fati...

  8. 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 ...

  9. 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 to...

  10. An overview of fatigue

    International Nuclear Information System (INIS)

    Four topics are briefly discussed in this paper: fatigue crack initiation and growth in a nickel-base superalloy single crystal, the environment effect on near-threshold fatigue crack growth behaviour, the role of crack closure in load-interaction effects in fatigue crack growth, and the nature of creep-fatigue interactions, if any, during fatigue crack growth. (Author)

  11. Breast Cancer and Fatigue

    OpenAIRE

    Bardwell, Wayne A; Ancoli-Israel, Sonia

    2008-01-01

    Fatigue is a common and disabling symptom in breast cancer patients and survivors. A rather nebulous concept, fatigue overlaps with sleepiness and depressed mood. In this chapter, we cover methods for assessing fatigue; describe the occurrence of fatigue before, during and after initial treatment; present possible underlying mechanisms of fatigue; and, enumerate approaches to its treatment.

  12. Myalgic Encephalomyelitis (ME and Chronic Fatigue Syndrome (CFS: The essence of objective assessment, accurate diagnosis, and acknowledging biological and clinical subgroups.

    Directory of Open Access Journals (Sweden)

    Frank N.M. Twisk

    2014-03-01

    Full Text Available Myalgic Encephalomyelitis (ME was identified as a new clinical entity in 1959 and has been acknowledged as a disease of the central nervous system/neurological disease by the World Health Organisation since 1969. Cognitive impairment, (muscle weakness, circulatory disturbances, marked variability of symptoms, and, above all, post-exertional malaise: a long-lasting increase of symptoms after minor exertion, are distinctive symptoms of ME.Chronic Fatigue Syndrome (CFS was introduced in 1988 and was redefined into clinically evaluated, unexplained (persistent or relapsing chronic fatigue, accompanied by at least four out of a list of eight symptoms, e.g. headaches and unrefreshing sleep, in 1994.Although the labels are used interchangeably, ME and CFS define distinct diagnostic entities. Post-exertional malaise and cognitive deficits e.g. are not mandatory for the diagnosis CFS, while obligatory for the diagnosis ME. Fatigue is not obligatory for the diagnosis ME.Since fatigue and other symptoms are subjective and ambiguous, research has been hampered. Despite this and other methodological issues, research has observed specific abnormalities in ME/CFS repetitively, e.g. immunological abnormalities, oxidative and nitrosative

  13. Fatigue and Multiple Sclerosis

    Science.gov (United States)

    Fatigue - National Multiple Sclerosis Society Skip to navigation Skip to content Menu Navigation National Multiple Sclerosis Society ... Twitter Email Home Symptoms & Diagnosis MS Symptoms Fatigue Fatigue Share Smaller Text Larger Text Print In this ...

  14. MANAGING FATIGUE IN SPORTS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Fatigue is a multifactorial process. Depletion of energy sources, including adenosine triphosphate (ATP), phosphocreatine (PCr), plus carbohydrates (CHO) like muscle glycogen and blood glucose can contribute to fatigue.

  15. Cancer-related fatigue: Mechanisms, risk factors, and treatments

    OpenAIRE

    Bower, Julienne E.

    2014-01-01

    Fatigue is one of the most common and distressing side effects of cancer and its treatment, and may persist for years after treatment completion in otherwise healthy survivors. Cancer-related fatigue causes disruption in all aspects of quality of life and may be a risk factor for reduced survival. The prevalence and course of fatigue in cancer patients has been well characterized, and there is growing understanding of underlying biological mechanisms. Inflammation has emerged as a key biologi...

  16. [Fatigue in neuromuscular disease

    NARCIS (Netherlands)

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

    2004-01-01

    Chronic fatigue is a symptom of diseases such as cancer, multiple sclerosis, Parkinson's and cerebrovascular disease. Fatigue can also be present in people with no demonstrable somatic disease. If certain criteria are met, chronic-fatigue syndrome may be diagnosed in these cases. Fatigue is a multi-

  17. Biologic

    CERN Document Server

    Kauffman, L H

    2002-01-01

    In this paper we explore the boundary between biology and the study of formal systems (logic). In the end, we arrive at a summary formalism, a chapter in "boundary mathematics" where there are not only containers but also extainers ><, entities open to interaction and distinguishing the space that they are not. The boundary algebra of containers and extainers is to biologic what boolean algebra is to classical logic. We show how this formalism encompasses significant parts of the logic of DNA replication, the Dirac formalism for quantum mechanics, formalisms for protein folding and the basic structure of the Temperley Lieb algebra at the foundations of topological invariants of knots and links.

  18. 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.

  19. 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...

  20. Chronic Fatigue Syndrome

    Science.gov (United States)

    ... that can go on for months with no obvious cause. This kind of fatigue makes it really ... causing fatigue previous or current conditions such as depression, an eating disorder, psychiatric illness. To better understand ...

  1. New Mom Fatigue

    Science.gov (United States)

    ... Home > Baby > New parents > New mom fatigue New mom fatigue E-mail to a friend Please fill ... But it can also leave many new parents, moms especially, feeling overwhelmed and exhausted. Some moms might ...

  2. [Fatigue in neuromuscular disease].

    Science.gov (United States)

    Van Engelen, B G M; Kalkman, J S; Schillings, M L; Van Der Werf, S P; Bleijenberg, G; Zwarts, M J

    2004-07-01

    Chronic fatigue is a symptom of diseases such as cancer, multiple sclerosis, Parkinson's and cerebrovascular disease. Fatigue can also be present in people with no demonstrable somatic disease. If certain criteria are met, chronic-fatigue syndrome may be diagnosed in these cases. Fatigue is a multi-dimensional concept with physiological and psychological dimensions. The 'Short Fatigue Questionnaire' consisting of 4 questions is a tool to measure fatigue with a high degree of reliability and validity. Within the group of neuromuscular disorders, fatigue has been reported by patients with post-polio syndrome, myasthenia gravis, and Guillain-Barré syndrome. The percentage of neuromuscular patients suffering from severe fatigue (64%) is comparable with that of patients with multiple sclerosis, a disease in which fatigue is an acknowledged symptom. Now that reliable psychological and clinical neurophysiological techniques are available, a multidisciplinary approach to fatigue in patients with well-defined neuromuscular disorders may contribute towards the elucidation of the pathophysiological mechanisms of chronic fatigue, with the ultimate goal being to develop methods of treatment for fatigue in neuromuscular patients. PMID:15283024

  3. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, M. H.; 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 ...

  4. 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.

  5. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

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

    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...... 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...

  6. 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...... failure explanation under fatigue and static load conditions is observed. In the present study 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 between stiffness reduction...

  7. AREVA fatigue concept

    International Nuclear Information System (INIS)

    Modern state-of-the-art fatigue monitoring approaches gain in importance as part of the ageing management of nuclear power plant components. Consequently, lots of operators have to deal with demanding security requirements to ensure the safe operation of power plants. AREVA disposes of a long tradition in the development of fatigue and structural health monitoring solutions. Nuclear power plant applications require the qualified assessment of measured thermo-mechanical loads. The core challenge is the identification and qualified processing of realistic load-time histories. The related methodological requirements will be explained in detail within this contribution. In terms of the nuclear industry, the ageing management of power plant components is nowadays a main issue for all actors: states, regulatory agencies, operators, designers or suppliants. As regards fatigue assessment of nuclear components stringent safety standards imply the consideration of new parameters in the framework of the fatigue analysis process: new design fatigue curves, consideration of environmental fatigue (EAF) parameters and stratification effects. In this general context AREVA developed the integral approach AREVA Fatigue Concept (AFC) with new tools and methods in order to live up to operators’ expectations: Simplified Fatigue Estimation (SFE), Fast Fatigue Evaluation (FFE) and Detailed Fatigue Check (DFC). Based on real measured thermal loads (FAMOSi Local Measurements) and superposed mechanical loads the Fast Fatigue Evaluation (FFE) process allows a highly automated and reliable data processing to evaluate cumulative usage factors of mechanical components. Calculation and management of results are performed within the software frontend FAMOSi, thus impact of operating cycles on components in terms of stress and fatigue usage can be taken into account in order to plan optimized decisions relating to the plant operation or maintenance activities. The paper mainly describes the

  8. Extension of recovery time from fatigue by repeated rest with short-term sleep during continuous fatigue load: Development of chronic fatigue model.

    Science.gov (United States)

    Kanzaki, Akinori; Okauchi, Takashi; Hu, Di; Shingaki, Tomotaka; Katayama, Yumiko; Koyama, Hidenori; Watanabe, Yasuyoshi; Cui, Yilong

    2016-05-01

    Homeostasis is known to be involved in maintaining the optimal internal environment, helping to achieve the best performance of biological functions. At the same time, a deviation from optimal conditions often attenuates the performance of biological functions, and such restricted performance could be considered as individual fatigue, including physical and mental fatigue. The present study seeks to develop an animal model of chronic or subacute fatigue in which the recovery time is extended through the gradual disruption of homeostasis. We show that repeated short-term rest periods with certain lengths of sleep during continuous fatigue loading extend recovery from spontaneous nighttime activity but not physical performance in comparison with a continuous fatigue-loading procedure. Furthermore, the immobility time in a forced swimming test was extended by repeated short-term rests. These results suggest that repeated short-term rest with certain lengths of sleep during continuous fatigue loading is able to extend the recovery from mental fatigue but not from physical fatigue and that this effect might occur via the disruption of a homeostatic mechanism that is involved in restoring the optimal internal environment. © 2016 Wiley Periodicals, Inc. PMID:26864568

  9. Compassion fatigue in nurses.

    Science.gov (United States)

    Yoder, Elizabeth A

    2010-11-01

    Compassion fatigue, trigger situations, and coping strategies were investigated in hospital and home care nurses. The Professional Quality of Life Scale measured compassion fatigue, compassion satisfaction, and burnout. Narrative questions elicited trigger situations and coping strategies. Compassion fatigue scores were significantly different between nurses who worked 8- or 12-hour shifts. Fifteen percent of the participants had scores indicating risk of the compassion fatigue. There were significant differences in compassion satisfaction, depending on the unit worked and time as a nurse. The most common category of trigger situations was caring for the patient. Work-related and personal coping strategies were identified. PMID:21035028

  10. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

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

    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 is...

  11. Myth vs. Fact: Adrenal Fatigue

    Science.gov (United States)

    ... Hormones and Health › Myth vs Fact › Adrenal Fatigue Myth vs. Fact Adrenal Fatigue January 2015 Download PDFs ... science. This fact sheet was created to address myths about adrenal fatigue and to provide facts on ...

  12. Physiological and neurophysiological determinants of postcancer fatigue: design of a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Prinsen Hetty

    2012-06-01

    . The results of this study are not only essential for a theoretical understanding of this invalidating condition, but also for providing an objective biological marker for fatigue that could support the diagnosis and follow-up of treatment. Trial registration The study is registered at http://ClinicalTrials.gov (NCT01096641.

  13. 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 is...... observed between stiffness reduction and accumulated creep. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and an explanation at a microstructural level is...

  14. Fatigue, depression, and social adjustment in chronic fatigue syndrome.

    OpenAIRE

    Walford, G.A.; Nelson, W. M.; McCluskey, D R

    1993-01-01

    The aims of this study were to determine the characteristics and perceived levels of fatigue and the prevalence of depression in children with chronic fatigue syndrome and to assess the effects of illness on schooling and social functioning. Twelve children with chronic fatigue syndrome were compared with a matched group of children with cystic fibrosis and matched healthy controls. Levels of fatigue (fatigue questionnaire), depression (children's depression inventory), and social adjustment ...

  15. Fatigue, degradation, and fracture 1990

    Energy Technology Data Exchange (ETDEWEB)

    Bamford, W.H. (Westinghouse Energy Systems (US)); Becht, C. IV (Becht Engineering Co., Inc. (US)); Bhandari, S. (Framatome (FR)); Gilman, J.D. (Electric Power Research Institute (US)); James, L.A. (Westinghouse Bettis Laboratory (US)); Prager, M. (Materials Properties Council (US))

    1990-01-01

    This book contains papers presented at the 1990 Pressure Vessels and Piping Conference. It is organized under the following headings: Environmental fatigue crack growth; Fatigue analysis and fracture assessment; Fatigue and fracture of piping; Fatigue and fracture of vessels; Degradation of ferritic, austenitic, and duplex stainless alloys in nuclear service.

  16. 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)

  17. Metabolic Factors in Fatigue

    Institute of Scientific and Technical Information of China (English)

    Mark Hargreaves

    2006-01-01

    Increased non-oxidative and oxidative ATP production via metabolic pathways in skeletal muscle is essential for the maintenance of force and power production during exercise. However, substrate depletion and accumulation of metabolic byproducts are potential causes of fatigue. Reduced PCr availability can limit power production during sprint exercise, whereas carbohydrate depletion is a major limitation to endurance performance. During sprint exercise increased Pi and H+ may contribute to fatigue, and during prolonged strenuous exercise, the accumulation of NH3, reactive oxygen species, and heat can limit performance. Appropriate training programs and nutritional interventions are potential strategies to enhance fatigue resistance and exercise performance.

  18. Determinants of fatigue and stress

    OpenAIRE

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

    2011-01-01

    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 Que...

  19. Fatigue of dental ceramics

    OpenAIRE

    Zhang, Yu; Sailer, Irena; lawn, brian

    2013-01-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics

  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’ ... Sex Sexual Side Effects Body Image and Sexuality Improving Sexual Health With Medical Approaches Improving Sexual Health ...

  1. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    This review describes when fatigue may develop during soccer games and the potential physiological mechanisms that cause fatigue in soccer. According to time?-?motion analyses and performance measures during match-play, fatigue or reduced performance seems to occur at three different stages......, acidity or the breakdown of creatine phosphate. Instead, it may be related to disturbances in muscle ion homeostasis and an impaired excitation of the sarcolemma. Soccer players' ability to perform maximally is inhibited in the initial phase of the second half, which may be due to lower muscle...... 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...

  2. 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...

  3. 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...

  4. 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.

  5. Modafinil May Alleviate Poststroke Fatigue

    DEFF Research Database (Denmark)

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

    2015-01-01

    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 was....... 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...

  6. Chronic Fatigue Syndrome (CFS): Symptoms

    Science.gov (United States)

    ... please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Symptoms On this Page ... Symptoms What's the Clinical Course of CFS? Chronic fatigue syndrome can be misdiagnosed or overlooked because its ...

  7. 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.)

  8. Fatigue Strength of Weathering Steel

    OpenAIRE

    Kunz, Ludvík; Lukáš, Petr; Klusák, Jan

    2012-01-01

    Fatigue behaviour of Atmofix 52 steel (comparable to COR-TENâ steel) exposed to atmospheric corrosion for 20 years was investigated. S-N curves for load symmetrical cycling and cycling with stress ratio R = 0 were determined on specimens detracted from a failed transmission tower. The data were compared with those on material without a rust layer. The fracture surfaces and, in particular, the sites of fatigue crack initiation were analyzed. Substantial decrease of fatigue life and fatigue lim...

  9. Fatigue and cognition - hormonal perspectives

    OpenAIRE

    Möller, Marika

    2013-01-01

    Fatigue is a common complaint and considered a very challenging symptom to cope with in many different medical diseases. The assessment of fatigue is bound up with the problems of both conceptualization and definition. In addition, few studies have investigated suitable neuropsychological tests to examine fatigue and its consequences. This thesis evaluates whether neuropsychological tests can elicit cognitive fatigue. It also investigates whether specific hormones and hormon...

  10. Fatigue: More Than Being Tired

    Science.gov (United States)

    ... suggest you become more active . Some Illnesses Cause Fatigue Feeling fatigued can be like an alarm going off in your body. It may be the first sign that something is wrong. But, fatigue itself is not a disease. For example, many ...

  11. Fatigue Strength of Weathering Steel

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Klusák, Jan

    2012-01-01

    Roč. 18, č. 1 (2012), s. 18-22. ISSN 1392-1320 Grant ostatní: GA MPO(CZ) FT/TA5/076 Institutional support: RVO:68081723 Keywords : fatigue of weathering steel * corrosion pits * fatigue notch factor Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.522, year: 2012

  12. Fatigue in systemic lupus erythematosus

    OpenAIRE

    Ahn, Grace E.; Ramsey-Goldman, Rosalind

    2012-01-01

    Systemic lupus erythematosus is a chronic inflammatory autoimmune disease often characterized by fatigue, with significant effects on physical functioning and wellbeing. The definition, prevalence and factors associated with fatigue, including physical activity, obesity, sleep, depression, anxiety, mood, cognitive dysfunction, vitamin D deficiency/insufficiency, pain, effects of medications and comorbidities, as well as potential therapeutic options of fatigue in the systemic lupus erythemato...

  13. Fatigue data compilation and evaluation of fatigue on design

    International Nuclear Information System (INIS)

    The aim of this report is a review of the available fatigue data of various materials necessary for the design of large superconducting magnets for fusion. One of the primary objectives of this work is to present a broad outline of the low temperature fatigue data of relevant materials within the scope of available data. Besides the classical fatigue data of materials the fatigue crack propagation measurements are outlined widely. The existing recommendations for the design of cryogenic structures are described. A brief introduction of fracture mechanics as well as a historical background of the development of our present day understanding of fatigue has been done. (orig.)

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

    International Nuclear Information System (INIS)

    This paper presents a fundamental investigation of the fatigue and thermal fatigue characteristics, with an emphasis on the microstructural development during fatigue, of Sn-Pb solder joints. Fatigue tests were performed in simple shear on both 60Sn-40Pb and 5Sn-95Pb solder joints. Isothermal fatigue tests show increasing fatigue life of 60Sn-40Pb solder joints with decreasing strain and temperature. In contrast, such behavior was not observed in the isothermal fatigue of 5Sn-95Pb solder joints. Thermal fatigue results on 60Sn-40Pb solder cycled between -550C and 1250C show that a coarsened region develops in the center of the joint. Both Pb-rich and Sn-rich phases coarsen, and cracks form within these coarsened regions. The failure mode 60Sn-40Pb solder joints in thermal and isothermal fatigue is similar: cracks form intergranularly through the Sn-rich phase or along Sn/Pb interphase boundaries. Extensive cracking is found throughout the 5Sn-95Pb joint for both thermal and isothermal fatigue. In thermal fatigue the 5Sn-95Pb solder joints failed after fewer cycles than 60Sn-40Pb

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

    International Nuclear Information System (INIS)

    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.

  16. Chronic fatigue syndrome.

    NARCIS (Netherlands)

    Prins, J.B.; Meer, J.W.M. van der; Bleijenberg, G.

    2006-01-01

    During the past two decades, there has been heated debate about chronic fatigue syndrome (CFS) among researchers, practitioners, and patients. Few illnesses have been discussed so extensively. The existence of the disorder has been questioned, its underlying pathophysiology debated, and an effective

  17. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, MM; 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

  18. CONTRIBUTIONS REGARDING FRETTING FATIGUE

    OpenAIRE

    Stefan GHIMISI

    2013-01-01

    Fretting phenomenon is a complex deterioration phenomenon that can be found in most technicalapplications which require the existence of contacts undergoing a small amplitude oscillatory motion. Frettinghas two sides, one given by fretting-wear and another one given by fretting-fatigue, both leading to specificdeteriorations.

  19. CONTRIBUTIONS REGARDING FRETTING FATIGUE

    Directory of Open Access Journals (Sweden)

    Stefan GHIMISI

    2013-05-01

    Full Text Available Fretting phenomenon is a complex deterioration phenomenon that can be found in most technicalapplications which require the existence of contacts undergoing a small amplitude oscillatory motion. Frettinghas two sides, one given by fretting-wear and another one given by fretting-fatigue, both leading to specificdeteriorations.

  20. Fatigue in Composite Materials

    Science.gov (United States)

    1984-01-01

    The deformation and failure behavior of graphite/epoxy tubes under biaxial loading was investigated. The increase of basic understanding of and provide design information for the bi-axial response of graphite/epoxy composites to fatigue loads are considered.

  1. 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…

  2. Fatigue Strength of Weathering Steel

    Directory of Open Access Journals (Sweden)

    Ludvík KUNZ

    2012-03-01

    Full Text Available Fatigue behaviour of Atmofix 52 steel (comparable to COR-TENâ steel exposed to atmospheric corrosion for 20 years was investigated. S-N curves for load symmetrical cycling and cycling with stress ratio R = 0 were determined on specimens detracted from a failed transmission tower. The data were compared with those on material without a rust layer. The fracture surfaces and, in particular, the sites of fatigue crack initiation were analyzed. Substantial decrease of fatigue life and fatigue limit due to corrosion exposition was found. Based on observation of surface layer with corrosion products and on fractographic analysis of failed specimens conclusions on fatigue damage mechanism were drawn. No grain boundary corrosion, which can be responsible for fatigue crack initiation, was observed. Initiation of fatigue cracks was related to surface roughness and took place exclusively on corrosion dimples.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1335

  3. Fatigue Experiences Among OCD Outpatients.

    Science.gov (United States)

    Pasquini, Massimo; Piacentino, Daria; Berardelli, Isabella; Roselli, Valentina; Maraone, Annalisa; Tarsitani, Lorenzo; Biondi, Massimo

    2015-12-01

    Patients with OCD are impaired in multiple domains of functioning and quality of life. While associated psychopathology complaints and neuropsychological deficits were reported, the subjective experience of general fatigue and mental fatigue was scarcely investigated. In this single-center case-control study we compared 50 non-depressed OCD outpatients consecutively recruited and 50 panic disorder (PD) outpatients, to determine whether they experienced fatigue differently. Assessment consisted of structured clinical interview for DSM-IV criteria by using the SCID-I and the SCID-II. Symptom severity was assessed using the Yale-Brown Obsessive-Compulsive Scale, the Hamilton Anxiety Rating Scale, the Hamilton Depression Rating Scale, the Clinical Global Impressions Scale, severity and the Global Assessment of Functioning Scale. Fatigue was assessed by using the Multidimensional Fatigue Inventory (MFI). Regarding MFI physical fatigue, an OR of 0.196 (95 % CI 0.080-0.478) was found, suggesting that its presence is associated with lower odds of OCD compared to PD. The same can be said for MFI mental fatigue, as an OR of 0.138 (95 % CI 0.049-0.326) was found, suggesting that its presence is associated with lower odds of OCD. Notably, OCD patients with OCDP co-morbidity reported higher scores of mental fatigue. In this study fatigue, including mental fatigue, seems not to be a prominent experience among adult non-depressed OCD patients. PMID:25814268

  4. Creep-Fatigue Interaction Testing

    Science.gov (United States)

    Halford, Gary R.

    2001-01-01

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

  5. Fatigue in systemic lupus erythematosus.

    Science.gov (United States)

    Ahn, Grace E; Ramsey-Goldman, Rosalind

    2012-04-01

    Systemic lupus erythematosus is a chronic inflammatory autoimmune disease often characterized by fatigue, with significant effects on physical functioning and wellbeing. The definition, prevalence and factors associated with fatigue, including physical activity, obesity, sleep, depression, anxiety, mood, cognitive dysfunction, vitamin D deficiency/insufficiency, pain, effects of medications and comorbidities, as well as potential therapeutic options of fatigue in the systemic lupus erythematosus population are reviewed. Due to variability in the reliability and validity of various fatigue measures used in clinical studies, clinical trial data have been challenging to interpret. Further investigation into the relationships between these risk factors and fatigue, and improved measures of fatigue, may lead to an improvement in the management of this chronic inflammatory disease. PMID:22737181

  6. Compassion fatigue: a nurse's primer.

    Science.gov (United States)

    Lombardo, Barbara; Eyre, Caryl

    2011-01-01

    Most nurses enter the field of nursing with the intent to help others and provide empathetic care for patients with critical physical, mental, emotional, and spiritual needs. Empathic and caring nurses, however, can become victims of the continuing stress of meeting the often overwhelming needs of patients and their families, resulting in compassion fatigue. Compassion fatigue affects not only the nurse in terms of job satisfaction and emotional and physical health, but also the workplace environment by decreasing productivity and increasing turnover. We begin this article with a case study of a reactive nurse who did not seek help for her continuing stress. This is followed by a review of Watson's theoretical perspective related to compassion fatigue. Next we delineate symptoms of, and describe interventions for addressing compassion fatigue. We conclude by presenting a case study of a proactive nurse who avoided developing compassion fatigue and a discussion of future research needed to better prevent and ameliorate compassion fatigue. PMID:21800934

  7. 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.

  8. Fatigue properties of weathering steel

    OpenAIRE

    Zavadilová, Petra

    2012-01-01

    This work deals with the influence of atmospheric corrosion on high-cycle fatigue properties of a weathering steel ATMOFIX B. New experimental data on fatigue strength of a steel exposed for 20 years to an atmospheric corrosion were compared to those characterizing the base material. Reduction of the fatigue lifetime of the exposed material compared with the base material was predicted on the basic of fractographic examination of fracture surfaces and the influence of surface notches on fatig...

  9. Automotive stamped part fatigue design

    OpenAIRE

    Caudoux Mélanie; Facchinetti Matteo Luca; Raynal Renaud

    2014-01-01

    Fatigue design of automotive axle parts is of prior concern because of these are high safety parts and they are expected to drive the overall vehicle mass reduction. In this framework, the stamping process is widely used to form axle parts, before assembling them by welding. Consequently, the mechanical and physical characteristics of the blank sheet are modified, having a strong influence on the fatigue behavior. In this paper, we address the consequences of the stamped process on the fatigu...

  10. Occupational fatigue: Implications for aviation

    OpenAIRE

    Oliveira, Teresa Cristina Clímaco Monteiro d'

    2011-01-01

    Occupational fatigue has been considered a major contribution to decreases in well-being and performance in a variety of industries. The objective of the chapter is to review the main issues associated with occupational fatigue and to consider the implications for the globalized aviation industry. Fatigue management in aviation has been associated with rostering practices, countermeasures and the development of international regulations. Recently research has proposed that p...

  11. Fatigue of closed cell foams

    OpenAIRE

    Zenkert, Dan; Shipsha, Andrey; Burman, Magnus

    2006-01-01

    The static properties of foams scale with relative density and scaling can be obtained through various static tests. The same scaling appears to be valid for both crack propagation rates and fatigue properties of the foams. This implies that, once the fatigue behavior of one relative density foam is established, one can predict the fatigue behavior of all other density foams within the same class of materials. This study deals with fatigue of closed cell foams. The main idea is to use a few s...

  12. Nonlinear cumulative damage model for multiaxial fatigue

    Institute of Scientific and Technical Information of China (English)

    SHANG De-guang; SUN Guo-qin; DENG Jing; YAN Chu-liang

    2006-01-01

    On the basis of the continuum fatigue damage theory,a nonlinear uniaxial fatigue cumulative damage model is first proposed.In order to describe multiaxial fatigue damage characteristics,a nonlinear multiaxial fatigue cumulative damage model is developed based on the critical plane approach,The proposed model can consider the multiaxial fatigue limit,mean hydrostatic pressure and the unseparated characteristic for the damage variables and loading parameters.The recurrence formula of fatigue damage model was derived under multilevel loading,which is used to predict multiaxial fatigue life.The results showed that the proposed nonlinear multiaxial fatigue cumulative damage model is better than Miner's rule.

  13. Structural Considerations on Fatigue Cracks

    Directory of Open Access Journals (Sweden)

    Cornel Bit

    2015-07-01

    Full Text Available This paper has been focused on the modern theoretical and experimental investigations on fatigue of metals which are now largely concentrated on three important areas: fatigue crack nucleation, short crack growth and long crack propagation. The main differences concerning the short cracks and long cracks mechanical investigation analysis have been presented.

  14. Structural Considerations on Fatigue Cracks

    OpenAIRE

    Cornel Bit

    2015-01-01

    This paper has been focused on the modern theoretical and experimental investigations on fatigue of metals which are now largely concentrated on three important areas: fatigue crack nucleation, short crack growth and long crack propagation. The main differences concerning the short cracks and long cracks mechanical investigation analysis have been presented.

  15. [Compassion fatigue: a concept analysis].

    Science.gov (United States)

    Fu, Chia-Yun; Chen, Hsing-Mei

    2011-04-01

    Compassion fatigue is a relatively new term in nursing. This term describes mood swings experienced by healthcare providers that are both complex in origin and intensify over time due to cumulative stress. Quality of care can be affected if compassion fatigue goes untreated. This paper presents a concept analysis of compassion fatigue using Walker & Avant's method. Results show the defining attributes of compassion fatigue to include: 1. accumulated patient and family suffering; 2. sufferer unable to release built-up stresses effectively; and 3. negative effects on physical, psychological, and spiritual health. Identified antecedents of compassion fatigue included: (1) working as a healthcare provider; (2) investing sympathy in others over a long period of time; and (3) ignoring stress symptoms and personal emotional needs over time. Identified consequences of compassion fatigue included: (1) decreased coping ability; (2) damage / destruction of patient relationship; and (3) increased medical care costs. This study conducted a concept analysis to offer a better understanding of the concept of compassion fatigue and provide a reference for nursing practice and compassion fatigue-related nursing research. PMID:21455900

  16. 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....

  17. Fatigue monitoring in Nuclear Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Ware, A.G.; Shah, V.N. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)

    1995-04-01

    This paper summarizes fatigue monitoring methods and surveys their application in the nuclear power industry. The paper is based on a review of the technical literature. Two main reasons for fatigue monitoring are more frequent occurrence of some transients than that assumed in the fatigue design analysis and the discovery of stressors that were not included in the fatigue design analysis but may cause significant fatigue damage at some locations. One fatigue monitoring method involves use of plant operating data and procedures to update the fatigue usage. Another method involves monitoring of plant operating parameters using existing, or if needed, supplementary plant instrumentation for online computation of fatigue usage. Use of fatigue monitoring has better defined the operational transients. Most operational transients have been found less severe and fewer in numbers than anticipated in the design fatigue analysis. Use of fatigue monitoring has assisted in quantifying newly discovered stressors and has helped in detecting the presence of thermal stratification of unsuspected locations.

  18. Simplified elastoplastic fatigue analysis

    International Nuclear Information System (INIS)

    Oligocyclic fatigue behaviour is a function of the local strain range. The design codes ASME section III, RCC-M, Code Case N47, RCC-MR, and the Guide issued by PNC propose simplified methods to evaluate the local strain range. After having briefly described these simplified methods, we tested them by comparing the results of experimental strains with those predicted by these rules. The experiments conducted for this study involved perforated plates under tensile stress, notched or reinforced beams under four-point bending stress, grooved specimens under tensile-compressive stress, and embedded grooved beams under bending stress. They display a relative conservatism depending on each case. The evaluation of the strains of rather inaccurate and sometimes lacks conservatism. So far, the proposal is to use the finite element codes with a simple model. The isotropic model with the cyclic consolidation curve offers a good representation of the real equivalent strain. There is obviously no question of representing the cycles and the entire loading history, but merely of calculating the maximum variation in elastoplastic equivalent deformations with a constant-rate loading. The results presented testify to the good prediction of the strains with this model. The maximum equivalent strain will be employed to evaluate fatigue damage

  19. Bearing fatigue investigation 3

    Science.gov (United States)

    Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

    1982-01-01

    The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

  20. Fatigue and corrosion fatigue of beryllium-copper spring materials

    International Nuclear Information System (INIS)

    Fine gage, 0.006-in. d(0.15-mm) thick, beryllium-copper (Be-Cu) spring materials with tensile strength in the range of 70 to 145 ksi were subjected to cyclic loading in air and salt water environments. Plain and notched (center hole) hour glass specimens were subjected to sinusoidal loading with R = (minimum/maximum) stress = 0.1 at cyclic frequencies of 50 Hz in air and 1 Hz in salt water. Fatigue life was typically from 104 to 106 cycles with crack initiation as the dominant fatigue process. The excellence fatigue performance of Be-Cu alloys in salt water is well-known, however, current findings demonstrate 10 to 37% reduction in fatigue strength of unnotched specimens in this environment for a life of 3 x 105 cycles. This strength degradation is attributed to the use of a lower cyclic frequency for present than for previous tests, i.e., 1 versus about 20 Hz. There was no effect of salt water on crack initiation in notched specimens. The ratios of the fatigue strengths, namely (cold-rolled/annealed) and (aged/annealed), for plain and notched specimens tested in air, decreased from 2 to about 1.4 as fatigue life increased from 104 to 106 cycles. This effect is attributed to cyclic hardening of the annealed material. The fatigue stress concentration factor, Kf = (plain/notched) fatigue strength, increased by about 30% as fatigue cycles increased from 104 to 106. The ranking of Kf values of the various material conditions from highest to lowest was: cold-rolled, aged, and annealed

  1. Social loafing under fatigue.

    Science.gov (United States)

    Hoeksema-van Orden, C Y; Gaillard, A W; Buunk, B P

    1998-11-01

    In 2 experiments, 64 male students worked almost continuously for 20 hr without sleep under varying social conditions. In Experiment 1, participants worked either individually or as a group. As hypothesized, performance deteriorated over time, especially in the group condition, which allowed participants to loaf. In Experiment 2, all participants worked in groups. They were instructed that public feedback would be provided either on the group result only or on the individual results of all group members. As expected, when individual results were made public, performance deteriorated less. Overall, the data suggest that fatigue increases social loafing. However, both individualizing the task and providing public individual feedback seem to counteract these effects. PMID:9866183

  2. Fatigue of closed cell foams

    OpenAIRE

    Zenkert, Dan; Shipsha, Andrey; Burman, Magnus

    2005-01-01

    This paper deals with fatigue of closed cell foams. The main idea is to use a few simple tests to predict the tension-tension fatigue properties of foams. The required testing consists of crack propagation rate measurements and one tension-tension fatigue test performed at yield stress for the foam. This data can then be combined to construct a synthetic S-N Curve for the foam. Tests on three densities of Divinycell H-grade foam are performed and the results Support this approach. Some prelim...

  3. Mental fatigue detection using electrophysiological measurements

    OpenAIRE

    Laurent, François

    2010-01-01

    Three experiments were conducted to assess the feasibility of a mental fatigue detector that would exploit electrophysiological signals for discriminating time windows associated with a "fatigue" state of windows associated with a "no fatigue" state. In the first experiment, subjects performed a task switching task for about 2 h. Two segments of 20 min were selected for each subject. The first one was associated with the "no fatigue" state and the other one with the "fatigue" state. These seg...

  4. Fatigue in Parkinson disease: an integrative review.

    Science.gov (United States)

    Bruno, Amy E; Sethares, Kristen A

    2015-06-01

    Fatigue, one of the most prevalent and underassessed nonmotor symptoms in patients with Parkinson disease (PD), is reported to be a major cause of disability and reduced quality of life. The purpose of this review was to systematically examine the scientific literature and report how fatigue is defined and measured and what interventions are used to treat it. A synthesis of the current literature will expose the current state of the science of fatigue in PD, propose areas for future research, and offer practice implications. An integrative review of the literature was conducted. The electronic databases CINAHL, Psychinfo, and PUBMED were searched using the keywords "Parkinson's disease," "fatigue," "definition," "mental fatigue," "physical fatigue," "measurement," "interventions," "treatment," and "methylphenidate." One hundred fourteen articles were found. Nineteen studies met review criteria. No universal definition of fatigue in PD was found, making it difficult to measure. However, central, physical, mental, and peripheral fatigues were described. Six scales were found that measure fatigue in PD; only one specific to PD, the Parkinson Fatigue Scale, measured physical fatigue. Seven studies reported interventions to treat fatigue and were categorized as medication, exercise, and alternative interventions. None of these interventions had a significant effect on fatigue. Findings showed that (a) there is a lack of a universally accepted definition of fatigue because of its subjective nature, (b) existing fatigue measurement tools do not measure all types of fatigue in PD, and (c) no intervention had a significant effect on fatigue. There is a need to define and explore fatigue further using qualitative methods. Further development of instruments to measure fatigue in women, younger onset, and older adults with PD is needed. A focus on person-centered interventions to reduce fatigue in patients with PD is a research priority. PMID:25943995

  5. Fatigue, burnout, and chronic fatigue syndrome among employees on sick leave: do attributions make the difference?

    OpenAIRE

    Huibers, M.; Beurskens, A; J. Prins; Kant, I.; Bazelmans, E.; van Schayck, C. P.; Knottnerus, J; 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.

  6. 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 ... have trouble taking in nutrients during cancer treatment. Emotional stress. Having cancer can make you feel anxious, ...

  7. Nonlinear vibration caused by fatigue

    Science.gov (United States)

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

    2007-06-01

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

  8. 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...

  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 in primary Sjogren's syndrome

    NARCIS (Netherlands)

    P.J. Barendregt (Pieternella); M.R. Visser; 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 fat

  11. Fatigue properties in reactor water

    International Nuclear Information System (INIS)

    Results of research projects on the effect of reactor water environment on the fatigue properties of the pressure boundary materials have been reported in the literature for the last 20 years. These include projects to investigate effect on crack growth along with projects on crack initiation through studies of the S-N fatigue properties. Much has been learned in these studies about how the environment can influence the fatigue life of a material in an environment. Much still needs to be done, however, before this information can be applied to the analyses of actual structures. This presentation will present an overview of what is known concerning the interactions of the reactor environment with the pressure boundary materials that affect the fatigue properties of the material, a summary of current activities within the PVRC and a discussion of the work needed before the environmental effects can be effectively considered in the analysis of structures

  12. Fatigue reliability for LNG carrier

    Institute of Scientific and Technical Information of China (English)

    Xiao Taoyun; Zhang Qin; Jin Wulei; Xu Shuai

    2011-01-01

    The procedure of reliability-based fatigue analysis of liquefied natural gas (LNG) carrier of membrane type under wave loads is presented. The stress responses of the hotspots in regular waves with different wave heading angles and wave lengths are evaluated by global ship finite element method (FEM). Based on the probabilistic distribution function of hotspots' short-term stress-range using spectral-based analysis, Weibull distribution is adopted and discussed for fitting the long-term probabilistic distribution of stress-range. Based on linear cumulative damage theory, fatigue damage is characterized by an S-N relationship, and limit state function is established. Structural fatigue damage behavior of several typical hotspots of LNG middle ship section is clarified and reliability analysis is performed. It is believed that the presented results and conclusions can be of use in calibration for practical design and initial fatigue safety evaluation for membrane type LNG carrier.

  13. Human herpesvirus 6 and 7 are biomarkers for fatigue, which distinguish between physiological fatigue and pathological fatigue.

    Science.gov (United States)

    Aoki, Ryo; Kobayashi, Nobuyuki; Suzuki, Go; Kuratsune, Hirohiko; Shimada, Kazuya; Oka, Naomi; Takahashi, Mayumi; Yamadera, Wataru; Iwashita, Masayuki; Tokuno, Shinichi; Nibuya, Masashi; Tanichi, Masaaki; Mukai, Yasuo; Mitani, Keiji; Kondo, Kazuhiro; Ito, Hiroshi; Nakayama, Kazuhiko

    2016-09-01

    Fatigue reduces productivity and is a risk factor for lifestyle diseases and mental disorders. Everyone experiences physiological fatigue and recovers with rest. Pathological fatigue, however, greatly reduces quality of life and requires therapeutic interventions. It is therefore necessary to distinguish between the two but there has been no biomarker for this. We report on the measurement of salivary human herpesvirus (HHV-) 6 and HHV-7 as biomarkers for quantifying physiological fatigue. They increased with military training and work and rapidly decreased with rest. Our results suggested that macrophage activation and differentiation were necessary for virus reactivation. However, HHV-6 and HHV-7 did not increase in obstructive sleep apnea syndrome (OSAS), chronic fatigue syndrome (CFS) and major depressive disorder (MDD), which are thought to cause pathological fatigue. Thus, HHV-6 and HHV-7 would be useful biomarkers for distinguishing between physiological and pathological fatigue. Our findings suggest a fundamentally new approach to evaluating fatigue and preventing fatigue-related diseases. PMID:27396623

  14. The relationship between fatigue and sleep in cancer patients: a review

    OpenAIRE

    Ancoli-Israel, S.; Moore, P.J.; Jones, V.

    2001-01-01

    Fatigue is a major complaint among cancer patients, yet it is unknown whether cancer-related fatigue experienced during the day relates to sleep/wake cycles or to the quality and quantity of sleep obtained at night. Although it is not well defined or well understood at present, cancer-related fatigue is generally regarded as a form of tiredness that does not improve following rest or sleep. Objectively recorded sleep and biological rhythms have not been well investigated in these patients, bu...

  15. Fatigue Strain and Damage Analysis of Concrete in Reinforced Concrete Beams under Constant Amplitude Fatigue Loading

    OpenAIRE

    Fangping Liu; Jianting Zhou

    2016-01-01

    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 equation...

  16. Automotive stamped part fatigue design

    Directory of Open Access Journals (Sweden)

    Caudoux Mélanie

    2014-06-01

    Full Text Available Fatigue design of automotive axle parts is of prior concern because of these are high safety parts and they are expected to drive the overall vehicle mass reduction. In this framework, the stamping process is widely used to form axle parts, before assembling them by welding. Consequently, the mechanical and physical characteristics of the blank sheet are modified, having a strong influence on the fatigue behavior. In this paper, we address the consequences of the stamped process on the fatigue design and how they may be effectively taken into account in the automotive industry. Actually, the coupling between the stamping process and the fatigue design is under development at PSA Peugeot Citroën Company since several years. Such an analysis deals with some major topics: thickness variation, plastic hardening and deformation, and residual stress. All of these ingredients result in fatigue criteria evolutions: it is important to stress that the stamping process can have advantageous or disadvantageous consequences on the fatigue design. This is here highlighted on some examples, dealing with front and rear axles.

  17. Astragalus membranaceus Improves Exercise Performance and Ameliorates Exercise-Induced Fatigue in Trained Mice

    OpenAIRE

    Tzu-Shao Yeh; Hsiao-Li Chuang; Wen-Ching Huang; Yi-Ming Chen; Chi-Chang Huang; Mei-Chich Hsu

    2014-01-01

    Astragalus membranaceus (AM) is a popular “Qi-tonifying” herb with a long history of use as a Traditional Chinese Medicine with multiple biological functions. However, evidence for the effects of AM on exercise performance and physical fatigue is limited. We evaluated the potential beneficial effects of AM on ergogenic and anti-fatigue functions following physiological challenge. Male ICR strain mice were randomly assigned to four groups (n = 10 per group) for treatment: (1) sedentary control...

  18. Corrosion fatigue properties of thermally insulated pipeline

    International Nuclear Information System (INIS)

    The corrosion fatigue properties of thermally insulated pipeline were investigated in synthetic groundwater by electrochemical test, corrosion fatigue test and SEM analysis. Since the potential difference between the weldment and the base metal was small, the pipeline steel was not susceptible to galvanic corrosion. No fatigue limit was apparent for corrosion fatigue testing with remarkable reduction of fatigue lifetime. The effects of insulation and stress on the corrosion fatigue resistance of pipeline steel were studied through Linear Polarization Resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) during corrosion fatigue testing. The result of LPR measurement indicated that the corrosion rate was determined not by the water content of PUR foam but by the magnitude of applied stress. The better corrosion fatigue property of the insulated steel was attributable to the formation of a protective rust layer under the insulation, which reduced the acceleration of corrosion process and the propagation of fatigue crack. This was confirmed by the results of EIS measurements and SEM observation

  19. 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.

  20. Fatigue after Stroke: The Patient's Perspective

    Directory of Open Access Journals (Sweden)

    Victoria Louise Barbour

    2012-01-01

    Full Text Available Background. Fatigue after stroke is common and distressing to patients. Aims. Our aims were to explore patients' perceptions of post-stroke fatigue, including the causes of fatigue and the factors that alleviate fatigue, in a mixed methods study. Results. We interviewed 15 patients who had had a stroke and were inpatients on stroke rehabilitation wards. A substantial proportion of patients reported that their fatigue started at the time of their stroke. Various different factors were reported to improve fatigue, including exercise, good sleep, rehabilitation and rest. Fatigue influences patients' sense of “control” after their stroke. Conclusion. Our results are consistent with the possibility that poststroke fatigue might be triggered by factors that occur at the time of the stroke (e.g., the stroke lesion itself, or admission to hospital and then exacerbated by poor sleep and boredom. These factors should be considered when developing complex interventions to improve post-stroke fatigue.

  1. Traditional Chinese Medicine for Chronic Fatigue Syndrome

    Directory of Open Access Journals (Sweden)

    Rui Chen

    2010-01-01

    Full Text Available More and more patients have been diagnosed as having chronic fatigue syndrome (CFS in recent years. Western drug use for this syndrome is often associated with many side-effects and little clinical benefit. As an alternative medicine, traditional Chinese medicine (TCM has provided some evidences based upon ancient texts and recent studies, not only to offer clinical benefit but also offer insights into their mechanisms of action. It has perceived advantages such as being natural, effective and safe to ameliorate symptoms of CFS such as fatigue, disordered sleep, cognitive handicaps and other complex complaints, although there are some limitations regarding the diagnostic standards and methodology in related clinical or experimental studies. Modern mechanisms of TCM on CFS mainly focus on adjusting immune dysfunction, regulating abnormal activity in the hypothalamic-pituitary-adrenal (HPA axis and serving as an antioxidant. It is vitally important for the further development to establish standards for ‘zheng’ of CFS, i.e. the different types of CFS pathogenesis in TCM, to perform randomized and controlled trials of TCM on CFS and to make full use of the latest biological, biochemical, molecular and immunological approaches in the experimental design.

  2. 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 forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

  3. 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.

  4. Fatigue crack initiation life prediction of railroad

    International Nuclear Information System (INIS)

    Study of multiaxial high-cycle fatigue initiation life prediction for railroad is done in this paper. Using ANSYS 11.0 software three dimensional elasto-plastic finite element model of rail/wheel contact is constructed and fine mesh technique in contact region is used to achieve both computational efficiency and accuracy. Stress analysis is performed and fatigue damage in railroad is evaluated numerically using multiaxial fatigue crack initiation model. Using the stress history during one loading cycle and fatigue damage model, the effects of vertical loading, material hardness material fatigue properties and wheel/rail contact situation on fatigue crack initiation life are investigated.

  5. Fatigue Properties of Supersteel for Automobiles

    Institute of Scientific and Technical Information of China (English)

    DU Lin-xiu; ZHANG Zhong-ping; TIAN Yu-wei; LIU Xiang-hua; WANG Guo-dong

    2006-01-01

    The fatigue properties of 400 MPa grade supersteel, plain low carbon steel SS400 and microalloyed steel Q340TM were investigated through tensile-compression fatigue experiment with R=-1. The results indicate that the fatigue limit of the 400 MPa supersteel is higher than that of SS400 steel and close to that of the 340TM steel. According to the analysis of fatigue fracture, the fatigue striations of supersteel SS400 is thinner than that of SS400 steel and 340TM steel, and grain refinement can increase the fatigue limit.

  6. High speed rails. Fatigue behaviour

    International Nuclear Information System (INIS)

    In recent years, passenger train speed and freight train load have increased to enhance efficiency of rail road transportation. These trends have increased the severity of rail service conditions, calling for rails with greater wear resistance, strength and fatigue behaviour. In the United Stated and Europe, track site weld rails are made entirely by aluminothermic process. This work describes the results of experimental study conducted on bending fatigue strength of plain rails and aluminothermic welded rails with preheating procedures (oxipropane and air-induced propane) approved by railways authorities. Compliance with the required fatigue strength shall be ascertained by 4 point pulsating bending test in accordance with European standards by aluminothermic welding in rails. The locati method, based in the empirical Miner's law about the cumulative damage on a fatigue tested material, allows, once known the Wohler curve of the welding process in use to settle the fatigue tensile limit at 50% with only one test. The values obtained at 2.10''6 cycles for plain rails (Sf=353 MPa), oxipropane preheated aluminothermic weld rails (Sf=225 MPa), and propane-air induced aluminothermic weld rails (Sf=210 MPa) are very similar to those resulting from test method stated in the European Standard. From our point of view and due to its ease, speediness and savings, this is the most suitable test to check the quality and compare the aluminothermic processes in use. (Author) 15 refs

  7. 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. PMID:27466935

  8. 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 ischemia leading to a 7% or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

  9. 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.

  10. 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...... was used to investigate dimensionality, monotonicity, and invariant item ordering (IIO). In both age groups, as well as by gender, the Motivation domain presented with weak scalability, suggesting that caution be exercised when interpreting sum scores. For all groupings, the strongest scaling...

  11. Chronic Fatigue Syndrome (CFS): Who's at Risk?

    Science.gov (United States)

    ... please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Who's at Risk? More ... explore this possibility Related Links Disability and Chronic Fatigue Syndrome Print page View page in: Español (Spanish) ...

  12. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart A.; 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 %22remaining life%22 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.

  13. 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).

  14. Fatigue Risk Management: A Maritime Framework

    OpenAIRE

    Michelle Rita Grech

    2016-01-01

    It is evident that despite efforts directed at mitigating the risk of fatigue through the adoption of hours of work and rest regulations and development of codes and guidelines, fatigue still remains a concern in shipping. Lack of fatigue management has been identified as a contributory factor in a number of recent accidents. This is further substantiated through research reports with shortfalls highlighted in current fatigue management approaches. These approaches mainly focus on prescriptiv...

  15. PROBABILISTIC METHODOLOGY OF LOW CYCLE FATIGUE ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    Jin Hui; Wang Jinnuo; Wang Libin

    2003-01-01

    The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analy sis. The randomness of loading and the theory of fatigue damage accumulation (TOFDA) are consid ered. The probabilistic analysis of local stress, local strain and fatigue life are constructed based on the first-order Taylor's series expansions. Through this method proposed fatigue reliability analysis can be accomplished.

  16. Understanding Muscle Dysfunction in Chronic Fatigue Syndrome

    OpenAIRE

    Gina Rutherford; Philip Manning; Newton, Julia L

    2016-01-01

    Introduction. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a debilitating disorder of unknown aetiology, characterised by severe disabling fatigue in the absence of alternative diagnosis. Historically, there has been a tendency to draw psychological explanations for the origin of fatigue; however, this model is at odds with findings that fatigue and accompanying symptoms may be explained by central and peripheral pathophysiological mechanisms, including effects of the immune...

  17. The nature of fatigue damage in bone

    OpenAIRE

    Lee, T Clive; O'Brien, Fergal J.; Taylor, David

    2000-01-01

    Bone is unusual among structural materials as it is alive and capable of self-repair. Fatigue-induced microdamage is repaired by bone remodelling, but if damage accumulates too quickly, or remodelling is deficient, fatigue failure may result. Fatigue is thought to contribute to both stress and fragility fractures which are of major clinical importance. Despite this, we do not fully understand the nature of fatigue damage in bone. Human rib sections, containing microcracks stained with basic f...

  18. Biomarkers of peripheral muscle fatigue during exercise

    OpenAIRE

    Finsterer Josef

    2012-01-01

    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 oxid...

  19. Polarization fatigue of organic ferroelectric capacitors

    OpenAIRE

    Dong Zhao; Ilias Katsouras; Mengyuan Li; Kamal Asadi; Junto Tsurumi; Gunnar Glasser; Jun Takeya; Blom, Paul W. M.; de Leeuw, Dago M.

    2014-01-01

    The polarization of the ferroelectric polymer P(VDF-TrFE) decreases upon prolonged cycling. Understanding of this fatigue behavior is of great technological importance for the implementation of P(VDF-TrFE) in random-access memories. However, the origin of fatigue is still ambiguous. Here we investigate fatigue in thin-film capacitors by systematically varying the frequency and amplitude of the driving waveform. We show that the fatigue is due to delamination of the top electrode. The origin i...

  20. Mental Fatigue Affects Visual Selective Attention

    OpenAIRE

    Faber, Léon 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 attention-related changes in event-related potentials (ERPs). EEG, reaction times and response accuracies were obtained from 17 healthy volunteers during two hours of task performance on an adapted Eriksen...

  1. Inflammation and cancer-related fatigue: mechanisms, contributing factors, and treatment implications.

    Science.gov (United States)

    Bower, Julienne E; Lamkin, Donald M

    2013-03-01

    Fatigue is one of the most common and distressing side effects of cancer and its treatment, and may persist for years after treatment completion in otherwise healthy survivors. Guided by basic research on neuro-immune interactions, a growing body of research has examined the hypothesis that cancer-related fatigue is driven by activation of the pro-inflammatory cytokine network. In this review, we examine the current state of the evidence linking inflammation and cancer-related fatigue, drawing from recent human research and from experimental animal models probing effects of cancer and cancer treatment on inflammation and fatigue. In addition, we consider two key questions that are currently driving research in this area: what are the neural mechanisms of fatigue, and what are the biological and psychological factors that influence the onset and/or persistence of inflammation and fatigue in cancer patients and survivors? Identification of the mechanisms driving cancer-related fatigue and associated risk factors will facilitate the development of targeted interventions for vulnerable patients. PMID:22776268

  2. SIMULATION OF COMPLEX THERMOMECHANICAL FATIGUE

    Institute of Scientific and Technical Information of China (English)

    R.Bardenheier; G.Rogers

    2004-01-01

    Two different types of experimental techniques to perform non-isothermal, unicxial and biaxial fatigue testa were described. A new miniaturised electrothermalmechanical test rig was presented and discussed. It enables testing of small specimens under complex thermomechanical loading conditions. In order to cope with the simulation of well defined biaxial proportional and non-proportional loadings with in-phase and out-of-phase superposition of thermal loads a cruciform biaxial fatigue testing machine has been developed. Special design features of both machines, and the specimens tested, as well as typical test results were discussed.

  3. [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

  4. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

    Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...

  5. 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 conservativ

  6. Fatigue Analysis and Life Prediction of Dumpers with Cumulative Fatigue Damage Approach

    Institute of Scientific and Technical Information of China (English)

    LI Shouju; LIU Yingxi; SUN Huiling

    2004-01-01

    A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.

  7. Fatigue Severity and Factors Associated with High Fatigue Levels in Korean Patients with Inflammatory Bowel Disease

    Science.gov (United States)

    Yoo, Suhyeon; Jung, Yoon Suk; Park, Jung Ho; Kim, Hong Joo; Cho, Yong Kyun; Sohn, Chong Il; Jeon, Woo Kyu; Kim, Byung Ik

    2014-01-01

    Background/Aims Many patients with inflammatory bowel disease (IBD) often complain of fatigue. To date, only a few studies in Western countries have focused on fatigue related to IBD, and fatigue has never been specifically studied in Asian IBD patients. The aim of the present study was to investigate the fatigue level and fatigue-related factors among Korean IBD patients. Methods Patients in remission or with mild to moderate IBD were included. Fatigue was assessed using the Functional Assessment of Chronic Illness Therapy-Fatigue and the Brief Fatigue Inventory. Corresponding healthy controls (HCs) also completed both fatigue questionnaires. Results Sixty patients with Crohn disease and 68 patients with ulcerative colitis (UC) were eligible for analysis. The comparison group consisted of 92 HCs. Compared with the HCs, both IBD groups were associated with greater levels of fatigue (p<0.001). Factors influencing the fatigue score in UC patients included anemia and a high erythrocyte sedimentation rate (ESR). Conclusions Greater levels of fatigue were detected in Korean IBD patients compared with HCs. Anemia and ESR were determinants of fatigue in UC patients. Physicians need to be aware of fatigue as one of the important symptoms of IBD to better understand the impact of fatigue on health-related quality of life. PMID:24672655

  8. Hormone levels in radiotherapy treatment related fatigue

    International Nuclear Information System (INIS)

    Radiotherapy is known to cause debilitating treatment related fatigue. Fatigue in general is a conglomeration of psychological, physical, hematological and unknown factors influencing the internal milieu of the cancer patient. Radiotherapy can add stress at the cellular and somatic level to aggravate further fatigue in cancer patients undergoing radiotherapy. Stress related hormones might be mediating in the development of fatigue. This is an ongoing prospective study to evaluate if the hormonal profile related to stress is influenced by radiotherapy treatment related fatigue. The study was conducted from September 2002 onwards in the division of Radiotherapy and Oncology of our Medical School. Previously untreated patients with histopathology proof of malignancy requiring external beam radiotherapy were considered for this study. Selection criteria were applied to exclude other causes of fatigue. Initial fatigue score was obtained using Pipers Fatigue Score questionnaire containing 23 questions, subsequently final fatigue score was obtained at the end of radiotherapy. Blood samples were obtained to estimate the levels of ACTH, TSH, HGH, and cortisol on the final assessment. The hormone levels were compared with resultant post radiotherapy fatigue score. At the time of reporting 50 patients were evaluable for the study. The total significant fatigue score was observed among 12 (24%) patients. The individual debilitating fatigue score were behavioral severity 14 (28%), affective meaning 14(28%), Sensory 13 (26%) and cognitive mood 10 (20%) respectively. From the analysis of hormonal profile, growth hormone level > 1 ng/mL and TSH <0.03 appears to be associated with high fatigue score (though statistically not significant); whereas there was no correlation with ACTH and serum cortisol level. In our prospective study severe radiotherapy treatment related fatigue was found among our patient population. Low levels of TSH and high levels of GH appear to be associated

  9. MULTIAXIAL FATIGUE OF A RAILWAY WHEEL STEEL

    OpenAIRE

    CHIN-SUNG CHUNG; HO-KYUNG KIM

    2015-01-01

    Uniaxial and biaxial torsional fatigue specimens were extracted from a railway wheel steel. The fatigue tests were performed with the stress ratio of R= -1 by using uniaxial and biaxial torsional fatigue test specimens at room temperature in air. The ultimate and yield strengths of the steel were evaluated. The uniaxial fatigue limit was 422.5 MPa, which corresponds to 67% of the ultimate tensile strength. The ratio of e  e  / was 0.63. Appropriate parameters to predict the fatigue life ...

  10. Fatigue in traffic : causes and effects.

    OpenAIRE

    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 conservative estimate based on studies abroad, driver fatigue is involved in 10-15% of all severe crashes. Although technical aids to prevent fatigue crashes are being developed, they are not yet ready for us...

  11. Variable amplitude fatigue, modelling and testing

    International Nuclear Information System (INIS)

    Problems related to metal fatigue modelling and testing are here treated in four different papers. In the first paper different views of the subject are summarised in a literature survey. In the second paper a new model for fatigue life is investigated. Experimental results are established which are promising for further development of the mode. In the third paper a method is presented that generates a stochastic process, suitable to fatigue testing. The process is designed in order to resemble certain fatigue related features in service life processes. In the fourth paper fatigue problems in transport vibrations are treated

  12. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the...... propagation stage. The consequences of this behaviour on the fatigue reliability are discussed....

  13. Fatigue damage of nuclear facilities

    International Nuclear Information System (INIS)

    The conference on the fatigue damage of nuclear facilities, organized by the SFEN (french society of nuclear energy), took place at Paris the 23. of november 2000. Eleven papers were presented, showing the state of the art and the research programs in the domain of the sizing rules, safety, installations damage, examination and maintenance. (A.L.B.)

  14. Fatigue failure of coated structures

    Czech Academy of Sciences Publication Activity Database

    Knésl, Zdeněk; Náhlík, Luboš; Bareš, Pavel

    Riga : Institute of polymer mechanics, University of Latvia, 2006. s. 92-92. [Mechanics of Composite Materials. 29.05.2006-02.06.2006, Riga] R&D Projects: GA ČR GP106/04/P084 Institutional research plan: CEZ:AV0Z20410507 Keywords : protective coatings * interface Subject RIV: JL - Materials Fatigue, Friction Mechanics

  15. 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...

  16. "Holocaust Fatigue" in Teaching Today

    Science.gov (United States)

    Schweber, Simone

    2006-01-01

    In this article, the author discusses the problems faced by educators in teaching about the Holocaust. She relates that because the Holocaust is now frequently taught in middle schools and in upper elementary grades, by the time it is taught in high schools, students will experience "Holocaust fatigue." As such, teachers face the challenge of…

  17. A Transcriptional Signature of Fatigue Derived from Patients with Primary Sjogren's Syndrome.

    Directory of Open Access Journals (Sweden)

    Katherine James

    Full Text Available Fatigue is a debilitating condition with a significant impact on patients' quality of life. Fatigue is frequently reported by patients suffering from primary Sjögren's Syndrome (pSS, a chronic autoimmune condition characterised by dryness of the eyes and the mouth. However, although fatigue is common in pSS, it does not manifest in all sufferers, providing an excellent model with which to explore the potential underpinning biological mechanisms.Whole blood samples from 133 fully-phenotyped pSS patients stratified for the presence of fatigue, collected by the UK primary Sjögren's Syndrome Registry, were used for whole genome microarray. The resulting data were analysed both on a gene by gene basis and using pre-defined groups of genes. Finally, gene set enrichment analysis (GSEA was used as a feature selection technique for input into a support vector machine (SVM classifier. Classification was assessed using area under curve (AUC of receiver operator characteristic and standard error of Wilcoxon statistic, SE(W.Although no genes were individually found to be associated with fatigue, 19 metabolic pathways were enriched in the high fatigue patient group using GSEA. Analysis revealed that these enrichments arose from the presence of a subset of 55 genes. A radial kernel SVM classifier with this subset of genes as input displayed significantly improved performance over classifiers using all pathway genes as input. The classifiers had AUCs of 0.866 (SE(W 0.002 and 0.525 (SE(W 0.006, respectively.Systematic analysis of gene expression data from pSS patients discordant for fatigue identified 55 genes which are predictive of fatigue level using SVM classification. This list represents the first step in understanding the underlying pathophysiological mechanisms of fatigue in patients with pSS.

  18. Dynamic fatigue of feldspathic porcelain.

    Science.gov (United States)

    Fairhurst, C W; Lockwood, P E; Ringle, R D; Twiggs, S W

    1993-07-01

    Several studies (Sherrill and O'Brien, 1974; Southan and Jørgensen, 1974; Jones, 1983) have shown that stress corrosion fatigue occurs in dental porcelains. Morena et al. (1986) reported on an assessment of slow crack growth parameters for dental ceramics. The purpose of the study reported here was to evaluate the fatigue parameters of a model experimental porcelain using dynamic fatigue testing. This test procedure makes use of several constant stressing rates to perform strength tests. Dynamic stress testing was first described by Evans (1974) and later defined as a distinct test modality by Ritter (1978). From such data, the fatigue parameters can be calculated. These fatigue parameters, n and sigma f0, are, respectively, the crack growth exponent from the crack velocity expression and a materials constant which is dependent on the test environment and the inert (moisture-free) strength. The model porcelain was made from 60% component 1 and 40% component 3 according to the Weinstein patent (Weinstein, et al., 1962). The biaxial flexure strength of 300 specimens 1 mm thick was tested in 37 degrees C water by testing 50 samples at each of 6 constant stressing rates: 100, 10, 1, 0.1, 0.01, and 0.001 MPa/s. One hundred specimens were tested in a moisture-free environment at 100 MPa/s using a servo-mechanical testing machine. A commercial porcelain (Jelenko Gingival-Lot # 2012, Jelenko Dental Health Products, Armonk, NY, USA) was chosen as a reference material. One hundred twenty specimens were tested using the same procedures as those used for the model porcelain; however, only 20 samples were tested for 5 stressing rate groups and an inert group.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7988760

  19. Fatigue and Depressive Symptoms in Older People

    DEFF Research Database (Denmark)

    Mänty, Minna; Rantanen, Taina; Era, Pertti; Avlund, Kirsten

    2014-01-01

    Fatigue is considered an important indicator of aging-related declines in health and functional abilities. Previous studies have indicated strong associations between fatigue and depressive symptoms among younger populations and in patient groups with specific diseases. However, it is not known how...... different measures of fatigue are associated with depressive symptoms among general older populations. The purpose of this study is to describe the prevalence of depressive symptoms among community-dwelling older adults reporting mobility-related or general feelings fatigue. The study population consisted...... of 75-year-old community-living individuals (n = 561). Both, mobility-related and general fatigue, were associated in a stepwise relationship with depressive symptoms: a higher level of fatigue was related to higher level of depressive symptoms. Especially major general fatigue was strongly...

  20. Fatigue processes in thermoplastic fibres; Les mecanismes de fatigue dans les fibres thermoplastiques

    Energy Technology Data Exchange (ETDEWEB)

    Herrera Ramirez, J.M.

    2004-09-15

    The present study examines and compares the behaviour of the two types of PA66 fibres and two types of PET fibres under fatigue loading up to failure, and the correlation between the fibres (nano)structures and their structural heterogeneities, with fatigue lifetimes. Several techniques have been used to analyze the materials, such as scanning electron microscopy (SEM), microanalysis (EDS), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and micro-Raman spectroscopy. A meticulous analysis by scanning electron microscopy of the fracture morphology of fibres broken in tension and in fatigue, as well as a study of the fatigue life, were undertaken. The fatigue process occurs when the cyclic load amplitude is sufficiently large, however a condition for fatigue failure is that the minimum load each cycle must be lower than a threshold stress level. Failure under fatigue conditions leads to distinctive fracture morphologies which are very different from those seen after tensile or creep failure and this allows easy identification of the fatigue process. The fibres have been analyzed in the as received state and after fatigue failure in order to observe the microstructural changes resulting from the fatigue loading. The results will be compared with those obtained for fibres loaded under conditions where the fatigue process was hindered. The role of the microstructure of the fibres in determining fatigue will be discussed in this work and the possibility of improving their resistance to fatigue or eliminating the fatigue process will be discussed. (author)

  1. A Randomized Controlled Trial of Qigong Exercise on Fatigue Symptoms, Functioning, and Telomerase Activity in Persons with Chronic Fatigue or Chronic Fatigue Syndrome

    OpenAIRE

    Ho, Rainbow T. H.; Chan, Jessie S. M.; Wang, Chong-Wen; Lau, Benson W. M.; So, Kwok Fai; Yuen, Li Ping; Sham, Jonathan S. T.; Chan, Cecilia L. W.

    2012-01-01

    BACKGROUND: Chronic fatigue is common in the general population. Complementary therapies are often used by patients with chronic fatigue or chronic fatigue syndrome to manage their symptoms. PURPOSE: This study aimed to assess the effect of a 4-month qigong intervention program among patients with chronic fatigue or chronic fatigue syndrome. METHODS: Sixty-four participants were randomly assigned to either an intervention group or a wait list control group. Outcome measures included fatigue s...

  2. Investigating the effects of exam length on performance and cognitive fatigue.

    Directory of Open Access Journals (Sweden)

    Jamie L Jensen

    Full Text Available This study examined the effects of exam length on student performance and cognitive fatigue in an undergraduate biology classroom. Exams tested higher order thinking skills. To test our hypothesis, we administered standard- and extended-length high-level exams to two populations of non-majors biology students. We gathered exam performance data between conditions as well as performance on the first and second half of exams within conditions. We showed that lengthier exams led to better performance on assessment items shared between conditions, possibly lending support to the spreading activation theory. It also led to greater performance on the final exam, lending support to the testing effect in creative problem solving. Lengthier exams did not result in lower performance due to fatiguing conditions, although students perceived subjective fatigue. Implications of these findings are discussed with respect to assessment practices.

  3. Investigating the effects of exam length on performance and cognitive fatigue.

    Science.gov (United States)

    Jensen, Jamie L; Berry, Dane A; Kummer, Tyler A

    2013-01-01

    This study examined the effects of exam length on student performance and cognitive fatigue in an undergraduate biology classroom. Exams tested higher order thinking skills. To test our hypothesis, we administered standard- and extended-length high-level exams to two populations of non-majors biology students. We gathered exam performance data between conditions as well as performance on the first and second half of exams within conditions. We showed that lengthier exams led to better performance on assessment items shared between conditions, possibly lending support to the spreading activation theory. It also led to greater performance on the final exam, lending support to the testing effect in creative problem solving. Lengthier exams did not result in lower performance due to fatiguing conditions, although students perceived subjective fatigue. Implications of these findings are discussed with respect to assessment practices. PMID:23950918

  4. Fatigue of Dental Implants: Facts and Fallacies

    Directory of Open Access Journals (Sweden)

    Keren Shemtov-Yona

    2016-05-01

    Full Text Available Dental implants experience rare yet problematic mechanical failures such as fracture that are caused, most often, by (time-dependent metal fatigue. This paper surveys basic evidence about fatigue failure, its identification and the implant’s fatigue performance during service. We first discuss the concept of dental implant fatigue, starting with a review of basic concepts related to this failure mechanism. The identification of fatigue failures using scanning electron microscopy follows, to show that this stage is fairly well defined. We reiterate that fatigue failure is related to the implant design and its surface condition, together with the widely varying service conditions. The latter are shown to vary to an extent that precludes devising average or representative conditions. The statistical nature of the fatigue test results is emphasized throughout the survey to illustrate the complexity in evaluating the fatigue behavior of dental implants from a design perspective. Today’s fatigue testing of dental implants is limited to ISO 14801 standard requirements, which ensures certification but does not provide any insight for design purposes due to its limited requirements. We introduce and discuss the random spectrum loading procedure as an alternative to evaluate the implant’s performance under more realistic conditions. The concept is illustrated by random fatigue testing in 0.9% saline solution.

  5. Experimental study on creep-fatigue loading history effect

    International Nuclear Information System (INIS)

    In order to extend the applicability of a creep-fatigue life prediction method based on the overstress to a loading history effect, a series of creep-fatigue tests has been conducted with 316FR stainless steel at 923K in a high vacuum environment. The creep-fatigue test program includes changes of strain wave form: changed from creep-fatigue type to fatigue type and that from fatigue type to creep-fatigue type. Additional tests have been conducted to simulate an effect of a safe shutdown earthquake (SSE) on a creep-fatigue. A fatigue type strain cycling with a large strain range from 50 to 120 cycles is introduced into the creep-fatigue cycling. It was experimentally investigated how the fatigue loading with a larger strain range affects the total creep-fatigue life. In these tests the conventional linear cumulative damage rule is used in evaluating the creep-fatigue life under the complex loading history

  6. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

    This study is centred on assessment of the fatigue strength of titanium fusion welds for deep-water riser's applications. Deep-water risers are subjected to significant fatigue loading. Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments. The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechanics modelling of fatigue crack growth. Two series of welded grade of titanium consisting of 14 specimens in each series were fatigue tested under constant amplitude loading. Prior to fatigue testing, strain gauge measurements of some specimens was conducted to enable the definition of stress range in the fatigue assessment procedure. The results were compared with finite solid element analysis and related to fatigue stresses in a riser pipe wall. Distribution and geometry of internal and surface defects both in the as-welded and in the post-weld machined conditions were assessed using fractography. This served as a tool to determine the fatigue initiation point in the welds. Fracture mechanics was applied to model fatigue strength of titanium welds with initiation from weld defects. Two different stress intensity factor formulations for embedded eccentrically placed cracks were used for analysis of elliptical cracks with the major axis parallel and close to one of the free surfaces. The methods were combined to give a satisfactory model for crack growth analysis. The model analyses crack growth of elliptical and semi-elliptical cracks in two directions, with updating of the crack geometry. Fatigue strength assessment was conducted using two crack growth models, the Paris-Erdogan relation with no threshold and the Donahue et al. relation with an implied threshold. The model was validated against experimental data, with a discussion on the choice of crack growth model. (author)

  7. 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...... of the maximum number of load cycles performed before experiment termination. The approach utilizes to a large extent standard statistical and decision theoretical tools and is formulated such that the necessary calculations are easily performed using nested FORM/SORM. The suggested approach is illustrated...

  8. Impact of IL-1 inhibition on fatigue associated with autoinflammatory syndromes.

    Science.gov (United States)

    Yadlapati, Sujani; Efthimiou, Petros

    2016-01-01

    Cryopyrin-associated periodic syndromes (CAPS) is a rare group of autoinflammatory disorders that includes familial cold autoinflammatory syndrome or FCAS, Muckle-wells syndrome or MWS, and neonatal-onset multisystem inflammatory disease or NOMID. CAPS is caused by a mutation in the NOD-like receptor family, pyrin domain containing 3 (NLRP3) gene. This ultimately leads to increased production of interleukin (IL)-1β. IL-1β is a biologically active member of the IL-1 family. It is not only a pro-inflammatory cytokine responsible for features such as fever, rash, and arthritis, but is also a major mediator in the central pathways of fatigue. Fatigue is a major component of CAPS and is associated with severely compromised quality of life. In clinical studies, fatigue was measured using functional assessment of chronic illness therapy-fatigue or FACIT-F and short form-36 or SF-36, physical component score instruments. These questionnaires can also be used to monitor improvement of fatigue following initiation of therapy. IL-1 inhibitors block the IL-1 signaling cascade, thereby preventing systemic inflammation in CAPS. The decrease in systemic inflammation is accompanied by improvement in fatigue. PMID:26140469

  9. IEA Joint Action. Wind turbine fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B. [ed.

    1996-09-01

    Fatigue research on wind turbine blade material has been an important issue over the years in many countries and in the E.U. As a result of the effort the knowledge on fatigue properties of fibre reinforced materials has been expanded enormously. Practical fatigue design properties are available for constant amplitude tests at ambient temperatures. A lack of knowledge can be shown in several other fields, such as variable amplitude and multi-axial testing and the influence of the environment and carbon fibres. Fatigue is seen as dominant for the blade design, improvements in both the load prediction and material fatigue properties should be strove for. In discussions with blade manufacturers and subsidy agencies (E.U. DGXII, NOVEM, ETSU, etc.) on the importance of continuous materials fatigue research the improvement in reliability should be stressed. (au)

  10. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from Miner's rule will depend......Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...... types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel with a yield stress of ~ 360-410 MPa or high-strength steel with a yield stress of ~ 810-1010 MPa. The fatigue tests and the fracture mechanics analyses...

  11. Adults living with heart failure and fatigue

    DEFF Research Database (Denmark)

    Schjødt, Inge; Sommer, Irene; Bjerrum, Merete

    studies have been performed to develop more coherent and effective interventions to support self-care among heart failure patients experiencing fatigue. The findings of qualitative research should be synthesised to optimise nurses' understanding of fatigue and develop recommendations for practice. Aim To...... describe their experiences of fatigue? • How do patients with HF perceive the impact of fatigue in everyday life? • How do patients with HF manage fatigue and its consequences in everyday life? Methods A systematic literature search for published and unpublished studies 1995-2012 was carried out from...... October 2012 - ????. Search terms were “heart failure”, “fatigue” and “experience”. Studies were included if they explored the experiences and management of fatigue in everyday life among adult patients with HF, included non-hospitalised adult patients with confirmed HF or outpatients in a HF clinic. The...

  12. JSME code on environmental fatigue evaluation method

    International Nuclear Information System (INIS)

    The phenomena that the fatigue lives of LWR component materials tend to be reduced in simulated reactor cooling water were first recognized in Japan and reported to the world in 1970's. These are called 'Environmental fatigue'. Japan continues to play a leading role in this field and developed the methodology for evaluating fatigue life reduction due to environmental effects and issued the practical guidelines first in the world as the guidelines on environmental fatigue evaluation for LWR component by the Thermal and Nuclear Power Engineering Society (TENPES) in 2002. After that the Japan Society of Mechanical Engineers (JSME) reviewed the TENPES guidelines considering the latest environmental fatigue data and has established the new set of rules, called the Environmental Fatigue Evaluation Method (EFEM) in 2006. (author)

  13. Initiation of fatigue cracks in ultrafine-grained materials in highcycle fatigue region

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Fintová, S.

    Amsterdam : Elsevier, 2014 - (Gulagliano, M.; Vergani, L.), s. 2-5 ISSN 1877-7058. - (Procedia Engineering. 74). [ICMFM 2014 International Colloquium on Mechanical Fatigue of Metals /17./. Verbania (IT), 25.06.2014-27.06.2014] Institutional support: RVO:68081723 Keywords : Cyclic slip bands * Fatigue crack initiation * Fatigue of ultrafine-grained materials * Localization of cyclic platicity * Point defects Subject RIV: JL - Materials Fatigue, Friction Mechanics

  14. Determination of subject-specific muscle fatigue rates under static fatiguing operations

    OpenAIRE

    Ma, Liang; Zhang, Wei; Hu, Bo; Chablat, Damien; Bennis, Fouad; Guillaume, François

    2013-01-01

    Cumulative local muscle fatigue may lead to potential musculoskeletal disorder (MSD) risks {\\color{red}, and subject-specific muscle fatigability needs to be considered to reduce potential MSD risks.} This study was conducted to determine local muscle fatigue rate at shoulder joint level based on an exponential function derived from a muscle fatigue model. Forty male subjects participated in a fatiguing operation under a static posture with a range of relative force levels (14\\% - 33\\%). Rema...

  15. Myoelectrical Manifestation of Fatigue Less Prominent in Patients with Cancer Related Fatigue

    OpenAIRE

    Kisiel-Sajewicz, Katarzyna; Siemionow, Vlodek; Seyidova-Khoshknabi, Dilara; Davis, Mellar P.; Wyant, Alexandria; Ranganathan, Vinoth K.; Walsh, Declan; Yan, Jin H.; Hou, Juliet; Yue, Guang H

    2013-01-01

    Purpose A lack of fatigue-related muscle contractile property changes at time of perceived physical exhaustion and greater central than peripheral fatigue detected by twitch interpolation technique have recently been reported in cancer survivors with fatigue symptoms. Based on these observations, it was hypothesized that compared to healthy people, myoelectrical manifestation of fatigue in the performing muscles would be less significant in these individuals while sustaining a prolonged motor...

  16. ProFatigue: a software program for probabilistic assessment of experimental fatigue data sets

    OpenAIRE

    Fernández Canteli, Alfonso; Przybilla, Constanze; Nogal Macho, María; López Aenlle, Manuel; Castillo Ron, Enrique

    2014-01-01

    In this work, the software program ProFatigue is presented as a practical tool for derivation of probabilistic S-N and ε-N fields from experimental fatigue data. The program provides an estimation of the parameters involved in the regression probabilistic Weibull fatigue model developed by the authors, allowing an advantageous application of both fields to the stress or strain based approaches in the fatigue design of structures and mechanical components. An extension to the analysis of more ...

  17. The effect of cognitive fatigue on prefrontal cortex correlates of neuromuscular fatigue in older women

    OpenAIRE

    Shortz, Ashley E.; Pickens, Adam; Zheng, Qi; Mehta, Ranjana K.

    2015-01-01

    Background As the population of adults aged 65 and above is rapidly growing, it is crucial to identify physical and cognitive limitations pertaining to daily living. Cognitive fatigue has shown to adversely impact neuromuscular function in younger adults, however its impact on neuromuscular fatigue, and associated brain function changes, in older adults is not well understood. The aim of the study was to examine the impact of cognitive fatigue on neuromuscular fatigue and associated prefronta...

  18. Nondestructive evaluation of fatigue in titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roesner, H.; Meyendorf, N.; Sathish, S.; Matikas, T.E.

    2000-07-01

    Dissipated heat has been measured by thermographic technique during fatigue experiments on Ti-6Al-4V. Surface temperature of the specimen was found sensitive to the amount of fatigue damage accumulated in the material. An increased heat dissipation due to fatigue can be related to continuous change in the microstructure (increased dislocation density, stacking faults, etc.) of the material. A method based on passive thermography can be proposed to monitor damage accumulation in Ti-6Al-4V due to cyclic loading.

  19. Fatigue in Older Adults Post Myocardial Infarction

    OpenAIRE

    Patricia Barton Crane; Jimmy eEfird; Willie Mae Abel

    2016-01-01

    Objective. The purpose of this study was to comprehensively examine putative factors that may independently contribute to fatigue and subsequent persistence of fatigue in elderly adults 6-8 months post myocardial infarction (MI). Studies suggest cardiac function, comorbidities, daytime sleepiness, depression, anemia, interleukins, and social support are correlates of fatigue; however, no studies have systematically examined these factors 6 months post MI in an aging population. Methods. Study...

  20. Fatigue in Older Adults Postmyocardial Infarction

    OpenAIRE

    Crane, Patricia Barton; Jimmy T. Efird; Abel, Willie Mae

    2016-01-01

    Objective The purpose of this study was to comprehensively examine putative factors that may independently contribute to fatigue and subsequent persistence of fatigue in elderly adults 6–8 months post-myocardial infarction (MI). Studies suggest cardiac function, comorbidities, daytime sleepiness, depression, anemia, interleukins, and social support are correlates of fatigue; however, no studies have systematically examined these factors 6 months post-MI in an aging population. Methods Study p...

  1. Fatigue, workload and adaptive driver systems

    OpenAIRE

    Hancock, P.A.; Verwey, W.B.

    1997-01-01

    This paper is directed to the further understanding of the problems of fatigue and workload and their role in diminishing driving capability. We present a specific strategy designed to defend against the adverse effects of fatigue and workload extremes through the use of adaptive driver systems. To begin, the work presents a brief critique of Muscio's constraints on developing a test of fatigue. In criticizing these constraints, we point to the commonalities between all energetic reflections ...

  2. Nondestructive evaluation of fatigue in titanium alloys

    International Nuclear Information System (INIS)

    Dissipated heat has been measured by thermographic technique during fatigue experiments on Ti-6Al-4V. Surface temperature of the specimen was found sensitive to the amount of fatigue damage accumulated in the material. An increased heat dissipation due to fatigue can be related to continuous change in the microstructure (increased dislocation density, stacking faults, etc.) of the material. A method based on passive thermography can be proposed to monitor damage accumulation in Ti-6Al-4V due to cyclic loading

  3. Rotor fatigue monitoring data acquisition system

    Science.gov (United States)

    Smith, Scott M.

    1993-01-01

    The 40 by 80 Foot Wind Tunnel of the National Full Scale Aerodynamics Complex (NFAC) had a requirement to monitor rotor fatigue during a test. This test subjected various rotor components to stress levels higher than their structural fatigue limits. A data acquisition system was developed to monitor the cumulative fatigue damage of rotor components using National Instruments hardware and LabVIEW software. A full description of the data acquisition system including its configuration and salient features, is presented in this paper.

  4. Does Fatigue Alter Pitching Mechanics?

    Science.gov (United States)

    Chalmers, Peter Nissen; Erickson, Brandon J.; Sgroi, Terrance; Vignona, Peter; Lesniak, Matthew; Bush-Joseph, Charles A.; Verma, Nikhil N.; Romeo, Anthony A.

    2016-01-01

    Objectives: Background: Injuries of the adolescent shoulder and elbow are common in baseball pitchers. Fatigue has been demonstrated to be a risk factor for injury. Purpose: To determine if shoulder and elbow kinematics, pitching velocity, accuracy, and pain change during a simulated full baseball game in adolescent pitchers. Methods: Methods: Adolescent pitchers between the ages of 13-16 were recruited to throw a 90 pitch simulated game. Shoulder range of motion was assessed before and after the game. Velocity and accuracy were measured for every pitch and every 15th pitch was videotaped from two orthogonal views in high definition at 240 Hz. Quantitative and qualitative mechanics were measured from these videos. Perceived fatigue and pain were assessed after each inning using the visual analog scale. Data was statistically analyzed using a repeated-measures analysis of variance. Results: Results: Twenty-eight elite adolescent pitchers were included. These pitchers, on average, were 14.6±0.9 years old (mean ± standard deviation), had been pitching for 6.3±1.7 years, and threw 94±58 pitches per week. Our experimental model functioned as expected in that pitchers became progressively more fatigued and painful and pitched with a lower velocity as pitch number increased (p<0.001, 0.001, and <0.001 respectively). Knee flexion at ball release progressively increased with pitch number (p=0.008). Hip and shoulder separation significantly decreased as pitch number increased, from 90%±40% at pitch 15 to 40%±50% at pitch 90 (p0.271 in all cases, 91% power for elbow flexion at ball release). External rotation and total range of motion in the pitching shoulder significantly increased post-pitching (p=0.007 and 0.047 respectively). Conclusion: Conclusion: As pitchers progress through a simulated game they throw lower velocity pitches and become fatigued and painful. Core and leg musculature becomes fatigued before upper extremity kinematics change. Based upon these

  5. Individual differences in cognitive vulnerability to fatigue in the laboratory and in the workplace.

    Science.gov (United States)

    Van Dongen, Hans P A; Caldwell, John A; Caldwell, J Lynn

    2011-01-01

    Individual differences in cognitive functioning during extended work hours and shift work are of considerable magnitude, and observed both in the laboratory and in the workplace. These individual differences have a biological basis in trait-like, differential vulnerability to fatigue from sleep loss and circadian misalignment. Trait-like vulnerability is predicted in part by gene polymorphisms and other biological or psychological characteristics, but for the larger part it remains unexplained. A complicating factor is that whether individuals are vulnerable or resilient to sleep deprivation depends on the fatigue measure considered--subjective versus objective assessment, or one cognitive task versus another. Such dissociation has been observed in laboratory data published previously, and in data from a simulated operational setting first presented here. Discordance between subjective and objective measures of fatigue has been documented in various contexts, and may be one of the reasons why vulnerable individuals do not systematically opt out of professions involving high cognitive demands and exposure to fatigue. Discordance in vulnerability to fatigue among different measures of cognitive performance may be related to the "task impurity problem," which implies that interrelated cognitive processes involved in task performance must be distinguished before overall performance outcomes can be fully understood. Experimental studies and cognitive and computational modeling approaches are currently being employed to address the task impurity problem and gain new insights into individual vulnerability to fatigue across a wide range of cognitive tasks. This ongoing research is driving progress in the management of risks to safety and productivity associated with vulnerability to cognitive impairment from fatigue in the workplace. PMID:21531250

  6. Objective assessment of motor fatigue in multiple sclerosis: the Fatigue index Kliniken Schmieder (FKS).

    Science.gov (United States)

    Sehle, Aida; Vieten, Manfred; Sailer, Simon; Mündermann, Annegret; Dettmers, Christian

    2014-09-01

    Fatigue is a common and frequently disabling symptom of multiple sclerosis (MS). The aim of this study was to develop the Fatigue index Kliniken Schmieder (FKS) for detecting motor fatigue in patients with MS using kinematic gait analysis. The FKS relies on the chaos theoretical term "attractor", which, if unchanged, is a necessary and sufficient indicator of a stable dynamical system. We measured the acceleration of the feet at the beginning of and shortly before stopping a treadmill walking task in 20 healthy subjects and 40 patients with multiple sclerosis. The attractor and movement variability were calculated. In the absence of muscular exhaustion a significant difference in the attractor and movement variability between the two time points demonstrates altered motor control indicating fatigue. Subjects were classified using the FKS. All healthy subjects had normal FKS and thus no fatigue. 29 patients with MS were classified into a fatigue group and 11 patients into a non-fatigue group. This classification agreed with the physician's observation and video analyses in up to 97 % of cases. The FKS did not correlate significantly with the overall and motor dimensions of the fatigue questionnaire scores in patients with MS and motor fatigue. The common concept of fatigue as overall subjective sensation of exhaustion can be affected by conditions including depression, sleep disorder and others. FKS constitutes a robust and objective measure of changes in motor performance. Therefore, the FKS allows correct identification of motor fatigue even in cases where common comorbidities mask motor fatigue. PMID:24952620

  7. Evaluation of Conventional Al 2024 Fatigue Limit in Fatigue Test Using Thermographic Measurement: Effect of Frequency

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Klusák, Jan; Fernández, P.; Canteli, A.

    Switzerland: Trans Tech Publications, 2014 - (Clark, G.; Wang, C.), s. 1308-1313 ISSN 1662-8985. [Fatigue 2014 - International Fatigue Congress /11./. Melbourne (AU), 02.03.2014-07.03.2014] Institutional support: RVO:68081723 Keywords : Thermographic measurement * frequency * Al 2024 * statistical evaluation * Wohler curve Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. [Research Progress on the Interaction Effects and Its Neural Mechanisms between Physical Fatigue and Mental Fatigue].

    Science.gov (United States)

    Zhang, Lixin; Zhang, Chuncui; He, Feng; Zhao, Xin; Qi, Hongzhi; Wan, Baikun; Ming, Dong

    2015-10-01

    Fatigue is an exhaustion state caused by prolonged physical work and mental work, which can reduce working efficiency and even cause industrial accidents. Fatigue is a complex concept involving both physiological and psychological factors. Fatigue can cause a decline of concentration and work performance and induce chronic diseases. Prolonged fatigue may endanger life safety. In most of the scenarios, physical and mental workloads co-lead operator into fatigue state. Thus, it is very important to study the interaction influence and its neural mechanisms between physical and mental fatigues. This paper introduces recent progresses on the interaction effects and discusses some research challenges and future development directions. It is believed that mutual influence between physical fatigue and mental fatigue may occur in the central nervous system. Revealing the basal ganglia function and dopamine release may be important to explore the neural mechanisms between physical fatigue and mental fatigue. Future effort is to optimize fatigue models, to evaluate parameters and to explore the neural mechanisms so as to provide scientific basis and theoretical guidance for complex task designs and fatigue monitoring. PMID:26964325

  9. Poststroke Fatigue: Who Is at Risk for an Increase in Fatigue?

    Directory of Open Access Journals (Sweden)

    Hanna Maria van Eijsden

    2012-01-01

    Full Text Available Background. Several studies have examined determinants related to post-stroke fatigue. However, it is unclear which determinants can predict an increase in poststroke fatigue over time. Aim. This prospective cohort study aimed to identify determinants which predict an increase in post-stroke fatigue. Methods. A total of 250 patients with stroke were examined at inpatient rehabilitation discharge (T0 and 24 weeks later (T1. Fatigue was measured using the Fatigue Severity Scale (FSS. An increase in post-stroke fatigue was defined as an increase in the FSS score beyond the 95% limits of the standard error of measurement of the FSS (i.e., 1.41 points between T0 and T1. Candidate determinants included personal factors, stroke characteristics, physical, cognitive, and emotional functions, and activities and participation and were assessed at T0. Factors predicting an increase in fatigue were identified using forward multivariate logistic regression analysis. Results. The only independent predictor of an increase in post-stroke fatigue was FSS (OR 0.50; 0.38–0.64, P<0.001. The model including FSS at baseline correctly predicted 7.9% of the patients who showed increased fatigue at T1. Conclusion. The prognostic model to predict an increase in fatigue after stroke has limited predictive value, but baseline fatigue is the most important independent predictor. Overall, fatigue levels remained stable over time.

  10. Poststroke fatigue: who is at risk for an increase in fatigue?

    NARCIS (Netherlands)

    Eijsden, H.M. van; Port, I.G. van de; Visser-Meily, J.M.; Kwakkel, G.

    2012-01-01

    Background. Several studies have examined determinants related to post-stroke fatigue. However, it is unclear which determinants can predict an increase in poststroke fatigue over time. Aim. This prospective cohort study aimed to identify determinants which predict an increase in post-stroke fatigue

  11. Fatigue Risk Management: A Maritime Framework

    Directory of Open Access Journals (Sweden)

    Michelle Rita Grech

    2016-01-01

    Full Text Available It is evident that despite efforts directed at mitigating the risk of fatigue through the adoption of hours of work and rest regulations and development of codes and guidelines, fatigue still remains a concern in shipping. Lack of fatigue management has been identified as a contributory factor in a number of recent accidents. This is further substantiated through research reports with shortfalls highlighted in current fatigue management approaches. These approaches mainly focus on prescriptive hours of work and rest and include an individualistic approach to managing fatigue. The expectation is that seafarers are responsible to manage and tolerate fatigue as part of their working life at sea. This attitude is an accepted part of a seafarer’s role. Poor compliance is one manifest of this problem with shipboard demands making it hard for seafarers to follow hours of work and rest regulations, forcing them into this “poor compliance” trap. This makes current fatigue management approaches ineffective. This paper proposes a risk based approach and way forward for the implementation of a fatigue risk management framework for shipping, aiming to support the hours of work and rest requirements. This forms part of the work currently underway to review and update the International Maritime Organization, Guidelines on Fatigue.

  12. Chronic fatigue syndrome: a review for clinicians.

    Science.gov (United States)

    Goshorn, R K

    1998-01-01

    Syndromes characterized by persistent fatigue, musculoskeletal pain, sleep disturbance, and subjective cognitive impairment have been common problems in clinical practice for decades. The chronic fatigue syndrome case definition was created to standardize the patient population in research studies and to foster a systematic and comprehensive approach to the attempt to define the etiology and pathophysiology of these syndromes. The pathogenesis of chronic fatigue syndrome remains unknown, though it does appear to be associated with subtle neuroendocrine and immunologic abnormalities. Treatment of chronic fatigue syndrome is empirical. Significant palliation is often possible, though treatment success requires skillful practice of the art of medicine. PMID:9608620

  13. Fatigue and radiotherapy. A literature review

    International Nuclear Information System (INIS)

    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)

  14. Chaos caused by fatigue crack growth

    International Nuclear Information System (INIS)

    The nonlinear dynamic responses including chaotic oscillations caused by a fatigue crack growth are presented. Fatigue tests have been conducted on a novel fatigue-testing rig, where the loading is generated from inertial forces. The nonlinearity is in the form of discontinuous stiffness caused by the opening and closing of a growing crack. Nonlinear dynamic tools such as Poincare maps and bifurcation diagrams are used to unveil the global dynamics of the system. The results obtained indicate that fatigue crack growth strongly influences the dynamic response of the system leading to chaos

  15. Chaos caused by fatigue crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Foong, C.-H.; Pavlovskaia, Ekaterina; Wiercigroch, Marian; Deans, William

    2003-06-01

    The nonlinear dynamic responses including chaotic oscillations caused by a fatigue crack growth are presented. Fatigue tests have been conducted on a novel fatigue-testing rig, where the loading is generated from inertial forces. The nonlinearity is in the form of discontinuous stiffness caused by the opening and closing of a growing crack. Nonlinear dynamic tools such as Poincare maps and bifurcation diagrams are used to unveil the global dynamics of the system. The results obtained indicate that fatigue crack growth strongly influences the dynamic response of the system leading to chaos.

  16. Fatigue in Multiple Sclerosis: (An update

    Directory of Open Access Journals (Sweden)

    Hossein Zarei

    2007-10-01

    Full Text Available BACKGROUND:To study the dimensions of fatigue in multiple sclerosis, its pathophysiology, the efficacy, tolerability and safety of drug and non-drug treatments and measurement of fatigue. METHODS: Relevant articles from PubMed and Google scholar search engines from January 1987 until September 2006 were studied to compose a short clinical update (not a systematic review and make the required clinical information available for the clinicians. RESULTS: There is evidence that fatigue is very common in all types and stages of multiple sclerosis, but its pathophysiology is not well explained. Consequently, few drug options have been offered for its treatment. Amantadine is the bestknown drug, though its efficacy and duration of action are limited. Pemoline and modafinil are alternatives and have
    some effects on fatigue. DAP (diaminopyridine, ASA (acetylsalicylic acid, methylphenidate and fluoxetine are other possible options but await further confirmation. Neurorehabilitation, regular exercise and cooling are confirmed to be of value in MS treatment. Measurement of fatigue is a complicated issue. At present fatigue does not have a laboratory marker. CONCLUSIONS: The results of this short clinical update provide guidelines for diagnosing MS-related fatigue and differentiating
    it from other similar physical and psychological conditions. It also examines prescription drug options and other therapies for MS patients with fatigue.
    KEYWORDS: Multiple sclerosis, fatigue, pathophysiology, treatment, measurement.

  17. Fatigue Risk Management: A Maritime Framework.

    Science.gov (United States)

    Grech, Michelle Rita

    2016-02-01

    It is evident that despite efforts directed at mitigating the risk of fatigue through the adoption of hours of work and rest regulations and development of codes and guidelines, fatigue still remains a concern in shipping. Lack of fatigue management has been identified as a contributory factor in a number of recent accidents. This is further substantiated through research reports with shortfalls highlighted in current fatigue management approaches. These approaches mainly focus on prescriptive hours of work and rest and include an individualistic approach to managing fatigue. The expectation is that seafarers are responsible to manage and tolerate fatigue as part of their working life at sea. This attitude is an accepted part of a seafarer's role. Poor compliance is one manifest of this problem with shipboard demands making it hard for seafarers to follow hours of work and rest regulations, forcing them into this "poor compliance" trap. This makes current fatigue management approaches ineffective. This paper proposes a risk based approach and way forward for the implementation of a fatigue risk management framework for shipping, aiming to support the hours of work and rest requirements. This forms part of the work currently underway to review and update the International Maritime Organization, Guidelines on Fatigue. PMID:26840326

  18. Compassion fatigue in pediatric palliative care providers.

    Science.gov (United States)

    Rourke, Mary T

    2007-10-01

    The experience of compassion fatigue is an expected and common response to the professional task of routinely caring for children at the end of life. Symptoms of compassion fatigue often mimic trauma reactions. Implementing strategies that span personal, professional, and organizational domains can help protect health care providers from the damaging effects of compassion fatigue. Providing pediatric palliative care within a constructive and supportive team can help caregivers deal with the relational challenges of compassion fatigue. Finally, any consideration of the toll of providing pediatric palliative care must be balanced with a consideration of the parallel experience of compassion satisfaction. PMID:17933615

  19. Compassion fatigue and the veterinary health team.

    Science.gov (United States)

    Cohen, Susan P

    2007-01-01

    Although the term "compassion fatigue" is often used interchangeably with the term "burnout", they are two different concepts. Compassion fatigue stems from an overcommitment to work that involves caring for others and is considered by some to be a kind of secondary posttraumatic stress disorder. Because they often invest themselves deeply in the animals they care for, veterinarians, technicians, and other members of an animal health team may be particularly vulnerable to compassion fatigue. This article summarizes the current state of knowledge about compassion fatigue, describes its symptoms, and suggests ways to prevent or overcome it. PMID:17162116

  20. Fatigue in Breakwater Concrete Armour Units

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    1985-01-01

    The reliability of rubble mound breakwaters depends on the hydraulic stability and the mechanical strength of the armour units. The paper deals with the important aspect of fatigue related to the strength of concrete armour units. Results showing significant fatigue from impact tests with Dolosse...... made of unreinforced and steel fibre reinforced flyash concrete are presented. Moreover universal graphs for fatigue in armour units made of conventional unreinforced concrete exposed to impact load and pulsating load are presented. The effect of fibre reinforcement and the implementation of fatigue in...

  1. Fatigue Performance of Bridge Deck Pavement Materials

    Institute of Scientific and Technical Information of China (English)

    WU Shaopeng; ZHANG Guang; HAN Jun; LIU Gang; ZHOU Jie

    2009-01-01

    Three beam samplesof bridge deck pavementwere prepared, with gradationtypes of AC-13, and AC-16 and combined AC-13+AC-16. Four-point bending test was adopted to investigate the fatigue performance of these beam samples. The experimental results indicate that the initial bending stiffness is related to the type of beam sample and testing temperature. Fatigue life of these samples decreases as the increase of the controlled strain level. The AC-13 beam sample exhibits better fatigue resistance and bigger limiting bending strain at the given strain level and temperature. Com-pared with single beam sample, the fatigue performance of combining beam sample is relatively poor.

  2. Uncertainty on Fatigue Damage Accumulation for Composite Materials

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2009-01-01

    In the present paper stochastic models for fatigue damage accumulation for composite materials are presented based on public available constant and variable amplitude fatigue tests. The methods used for estimating the SN-curve and accumulated fatigue damage are presented....

  3. Fatigue in primary Sjögren's syndrome

    OpenAIRE

    Barendregt, P; M. Visser; SMETS, E.; Tulen, J; van den Meiracker, A H; Boomsma, F; Markusse, H

    1998-01-01

    OBJECTIVE—To assess fatigue in relation to depression, blood pressure, and plasma catecholamines in patients with primary Sjögren's syndrome (SS), in comparison with healthy controls and patients with rheumatoid arthritis.
METHODS—For the assessment of fatigue the Multidimensional Fatigue Inventory (MFI) was used, a 20 item questionnaire, covering the following dimensions: general fatigue, physical fatigue, mental fatigue, reduced motivation, and reduced activity. Furthermore, the Zung depres...

  4. Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures

    OpenAIRE

    Barsoum, Zuheir

    2008-01-01

    This doctoral thesis is concerned with fatigue life of welded structures. Several topics related to fatigue of welded structures are treated such as; weld defects and their influence on fatigue performance of welded structures, fatigue life prediction using LEFM (Linear Elastic Fracture Mechanics), fatigue testing, welding simulation, residual stress prediction and measurement and their influence on fatigue life. The work that is reported in this doctoral thesis is part results of the Nordic ...

  5. One-Year Longitudinal Study of Fatigue, Cognitive Functions, and Quality of Life After Adjuvant Radiotherapy for Breast Cancer

    International Nuclear Information System (INIS)

    Purpose: Most patients with localized breast cancer (LBC) who take adjuvant chemotherapy (CT) complain of fatigue and a decrease in quality of life during or after radiotherapy (RT). The aim of this longitudinal study was to compare the impact of RT alone with that occurring after previous CT on quality of life. Methods and Materials: Fatigue (the main endpoint) and cognitive impairment were assessed in 161 CT-RT and 141 RT patients during RT and 1 year later. Fatigue was assessed with Functional Assessment of Cancer Therapy-General questionnaires, including breast and fatigue modules. Results: At baseline, 60% of the CT-RT patients expressed fatigue vs. 33% of the RT patients (p <0.001). Corresponding values at the end of RT were statistically similar (61% and 53%), and fatigue was still reported at 1 year by more than 40% of patients in both groups. Risk factors for long-term fatigue included depression (odds ratio [OR] = 6), which was less frequent in the RT group at baseline (16% vs. 28 %, respectively, p = 0.01) but reached a similar value at the end of RT (25% in both groups). Initial mild cognitive impairments were reported by RT (34 %) patients and CT-RT (24 %) patients and were persistent at 1 year for half of them. No biological disorders were associated with fatigue or cognitive impairment. Conclusions: Fatigue was the main symptom in LBC patients treated with RT, whether they received CT previously or not. The correlation of persistent fatigue with initial depressive status favors administering medical and psychological programs for LBC patients treated with CT and/or RT, to identify and manage this main quality-of-life-related symptom.

  6. Fatigue is a brain-derived emotion that regulates the exercise behavior to ensure the protection of whole body homeostasis

    Directory of Open Access Journals (Sweden)

    Timothy David Noakes

    2012-04-01

    Full Text Available An influential book written by A. Mosso in the late 19th century proposed that fatigue that at first sight might appear an imperfection of our body, is on the contrary one of its most marvellous perfections. The fatigue increasing more rapidly than the amount of work done saves us from the injury which lesser sensibility would involve for the organism so that muscular fatigue also is at bottom an exhaustion of the nervous system.It has taken more than a century to confirm Mosso’s idea that both the brain and the muscles alter their function during exercise and that fatigue is predominantly an emotion, part of a complex regulation, the goal of which is to protect the body from harm. Mosso’s ideas were supplanted in the English literature by those of A.V. Hill who believed that fatigue was the result of biochemical changes in the exercising limb muscles - peripheral fatigue - to which the central nervous system makes no contribution. The past decade has witnessed the growing realization that this brainless model cannot explain exercise performance. This article traces the evolution of our modern understanding of how the CNS regulates exercise specifically to insure that each exercise bout terminates whilst homeostasis is retained in all bodily systems. The brain uses the symptoms of fatigue as key regulators to insure that the exercise is completed before harm develops. These sensations of fatigue are unique to each individual and are illusionary since their generation is largely independent of the real biological state of the athlete at the time they develop. The model predicts that attempts to understand fatigue and to explain superior human athletic performance purely on the basis of the body’s known physiological and metabolic responses to exercise must fail since subconscious and conscious mental decisions made by winners and losers, in both training and competition, are the ultimate determinants of both fatigue and athletic performance.

  7. AREVA Fatigue Concept (AFC). Live demonstration of a modern fatigue monitoring system FAMOS i

    International Nuclear Information System (INIS)

    The prevention of fatigue damage is to be considered as a crucial issue in the view of changing boundary conditions: code modifications, long term operation, new plants with operating periods of 60 years. The AREVA Fatigue Concept (AFC) provides for a multiple step and multidisciplinary process (process engineering, fatigue monitoring, fatigue analyses etc.) against fatigue before and during the entire operation of nuclear power plants (NPPs). The ensuing fatigue analyses are based on the real operational loads measured continuously on site in the plant by means of an installed fatigue monitoring system. This way, realistic load data are available and qualified fatigue usage factors can be determined. Locations of potential fatigue failure are reliably identified and expensive cost for inspection can be essentially reduced. The direct processing of the measured temperatures can immediately be used for a Fast Fatigue Evaluation (FFE). FFE calculates the real stress history in form of a six stress tensor approach. The shape functions of fatigue relevant NPP parts are included. Based on the stress history the fatigue evaluation is the last step. Effects based on environmental fatigue influence can also be analyzed inside AFC. The fatigue calculation workflow will be processed on the FAMOS i (i stands for ''integrated'') demonstration wall (cf. Figure 1). Starting with the measurement of transient temperatures, the thermal loads will be shown with the FAMOS i-viewer software. Within the next step the inner wall temperature is calculated, which is based on the FAMOS i measurements. In a third step the computation of the stress history is done, followed by the combination of the relevant stress ranges for the purpose of a particular fatigue usage calculation. In addition, a short overview will be given about the requirements and solutions of an effective modern measurement system, followed by showing the benefit of local monitoring for NPP owners. (orig.)

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

    Science.gov (United States)

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

    2016-03-01

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

  9. Reconstruction of grand design for fatigue evaluation. Step-2. Fatigue failure analysis of Japanese NPPs

    International Nuclear Information System (INIS)

    After Fukushima-Daiichi NPP accident, improvement of nuclear safety is highly requested in order to prevent re-occurrence of severe accident. New scheme of fatigue evaluation to confirm system safety in NPPs is enhanced to be established based on Defense-in-Depth concept. In step 1, grand design of fatigue evaluation is reviewed on the viewpoint of fatigue management in long-term safe operation of NPPs, which is required after Fukushima-Daiichi NPP accident. This study focuses on the direction to re-construct grand design of fatigue evaluation to ensure system safety based on fatigue failure analysis of Japanese NPPs. (author)

  10. Reconstruction of grand design for fatigue evaluation based on fatigue failure analysis of Japanese NPPs

    International Nuclear Information System (INIS)

    After Fukushima Daiichi NPP accident, the improvement of nuclear safety is highly requested in order to prevent re-occurrence of severe accident. New scheme of fatigue evaluation to confirm system safety in NPPs is enhanced to be established based on Defense in Depth concept. This study focuses on the direction to reconstruct Grand Design of fatigue evaluation to ensure system safety based on fatigue failure analysis of Japanese NPPs. The issues of fatigue evaluation we have now is investigated in order to review Grand Design on the basis of new role of fatigue management in plant long term safe operating scheme that is required after Fukushima Daiichi NPP accident. (author)

  11. Failure by fracture and fatigue in 'NANO' and 'BIO'materials

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, R.O.; Muhlstein, C.L.; Nalla, R.K.

    2003-12-19

    The behavior of nanostructured materials/small-volumestructures and biologi-cal/bio-implantable materials, so-called "nano"and "bio" materials, is currently much in vogue in materials science. Oneaspect of this field, which to date has received only limited attention,is their fracture and fatigue properties. In this paper, we examine twotopics in this area, namely the premature fatigue failure ofsilicon-based micron-scale structures for microelectromechanical systems(MEMS), and the fracture properties of mineralized tissue, specificallyhuman bone.

  12. Coverage of multiaxial fatigue criteria in fatigue limit region

    Directory of Open Access Journals (Sweden)

    Papuga J.

    2007-11-01

    Full Text Available There is a power of methods aimed at calculation of equivalent fatigue limit for arbitrary multiaxial loading. Although there are so many ways of computation, their thorough mutual comparison in a larger scale is missing. The database project presented in this paper comprise of several databases crowned with the FatLim database, which comprise of a huge number of experimental results and of 18 computational method working in the category mentioned before. The great block of data was acquired using in-house fatigue software PragTic, which is offered as a freeware application. The FatLim database follows its philosophy of a simple and non-paid accessibility. Its query tool written in MySQL and PhP allows to users to evaluate a practical usability of tested methods on load cases, which the users define. All the issues covered within this paper are available on the website www.pragtic.com, structure of which is described here.

  13. Fatigue problems of steel bridges

    Czech Academy of Sciences Publication Activity Database

    Urushadze, Shota; Frýba, Ladislav; Škaloud, Miroslav; Pirner, Miroš; Zörnerová, Marie

    Stirlingshire : Civil-Comp Press, 2012 - (Pombo, J.), s. 142-151 ISBN 978-1-905088-53-9. ISSN 1759-3433. [International Conference on Railway Technology: Research, Development and Maintenance /1./. Las Palmas de Gran Canaria (ES), 18.04.2012-20.04.2012] R&D Projects: GA MŠk(CZ) 7E08098 Grant ostatní: evropská komise(XE) RFSR-CT-2008-00033 (BRIFAG); GA ČR(CZ) GA103/08/1340 Institutional support: RVO:68378297 Keywords : steel bridges * fatigue * S-N curve * orthotropic deck * web breathing Subject RIV: JM - Building Engineering

  14. Fatigue life evaluation of mechanical components using vibration fatigue analysis technique

    International Nuclear Information System (INIS)

    Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration's direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition

  15. Studies of diaphragm fatigue and dysfunction

    OpenAIRE

    Radell, Peter J

    2001-01-01

    Diaphragm fatigue and dysfunction are important components of acute and chronic respiratory pump failure. We lack knowledge about the nature of diaphragm fatigue and the pathophysiological and morphological changes that occur in the diaphragm after prolonged mechanical ventilation. This thesis studied two aspects of diaphragm function. Diaphragm contractility and oxidative metabolism were studied during inspiratory resistive loaded breathing (IRB) and hypoxia, and diaphragm ...

  16. 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)

  17. Fatigue Reliability under Multiple-Amplitude Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    initial tensile strength and the fatigue life, the probability distributions for the residual tensile strength in both the crack initiation and the crack propagation stages of fatigue are determined. The method is illustrated for two-amplitude loads by means of experimental results obtained by testing...

  18. Attention, effort, and fatigue: Neuropsychological perspectives

    Science.gov (United States)

    Cohen, Ronald A.; Odonnell, Brian F.

    1988-01-01

    Models of attention, effort, and fatigue are reviewed. Methods are discussed for measuring these phenomena from a neuropsychological and psychophysiological perspective. The following methodologies are included: (1) the autonomic measurement of cognitive effort and quality of encoding; (2) serial assessment approaches to neurophysiological assessment; and (3) the assessment of subjective reports of fatigue using multidimensional ratings and their relationship to neurobehavioral measures.

  19. Standard guide for fretting fatigue testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This guide defines terminology and covers general requirements for conducting fretting fatigue tests and reporting the results. It describes the general types of fretting fatigue tests and provides some suggestions on developing and conducting fretting fatigue test programs. 1.2 Fretting fatigue tests are designed to determine the effects of mechanical and environmental parameters on the fretting fatigue behavior of metallic materials. This guide is not intended to establish preference of one apparatus or specimen design over others, but will establish guidelines for adherence in the design, calibration, and use of fretting fatigue apparatus and recommend the means to collect, record, and reporting of the data. 1.3 The number of cycles to form a fretting fatigue crack is dependent on both the material of the fatigue specimen and fretting pad, the geometry of contact between the two, and the method by which the loading and displacement are imposed. Similar to wear behavior of materials, it is important t...

  20. Fatigue Reliability of Offshore Wind Turbine Systems

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    Optimization of the design of offshore wind turbine substructures with respect to fatigue loads is an important issue in offshore wind energy. A stochastic model is developed for assessing the fatigue failure reliability. This model can be used for direct probabilistic design and for calibration ...

  1. MR spectroscopy studies of human muscle fatigue

    International Nuclear Information System (INIS)

    To investigate the relationship between fatigue and metabolism, P-31 MR spectra of human muscle were obtained while simultaneously monitoring force production, before, during, and following aerobic and anaerobic exercise. Changes of PCr and Pi showed a nonlinear relationship to fatigue

  2. A critical evaluation on the fatigue problem

    International Nuclear Information System (INIS)

    A review of the different aspects of approaches to the fatigue problems since the Woehler curves till the crack propagation is presented. The interrelationship among each one of the aspects is then carried out as well as the relation of the aspects to the different fatigue phases, since the crack nucleation till the final rupture in an attempt to unify the design procedure. (Author)

  3. Fatigue, workload and adaptive driver systems

    NARCIS (Netherlands)

    Hancock, P.A.; Verwey, W.B.

    1997-01-01

    This paper is directed to the further understanding of the problems of fatigue and workload and their role in diminishing driving capability. We present a specific strategy designed to defend against the adverse effects of fatigue and workload extremes through the use of adaptive driver systems. To

  4. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    In the present work the effect of ion nitriding, laser hardening and hot dip galvanizing upon the fatigue limit and notch sensitivity of a B-Mn Swedish steel SS 2131 have been investigated. The fatigue tests were performed in plane reverse bending fatigue (R=1). The quenched and tempered condition was taken as the reference condition. The microstructure, microhardness, fracture surface and coating appearance of the fatigue surface treated specimens were studied. Residual stress and retained austenite measurements were also carried out. It was found that ion nitriding improves the fatigue limit by 53 % for smooth specimens and by 115 % for notched specimens. Laser hardening improves the fatigue limit by 18 % and 56 % for smooth and notched specimen respectively. Hot dip galvanizing gives a slight deterioration of the fatigue limit (9 % and 10 % for smooth and notched specimen respectively). Ion nitriding and laser hardening decrease the value of the notch sensitivity factor q by 78 % and 65 % respectively. Hot dip galvanizing does not modify it. A simple schematic model based on a residual stress distribution, has been used to explain the different effects. It seems that the presence of the higher compressive residual stresses and the higher uniformity of the microstructure may be the causes of the better fatigue performance of ion nitrided specimens. (119 refs.) (author)

  5. Fracture mechanics, creep and fatigue analysis

    International Nuclear Information System (INIS)

    This book covers the proceedings of the 1988 ASME Pressure Vessels and Piping Converence. Topics include: Fatigue crack growth analysis of a 450 PWR - lateral; Fatigue crack growth on straight pipes under thermal shocks; and The treatment of residual stress in defect assessment of austenitic fast reactor structures

  6. Fracture mechanics, creep and fatigue analysis

    Energy Technology Data Exchange (ETDEWEB)

    Becht IV, C. (Becht Engineering Co., Inc., Liberty Corner, NJ (US)); Bhandari, S.K. (Framatome, Paris (FR)); Tomkins, B. (Northern Research Labs., Risley (GB))

    1988-01-01

    This book covers the proceedings of the 1988 ASME Pressure Vessels and Piping Converence. Topics include: Fatigue crack growth analysis of a 45{sup 0} PWR - lateral; Fatigue crack growth on straight pipes under thermal shocks; and The treatment of residual stress in defect assessment of austenitic fast reactor structures.

  7. Fatigue crack initiation in fcc crystals

    Czech Academy of Sciences Publication Activity Database

    Lukáš, Petr; Kunz, Ludvík

    Brno : VUT, 2001, s. 263-271. [International Conference on Materials structure and Micromechanics of Fracture /3./. Brno (CZ), 27.06.2001-29.06.2001] R&D Projects: GA AV ČR IAA2041002 Institutional research plan: CEZ:AV0Z2041904 Keywords : cyclic plastic deformation * crystal defects * fatigue crack initiation Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. Fatigue Lives of Materials Cut by Lasers

    Science.gov (United States)

    Martin, Michael R.

    1987-01-01

    Laser machining helps to balance high-speed rotating machinery. Report describes continuing studies of fatigue lives of materials cut by lasers. One long-term objective of such studies is use of laser machining to balance rotors operating at high speeds. To achieve objective, necessary to know relationship between effects of conventional and laser machining on fatigue lives of machined materials.

  9. Thermal Fatigue Analysis of Takeover Pipeline

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    This article uses the finite element analysis software ANSYS to analyze the fatigue life of the three links pipeline with different angles in the first level pipe of experimental fast reactor. The fatigue analysis is operated following the startup and shutdown process which has two load step,

  10. Common Mathematical Model of Fatigue Characteristics

    Directory of Open Access Journals (Sweden)

    Z. Maléř

    2004-01-01

    Full Text Available This paper presents a new common mathematical model which is able to describe fatigue characteristics in the whole necessary range by one equation only:log N = A(R + B(R ∙ log Sawhere A(R = AR2 + BR + C and B(R = DR2 + AR + F.This model was verified by five sets of fatigue data taken from the literature and by our own three additional original fatigue sets. The fatigue data usually described the region of N 104 to 3 x 106 and stress ratio of R = -2 to 0.5. In all these cases the proposed model described fatigue results with small scatter. Studying this model, following knowledge was obtained:– the parameter ”stress ratio R” was a good physical characteristic– the proposed model provided a good description of the eight collections of fatigue test results by one equation only– the scatter of the results through the whole scope is only a little greater than that round the individual S/N curve– using this model while testing may reduce the number of test samples and shorten the test time– as the proposed model represents a common form of the S/N curve, it may be used for processing uniform objective fatigue life results, which may enable mutual comparison of fatigue characteristics.

  11. 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

  12. On the Fatigue Analysis of Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Herbert J.

    1999-06-01

    Modern wind turbines are fatigue critical machines that are typically used to produce electrical power from the wind. Operational experiences with these large rotating machines indicated that their components (primarily blades and blade joints) were failing at unexpectedly high rates, which led the wind turbine community to develop fatigue analysis capabilities for wind turbines. Our ability to analyze the fatigue behavior of wind turbine components has matured to the point that the prediction of service lifetime is becoming an essential part of the design process. In this review paper, I summarize the technology and describe the ''best practices'' for the fatigue analysis of a wind turbine component. The paper focuses on U.S. technology, but cites European references that provide important insights into the fatigue analysis of wind turbines.

  13. Interconnect fatigue design for terrestrial photovoltaic modules

    Science.gov (United States)

    Mon, G. R.; Moore, D. M.; Ross, R. G., Jr.

    1982-03-01

    The results of comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable (1) the prediction of cumulative interconnect failures during the design life of an array field, and (2) the unambiguous--ie., quantitative--interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field.

  14. Fatigue in tension perpendicular to the grain

    DEFF Research Database (Denmark)

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

    1999-01-01

    Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens and on...... made on dowel type connections that have tension perpendicular to the grain as limiting strength parameter. Is is concluded that no significant influence of duration of load is observed when the fatigue resistance of small specimens at 0.01 Hz and 0.1 Hz are compared. A weak but inconclusive time...

  15. Fatigue In Tension Perpendicular to the Grain

    DEFF Research Database (Denmark)

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

    2004-01-01

    Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens and on...... made on dowel type connections that have tension perpendicular to the grain as limiting strength parameter. It is concluded that no significant influence of duration of load is observed w hen the fatigue resistance of small specimens at 0.01 Hz and 0.1 Hz are compared. A weak but inconclusive time...

  16. High cycle fatigue properties of inconel 690

    International Nuclear Information System (INIS)

    Inconel 690 is presently used as sleeve material and a replacement alloy in degraded steam generators, as well as the material for new steam generators. But Inconel 690 has low thermal conductivity which are 3-8% less than that of Inconel 600 at operating temperature. For the same power output, conduction area must be increased. As a result, more fluid induced vibration can cause a fatigue damage of Inconel 690. High cycle fatigue ruptures occurred in the U-bend regions of North Anna Unit 1 and Mihama Unit 2 steam generators. At this study, the effect of temperature on fatigue crack growth rate in Inconel 690 steam generator tube was investigated at various temperature in air environment. With increasing temperature, fatigue crack growth rate increased and grain size effect decreased. Chromium carbides which have large size and semi-continuous distribution in the grain boundaries decreased fatigue crack growth rate

  17. Thermal fatigue behavior of K465 superalloy

    Institute of Scientific and Technical Information of China (English)

    YANG Jinxia; ZHENG Qi; SUN Xiaofeng; GUAN Hengrong; HU Zhuangqi

    2006-01-01

    The thermal fatigue behavior of K465 superalloy was investigated at the peak temperature of 1050℃. By scanning electron microscopy (SEM) and optical microscopy, the main crack length was observed and measured. The initiation sites of the tested alloys are different in as-cast (named as K465) and solution heat treatment (named as SK465) conditions.In K465 alloy, most thermal fatigue cracks nucleate at (Nb,W,Ti)C carbides. In SK465 alloy, thermal fatigue cracks initiate in interdendritic regions, MC-type carbides and some interfaces. Thermal fatigue cracks propagate in transdendritic mode,and M6C-type carbides could retard thermal fatigue crack growth for SK465 superalloy.

  18. Multiscale Fatigue Life Prediction for Composite Panels

    Science.gov (United States)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Arnold, Steven M.

    2012-01-01

    Fatigue life prediction capabilities have been incorporated into the HyperSizer Composite Analysis and Structural Sizing Software. The fatigue damage model is introduced at the fiber/matrix constituent scale through HyperSizer s coupling with NASA s MAC/GMC micromechanics software. This enables prediction of the micro scale damage progression throughout stiffened and sandwich panels as a function of cycles leading ultimately to simulated panel failure. The fatigue model implementation uses a cycle jumping technique such that, rather than applying a specified number of additional cycles, a specified local damage increment is specified and the number of additional cycles to reach this damage increment is calculated. In this way, the effect of stress redistribution due to damage-induced stiffness change is captured, but the fatigue simulations remain computationally efficient. The model is compared to experimental fatigue life data for two composite facesheet/foam core sandwich panels, demonstrating very good agreement.

  19. Temperament vs. chronic fatigue in police officers

    Directory of Open Access Journals (Sweden)

    Ewa Stępka

    2015-12-01

    Full Text Available Background: Chronic fatigue is a problem affecting a still growing number of people. Among them there are representatives of different professions who are forced to cope not only with occupational stress, but also with the problem of fatigue. The police is one of such occupational groups, in which exposure to stressful and often traumatic situations, contact with those who violate the law, shift work and contact with superiors can play a key role in the development of chronic fatigue. However, chronic fatigue, induced by the above mentioned factors, does not affect all police officers since its occurrence also depends on many personal traits, including temperament. Material and methods: We studied a group of 61 police officers of the Kuyavian-Pomeranian garrison. The study was conducted using the Buss and Plomin EAS (emotionality, activity, sociability Temperament Questionnaire, CIS-20R (community, innovation, survey Questionnaire, developed by Vercoulen et al. and a questionnaire on socio-demographic data. Results: The results indicated the relationship between chronic fatigue and emotionality. Statistical analyses showed a negative correlation between the nature of emotional components, distress, fear, anger, and the general rate of chronic fatigue. There was no statistically significant correlation between age, and service experience and the level of chronic fatigue. Conclusions: The results indicate that the officers of the study group show dramatically high levels of chronic fatigue. The results also revealed that temperament characteristics, such as sociability and activity, reported in the literature as factors reducing fatigue and stress, did not show relevance to chronic fatigue in the study group. Med Pr 2015;66(6:793–801

  20. Strain evaluation in fatigue analysis

    International Nuclear Information System (INIS)

    Thermoplastic analysis and more precisely fatigue analysis of nuclear components working at high temperature is usually very difficult and very expensive. Simplified methods have been proposed and are generally used to perform analysis of these structures. These simplified methods require elastic analysis of the component. For a fatigue analysis it is necessary to obtain a very precise value of the strains so the elastic strains must be corrected in order to take plasticity into account. This later appears in two different ways. Non linearity of material which induces strain amplification when working in the plastic field especially near by geometric discontinuities. That can be taken into account with a coefficient Ke. Triaxiality and isovolumic character of strains in the plastic field. That also induces strain amplification with regard to elastic computation. It is proposed in this work to introduce a coefficient Kv to estimate this strain amplification. Several elastic and plastic calculations for typical geometries, have been done in order to test the importance of these parameters and to set up methods for evaluating the coefficients Ke and Kv

  1. [Chronic fatigue syndrome--a disease entity or an unspecified psychosomatic disorder?].

    Science.gov (United States)

    Albus, C

    1997-12-01

    In spite of its nature as an often severe and disabeling disease, it is still unclear, whether the Chronic Fatigue Syndrome (CFS) is an entire disease of its own right or not. Moreover, there is a growing evidence that patients with CFS belong to an inhomogeneous group with different etiologic constellations. Specific somatic factors, e.g. viruses, seem to be less important for onset than certain personality-traits like depressiveness and workaholism. These traits lead to an increased vulnerability to unspecific psychological or biological stressors that may cause chronic fatigue by complex psychosomatic interferences. Concerning diagnosis, there are no specific methods or results available, the same is true for pharmacological treatment. As a consequence, practitioners should be aware not to miss a somatic disease causing fatigue, and, parallel to this, start right from the beginning talking about the psychosomatic background of CFS. Furthermore, psychotherapy has shown to be effective in CFS. PMID:9487622

  2. DNA methylation modifications associated with chronic fatigue syndrome.

    Directory of Open Access Journals (Sweden)

    Wilfred C de Vega

    Full Text Available Chronic Fatigue Syndrome (CFS, also known as myalgic encephalomyelitis, is a complex multifactorial disease that is characterized by the persistent presence of fatigue and other particular symptoms for a minimum of 6 months. Symptoms fail to dissipate after sufficient rest and have major effects on the daily functioning of CFS sufferers. CFS is a multi-system disease with a heterogeneous patient population showing a wide variety of functional disabilities and its biological basis remains poorly understood. Stable alterations in gene function in the immune system have been reported in several studies of CFS. Epigenetic modifications have been implicated in long-term effects on gene function, however, to our knowledge, genome-wide epigenetic modifications associated with CFS have not been explored. We examined the DNA methylome in peripheral blood mononuclear cells isolated from CFS patients and healthy controls using the Illumina HumanMethylation450 BeadChip array, controlling for invariant probes and probes overlapping polymorphic sequences. Gene ontology (GO and network analysis of differentially methylated genes was performed to determine potential biological pathways showing changes in DNA methylation in CFS. We found an increased abundance of differentially methylated genes related to the immune response, cellular metabolism, and kinase activity. Genes associated with immune cell regulation, the largest coordinated enrichment of differentially methylated pathways, showed hypomethylation within promoters and other gene regulatory elements in CFS. These data are consistent with evidence of multisystem dysregulation in CFS and implicate the involvement of DNA modifications in CFS pathology.

  3. German experiences in local fatigue monitoring

    International Nuclear Information System (INIS)

    The ageing management of nuclear power plants (NPP) has gained an increasing importance in the last years. The reasons are mainly due to the international context of extending period of plants operation. Moreover, new scientific discoveries, such as the corrosive influence of the medium on the fatigue process (environmentally assisted fatigue - EAF) play an important role and influence the code development (ASME, EAF code cases). The fatigue damage process takes a central position in ageing mechanisms of components. It must be ensured through appropriate evidence that facilities are being operated under allowable boundary conditions. In the design phase of NPP, fatigue analyses are still based on theoretical considerations and empirical values, which are summarized in the design transient catalogue, necessary for licensing. These analyses aim at proving the admissibility of the loads in terms of stress and fatigue usage. These analyses will also provide the fatigue-relevant positions in the NPP and give a basis for future design improvements and optimization of operating modes. The design transients are in practice conservatively correlated with the real transients occurring during operation. Uncertainties reveal very conservative assumptions regarding forecast temperatures, temperature gradients and frequencies of events. During operation of the plant, it has to be recurrently proved, that the plant is being operated under designed boundary conditions. Moreover, operating signals are constantly acquired to enable a fatigue evaluation. For example, in Germany fatigue evaluation is based on decades of experience and regulatory requirements. The rule KTA 3201.4 [1] establishes the rules for qualified fatigue monitoring. The rule DIN 25475-3 [2] on fatigue monitoring systems is available in draft version. Experience shows that some significant differences occur between the design transients and the real occurred transients during plant operation. The reasons for it

  4. Fatigue

    Science.gov (United States)

    ... Other infections can tire you out, even without obvious symptoms. Parasites in your digestive system, bronchitis, other ... or injections can restore hormone levels to normal. Depression (see fact sheet 558). This is more than ...

  5. Biological Threats

    Science.gov (United States)

    ... Workplace Plans School Emergency Plans Main Content Biological Threats Biological agents are organisms or toxins that can ... for Disease Control and Prevention . Before a Biological Threat Unlike an explosion, a biological attack may or ...

  6. 38 CFR 4.88a - Chronic fatigue syndrome.

    Science.gov (United States)

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Chronic fatigue syndrome... Deficiencies § 4.88a Chronic fatigue syndrome. (a) For VA purposes, the diagnosis of chronic fatigue syndrome requires: (1) new onset of debilitating fatigue severe enough to reduce daily activity to less than...

  7. Fatigue studies of superalloys in Japan

    International Nuclear Information System (INIS)

    In the past 15 years, several national projects were advanced to develop high temperature machinery, such as high temperature gas-cooled reactors, gas turbines and fusion reactors. Before, the studies on the strength of superalloys were rarely carried out, however, by the above research works, superalloys are in rapid progress. Because these machinery are subjected to temperature cycles and vibration stress, the fatigue failure is the main concern in the safety analysis of the components. The purpose of this paper is to summarize the present status of the fatigue research on the alloys for high temperature use in Japan. The superalloys used for gas turbine and HTGR components are listed, and the materials tested were mostly the alloys of nickel base, cobalt base or iron base. In the above national projects, the main purpose was to clarify the high temperature properties including fatigue properties, to develop the method of forecasting the life span and to develop better materials. As the topics about the fatigue research on superalloys, the development of the method for forecasting the life span, the effect of directional solidification, coating and HIP process on the fatigue strength of gas turbine materials, the effect of helium and aging on the fatigue strength of HTGR materials, the fatigue strength of weldment of HTGR materials and others are reported. (Kako, I.)

  8. Psychostimulants for cancer-related fatigue.

    Science.gov (United States)

    Breitbart, William; Alici, Yesne

    2010-08-01

    Fatigue is a highly prevalent and distressing symptom associated with significant psychological and functional morbidity and decreased quality of life among patients with cancer. Despite its impact on patients and caregivers, fatigue is underreported and underrecognized, and remains untreated among patients with cancer because of various patient- and clinician-related factors. In addition to assessment for potentially reversible medical causes or medications exacerbating fatigue, and the implementation of nonpharmacologic interventions, several pharmacologic treatment options have been considered for the treatment of cancer-related fatigue. Among traditional psychostimulants, methylphenidate has been studied the most and is effective and well tolerated among patients with cancer despite common side effects. Modafinil, a novel psychostimulant commonly referred to as wakefulness-promoting agents as a group, has also been studied and seems to be well tolerated among patients with cancer. A large placebo effect has been reported in most randomized controlled trials with psychostimulants. Thus, randomized placebo-controlled trials with large sample sizes are needed to further assess the efficacy and tolerability of psychostimulants in the treatment of cancer-related fatigue. This article presents a comprehensive review of the use of psychostimulant agents for fatigue among patients with cancer, including an overview of the clinical trials with psychostimulants and of the clinical guidelines available for treatment of cancer-related fatigue. PMID:20870637

  9. Effects of human fatigue on speech signals

    Science.gov (United States)

    Stamoulis, Catherine

    2001-05-01

    Cognitive performance may be significantly affected by fatigue. In the case of critical personnel, such as pilots, monitoring human fatigue is essential to ensure safety and success of a given operation. One of the modalities that may be used for this purpose is speech, which is sensitive to respiratory changes and increased muscle tension of vocal cords, induced by fatigue. Age, gender, vocal tract length, physical and emotional state may significantly alter speech intensity, duration, rhythm, and spectral characteristics. In addition to changes in speech rhythm, fatigue may also affect the quality of speech, such as articulation. In a noisy environment, detecting fatigue-related changes in speech signals, particularly subtle changes at the onset of fatigue, may be difficult. Therefore, in a performance-monitoring system, speech parameters which are significantly affected by fatigue need to be identified and extracted from input signals. For this purpose, a series of experiments was performed under slowly varying cognitive load conditions and at different times of the day. The results of the data analysis are presented here.

  10. COGNITIVE FATIGUE FACILITATES PROCEDURAL SEQUENCE LEARNING

    Directory of Open Access Journals (Sweden)

    Guillermo eBorragán

    2016-03-01

    Full Text Available Enhanced procedural learning has been evidenced in conditions where cognitive control is diminished, including hypnosis, disruption of prefrontal activity and non-optimal time of the day. Another condition depleting the availability of controlled resources is cognitive fatigue. We tested the hypothesis that cognitive fatigue, eventually leading to diminished cognitive control, facilitates procedural sequence learning. In a two-day experiment, twenty-three young healthy adults were administered a serial reaction time task (SRTT following the induction of high or low levels of cognitive fatigue, in a counterbalanced order. Cognitive fatigue was induced using the Time load Dual-back (TloadDback paradigm, a dual working memory task that allows tailoring cognitive load levels to the individual's optimal performance capacity. In line with our hypothesis, reaction times in the SRTT were faster in the high- than in the low-level fatigue condition, and performance improvement showed more of a benefit from the sequential components than from motor. Altogether, our results suggest a paradoxical, facilitating impact of cognitive fatigue on procedural motor sequence learning. We propose that facilitated learning in the high-level fatigue condition stems from a reduction in the cognitive resources devoted to cognitive control processes that normally oppose automatic procedural acquisition mechanisms.

  11. Fatigue Properties of Cast Magnesium Wheels

    Science.gov (United States)

    Li, Zhenming; Luo, Alan A.; Wang, Qigui; Peng, Liming; Zhang, Peng

    2016-05-01

    This paper investigates the fatigue properties and deformation behavior of a newly developed Mg-2.96Nd-0.21Zn-0.39Zr magnesium alloy wheel in both as-cast and T6 conditions. Compared with the as-cast alloy, the T6-treated alloy shows a significant increase in fatigue strength and cyclic stress amplitude. This is believed to be attributed to the change of defect type from porosity to oxides and the increased matrix strength in the T6 (peak-aged) condition. For the as-cast alloy wheel, fatigue failure mainly originated from the cast defects including porosity, oxide film, and inclusion at or near the sample surface. In the T6-treated alloy, however, oxides and inclusions or slip bands initiate the fatigue cracks. Solution treatment appears to reduce or eliminate the shrinkage porosity because of grain growth and dissolution of as-cast eutectic phases in the grain boundaries. The cyclic stress amplitude of the as-cast alloy increases with increasing the number of cycles, while the T6-treated alloy shows cyclic softening after the stress reaches a maximum value. The Coffin-Manson law and Basquin equation can be used to evaluate the life of low cycle fatigue. The developed long crack model and multi-scale fatigue (MSF) models can be used to predict high-cycle fatigue life of the Mg-2.96Nd-0.21Zn-0.39Zr alloys with or without casting defects.

  12. Atomistic mechanisms of fatigue in nanotwinned metals

    International Nuclear Information System (INIS)

    We investigate the fatigue behavior of nanotwinned Cu using a combination of molecular statics and molecular dynamics simulations. The presence of nanoscale twins is found to enhance fatigue crack growth resistance. For the twin-free nanocrystalline samples, the fatigue crack propagates by linking the nanovoids that are formed ahead of the crack tip. In the case of the nanotwinned samples, however, it advances as the crack tip alternately blunts and re-sharpens due to dislocation emission and slip. Both detwinning and crack closure are observed in the path of the fatigue crack in nanotwinned samples with a high density of twin boundaries. As the twin number per grain (quantified by the ratio of the mean grain size to the twin boundary spacing d/λ) increases, detwinning increases the dissipated energy of fatigue cracking, leading to enhanced fatigue resistance. The atomistic simulations show that fatigue crack growth in nanotwinned Cu conforms to Paris’ law. In conjunction with the experimental results, we obtain a quantitative estimation of the Paris’ law exponent (∼4.0), which is in agreement with the theoretical predictions from the damage accumulation model

  13. Future directions in fatigue and safety research.

    Science.gov (United States)

    Noy, Y Ian; Horrey, William J; Popkin, Stephen M; Folkard, Simon; Howarth, Heidi D; Courtney, Theodore K

    2011-03-01

    Fatigue is regarded as a major contributor to workplace and highway morbidity and mortality. While the scientific literature is replete with studies that can be traced back more than a hundred years, much remains to be done to improve our knowledge of and ability to alleviate the consequences of fatigue. Moreover, given the dramatic transformation of modern work systems due to a global and 24/7 economy, there is increasing urgency in improving our understanding of fatigue as a safety risk factor, its etiology and management. As a result, a Hopkinton Conference was organized to review the state of knowledge in the area and define future directions for research aimed at preventing or mitigating the consequences of fatigue. The Hopkinton Conference paradigm brings together leading experts on a key research area to define scientific gaps and research needs, and serves as a stimulus for further collaboration. Over the course of several months prior to the conference, participants draft state-of-the-art reviews covering various aspects of the research topic. In this case, five working groups were formed, each charged with developing collaborative manuscripts in a given topic area of interest, as follows: the Link Between Fatigue and Safety, Demographic Issues in Fatigue, Predicting Fatigue, Technological Approaches in the Management of Fatigue, and Organizational Factors in the Management of Fatigue. The participants then convened for a 2 day conference at the Liberty Mutual Research Institute for Safety in Hopkinton to review, debate, and revise the draft manuscripts; examine global issues; and discuss research priorities. The output from this collective effort is captured in this special issue of Accident Analysis and Prevention. PMID:21130212

  14. Interpretation of Hospital Nurse Fatigue Using Latent Profile Analysis.

    Science.gov (United States)

    Drake, Diane Ash; Steege, Linsey M Barker

    2016-01-01

    There has been a lack of consensus in the literature related to the conceptualization, definition, and measurement of hospital nurse fatigue. Using latent profile analysis, the Hospital Nurse Force Theory provided a conceptual format to identify 3 profiles of nurse fatigue from subjective reports of hospital patient care nurses in a survey cohort. All fatigue and adaptation variables demonstrated significant inverse relationships. Describing nurse fatigue in profiles that include measures of acute, chronic, physical, and mental fatigue dimensions provided a new and expanded view of nurse fatigue to monitor trends comprehensively and evaluate fatigue risk management strategies. PMID:27490883

  15. Muscle glycogen stores and fatigue

    DEFF Research Database (Denmark)

    Ørtenblad, Niels; Westerblad, Håkan; Nielsen, Joachim

    2013-01-01

      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...... 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...... pools. Furthermore, each glycogen granule has its own metabolic machinery with glycolytic enzymes and regulating proteins. One pool of such glycogenolytic complexes is localized within the myofibrils in close contact with key proteins involved in the excitation-contraction coupling and Ca2+ release from...

  16. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the...... material strength. For the material strength, the Weibull distribution is assumed, the parameters of which are estimated by a statistical analysis of the experimental tensile strength of steel specimens subjected to different periods of random loads. The statistical analysis shows that, with the...... application of random loads, the initial homogeneous distribution of strength changes to a two-component distribution, reflecting the two-stage fatigue damage. In the crack initiation stage, the strength increases initially and then decreases, while an abrupt decrease of strength is seen in the crack...

  17. Approche variationnelle de la fatigue

    OpenAIRE

    Jaubert, André

    2006-01-01

    En adoptant un principe de moindre énergie, une énergie de surface de type Dugdale-Barenblatt et une condition d'irréversibilité, on construit un modèle de propagation de fissure opérant aussi bien sous chargement monotone que sous chargement cyclique. Plus précisément, à travers l'exemple du décollement d'un film mince, on montre tout d'abord qu'en utilisant une énergie de surface de Griffith, il est impossible de rendre compte du phénomène de fatigue. Par contre, avec une énergie de surface...

  18. Evaluation of micro fatigue crack growth under equi-biaxial stress by membranous pressure fatigue test

    International Nuclear Information System (INIS)

    For preventing nuclear power plant (NPP) accidents, NPPs are required to ensure system safety in long term safe operation under aging degradation. Now, fatigue accumulation is one of major ageing phenomena and are evaluated to ensure safety by design fatigue curve that are based on the results of uniaxial fatigue tests. On the other hand, thermal stress that occurs in piping of actual components is not uniaxial but equi-biaxial. For accurate evaluation, it is required to conform real circumstance. In this study, membranous pressure fatigue test was conducted to simulated equi-biaxial stress. Crack initiation and crack growth were examined by replica investigation. Calculation result of equivalent stress intensity factor shows crack growth under equi-biaxial stress is faster than under uniaxial stress. It is concluded that equi-biaxial fatigue behavior should be considered in the evaluation of fatigue crack initiation and crack growth. (author)

  19. High-temperature fatigue in metals

    Science.gov (United States)

    Halford, G. R.

    1982-01-01

    The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range Partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed.

  20. Predicting Fatigue Lives Under Complex Loading Conditions

    Science.gov (United States)

    Mcgaw, Michael A.; Nelson, R. S.; Janitor, L. A.

    1995-01-01

    Cyclic Damage Accumulation (CDA) computer program performs high-temperature, low-cycle-fatigue life prediction for materials analysis. Designed to account for effects on creep-fatigue life of complex loadings involving such factors as thermomechanical fatigue, hold periods, wave-shapes, mean stresses, multiaxiality, cumulative damage, coatings, and environmental attack. Several features practical for application to actual component analysis using modern finite-element or boundary-element methods. Although developed for use in predicting crack-initiation lifetimes of gas-turbine-engine materials, also applied to other materials as well. Written in FORTRAN 77.

  1. Fatigue of continuous fiber reinforced metallic materials

    Science.gov (United States)

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

    1993-01-01

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

  2. Fatigue management in 12-hour shift operations

    International Nuclear Information System (INIS)

    The adoption of 12-hour shift operations has been widespread in many 24-hour industrial work environments. This move has fatigue implications that must be understood and considered when staffing, training and scheduling personnel. This presentation will highlight the pros and cons of the 12-hour shift and describe strategies to ensure levels of fatigue risk that are acceptable to all stakeholders. The importance of striking a balance between personnel needs and operational requirements will be discussed. An overview of the role of fatigue risk management systems will also be presented. (author)

  3. Fatigue of High Purity Copper Wire

    OpenAIRE

    Tanabe, N.; Kurosaka, A.; Suzuki, K.; Kohno, O.

    1995-01-01

    The fatigue properties of 7N, OFC and Tough-Pitch copper wires were evaluated by a rotational bending method. 7N copper wires, having RRR300K/4.2K of 7600, were produced by electro-refining, vacuum melting, zonerefining followed by suitable drawing processes, using 4N class commercial OFC plates as the starting material. The fatigue failure cycles of 7N copper increased with an increased pause period imposed during the fatigue test after 5x106 cycles. Remarkable recrystallizations initiated f...

  4. High-speed Stochastic Fatigue Testing

    DEFF Research Database (Denmark)

    Brincker, Rune; Sørensen, John Dalsgaard

    1990-01-01

    Good stochastic fatigue tests are difficult to perform. One of the major reasons is that ordinary servohydraulic loading systems realize the prescribed load history accurately at very low testing speeds only. If the speeds used for constant amplitude testing are applied to stochastic fatigue...... testing, quite unacceptable errors are introduced. Usually this problem is solved by running the tests at very low speeds and by editing the load history in order to reduce the duration of the test. In this paper a new method for control of stochastic fatigue tests is proposed. It is based on letting the...... allowable speed by a factor from 10 to 30....

  5. Fatigue crack growth detect, assess, avoid

    CERN Document Server

    Richard, Hans Albert

    2016-01-01

    This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.

  6. Composite materials: Fatigue and fracture. Vol. 3

    Science.gov (United States)

    O'Brien, T. K. (Editor)

    1991-01-01

    The present volume discusses topics in the fields of matrix cracking and delamination, interlaminar fracture toughness, delamination analysis, strength and impact characteristics, and fatigue and fracture behavior. Attention is given to cooling rate effects in carbon-reinforced PEEK, the effect of porosity on flange-web corner strength, mode II delamination in toughened composites, the combined effect of matrix cracking and free edge delamination, and a 3D stress analysis of plain weave composites. Also discussed are the compression behavior of composites, damage-based notched-strength modeling, fatigue failure processes in aligned carbon-epoxy laminates, and the thermomechanical fatigue of a quasi-isotropic metal-matrix composite.

  7. Fatigue properties of duplex stainless steel

    OpenAIRE

    Turrel, Benjamin; Luna Garcia, Jordi; Andraschko, Stephan

    2009-01-01

    PFC presentat a Oslo University College The aim of the project is to study fatigue properties of duplex stainless steel used for a bridge. The samples had to be tested and the results have to be compared with the theory, studied before. Six specimens have been broken by tensile fatigue testing machine in order to get more knowledge about the lifetime and the behavior under dynamic stress and not only for welded parts. Out of this new knowledge a new fatigue curve for this ma...

  8. Fatigue damage evolution in structural materials above and below the fatigue limit

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Obrtlík, Karel; Vašek, Alois; Degallaix, S.

    Rotterdam: A.A.Balkema, 1999, s. 319-327. ISBN 90-5410-969-6. [International Conference on the importance of understanding the fundamentals of the fatigue process in counteracting its effects in engineering components and structures, and to reflect on the contributions of K.J.Miller "Engineering Against Fatigue". Sheffield (GB), 17.03.1997-21.03.1997] R&D Projects: GA ČR GA106/95/1529 Subject RIV: JL - Materials Fatigue, Friction Mechanics

  9. High-cycle fatigue / low-cycle fatigue interactions in Ti-6Al-4V

    OpenAIRE

    Knipling, Keith Edward

    2002-01-01

    The largest single cause of failure in fan and compressor components in the cold frontal sections of commercial and military gas turbine engines has been attributed to high cycle fatigue (HCF). Additionally, both high-cycle fatigue (HCF) and low-cycle fatigue (LCF) loadings are widely recognized as unavoidable during operation of these components and because the classic Linear Damage Rule (LDR) neglects to account for the synergistic interaction between these damage contributors, dangerous o...

  10. Fatigue Test Design: Scenarios for Biaxial Fatigue Testing of a 60-Meter Wind Turbine Blade

    Energy Technology Data Exchange (ETDEWEB)

    Post, Nathan [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-07-01

    Current practice in commercial certification of wind turbine blades is to perform separate flap and lead-lag fatigue tests. The National Renewable Energy Laboratory has been researching and evaluating biaxial fatigue testing techniques and demonstrating various options, typically on smaller-scale test articles at the National Wind Technology Center. This report evaluates some of these biaxial fatigue options in the context of application to a multimegawatt blade certification test program at the Wind Technology Testing Center in Charlestown, Massachusetts.

  11. Fatigue behaviour and energy dissipation of a nodular cast iron in ultrasonic fatigue loading

    Directory of Open Access Journals (Sweden)

    H.Q. Xue

    2006-08-01

    Full Text Available Purpose: In the current research, fatigue tests of cast iron (GS51 have been conducted using the ultrasonicfatigue system and monitored by an advanced infrared imaging system in real time. Fatigue damage processeshas been observed and analyzed. Furthermore, heat condition effect has been to analyze.Design/methodology/approach: Fatigue behaviour in the very high cycle regime of 1010 cycles wereinvestigated with a cast iron (GS51 under ultrasonic fatigue test system in ambient air at room temperaturewith a stress ratio R=-1. The influence of frequency was examined by comparing similar data generated onconventional servo hydraulic test systems. An infrared camera was also used to record specimen temperaturesat various load levels caused by internal damping due to cycling at a very high frequency.Findings: The S-N curves obtained show that fatigue failure occurred beyond 109 cycles, fatigue limit does notexist for the cast iron and there is no evidence of frequency effect on the test results. A detailed study on fatiguespecimens subjected to ultrasonic frequency shows that the temperature evolution of the cast iron specimen isvery evident, the temperature increased just at the beginning of the test, the temperature increased depending onthe maximum stress amplitude.Research limitations/implications: Ultrasonic fatigue test methodology had been applied extensively inexploring fatigue lives at very high cycle regime. However, it is a predominant problem that the thermal energydissipation results in increasing of temperature of specimen at very high frequency fatigue experiment. In orderto investigate the heat dissipation of ultrasonic fatigue specimen and understand the influence of temperatureevolution on the fatigue properties, it is necessary to obtain the temperature response of vibratory specimen.Originality/value: Early stage of damage of the cast iron which lead to crack initiation and micro crack growthare characterized by local microstructure

  12. Combined Cycle Fatigue Investigation Based on Energy Principle

    OpenAIRE

    Kalynenko Mykyta

    2016-01-01

    We present a modified energy-principle based model of fatigue damage accumulation in high temperature alloys usually used in gas turbine engine under combined high cycle fatigue and low cycle fatigue (LCF/HCF) loading conditions. Our model is based on the energy principle which includes a modified approximation formula that describes fatigue crack origin depending on the relative amplitude of stress intensity in the ranges of both high- and low-cycle fatigue under non-isothermal loading. Func...

  13. Uncertainty on Fatigue Damage Accumulation for Composite Materials

    OpenAIRE

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2009-01-01

    In the present paper stochastic models for fatigue damage accumulation for composite materials are presented based on public available constant and variable amplitude fatigue tests. The methods used for estimating the SN-curve and accumulated fatigue damage are presented. In the present paper stochastic models for fatigue damage accumulation for composite materials are presented based on public available constant and variable amplitude fatigue tests. The methods used for estimating the SN-...

  14. FACOMS - Fatigue und Kognition bei MS - eine Langzeitstudie

    OpenAIRE

    Lang, Charlotte

    2013-01-01

    Objective: prospective multi-center study to define subjective and objective experienced fatigue in MS in the course of two years by addressing the following questions: (1) How does fatigue influence the clinical, behavioral and cognitive variables in the early progress of the disease? (2) What factors need to be defined that contribute to fatigue in MS? (3) How and above all do fatigue and personality correlate? (4) Does depression play a significant role in the development of fatigue in MS?...

  15. Effects of Local and Widespread Muscle Fatigue on Movement Timing

    OpenAIRE

    Cowley, Jeffrey C.; Dingwell, Jonathan B.; Gates, Deanna H.

    2014-01-01

    Repetitive movements can cause muscle fatigue, leading to motor reorganization, performance deficits, and/or possible injury. The effects of fatigue may depend on the type of fatigue task employed, however. The purpose of this study was to determine how local fatigue of a specific muscle group versus widespread fatigue of various muscle groups affected the control of movement timing. Twenty healthy subjects performed an upper-extremity low-load work task similar to sawing for 5 continuous min...

  16. The Corrosion Fatigue Properties of High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    CHEN Shuanfa; ZHENG Mulian; LIAO Weidong; WANG Binggang

    2005-01-01

    With the loading test equipment of corrosion fatigue specially designed, the corrosion fatigue characteristics of high performance concrete (HPC) withstanding the interaction of third point fatigue loading and Na2SO4 solution were investigated and analyzed. The experimental results indicate that water-binder ratio evidently influences the corrosion fatigue characteristics of HPC, and a moderate quantitative fine mineral admixture enhances the corrosion fatigue resistance of HPC. The effect is more significant when fly ash and silica fume are added.

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

    International Nuclear Information System (INIS)

    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

  18. 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)

  19. Development and characterization of fatigue resistant aramid reinforced aluminium laminates (ARALL) for fatigue critical aircraft components

    International Nuclear Information System (INIS)

    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. (author)

  20. Investigation and analysis on fatigue status of military pilots

    Directory of Open Access Journals (Sweden)

    Jian-sheng GUO

    2012-03-01

    Full Text Available Objective To investigate the fatigue status and its characteristics and influential factors of military pilots. Methods Questionnaire survey was conducted on 924 military pilots by using Fatigue Assessment Instrument (FAI and Fatigue Scale (FS-14, χ2 test and Pearson correlation analysis were performed on the data results with SPSS 17.0 software. Results The findings of fatigue status indicated 343 subjects (37.1% with positive fatigue symptoms and 581 subjects (62.9% with negative fatigue symptoms. FAI factor 1 (severity of fatigue, factor 2 (mental fatigue factor, factor 3 (consequence of fatique and the total score, FS-14 factor 1 (physical fatigue factor and the total score in fatigue-positive group were all higher than those in fatiguenegative group, and the differences were all statistically significant (P 0.05 in the possibility of developing fatigue symptoms between subjects with different aircraft types. Age and flight time were positively correlated with factor 1 and total score in FAI and factor 1, factor 2 and total score in FS-14. However, the aircraft type was associated with neither the individual factors and total score in FAI nor the individual factors and total score in FS-14. Conclusion It is common for military pilots to develop fatigue symptoms, characterized by obvious manifestations of severity, environmental specificity, consequences of fatigue and physical fatigue, and the possibilities of developing fatigue symptoms for different ages and flight time were different.

  1. Fatigue failure by flow-induced vibration

    International Nuclear Information System (INIS)

    The mechanism of fatigue failure by flow-induced vibration was studied by using a newly developed small wind tunnel. The necessary conditions of flow-induced vibration for a carbon steel specimen attached to a larger styrofoam cylinder were first investigated. Possible methods to detect indications of fatigue crack initiation and propagation were sought. A fatigue life prediction method was also developed. The change in natural frequency and amplitude of the test cylinder and strain history at the prospective crack initiation sites were measured. The 0.45 C steel specimen contained an artificial small hole which is expected to become the crack initiation site. A small portable service strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project was used to monitor the variation of strains due to crack growth from the small hole. Fatigue damage accumulation based on Miner's rule was calculated and compared with the experimental results. (author)

  2. Chronic Fatigue Syndrome (CFS): Childhood Adversity

    Science.gov (United States)

    ... childhood maltreatment. In particular, for women, emotional and sexual abuse during childhood was associated with a greater risk ... risk for chronic fatigue syndrome: results from a population-based study. Arch Gen Psychiatry. 2006 Nov;63( ...

  3. LIFE PREDICTION APPROACH FOR RANDOM MULTIAXIAL FATIGUE

    Institute of Scientific and Technical Information of China (English)

    Wang Lei; Wang Dejun

    2005-01-01

    According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results.

  4. Human Muscle Fatigue Model in Dynamic Motions

    CERN Document Server

    Ma, Ruina; Bennis, Fouad; Ma, Liang

    2012-01-01

    Human muscle fatigue is considered to be one of the main reasons for Musculoskeletal Disorder (MSD). Recent models have been introduced to define muscle fatigue for static postures. However, the main drawbacks of these models are that the dynamic effect of the human and the external load are not taken into account. In this paper, each human joint is assumed to be controlled by two muscle groups to generate motions such as push/pull. The joint torques are computed using Lagrange's formulation to evaluate the dynamic factors of the muscle fatigue model. An experiment is defined to validate this assumption and the result for one person confirms its feasibility. The evaluation of this model can predict the fatigue and MSD risk in industry production quickly.

  5. Alarm fatigue: a patient safety concern.

    Science.gov (United States)

    Sendelbach, Sue; Funk, Marjorie

    2013-01-01

    Research has demonstrated that 72% to 99% of clinical alarms are false. The high number of false alarms has led to alarm fatigue. Alarm fatigue is sensory overload when clinicians are exposed to an excessive number of alarms, which can result in desensitization to alarms and missed alarms. Patient deaths have been attributed to alarm fatigue. Patient safety and regulatory agencies have focused on the issue of alarm fatigue, and it is a 2014 Joint Commission National Patient Safety Goal. Quality improvement projects have demonstrated that strategies such as daily electrocardiogram electrode changes, proper skin preparation, education, and customization of alarm parameters have been able to decrease the number of false alarms. These and other strategies need to be tested in rigorous clinical trials to determine whether they reduce alarm burden without compromising patient safety. PMID:24153215

  6. Multiple Surveys of Students and Survey Fatigue

    Science.gov (United States)

    Porter, Stephen R.; Whitcomb, Michael E.; Weitzer, William H.

    2004-01-01

    This chapter reviews the literature on survey fatigue and summarizes a research project that indicates that administering multiple surveys in one academic year can significantly suppress response rates in later surveys. (Contains 4 tables.)

  7. Fatigue modeling of materials with complex microstructures

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2011-01-01

    phenomenological model of fatigue damage growth. As a result, the fatigue lifetime of materials with complex structures can be determined as a function of the parameters of their structures. As an example, the fatigue lifetimes of wood modeled as a cellular material with multilayered, fiber reinforced walls were......A new approach and method of the analysis of microstructure-lifetime relationships of materials with complex structures is presented. The micromechanical multiscale computational analysis of damage evolution in materials with complex hierarchical microstructures is combined with the...... determined for different parameters of wood microstructures. In so doing, 3D hierarchical finite element models of softwood, and a computational technique, including the repeating restart and model change procedures, have been employed to model the fatigue response of latewood....

  8. Fatigue (PDQ®)—Health Professional Version

    Science.gov (United States)

    Expert-reviewed information summary about fatigue, a condition marked by extreme tiredness and inability to function because of lack of energy, often seen as a complication of cancer or its treatment.

  9. Risers. Fatigue of steel catenary risers

    Energy Technology Data Exchange (ETDEWEB)

    Croutelle, Y.; Le Cunff, C.; Biolley, F. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France)

    2002-12-01

    Steel catenary risers (SCR) are used in the Golf of Mexico (Auger,...), Brazil (Marlim), and soon West Africa (Bonga). Some risers have been instrumented to better understand their behaviour, for instance in the Allegheny Field or the Marlim field. One of the main problem is the interaction between the riser and the soil, since it may create high stresses when the riser is excited by top motion or Vortex-Induced Vibrations (VIV), leading to low fatigue life near the Touch Down Point (TDP). The objective of the present paper is to analyze the influence of the soil on the fatigue of a SCR. A riser configuration is defined and parametric studies are conducted on the soil stiffness, the riser characteristics and the geographic location. The fatigue considered is either due to currents (VIV) or waves (top excitation). For the latter case, several fatigue methods are also compared. (authors)

  10. Thermal-mechanical low-cycle fatigue under creep-fatigue interaction on type 304 stainless steel

    International Nuclear Information System (INIS)

    Thermal-mechanical low-cycle fatigue tests as well as isothermal low-cycle fatigue tests were carried out on Type 304 stainless steels in order to investigate the fatigue failure properties under creep-fatigue interactions from the viewpoint of correlations between the failure life, and mode. Also an attempt was made to apply the strain rate partitioning method to thermal fatigue life prediction. The results are presented and discussed. (author)

  11. Fatigue-Prone Details in Steel Bridges

    OpenAIRE

    Mohsen Heshmati; Mohammad Al-Emrani; Reza Haghani

    2012-01-01

    This paper reviews the results of a comprehensive investigation including more than 100 fatigue damage cases, reported for steel and composite bridges. The damage cases are categorized according to types of detail. The mechanisms behind fatigue damage in each category are identified and studied. It was found that more than 90% of all reported damage cases are of deformation-induced type and generated by some kind of unintentional or otherwise overlooked interaction between different load-carr...

  12. Effect Of Solidification Speed On Fatigue Properties

    Science.gov (United States)

    Mccay, M. H.; Schmidt, D. D.; Hamilton, W. D.; Alter, W. S.; Parr, R. A.

    1989-01-01

    Fast solidification increases fatigue life, but failure distribution becomes less predictable. Report describes effects of rate of solidification on nickel-based super-alloy MAR-M246(Hf) used in turbine blades. Based on experiments in which specimens directionally solidified at 5 cm/h and 30 cm/h, then tested for high cycle fatigue. Specimens also inspected by energy-dispersive x-ray (EDX) analysis and optical and electron microscopy.

  13. Evaluation of fatigue performance at different temperatures

    OpenAIRE

    Minhoto, Manuel; Pais, Jorge; Pereira, Paulo

    2009-01-01

    The fatigue performance of asphalt mixtures is used to predict pavement life to control the cracking in the asphalt layers. The design of an asphalt pavement is usually made for a specific temperature, what is intended to represent the pavement behaviour throughout a whole year. For damage analysis during a year, along which the pavement temperature constant-ly varies, it is necessary to calculate the fatigue performance of pavements at a wide range of temperatures. Thus, this paper presents ...

  14. Human Muscle Fatigue Model in Dynamic Motions

    OpenAIRE

    Ma, Ruina; Chablat, Damien; Bennis, Fouad; Ma, Liang

    2012-01-01

    Human muscle fatigue is considered to be one of the main reasons for Musculoskeletal Disorder (MSD). Recent models have been introduced to define muscle fatigue for static postures. However, the main drawbacks of these models are that the dynamic effect of the human and the external load are not taken into account. In this paper, each human joint is assumed to be controlled by two muscle groups to generate motions such as push/pull. The joint torques are computed using Lagrange's formulation ...

  15. Cancer-related fatigue: a review.

    Science.gov (United States)

    Campos, Maira Paschoin de Oliveira; Hassan, Benjamin Joseph; Riechelmann, Rachel; Del Giglio, Auro

    2011-01-01

    Cancer-related fatigue is the most prevalent cancer symptom, reported in 50%-90% of patients and severely impacts quality of life and functional capacity. The condition remains underreported and often goes untreated. Guidelines suggest screening for fatigue at the initial visit, when the diagnosis of advanced disease is made, and at each chemotherapy session, as well as the identification of treatable contributing factors such as anemia, hypothyroidism, depression and sleep disorders. Brief assessment tools such as the Brief Fatigue Inventory or the Visual Analog Scale may be appropriate in the initial scoring of fatigue severity, but the initial approach to treatment usually requires a more comprehensive assessment, education, and the determination of an individualized treatment plan. Patients with moderate or severe fatigue may benefit from both pharmacological and non-pharmacological interventions, whereas mild fatigue that does not interfere with quality of life can be treated with non-pharmacological measures alone. Non-pharmacological measures that have shown to be promising include cognitive-behavioral interventions such as energy conservation and activity management (ECAM), exercise and perhaps sleep therapy. Many other modalities may be beneficial and can be used on an individual basis, but there is insufficient evidence to promote any single treatment. Pharmacological therapies that have shown to be promising include the psycho-stimulants methylphenidate and dexmethylphenidate, modafinil (in severely fatigued patients only), and erythropoietin-stimulating agents in patients with chemotherapy-associated anemia and hemoglobin levels side effects and at low cost, for the treatment of physical and mental cancer-related fatigue. PMID:21537710

  16. Modified low-cycle fatigue (LCF) test

    OpenAIRE

    M. Maj; A. Klasik; K. Pietrzak; D. Rudnik

    2015-01-01

    The fatigue test results obtained by the common low-cycle fatigue test (LCF) and its modified MLCF counterpart were presented. A satisfactory agreement of results was achieved for the two selected materials. With the MLCF method it is possible to examine from ten to twenty parameters using one single sample only. These parameters characterise the tested material in terms of its mechanical properties under the conditions of mechanical loads. Simultaneously, the study shows the implementation o...

  17. Improvement of fatigue properties of orthotropic decks

    Czech Academy of Sciences Publication Activity Database

    Frýba, Ladislav; Urushadze, Shota

    2011-01-01

    Roč. 33, č. 4 (2011), s. 1166-1169. ISSN 0141-0296 R&D Projects: GA ČR GA103/08/1340; GA MŠk(CZ) 7E08098 Grant ostatní: BRIFAG -Bridge Fatigue Guidance(XE) RFSR_CT-2008-00033 Institutional research plan: CEZ:AV0Z20710524 Keywords : orthotropic deck * fatigue * prolonged life Subject RIV: JM - Building Engineering Impact factor: 1.351, year: 2011

  18. Micromechanical Simulation for Fatigue Damage Incubation

    OpenAIRE

    Li, Tong

    2011-01-01

    Micromechanical simulations are conducted to quantify the influence of microstructure attributes to the formation of small fatigue cracks. Three wrought aluminum alloys (7075-T651, 2024-T3, virtual material) with fractured particle are studied to quantify the influence of material’s yield strength and ultimate strength to material’s fatigue resistance. Laser Engineered Net Shaping (LENS) material with pores of various spatial distribution and particles are simulated for the microplasticity an...

  19. Fatigue and fracture research in composite materials

    Science.gov (United States)

    Obrien, T. K.

    1982-01-01

    The fatigue, fracture, and impact behavior of composite materials are investigated. Bolted and bonded joints are included. The solutions developed are generic in scope and are useful for a wide variety of structural applications. The analytical tools developed are used to demonstrate the damage tolerance, impact resistance, and useful fatigue life of structural composite components. Standard tests for screening improvements in materials and constituents are developed.

  20. Fatigue Tests with Densit Cylinders - D4

    DEFF Research Database (Denmark)

    Ellegaard, Peter

    This report contains descriptions and results of a series of fatigue tests performed during the autumn of 2005 at the Stuctural Research Laboratory, Aalborg University. Cylinders with a diameter of 45 mm and a height of 90 mm were used as test specimens; the material was Densit Ducorit D4. Four...... cylinders were tested statically under compression and the rest of the cylinders (30) were tested under fatigue conditions with a load varying sinusoidally....

  1. 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.

  2. Damage evolution during fatigue in structural materials

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Man, Jiří; Petrenec, Martin

    2012-01-01

    Roč. 1, August (2012), s. 3-12. ISSN 2211-8128. [International Congress on Metallurgy and Materials - SAM/CONAMET 2011 /11./. Rosario, 18.10.2011-21.10.2011] R&D Projects: GA ČR GA106/09/1954 Institutional support: RVO:68081723 Keywords : cyclic plasticity * crack nucleation * crack growth * fatigue damage Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Midodrine treatment for chronic fatigue syndrome

    OpenAIRE

    Naschitz, J; Dreyfuss, D; Yeshurun, D.; Rosner, I

    2004-01-01

    The long term results of midodrine treatment in a patient having debilitating chronic fatigue syndrome (CFS) are reported. Midodrine treatment, directed at the autonomic nervous system, resulted in correction of the dysautonomia followed by improvement of fatigue. This finding is consistent with the hypothesis that dysautonomia plays a major part in the pathophysiology of CFS and that therapies directed at the autonomic nervous system may be effective in the treatment of CFS.

  4. Understanding Muscle Dysfunction in Chronic Fatigue Syndrome

    Directory of Open Access Journals (Sweden)

    Gina Rutherford

    2016-01-01

    Full Text Available Introduction. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME is a debilitating disorder of unknown aetiology, characterised by severe disabling fatigue in the absence of alternative diagnosis. Historically, there has been a tendency to draw psychological explanations for the origin of fatigue; however, this model is at odds with findings that fatigue and accompanying symptoms may be explained by central and peripheral pathophysiological mechanisms, including effects of the immune, oxidative, mitochondrial, and neuronal pathways. For example, patient descriptions of their fatigue regularly cite difficulty in maintaining muscle activity due to perceived lack of energy. This narrative review examined the literature for evidence of biochemical dysfunction in CFS/ME at the skeletal muscle level. Methods. Literature was examined following searches of PUB MED, MEDLINE, and Google Scholar, using key words such as CFS/ME, immune, autoimmune, mitochondria, muscle, and acidosis. Results. Studies show evidence for skeletal muscle biochemical abnormality in CFS/ME patients, particularly in relation to bioenergetic dysfunction. Discussion. Bioenergetic muscle dysfunction is evident in CFS/ME, with a tendency towards an overutilisation of the lactate dehydrogenase pathway following low-level exercise, in addition to slowed acid clearance after exercise. Potentially, these abnormalities may lead to the perception of severe fatigue in CFS/ME.

  5. Understanding Muscle Dysfunction in Chronic Fatigue Syndrome.

    Science.gov (United States)

    Rutherford, Gina; Manning, Philip; Newton, Julia L

    2016-01-01

    Introduction. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a debilitating disorder of unknown aetiology, characterised by severe disabling fatigue in the absence of alternative diagnosis. Historically, there has been a tendency to draw psychological explanations for the origin of fatigue; however, this model is at odds with findings that fatigue and accompanying symptoms may be explained by central and peripheral pathophysiological mechanisms, including effects of the immune, oxidative, mitochondrial, and neuronal pathways. For example, patient descriptions of their fatigue regularly cite difficulty in maintaining muscle activity due to perceived lack of energy. This narrative review examined the literature for evidence of biochemical dysfunction in CFS/ME at the skeletal muscle level. Methods. Literature was examined following searches of PUB MED, MEDLINE, and Google Scholar, using key words such as CFS/ME, immune, autoimmune, mitochondria, muscle, and acidosis. Results. Studies show evidence for skeletal muscle biochemical abnormality in CFS/ME patients, particularly in relation to bioenergetic dysfunction. Discussion. Bioenergetic muscle dysfunction is evident in CFS/ME, with a tendency towards an overutilisation of the lactate dehydrogenase pathway following low-level exercise, in addition to slowed acid clearance after exercise. Potentially, these abnormalities may lead to the perception of severe fatigue in CFS/ME. PMID:26998359

  6. Micromechanisms of thermomechanical fatigue: A comparison with isothermal fatigue

    Science.gov (United States)

    Bill, R. C.

    1986-01-01

    Thermomechanical Fatigue (TMF) experiments were conducted on Mar-M 200, B-1900, and PWA-1480 (single crystals) over temperature ranges representative of gas turbine airfoil environments. The results were examined from both a phenomenological basis and a micromechanical basis. Depending on constituents present in the superalloy system, certain micromechanisms dominated the crack initiation process and significantly influenced the TMF lives as well as sensitivity of the material to the type TMF cycle imposed. For instance, high temperature cracking around grain boundary carbides in Mar-M 200 resulted in short in-phase TMF lives compared to either out-of-phase or isothermal lives. In single crystal PWA-1480, the type of coating applied was seen to be the controlling factor in determining sensitivity to the type of TMF cycle imposed. Micromechanisms of deformation were observed over the temperature range of interest to the TMF cycles, and provided some insight as to the differences between TMF damage mechanisms and isothermal damage mechanisms. Finally, the applicability of various life prediction models to TMF results was reviewed. Current life prediction models based on isothermal data must be modified before being generally applied to TMF.

  7. 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

  8. Low cycle fatigue on crack initiation life basis

    International Nuclear Information System (INIS)

    A review is given of the following subjects: A proposed formula, from which the strain cycling fatigue strength can be estimated, on the basis of crack initiation life, from static tensile strength and reduction in area. Relation between crack initiation life and failure life. Distribution of strain cycling fatigue life. Cyclic characteristics of notch root strain and the interrelation between fatigue life of a notched plate subjected to load cycling and fatigue life of an hour-glass shaped specimen subjected to strain cycling. Effect of angular distribution and misalignment in a butt-welded joint on load-controlled low cycle fatigue strength. Fatigue strength ratio of bending to axial strain cycling. Low cycle bending fatigue strength of the fillet welded joint. Fatigue strength of welded tubular conncetions in offshore structures. Creep-fatigue interaction problems for stainless steels. Material constants in the simplified elastic-plastic analysis in ASME Sec. III. (orig.) 891 RW/orig. 892 RKD

  9. High cycle fatigue characteristics of 2124-T851 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    LI Xue; YIN Zhimin; NIE Bo; ZHONG Li; PAN Qinglin; JIANG Feng

    2007-01-01

    The fatigue crack growth rate, fracture toughness and fatigue S-N curve of 2124-T851 aluminum alloy at high cycle fatigue condition were measured and fatigue fracture process and fractography were studied using optical microscopy (OM), X-ray diffraction (XRD) technique, trans-mission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that at room tempera-ture and R = 0.1 conditions, the characteristics of fatigue fracture could be observed. Under those conditions, the fatigue strength and the fracture toughness of a 2124-T851 thick plate is 243 MPa and 29.64 MPa·m1/2,respectively.At high cycle fatigue condition, the higher the stress amplitude,the wider the space between fatigue striations, the faster the rate of fatigue crack developing and going into the intermittent fracture area, and the greater the ratio between the intermittent fracture area and the whole fracture area.

  10. Multimodal MRI and cognitive function in patients with breast cancer prior to adjuvant treatment — The role of fatigue

    Directory of Open Access Journals (Sweden)

    Sanne Menning

    2015-01-01

    This study suggests that cancer-related psychological or biological processes may adversely impact cognitive functioning and associated aspects of brain structure and function before the start of adjuvant treatment. Our findings stress the importance to further explore the processes underlying the expression of fatigue and to study whether it has a contributory role in subsequent treatment-related cognitive decline.

  11. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel

    International Nuclear Information System (INIS)

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  12. Fatigue Lifetime of ADI from Ultimate Tensile Strength to Permanent Fatigue Limit

    Czech Academy of Sciences Publication Activity Database

    Zapletal, J.; Věchet, S.; Kohout, J.; Obrtlík, Karel

    -, č. 1 (2008), s. 40-43. ISSN 0556-171X. [MSMF /5./. Brno, 27.06.2007-29.06.2007] R&D Projects: GA ČR GA106/03/1265 Institutional research plan: CEZ:AV0Z20410507 Keywords : austempered ductile iron * fatigue behaviour * S N curve Subject RIV: JL - Materials Fatigue, Friction Mechanics

  13. Numerical Analysis of Rolling Contact Fatigue Crack Initiation and Fatigue Life Prediction of the Railway Crossing

    NARCIS (Netherlands)

    Xin, L.; Markine, V.L.; Shevtsov, I.

    2015-01-01

    The procedure for analysing rolling contact fatigue crack initiation and fatigue life prediction of the railway turnout crossing is developed. A three-dimensional finite element (FE) model is used to obtain stress and strain results, considering the dynamic effects of wheel-crossing rolling contact.

  14. Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo

    NARCIS (Netherlands)

    F. Garcia-Godoy; R. Frankenberger; U. Lohbauer; A.J. Feilzer; N. Krämer

    2012-01-01

    Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural str

  15. Low cycle fatigue and creep fatigue behavior of alloy 617 at high temperature

    International Nuclear Information System (INIS)

    Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the very high temperature nuclear reactor (VHTR), expected to have an outlet temperature as high as 950 C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanisms and failure life. Continuous cycle fatigue and creep-fatigue testing of Alloy 617 was conducted at 950 C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle fatigue specimens exhibited transgranular cracking. Intergranular cracking was observed in the creep-fatigue specimens and the addition of a hold time at peak tensile strain degraded the cycle life. This suggests that creep-fatigue interaction occurs and that the environment may be partially responsible for accelerating failure. (authors)

  16. The fatigue of high office

    Science.gov (United States)

    Ramsden, Jeremy J.; Naran, Deven

    2007-03-01

    The word frequencies of the speeches of some contemporary politicians have been determined over a decade of office. By fitting Mandelbrot's simple canonical law (a development of Zipf 's law) to the data, the average cybernetic temperature θ was determined for each year of office. Two contrasting cases were examined. The first, that of the British Prime Minister Tony Blair, showed a steady decline of θ punctuated by partial recovery following certain key events such as re-election. The second, that of the Australian Prime Minister John Howard, showed a more uniform temperature. It is suggested that the first case is an example of the phenomenon of fatigue or habituation, inevitable in any complex system rich in equilibrium states, and the partial de-habituation observed is a consequence of a sharp disturbance to the system. Given the relative ease of carrying out the analysis, it could become a routine tool regularly applied to holders of high office to determine their continuing fitness to occupy the office.

  17. Rolling Contact Fatigue of Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Wang, W. [Bournemouth University, Bournemouth, United Kingdom; Wang, Y. [Bournemouth University, Bournemouth, United Kingdom; Hadfield, M. [Bournemouth University, Bournemouth, United Kingdom; Kanematsu, W. [National Institute of Advanced Industrial Science and Technology, Japan; Kirkland, Timothy Philip [ORNL; Jadaan, Osama M. [University of Wisconsin, Platteville

    2006-09-01

    High hardness, low coefficient of thermal expansion and high temperature capability are properties also suited to rolling element materials. Silicon nitride (Si{sub 3}N{sub 4}) has been found to have a good combination of properties suitable for these applications. However, much is still not known about rolling contact fatigue (RCF) behavior, which is fundamental information to assess the lifetime of the material. Additionally, there are several test techniques that are employed internationally whose measured RCF performances are often irreconcilable. Due to the lack of such information, some concern for the reliability of ceramic bearings still remains. This report surveys a variety of topics pertaining to RCF. Surface defects (cracks) in Si{sub 3}N{sub 4} and their propagation during RCF are discussed. Five methods to measure RCF are then briefly overviewed. Spalling, delamination, and rolling contact wear are discussed. Lastly, methods to destructively (e.g., C-sphere flexure strength testing) and non-destructively identify potential RCF-limiting flaws in Si{sub 3}N{sub 4} balls are described.

  18. Integrated Weighted Gene Co-expression Network Analysis with an Application to Chronic Fatigue Syndrome

    OpenAIRE

    Rajeevan Mangalathu S; Suarez Charlyn J; Whistler Toni; Papp Jeanette C; Sobel Eric M; Presson Angela P; Vernon Suzanne D; Horvath Steve

    2008-01-01

    Abstract Background Systems biologic approaches such as Weighted Gene Co-expression Network Analysis (WGCNA) can effectively integrate gene expression and trait data to identify pathways and candidate biomarkers. Here we show that the additional inclusion of genetic marker data allows one to characterize network relationships as causal or reactive in a chronic fatigue syndrome (CFS) data set. Results We combine WGCNA with genetic marker data to identify a disease-related pathway and its causa...

  19. Yang/Qi Invigoration: An Herbal Therapy for Chronic Fatigue Syndrome with Yang Deficiency?

    OpenAIRE

    Pou Kuan Leong; Hoi Shan Wong; Jihang Chen; Kam Ming Ko

    2015-01-01

    According to traditional Chinese medicine (TCM) theory, Yang and Qi are driving forces of biological activities in the human body. Based on the crucial role of the mitochondrion in energy metabolism, we propose an extended view of Yang and Qi in the context of mitochondrion-driven cellular and body function. It is of interest that the clinical manifestations of Yang/Qi deficiencies in TCM resemble those of chronic fatigue syndrome in Western medicine, which is pathologically associated with m...

  20. Fatigue Reliability and Calibration of Fatigue Design Factors for Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Dominguez, Sergio Marquez; Sørensen, John Dalsgaard

    2012-01-01

    Consequences of failure of offshore wind turbines (OWTs) are in general lower than consequences of failure of, e.g., oil & gas platforms. It is reasonable that lower fatigue design factors can be applied for fatigue design of OWTs when compared to other fixed offshore structures. Calibration of...... uncertainties are described by stochastic variables. SN and fracture mechanics approaches are considered for to model the fatigue life. Further, both linear and bi-linear SN-curves are formulated and various approximations are investigated. The acceptable reliability level for fatigue failure of OWTs is...... discussed and results are presented for calibrated optimal fatigue design factors. Further, the influence of inspections is considered in order to extend and maintain a given target safety level....

  1. Comparing Fatigue Life Estimations of Composite Wind Turbine Blades using different Fatigue Analysis Tools

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro; Lennie, Matthew; Branner, Kim;

    2015-01-01

    In this paper, fatigue lifetime prediction of NREL 5MW reference wind turbine is presented. The fatigue response of materials used in selected blade cross sections was obtained by applying macroscopic fatigue approaches and assuming uniaxial stress states. Power production and parked load cases...... suggested by the IEC 61400-1 standard were studied employing different load time intervals and by using two novel fatigue tools called ALBdeS and BECAS+F. The aeroelastic loads were defined thought aeroelastic simulations performed with both FAST and HAWC2 tools. The stress spectra at each layer were...... calculated employing laminated composite theory and beam cross section methods. The Palmgren-Miner linear damage rule was used to calculate the accumulation damage. The theoretical results produced by both fatigue tools proved a prominent effect of analysed design load conditions on the estimated lifetime of...

  2. Subsea rigid jumper design and ⅤⅣ fatigue evaluation

    Institute of Scientific and Technical Information of China (English)

    Wang Jun

    2013-01-01

    The purpose of this paper is to present a design procedure for subsea rigid jumper system including strength and fatigue analysis.Special attention gives to a methodology based on DNV-RP-F105 to evaluate jumper fatigue damage caused by vortex induced vibration (ⅤⅣ).Jumper strength analysis is to determine the jumper configuration which can accommodate various load conditions and all possible span lengths driven by installation tolerances of connected subsea structures.Fatigue analysis includes two parts:thermal fatigue and ⅤⅣ fatigue.This paper presents the procedure of ⅤⅣ fatigue damage calculation.An example is given to illustrate above methodologies.

  3. Comparison of Fatigue Properties and Fatigue Crack Growth Rates of Various Implantable Metals

    Directory of Open Access Journals (Sweden)

    Yoshimitsu Okazaki

    2012-12-01

    Full Text Available The fatigue strength, effects of a notch on the fatigue strength, and fatigue crack growth rate of Ti-15Zr-4Nb-4Ta alloy were compared with those of other implantable metals. Zr, Nb, and Ta are important alloying elements for Ti alloys for attaining superior long-term corrosion resistance and biocompatibility. The highly biocompatible Ti-15Zr-4Nb-4Ta alloy exhibited an excellent balance between strength and ductility. Its notched tensile strength was much higher than that of a smooth specimen. The strength of 20% cold-worked commercially pure (C.P. grade 4 Ti was close to that of Ti alloy. The tension-to-tension fatigue strength of an annealed Ti-15Zr-4Nb-4Ta rod at 107 cycles was approximately 740 MPa. The fatigue strength of this alloy was much improved by aging treatment after solution treatment. The fatigue strengths of C.P. grade 4 Ti and stainless steel were markedly improved by 20% cold working. The fatigue strength of Co-Cr-Mo alloy was markedly increased by hot forging. The notch fatigue strengths of 20% cold-worked C.P. grade 4 Ti, and annealed and aged Ti-15Zr-4Nb-4Ta, and annealed Ti-6Al-4V alloys were less than those of the smooth specimens. The fatigue crack growth rate of Ti-15Zr-4Nb-4Ta was the same as that of Ti-6Al-4V. The fatigue crack growth rate in 0.9% NaCl was the same as that in air. Stainless steel and Co-Cr-Mo-Ni-Fe alloy had a larger stress-intensity factor range (ΔK than Ti alloy.

  4. Damage mechanism during the fatigue process

    International Nuclear Information System (INIS)

    During of the complex process of the fatigue damage several stages are evinced. Each stage is characterized by certain damage mechanisms having a more or less known regularity. Generally, the fatigue damage can be described by a Woehler curve. The dislocation mobility, their capacity to accumulate and the inner tensions have a major influence on the fatigue damage process initiation. In this paper some results regarding the evolutions of inner second order tensions, the dislocations density and micro-hardness in the superficial layer of some metallic materials during fatigue process are presented. The fatigue tests were performed in air, with and without presence of a magnetic field, and corroding medium (water solution of NaCl 3%). The OL52-2K steel samples were tested to fatigue, using an alternate symmetric cycle with bending at constant moment and a tensions level of 280·106 N/m2. In the superficial layer of tested samples the structure modification by X-ray diffractometer (DRON-3), ultra-sound device (DI-4T) and micro-hardness-meter have been evinced. The diffraction line widthB220 is proportional to the level of the inner second order tensions. The distribution of X-ray diffracted intensity within the (110) interference fringe is influenced by the presence of dislocations, namely, by separation of mosaic blocks into subblocks. The level of the dislocation density in the crystalline lattice was estimated by the ratio (Imin/Imax)220. Using the potentiometer PAR 210 the evolution of the electrode potential of the tested samples was monitored. The evolution of diffraction line width, B220, during the testing time was displayed. Both in air and in the corroding medium, B220 varies in jumps. In the corroding medium the inner second order tensions have a smaller level and a greater jump frequency. This shows that the tested samples have a lower durability in corroding medium than in the air. The variation of the inner second order tension level versus the number of

  5. Piezoelectric Bolt Breakers and Bolt Fatigue Testers

    Science.gov (United States)

    Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Barengoltz, Jack; Heckman, Vanessa

    2008-01-01

    A proposed family of devices for inducing fatigue in bolts in order to break the bolts would incorporate piezoelectric actuators into resonant fixtures as in ultrasonic/ sonic drills/corers and similar devices described in numerous prior NASA Tech Briefs articles. These devices were originally intended primarily for use as safer, more-reliable, more-versatile alternatives to explosive bolts heretofore used to fasten spacecraft structures that must subsequently be separated from each other quickly on command during flight. On Earth, these devices could be used for accelerated fatigue testing of bolts. Fatigue theory suggests that a bolt subjected to both a constant-amplitude dynamic (that is, oscillatory) stress and a static tensile stress below the ultimate strength of the bolt material will fail faster than will a bolt subjected to only the dynamic stress. This suggestion would be applied in a device of the proposed type. The device would be designed so that the device and the bolt to be fatigue-tested or broken would be integral parts of an assembly (see figure). The static tension in the tightened bolt would apply not only the clamping force to hold the joined structures (if any) together but also the compression necessary for proper operation of the piezoelectric actuators as parts of a resonant structural assembly. The constant-amplitude dynamic stress would be applied to the bolt by driving the piezoelectric actuators with a sinusoidal voltage at the resonance frequency of longitudinal vibration of the assembly. The amplitude of the excitation would be made large enough so that the vibration would induce fatigue in the bolt within an acceptably short time. In the spacecraft applications or in similar terrestrial structural-separation applications, devices of the proposed type would offer several advantages over explosive bolts: Unlike explosive bolts, the proposed devices would be reusable, could be tested before final use, and would not be subject to

  6. Improving Fatigue Performance of AHSS Welds

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [ORNL; Yu, Xinghua [ORNL; ERDMAN III, DONALD L [ORNL; Wang, Yanli [ORNL; Kelly, Steve [ArcelorMittal USA; Hou, Wenkao [ArcelorMittal USA; Yan, Benda [ArcelorMittal USA; Wang, Zhifeng [Colorado School of Mines, Golden; Yu, Zhenzhen [Colorado School of Mines, Golden; Liu, Stephen [Colorado School of Mines, Golden

    2015-03-01

    Reported herein is technical progress on a U.S. Department of Energy CRADA project with industry cost-share aimed at developing the technical basis and demonstrate the viability of innovative in-situ weld residual stresses mitigation technology that can substantially improve the weld fatigue performance and durability of auto-body structures. The developed technology would be costeffective and practical in high-volume vehicle production environment. Enhancing weld fatigue performance would address a critical technology gap that impedes the widespread use of advanced high-strength steels (AHSS) and other lightweight materials for auto body structure light-weighting. This means that the automotive industry can take full advantage of the AHSS in strength, durability and crashworthiness without the concern of the relatively weak weld fatigue performance. The project comprises both technological innovations in weld residual stress mitigation and due-diligence residual stress measurement and fatigue performance evaluation. Two approaches were investigated. The first one was the use of low temperature phase transformation (LTPT) weld filler wire, and the second focused on novel thermo-mechanical stress management technique. Both technical approaches have resulted in considerable improvement in fatigue lives of welded joints made of high-strength steels. Synchrotron diffraction measurement confirmed the reduction of high tensile weld residual stresses by the two weld residual stress mitigation techniques.

  7. A description of spinal fatigue strength.

    Science.gov (United States)

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

    2016-04-11

    Understanding fatigue failure of the spine is important to establish dynamic loading limits for occupational health and safety. In this study experimental data were combined with published data to develop a description of the predictive parameters for spinal fatigue failure. 41 lumbar functional spinal units (FSUs) from cadaveric spines (age 49.0±11.9yr) where cyclically loaded. Three different levels of sinusoidal axial compression (0-3kN, 0-2kN or 1-3kN) were applied for 300,000 cycles. Further, published data consisted of 70 thoracic and lumbar FSUs loaded in axial compression for 5000 cycles. Cyclic forces ranged from lower peaks (Fmin) of 0.7-1kN to upper peaks (Fmax) of 1.2-7.1kN. Based on Wöhler analysis, a fatigue model was developed accounting for three parameters: I) specimen-specific scaling based on the endplate area, II) specimen-specific strength dependency on age or bone mineral density, III) load-specific correction factors based on Fmax and Fmin. The most predictive model was achieved for a combination of Fmax, endplate area and bone mineral density; this model explained 61% of variation (pload-specific correction factor did not significantly improve model prediction of fatigue failure. This analysis presents the basis for the prediction of specimen-specific fatigue failure of the lumbar spine, provided the endplate area and bone mineral density can be derived. PMID:26948575

  8. E-readers and visual fatigue.

    Directory of Open Access Journals (Sweden)

    Simone Benedetto

    Full Text Available The mass digitization of books is changing the way information is created, disseminated and displayed. Electronic book readers (e-readers generally refer to two main display technologies: the electronic ink (E-ink and the liquid crystal display (LCD. Both technologies have advantages and disadvantages, but the question whether one or the other triggers less visual fatigue is still open. The aim of the present research was to study the effects of the display technology on visual fatigue. To this end, participants performed a longitudinal study in which two last generation e-readers (LCD, E-ink and paper book were tested in three different prolonged reading sessions separated by--on average--ten days. Results from both objective (Blinks per second and subjective (Visual Fatigue Scale measures suggested that reading on the LCD (Kindle Fire HD triggers higher visual fatigue with respect to both the E-ink (Kindle Paperwhite and the paper book. The absence of differences between E-ink and paper suggests that, concerning visual fatigue, the E-ink is indeed very similar to the paper.

  9. Effects of fatigue on golf performance.

    Science.gov (United States)

    Higdon, Nicholas R; Finch, W Holmes; Leib, Daniel; Dugan, Eric L

    2012-06-01

    The purpose of this study was to determine if body position, weight transfer, and/or pelvis/trunk rotations changed as a result of a golf specific fatiguing protocol and whether these changes affected resultant club head velocity at impact and shot consistency. Six male golfers and one female golfer participated in the study, who had a mean age, height, and body mass of 23.9 +/- 3.9 years, 177.4 +/- 4.9 cm, and 75.3 +/- 9.9 kg, respectively. Path analysis was used to determine the relationships between fatigue, biomechanical variables, and resultant club head velocity at impact and shot consistency. In the statistical models representing the effects of biomechanical variables calculated at the top of the swing and ball contact, golf specific fatigue was associated with a 2.0% and 2.5% reduction in the club head velocity and a 7.1% and 9.4% improvement in the shot consistency, respectively. These data suggest that golf specific fatigue was not related to the initial lower body sagittal plane angles at address nor was simulated golf specific fatigue related to peak transverse plane pelvis and trunk rotational velocities (or their timings) in a manner that indicates a relationship to resultant club head velocity and shot consistency. PMID:22900400

  10. Strength gradient enhances fatigue resistance of steels

    Science.gov (United States)

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-02-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility.

  11. A fatigue monitoring system in the nuclear power station. A fatigue evaluation on a pressure vessel of the Tsuruga No. 1 reactor using an automatic fatigue calculating system

    International Nuclear Information System (INIS)

    For the Tsuruga Power Station No. 1 reactor, in order not only to evaluate a maintaining fatigue, but also to confirm at an actual reactor how actually forming fatigue is accumulated, and to what grade it was accumulated against its designed value, a fatigue monitoring system was mounted onto the reactor pressure vessel about ten years ago. This fatigue monitor can automatically and in real time collect its operation parameters to carry out automatically its fatigue calculation and also store these data. Then, by data output from this monitor, maintenance against fatigue evaluation of the design base can be proved and its long-term fatigue soundness can be forecast. And, recently, so-called 'environmental fatigue' where coolant environment in the reactor primary system reduces fatigue strength, has become a problem on discussion, and from this viewpoint, the monitor is thought to be an effective means to prove soundness of reactor. Here were introduced the fatigue monitor in the Tsuruga Power Station No. 1 reactor and its application results, evaluation of recorded fatigue coefficients, and so forth. (G.K.)

  12. 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.

  13. Astragalus membranaceus Improves Exercise Performance and Ameliorates Exercise-Induced Fatigue in Trained Mice

    Directory of Open Access Journals (Sweden)

    Tzu-Shao Yeh

    2014-03-01

    Full Text Available Astragalus membranaceus (AM is a popular “Qi-tonifying” herb with a long history of use as a Traditional Chinese Medicine with multiple biological functions. However, evidence for the effects of AM on exercise performance and physical fatigue is limited. We evaluated the potential beneficial effects of AM on ergogenic and anti-fatigue functions following physiological challenge. Male ICR strain mice were randomly assigned to four groups (n = 10 per group for treatment: (1 sedentary control and vehicle treatment (vehicle control; (2 exercise training with vehicle treatment (exercise control; and (3 exercise training with AM treatment at 0.615 g/kg/day (Ex-AM1 or (4 3.075 g/kg/day (Ex-AM5. Both the vehicle and AM were orally administered for 6 weeks. Exercise performance and anti-fatigue function were evaluated by forelimb grip strength, exhaustive swimming time, and levels of serum lactate, ammonia, glucose, and creatine kinase after 15-min swimming exercise. Exercise training combined with AM supplementation increased endurance exercise capacity and increased hepatic and muscle glycogen content. AM reduced exercise-induced accumulation of the byproducts blood lactate and ammonia with acute exercise challenge. Moreover, we found no deleterious effects from AM treatment. Therefore, AM supplementation improved exercise performance and had anti-fatigue effects in mice. It may be an effective ergogenic aid in exercise training.

  14. Creep and fatigue crack growth at high temperatures

    Czech Academy of Sciences Publication Activity Database

    Radon, J.; Knésl, Zdeněk

    2002-01-01

    Roč. 9, č. 2 (2002), s. 1-8. ISSN 1335-0803 Institutional research plan: CEZ:AV0Z2041904 Keywords : Creep * fatigue crack growth * high temperatures Subject RIV: JL - Materials Fatigue, Friction Mechanics

  15. Number of teeth and fatigue in older adults

    DEFF Research Database (Denmark)

    Avlund, Kirsten; Schultz-Larsen, Kirsten; Christiansen, Niels;

    2011-01-01

    To examine whether tooth loss at age 70 is associated with fatigue in a nondisabled community-dwelling population cross-sectionally at age 70 and with onset of fatigue longitudinally at 5-, 10-, and 15-year follow-ups....

  16. Chronic Fatigue Syndrome (CFS): Managing Activities and Exercise

    Science.gov (United States)

    ... message, please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Managing Activities and Exercise ... activities. Top of Page Related Links Disability and Chronic Fatigue Syndrome Print page View page in: Español (Spanish) ...

  17. Creep and fatigue crack growth at elevated temperatures

    Czech Academy of Sciences Publication Activity Database

    Czoboly, E.; Knésl, Zdeněk; Radon, J.

    2002-01-01

    Roč. 12, č. 4 (2002), s. 103-110. ISSN 1215-8410 Institutional research plan: CEZ:AV0Z2041904 Keywords : elevated temperatures * fatigue crack * creep Subject RIV: JL - Materials Fatigue, Friction Mechanics

  18. Towards a unified fatigue life prediction method for marine structures

    CERN Document Server

    Cui, Weicheng; Wang, Fang

    2014-01-01

    In order to apply the damage tolerance design philosophy to design marine structures, accurate prediction of fatigue crack growth under service conditions is required. Now, more and more people have realized that only a fatigue life prediction method based on fatigue crack propagation (FCP) theory has the potential to explain various fatigue phenomena observed. In this book, the issues leading towards the development of a unified fatigue life prediction (UFLP) method based on FCP theory are addressed. Based on the philosophy of the UFLP method, the current inconsistency between fatigue design and inspection of marine structures could be resolved. This book presents the state-of-the-art and recent advances, including those by the authors, in fatigue studies. It is designed to lead the future directions and to provide a useful tool in many practical applications. It is intended to address to engineers, naval architects, research staff, professionals and graduates engaged in fatigue prevention design and survey ...

  19. Macroscopic cumulative fatigue damage of material under nonsymmetrical cycle

    Institute of Scientific and Technical Information of China (English)

    盖秉政

    2002-01-01

    Hashin's macroscopic theory of fatigue damage is further discussed and a new method has been proposed for prediction of cumulative fatigue damage of material and its lifetime under nonsymmetrical cyclic loading.

  20. Corrosion fatigue of high strength fastener materials in seawater

    Science.gov (United States)

    Tipton, D. G.

    1983-01-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  1. Fatigue Reliability and Calibration of Fatigue Design Factors for Offshore Wind Turbines

    Directory of Open Access Journals (Sweden)

    Sergio Márquez-Domínguez

    2012-06-01

    Full Text Available Consequences of failure of offshore wind turbines (OWTs is in general lower than consequences of failure of, e.g., oil & gas platforms. It is reasonable that lower fatigue design factors can be applied for fatigue design of OWTs when compared to other fixed offshore structures. Calibration of appropriate partial safety factors/Fatigue Design Factors (FDF for steel substructures for OWTs is the scope of this paper. A reliability-based approach is used and a probabilistic model has been developed, where design and limit state equations are established for fatigue failure. The strength and load uncertainties are described by stochastic variables. SN and fracture mechanics approaches are considered for to model the fatigue life. Further, both linear and bi-linear SN-curves are formulated and various approximations are investigated. The acceptable reliability level for fatigue failure of OWTs is discussed and results are presented for calibrated optimal fatigue design factors. Further, the influence of inspections is considered in order to extend and maintain a given target safety level.

  2. Crohn's disease, fatigue, and infliximab: Is there a role for cytokines in the pathogenesis of fatigue?

    Institute of Scientific and Technical Information of China (English)

    Itta M Minderhoud; Melvin Samsom; Bas Oldenburg

    2007-01-01

    AIM: To study the effect of infliximab on fatigue in relation to cytokine levels in Crohn's disease (CD) patients.METHODS: Fourteen CD patients were blinded for treatment and received placebo at baseline, and infliximab 2 wk later, with a follow-up of 4 wk. Blood samples were drawn on a regular basis, and questionnaires on fatigue,depression, quality of life, and clinical disease activity were completed at regular intervals.RESULTS: After placebo infusion, fatigue scores decreased within 3 d (3.5 points + 1.1, P ≤ 0.01), but returned to baseline values 14 d after this infusion.The drop of fatigue scores following infliximab infusion sustained until the end of the study (3.8 points ± 1.4, P ≤ 0.05). Quality of life was increased at the end of the study compared to baseline values (138.6 ± 9.4 vs179.4+ 6.7; P ≤ 0.005), whereas depression scores were decreased (20.4 ± 9.4 vs11.3 + 2.2; P ≤ 0.01). No correlation between the severity of fatigue and the level of cytokines was observed.CONCLUSION: The reduction of fatigue after infliximab infusion is subjective to a placebo effect. The effect of infliximab on fatigue, however, persists while the placebo effect disappears after a short period of time. A clear role of cytokines could not be substantiated.

  3. Adaptations to isolated shoulder fatigue during simulated repetitive work. Part I: Fatigue.

    Science.gov (United States)

    Tse, Calvin T F; McDonald, Alison C; Keir, Peter J

    2016-08-01

    Upper extremity muscle fatigue is challenging to identify during industrial tasks and places changing demands on the shoulder complex that are not fully understood. The purpose of this investigation was to examine adaptation strategies in response to isolated anterior deltoid muscle fatigue while performing simulated repetitive work. Participants completed two blocks of simulated repetitive work separated by an anterior deltoid fatigue protocol; the first block had 20 work cycles and the post-fatigue block had 60 cycles. Each work cycle was 60s in duration and included 4 tasks: handle pull, cap rotation, drill press and handle push. Surface EMG of 14 muscles and upper body kinematics were recorded. Immediately following fatigue, glenohumeral flexion strength was reduced, rating of perceived exertion scores increased and signs of muscle fatigue (increased EMG amplitude, decreased EMG frequency) were present in anterior and posterior deltoids, latissimus dorsi and serratus anterior. Along with other kinematic and muscle activity changes, scapular reorientation occurred in all of the simulated tasks and generally served to increase the width of the subacromial space. These findings suggest that immediately following fatigue people adapt by repositioning joints to maintain task performance and may also prioritize maintaining subacromial space width. PMID:26208429

  4. Fatigue-Prone Details in Steel Bridges

    Directory of Open Access Journals (Sweden)

    Mohsen Heshmati

    2012-11-01

    Full Text Available This paper reviews the results of a comprehensive investigation including more than 100 fatigue damage cases, reported for steel and composite bridges. The damage cases are categorized according to types of detail. The mechanisms behind fatigue damage in each category are identified and studied. It was found that more than 90% of all reported damage cases are of deformation-induced type and generated by some kind of unintentional or otherwise overlooked interaction between different load-carrying members or systems in the bridge. Poor detailing, with unstiffened gaps and abrupt changes in stiffness at the connections between different members were also found to contribute to fatigue cracking in many details.

  5. Ultrasonic fatigue testing device under biaxial bending

    Directory of Open Access Journals (Sweden)

    C. Brugger

    2016-07-01

    Full Text Available A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. A flat smooth specimen with a disc geometry is placed on a torus frame and cyclically loaded at the center of its upper face. Disc bending generates a biaxial proportional stress state at the center of the lower face. Any positive loading ratio can be applied. A cast aluminum alloy (used to produce cylinder heads has been tested under biaxial bending using this device in order to determine its fatigue strength at 109 cycles under high hydrostatic pressure. Self-heating is moderate but macroscopic fatigue cracks after testing are very long. First results in VHCF regime are consistent with literature results obtained under similar stress state but in HCF regime and at 20 Hz.

  6. Fatigue-ratcheting analysis of pressurized elbows

    International Nuclear Information System (INIS)

    Three dynamic tests on pressurized elbows involving fatigue-ratcheting as the major failure mode are investigated. The fatigue analysis is carried out with two approaches: the first is global and consists of Markl's equation; the second is local and is based on local fatigue criteria combined with a suggestion by Coffin to take into account ratcheting. The implementation of these approaches required some elementary signal processing to separate the cyclic part of the strain from ratcheting, results on narrow-band processes to assess cumulative damage, finite element computations to derive necessary data in not instrumented locations, and some heuristic assumptions. The great sensitivity of the implemented criteria to their arguments is discussed and exemplified. Even though the issue is full of complexities, computed results match well with those of the tests

  7. Mechanisms of exertional fatigue in muscle glycogenoses

    DEFF Research Database (Denmark)

    Vissing, John; Haller, Ronald G

    2012-01-01

    relates directly to the metabolic defect, but also to substrate-limited energy deficiency, as exemplified by the "second wind" phenomenon in McArdle disease. A number of secondary events may also play a role in inducing premature fatigue in glycogenoses, including (1) absent or blunted muscle acidosis...... concentrations of extracellular potassium in exercising muscle and (3) exaggerated accumulation of ADP during exercise that may inhibit sodium-potassium and calcium-ATPases. Disorders of muscle glycogenolysis and glycolysis reveal the crucial role of these metabolic processes for supplying both anaerobic and...... aerobic energy for muscle contraction; and the pathological fatigue that occurs when glycogenolysis and/or glycolysis is blocked imply an important role for theses metabolic pathways in normal muscle fatigue....

  8. Low cycle fatigue problem in RAPP fuel

    International Nuclear Information System (INIS)

    In a nuclear power plant, the fuel sheath is subjected to power cycling during start-up and shut-down, and also during normal operation. Power reactors operating in relatively small electrical grids, as for example RAPS-1 are prone to large number of such power cycles. RAPS fuel sheath being of the collapsible design is subjected to high initial plastic strains. These environmental conditions pose serious low cycle fatigue problem in RAPS fuel operations. The limitations on fuel life due to low cycle fatigue are described. The low cycle fatigue behaviour of zircaloy under normal and irradiation is discussed. UO2 expansion model used for calculating plastic strains is also described. (author)

  9. Nondestructive detection of microstructural fatigue damage

    International Nuclear Information System (INIS)

    Ultrasonic as well as magnetic investigations have been performed on a pressure vessel steel (A533, B class 1) in order to study the influence of fatigue loading on both elastic and magnetic material properties. Using laboratory specimens under two different loading conditions (tension-tension loading, tension-compression loading), material characteristics like ultrasonic velocity, ultrasonic absorption, coercivity, incremental permeability were measured and evaluated as a function of consumed lifetime. Only in case of macroscopic plastic deformation, significant changes of the measuring quantities were observed. Otherwise the effects are so small that the nondestructive detection of microstructural changes due to fatigue loading seems not to be feasible under practical conditions (for example at pressure vessels) with the techniques used. Besides a zero measurement, additional measurements on a 1:5 model vessel at JRC Ispra could not be carried out, because the planned fatigue tests were not performed by JRC Ispra during the research period

  10. Creep fatigue design of FBR components

    International Nuclear Information System (INIS)

    This paper deals with the characteristic features of Fast Breeder Reactor (FBR) with reference to creep fatigue, current creep fatigue design approach in compliance with RCCMR (1987) design code, material data, effects of weldments and neutron irradiation, material constitutive models employed, structural analysis and further R and D required for achieving maturity in creep fatigue design of FBR components. For the analysis reported in this paper, material constitutive models developed based on ORNIb (Oak Ridge National Laboratory) and Chaboche viscoplastic theories are employed to demonstrate the potential of FBR components for higher plant temperatures and/or longer life. The results are presented for the studies carried out towards life prediction of Prototype Fast Breeder Reactor (PFBR) components. (author). 24 refs, 8 figs, 5 tabs

  11. Jacket Substructure Fatigue Mitigation through Active Control

    DEFF Research Database (Denmark)

    Hanis, Tomas; Natarajan, Anand

    As offshore wind farms are being installed farther and in deeper waters offshore, new, and more sophisticated marine substructures such as jackets need to be used. Herein, a 10MW wind turbine mounted on a jacket sub structure at a mean water depth of 50 meters is investigated with regards to the...... fatigue design loads on the braces of the jacket. Since large wind turbines of 10MW rating have low rotor speeds (p), the modal frequencies of the sub structures approach 3p at low wind speeds, which leads to a modal coupling and resonance. Therefore an active control system is developed which provides...... sufficient structural damping and consequently a fatigue reduction at the substructure. The resulting reduction in fatigue design loads on the jacket structure based on the active control system is presented....

  12. Fatigue strength on superalloy Inconel 600

    International Nuclear Information System (INIS)

    In this paper, the strain controlled fatigue test at room temperature in air and the fractographic study on superalloy Inconel 600 are performed. From the test results, the relations between nominal stresses and number of cycles are obtained to show that the stress increases slightly in the early period, then remains stable at constant value for a subsequent long period, and then steeply drops immediately before the final failure. The relationships on strain amplitude with fatigue life are introduced. The values of fictitious stress amplitude calculated from the test results are just lying between the two best fit curves from ASME, Sec. III, Division I, Appendix Table 1.9.1/2 in 1983 and Transaction of ASME, Nov. 1977, p. 584. From the microscopic examination of the fatigue fracture, there are three failure process zones: fatiguecrack origin appearance zone, stable radial spread zone, and final fast fracture zone. (author)

  13. Fatigue in adults with traumatic brain injury

    DEFF Research Database (Denmark)

    Mollayeva, Tatyana; Kendzerska, Tetyana; Mollayeva, Shirin;

    2013-01-01

    BACKGROUND: Despite strong indications that fatigue is the most common and debilitating symptom after traumatic brain injury, little is known about its frequency, natural history, or relation to other factors. The current protocol outlines a strategy for a systematic review that will identify......, assess, and critically appraise studies that assessed predictors for fatigue and the consequences of fatigue on at least two separate time points following traumatic brain injury. METHODS/DESIGN: MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, CINAHL, and PsycINFO will be systematically...... quality appraisal. Randomized control trial data will be treated as a cohort. The quality will be assessed using the criteria defined by Hayden and colleagues. The review will be conducted and reported in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines...

  14. In situ fatigue-crack-propagation experiment

    International Nuclear Information System (INIS)

    An in-reactor fatigue experiment was conducted in the Oak Ridge Research Reactor to determine the effects of dynamic irradiation on fatigue crack propagation. Eight 20% cold-worked 316 stainless steel specimens were precracked to various initial crack lengths, linked together to form a chain, and inserted into a specially designed in-reactor fatigue machine. Test conditions included a maximum temperature of 4600C, an environment of sodium, a frequency of 1 cycle/min, and a stress ratio of 0.10. Results indicated that (1) no effects of dynamic irradiation were observed for a fluence of 1.5 x 1021 n/cm2 (E > 0.1 MeV); and (2) crack growth rates in elevated temperature sodium were a factor of 3 to 4 lower than in room temperature air

  15. Pharmacological treatments for fatigue associated with palliative care

    OpenAIRE

    Mücke, M.; Mochamat; Cuhls, H; Peuckmann-Post, V.; Minton, O.; Stone, P.; Radbruch, L.

    2015-01-01

    BACKGROUND: This review updates the original review, 'Pharmacological treatments for fatigue associated with palliative care' and also incorporates the review 'Drug therapy for the management of cancer-related fatigue'.In healthy individuals, fatigue is a protective response to physical or mental stress, often relieved by rest. By contrast, in palliative care patients' fatigue can be severely debilitating and is often not counteracted with rest, thereby impacting daily activity and quality of...

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

    OpenAIRE

    Carlos Carvalho Engler-Pinto Júnior; Dirceu Spinelli

    2014-01-01

    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 ...

  17. Is there a future for material fatigue research?

    Energy Technology Data Exchange (ETDEWEB)

    Joosse, P. [Stork Product Engineering b.v., Amsterdam (Netherlands); Bulder, B. [ECN-Renewable Energy, Petten (Netherlands)

    1996-09-01

    Due to the fact that it is quite difficult to get new funding for (fundamental) wind turbine material related fatigue research the authors started a discussion with the following title: Are there still wind turbine engineering specific fatigue problems? and What are the research goals for the fatigue experts in wind engineering for the second half of the 90{sup ies}. In this paper the present status of the fatigue issue and the discussion following is reported. (au)

  18. Fatigue damage modeling of composite structures: the onera viewpoint

    OpenAIRE

    Kaminski, M.; Laurin, F.; Maire, J.F.; Rakotoarisoa, C.; Hémon, E.

    2015-01-01

    International audience The aim of this paper is to present the fatigue damage modeling approach developed at ONERA for the fatigue life prediction of composite materials and structures. This paper is divided into five sections. The first one explains why the already developed and validated methods for fatigue life modeling of metals and alloys cannot be directly applied to composite materials. Thus, the proposal of an efficient fatigue model for composite materials necessitates a good unde...

  19. Fatigue in Aluminum Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2014-01-01

    Fatigue damage accumulation in aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test...... normally used in the design against fatigue in aluminum bridges, may give results which are unconservative. The validity of the results obtained from Miner’s rule will depend on the distribution of the load history in tension and compression....

  20. Efficacy of Neurotropin in Chronic Fatigue Syndrome : a Case Report

    OpenAIRE

    Toda, Katsuhiro; Kimura, Hiroaki

    2006-01-01

    Chronic fatigue syndrome (CFS) is a disorder that causes general fatigue and chronic widespread pain. A 28-year-old male visited an outpatient department due to general fatigue and pain involving the entire body. He did not suffer from fibromyalgia, but he was diagnosed with CFS. At the initial visit, he complained of lack of concentration, memory decline, frequent urination, insomnia and occasional difficulty of emotional control, as well as general fatigue and pain involving the entire body...

  1. Study of Driving Fatigue Alleviation by Transcutaneous Acupoints Electrical Stimulations

    OpenAIRE

    Fuwang Wang; Hong Wang

    2014-01-01

    Driving fatigue is more likely to bring serious safety trouble to traffic. Therefore, accurately and rapidly detecting driving fatigue state and alleviating fatigue are particularly important. In the present work, the electrical stimulation method stimulating the Láogóng point (劳宫PC8) of human body is proposed, which is used to alleviate the mental fatigue of drivers. The wavelet packet decomposition (WPD) is used to extract θ, α, and β subbands of drivers' electroencephalogram (EEG) signals....

  2. Very high cycle fatigue of high performance steels

    OpenAIRE

    Kazymyrovych, Vitaliy

    2008-01-01

    Many engineering components reach a finite fatigue life well above 109 load cycles. Some examples of such components are found in airplanes, automobiles or high speed trains. For some materials the fatigue failures have lately been found to occur well after 107 load cycles, namely in the Very High Cycle Fatigue (VHCF) range. This finding contradicted the established concept of fatigue limit for these materials, which postulates that having sustained 107 load cycles the material is capable of ...

  3. Motor fatigue and cognitive task performance in humans

    OpenAIRE

    Lorist, M.M.; Kernell, Daniel; Meijman, T F; Zijdewind, Inge

    2002-01-01

    During fatiguing submaximal contractions a constant force production can be obtained at the cost of an increasing central command intensity. Little is known about the interaction between the underlying central mechanisms driving motor behaviour and cognitive functions. To address this issue, subjects performed four tasks: an auditory choice reaction task (CRT), a CRT simultaneously with a fatiguing or a non-fatiguing submaximal muscle contraction task, and a fatiguing submaximal contraction t...

  4. Partial Safety Factors for Fatigue Design of Wind Turbine Blades

    OpenAIRE

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2010-01-01

    In the present paper calibration of partial safety factors for fatigue design of windturbine blades is considered. The stochastic models for the physical uncertaintieson the material properties are based on constant amplitude fatigue tests and theuncertainty on Miners rule for linear damage accumulation is determined fromvariable amplitude fatigue tests with the Wisper and Wisperx spectra. Thestatistical uncertainty for the assessment of the fatigue loads is also investigated.The partial safe...

  5. Flexural Fatigue Behavior of Layered Hybrid Fiber Reinforced Concrete

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to obtain the fatigue life of layered hybrid fiber reinforced concrete (LHFRC) at different stress levels, fiexural fatigue tests were carried out on specimens. The relation between fatigue lives and stress levels was simulated using the two-parameter Weibull distribution. Furthermore, both single-logarithmic and double-logarithmic regressive equations of various reliabilities were derived. It is evident that LHFRC gets the advantage of longer fatigue life over common concrete.

  6. The effect of exercise therapy on fatigue in multiple sclerosis

    DEFF Research Database (Denmark)

    Andreasen, A; Stenager, E; Dalgas, U

    2011-01-01

    Fatigue occurs in the majority of patients with multiple sclerosis (MS) and therapeutic possibilities are few. Exercise therapy is a therapeutic option but no studies have systematically reviewed the existing literature evaluating the effect of exercise therapy on MS fatigue.......Fatigue occurs in the majority of patients with multiple sclerosis (MS) and therapeutic possibilities are few. Exercise therapy is a therapeutic option but no studies have systematically reviewed the existing literature evaluating the effect of exercise therapy on MS fatigue....

  7. Fatigue Crack Initiation and Propagation of Aluminum Alloy Bearings

    Institute of Scientific and Technical Information of China (English)

    CHENG Xian-Hua; MA Yan-Yan

    2004-01-01

    Observation of fatigue crack initiation and propagation during fatigue test in ALSn20Cu bearing has been presented. Journal center orbit, oil film pressure and stress distribution in alloy layer have been calculated and are taken as the basis for theoretically simulating the bearing fatigue process. It is found that the calculated results are in good accordance with the experimental results, which provides a feasible way for investigation of fatigue crack propagation process in the bearing.

  8. Thermal fatigue crack growth in stainless steel

    International Nuclear Information System (INIS)

    A judgment of residual service life of engineering parts exposed to thermal fatigue makes it possible to deal with economic and safety issues in power plants. The aim of this study is to analyze a fatigue crack initiation and propagation in A321 stainless steel bodies subjected to repeated thermal shocks. For this purpose, various methods of crack propagation monitoring were used. The first stage of experiments included mechanical cyclic loading of specimens with the central notch at fixed temperatures ranging from 20 °C to 410 °C. The crack growth rate was only minimally influenced by temperature in this case. Thermal loading of the same specimens with ΔT varying from 150 °C to 340 °C showed very rapid crack initiation in the notches and its asymmetric growth. Metallographic and fractographic analyses of failed specimens were carried out after 1000, 3000 and 6000 thermal cycles. The comparison of the fracture surface micromorphology confirmed the similarity in the mechanism of the thermal and mechanical fatigue crack growth. Stress analysis using the finite element method consisting of transient thermal and mechanical solutions was performed in order to simulate the experiments. Thermal fatigue crack growth assessment was carried out on the basis of the experiments and the computed thermally induced stress intensity factors. This model successfully confirms the discussed analogy of thermal and mechanical stress induced damage. Highlights: ► A fatigue crack initiation and propagation in A321 stainless steel was analyzed. ► Mechanical and thermal experiments were performed, simulated also by FEM. ► Similarity in the mechanism of thermal and mechanical fatigue crack growth found. ► Application of the Paris model for the thermal cycling confirmed.

  9. Operator fatigue detection and countermeasure development

    Energy Technology Data Exchange (ETDEWEB)

    Daniel Bongers [CRC Mining (Australia)

    2009-05-15

    A prototype technology for measuring and reporting an individual's fatigue, with the intention that such a technology could be used to prevent fatigue-related injuries in the Australian coal mining industry is known as the Smart Cap system. It resembles a typical baseball cap yet contains sophisticated sensors capable of measuring EEG (brain waves) through hair, determining an individual's fatigue level and reporting that to an in-cab display. The first phase of developmentwas to develop the sensor capable of reading EEG without the need for conductive gel. Once this was proven, a more sophisticated circuit was developed that incorporated tuned filtering and digital signal processing allowing the brain wave data to be stored and communicated using Bluetooth wireless. The third and final phase was focussed on the embodiment of the sensor array into a baseball cap in order to allow long term use in a mining environment. Two field trials of the Smart Cap fatigue detection system took place at surface coal mining operations in central Queensland during 2008. 53 operators were involved in these trials for one or more shifts. Both day and night shifts were incorporated for operators of haul trucks, excavators, water trucks, dozers and graders. Infrared video footage of some operators was captured for comparison with the real-time EEG and fatigue information collected by the Smart Cap system. This footage allowed the calculation of the percentage of eye closure (PERCLOS) of eleven operators. Comparison of the PERCLOS measurements with operator fatigue levels shows good correlation in line with similar published research. The Smart Cap system performed according to its design parameters. We show that the sophisticated sensor array is capable of eliminating ambient electrical noise in the mine environment, and that the Bluetooth connectivity is secure in the event of intentional mismatching of equipment or close vehicle interactions.

  10. Study Fatigue in Materials of Drill Pipes

    Directory of Open Access Journals (Sweden)

    J. Argirov

    2016-02-01

    Full Text Available Upon examination of a fracture burst, it was found out that the main reason for this is the fatigue of the material in the annular section of the pipes. Analysis was made of the stress state and its impact on the nature of the destruction. In a working conditions, especially in rotor drilling, a direct correlation between the loss of stability of the column in the compression zone and the destruction of drill piping due to fatigue failures in material is established. Object of study is the nature of the destruction of defective drill pipe

  11. Fatigue Properties of the Two Composite Geotextiles

    Institute of Scientific and Technical Information of China (English)

    QIAN Cheng; CHU Cai-yuan

    2002-01-01

    In order to make clear the service life of the two composite geotextiles, their fatigue and dynamic creep properties were tested and compared. The experimental results show that the dynamic creep deformations of adhesive bonded composite geotextiles are lower than those of needle -punched composite geotextiles and the former also have longer fatigue lifetime than the latter.As during the making process, the component parts of adhesive bonded composite geotextiles are not damaged by any factors which in case make their tensile strength higher than those of the needle- punched composite geotextiles. At the end of the paper, a proper explanation was given to this phenomenon.

  12. Asphalt rubber mixtures in Portugal: fatigue resistance

    OpenAIRE

    Miranda, Henrique; Batista, Fátima; Neves, José; Antunes, Maria de Lurdes; Fonseca, Paulo

    2009-01-01

    This paper presents a study concerning the fatigue behaviour of asphalt mixtures with bitumen modified with high content of crumb rubber used in Portugal. For assessing the fatigue behaviour of this type of mixtures, four asphalt mixtures with high content of crumb rubber were used: two field bituminous mixtures – an open-graded and a gap-graded – both with granite aggregates; and two laboratory manufactured bituminous mixtures – an open-graded mixture with granite aggregates and a gap-graded...

  13. Work fatigue in urban bus drivers

    OpenAIRE

    Teresa Makowiec-Dąbrowska; Jadwiga Siedlecka; Elżbieta Gadzicka; Agata Szyjkowska; Marta Dania; Piotr Viebig; Marcin Kosobudzki; Alicja Bortkiewicz

    2015-01-01

    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...

  14. Failure and fatigue mechanisms in composite materials

    Science.gov (United States)

    Rosen, B. W.; Kulkarni, S. V.; Mclaughlin, P. V., Jr.

    1975-01-01

    A phenomenological description of microfailure under monotonic and cyclic loading is presented, emphasizing the significance of material inhomogeneity for the analysis. Failure in unnotched unidirectional laminates is reviewed for the cases of tension, compression, shear, transverse normal, and combined loads. The failure of notched composite laminates is then studied, with particular attention paid to the effect of material heterogeneity on load concentration factors in circular holes in such laminates, and a 'materials engineering' shear-lay type model is presented. The fatigue of notched composites is discussed with the application of 'mechanistic wearout' model for determining crack propagation as a function of the number of fatigue cycles.-

  15. The monotonic and fatigue behavior of CFCCs

    Energy Technology Data Exchange (ETDEWEB)

    Miriyala, N.; Liaw, P.K.; McHargue, C.J. [Univ. of Tennessee, Knoxville, TN (United States); Snead, L.L. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Flexure tests were performed to study the fabric orientation effects on the monotonic and fatigue behavior of two commercially available continuous fiber reinforced ceramic composites (CFCCs), namely (i) Nicalon fiber fabric reinforced alumina (Al{sub 2}O{sub 3}) matrix composite fabricated by a direct molten metal oxidation (DIMOX) process and, (ii) Nicalon fiber fabric reinforced silicon carbide (SiC) matrix composite fabricated by an isothermal chemical vapor infiltration (ICVI) process. The fabric orientation effects on the monotonic and fatigue behavior were strong in the Nicalon/Al{sub 2}O{sub 3} composite, while they were relatively weak in the Nicalon/SiC composite.

  16. Compassion Fatigue: Strategies for Minimizing Impact on Aesthetic Medical Providers.

    Science.gov (United States)

    Brennan, Connie

    2015-01-01

    Compassion fatigue is emotional, physical, and spiritual exhaustion from witnessing and absorbing the problems of others. Aesthetic providers are prone to becoming victims of compassion fatigue because of the stress of meeting the often overwhelming needs of patients. This article discusses what is known about compassion fatigue, what differentiates it from burnout, and how to recognize and combat it. PMID:26605823

  17. Chronic Fatigue Syndrome in Adolescents: treatment, clinical features and epidemiology

    NARCIS (Netherlands)

    Nijhof, S.L.

    2013-01-01

    This thesis describes the treatment, epidemiology and clinical features of the adolescent chronic fatigue syndrome (CFS). Fatigue is a common complaint among adolescents, with a reported incidence of up to 20% in girls. This fatigue however is not chronic, does not debilitate and has an identifiable

  18. Work schedules and fatigue: a prospective cohort study

    OpenAIRE

    Jansen, N; van Amelsvoort, L G P M; Kristensen, T; van den Brandt, P.A.; Kant, I.

    2003-01-01

    Aims: (1) To describe the prevalence of fatigue among employees in different work schedules (day work, three-shift, five-shift, and irregular shift work); (2) to investigate whether different work schedules are related to increasing fatigue over time, while taking into account job title and job characteristics; and (3) to study fatigue among shift workers changing to day work.

  19. Fatigue in cholestatic liver disease—a perplexing symptom

    OpenAIRE

    Kumar, D.; Tandon, R.

    2002-01-01

    Fatigue is an important symptom and a quality of life determinant in patients with cholestatic liver disease. The pathogenesis of fatigue is obscure, although alterations in central neurotransmission and peripheral muscle dysfunction have been incriminated. No effective treatment is available at present. The available literature on fatigue in cholestatic liver disease is reviewed.

  20. Fatigue in fibromyalgia: a conceptual model informed by patient interviews

    DEFF Research Database (Denmark)

    Humphrey, Louise; Arbuckle, Rob; Mease, Philip;

    2010-01-01

    Fatigue is increasingly recognized as an important symptom in fibromyalgia (FM). Unknown however is how fatigue is experienced by individuals in the context of FM. We conducted qualitative research in order to better understand aspects of fatigue that might be unique to FM as well as the impact it...

  1. Fatigue in fibromyalgia: a conceptual model informed by patient interviews

    DEFF Research Database (Denmark)

    Humphrey, Louise; Arbuckle, Rob; Mease, Philip; Williams, David A; Danneskiold-Samsøe, Bente; Gilbert, Claire

    2010-01-01

    Fatigue is increasingly recognized as an important symptom in fibromyalgia (FM). Unknown however is how fatigue is experienced by individuals in the context of FM. We conducted qualitative research in order to better understand aspects of fatigue that might be unique to FM as well as the impact i...

  2. Conceptual design of a fretting fatigue testing device

    OpenAIRE

    Borms, Nick; De Schamphelaere, Davy; De Pauw, Jan; DE BAETS, PATRICK; De Waele, Wim

    2011-01-01

    Fretting fatigue occurs in contacting parts which are simultaneously subjected to fluctuating loads and very small sliding movements. This phenomenon can significantly reduce the fatigue life of components. This paper focuses on the conceptual design of an advanced, especially in functionality and human engineering, test rig for fretting fatigue experiments. Different designs of test rigs are evaluated by weighing their advantages and disadvantages.

  3. Fatigue and phase transition in an oscillating plate

    International Nuclear Information System (INIS)

    We propose a temperature-dependent model for fatigue accumulation in an oscillating elasto-plastic plate accounting also for phase transition. The main modeling hypothesis is that the fatigue rate is proportional to the dissipation rate. We show thermodynamic consistency of the model and discuss a possible choice of the evolution equation for the fatigue parameter m

  4. Nursing on empty: compassion fatigue signs, symptoms, and system interventions.

    Science.gov (United States)

    Harris, Chelsia; Griffin, Mary T Quinn

    2015-01-01

    Few healthcare organizations acknowledge, discuss, or provide interventions for assisting with compassion fatigue. Yet, it is an important concept due to its individual, professional, and financial costs. This article defines compassion fatigue, differentiates it from burnout, and offers system interventions for supporting nurses and reducing compassion fatigue. PMID:25898441

  5. Automatic fatigue monitoring based on real loads. Live demonstration

    International Nuclear Information System (INIS)

    The fatigue assessment of power plant components based on local fatigue monitoring approaches is an essential part of the integrity concept and modern lifetime management. An integral approach like the AREVA Fatigue Concept (AFC) basically consists of two essential modules: realistic determination of occurring operational thermal loads by means of a high end fatigue monitoring system and related highly qualified fatigue assessment methods and tools. The fatigue monitoring system delivers continuously realistic load data at the fatigue relevant locations. Consequently, realistic operational load sequences are available as input data for all ensuing fatigue analyses. This way, realistic load data are available and qualified fatigue usage factors can be determined. The mode of operation of the fatigue monitoring system will be explained in the framework of a live demonstration by means of the FAMOSi (i = integrated) demonstration wall. The workflow starts with the continuous online measurement of outer wall temperatures transients on a pipe. Visualization is implemented within the FAMOSi viewer software. In a second step, inner wall temperatures are directly calculated. In a third step, the resulting linearly elastic stress history will be calculated as the basis for subsequent code conforming fatigue assessment. Subsequently, the related advanced fatigue assessment methods of the three staged AFC-approach are addressed.

  6. Microstructure degradation in high temperature fatigue of TiAl

    Czech Academy of Sciences Publication Activity Database

    Kruml, Tomáš; Obrtlík, Karel

    2014-01-01

    Roč. 65, AUG (2014), s. 28-32. ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP107/11/0704 Institutional support: RVO:68081723 Keywords : Low cycle fatigue * lamellar TiAl alloy * high temperature fatigue * dislocations Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.275, year: 2014

  7. Special samples for investigation into kinetics of blind fatigue cracks

    International Nuclear Information System (INIS)

    Samples designed for investigation into kinetics of elliptic and semi-elliptic fatigue cracks in construction large-size elements and for evaluation of structural material resistance to fracture are developed. Data on form changing of blind fatigue cracks in vessel steel 15KH2MFA are obtained; it is shown, that material anisotropy and load kind affect essentially blind fatigue crack forms

  8. Mental fatigue induced by prolonged self-regulation does not exacerbate central fatigue during subsequent whole-body endurance exercise

    OpenAIRE

    Benjamin ePageaux; Samuele Maria Marcora; Vianney eRozand; Romuald eLepers

    2015-01-01

    It has been shown that the mental fatigue induced by prolonged self-regulation increases perception of effort and reduces performance during subsequent endurance exercise. However, the physiological mechanisms underlying these negative effects of mental fatigue are unclear. The primary aim of this study was to test the hypothesis that mental fatigue exacerbates central fatigue induced by whole-body endurance exercise. Twelve subjects performed 30 min of either an incongruent Stroop task to in...

  9. Unipolar and bipolar fatigue in antiferroelectric lead zirconate thin films and evidences for switching-induced charge injection inducing fatigue

    OpenAIRE

    Lou, X. J.; Wang, J.

    2010-01-01

    For the first time, we show that unipolar fatigue does occur in antiferroelectric capacitors, confirming the predictions of a previous work [Appl. Phys. Lett., 94, 072901 (2009)]. We also show that unipolar fatigue in antiferroelectrics is less severe than bipolar fatigue if the driving field is of the same magnitude. This phenomenon has been attributed to the switching-induced charge injection, the main cause for polarization fatigue in ferroelectric and antiferroelectric materials. Other ev...

  10. Study of corrosion and corrosion fatigue properties of 10KhSND steel in natural sea water and in environment saturated with marine bacteria

    International Nuclear Information System (INIS)

    Corrosion and corrosion fatigue tests of samples of the 10KhSND steel in natural sea water, in sterile sea water and in sea water rich in nutrition for microorganisms, are performed. It is established that the effect of corrosion biologic factor changes with time. In the initial period of tests due to the active growth of microorganisms heterogeneity of sample surface increases which promotes the appearance of multiple patrs of differential aeration, and resistance of steel to low-cycle corrosion fatigue decreases. 2-4 days later steel fatigue resistance becomes similar in all media studied. The connection of corrosion kinetics and corrosion fatigue with the intensity of develpment of microorganisms is noted

  11. Fatigue property and fatigue cracks of ultra-fine grained copper processed by equal-channel angular pressing

    Czech Academy of Sciences Publication Activity Database

    Wang, Q.; Du, Z.; Liu, X.; Kunz, Ludvík

    2011-01-01

    Roč. 2011, č. 682 (2011), s. 231-237. ISSN 1013-9826 Institutional research plan: CEZ:AV0Z20410507 Keywords : ultrafine-grained copper * equal channel angular pressing * fatigue * fatigue cracks Subject RIV: JL - Materials Fatigue, Friction Mechanics

  12. How does cognitive behaviour therapy reduce fatigue in patients with chronic fatigue syndrome? The role of physical activity.

    NARCIS (Netherlands)

    Wiborg, J.F.; Knoop, H.; Stulemeijer, M.; Prins, J.B.; Bleijenberg, G.

    2010-01-01

    BACKGROUND: Cognitive behaviour therapy (CBT) is known to reduce fatigue severity in chronic fatigue syndrome (CFS). How this change in symptomatology is accomplished is not yet understood. The purpose of the present study was to determine whether the effect of CBT on fatigue is mediated by an incre

  13. Effects of Local and Widespread Muscle Fatigue on Movement Timing

    Science.gov (United States)

    Cowley, Jeffrey C.; Dingwell, Jonathan B.; Gates, Deanna H.

    2014-01-01

    Repetitive movements can cause muscle fatigue, leading to motor reorganization, performance deficits, and/or possible injury. The effects of fatigue may depend on the type of fatigue task employed, however. The purpose of this study was to determine how local fatigue of a specific muscle group versus widespread fatigue of various muscle groups affected the control of movement timing. Twenty healthy subjects performed an upper-extremity low-load work task similar to sawing for 5 continuous minutes both before and after completing a protocol that either fatigued all the muscles used in the task (widespread fatigue) or a protocol that selectively fatigued the primary muscles used to execute the pushing stroke of the sawing task (localized fatigue). Subjects were instructed to time their movements with a metronome. Timing error, movement distance, and speed were calculated for each movement. Data were then analyzed using a goal-equivalent manifold (GEM) approach to quantify changes in goal-relevant and non-goal-relevant variability. We applied detrended fluctuation analysis to each time series to quantify changes in fluctuation dynamics that reflected changes in the control strategies used. After localized fatigue, subjects made shorter, slower movements and exerted greater control over non-goal-relevant variability. After widespread fatigue, subjects exerted less control over non-goal-relevant variability and did not change movement patterns. Thus, localized and widespread muscle fatigue affected movement differently. Local fatigue may reduce the available motor solutions and therefore cause greater movement reorganization than widespread muscle fatigue. Subjects altered their control strategies but continued to achieve the timing goal after both fatigue tasks. PMID:25183157

  14. STUDY ON FATIGUE SHORT CRACK GROWTH LAW AND FATIGUE LIFE FOR MEDIUM CARBON STEELS

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels-35CrMo and 42CrMo are investigated under the different stress ratios R=0.1, 0.3) and three-point bending condition. The relationships between the maximum stress range at the notch root Δσmax and the number of cycles before fatigue crack initiation Ni are determined. The threshold stresses of fatigue crack initiation (Δσmax)th are got, and the smallcrack growth laws are obtained for these steels. An effective and convenient method is proposed for predicting the fatigue life of the notch specimens.

  15. A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

    Science.gov (United States)

    Pejkowski, Łukasz; Skibicki, Dariusz

    2016-08-01

    This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The criterion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are: function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S-N curves: tension-compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promising. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the non-proportionality of loading.

  16. GENERALIZED FATIGUE CONSTANT LIFE CURVE AND TWO-DIMENSIONAL PROBABILITY DISTRIBUTION OF FATIGUE LIMIT

    Institute of Scientific and Technical Information of China (English)

    熊峻江; 武哲; 高镇同

    2002-01-01

    According to the traditional fatigue constant life curve, the concept and the universal expression of the generalized fatigue constant life curve were proposed.Then, on the basis of the optimization method of the correlation coefficient, the parameter estimation formulas were induced and the generalized fatigue constant life curve with the reliability level p was given.From P-Sa-Sm curve, the two-dimensional probability distribution of the fatigue limit was derived.After then, three set of tests of LY11 CZ corresponding to the different average stress were carried out in terms of the two-dimensional up-down method.Finally, the methods are used to analyze the test results, and it is found that the analyzedresults with the high precision may be obtained.

  17. AREVA Fatigue Concept (AFC) - an integrated and multi-disciplinary approach to the fatigue assessment of NPP components

    International Nuclear Information System (INIS)

    The AREVA fatigue concept (AFC) provides for a multi-step and multi-disciplinary process (process engineering, fatigue monitoring, fatigue analyses, etc.) against fatigue in the design and construction phase and also during the entire operation cycle of nuclear power plants (NPPs). The ensuing fatigue analyses are based on the real operational loads measured continuously on site in the plant. The entire process of fatigue design is based on an installed fatigue monitoring system, the FAMOS. This way, realistic load data are available. This system enables a reliable and realistic fatigue assessment of stressed components. FAMOS, as the central module of the AFC, contributes critically to the management of the component ageing problem and enables the identification of operating modes unfavorable to fatigue. Moreover, code conforming fatigue usage factors can be determined for the lifetime of the plant. The direct processing of the measured temperatures is immediately used for a fast fatigue evaluation (FFE). By means of FFE, the inverse thermal field at the inner surface of the pipe is calculated and transferred from measuring location to the component of concern for stress calculation. Then, a real time fatigue evaluation of the cumulative usage factor (CUF) can be performed after every operational cycle. This procedure is highly automated and gives a first fatigue status of the power plant. In the framework of the periodic safety inspection (PSI), a detailed fatigue calculation conforming to the code rules is carried out in order to determine the current state of the plant. This detailed fatigue check is based on the real loads (specification of thermal transient loads) and finite element analyses (FEA) in connection with the local strain approach to design against fatigue. These FEA always include transient thermal determination of the temperature field and subsequent determination of stresses and strains. The latter analyses may consist of simplified elastic or

  18. Fatigue life improvement in fatigue-aged fastener holes using the cold expansion technique

    OpenAIRE

    Zhang, Xiang; Wang, Z.

    2003-01-01

    The use of cold expansion process as a life extension technique on aircraft structural joints was investigated. The primary focus was an experimental test programme consisting of open-hole and low-load transfer joint specimens made of 2024-T351 aluminium alloy and pre-fatigued to 25, 50 and 75% of the baseline fatigue life for plain holes. The FALSTAFF loading spectrum was applied. The results indicate that significant life improvements can be obtained through cold expansion...

  19. SHIFTING OF ACTIVATION CENTER IN THE BRAIN DURING MUSCLE FATIGUE: AN EXPLANATION OF MINIMAL CENTRAL FATIGUE?

    OpenAIRE

    Liu, Jing Z; Lewandowski, Beth; Karakasis, Chris; Yao, Bing; Siemionow, Vlodek; Sahgal, Vinod; Yue, Guang H

    2007-01-01

    Accumulating evidence suggests that the overall level of cortical activation controlling a voluntary motor task that leads to significant muscle fatigue does not decrease as much as the activation level of the motoneuron pool projecting to the muscle. One possible explanation for this “muscle fatigue>cortical fatigue” phenomenon is that the brain is an organ with built-in redundancies: it has multiple motor centers and parallel pathways, and the center of activation may shift from one locatio...

  20. Studies on fatigue life enhancement of pre-fatigued spring steel specimens using laser shock peening

    International Nuclear Information System (INIS)

    Highlights: • Laser peening significantly extended fatigue life of pre-fatigued spring steel. • Increase in fatigue life of laser peened specimens was more than 15 times. • Black PVC tape is an effective coating for laser peening of ground surfaces. • Repeat peening repaired local surface melted regions on laser peened surface. • Technique is effective for life extension of in-service automobile parts. - Abstract: SAE 9260 spring steel specimens after enduring 50% of their mean fatigue life were subjected to laser shock peening using an in-house developed 2.5 J/7 ns pulsed Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser for studying their fatigue life enhancement. In the investigated range of process parameters, laser shock peening resulted in the extension of fatigue life of these partly fatigue damaged specimens by more than 15 times. Contributing factors for the enhanced fatigue life of laser peened specimens are: about 400 μm thick compressed surface layer with magnitude of surface stress in the range of −600 to −700 MPa, about 20% increase in surface hardness and unaltered surface finish. For laser peening of ground steel surface, an adhesive-backed black polyvinyl chloride (PVC) tape has been found to be a superior sacrificial coating than conventionally used black paint. The effect of repeated laser peening treatment was studied to repair locally surface melted regions and the treatment has been found to be effective in re-establishing desired compressive stress pattern on the erstwhile tensile-stressed surface

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

    Science.gov (United States)

    Choi, Sung R.; Salem, Jonathan A.

    1995-01-01

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

  2. Experimental Validation of a New Dynamic Muscle Fatigue Model

    OpenAIRE

    Seth, Deep; Chablat, Damien; Sakka, Sophie; Bennis, Fouad

    2016-01-01

    Muscle fatigue is considered as one of the major risk factor causing Musculo-Skeletal Disorder (MSD). To avoid MSD the study of muscle fatigue is very important. For the study of muscle fatigue a new model is developed by modifying the Ruina Ma's dynamic muscle fatigue model and introducing the muscle co-contraction factor 'n' in this model.The aim of this paper is to experimentally validate a dynamic muscle fatigue model using Electromyography (EMG) and Maximum Voluntary Contraction (MVC) da...

  3. Random accumulated damage evaluation under multiaxial fatigue loading conditions

    Directory of Open Access Journals (Sweden)

    V. Anes

    2015-07-01

    Full Text Available Multiaxial fatigue is a very important physical phenomenon to take into account in several mechanical components; its study is of utmost importance to avoid unexpected failure of equipment, vehicles or structures. Among several fatigue characterization tools, a correct definition of a damage parameter and a load cycle counting method under multiaxial loading conditions show to be crucial to estimate multiaxial fatigue life. In this paper, the SSF equivalent stress and the virtual cycle counting method are presented and discussed, regarding their physical foundations and their capability to characterize multiaxial fatigue damage under complex loading blocks. Moreover, it is presented their applicability to evaluate random fatigue damage.

  4. Fatigue In Continuous-Fiber/Metal-Matrix Composites

    Science.gov (United States)

    Johnson, William S.

    1992-01-01

    Report describes experimental approaches to quantification of fatigue damage in metal-matrix composites (MMC's). Discusses number of examples of development of damage and failure along with associated analytical models of behavior of MMC. Objectives of report are twofold. First, present experimental procedures and techniques for conducting meaningful fatigue tests to detect and quantify fatigue damage in MMC's. Second, present examples of how fatigue damage initiated and grows in various MMC's. Report furnishes some insight into what type of fatigue damage occurs and how damage quantified.

  5. Creep-fatigue life prediction: What about initiation

    International Nuclear Information System (INIS)

    Metallographical observations permit the nature of creep and fatigue damage to be exhibited and give some information on the creep-fatigue interaction. The macroscopic models can make qualitative use of these data. A Damage Mechanics model is proposed, which takes into account the initiation and propagation stages during the fatigue process. The implementation of new creep-fatigue rules leads to a good modelization of any creep-fatigue sequence tests or LCF tests. A unique set of material dependent coefficients is needed for both in-air and in-vacuum tests. (orig.)

  6. Muscle Fatigue Increases the Probability of Developing Hyperalgesia in Mice

    OpenAIRE

    Yokoyama, Takeshi; Lisi, Tammy L.; Moore, Steven A.; Sluka, Kathleen A.

    2007-01-01

    Chronic muscle pain is a major clinical problem that is often associated with fatigue. Conversely, chronic fatigue conditions are commonly associated with muscle pain. We tested the hypothesis that muscle fatigue enhances hyperalgesia associated with injection of acidic saline into muscle. We evaluated mechanical sensitivity of the paw (von Frey) in mice after 2 intramuscular injections of saline (20 µL; pH 4, pH 5, pH 6, pH 7.2) in a fatigue and a control group. To induce fatigue, mice were ...

  7. A preliminary bending fatigue spectrum for steel monostrand cables

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.; Kotas, Agnieszka

    2011-01-01

    This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension and...

  8. Partial Safety Factors for Fatigue Design of Wind Turbine Blades

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    accumulation is determined from variable amplitude fatigue tests with the Wisper and Wisperx spectra. The statistical uncertainty for the assessment of the fatigue loads is also investigated. The partial safety factors are calibrated for design load case 1.2 in IEC 61400-1. The fatigue loads are determined......In the present paper calibration of partial safety factors for fatigue design of wind turbine blades is considered. The stochastic models for the physical uncertainties on the material properties are based on constant amplitude fatigue tests and the uncertainty on Miners rule for linear damage...

  9. Nondestructive detection of fatigue damage accumulation of RPV steel

    International Nuclear Information System (INIS)

    Nondestructive methods for measurement and evaluation of fatigue damage in A508 RPV steels have been investigated for inservice inspection of fatigue damage accumulation during the service operation of reactor vessels. One is a newly developed electrochemical method which can detect and evaluate the fatigue damage accumulated in a material before initiation of cracks and the other is the one based upon a quantitative relationship between microcrack density at surface and fatigue damage accumulation represented by parameters such as usage factor or Coffin-Manson type damage parameter. Detection mechanisms of fatigue damage by these methods were described in details

  10. Compassion fatigue and the adult protective services social worker.

    Science.gov (United States)

    Bourassa, Dara Bergel

    2009-04-01

    Compassion fatigue is a relatively new term that describes the symptoms that are experienced by social workers and other helping professionals who work with clients experiencing trauma. This article defines the concept of compassion fatigue and relates compassion fatigue to Adult Protective Services (APS) social workers. It is proposed that APS social workers may be susceptible to the deleterious effects of compassion fatigue due to the nature of their work and environment. Suggestions for avoidance of compassion fatigue are also discussed, including self-care strategies and the need for continuing education regarding this phenomenon. PMID:19308828

  11. Fatigue Damage Accumulation of Steel/rubber Composite

    Institute of Scientific and Technical Information of China (English)

    Zhenhui TIAN; Huifeng TAN; Xingwen DU

    2006-01-01

    The fatigue damage accumulation of [±20°] laminated steel cord reinforced rubber composite under T-T loading was studied. Results indicate that the increase in the cyclic maximum strain exhibits three-stage tendency in the process of fatigue. The macroscopic fatigue damage initiates from the ends of steel cords in the form of cylindrical crack. Damage propagates along with the increase in crack numbers, the cord/matrix interface debonding and the growth of interply cracks. By using the dynamic creep as parameter, a linear fatigue damage accumulation model was established. This model can be used under dual loading conditions to estimate the residual fatigue life of the specimen.

  12. Influence of laser treatment on the fatigue of notched bar

    Institute of Scientific and Technical Information of China (English)

    ZhangHui; LingWeiye; JiangShouwei

    2003-01-01

    Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.

  13. SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA

    Institute of Scientific and Technical Information of China (English)

    Z.X.Wu; X.C.Wu

    2001-01-01

    The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.

  14. Tensile and Fatigue Properties of Free-Standing Cu Foils

    Institute of Scientific and Technical Information of China (English)

    Caiyun Dai; Xiaofei Zhu; Guangping Zhang

    2009-01-01

    Tensile and fatigue properties of free-standing as-rolled Cu foils were investigated by means of uniaxial tensile and dynamic bending tests. A special testing system was established to evaluate fatigue behavior of a mi-croscale material subjected to dynamic bending load. The experimental results show that the yield strength increases, but the fracture strain and fatigue resistance decrease with decreasing foil thickness. Deformation and fatigue damage behavior was characterized. The size effect on tensile and fatigue properties of the Cu foils are evaluated to get further understanding of the mechanical behavior of the micrometer-scale metallic materials.

  15. Fatigue life of metal treated by magnetic field

    Institute of Scientific and Technical Information of China (English)

    Liu Zhao-Long; Hu Hai-Yun; Fan Tian-You; Xing Xiu-San

    2009-01-01

    This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statis-tical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the dynamic equation of microcrack growth, where the influence of magnetization is described by an additional term in the potential energy of microcrack. The statistical value of fatigue life of metal under magnetic field is derived, which is expressed in terms of magnetic field and macrophysical as well as microphysical quantities. The fatigue life of AISI 4140 steel in static magnetic field from this theory is basically consistent with the experimental data.

  16. Practitioner Review: Chronic Fatigue Syndrome in Childhood

    Science.gov (United States)

    Garralda, M. Elena; Chalder, Trudie

    2005-01-01

    RBackground: Chronic fatigue syndrome (CFS) is being increasingly recognized in children and adolescents. Yet comparatively little attention has been given in the literature to management. Methods: Description of the main features of the disorder, precipitating and maintaining factors and diagnostic assessment. Outline of different views on the…

  17. Corrosion Fatigue in District Heating Water Tanks

    DEFF Research Database (Denmark)

    Maahn, Ernst Emanuel

    1996-01-01

    Three candidate materials for construction of buffer tanks for district heating water have been tested for corrosion fatigue properties in a district heating water environment. The investigation included Slow Strain Rate Testing of plain tensile specimens, crack initiation testing by corrosion...

  18. Dynamic Fatigue of a Titanium Silicate Glass

    Science.gov (United States)

    Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly A.; Smith, W. Scott (Technical Monitor)

    2002-01-01

    A dynamic fatigue study was performed on a Titanium Silicate Glass in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N=23 to stress corrosion in ambient conditions).

  19. Mechanisms of aging and fatigue in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Genenko, Yuri A. [Sonderforschungsbereich 595, Institut für Materialwissenschaft, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Glaum, Julia [Department of Materials Science and Engineering, University of New South Wales, Sydney (Australia); Hoffmann, Michael J. [Institut für keramische Werkstoffe, Haid-und-Neu Str. 7, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Albe, Karsten, E-mail: albe@mm.tu-darmstadt.de [Sonderforschungsbereich 595, Institut für Materialwissenschaft, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany)

    2015-02-15

    Highlights: • Experiments on aging and fatigue of bulk ferroelectrics are thoroughly reviewed. • Lead-based PZT and lead-free BNT–BT and KNN materials are covered. • Various fatigue regimes and factors are classified. • Defect associate formation and alignment are analyzed by density functional theory. • Emerging of internal bias field is studied within drift-diffusion approach. - Abstract: A comprehensive review of aging and fatigue phenomena in bulk polycrystalline ferroelectrics is presented. Three material classes are covered, namely the most widely used Pb[Zr{sub 1−x}Ti{sub x}]O{sub 3} (PZT) ceramics and lead-free materials, including those based on bismuth sodium titanate Bi{sub 1/2}Na{sub 1/2}TiO{sub 3} (BNT) and alkali niobate [K{sub x}Na{sub 1−x}]NbO{sub 3} (KNN). Aging is studied in poled and unpoled states both experimentally and theoretically. The variety of different loading regimes for fatigue includes DC electric field, unipolar, sesquipolar and bipolar cycling and all these differently combined with mechanical loading at different frequencies and temperatures. The role of device geometries and electrode materials is addressed and models describing charge migration and defect dipole re-orientation are discussed in the context of recent experimental studies.

  20. An analytical thermal fatigue crack growth approach

    International Nuclear Information System (INIS)

    The paper presents recent works on the thermal fatigue crack growth approach in structure integrity analysis proposed by nuclear standard codes such as A16 Appendix of RCC-MR. The proposed approach for crack growth is used to study the mechanisms leading to cracking of piping as a result of thermal loading in mixed flow zones

  1. Neuroaetiology of chronic fatigue syndrome : An overview

    NARCIS (Netherlands)

    Sanders, Patricia; Korf, Jakob

    2008-01-01

    Chronic fatigue syndrome (CFS) is now recognized as a medial disorder. In contrast to recent related reports, the present review focuses primarily on aetiological aspects of CFS. Four major hypotheses are reviewed. (1) Although CFS is often associated with viral infection, the presence of viruses ha

  2. Fatigue accumulation in an oscillating plate

    Czech Academy of Sciences Publication Activity Database

    Eleuteri, M.; Kopfová, J.; Krejčí, Pavel

    2013-01-01

    Roč. 6, č. 4 (2013), s. 909-923. ISSN 1937-1632 R&D Projects: GA ČR GAP201/10/2315 Institutional support: RVO:67985840 Keywords : elastoplastic plate * Prandtl-Ishlinskii operator * material fatigue Subject RIV: BA - General Mathematics http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=8092

  3. Fatigue Damage Predictions in Aluminium Constructions

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher; Toernqvist, Rikard; Nielsen, Poul Erik

    2002-01-01

    The paper describes parts of the outcome of a large Danish research project on Large Scale Aluminum Connections. The topic addressed is calculation of fatigue failure in complicated welded aluminum connections. The calculation procedure is based on a S-N curve for the hot-spot stresses at the weld...... crack growth in plane connections with a edge crack is performed....

  4. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

    K Bhanu Sankara Rao

    2003-06-01

    There would be considerable benefits in developing new structural materials where high use temperatures and strength coupled with low density are minimum capabilities. Nickel and titanium aluminides exhibit considerable potential for near-term application in various branches of modern industry due to the number of property advantages they possess including low density, high melting temperature, high thermal conductivity, and excellent environmental resistance, and their amenability for significant improvment in creep and fatigue resistance through alloying. Reliability of intermetallics when used as engineering materials has not yet been fully established. Ductility and fracture toughness at room and intermediate temperatures continue to be lower than the desired values for production implementation. In this paper, progress made towards improving strain-controlled fatigue resistance of nickel and titanium aluminides is outlined. The effects of manufacturing processes and micro alloying on low cycle fatigue behaviour of NiAl are addressed. The effects of microstructure, temperature of testing, section thickness, brittle to ductile transition temperature, mean stress and environment on fatigue behaviour of same -TiAl alloys are discussed.

  5. Prescribed Travel Schedules for Fatigue Management

    Science.gov (United States)

    Whitmire, Alexandra; Johnston, Smith; Lockley, Steven

    2011-01-01

    The NASA Fatigue Management Team is developing recommendations for managing fatigue during travel and for shift work operations, as Clinical Practice Guidelines for the Management of Circadian Desynchrony in ISS Operations. The Guidelines provide the International Space Station (ISS ) flight surgeons and other operational clinicians with evidence-based recommendations for mitigating fatigue and other factors related to sleep loss and circadian desynchronization. As much international travel is involved both before and after flight, the guidelines provide recommendations for: pre-flight training, in-flight operations, and post-flight rehabilitation. The objective of is to standardize the process by which care is provided to crewmembers, ground controllers, and other support personnel such as trainers, when overseas travel or schedule shifting is required. Proper scheduling of countermeasures - light, darkness, melatonin, diet, exercise, and medications - is the cornerstone for facilitating circadian adaptation, improving sleep, enhancing alertness, and optimizing performance. The Guidelines provide, among other things, prescribed travel schedules that outline the specific implementation of these mitigation strategies. Each travel schedule offers evidence based protocols for properly using the NASA identified countermeasures for fatigue. This presentation will describe the travel implementation schedules and how these can be used to alleviate the effects of jet lag and/or schedule shifts.

  6. Fatigue Feature Classification for Automotive Strain Data

    International Nuclear Information System (INIS)

    Fatigue strain signal were analysed using data segmentation and data clustering. For data segmentation, value of fatigue damage and global statistical signal analysis such as kurtosis was obtained using specific software. Data clustering were carried out using K-Mean clustering approaches. The objective function was calculated in order to determine the best numbers of groups. This method is used to calculate the average distance of each data in the group from its centroid. Finally, the fatigue failure indexes of metallic components were generated from the best number of group that has been acquired. Based on four data collect from two different roads which are D1, D2, the index value generated is not the same for all of data because due to K-Mean clustering, the best group is different for each of the data used. The maximum indexes generated are different for two types of road and namely the index 4 for D1 and index 5 for D2. Due to the road surface condition, higher distributions of the best groups give higher values of index and reflect to higher fatigue damage experienced by the system.

  7. Finite element simulation of asphalt fatigue testing

    DEFF Research Database (Denmark)

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

    damage mechanics.The paper describes how continuum damage mechanics may be used with a finite element program to explain the progressive deterioration of asphalt mixes under laboratory fatigue testing. Both constant stress and constant strain testing are simulated, and compared to the actual results from...

  8. Roughness analysis of local fatigue fracture surface

    Czech Academy of Sciences Publication Activity Database

    Major, Štěpán; Hubálovský, Š.

    2013-01-01

    Roč. 7, č. 2 (2013), s. 65-72. ISSN 1998-4448 Institutional support: RVO:68378297 Keywords : bending-torsion * biaxial loading * fatigue * fractography Subject RIV: JJ - Other Materials http://www.naun.org/cms.action?id=2828

  9. Fatigue Performance of Fiber Reinforced Concrete

    DEFF Research Database (Denmark)

    Jun, Zhang; Stang, Henrik

    1996-01-01

    The objective of the present study is to obtain basic data of fibre reinforced concrete under fatigue load and to set up a theoretical model based on micromechanics. In this study, the bridging stress in fiber reinforced concrete under cyclic tensile load was investigted in details. The damage...

  10. Conquering fatigue: the battle for engagement

    NARCIS (Netherlands)

    J.F. Hopstaken (Jesper)

    2016-01-01

    markdownabstractThe central aim of this dissertation was to examine how motivation influences fatigue and through what psychophysiological mechanisms it influences cognition. With this aim in mind, task disengagement, which is defined as an affective, cognitive, and motivational state of commitment

  11. Wheelchair tire rolling resistance and fatigue.

    Science.gov (United States)

    Kauzlarich, J J; Thacker, J G

    1985-07-01

    The hysteresis loss theory of rolling resistance is developed for solid rubber wheelchair tires. The analysis is used to correlate test data for a clay-filled natural rubber and a polyurethane tire material. A discussion of tire rolling work, hysteresis loss factor measurement, and rolling loss measurement is presented. An example calculation of rolling resistance for a polyurethane tire is given in detail. The subject of solid rubber tire design is developed on the basis of recommended fatigue life theory and practice. It is shown that polyurethane tires have a useful fatigue life due to a high shear modulus at useful values of hardness. This characteristic of polyurethane, if exploited, is predicted to lead to a tire with a lower rolling resistance than other wheelchair tires available. The effect of surface roughness on rolling resistance is briefly discussed and some experimental results are listed. The purpose of this paper is to give the rehabilitation engineer the means for wheelchair tire rolling resistance and fatigue life design and the methods to assess the tire characteristics when a tire design is modified or a new tire material is contemplated. Other important design factors, such as wear and chemical degradation, are not discussed, but references are suggested for information on these topics. As in most research and development projects, this study raises problems which need further work. For example, the fatigue properties of the rubber compounds employed in this application are not completely understood; this subject is planned for future investigation. PMID:3835263

  12. The effect of fatigue on interlimb communication

    DEFF Research Database (Denmark)

    Gervasio, Sabata; Stevenson, Andrew James Thomas; Mrachacz-Kersting, Natalie

    2015-01-01

    Performing repeated motor tasks during a volleyball, basketball, or soccer game can lead to muscular fatigue, inducing a decrease in the capacity of a muscle to generate force, changes in motor coordination, and an alteration in motor performance. These changes have been attributed to an elevated...

  13. Fatigue in early Parkinson’s disease

    Institute of Scientific and Technical Information of China (English)

    秦朝晖

    2012-01-01

    Objective To investigate the prevalence,character-istics and risk factors of fatigue in a large cohort of subjects with early Parkinson’s disease (PD).Methods A total of 391 individuals with PD,recrutied in Linzhi trial, were re-screened. Early, non-depressed subjects

  14. American Ginseng Teaand Resist in Fatigue

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The fatigue is a main factor to endanger the human health in the 21st century. In the current society, because the rhythm of life is accelerated and overworked for a long time or beared greater psychological pressure for a long time, if not rest reasonable for

  15. Effect of biomimetic coupling units' morphologies on rolling contact fatigue wear resistance of steel from machine tool rolling tracks

    Science.gov (United States)

    Yang, Wanshi; Zhou, Hong; Sun, Liang; Wang, Chuanwei; Chen, Zhikai

    2014-04-01

    The rolling contact fatigue wear resistance plays an important role on ensuring machining precision of machine tool using rolling tracks. Bio-inspired wearable surfaces with the alternated hardness were prepared on the specimen of steel material from machine tool rolling tracks by biomimetic coupling laser remelting method to imitate biological coupling principle. The microstructures and micromorphologies of bionic units in different sizes were characterized by optical microscope. The specimens with bionic units in different sizes and distributions were tested for rolling contact fatigue wear resistance. Combining the finite element analysis and the results of wear tests, a discussion on rolling contact fatigue wear was had. The specimens with bionic units had better rolling contact fatigue wear resistance than the untreated one, while the specimens with bionic units in the alternative depth's distributions present a better rolling contact fatigue wear resistance than the ones with bionic units in the single depth's distribution. It attributed to the alternative distribution made further improvement on the dispersion of depth of stress concentration.

  16. Chronic fatigue in cancer patients treated with radiotherapy

    International Nuclear Information System (INIS)

    Fatigue is one of the most prevalent and profound symptoms related to both malignancy and anti-neoplastic treatment. It is being reported in 60% to 80% of cancer patients. We review the correlation between the cancer-related fatigue syndrome and radiotherapy. In patients undergoing radiotherapy, fatigue is often cumulative and may reach its peak during the last weeks of treatment. The presence of fatigue prior to therapy initiation is the most important predictive factor of the occurrence of radiotherapy-related cancer fatigue syndrome. Occasionally, fatigue persists for a prolonged period of months and even years beyond radiotherapy. Anemia may be one of major causative factors responsible for the development of the cancer-related fatigue syndrome. Fatigue has an enormous physical, mental, emotional, and economic impact on cancer patients, their families and care-providers. The treatment of radiation-related fatigue remains unknown. The initial approach should cover efforts aimed at the correction of potential etiologies, especially anemia. Education concerning fatigue greatly benefits some patients. It seems that exercise may be beneficial in relieving fatigue, bearing in mind that the exercise program for cancer patients should be initiated gradually and significantly individualized. (author)

  17. Survey of trend and factors in perinatal maternal fatigue.

    Science.gov (United States)

    Cheng, Ching-Yu; Chou, Yu-Hua; Wang, Panchalli; Tsai, Jung-Mei; Liou, Shwu-Ru

    2014-05-18

    Few studies have investigated maternal fatigue, particularly fatigue throughout the duration of pregnancy and the postpartum period. The purpose of this study was to explore changes related to maternal fatigue from pregnancy to postpartum and the factors influencing fatigue. This prospective longitudinal study surveyed 197 pregnant women beyond 24 gestational weeks monthly until one month postpartum. The Multidimensional Assessment of Fatigue scale and one question about fatigue were used. Women at late pregnancy experienced a significant increase in level of fatigue, which remained high after childbirth. Those who were not happy about the pregnancy or were multiparas experienced a higher level of prenatal fatigue than their counterparts. At postpartum, mothers who were unemployed, had no one to help with childcare, or felt that the baby's night-time sleep pattern was a serious problem had a higher level of fatigue. Interventions can be planned and implemented at early pregnancy to reduce the prevalence of fatigue. Encouraging pregnant women to share experiences and thoughts about pregnancy and being a mother is suggested. Further studies that evaluate culturally sensitive instruments for fatigue are needed. PMID:24835296

  18. Influence of mean stress on fatigue strength of stainless steel

    International Nuclear Information System (INIS)

    In order to incorporate the mean stress effect in the design fatigue curve for designing nuclear power plant components, change in fatigue strength due to the mean stress and root causes of the change were investigated for Type 316 stainless steel. First, 20% cold work was applied to specimens of Type 316 stainless steel in order to reduce the cyclic strain hardening and softening during fatigue tests, and then, the specimens were subjected to stress controlled fatigue tests under the mean stress in air at room temperature. Although the mean stress tended to show a beneficial effect on the fatigue life under the same stress amplitude, it had a detrimental effect under the same strain range. It was shown that the reduction in fatigue life was brought about by the change in the effective strain, which was caused not only by the rise in the crack opening point but also by ratcheting deformation during the fatigue tests. The mean stress had little influence on the fatigue limit for the strain range. It was concluded that, although the mean stress reduced the fatigue life in the stress controlled fatigue tests, its effect did not need to be considered in the design fatigue curve because no significant change in the effective strain range occur in actual components. (author)

  19. Postural strategy changes with fatigue of the lumbar extensor muscles.

    Science.gov (United States)

    Wilson, Erin L; Madigan, Michael L; Davidson, Bradley S; Nussbaum, Maury A

    2006-04-01

    The purpose of this study was to investigate the effect of lumbar extensor fatigue on postural strategy in response to a balance perturbation. Anteriorly-directed force perturbations were applied to the upper back with a padded pendulum and attempted to challenge the postural control system without eliciting a stepping response. In three separate sessions, subjects were perturbed both before and after a fatiguing protocol that induced lumbar extensor fatigue to one of three different fatigue levels. Postural strategy was quantified using center of pressure position along with joint angles and joint torques for the ankle, knee, hip, and "low back" joints. Results showed both proactive and reactive changes in postural strategy. Proactive changes involved a slight anterior lean prior to the perturbation, and reactive changes were consistent with a shift toward more of a hip strategy with fatigue. In addition, results suggested that subjects classified as moving mostly at the hip prior to fatigue were more affected by fatigue compared to subjects classified as moving roughly equal amounts at the ankle and hip prior to fatigue. Increasing fatigue level exaggerated some, but not all, of the changes in postural strategy with fatigue. These findings illustrate that neuromuscular fatigue can influence postural strategy in response to a balance perturbation. PMID:16023345

  20. ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH

    Institute of Scientific and Technical Information of China (English)

    C.F.Lee; L.T.Hsiao

    2002-01-01

    In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the rc controlled node-released strategy are employed to study the fatigue crack opened/closed load (Pop) of A1 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed Pop values and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (Pmax) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of Pop/Pmax vs. Kmax and R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔKeff, the A1 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔKeff and R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves. According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.

  1. Environmentally assistant fatigue analysis for LWR reactor vessel nozzle

    International Nuclear Information System (INIS)

    Background: Considering the EAF (Environment Assistant Fatigue) effect during the design status is a key issue for generation Ⅲ nuclear power plant. Purpose: The calculation methodology of Fen (Environmentally Assistant Fatigue Factor) and strain ratio of ASME Code Case N-792 has been introduced in this paper. Methods: By creating 2D symmetry model of reactor pressure vessel nozzle, the environmentally assistant fatigue factor Fen and fatigue usage factor has been analyzed according Code Case N-792 with simplified and detailed integral methods. Results: The fatigue usage factor results of ASME-Ⅲ which does not consider environmental effect and Code Case N-792 which consider the environmental effect have been compared and discussed. Conclusions: And the fatigue life considering Fen effect of SCL1 section will reduce to about 1/3 of the life in air condition while the fatigue life of SCL2 decrease 3/5. (authors)

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

    Science.gov (United States)

    Wang, Qiliang; Zhang, Xianmin

    2015-10-01

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

  3. Development of fatigue life evaluation technique using miniature specimen

    International Nuclear Information System (INIS)

    To develop the fatigue life evaluation technique using miniature specimen, the investigation of the effect of specimen size and specimen shape on the fatigue life and the development of the fatigue testing machine, especially the extensometer, were carried out. The effect of specimen size on the fatigue life was almost negligible for the round-bar specimens. The shorter fatigue life at relatively low strain range conditions for the hourglass specimen that the standard specimen were observed. Therefore the miniature round-bar specimen was considered to be adequate for the fatigue life evaluation using small specimen. Several types of the extensometer system using a strain gauge and a laser has been developed for realizing the fatigue test of the miniature round-bar specimen at high temperature in vacuum. (author)

  4. Comparison of fatigue property between friction stir and TIG welds

    Institute of Scientific and Technical Information of China (English)

    Xunhong Wang; Kuaishe Wang; Yang Shen; Kai Hu

    2008-01-01

    The alloy 5052 was welded by friction stir welding (FSW) and tungsten inert gas (TIG) welding. The effect of welding processes (FSW and TIG) on the fatigue properties of 5052 aluminum-welded joints was analyzed based on fatigue testing, and the S-N curve of the joints were established. The results show that the fatigue properties of FSW welded joints are better than those of TIG welded joints. The fatigue strength is determined as 65 Mpa under 106 cycling of fatigue life. The microstructure of joints is fine grains and narrow HAZ zone in FSW welds, which inhibit the growth of cracks and produce high fatigue life compared with that of TIG welds. Fracture morphologies also show that the fatigue fracture results from weld defects.

  5. Fatigue Analysis of a Mono-Tower Platform

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune

    In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...... through linear-elastic fracture mechanics (LEFM). In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability as well as systems reliability is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters...... is investigated. The systems reliability index, estimated by using the fatigue elements with the fatigue strength expressed through SN relations, is found to be smaller than the systems reliability index estimated by using LEFM. It is shown that the systems reliability index is very sensitive to...

  6. MULTIAXIAL CREEP-FATIGUE LIFE EVALUATION UNDER PROPORTIONAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Y.Noguchi; M.Miyahara

    2004-01-01

    A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading.Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue loadings.

  7. Yang/Qi invigoration: an herbal therapy for chronic fatigue syndrome with yang deficiency?

    Science.gov (United States)

    Leong, Pou Kuan; Wong, Hoi Shan; Chen, Jihang; Ko, Kam Ming

    2015-01-01

    According to traditional Chinese medicine (TCM) theory, Yang and Qi are driving forces of biological activities in the human body. Based on the crucial role of the mitochondrion in energy metabolism, we propose an extended view of Yang and Qi in the context of mitochondrion-driven cellular and body function. It is of interest that the clinical manifestations of Yang/Qi deficiencies in TCM resemble those of chronic fatigue syndrome in Western medicine, which is pathologically associated with mitochondrial dysfunction. By virtue of their ability to enhance mitochondrial function and its regulation, Yang- and Qi-invigorating tonic herbs, such as Cistanches Herba and Schisandrae Fructus, may therefore prove to be beneficial in the treatment of chronic fatigue syndrome with Yang deficiency. PMID:25763095

  8. The chronic fatigue syndrome: a comprehensive approach to its definition and study. International Chronic Fatigue Syndrome Study Group.

    Science.gov (United States)

    Fukuda, K; Straus, S E; Hickie, I; Sharpe, M C; Dobbins, J G; Komaroff, A

    1994-12-15

    The complexities of the chronic fatigue syndrome and the methodologic problems associated with its study indicate the need for a comprehensive, systematic, and integrated approach to the evaluation, classification, and study of persons with this condition and other fatiguing illnesses. We propose a conceptual framework and a set of guidelines that provide such an approach. Our guidelines include recommendations for the clinical evaluation of fatigued persons, a revised case definition of the chronic fatigue syndrome, and a strategy for subgrouping fatigued persons in formal investigations. PMID:7978722

  9. Keep fatigue usage low for LTO. Benefits of load monitoring and related fatigue evaluations for long term operation

    International Nuclear Information System (INIS)

    Design fatigue calculations normally cover a service life of 40 years. Based on design transients with a specified number of cycles the evaluations have to prove that the fatigue usage after 40 years will stay below 1. In 40+ years of operation real loads can differ much from design loads so that premature ageing can occur. For long term operation, monitoring of real loads and detailed fatigue analysis for selected locations can be used to optimize operational modes in order to reduce the loads causing fatigue. As a result fatigue usage can be kept below 1 even for 60+ years. (author)

  10. Influence Of Surface Roughness On Ultra-High-Cycle Fatigue Of Aisi 4140 Steel.

    OpenAIRE

    Daniel Januário Cordeiro Gomes.; Ernani Sales Palma

    2015-01-01

    Low and high-cycle fatigue life regimes are well studied and are relatively well understood. However, recent fatigue studies on steels have shown that fatigue failures can occur at low amplitudes even below the conventional fatigue limit in the ultra-high-cycle fatigue range (life higher than 107 cycles). Fatigue life in the regime of 106 to 108 cycles-to-failure in terms of the influence of manufacturing processes on fatigue strength is examined. Specifically, the influe...

  11. Cancer-related fatigue. Clinical practice guidelines in oncology.

    Science.gov (United States)

    2003-07-01

    These guidelines propose a treatment algorithm in which patients are evaluated regularly for fatigue using a brief screening instrument, and are treated as indicated by their fatigue level. The algorithm's goal is to identify and treat all patients with fatigue that causes distress or interferes with their daily activities or functioning. Management of fatigue begins with primary oncology team members who perform the initial screening and either provide basic education and counseling or expand the initial screening to a more focused evaluation for moderate or higher levels of fatigue. At this point the patient is assessed for current disease and treatment status, a review of body systems, and an in-depth fatigue evaluation. In addition, the patient is assessed for the presence of seven treatable factors known to contribute to fatigue: pain, emotional distress, sleep disturbance, anemia, alterations in nutrition, deconditioning, and comorbidities. If any of these conditions are present, they should be treated according to practice guidelines, with referral to other care professionals as appropriate, and the patient's fatigue should be reevaluated regularly. If none of the seven factors are present or the fatigue is unresolved, selection of appropriate fatigue management and treatment strategies is considered within the context of the patient's clinical status: receiving active cancer treatment, receiving disease-free long-term follow-up, or receiving care at the end of life. Management of fatigue is cause-specific when conditions known to cause fatigue can be identified and treated. When specific causes, such as infection, fluid and electrolyte imbalances, or cardiac dysfunction, cannot be identified and corrected, nonpharmacologic and pharmacologic treatment of the fatigue should be considered. Nonpharmacologic interventions may include a moderate exercise program to improve functional capacity and activity tolerance, psychosocial programs to manage stress and

  12. Self-regulatory fatigue in chronic multisymptom illnesses: scale development, fatigue, and self-control

    Directory of Open Access Journals (Sweden)

    Solberg Nes L

    2013-03-01

    Full Text Available Lise Solberg Nes,1,3 Shawna L Ehlers,1 Mary O Whipple,2 Ann Vincent21Department of Psychiatry and Psychology, Mayo Clinic, Rochester, MN, USA; 2Fibromyalgia and Chronic Fatigue Clinic, General Internal Medicine, Mayo Clinic, Rochester, MN, USA; 3Center for Shared Decision Making and Collaborative Care Research, Oslo University Hospital, Oslo, NorwayBackground: Self-regulatory capacity involves ability to regulate thoughts, emotions, and behavior. Chronic multisymptom illnesses such as fibromyalgia and chronic fatigue syndrome are accompanied by numerous challenges, and have recently been associated with self-regulatory fatigue (SRF. Chronic multisymptom illnesses are also frequently associated with physical fatigue, and through development of a scale measuring SRF, the current study aimed to examine how SRF can be distinguished from physical fatigue. The study also sought to distinguish SRF from self-control.Methods: Two self-regulation researchers developed 30 items related to self-regulatory capacity. These items were distributed to patients (n = 296 diagnosed with chronic multisymptom illness together with validated measures of physical fatigue and self-control. A principal factor analysis was employed to examine factor structures, identify inter-item relationships, and aid in scale development.Results: The final proposed scale consisted of 18 items measuring self-regulatory capacity (SRF-18 with cognitive, emotional, and behavioral SRF components. Internal consistency and reliability was acceptable (Cronbach's α = 0.81. The final scale was moderately correlated with self-control (r = −0.48 and highly correlated with physical fatigue (r = 0.75, although more so with emotional (r = 0.72 and mental (r = 0.65 than physical (r = 0.46 fatigue components.Conclusion: The current study suggests a new scale for measurement of SRF in chronic multisymptom illness. Although cross-validation studies are necessary, such a scale may contribute to a

  13. Possible use of repeated cold stress for reducing fatigue in Chronic Fatigue Syndrome: a hypothesis

    Directory of Open Access Journals (Sweden)

    Shevchuk Nikolai A

    2007-10-01

    Full Text Available Abstract Background Physiological fatigue can be defined as a reduction in the force output and/or energy-generating capacity of skeletal muscle after exertion, which may manifest itself as an inability to continue exercise or usual activities at the same intensity. A typical example of a fatigue-related disorder is chronic fatigue syndrome (CFS, a disabling condition of unknown etiology and with uncertain therapeutic options. Recent advances in elucidating pathophysiology of this disorder revealed hypofunction of the hypothalamic-pituitary-adrenal axis and that fatigue in CFS patients appears to be associated with reduced motor neurotransmission in the central nervous system (CNS and to a smaller extent with increased fatigability of skeletal muscle. There is also some limited evidence that CFS patients may have excessive serotonergic activity in the brain and low opioid tone. Presentation of the hypothesis This work hypothesizes that repeated cold stress may reduce fatigue in CFS because brief exposure to cold may transiently reverse some physiological changes associated with this illness. For example, exposure to cold can activate components of the reticular activating system such as raphe nuclei and locus ceruleus, which can result in activation of behavior and increased capacity of the CNS to recruit motoneurons. Cold stress has also been shown to reduce the level of serotonin in most regions of the brain (except brainstem, which would be consistent with reduced fatigue according to animal models of exercise-related fatigue. Finally, exposure to cold increases metabolic rate and transiently activates the hypothalamic-pituitary-adrenal axis as evidenced by a temporary increase in the plasma levels of adrenocorticotropic hormone, beta-endorphin and a modest increase in cortisol. The increased opioid tone and high metabolic rate could diminish fatigue by reducing muscle pain and accelerating recovery of fatigued muscle, respectively. Testing

  14. Thermal fatigue of pipes induced by fluid temperature change. Effect of multiaxial pre-loading on fatigue strength

    International Nuclear Information System (INIS)

    This study investigates an effect of pre-inelastic multiaxial loading on failure lives in a followed high cycle fatigue test for SUS316 steel. In the multiaxial low cycle fatigue test for the pre-loading, two types of strain paths were employed which are a push-pull straining and a circle straining. The circle straining is the non-proportional loading in which axial strain ε and shear strain γ has 90 degree phase difference. Using the specimen fatigued in the pre-loading test, high cycle fatigue test was conducted by a rotating bending fatigue testing machine. Based on the obtained results, property of fatigue life in high cycle fatigue which received pre-loading under non-proportional loading is discussed. (author)

  15. 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

  16. Development of pressurized disc type fatigue testing system for equi-biaxial fatigue

    International Nuclear Information System (INIS)

    A testing method for investigating fatigue strength under equi-biaxial stress/strain condition was developed. In this method, the equi-biaxial stress condition was achieved by applying pressure on the surfaces of a disc-type specimen, for which the disc edge was constrained by supporting jigs. Air pressure was used to apply the cyclic loading and the failure of the specimen was determined by detecting the crack penetration of the specimen thickness. This method allows application of the cyclic equi-biaxial stress without a complex testing apparatus or a complex controlling system such as the testing system using the cruciform or tubular specimens, conventionally used for the fatigue test under the equi-biaxial stress condition. After developing the testing system, the configuration of the disc-type specimen was designed by finite element analysis so that a crack would be initiated at the center of the specimen. Then, carbon steel (SS400 in JIS) specimens were subjected to the fatigue test. The developed system was demonstrated to be able to initiate a fatigue crack at the center of the specimen and to detect the specimen failure successfully. The test results showed that the fatigue lifetime under equi-biaxial stress was longer than that under uniaxial stress for the same Von Mises equivalent strain range. (author)

  17. 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...... accomodate non-constant stress or strain, a mode factor may be introduced or the dissipated energy may be used instead of stress or strain.Cracking of asphalt (or other materials) may be described as a process consisting of three phases. In phase one diffuse microcracking is formed in the material. In the...... damage mechanics.The paper describes how continuum damage mechanics may be used with a finite element program to explain the progressive deterioration of asphalt mixes under laboratory fatigue testing. Both constant stress and constant strain testing are simulated, and compared to the actual results from...

  18. Thermal fatigue durability for advanced propulsion materials

    Science.gov (United States)

    Halford, Gary R.

    1989-01-01

    A review is presented of thermal and thermomechanical fatigue (TMF) crack initiation life prediction and cyclic constitutive modeling efforts sponsored recently by the NASA Lewis Research Center in support of advanced aeronautical propulsion research. A brief description is provided of the more significant material durability models that were created to describe TMF fatigue resistance of both isotropic and anisotropic superalloys, with and without oxidation resistant coatings. The two most significant crack initiation models are the cyclic damage accumulation model and the total strain version of strainrange partitioning. Unified viscoplastic cyclic constitutive models are also described. A troika of industry, university, and government research organizations contributed to the generation of these analytic models. Based upon current capabilities and established requirements, an attempt is made to project which TMF research activities most likely will impact future generation propulsion systems.

  19. Deformation Properties and Fatigue of Bituminous Mixtures

    Directory of Open Access Journals (Sweden)

    Frantisek Schlosser

    2013-01-01

    Full Text Available Deformation properties and fatigue performance are important characteristics of asphalt bound materials which are used for construction of pavement layers. Viscoelastic asphalt mixtures are better characterized via dynamic tests. This type of tests allows us to collate materials with regard to axle vibrations which lie usually in the range of 6 Hz–25 Hz for standard conditions. Asphalt modified for heat sensitivity in the range from −20°C to +60°C has significant impact on the overall characteristics of the mixture. Deformation properties are used as inputs for empirical mixture design, and fatigue performance of asphalt mixtures reflects the parameters of functional tests. Master curves convey properties of asphalt mixtures for various conditions and allow us to evaluate them without the need of time expensive testing.

  20. Research on Portable Fatigue Signal Detection System

    Directory of Open Access Journals (Sweden)

    Bowen Li

    2013-07-01

    Full Text Available According to the characteristics of human pulse wave signals, the acquisition system acquisition system with excellent performance is designed, 16 bit MCU MSP430 with ultralow power is used to record, process and transmit the collected pulse wave signals. In order to make the hardware part satisfy acquisition requirements of pulse wave, the paper focuses on discussing composition, operating principle, analysis method and performance parameter of analog circuit. The software part makes use of the design tools of Matlab graphical user interface (GUI for designing pulse wave signal measurement system. The trial on intelligent fatigue test signal adopts relatively unique methods no matter in hardware circuit design or software algorithm process, which provides important and meaningful reference for objective and quantitative research on fatigue signal.

  1. Fatigue Assessment of Threaded Riser Connections

    OpenAIRE

    Braun, Moritz,

    2014-01-01

    Threaded connections as found in applications like rigid riser, drillstrings, and workover riser are manufactured with sharp notches. Subjected to cyclic loading, those notches lead to high stress concentrations, which increase the risk of fatigue crack initiation significantly. A common connection type that has been the basis for extensive studies is the API Line Pipe connection. The basic API thread type consists of truncated triangular threads. In order to tighten the connection the male a...

  2. Fatigue Design of Hydraulic Turbine Runners

    OpenAIRE

    Huth, Hans-Jörg

    2005-01-01

    Turbine runners experience start-stop cycles and vibration cycles. Cracks initiated from service or manufacturing defects and propagated by start-stop cycles become critical when the stress intensity range due to vibrational loading exceeds the threshold for fatigue crack growth.In Francis turbine runners, semi-elliptical surface cracks tend to propagate from the quarter-circular transition of the welded T-joint transition between the blade and the band or crown. Assuming a crack to grow unde...

  3. Critical fatigue behaviour in brittle glasses

    Indian Academy of Sciences (India)

    Rajat Banerjee; Bikas K Chakrabarti

    2001-04-01

    The dynamic fatigue fracture behaviour in different glasses under various sub-threshold loading conditions are analysed here employing an anomalous diffusion model. Critical dynamical behaviour in the time-to-fracture and the growth of the micro-crack sizes, similar to that observed in such materials in the case of quasi-static (``instantaneous”) failures for above-threshold conditions, are predicted and compared with some of the experimental observations in different glasses.

  4. Fatigue fracture modes of a stainless steel

    International Nuclear Information System (INIS)

    The influence of strain hardening and martensite phase transformation on the fatigue fracture regions (pulsative tension) of a Stainless Steel type AISI 316 was investigated. This lead to the conclusion that the greater austenite strain hardening level only favours the occurrence of a brittle fracture. Also, in as much as the static induced martensite is concerned, a direct influence on the failure process was not observed, whereas, apparently, the one transformed under cyclic loading has no contribution to the rupture mechanisms. (author)

  5. Influence of muscular fatigue in evoked electromyogram

    International Nuclear Information System (INIS)

    In this work we present the results of the evaluation of the changes happened in M wave during application of functional electrical stimulation. Electromyogram from the tibialis anterior muscle and ankle angle were measured to determine the occurrence of the fatigue phenomenon. The results report a decrease of the signal amplitude and the median of the power spectrum and are encouraging for the development of strategies of control of FES applications

  6. Influence of muscular fatigue in evoked electromyogram

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, J; Acevedo, R; Tabernig, C [Rehabilitation Engineering and Neuromuscular and Sensorial Research Laboratory, National University of Entre Rios (Argentina)

    2007-11-15

    In this work we present the results of the evaluation of the changes happened in M wave during application of functional electrical stimulation. Electromyogram from the tibialis anterior muscle and ankle angle were measured to determine the occurrence of the fatigue phenomenon. The results report a decrease of the signal amplitude and the median of the power spectrum and are encouraging for the development of strategies of control of FES applications.

  7. The Research on Fatigue Driving Detection Algorithm

    OpenAIRE

    Zhui Lin; Lide Wang; Jieqiong Zhou; Tao Wang

    2013-01-01

    Researches on Driver Fatigue Detection System, which aims to ensure the safety of operations and to reduce traffic accidents caused by artificial factors, has been the major research subject in transportation safety. There is an enormous advantage in the method obtaining the driver's image by camera, We propose efficient tracking and detecting algorithm and with an appearance model based on haar-like features, finding out the accuracy and robustness of tracking of eyes movements and the confl...

  8. Pathologie des suspensions : la corrosion, la fatigue

    OpenAIRE

    Brevet, P.

    2005-01-01

    L'auteur fait une revue des désordres et des mécanismes de dégradation propres aux câbles de ponts suspendus et ponts à haubans, ainsi que d'une partie des désordres affectant les systèmes de protection ou les amortisseurs et leurs causes (corrosion et fatigue sont les principales origines de désordre traitées)

  9. The definition of disabling fatigue in children and adolescents

    Directory of Open Access Journals (Sweden)

    Thapar Anita

    2005-08-01

    Full Text Available Abstract Background Disabling fatigue is the main illness related reason for prolonged absence from school. Although there are accepted criteria for diagnosing chronic fatigue in adults, it remains uncertain as to how best to define disabling fatigue and Chronic Fatigue Syndrome (CFS in children and adolescents. In this population-based study, the aim was to identify children who had experienced an episode of disabling fatigue and examine the clinical and demographic differences between those individuals who fulfilled a narrow definition of disabling fatigue and those who fulfilled broader definitions of disabling fatigue. Methods Participants (aged 8–17 years were identified from a population-based twin register. Parent report was used to identify children who had ever experienced a period of disabling fatigue. Standardised telephone interviews were then conducted with the parents of these affected children. Data on clinical and demographic characteristics, including age of onset, gender, days per week affected, hours per day spent resting, absence from school, comorbidity with depression and a global measure of impairment due to the fatigue, were examined. A narrow definition was defined as a minimum of 6 months disabling fatigue plus at least 4 associated symptoms, which is comparable to the operational criteria for CFS in adults. Broader definitions included those with at least 3 months of disabling fatigue and 4 or more of the associated symptoms and those with simply a minimum of 3 months of disabling fatigue. Groups were mutually exclusive. Results Questionnaires were returned by 1468 families (65% response rate and telephone interviews were completed on 99 of the 129 participants (77% who had experienced fatigue. There were no significant differences in demographic and clinical characteristics or levels of impairment between those who fulfilled the narrower definition and those who fulfilled the broader definitions. The only exception

  10. Mental fatigue induced by prolonged self-regulation does not exacerbate central fatigue during subsequent whole-body endurance exercise.

    Science.gov (United States)

    Pageaux, Benjamin; Marcora, Samuele M; Rozand, Vianney; Lepers, Romuald

    2015-01-01

    It has been shown that the mental fatigue induced by prolonged self-regulation increases perception of effort and reduces performance during subsequent endurance exercise. However, the physiological mechanisms underlying these negative effects of mental fatigue are unclear. The primary aim of this study was to test the hypothesis that mental fatigue exacerbates central fatigue induced by whole-body endurance exercise. Twelve subjects performed 30 min of either an incongruent Stroop task to induce a condition of mental fatigue or a congruent Stroop task (control condition) in a random and counterbalanced order. Both cognitive tasks (CTs) were followed by a whole-body endurance task (ET) consisting of 6 min of cycling exercise at 80% of peak power output measured during a preliminary incremental test. Neuromuscular function of the knee extensors was assessed before and after CT, and after ET. Rating of perceived exertion (RPE) was measured during ET. Both CTs did not induce any decrease in maximal voluntary contraction (MVC) torque (p = 0.194). During ET, mentally fatigued subjects reported higher RPE (mental fatigue 13.9 ± 3.0, control 13.3 ± 3.2, p = 0.044). ET induced a similar decrease in MVC torque (mental fatigue -17 ± 15%, control -15 ± 11%, p = 0.001), maximal voluntary activation level (mental fatigue -6 ± 9%, control -6 ± 7%, p = 0.013) and resting twitch (mental fatigue -30 ± 14%, control -32 ± 10%, p effect of mental fatigue on perception of effort does not reflect a greater development of either central or peripheral fatigue. Consequently, mentally fatigued subjects are still able to perform maximal exercise, but they are experiencing an altered performance during submaximal exercise due to higher-than-normal perception of effort. PMID:25762914

  11. Neuromuscular Fatigue During 200 M Breaststroke

    Directory of Open Access Journals (Sweden)

    Ana Conceição

    2014-03-01

    Full Text Available The aims of this study were: i to analyze activation patterns of four upper limb muscles (duration of the active and non-active phase in each lap of 200m breaststroke, ii quantify neuromuscular fatigue, with kinematics and physiologic assessment. Surface electromyogram was collected for the biceps brachii, deltoid anterior, pectoralis major and triceps brachii of nine male swimmers performing a maximal 200m breaststroke trial. Swimming speed, SL, SR, SI decreased from the 1st to the 3rd lap. SR increased on the 4th lap (35.91 ± 2.99 stroke·min-1. Peak blood lactate was 13.02 ± 1.72 mmol·l-1 three minutes after the maximal trial. The EMG average rectified value (ARV increased at the end of the race for all selected muscles, but the deltoid anterior and pectoralis major in the 1st lap and for biceps brachii, deltoid anterior and triceps brachii in the 4th lap. The mean frequency of the power spectral density (MNF decreased at the 4th lap for all muscles. These findings suggest the occurrence of fatigue at the beginning of the 2nd lap in the 200m breaststroke trial, characterized by changes in kinematic parameters and selective changes in upper limb muscle action. There was a trend towards a non-linear fatigue state.

  12. The Research on Fatigue Driving Detection Algorithm

    Directory of Open Access Journals (Sweden)

    Zhui Lin

    2013-09-01

    Full Text Available Researches on Driver Fatigue Detection System, which aims to ensure the safety of operations and to reduce traffic accidents caused by artificial factors, has been the major research subject in transportation safety. There is an enormous advantage in the method obtaining the driver's image by camera, We propose efficient tracking and detecting algorithm and with an appearance model based on haar-like features, finding out the accuracy and robustness of tracking of eyes movements and the conflict between real-time tracing and accuracy of fatigue detection algorithms systems. First, PERCLOS algorithm is adopted to analyze and determine whether a person is fatigue. Second, AdaBoost algorithm is applied to fast detect and the algorithm is implemented in FPGA. Third, We propose a compressed sample tracking algorithm, which compress samples of image using the sparse measurement matrix and train the classification online. The algorithms runs in real-time and is implemented based on ARM add FPGA platform. Experimental results show that the algorithm has high recognition accuracy and robust performance under real train driving environment, in the case of nonlinear tracking of the human eye, illumination change, multi-scale variations, the driver head movement and pose variation. 

  13. 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.

  14. Biology Notes.

    Science.gov (United States)

    School Science Review, 1982

    1982-01-01

    Presents procedures, exercises, demonstrations, and information on a variety of biology topics including labeling systems, biological indicators of stream pollution, growth of lichens, reproductive capacity of bulbous buttercups, a straw balance to measure transpiration, interaction of fungi, osmosis, and nitrogen fixation and crop production. (DC)

  15. Analysis of Common Fatigue Details in Steel Truss Structures

    Institute of Scientific and Technical Information of China (English)

    张玉玲; 潘际炎; 潘际銮

    2004-01-01

    Generally, the number of fatigue cycles, the range of the repeated stresses, and the type of the structural details are the key factors affecting fatigue in large-scale welded structures. Seven types of structure details were tested using a 2000-kN hydraulic-pressure-servo fatigue machine to imitate fatigue behavior in modern steel-truss-structures fabricated using thicker welded steel plates and integral joint technology. The details included longitudinal edge welds, welded attachment affecting detail, integral joint, and weld repairs on plate edges. The fatigue damage locations show that the stress (normal or shear), the shape, and the location of the weld start and end points are three major factors reducing the fatigue strength. The test results can be used for similar large structures.

  16. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, Jette Andkjær

    1999-01-01

    fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel bridges, may give results that are unconservative. The validity. of the results obtained from Miner's rule will depend on the distribution of the load history......Fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test specimens...... have been carried through. The materials that have been used are either conventional structural steel with a yield stress of f(y) similar to 400-410 MPa or high-strength steel with a yield stress of f(y) similar to 810-840 MPa. The fatigue tests have been carried out using load histories, which...

  17. How to manage fatigue in fibromyalgia: nonpharmacological options.

    Science.gov (United States)

    Ericsson, Anna; Mannerkorpi, Kaisa

    2016-05-01

    The aim of this article is to suggest recommendations for the management of fatigue in fibromyalgia (FM) by reviewing and compiling findings of nonpharmacological treatment for fatigue in patients with FM. The management of fatigue in FM should incorporate regular physical exercise maintained for a longer period of time, which contributes to improved general health and facilitates coping with fatigue and other symptoms. The evidence is still low and the effect of exercise on fatigue in FM needs to be further studied. Patients with FM appear to benefit from general sleep hygiene advice and also need to develop individual strategies to manage the complex factors in everyday life that may be related to fatigue. PMID:27297077

  18. High-temperature fatigue life prediction of turbopump turbine

    International Nuclear Information System (INIS)

    In general, many components are able to be operated under severe thermal conditions. The turbopump turbine is operated under these environments like high temperature and high centrifugal force due to high rotating velocity during operating time. Because these conditions may often cause low-cycle fatigue problem, strain life method is applied to predict low-cycle fatigue life of turbopump turbine. In this paper, strain life method is used to analyze low-cycle fatigue. First of all, to obtain strain history, thermal stress analysis is practised by ABAQUS/CAE. Considering elasticity and plasticity strain's effect, Coffin-Manson' equation is used. S.W.T's method is used to consider the mean stress effect. Low-cycle fatigue analysis is done for turbopump turbine which may have FCL(Fracture Critical Location). MSC.Fatigue is used to analyze low-cycle fatigue life of turbopump turbine.

  19. Corrosion fatigue behavior of carbon steel in drilling fluids

    Energy Technology Data Exchange (ETDEWEB)

    Chaoyang, F.; Jiashen, Z. [Huazhong Univ. of Science and Technology, Wuhan (China)

    1998-08-01

    Corrosion fatigue of carbon steel (CS) in drilling fluids was studied using a self-made rotary bending corrosion fatigue testing apparatus under simulated drilling conditions. Mechanisms of the effects of cyclic stress, chloride (Cl{sup {minus}}), sulfide (S{sup 2{minus}}), and pH of drilling fluids on corrosion fatigue of CS as well as the inhibiting action of the imidazoline inhibitor and oxygen (O{sub 2}) scavenger sodium sulfite (Na{sub 2}SO{sub 3}) on corrosion fatigue were studied. Results showed Cl{sup {minus}} and S{sup 2{minus}} promoted corrosion fatigue crack initiation and growth. Fatigue life was lengthened after reducing subjected stress, increasing the pH of the drilling fluids, or adding the inhibitor and O{sub 2} scavenger.

  20. Environmental fatigue evaluation guide of nuclear power generation facilities

    International Nuclear Information System (INIS)

    This report was environmental fatigue evaluation guide issued in 2007 on the base of the latest data of environmental fatigue testing of materials in simulated reactor coolant environments of nuclear power generation facilities obtained until March 2007. Proposal of equation to evaluate environmental fatigue life with reference fatigue curve in air at the room temperature and environmental fatigue life correction factor in high-temperature water was provided for carbon steel, low alloy steel, austenitic stainless steel and nickel based alloy. Environmental correction factor was obtained from parameters derived from strain rate and temperature; with additional parameters of dissolved oxygen concentration and sulfur content in case of carbon steel and low alloy steel. Calculation of environmental fatigue life correction factor was made to provide large and simplified one with factor multiplication or simplified methods and also accurate and complicated one with detailed method based on selection of strain rate, temperature and dissolved oxygen. (T. Tanaka)

  1. Probabilistic Analysis of Fatigue Behavior of Induction Hardened Steel

    International Nuclear Information System (INIS)

    This study considers how the fatigue behavior and probabilistic properties of S.a.e. steel are related to its hardness level. S.a.e. steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HIV, C: through hardened material with HIV, D: through hardened material with HIV, and E: surface hardened material with HIV). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HIV. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis

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

    Science.gov (United States)

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

    2006-08-01

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

  3. High-Strength Bolt Corrosion Fatigue Life Model and Application

    Directory of Open Access Journals (Sweden)

    Wang Hui-li

    2014-01-01

    Full Text Available The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

  4. Indoor mobility-related fatigue and muscle strength in nonagenarians

    DEFF Research Database (Denmark)

    Mänty, Minna; Ekmann, Anette; Thinggaard, Mikael;

    2014-01-01

    strength decline in nonagenarians. METHODS: The study is based on a prospective longitudinal study of all Danes born in 1905 and assessed in 1998, 2000 and 2003, and includes 92- to 93-year-old persons who were independent of help in basic indoor mobility at baseline (n = 1,353). Fatigue was assessed at...... baseline and defined as a subjective feeling of fatigue when transferring or walking indoors. The outcome measure, maximum grip strength, was measured at each measurement point. RESULTS: Grip strength declined throughout the study in participants with and without fatigue, but those reporting fatigue had...... significantly (P < .001) lower muscle strength during the entire study period. Longitudinal analyses indicated slightly slower decline in muscle strength among participants with fatigue compared to those without; however, observed selective dropout of participants with fatigue and poor performance at baseline...

  5. Fatigue Defect of Layer Steel Fiber Reinforced Concrete

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    An experimental study is carried out on fatigue defect of layer steel fiber reinforced concrete (LSFRC). Based on experimental data,the various relation curves are given corresponding to different stress levels 0.9, 0.85, and 0.8. Furthermore, the fatigue defect degree is defined, and the strain-cycle ratio equations and defect-cycle ratio equations with the correlation coefficients very close to 1, are regressed in terms of the cubic polynomial,of which the fittings are preferable.In addition,the results show that the fatigue defect of LSFRC presents three-phase development regularity too.And in comparison with the plain concrete,the third phase of the fatigue defect of LSFRC is longer, therefore the fatigue failure of LSFRC is more ductile.The mechanism of the fatigue defect is discussed too.

  6. HIGH CYCLE FATIGUE PROPERTIES OF NICKEL-BASE ALLOY 718

    Institute of Scientific and Technical Information of China (English)

    K.Kobayashi; K.Yamaguchi; M.Hayakawa; M.Kimura

    2004-01-01

    The fatigue properties of nickel-base Alloy 718 with fine- and grain-coarse grains were investigated. In the fine-grain alloy, the fatigue strength normalized by the tensile strengtn was 0.51 at 107 cycles. In contrast, the fatigue strength of the coarse-grain alloy was 0.32 at the same cycles, although the fatigue strengths in the range from 103to 105 cycles are the same for both alloys. The fracture appearances fatigued at around 106 cycles showed internal fractures originating from the flat facets of austenite grains for both alloys. The difference in fatigue strength at 107 cycles between the fine- and coarse-grain alloys could be explained in terms of the sizes of the facets from which the fractures originated.

  7. Effect of ageing on fatigue properties of asphalt

    Institute of Scientific and Technical Information of China (English)

    王佶; 庞凌; 吴少鹏; 刘全涛; 陈筝

    2008-01-01

    The fatigue properties of asphalts were investigated after various laboratory simulation ageing tests and outdoor natural exposure ultraviolet radiation ageing,by dynamic shear rheometer(DSR) time sweep fatigue test in constant strain model and a new type of specimen which was introduced to avoid the problem of adhesion failure between rotor and asphalt binder.The results show that outdoor natural exposure ageing(NEA) causes the decrease of retained fatigue life distinctly,and photodegradation caused by outdoor NEA of 1 250 μm thin films asphalt for three months,is found to be severer than pressure ageing vessel(PAV) with respects to retained fatigue life.The effect of photodegradation increases as the time of outdoor NEA increases.DSR time sweep fatigue test in constant strain indicates that the aged styrene-butadiene-styrene(SBS) modified asphalt still displays better fatigue properties than the corresponding base asphalt after ageing.

  8. Improvement Fatigue Performance of Threaded Drillstring Connections by Cold Rolling

    OpenAIRE

    Kristoffersen, Steinar

    2002-01-01

    The research work presented in this thesis is concerned with analytical, numerical and experimental studies of the effect of cold rolling on the fatigue behaviour of threaded drillstring connections.A comprehensive literature study is made of the various effects on the fatigue behaviour of residual stresses introduced by mechanical deformation of notched components. Some of the effects studied are cyclic hardening behaviour after prestraining, cyclic creep, fatigue initiation in prestrained m...

  9. Relaxation Acupressure Reduces Persistent Cancer-Related Fatigue

    OpenAIRE

    Zick, Suzanna M; Sara Alrawi; Gary Merel; Brodie Burris; Ananda Sen; Amie Litzinger; Harris, Richard E.

    2010-01-01

    Persistent cancer-related fatigue (PCRF) is a symptom experienced by many cancer survivors. Acupressure offers a potential treatment for PCRF. We investigated if acupressure treatments with opposing actions would result in differential effects on fatigue and examined the effect of different “doses” of acupressure on fatigue. We performed a trial of acupressure in cancer survivors experiencing moderate to severe PCRF. Participants were randomized to one of three treatment groups: relaxation ac...

  10. Mechanisms of extrusion and intrusion formation in fatigued crystalline materials

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Man, Jiří

    2014-01-01

    Roč. 596, FEB (2014), s. 15-24. ISSN 0921-5093 R&D Projects: GA ČR(CZ) GAP108/10/2371; GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : Fatigue * Extrusion * Intrusion * Persistent slip band * Fatigue crack initiation Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.567, year: 2014

  11. Dopaminergic involvement during mental fatigue in health and cocaine addiction

    OpenAIRE

    Moeller, S J; Tomasi, D; Honorio, J; Volkow, N.D.; Goldstein, R.Z.

    2012-01-01

    Dopamine modulates executive function, including sustaining cognitive control during mental fatigue. Using event-related functional magnetic resonance imaging (fMRI) during the color-word Stroop task, we aimed to model mental fatigue with repeated task exposures in 33 cocaine abusers and 20 healthy controls. During such mental fatigue (indicated by increased errors, and decreased post-error slowing and dorsal anterior cingulate response to error as a function of time-on-task), healthy individ...

  12. Relation between constraint and fatigue crack growth rate

    Czech Academy of Sciences Publication Activity Database

    Hutař, Pavel; Knésl, Zdeněk

    Atlanta : Elsevier, 2006, s. 1-9. [Fatigue 2006. Atlanta (US), 14.05.2006-19.05.2006] R&D Projects: GA ČR GA101/03/0331; GA ČR GP106/06/P239 Institutional research plan: CEZ:AV0Z20410507 Keywords : constraint * T-stress * high cycle fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics

  13. Table Tennis Sports Fatigue Recovery and Dietary Improvement

    OpenAIRE

    Dongyang Tang

    2015-01-01

    The study is explaining briefly about the supplement for the physical fatigue during the process of the movement, putting forward the effective recovery means for the fatigue caused by physical fitness through the principle of physical fitness, so that the exercise fatigue can be quickly recovered and people can have scientific physical exercise and fitness. Table tennis game is a non-cyclical sports item, with the characteristics of high intensity motion, high density, long time, fierce conf...

  14. DIMINISHED FATIGUE AT REDUCED MUSCLE LENGTH IN HUMAN SKELETAL MUSCLE

    OpenAIRE

    Lee, Samuel C. K.; Braim, Anthony; Becker, Cara N.; Prosser, Laura A.; Tokay, Ann M.; Binder-Macleod, Stuart A.

    2007-01-01

    Understanding muscle fatigue properties at different muscle lengths is essential to improve electrical stimulation applications in which impaired muscle is activated to produce function or to serve as an orthotic assist. This study examined the effects of muscle length on fatigue in human quadriceps muscle. Twelve healthy subjects were tested at short and long muscle lengths (15° and 90° of knee flexion, respectively) before and after a fatigue-producing protocol using low-, high-, and variab...

  15. Muscle fatigue degrades force sense at the ankle joint.

    OpenAIRE

    Vuillerme, Nicolas; Boisgontier, Matthieu

    2008-01-01

    To investigate the effects of muscle fatigue on force sense at the ankle joint, 10 young healthy adults were asked to perform an isometric contra-lateral force ankle-matching task in two experimental conditions of: (1) no-fatigue and (2) fatigue of the plantar-flexor muscles. Measures of the overall accuracy and the variability of the force matching performances were determined using the absolute error and the variable error, respectively. Results showed less accurate and less consistent forc...

  16. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  17. Chicken Essence Improves Exercise Performance and Ameliorates Physical Fatigue

    OpenAIRE

    Wen-Ching Huang; Ching-I Lin; Chien-Chao Chiu; Yi-Ting Lin; Wei-Kai Huang; Hui-Yu Huang; Chi-Chang Huang

    2014-01-01

    Chicken essence (CE) is a liquid nutritional supplement made from cooking whole chickens. In traditional Chinese medicine, CE is used to support health, promote healing, increase metabolism, and relieve fatigue. However, few studies have examined the effect of CE on exercise performance and physical fatigue. We aimed to evaluate the potential beneficial effects of CE on fatigue and ergogenic functions following physical challenge in mice. Male ICR mice were divided into four groups to receiv...

  18. Wooden Bridges - Phase 2, Subproject 2.3 Fatigue

    DEFF Research Database (Denmark)

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

    1999-01-01

    The report presents preliminary results on fatigue of wood subjected to tension perpendicular to the grain at a moisture content around 12% and 17%. The main result of the paper concerns the frequency dependency of the fatigue strength. At present it is concluded that fatigue in tension perpendic...... perpendicular to the grain can be time dependent as well as time independent depending on stress level and moisture content....

  19. Influence of Fatigue in Neuromuscular Control of Spinal Stability

    OpenAIRE

    Granata, Kevin P.; Slota, Greg P.; Wilson, Sara E.

    2004-01-01

    Lifting-induced fatigue may influence neuromuscular control of spinal stability. Stability is primarily controlled by muscle recruitment, active muscle stiffness, and reflex response. Fatigue has been observed to affect each of these neuromuscular parameters and may therefore affect spinal stability. A biomechanical model of spinal stability was implemented to evaluate the effects of fatigue on spinal stability. The model included a 6-degree-of-freedom representation of the spine controlled b...

  20. Reducing Patient Barriers to Pain and Fatigue Management

    OpenAIRE

    Borneman, Tami; Koczywas, Marianna; Sun, Virginia; Piper, Barbara F.; Uman, Gwen; Ferrell, Betty

    2010-01-01

    Pain and fatigue are recognized as critical symptoms that impact quality of life (QOL) for cancer patients. The barriers to pain and fatigue relief have been classified into three categories: patient, professional and system barriers. The overall objective of this trial is to test the effects of the “Passport to Comfort” intervention on reducing barriers to pain and fatigue management for ambulatory care cancer patients. This intervention demonstrates innovation by translating the evidence-ba...

  1. [On fatigue bending strength of PMMA-specimen (author's transl)].

    Science.gov (United States)

    Rojczyk, M; Rojczyk-Pflüger, J

    1980-01-01

    The fatigue response of PMMA-specimen was tested under cyclic bending of 1.5 Hz in a particularly designed testing device. Specimen were tested that a "Wöhler" curve and the corresponding fatigue strength could be evaluated. The fatigue strength was reached after a comparatively short time and ranged in the order of 33 per cent of static breaking strength. PMID:7447658

  2. Cognitive impairment in patients with chronic fatigue: a preliminary study.

    OpenAIRE

    McDonald, E; Cope, H; David, A

    1993-01-01

    Subjective impairment of memory and concentration is a frequent complaint in sufferers from chronic fatigue. To study this, 65 general practice attenders identified as having chronic fatigue were administered a structured psychiatric interview and a brief screening battery of cognitive tests. Subjective cognitive impairment was strongly related to psychiatric disorder, especially depressed mood, but not fatigue, anxiety, or objective performance. Simple tests of attention and concentration sh...

  3. Mixed-Mode Fatigue Disbond on Metallic Bonded Joints

    OpenAIRE

    Bürger, D.B.

    2015-01-01

    Aerospace structures have been long dealing with the safety versus weight issue. Lighter airplanes are cheaper to operate, however, they may face a safety issue because of the reduced fatigue life. Consequently, a heavier/safer structure is designed. Adhesive bonding is a joining technique that offers potential for improvement in the fatigue behavior of a structure, resulting in reduced weight. However, predicting the fatigue behavior of a bonded joint for its use in a damage tolerance design...

  4. Experimental methods for the characterization of fatigue in microstructures

    OpenAIRE

    G. De Pasquale; A. Somà

    2013-01-01

    The mechanical fatigue behavior of gold microbeams is analyzed. Dedicated devices have been designed and built able to produce alternate loading on gold specimens; the electrostatic actuation is used as driving force. Gold beams are tested under both bending and tensile alternate loadings. Results were used to plot S-N curves and fatigue Goodman-Smith diagram in order to estimate the fatigue limit of the material in presence of mean and alternate stress conditions. The surface topography evol...

  5. Fatigue in asymmetric-field-driven ferroelectric thin films

    International Nuclear Information System (INIS)

    The polarization fatigue problems in asymmetric-field-driven ferroelectric thin films is investigated in present Letter. The refreshment of fatigue induced by the application of asymmetric voltage to the top and bottom electrodes is modeled by asymmetric Schottky voltage barrier of a quantum well structure. The fatigue behavior under various asymmetric driving voltages and asymmetric driving pulses have been studied. Theoretical calculations are shown to be in agreement with experimental results

  6. Investigating Driver Fatigue versus Alertness Using the Granger Causality Network

    OpenAIRE

    Wanzeng Kong; Weicheng Lin; Fabio Babiloni; Sanqing Hu; Gianluca Borghini

    2015-01-01

    Driving fatigue has been identified as one of the main factors affecting drivers’ safety. The aim of this study was to analyze drivers’ different mental states, such as alertness and drowsiness, and find out a neurometric indicator able to detect drivers’ fatigue level in terms of brain networks. Twelve young, healthy subjects were recruited to take part in a driver fatigue experiment under different simulated driving conditions. The Electroencephalogram (EEG) signals of the subjects were rec...

  7. Design of a fretting fatigue test rig with compliant springs

    OpenAIRE

    De Pauw, Jan; DE BAETS, PATRICK; De Waele, Wim; Hojjati Talemi, Reza

    2013-01-01

    Fretting is a small amplitude oscillatory movement which occurs between contacting bodies who are subjected to cyclic loading or vibrations. In the contact area arise stresses -normal and tangential- causing stress concentrations and surface degradation. Fretting in combination with ordinary fatigue will reduce the plain fatigue lifetime due to the additional stresses and surface degradation. Applications susceptible to fretting fatigue are for instance connections techniques. By nature they ...

  8. Forecasting method of fatigue life test data for metal materials

    Institute of Scientific and Technical Information of China (English)

    张怀亮; 邱显焱; 谭冠军

    2001-01-01

    GM(1, 1) model of grey system theory is used to forecast fatigue life test data for metal materials. The method can reduce test time and save test cost, and reliability indexes of metal materials can be obtained quickly. The results of an example show that grey system theory has a high precision for forecasting fatigue life test data for metal materials. A valuable method is put forward, which can effectively reduce the fatigue life test time for metal materials.

  9. Fatigue in Patients with Parkinson’s Disease

    OpenAIRE

    Kazuo Abe; Mayako Takanashi; Takehiko Yanagihara

    2000-01-01

    Purpose: Fatigue is a complaint frequently encountered among patients with Parkinson’s disease (PD), however, the pathophysiological mechanism remains unclear. Methods: We evaluated fatigue in 26 patients clinically diagnosed to have PD (16 men, 10 women) and age- and sex- matched 26 controls (16 men, 10 women) without neurological deficits by using a fatigue scale. In addition to neurological and neuropsychological examinations, all patients underwent MRI and SPECT using 99mTc-HMPAO. Results...

  10. Fatigue crack initiation — the role of point defects

    Czech Academy of Sciences Publication Activity Database

    Polák, Jaroslav; Man, Jiří

    Brno : Ústav fyziky materiálů AV ČR, v. v. i., 2012, s. 48-55. ISBN 978-80-87434-05-5. [ International Colloquim Mechanical Fatigue of Materials - ICMFM /16./. Brno (CZ), 24.09.2012-26.09.2012] R&D Projects: GA ČR GAP108/10/2371 Institutional support: RVO:68081723 Keywords : fatigue * crack initiation * intrusion * extrusion Subject RIV: JL - Materials Fatigue, Friction Mechanics

  11. High temperature low cycle biaxial fatigue of two steels

    International Nuclear Information System (INIS)

    Biaxial low cycle fatigue tests at various temperatures and strain rates were performed on 1% Cr-Mo-V steel and AISI 316 stainless steel under combined torsional and axial loads. A correlation for fatigue strength has been derived, and it is also shown that if the Gough ellipse quadrant criterion is rephrased in terms of strain amplitudes, it may be used as a safe design rule for ductile metals in both the low and high cycle fatigue regimes. (author)

  12. Fatigue test of epoxide resin at low temperatures

    International Nuclear Information System (INIS)

    The search for experimental data on LHeT is presented, with an examination of the temperature dependence on fatigue properties, Also given are reference data for magnet design. The sample, flexural and fatigue tests are described. The recorded discussion is followed by four conclusions based on the fact that a cured Bisphenol-A resin was subjected to a repeating load and was investigated for fatigue properties at cryogenic temperatures

  13. Analysis of fatigue life for tube trailer cylinders

    OpenAIRE

    Xinqi YU; Bolong SONG; Zhang, Zhao; Qinggang LIU

    2015-01-01

    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 dist...

  14. Psychometric properties of fatigue severity and fatigue impact scales in postpolio patients.

    Science.gov (United States)

    Oncu, Julide; Atamaz, Funda; Durmaz, Berrin; On, Arzu

    2013-12-01

    We evaluate the reliability, validity, and responsiveness of the Fatigue Severity Scale (FSS) and the Fatigue Impact Scale (FIS) and to determine whether these scales are potentially applicable for measuring fatigue in postpolio patients (PPS). After the Turkish adaptation of FSS and FIS using a forward-backward procedure, the scales were administered to 48 PPS patients without additional health problems that may induce fatigue. Reliability studies were carried out by determination of intraclass correlation coefficient and internal consistency by the Cronbach-α coefficient. Validity was tested by within-scale analyses and analyses against the external criteria including convergent validity and discriminant validity. Correlations with the Notthingham Health Profile (NHP), fatigue, pain and cramp severity (visual analog scale), and manual muscle testing were performed. Sensitivity to changes was determined by standardized response mean values. All patients completed scales, suggesting their satisfactory acceptance. Reliability studies were satisfactory, with higher Cronbach-α values and intraclass correlation coefficients than 0.80. The FSS score was correlated moderately with visual analog scale-fatigue (r=0.41) and the NHP-energy dimension (r=0.29). All FIS scores except cognitive scores were moderately related to the NHP-social isolation score (r=0.40, 0.37, and 0.43 for FIS-physical, social, and total scores, respectively). There was also a significant correlation between the FIS-physical score and the NHP-energy score (r=0.31). On the basis of the standardized response mean values, response to treatment for these two questionnaires was satisfactory (P=0.00). The Turkish versions of FSS and FIS were reliable, sensitive to clinical changes, and also well accepted by patients with PPS. Although they had somewhat satisfactory convergent validity, the absence of strong correlations did not support the validity entirely. PMID:23903028

  15. Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

    Science.gov (United States)

    Safaei, Farinaz; Castorena, Cassie; Kim, Y. Richard

    2016-04-01

    Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder's contribution to mixture fatigue and pavement fatigue cracking performance.

  16. Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

    Science.gov (United States)

    Safaei, Farinaz; Castorena, Cassie; Kim, Y. Richard

    2016-08-01

    Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder's contribution to mixture fatigue and pavement fatigue cracking performance.

  17. Fatigue reliability and calibration of fatigue design factors of wave energy converters

    DEFF Research Database (Denmark)

    Ambühl, Simon; Ferri, Francesco; Kofoed, Jens Peter;

    2015-01-01

    Fatigue Factors (DFF), for steel substructures of WECs. A reliability-based approach is used and a probabilistic model including design and limit state equation is established. For modelling fatigue, the SN-curve approach as well as fracture mechanics are used. Furthermore, the influence of inspections is...... considered in order to extend and maintain a certain target safety level. This paper uses the Wavestar prototype located at Hanstholm (DK) as case study in order to calibrate FDFs for welded and bolted details in steel structures of an offshore bottom-fixed WEC with hydraulic floaters....

  18. Participant attributions for global change ratings in unexplained chronic fatigue and chronic fatigue syndrome.

    Science.gov (United States)

    Friedberg, Fred; Coronel, Janna; Seva, Viktoria; Adamowicz, Jenna L; Napoli, Anthony

    2016-05-01

    The purpose of this mixed methods study was to identify participants' attributions for their global impression of change ratings in a behavioral intervention for unexplained chronic fatigue and chronic fatigue syndrome. At 3-month follow-up, participants (N = 67) were asked "Why do you think you are (improved, unchanged, worse)?" Improved patients pointed to specific behavioral changes, unchanged patients referred to a lack of change in lifestyle, and worsened patients invoked stress and/or specific life events. Identifying patient perceptions of behaviors associated with patient global impression of change-rated improvement and non-improvement may assist in developing more effective management strategies in clinical care. PMID:24913009

  19. Damage tolerance design for thermal fatigue loading. Crack growth behavior under thermal fatigue loading

    International Nuclear Information System (INIS)

    Thermal fatigue is one of critical problems in nuclear power plants. To prevent crack initiation, JSME has issued a guideline for design. In this study, the feasibility of incorporating crack growth analysis into the design and integrity evaluation was investigated. It was shown that the steep stress gradient near the surface significantly reduced the stress intensity factor of deep cracks. It is concluded that, under thermal fatigue loading, the cracks that are detected in the in-service inspection have already been arrested if they do not penetrate the wall thickness. The crack arrest scenario is a reasonable method of assessing the integrity of cracked components. (author)

  20. Quantum Biology

    Directory of Open Access Journals (Sweden)

    Alessandro Sergi

    2009-06-01

    Full Text Available A critical assessment of the recent developmentsof molecular biology is presented.The thesis that they do not lead to a conceptualunderstanding of life and biological systems is defended.Maturana and Varela's concept of autopoiesis is briefly sketchedand its logical circularity avoided by postulatingthe existence of underlying living processes,entailing amplification from the microscopic to the macroscopic scale,with increasing complexity in the passage from one scale to the other.Following such a line of thought, the currently accepted model of condensed matter, which is based on electrostatics and short-ranged forces,is criticized. It is suggested that the correct interpretationof quantum dispersion forces (van der Waals, hydrogen bonding, and so onas quantum coherence effects hints at the necessity of includinglong-ranged forces (or mechanisms for them incondensed matter theories of biological processes.Some quantum effects in biology are reviewedand quantum mechanics is acknowledged as conceptually important to biology since withoutit most (if not all of the biological structuresand signalling processes would not even exist. Moreover, it is suggested that long-rangequantum coherent dynamics, including electron polarization,may be invoked to explain signal amplificationprocess in biological systems in general.