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

    : 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...... and 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...... quality and extracted data. Where appropriate, we pooled data in meta-analyses using a random-effects model. MAIN RESULTS: We identified 32 studies for inclusion in this current review. Twenty studies evaluated five anti-tumour necrosis factor (anti-TNF) biologic agents (adalimumab, certolizumab...

  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)

    Bennett RM. Fibromyalgia, chronic fatigue syndrome, and myofascial pain. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 274. Thames TA, Karrh ...

  4. 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 ...

  5. 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 ...

  6. Fatigue management in the workplace

    Directory of Open Access Journals (Sweden)

    Khosro Sadeghniiat-Haghighi

    2015-01-01

    Full Text Available 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 fatigue. It can be more investigated in a new field of sleep medicine called occupational sleep medicine. Occupational sleep medicine is concerned with maintaining best productivity and safety in the industrial settings. The fatigue risk management system (FRMS is a comprehensive approach that is based on applying scientific evidence of sleep knowledge to manage workers fatigue. It is developing rapidly in the highly safety demand jobs; especially truck drivers, pilots, and power plant workers. The objective of this review is to explain about fatigue in the workplace with emphasis on its association work performance and errors/accidents. Also, we discussed about different methods of fatigue measurement and management.

  7. 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...

  8. 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)

  9. 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.

  10. Search Fatigue

    OpenAIRE

    Bruce Ian Carlin; Florian Ederer

    2012-01-01

    Consumer search is not only costly but also tiring. We characterize the intertemporal effects that search fatigue has on oligopoly prices, product proliferation, and the provision of consumer assistance (i.e., advice). These effects vary based on whether search is all-or-nothing or sequential in nature, whether learning takes place, and whether consumers exhibit brand loyalty. We perform welfare analysis and highlight the novel empirical implications that our analysis generates.

  11. 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 ...

  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. 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.

  14. [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-

  15. 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.

  16. 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...

  17. 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 ...

  18. 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 ...

  19. 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...

  20. [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

  1. 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.

  2. Fatigue - corrosion of endoprosthesis titanium alloys.

    Science.gov (United States)

    Cornet, A; Muster, D; Jaeger, J H

    1979-01-01

    Commercial total hip prostheses often show certain metallurgical faults (porosities, coarse grains, growth dendrites, carbide networks). In order to investigate more accurately the role played by these different parameters in prostheses failure we performed a large number of systematic corrosion, fatigue and fatigue - corrosion tests on these materials and on commercial total hip prostheses. Ultimate strengthes seem to be reached for cast cobalt alloys, whereas titanium alloys, such as Ta 6 V, present very high fatigue limit under corrosion. Thus, rotative bending fatigue - corrosion tests in biological environment provide values about 50 DaN/mm2. This value, is nevertheless appreciably higher than those obtained with stellites and stainless steel. Titanium alloys, because of their mechanical performances, their weak Young's modulus (11000 DaN/mm2) and their relative lightness (4.5. g/cm3), which are associated with a good biocompatibility, seem very promising for permanent implants realisation.

  3. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

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

    1996-01-01

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

  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. 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

  6. Clinical neurophysiology of fatigue.

    Science.gov (United States)

    Zwarts, M J; Bleijenberg, G; van Engelen, B G M

    2008-01-01

    Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic disease has been established. If certain criteria are met, chronic fatigue syndrome can be diagnosed. The 4-item Abbreviated Fatigue Questionnaire allows the extent of the experienced fatigue to be assessed with a high degree of reliability and validity. Physiological fatigue has been well defined and originates in both the peripheral and central nervous system. The condition can be assessed by combining force and surface-EMG measurements (including frequency analyses and muscle-fibre conduction estimations), twitch interpolation, magnetic stimulation of the motor cortex and analysis of changes in the readiness potential. Fatigue is a well-known phenomenon in both central and peripheral neurological disorders. Examples of the former conditions are multiple sclerosis, Parkinson's disease and stroke. Although it seems to be a universal symptom of many brain disorders, the unique characteristics of the concomitant fatigue also point to a specific relationship with several of these syndromes. As regards neuromuscular disorders, fatigue has been reported in patients with post-polio syndrome, myasthenia gravis, Guillain-Barré syndrome, facioscapulohumeral dystrophy, myotonic dystrophy and hereditary motor and sensory neuropathy type-I. More than 60% of all neuromuscular patients suffer from severe fatigue, a prevalence resembling that of patients with MS. Except for several rare myopathies with specific metabolic derangements leading to exercise-induced muscle fatigue, most studies have not identified a prominent peripheral cause for the fatigue in this population. In contrast, the central activation of the diseased neuromuscular system is generally found to be suboptimal. The

  7. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

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

  8. 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

  9. 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...

  10. Examining fatigue in COPD

    DEFF Research Database (Denmark)

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

    2012-01-01

    ABSTRACT: INTRODUCTION: Fatigue is a disruptive symptom that inhibits normal functional performance of COPD patients in daily activities. The availability of a short, simple, reliable and valid scale would improve assessment of the characteristics and influence of fatigue in COPD. METHODS...... were less able to capture fatigue characteristics in COPD and were deleted. PCA was applied to the remaining 9 items of the modified FACIT-F and resulted in three interpretable dimensions: i) general (5 items); ii) functional ability (2 items); and iii) psychosocial fatigue (2 items). The modified...... 7) and mMRC dyspnoea scores (0.48 and 0.47), (p =...

  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. Clinical neurophysiology of fatigue.

    NARCIS (Netherlands)

    Zwarts, M.J.; Bleijenberg, G.; Engelen, B.G.M. van

    2008-01-01

    Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic dis

  13. 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.

  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 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)

  16. 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.

  17. Hyperthermia and fatigue

    DEFF Research Database (Denmark)

    Nybo, Lars

    2008-01-01

    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...... 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...... of the dopaminergic system, but may primarily relate to inhibitory signals from the hypothalamus arising secondary to an increase in brain temperature. Fatigue is an integrated phenomenon, and psychological factors, including the anticipation of fatigue, should not be neglected and the interaction between central...

  18. 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 ...

  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. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    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......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...

  1. Chronic fatigue syndrome

    Science.gov (United States)

    Bennett RM. Fibromyalgia, chronic fatigue syndrome, and myofascial pain. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 274. Engleberg NC. Chronic ...

  2. 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...

  3. Thermal fatigue of beryllium

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-09-01

    Thermal fatigue life of S65c beryllium castellated to a geometry 6 x 6 x (8-10)mm deep has been tested for steady heat fluxes of 3 MW/m{sup 2} to 5 MW/m{sup 2} and under pulsed heat fluxes (10-20 MW/m{sup 2}) for which the time averaged heat flux is 5 MW/m{sup 2}. These tests were carried out in the JET neutral beam test facility A test sequence with peak surface temperatures {le} 600{degrees}C produced no visible fatigue cracks. In the second series of tests, with T{sub max} {le} 750{degrees}C evidence for fatigue appeared after a minimum of 1350 stress cycles. These fatigue data are discussed in view of the observed lack of thermal fatigue in JET plasma operations with beryllium PFC. JET experience with S65b and S65c is reviewed; recent operations with {Phi} = 25 MW/m{sup 2} and sustained melting/resolidification are also presented. The need for a failure criterion for finite element analyses of Be PFC lifetimes is discussed.

  4. Modafinil May Alleviate Poststroke Fatigue

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  5. 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 ...

  6. 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.)

  7. 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...

  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 of stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Solin, J. (VTT Technical Research Centre of Finland, Espoo (Finland))

    2010-05-15

    The 2009b update of ASME III introduces a new set of fatigue design curves. The new curve for austenitic stainless steels is exactly matching with the one endorsed in 2007 by the US NRC for new designs only. This has a notable effect in usage factor calculation at strain amplitudes below 0.5 %. However, experimental results clearly demonstrate that a new air curve would not be needed for the studied stainless steel grades. Our current results suggest arguments for use of stabilized stainless steels in NPP piping components, where high cycle fatigue (epsilon{sub a}<=0.5%) is a concern. (orig.)

  10. 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...

  11. 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.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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…

  18. Self-regulation, physical activity and unexplained chronic fatigue : from determinants to interventions

    NARCIS (Netherlands)

    Moreira Marques, Marta

    2015-01-01

    Unexplained Chronic Fatigue (CF) is of unknown aetiology, but research suggests a multifactorial nature in which biological/physical, psychological and social fators interact. Treatment approaches for CF target mainly perpetuating factors of fatigue chronicity, such as lack of physical activity. Thi

  19. Determinants of fatigue and stress

    Directory of Open Access Journals (Sweden)

    Brähler Elmar

    2011-07-01

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

  20. 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

  1. Chronic fatigue and chronic fatigue syndrome: shifting boundaries and attributions.

    Science.gov (United States)

    Lloyd, A R

    1998-09-28

    The subjective symptom of "fatigue" is one of the most widespread in the general population and is a major source of healthcare utilization. Prolonged fatigue is often associated with neuropsychological and musculoskeletal symptoms that form the basis of several syndromal diagnoses including chronic fatigue syndrome, fibromyalgia, and neurasthenia, and is clearly not simply the result of a lack of force generation from the muscle. Current epidemiologic research in this area relies predominantly on self-report data to document the prevalence and associations of chronic fatigue. Of necessity, this subjective data source gives rise to uncertain diagnostic boundaries and consequent divergent epidemiologic, clinical, and pathophysiologic research findings. This review will highlight the impact of the case definition and ascertainment methods on the varying prevalence estimates of chronic fatigue syndrome and patterns of reported psychological comorbidty. It will also evaluate the evidence for a true postinfective fatigue syndrome.

  2. Fatigue syndrome in sarcoidosis.

    Science.gov (United States)

    Górski, Witold; Piotrowski, Wojciech J

    2016-01-01

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

  3. 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

  4. 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

  5. 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.

  6. 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...

  7. 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...

  8. 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.

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

    NARCIS (Netherlands)

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

    2007-01-01

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

  10. [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

  11. Fatigue tests on aluminium bridges

    NARCIS (Netherlands)

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

    2005-01-01

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

  12. Fatigue tests on aluminium bridges

    NARCIS (Netherlands)

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

    2004-01-01

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

  13. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    , 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...... propagation stage. The consequences of this behaviour on the fatigue reliability are discussed....

  14. 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....

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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...

  6. 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.

  7. 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...

  8. MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

    Directory of Open Access Journals (Sweden)

    Grzegorz SZALA

    2014-03-01

    Full Text Available In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF, high cycle fatigue (HCF, fatigue limit (FL and giga cycle fatigue (GCF appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys.

  9. 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

  10. 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.

  11. 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.

  12. 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...

  13. Fatigue test machine

    Science.gov (United States)

    Jones, D. I. G.

    1985-12-01

    This invention relates to an apparatus for testing materials under combined static and dynamic loads. Materials used in rotating components of, for example, jet engines are subjected to unusually severe environmental conditions during their operational lifetimes. Components such as disks and blades are subjected to high temperature excursions, high levels of 'steady' stress from centrifugal loads (low cycle stress), as well as high levels of high frequency 'dynamic' stress from resonant vibration response (high cycle stress). The thermal-mechanical cycling of the component material can lead to initiation and propagation of cracks at voids, defects or scratches. The crack initiation and propagation characteristics of materials used in jet engine components vary widely, according to whether the material is more or less ductile, and depend on temperature, low cycle stress, high cycle stress, frequency, dwell time, local atmospheric conditions and many other parameters. This abstract discloses fatigue testing machine for testing materials under combined static and dynamic loads. The mach ine comprises a right circular ring, a pair of specimen clamps adapted for slidably fitting into diametrically opposed openings in the ring, a support cradle for the ring and a shaker. The clamps comprises means for applying a static load to a specimen clamped therebetween.

  14. 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.

  15. 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.

  16. Sleep complaints and fatigue of airline pilots.

    Science.gov (United States)

    Reis, Cátia; Mestre, Catarina; Canhão, Helena; Gradwell, David; Paiva, Teresa

    2016-01-01

    This work aimed to determine daytime sleepiness and sleep complaints prevalence and the corresponding influence on perceived fatigue and to evaluate the influence of sociodemographic parameters and labour variables on sleep complaints, sleepiness and fatigue. A questionnaire was developed including socio-economic and labour issues and instruments, focused in sleep and fatigue. The response rate was 32% and the final sample had 435 pilots. The prevalence of sleep complaints was 34.9%, daytime sleepiness 59.3% and fatigue 90.6%. The high prevalence of sleep complaints, sleepiness and fatigue was disclosed in pilots, with those who fly short/medium having an added risk of fatigue.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Fatigue and fatigue-related symptoms in patients treated for different causes of hypothyroidism

    NARCIS (Netherlands)

    J.W.K. Louwerens; B.C. Appelhof (Bente); H. Verloop (Herman); M. Medici (Marco); R.P. Peeters (Robin); T.J. Visser (Ton); A. Boelen (Anita); E. Fliers (Eric); J.W.A. Smit (Jan); O.M. Dekkers (Olaf)

    2012-01-01

    textabstractObjective: Research on determinants of well-being in patients on thyroid hormone replacement therapy is warranted, as persistent fatigue-related complaints are common in this population. In this study, we evaluated the impact of different states of hypothyroidism on fatigue and fatigue-r

  3. 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) ...

  4. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  5. 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).

  6. 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.

  7. 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.

  8. 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...

  9. 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...

  10. 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...

  11. 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.

  12. 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

  13. [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

  14. 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.

  15. A potential biomarker for fatigue: Oxidative stress and anti-oxidative activity.

    Science.gov (United States)

    Fukuda, Sanae; Nojima, Junzo; Motoki, Yukari; Yamaguti, Kouzi; Nakatomi, Yasuhito; Okawa, Naoko; Fujiwara, Kazumi; Watanabe, Yasuyoshi; Kuratsune, Hirohiko

    2016-07-01

    We sought to determine whether oxidative stress and anti-oxidative activity could act as biomarkers that discriminate patients with chronic fatigue syndrome (CFS) from healthy volunteers at acute and sub-acute fatigue and resting conditions. We calculated the oxidative stress index (OSI) from reactive oxygen metabolites-derived compounds (d-ROMs) and the biological antioxidant potential (BAP). We determined changes in d-ROMs, BAP, and OSI in acute and sub-acute fatigue in two healthy groups, and compared their values at rest between patients with CFS (diagnosed by Fukuda 1994 criteria) and another group of healthy controls. Following acute fatigue in healthy controls, d-ROMs and OSI increased, and BAP decreased. Although d-ROMs and OSI were significantly higher after sub-acute fatigue, BAP did not decrease. Resting condition yielded higher d-ROMs, higher OSI, and lower BAP in patients with CFS than in healthy volunteers, but lower d-ROMs and OSI when compared with sub-acute controls. BAP values did not significantly differ between patients with CFS and controls in the sub-acute condition. However, values were significantly higher than in the resting condition for controls. Thus, measured of oxidative stress (d-ROMS) and anti-oxidative activity (BAP) might be useful for discriminating acute, sub-acute, and resting fatigue in healthy people from patients with CFS, or for evaluating fatigue levels in healthy people.

  16. 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 ...

  17. Fatigue Reliability of Offshore Wind Turbine Systems

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2012-01-01

    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...... of appropriate partial safety factors / fatigue design factors (FDF) for steel substructures of offshore wind turbines (OWTs). The fatigue life is modeled by the SN approach. Design and limit state equations are established based on the accumulated fatigue damage. The acceptable reliability level for optimal...

  18. "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…

  19. 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

  20. Parallel monostrand stay cable bending fatigue

    DEFF Research Database (Denmark)

    Winkler, Jan Pawel

    This dissertation investigates the bending fatigue response of high-strength steel monostrands and multistrand stay cables to cyclic transverse deformations. Increasing bridge stock numbers and a push for longer cable-supported span lengths have led to an increased number of reported incidents...... of damage and replacement of bridge stay cables due to wind and traffic-induced fatigue. The understanding of fatigue mechanisms in most steel structures is well established. However, in the case of cables composed of steel strands, many important aspects related with bending fatigue remain to be clarified....... The thesis starts with a literature review of the state-of-the-art in the fields of stay cable fatigue testing and cable fatigue resistance. The study helped to systemize the understanding of the fatigue characteristics of bridge cables subjected to cyclic transverse displacements, failure mechanisms...

  1. Titanium in fatigue critical military aircraft structure

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, F.

    1999-07-01

    This paper discusses the effect of fatigue requirements on titanium structure in military aircraft applications, specifically, fighter aircraft. The discussion covers how fatigue affects the design and analysis of detail parts, and how manufacturing processes affect the fatigue performance of titanium structure. Criteria for designing fighter aircraft have evolved from simple strength calculations to extremely complex computer generated analyses involving strength, durability, damage tolerance and fatigue. Fatigue life prediction is an important part of these analyses and dramatically affects the design and weight of fighter aircraft. Manufacturing processes affect fatigue performance both in a positive and negative manner. Designers must allow for the effect of these processes on titanium structure and consider the efficiency and economy of adding processes that increase fatigue life.

  2. Fatigue and Depressive Symptoms in Older People

    DEFF Research Database (Denmark)

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

    2014-01-01

    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......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...... 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 associated...

  3. 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.

  4. A Transcriptional Signature of Fatigue Derived from Patients with Primary Sjögren’s Syndrome

    Science.gov (United States)

    James, Katherine; Al-Ali, Shereen; Tarn, Jessica; Cockell, Simon J.; Gillespie, Colin S.; Hindmarsh, Victoria; Locke, James; Mitchell, Sheryl; Lendrem, Dennis; Bowman, Simon; Price, Elizabeth; Pease, Colin T.; Emery, Paul; Lanyon, Peter; Hunter, John A.; Gupta, Monica; Bombardieri, Michele; Sutcliffe, Nurhan; Pitzalis, Costantino; McLaren, John; Cooper, Annie; Regan, Marian; Giles, Ian; Isenberg, David; Saravanan, Vadivelu; Coady, David; Dasgupta, Bhaskar; McHugh, Neil; Young-Min, Steven; Moots, Robert; Gendi, Nagui; Akil, Mohammed; Griffiths, Bridget; Wipat, Anil; Newton, Julia; Jones, David E.; Isaacs, John; Hallinan, Jennifer; Ng, Wan-Fai

    2015-01-01

    Background 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. Methods 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). Results 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. Conclusions 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. PMID:26694930

  5. Exploratory Cohort Study of Associations between Serum C - Reactive Protein and Fatigue after Stroke.

    Directory of Open Access Journals (Sweden)

    Simiao Wu

    Full Text Available Post-stroke fatigue is a common and distressing problem but little is known about its biological mechanisms. This cohort study was to investigate associations between C-reactive protein (CRP and fatigue after stroke.Patients were assessed at one, six and 12 months after their stroke onset, with the Fatigue Assessment Scale, a case definition of post-stroke fatigue, Hospital Anxiety and Depression Scale, and daily step counts. Blood samples were collected at each assessment and the CRP level was determined by a standard CRP immunoassay. Cross-sectional associations between CRP and fatigue at each time point were determined by Pearson correlation coefficient and independent-samples t-test. Whether CRP levels at one month predict fatigue scores at six and 12 months was explored by multiple linear regression, with anxiety, depression, and daily step counts as covariates.Sixty-five patients (mean age 67 years, 65% men were included: 61 at one month, 49 at six months, and 41 at 12 months. CRP levels and fatigue scores were not associated at one month (p = 0.88 or 12 months (p = 0.56, but weakly associated at six months (r = 0.27, p = 0.04; however, this association was no longer significant (p = 0.14 after controlling for the effects of covariates. The CRP level was not associated with the fulfilment of case definition of post-stroke fatigue at any time points (all p > 0.05. The CRP level at one month was not a significant predictor for fatigue levels at either six months (p = 0.93 or 12 months (p = 0.78.There is insufficient evidence for the association between CRP and PSF in stroke patients. Future studies with larger sample sizes and controlling for potential confounders are needed to investigate whether this association exists.

  6. Exploratory Cohort Study of Associations between Serum C - Reactive Protein and Fatigue after Stroke

    Science.gov (United States)

    Wu, Simiao; Duncan, Fiona; Anderson, Niall H.; Kuppuswamy, Annapoorna; Macloed, Malcolm R.; Mead, Gillian E.

    2015-01-01

    Background and Aim Post-stroke fatigue is a common and distressing problem but little is known about its biological mechanisms. This cohort study was to investigate associations between C-reactive protein (CRP) and fatigue after stroke. Methods Patients were assessed at one, six and 12 months after their stroke onset, with the Fatigue Assessment Scale, a case definition of post-stroke fatigue, Hospital Anxiety and Depression Scale, and daily step counts. Blood samples were collected at each assessment and the CRP level was determined by a standard CRP immunoassay. Cross-sectional associations between CRP and fatigue at each time point were determined by Pearson correlation coefficient and independent-samples t-test. Whether CRP levels at one month predict fatigue scores at six and 12 months was explored by multiple linear regression, with anxiety, depression, and daily step counts as covariates. Results Sixty-five patients (mean age 67 years, 65% men) were included: 61 at one month, 49 at six months, and 41 at 12 months. CRP levels and fatigue scores were not associated at one month (p = 0.88) or 12 months (p = 0.56), but weakly associated at six months (r = 0.27, p = 0.04); however, this association was no longer significant (p = 0.14) after controlling for the effects of covariates. The CRP level was not associated with the fulfilment of case definition of post-stroke fatigue at any time points (all p > 0.05). The CRP level at one month was not a significant predictor for fatigue levels at either six months (p = 0.93) or 12 months (p = 0.78). Conclusions There is insufficient evidence for the association between CRP and PSF in stroke patients. Future studies with larger sample sizes and controlling for potential confounders are needed to investigate whether this association exists. PMID:26599129

  7. 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)

  8. Frequency dependence of fatigue and corrosion fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Marvasti, Mohammad Hassan; Chen, Weixing [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB (Canada); Kania, Richard; Worthingham, Robert [TransCanada Pipelines Limited, Calgary, AB (Canada); Van Boven, Gregory [Spectra Energy Transmission Limited, Vancouver, BC (Canada)

    2010-07-01

    It was in the mid-1980s that stress corrosion cracking (SCC) was first found in near-neutral pH conditions on the TransCanada pipeline system. Since then, there have been many reports of pipeline cracking in Canada in these conditions. The huge quantity of pipelines in Canada and the number of failures have brought great interest in investigation of this cracking. A study was conducted on one X52 pipeline steel. It used compact tension specimens for corrosion fatigue and fatigue tests in air. The following conclusions were drawn: 1) crack growth in near-neutral pH conditions can be explained by a factor, which reflects the combined action of the mechanical driving force and the hydrogen effects; 2) mechanical dormancy can be common when oil and gas pipelines are in operation; 3) hydrogen is a determining factor of crack growth when pipeline steels are exposed to near-neutral pH conditions.

  9. 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...

  10. 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.

  11. 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)

  12. Fatigue in cancer: A review of literature

    Directory of Open Access Journals (Sweden)

    Vijayakumar Narayanan

    2009-01-01

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

  13. Mental fatigue: costs and benefits.

    Science.gov (United States)

    Boksem, Maarten A S; Tops, Mattie

    2008-11-01

    A framework for mental fatigue is proposed, that involves an integrated evaluation of both expected rewards and energetical costs associated with continued performance. Adequate evaluation of predicted rewards and potential risks of actions is essential for successful adaptive behaviour. However, while both rewards and punishments can motivate to engage in activities, both types of motivated behaviour are associated with energetical costs. We will review findings that suggest that the nucleus accumbens, orbitofrontal cortex, amygdala, insula and anterior cingulate cortex are involved evaluating both the potential rewards associated with performing a task, as well as assessing the energetical demands involved in task performance. Behaviour will only proceed if this evaluation turns out favourably towards spending (additional) energy. We propose that this evaluation of predicted rewards and energetical costs is central to the phenomenon of mental fatigue: people will no longer be motivated to engage in task performance when energetical costs are perceived to outweigh predicted rewards.

  14. Rethinking fatigue in Gaucher disease

    OpenAIRE

    Zion, Y. Chen; Pappadopulos, E.; Wajnrajch, M.; Rosenbaum, H.

    2016-01-01

    Background Gaucher disease (GD) is a rare lysosomal storage disease caused by deficiency in the enzyme beta-glucocerebrosidase. Along with visceral, hematologic, and bone manifestations, patients may experience chronic fatigue resulting in functional disability and reduced quality of life. Management of the disease includes therapeutic intervention, supportive therapies, and regular monitoring of all clinically relevant disease signs and symptoms. However, current practice guidelines do not i...

  15. Adults living with heart failure and fatigue

    DEFF Research Database (Denmark)

    Schjødt, Inge; Sommer, Irene; Bjerrum, Merete

    Background Fatigue is one of the most common symptoms reported by patients with heart failure (HF). Fatigue negatively impacts on patients’ everyday life, prognosis and quality of life. No specific cure or effective interventions to alleviate fatigue are available. Over the past decade, qualitative...... 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 synthesise the best available evidence related to the lived experiences and management of fatigue in everyday life in adult patients with stable heart failure to develop effective interventions to support self-care. Specific questions on the patients’ lived experiences included: • How do patients with HF...

  16. 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...... 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...... 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...

  17. 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)

  18. Low cycle fatigue of irradiated LMFBR materials

    Energy Technology Data Exchange (ETDEWEB)

    Blackburn, L D

    1976-01-01

    A review of low cycle fatigue data on irradiated LMFBR materials was conducted and extensive graphical representations of available data are presented. Representative postirradiation tensile properties of annealed 304 and 316 SS are selected and employed in several predictive methods to estimate irradiated material fatigue curves. Experimental fatigue data confirm the use of predictive methods for establishing conservative design curves over the range of service conditions relevant to such CRBRP components as core former, fixed radial shielding, core barrel, lower inlet module and upper internals structures. New experimental data on fatigue curves and creep-fatigue interaction in irradiated 20 percent cold worked (CW) 316 SS and Alloy 718 would support the design of removable radial shielding and upper internals in CRBRP. New experimental information on notched fatigue behavior and cyclic stress-strain curves of all these materials in the irradiated condition could provide significant design data.

  19. EVAPRED - A CODE FOR FATIGUE ANALYSIS OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    Dorin LOZICI-BRÎNZEI

    2010-03-01

    Full Text Available The fatigue can be, in fact, defined as: “failure under a repeated or otherwise varying load, which never reaches a level sufficient to cause failure in a single application”.Physical testing is clearly unrealistic for every design component. In most applications, fatigue-safe life design requires the prediction of the component fatigue life that accounts for predicted service loads and materials. The primary tool for both understanding and being able to predict and avoid fatigue has proven to be the finite element analysis (FEA. Computer-aided engineering (CAE programs use three major methods to determine the total fatigue life: Stress life (SN, Strain life (EN and Fracture Mechanics (FM. FEA can predict stress concentration areas and can help design engineers to predict how long their designs are likely to last before experiencing the onset of fatigue.

  20. 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)

  1. Chronic fatigue syndrome: an approach combining self-management with graded exercise to avoid exacerbations.

    Science.gov (United States)

    Nijs, Jo; Paul, Lorna; Wallman, Karen

    2008-04-01

    Controversy regarding the aetiology and treatment of patients with chronic fatigue syndrome continues among the medical professions. The Cochrane Collaboration advises practitioners to implement graded exercise therapy for patients with chronic fatigue syndrome using cognitive behavioural principles. Conversely, there is evidence that exercise can exacerbate symptoms in chronic fatigue syndrome, if too-vigorous exercise/activity promotes immune dysfunction, which in turn increases symptoms. When designing and implementing an exercise programme for chronic fatigue syndrome it is important to be aware of both of these seemingly opposing viewpoints in order to deliver a programme with no detrimental effects on the pathophysiology of the condition. Using evidence from both the biological and clinical sciences, this paper explains that graded exercise therapy for people with chronic fatigue syndrome can be undertaken safely with no detrimental effects on the immune system. Exercise programmes should be designed to cater for individual physical capabilities and should take into account the fluctuating nature of symptoms. In line with cognitive behaviourally and graded exercise-based strategies, self-management for people with chronic fatigue syndrome involves encouraging patients to pace their activities and respect their physical and mental limitations, with the ultimate aim of improving their everyday functioning. PMID:18382818

  2. 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...

  3. 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...

  4. 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...

  5. 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.

  6. 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...... the interpretive power of the MFI-20, allowing for the identification of the most optimal scales. Poorly performing items were more easily identified, and person ability was assessed more accurately....

  7. 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.

  8. Sleep complaints and fatigue of airline pilots

    OpenAIRE

    Reis, Cátia; Mestre, Catarina; Canhão, Helena; Gradwell, David; Paiva, Teresa

    2016-01-01

    This work aimed to determine daytime sleepiness and sleep complaints prevalence and the corresponding influence on perceived fatigue and to evaluate the influence of sociodemographic parameters and labour variables on sleep complaints, sleepiness and fatigue. A questionnaire was developed including socio-economic and labour issues and instruments, focused in sleep and fatigue. The response rate was 32% and the final sample had 435 pilots. The prevalence of sleep complaints was 34.9%, daytime ...

  9. 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

  10. 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

  11. 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.

  12. 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

  13. [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

  14. Fatigue and fatigue-related symptoms in patients treated for different causes of hypothyroidism

    NARCIS (Netherlands)

    Louwerens, M.; Appelhof, B.C.; Verloop, H.; Medici, M.; Peeters, R.P.; Visser, T.J.; Boelen, A.; Fliers, E.; Smit, J.W.A.; Dekkers, O.M.

    2012-01-01

    OBJECTIVE: Research on determinants of well-being in patients on thyroid hormone replacement therapy is warranted, as persistent fatigue-related complaints are common in this population. In this study, we evaluated the impact of different states of hypothyroidism on fatigue and fatigue-related sympt

  15. 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)

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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...

  3. Fatigue modeling of materials with complex microstructures

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2011-01-01

    with the 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...... 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....

  4. Fatigue tests on the ITER PF jacket

    Science.gov (United States)

    Qin, Jinggang; Weiss, Klaus-Peter; Wu, Yu; Wu, Zhixiong; Li, Laifeng; Liu, Sheng

    2012-10-01

    This paper focuses on fatigue tests on the ITER Poloidal Field (PF) jacket made of 316L stainless steel material. During manufacture, the conductor will be compacted and spooled after cable insertion. Therefore, sample jackets were prepared under compaction, bending and straightening in order to simulate the status of PF conductor during manufacturing and winding. The fatigue properties of materials were measured at T fatigue crack growth rate (FCGR). The testing results show that the present Chinese PF jacket has good fatigue properties, which conclude that the results are accordant with the requirements of ITER.

  5. 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.

  6. 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

  7. 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.

  8. Fatigue Reliability under Multiple-Amplitude Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution...... for the 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...

  9. 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 ...

  10. 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.......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....

  11. 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.

  12. Fatigue in osteoarthritis: a qualitative study

    Directory of Open Access Journals (Sweden)

    French Melissa R

    2008-05-01

    Full Text Available Abstract Background Fatigue is recognized as a disabling symptom in many chronic conditions including rheumatic disorders such as rheumatoid arthritis (RA and lupus. Fatigue in osteoarthritis (OA is not routinely evaluated and has only been considered in a very limited number of studies. To date, these studies have focused primarily on patients with OA under rheumatological care, which represent the minority of people living with OA. The purpose of this study was to increase our understanding of the fatigue experience in community dwelling people with OA. Methods In 2004, 8 focus groups were conducted with 28 men and 18 women (mean age 72.3 with symptomatic hip or knee OA recruited from a population-based cohort. Participants completed a self-administered questionnaire, which included demographics, measures of OA severity (WOMAC, depression (CES-D and fatigue (FACIT. Sessions were audio taped and transcribed verbatim. Two researchers independently reviewed the transcripts to identify themes. Findings were compared and consensus reached. Results Mean pain, disability, depression and fatigue scores were 8.7/20, 27.8/68, 15.4/60, and 30.9/52, respectively. Participants described their fatigue as exhaustion, being tired and "coming up against a brick wall". Participants generally perceived fatigue as different from sleepiness and distinguished physical from mental fatigue. Factors believed to increase fatigue included OA pain and pain medications, aging, various types of weather and poor sleep. Mental health was identified as both affecting fatigue and being affected by fatigue. Participants described fatigue as impacting physical function, and their ability to participate in social activities and to do household chores. Rest, exercise, and avoiding or getting assistance with activities were cited as ways of coping. Participants generally did not discuss their fatigue with anyone except their spouses. Conclusion Participants with OA described

  13. Exercise and fatigue in rheumatoid arthritis.

    Science.gov (United States)

    Balsamo, Sandor; Diniz, Leonardo R; dos Santos-Neto, Leopoldo L; da Mota, Licia M H

    2014-01-01

    Fatigue, the enduring sensation of weakness, lack of energy, tiredness or exhaustion, is described by 40%-80% of patients with rheumatoid arthritis as their most disabling symptom with wide-ranging consequences for quality of life. Little attention has been paid to its multidimensional nature or to its reliability as a measure to evaluate progression of the disease. Low impact aerobic exercise affects the level of fatigue, and this same level of fatigue influences the exercise itself. We searched Medline, Cochrane Collaboration Register of Controlled Trials (CCRCT), Lilacs, PubMed and Scopus databases for randomized controlled trials (with appropriate description of methods, materials and results) on the assessment of fatigue and exercise. Review articles, case reports, letters to the editor and editorials were excluded. Of 121 references initially identified, 4 randomized controlled trials met the inclusion criteria. Two studies used the MAF scale (Multidimensional Assessment of Fatigue), one used the MAC (Mental Adjustment to Cancer) fatigue scale, and all trials used POMS (Profile of Mood States) to assess fatigue. All four trials conducted a 12 week program of two to three times/ week and different periods of follow-up. Two studies used low impact aerobic exercise, one used dance-based exercise, and another study followed a home cardiopulmonary conditioning program using a stationary bicycle. While fatigue appears to be a reliable outcome measure in the clinical management of RA, especially when related to exercise prescription, further research is needed to evaluate the correlation between exercise, fatigue and quality of life, using fatigue scales validated to explore the different components of fatigue and its wide-ranging consequences.

  14. The effect of fatigue and fibromyalgia on sexual dysfunction in women with chronic fatigue syndrome.

    Science.gov (United States)

    Blazquez, Alicia; Ruiz, Eva; Aliste, Luisa; García-Quintana, Ana; Alegre, José

    2015-01-01

    Sexual dysfunction in patients with chronic fatigue syndrome is attracting growing interest but, to date, few studies have analyzed it. For this reason, the authors evaluated sexual dysfunction in women with chronic fatigue syndrome (using the Golombok Rust Inventory of Sexual Satisfaction) and explore correlations with fatigue and other symptoms. Sexual dysfunction was greater in patients with chronic fatigue syndrome (n = 615) with a higher number of cognitive, neurological, and neurovegetative symptoms, concomitant fibromyalgia, Sjögren's syndrome, or myofascial pain syndrome, and more intense fatigue (p <.05).

  15. 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.

  16. 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)

  17. 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)

  18. 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 being of key importance for SR Ca2+ release and thereby affecting muscle contractility and fatigability....

  19. 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

  20. 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 ...

  1. 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)

  2. Cancer-Related Fatigue: a multidimensional approach

    NARCIS (Netherlands)

    P.J. de Raaf (Pleun)

    2013-01-01

    textabstractFatigue is experienced by cancer patients in all stages of the disease trajectory: from before diagnosis to years after completing treatment and also in advanced cancer. Fatigue has a greater negative influence on quality of life and daily activities than any other cancer-related symptom

  3. 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)

  4. Corrosion Fatigue in District Heating Water Tanks

    DEFF Research Database (Denmark)

    Maahn, Ernst Emanuel

    1996-01-01

    fatigue of plain tensile specimens and crack growth rate determination for Compact Tensile Specimens under corrosion fatigue conditions. The three materials are equal with respect to stress corrosion sensibility and crack initiation. Crack growth rate is increased with a factor of 4-6 relative to an inert...

  5. 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.

  6. Exercise therapy for fatigue in multiple sclerosis

    NARCIS (Netherlands)

    Heine, Martin; van de Port, Ingrid; Rietberg, Marc B; van Wegen, Erwin Eh; Kwakkel, Gert

    2015-01-01

    BACKGROUND: Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system affecting an estimated 1.3 million people worldwide. It is characterised by a variety of disabling symptoms of which excessive fatigue is the most frequent. Fatigue is often reported as the most invalidat

  7. 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

  8. Neuromuscular frequency-coding and fatigue

    NARCIS (Netherlands)

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

    1995-01-01

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

  9. 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.

  10. 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...

  11. 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,

  12. 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.

  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. 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

  15. 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...... searched for relevant peer-reviewed studies. Reference lists of eligible papers will also be searched. All English language studies with a longitudinal design that focus on fatigue in adults with primary-impact traumatic brain injury will be included. Studies on fatigue following brain injury due...

  16. Damage identity in fatigue assessment of structures

    Directory of Open Access Journals (Sweden)

    S.V. Petinov

    2016-04-01

    Full Text Available The modified strain criterion-based method for fatigue assessment of structures is discussed. The damage is estimated based on the specified parameters of the criterion and the damage summation procedure by employing the finite-element method. With a reasonably fine mesh of the finiteelement model of the ‘critical location’ structure, the condition of the identity of damage in the material of the test specimen and the structure is provided and, respectively, the effect of uncertainty on the fatigue life assessment of the structure is reduced. The implementation of this version of the method is using the example of the fatigue life evaluation of a ship hull and superstructure detail at expansion joint. For comparison, the fatigue life of the detail is estimated using the standard S-N approach. The results are in approximate agreement; however, reducing the computational uncertainties with the help of the deformation criterion shows more physically reasonable fatigue properties of the detail.

  17. 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.

  18. 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...

  19. 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.

  20. 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.

  1. Fatigue Minimization Work Shift Scheduling for Air Traffic Controllers

    Directory of Open Access Journals (Sweden)

    Ta-Chung Wang

    2013-05-01

    Full Text Available It is common for Air Traffic Controllers to control air traffic during the night and to experience fatigue. Although fatigue is not the direct cause of aviation accidents, 21 percent of accidents are fatigue-related. Therefore countries and companies have tried to regulate work hours to avoid extreme fatigue, thus decreasing human error resulting from fatigue. However, these regulations may not reflect that actual fatigue variation and fatigue levels can be decreased still more by scheduling appropriately. This paper focuses on optimal work shift scheduling to reduce air traffic controller fatigue. First, a mathematical model is established to describe fatigue levels. The objective function is to reduce the fatigue peak produced by work shifts as much as possible. Various constraints, such as holidays and manpower requirements are considered. The optimization problem is then solved using integer programming. We take a sample schedule and draw conclusions by comparing our results with the original fatigue levels.

  2. 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

  3. German experiences in local fatigue monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Abib, E.; Bergholz, S.; Rudolph, J. [AREVA NP GmbH, Henri-Dunant-Strasse 50, Erlangen, Bayern, 91058 (Germany)

    2012-07-01

    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. 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.

  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. Fatigue and cardiorespiratory function following abdominal surgery.

    Science.gov (United States)

    Christensen, T; Bendix, T; Kehlet, H

    1982-07-01

    Subjective feelings of fatigue were assessed before operation and 10, 20 and 30 days after uncomplicated elective abdominal surgery in 16 otherwise healthy patients, using a constructed fatigue scale model. In addition, all patients had an orthostatic stress test performed at the same times. Six of the patients also underwent a bicycle ergometer test measuring heart rate and oxygen consumption. Subjective feelings of fatigue were increased (P less than 0.01) at all three postoperative observations, and only 5 of 16 patients returned to their preoperative level. The increased subjective feeling of fatigue correlated positively (RS = 0.53, P less than 0.001) with the increased pulse rate seen during orthostatic stress after operation. Heart rate was about 5 per cent higher (n.s.) after operation when bicycling at the same work loads, while oxygen consumption decreased by about 2 per cent (P less than 0.01) at all three postoperative bicycle tests. It is concluded that even electric uncomplicated abdominal surgery is followed by a pronounced feeling of fatigue, which may persist 1 month after surgery in about one-third of patients. The fatigue scale model seems applicable for future studies on the pathogenesis and treatment of the postoperative fatigue syndrome.

  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. Mental fatigue impairs physical performance in humans.

    Science.gov (United States)

    Marcora, Samuele M; Staiano, Walter; Manning, Victoria

    2009-03-01

    Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. Although the impact of mental fatigue on cognitive and skilled performance is well known, its effect on physical performance has not been thoroughly investigated. In this randomized crossover study, 16 subjects cycled to exhaustion at 80% of their peak power output after 90 min of a demanding cognitive task (mental fatigue) or 90 min of watching emotionally neutral documentaries (control). After experimental treatment, a mood questionnaire revealed a state of mental fatigue (P = 0.005) that significantly reduced time to exhaustion (640 +/- 316 s) compared with the control condition (754 +/- 339 s) (P = 0.003). This negative effect was not mediated by cardiorespiratory and musculoenergetic factors as physiological responses to intense exercise remained largely unaffected. Self-reported success and intrinsic motivation related to the physical task were also unaffected by prior cognitive activity. However, mentally fatigued subjects rated perception of effort during exercise to be significantly higher compared with the control condition (P = 0.007). As ratings of perceived exertion increased similarly over time in both conditions (P < 0.001), mentally fatigued subjects reached their maximal level of perceived exertion and disengaged from the physical task earlier than in the control condition. In conclusion, our study provides experimental evidence that mental fatigue limits exercise tolerance in humans through higher perception of effort rather than cardiorespiratory and musculoenergetic mechanisms. Future research in this area should investigate the common neurocognitive resources shared by physical and mental activity. PMID:19131473

  12. Fatigue Properties of Cast Magnesium Wheels

    Science.gov (United States)

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

    2016-08-01

    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.

  13. 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.

  14. 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

  15. Low-cycle fatigue of surgical cements

    Directory of Open Access Journals (Sweden)

    A. Balin

    2007-01-01

    Full Text Available Purpose: In case when surgical cement is used to fix endoprostheses of joints the fatigue character of mechanicalinterraction in the cement seems to be a significant importance. The paper suggests to adapt the research methodof low cycle fatigue for modelling the loads on surgical cements in an artificial hip joint. Surgical cements havealso been modified in order to improve their functional properties.Design/methodology/approach: Low cycle fatigue tests were conducted on samples made from Palamedcement without an addition and on samples modified with glassy carbon and titanium. The tests were conductedon a servohydraulic fatigue testing machine, MTS-810, with displacement control.Findings: Fatigue tests proved viscoelastic character of all the tested materials. During the fatigue tests, thephenomenon of stress cyclic relaxation was observed.Research limitations/implications: Modelling the loadings of cement in endoprostheses of joints with the lowcycle fatigue method takes into account all high value stresses, while cement is being used for endoprosthesesfor many years in the conditions of random stress and deformation courses. Therefore the obtained stress anddeformation values are bigger than those which would have been obtained in real conditions in the same time.Practical implications: The low cycle fatigue tests carried out showed how important is the factor of timefor the behavior of surgical cement in the conditions of changeable loadings. This fact is essential to assessits usability for endoprosthesoplasty of joints, specially of a hip joint. Post deformation return which is acharacteristic feature for material viscoelasticity enables its regeneration conditioning expected durability ofendoprosthesis of joints.Originality/value: Low cycle fatigue testing method for modelling of loads on surgical cement in artificial hipjoint enables to carry out the tests in a shorter period of time.

  16. 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

  17. 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

  18. Does Corruption Cause Aid Fatigue?

    DEFF Research Database (Denmark)

    Bauhr, Monika; Charron, Nicholas; Nasiritousi, Naghmeh

    2013-01-01

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

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. 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...

  4. Finite element simulation of asphalt fatigue testing

    DEFF Research Database (Denmark)

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

    1997-01-01

    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...... three point and four point fatigue test on different mixes. It is shown that the same damage law, based on energy density, may be used to explain the gradual deterioration under constant stress as well as under constant strain testing.Some of the advantages of using this method for interpreting fatigue...

  5. 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.

  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. Modified low-cycle fatigue (LCF test

    Directory of Open Access Journals (Sweden)

    M. Maj

    2015-01-01

    Full Text Available 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 of the modified low-cycle fatigue test in practice.

  8. 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...... are 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...

  9. Jacket Substructure Fatigue Mitigation through Active Control

    DEFF Research Database (Denmark)

    Hanis, Tomas; Natarajan, Anand

    2014-01-01

    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....

  10. 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...

  11. 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.

  12. 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

  13. 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...

  14. 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-...

  15. 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.

  16. 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)

  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. Neural effect of mental fatigue on physical fatigue: a magnetoencephalography study.

    Science.gov (United States)

    Tanaka, Masaaki; Ishii, Akira; Watanabe, Yasuyoshi

    2014-01-13

    We sought to clarify the neural effect of mental fatigue on physical fatigue using magnetoencephalography (MEG) and classical conditioning techniques. Eleven right-handed volunteers participated in this study. On the first day, participants performed fatigue-inducing maximum handgrip trials for 10 min; metronome sounds were started 5 min after the beginning of the trials. We used metronome sounds as conditioned stimuli and maximum handgrip trials as unconditioned stimuli to cause physical fatigue. On the next day, MEG recordings during the imagery of maximum grips of the right hand guided by the metronome sounds were performed for 10 min just before (control session) and after (mental fatigue session) a 30-min fatigue-inducing mental task session. In the right anterior cingulate cortex (Brodmann's area 23), the alpha-band event-related synchronization of the mental fatigue session relative to the control session within the time window of 500–600 ms after the onset of handgrip cue sounds was identified. We demonstrated that mental fatigue suppresses activities in the right anterior cingulate cortex during physical fatigue.

  19. Fatigue lifetime of AlBC(3 alloy by ultrasonic fatigue testing machine in cavitation regime

    Directory of Open Access Journals (Sweden)

    I.S. Cho

    2015-08-01

    Full Text Available In this study, the influence of ultrasonic nanocrystalline surface modification (UNSM technique on the cavitation fatigue properties of AlBC(3 alloy was investigated. The fatigue properties of the untreated and treated specimens were assessed using an ultrasonic fatigue testing (UFT machine. The treated specimens exhibited longer fatigue life in comparison with those of the untreated specimens, which may attributed to the plastically deformed layer at the top surface of the treated specimen. Also, a fracture analysis was studied using a scanning electron microscopy (SEM to shed light on the fracture behavior of the specimens.

  20. 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)

  1. 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.

  2. Metabolic features of chronic fatigue syndrome

    Science.gov (United States)

    Naviaux, Robert K.; Naviaux, Jane C.; Li, Kefeng; Bright, A. Taylor; Alaynick, William A.; Wang, Lin; Baxter, Asha; Nathan, Neil; Anderson, Wayne; Gordon, Eric

    2016-01-01

    More than 2 million people in the United States have myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We performed targeted, broad-spectrum metabolomics to gain insights into the biology of CFS. We studied a total of 84 subjects using these methods. Forty-five subjects (n = 22 men and 23 women) met diagnostic criteria for ME/CFS by Institute of Medicine, Canadian, and Fukuda criteria. Thirty-nine subjects (n = 18 men and 21 women) were age- and sex-matched normal controls. Males with CFS were 53 (±2.8) y old (mean ± SEM; range, 21–67 y). Females were 52 (±2.5) y old (range, 20–67 y). The Karnofsky performance scores were 62 (±3.2) for males and 54 (±3.3) for females. We targeted 612 metabolites in plasma from 63 biochemical pathways by hydrophilic interaction liquid chromatography, electrospray ionization, and tandem mass spectrometry in a single-injection method. Patients with CFS showed abnormalities in 20 metabolic pathways. Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome. Pathway abnormalities included sphingolipid, phospholipid, purine, cholesterol, microbiome, pyrroline-5-carboxylate, riboflavin, branch chain amino acid, peroxisomal, and mitochondrial metabolism. Area under the receiver operator characteristic curve analysis showed diagnostic accuracies of 94% [95% confidence interval (CI), 84–100%] in males using eight metabolites and 96% (95% CI, 86–100%) in females using 13 metabolites. Our data show that despite the heterogeneity of factors leading to CFS, the cellular metabolic response in patients was homogeneous, statistically robust, and chemically similar to the evolutionarily conserved persistence response to environmental stress known as dauer. PMID:27573827

  3. Metabolic features of chronic fatigue syndrome.

    Science.gov (United States)

    Naviaux, Robert K; Naviaux, Jane C; Li, Kefeng; Bright, A Taylor; Alaynick, William A; Wang, Lin; Baxter, Asha; Nathan, Neil; Anderson, Wayne; Gordon, Eric

    2016-09-13

    More than 2 million people in the United States have myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We performed targeted, broad-spectrum metabolomics to gain insights into the biology of CFS. We studied a total of 84 subjects using these methods. Forty-five subjects (n = 22 men and 23 women) met diagnostic criteria for ME/CFS by Institute of Medicine, Canadian, and Fukuda criteria. Thirty-nine subjects (n = 18 men and 21 women) were age- and sex-matched normal controls. Males with CFS were 53 (±2.8) y old (mean ± SEM; range, 21-67 y). Females were 52 (±2.5) y old (range, 20-67 y). The Karnofsky performance scores were 62 (±3.2) for males and 54 (±3.3) for females. We targeted 612 metabolites in plasma from 63 biochemical pathways by hydrophilic interaction liquid chromatography, electrospray ionization, and tandem mass spectrometry in a single-injection method. Patients with CFS showed abnormalities in 20 metabolic pathways. Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome. Pathway abnormalities included sphingolipid, phospholipid, purine, cholesterol, microbiome, pyrroline-5-carboxylate, riboflavin, branch chain amino acid, peroxisomal, and mitochondrial metabolism. Area under the receiver operator characteristic curve analysis showed diagnostic accuracies of 94% [95% confidence interval (CI), 84-100%] in males using eight metabolites and 96% (95% CI, 86-100%) in females using 13 metabolites. Our data show that despite the heterogeneity of factors leading to CFS, the cellular metabolic response in patients was homogeneous, statistically robust, and chemically similar to the evolutionarily conserved persistence response to environmental stress known as dauer. PMID:27573827

  4. SEAFARER FATIGUE: A REVIEW OF RISK FACTORS

    DEFF Research Database (Denmark)

    Jepsen, Jørgen Riis; Zhao, Zhiwei; Tu, Mingshan;

    2016-01-01

    Background: The widespread occurrence of fatigue in the maritime industry and the consequences for the health and safety of seafarers have caused concern, and indicates the importance of research into risk factors at sea. This review gives an overview of the currently recognized key determinants...... of seafarer fatigue. Methods: A literature study was conducted aiming to collect publications that address work-related risk factors for fatigue. Due to the limited number of publications that deals with seafarers, experiences from other populations sharing the same exposures (e.g. shift work) were also...... included when appropriate. Results: Work at sea involves multiple external risk factors for fatigue such as work stress, irregular work, sleep quantity and quality, workload, and physical factors such as noise and vessel movements. Vulnerability varies between individuals. Conclusions: Taking into account...

  5. 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.

  6. 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.

  7. 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( ...

  8. 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.)

  9. 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.

  10. Fatigue (PDQ®)—Patient 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.

  11. 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)

  12. 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...

  13. Mechanisms of exertional fatigue in muscle glycogenoses

    DEFF Research Database (Denmark)

    Vissing, John; Haller, Ronald G

    2012-01-01

    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....

  14. 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.

  15. 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.

  16. 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.

  17. 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....

  18. 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...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Eight Easy Ways to Beat Fatigue

    Institute of Scientific and Technical Information of China (English)

    Russell; Wild; 郑英培

    1998-01-01

    国人的生活节奏确实加快了! 我们常闻身边的人感叹:唉,吃得下,又睡得着,怎么就这么累?常生此感者,不妨细读此文。 文章介绍了8种导致“莫名疲惫”的可能,可供读者“对号入座”! 其中最具参考价值的是: 首先,周末睡懒觉的坏习惯,人们试图用此法来消除疲劳,这样做的结果是:越睡越疲劳! 原因: We each have a biological clock(生物钟)that determines when we are sleepy andwhen we are alert.When you wake up every morning at seven but sleep until noon onweekends,you can upset your biological clock and end up feeling even more fatigued. 那么,应如何通过在周末增加睡眠以消除疲劳呢?做法很简单: Catch up on weekends by going to bed early,not sleeping late.To keep yourbiological block happy,it is best to wake up every morning at about the same time. 其实,此观点并不新鲜,国人有“黎明即起,洒扫庭除”之说久矣! 其次,体内水份不足也是疲劳袭来的原因之一: A lack of water can cause a decrease in blood volume,and that can bring onfatigue. 本文提出了一个每日喝水的参考量: Drink eight to ten glasses of water a day ,or more if you exercise heavily. 再次,不注意

  5. 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.

  6. Factors related to fatigue; priority of interventions to reduce or eliminate fatigue and the exploration of a multidisciplinary research model for further study of fatigue

    NARCIS (Netherlands)

    Tiesinga, LJ; Dassen, TWN; Halfens, RJG; van den Heuvel, WJA

    1999-01-01

    A growing interest in the health problem presented by fatigue, both in clinical practice and research, coupled with a decreasing number of reported studies on fatigue in the last decade, make an updated and systematic review of factors related to fatigue necessary. A search of the literature, compri

  7. 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 ...

  8. 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

  9. 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...

  10. 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.

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. 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

  19. Fretting fatigue in AISI 1015 steel

    Indian Academy of Sciences (India)

    R Gnanamoorthy; R Rosi Reddy

    2002-04-01

    A small osillatory movement between two contacting surfaces is termed as fretting and on many occasions it acts as the crack initiation site leading to catastrophic failure of the overall structure. The occurrence of fretting is observed in many engineering structures such as shaft flanges, gas turbines, steel ropes etc. An experimental facility, which can simulate the fretting fatigue in many engineering applications, is the primary requirement of the research program. A laboratory fretting fatigue test facility capable of varying many influencing parameters of fretting fatigue such as slip amplitutde, frequency, contact pressure, etc is designed and developed. Preliminary investigations on plain and fretting fatigue behaviour of AISI 1015 structural steel are reported in this paper. A strength reduction factor of about 1.30 was obtained due to fretting for the test material under the present experimental conditions. Influence of contact load on fretting was also studied. Increasing fretting contact load decreased the fatigue life in the range investigated. Failure analysis showed typical stage I oblique crack growth followed by stage II straight crack perpedicular to the fretting zone.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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....

  5. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2009-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. 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 with a total of 540 fatigue tests 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 or high-strength steel. The fatigue tests...... and variable amplitude fatigue 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...

  6. 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) ...

  7. A preliminary bending fatigue spectrum for steel monostrand cables

    DEFF Research Database (Denmark)

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

    2011-01-01

    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...

  8. 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....

  9. Assessment of fatigue life of remanufactured impeller based on FEA

    Science.gov (United States)

    Xu, Lei; Cao, Huajun; Liu, Hailong; Zhang, Yubo

    2016-09-01

    Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.

  10. Practical Guideline for Fatigue Management in Inflammatory Bowel Disease.

    Science.gov (United States)

    Kreijne, J E; Lie, M R K L; Vogelaar, L; van der Woude, C J

    2016-01-01

    During active inflammatory bowel disease (IBD) fatigue is a common symptom, which seems related to active gut inflammation. However, even in remission many patients suffer from fatigue that negatively affects quality of life and work productivity. Currently, robust knowledge on the pathogenesis and treatment of IBD-related fatigue is lacking. In order to alleviate the burden of IBD-related fatigue, a systematic approach is mandatory. We propose a fatigue attention cycle to enhance identification, evaluation and management of fatigued IBD patients. The benefits of the cycle are twofold. Firstly, it allows the systematic and uniform identification of patients with severe fatigue, in turn allowing tailored non-pharmacological and pharmacological interventions. Secondly, uniform identification of such patients creates a well-defined patient base to investigate the underlying pathogenesis of fatigue, resulting in a greater understanding of this debilitating phenomenon and possibly resulting in the discovery of predictive factors and new treatment interventions.

  11. 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.

  12. 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.

  13. 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 ...

  14. CT and Clinical Predictors of Fatigue at One Month after Stroke

    Directory of Open Access Journals (Sweden)

    Mansur A. Kutlubaev

    2013-03-01

    gender, anxiety and depression may be linked with fatigue. Therefore, clinical vigilance rather than CT features should be used to predict fatigue early after stroke. Further research is needed in this area to establish whether biological mechanisms underlie the development of PSF.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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 analog control device remain as the basic control mechanism in the system, but distorting the input signal by computer in order to minimize the errors of the load history extremes. The principle proves to be very efficient to reduce all kinds of system errors and has shown to be able to increase...

  1. 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)

  2. 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.

  3. 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.

  4. 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

  5. Computer Simulations of the Fatigue Crack Propagation

    Directory of Open Access Journals (Sweden)

    A. Materna

    2000-01-01

    Full Text Available The following hypothesis for design of structures based on the damage tolerance philosophy is laid down: the perpendicular fatigue crack growth rate v in a certain point of a curved crack front is given by the local value of stress intensity factor per unit of nominal stress K' and the local triaxiality T which describes the constraint. The relationship v = f (K', T is supposed to be typical for a given loading spectrum and material. Such relationship for a 2024 Al alloy and the flight-simulation spectrum was derived from the fatigue test of the rectangular panel with the central hole and used for three-dimensional simulation of the corner fatigue crack propagation in the model of the wing spar flangeplate. Finite element and boundary element methods were used for these computations. The results of the simulation are in good agreement with the experiment.

  6. Fatigue Life Prediction under Service Load Considering Strengthening Effect of Loads below Fatigue Limit

    Institute of Scientific and Technical Information of China (English)

    ZHAO Lihui; ZHENG Songlin; FENG Jinzhi

    2014-01-01

    Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule (PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule (MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are –3.78% and –1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

  7. 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.

  8. Fatigue in lung cancer patients: symptom burden and management of challenges

    Directory of Open Access Journals (Sweden)

    Carnio S

    2016-05-01

    Full Text Available Simona Carnio, Rosario Francesco Di Stefano, Silvia Novello Oncology Department, University of Turin, AOU San Luigi, Orbassano, Italy Abstract: Lung cancer (LC remains the most common cause of cancer death in several countries across the world. Fatigue is the most frequently reported symptom in LC patients throughout the entire course of disease, and all international guidelines recommend early screening for cancer-related fatigue (CRF and symptoms that can affect patients' quality of life. In patients with LC, fatigue belongs to the symptom cluster of pain, depression, and insomnia, which are commonly observed simultaneously, but are typically treated as separate although they may have common biological mechanisms. The treatment of CRF remains one of the difficult areas in the oncology field: scarce evidence supports pharmacological therapies, while some interesting data arising indicates alternative remedies and physical exercise seem to be one of the most effective approaches for CRF at any stage of LC. Keywords: fatigue, lung cancer, symptom cluster, quality of life

  9. 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...

  10. 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...

  11. 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 ...

  12. 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)

  13. 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.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. Atomistic Mechanisms of Fatigue in Nanocrystalline Metals

    Science.gov (United States)

    Farkas, D.; Willemann, M.; Hyde, B.

    2005-04-01

    We investigate the mechanisms of fatigue behavior in nanocrystalline metals at the atomic scale using empirical force laws and molecular level simulations. A combination of molecular statics and molecular dynamics was used to deal with the time scale limitations of molecular dynamics. We show that the main atomistic mechanism of fatigue crack propagation in these materials is the formation of nanovoids ahead of the main crack. The results obtained for crack advance as a function of stress intensity amplitude are consistent with experimental studies and a Paris law exponent of about 2.

  20. 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...

  1. 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.

  2. 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.-

  3. PROBABILISTIC MINER'S RULE IN FATIGUE RELIABILITY

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Firstly, constant amplitude P-Sa-Sm-Nc surface family is established. Secondly, four basic assumptions, i.e., monotonically increasing, non-coupling, separability and nonintersecting of fatigue damage accumulation are proposed from the viewpoint of both damage mechanics and fracture mechanics. Then the individual isodamage D-Sa-Sm-N surface under constant amplitude loading is constructed and the two-dimensional individual Miner's rule is derived. Consequently, the two-dimensional probabilistic Miner's rule (TPMiner) is established and proved for a population subjected to variable amplitude loading. Finally, with successfully experiment verification, TPMiner proves be to very useful and feasible in fatigue reliability theory.

  4. Are chronic fatigue and chronic fatigue syndrome valid clinical entities across countries and health-care settings?

    NARCIS (Netherlands)

    Hickie, I.; Davenport, T.; Vernon, S.D.; Nisenbaum, R.; Reeves, W.C.; Hadzi-Pavlovic, D.; Lloyd, A.; Bleijenberg, G.; Werf, S.P. van der; Prins, J.B.; Blenkiron, P.M.; Buchwald, D.; Smith, W.R.; Edwards, R.; Lynch, S.; Kirmayer, L.J.; Taillefer, S.S.; Lee, S.; Martin, N.G.; Gillespie, N.E.; McIlvenny, S.; Sartorius, N.; Ustun, T.B.; Skapinakis, P.; Wessely, S.; Chalder, T.; Hotopf, M.; Nimnuan, C.; Candy, B.; Darbishire, L.; Ridsdale, L.; White, P.D.; Thomas, J.M.; Wilhelm, K.; Wilson, A.

    2009-01-01

    OBJECTIVE: The validity of the diagnosis of chronic fatigue syndrome and related chronic fatigue states remains controversial, particularly in psychiatry. This project utilized international epidemiological and clinical research data to test construct validity across diagnostic categories, health-ca

  5. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2008-01-01

    of the investigation, fatigue test series with a total of 540 fatigue tests 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 or high-strength steel. The fatigue tests...

  6. 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

  7. 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.

  8. Fatigue failure of sandwich beams with face sheet wrinkle defects

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Hvejsel, C.F.; Thomsen, Ole Thybo;

    2012-01-01

    This paper presents experimental fatigue results for GFRP face sheet/balsa core sandwich beams with face sheet wrinkle defects, subjected to fully reversed in-plane fatigue loading. An estimate of the fatigue design limit is presented, based on static test results, finite element analyses and app...

  9. 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...

  10. Probabilistic Fatigue Design of Composite Material for Wind Turbine Blades

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2011-01-01

    In the present paper a probabilistic design approach to fatigue design of wind turbine blades is presented. The physical uncertainty on the fatigue strength for composite material is estimated using public available fatigue tests. Further, the model uncertainty on Miner rule for damage accumulation...

  11. Cumulative creep fatigue damage in 316 stainless steel

    Science.gov (United States)

    Mcgaw, Michael A.

    1989-01-01

    The cumulative creep-fatigue damage behavior of 316 stainless steel at 1500 F was experimentally established for the two-level loading cases of fatigue followed by fatigue, creep fatigue followed by fatigue, and fatigue followed by creep fatigue. The two-level loadings were conducted such that the lower life (high strain) cycling was applied first for a controlled number of cycles and the higher life (low strain) cycling was conducted as the second level to failure. The target life levels in this study were 100 cycles to failure for both the fatigue and creep-fatigue lowlife loading, 5000 cycles to failure for the higher life fatigue loading and 10,000 cycles to failure for the higher life creep-fatigue loading. The failed specimens are being examined both fractographically and metallographically to ascertain the nature of the damaging mechanisms that produced failure. Models of creep-fatigue damage accumulation are being evaluated and knowledge of the various damaging mechanisms is necessary to ensure that predictive capability is instilled in the final failure model.

  12. 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.

  13. 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

  14. Fatigue crack propagation and delamination growth in Glare

    NARCIS (Netherlands)

    Alderliesten, R.C.

    2005-01-01

    Fibre Metal Laminate Glare consists of thin aluminium layers bonded together with pre-impregnated glass fibre layers and shows an excellent fatigue crack growth behaviour compared to monolithic aluminium. The fibres are insensitive to the occurring fatigue loads and remain intact while the fatigue c

  15. 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.

  16. 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

  17. Cancer-related fatigue : Predictors and effects of rehabilitation

    NARCIS (Netherlands)

    van Weert, Ellen; Hoekstra-Weebers, Josette; Otter, Renee; Postema, Klaas; Sanderman, Robbert; van der Schans, Cees

    2006-01-01

    Background. The aims of the study were to examine the effects of a multidimensional rehabilitation program on cancer-related fatigue, to examine concurrent predictors of fatigue, and to investigate whether change in fatigue over time was associated with change in predictors. Methods. Sample: 72 canc

  18. Review: Gigacycle fatigue data sheets for advanced engineering materials

    Directory of Open Access Journals (Sweden)

    Koji Yamaguchi, Takayuki Abe, Kazuo Kobayashi, Etsuo Takeuchi, Hisashi Hirukawa, Yoshio Maeda, Nobuo Nagashima, Masao Hayakawa, Yoshiyuki Furuya, Masuo Shimodaira and Kensuke Miyahara

    2007-01-01

    Full Text Available Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 1010 cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 108 cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete.

  19. Predictors and consequences of fatigue in prevalent kidney transplant recipients

    NARCIS (Netherlands)

    W. Chan; J.A. Bosch; D. Jones; O. Kaur; N. Inston; S. Moore; A. McClean; P.G. McTernan; L. Harper; A.C. Phillips; R. Borrows

    2013-01-01

    Background: Fatigue has been underinvestigated in stable kidney transplant recipients (KTRs). The objectives of this study were to investigate the nature, severity, prevalence, and clinical awareness of fatigue in medically stable KTRs, examine the impact of fatigue on quality of life (QoL), and exp

  20. Principles of fatigue in residency education: a qualitative study

    Science.gov (United States)

    Taylor, Taryn S.; Watling, Christopher J.; Teunissen, Pim W.; Dornan, Tim; Lingard, Lorelei

    2016-01-01

    Background: Proposals to implement fatigue-management strategies in residency education assume that medicine shares the view of other risk-adverse industries that fatigue is hazardous. This view is an essential underpinning of fatigue-management strategies that other industries have embedded as part of their workplace occupational health and safety programs. We sought to explore how residents understand fatigue in the context of their training environment. Methods: We interviewed 21 residents in 7 surgical and nonsurgical programs at Western University in 2014. All participants met the inclusion criteria of routinely working 24-hour call shifts while enrolled in their training program. Data collection and analysis occurred iteratively in keeping with constructivist grounded theory methodology and informed theoretical sampling to sufficiency. Results: Four predominant principles of fatigue captured how the social learning environment shaped residents' perceptions of fatigue. These included the conceptualization of fatigue as (a) inescapable and therefore accepted, (b) manageable through experience, (c) necessary for future practice and (d) surmountable when required. Interpretation: This study elaborates our understanding of how principles of fatigue are constructed and reinforced by the training environment. Whereas fatigue is seen as a collective hazard in other industries, our data showed that, in residency training, fatigue may be seen as a personal challenge. Consequently, fatigue-management strategies that conceptualize fatigue as an occupational threat may have a limited impact on resident behaviour and patient safety. PMID:27398364

  1. 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

  2. Fatigue-Related Gene Networks Identified in CD14+ Cells Isolated From HIV-Infected Patients—Part I: Research Findings

    Science.gov (United States)

    Voss, Joachim G.; Dobra, Adrian; Morse, Caryn; Kovacs, Joseph A.; Danner, Robert L.; Munson, Peter J.; Logan, Carolea; Rangel, Zoila; Adelsberger, Joseph W.; McLaughlin, Mary; Adams, Larry D.; Raju, Raghavan; Dalakas, Marinos C.

    2016-01-01

    Purpose Human immunodeficiency virus (HIV)–related fatigue (HRF) is multicausal and potentially related to mitochondrial dysfunction caused by antiretroviral therapy with nucleoside reverse transcriptase inhibitors (NRTIs). Methodology The authors compared gene expression profiles of CD14+ cells of low versus high fatigued, NRTI-treated HIV patients to healthy controls (n = 5/group). The authors identified 32 genes predictive of low versus high fatigue and 33 genes predictive of healthy versus HIV infection. The authors constructed genetic networks to further elucidate the possible biological pathways in which these genes are involved. Relevance for nursing practice Genes including the actin cytoskeletal regulatory proteins Prokineticin 2 and Cofilin 2 along with mitochondrial inner membrane proteins are involved in multiple pathways and were predictors of fatigue status. Previously identified inflammatory and signaling genes were predictive of HIV status, clearly confirming our results and suggesting a possible further connection between mitochondrial function and HIV. Isolated CD14+ cells are easily accessible cells that could be used for further study of the connection between fatigue and mitochondrial function of HIV patients. Implication for Practice The findings from this pilot study take us one step closer to identifying biomarker targets for fatigue status and mitochondrial dysfunction. Specific biomarkers will be pertinent to the development of methodologies to diagnosis, monitor, and treat fatigue and mitochondrial dysfunction. PMID:23324479

  3. 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...

  4. Dutch Multifactor Fatigue Scale : A New Scale to Measure the Different Aspects of Fatigue After Acquired Brain Injury

    NARCIS (Netherlands)

    Visser-Keizer, Annemarie C.; Hogenkamp, Antoinette; Westerhof-Evers, Herma J.; Egberink, Iris J. L.; Spikman, Jacoba M.

    2015-01-01

    Objectives: To develop the Dutch Multifactor Fatigue Scale (DMFS), a new scale to assess the nature and impact of fatigue and coping with fatigue in the chronic phase after acquired brain injury (ABI) and to analyze the psychometric properties of this scale in a mixed group of patients with ABI. Des

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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...

  11. 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

  12. 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.

  13. 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...

  14. 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

  15. 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.

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

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    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...... 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...

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Thermally activated processes of fatigue crack growth in steels

    Science.gov (United States)

    Tanaka, Masaki; Fujii, Atsushi; Noguchi, Hiroshi; Higashida, Kenji

    2014-02-01

    Fatigue crack growth rates in steels at high and low temperatures have been investigated using Paris curves. The fatigue crack growth rates at high temperatures are quite different from those at low temperatures. Arrhenius plots between fatigue crack growth rate (da/dN) and test temperatures at constant stress intensity factor range (ΔKI) indicate a difference of the rate-controlling process for fatigue crack growth with temperature. Slip deformation at the crack tip governs fatigue crack growth at high temperatures, while hydrogen diffusion is associated with crack growth at low temperatures.

  2. 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.

  3. 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.

  4. 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 wel...

  5. 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…

  6. 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

  7. Fatigue behaviour of titanium dental endosseous implants

    Directory of Open Access Journals (Sweden)

    Alessandro Scicutelli

    2011-10-01

    Full Text Available In this work two different titanium dental implants are analyzed in order to evaluate their mechanical strength. An ad-hoc designed experimental apparatus is prepared to test against fatigue these implants in a way that approximates as much as possible the actual stresses occurring during mastication motion. The results of these endurance tests are summarized in the form of Wohler-type diagrams showing the duration of a specific implant for different applied loads. These plots show a fatigue limit below which the implants could resist indefinitely. Other aspects of this research concern the influence of a potentially corrosive medium and the analysis of the deformation and failure of the specimens. During fatigue cycling, the titanium implants do not seem to be affected by a more aggressive environment, such as a saline solution. The analysis of the broken specimen allowed the crack initiation sites and the type of fracture propagation to be investigated in depth. In all the considered implants fatigue cracks were seen to initiate preferentially from sites in which the tensile stress concentration is the highest. The results of a finite element analysis performed on one of the specimens is in good agreement with the failure mode observed after the tests. The SEM fracture surface analysis shows a clear similarity between the fracture mode of the tested implants and of the actual implants broken after a certain operating period.

  8. Fatigue crack growth in Aluminium Alloys

    NARCIS (Netherlands)

    Van Kranenburg, C.

    2010-01-01

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

  9. Fatigue Feature Classification for Automotive Strain Data

    Science.gov (United States)

    Yunoh, M. F. M.; Abdullah, S.; Nopiah, Z. M.; Nuawi, M. Z.; Ismail, N.

    2012-09-01

    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.

  10. 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.

  11. 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.

  12. 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

  13. Fatigue in IBD outpatients in Scandinavia

    DEFF Research Database (Denmark)

    Bager, Palle; Befrits, Ragnar; Wikman, Ola;

    Prevalensopgørelse af træthed (fatigue) blandt 429 patienter med kronisk inflammatorisk tarmsygdom i Scandinavien. Data blev indsamlet på 6 universitetshospitaler i Danmark, Norge og Sverige. Patienterne var signifikant mere trætte sammenlignet med den danske baggrundsbefolkning, med en kronisk s...

  14. RESISTANCE TO THERMAL FATIGUE AND STANDARDS

    OpenAIRE

    Glandus, J.; Boch, P.; Jouin, C.

    1986-01-01

    Thermal shock resistance of ceramic parts does not depend on materials characteristics only, but also on external parameters (piece geometry, heat exchange...). However, it seems useful to standardize the conditions of measuring of some usual quantities, particularly ƊTc, and to develop some tests to control thermal fatigue damage.

  15. 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...

  16. 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...

  17. 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

  18. 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.

  19. 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

  20. Polarization Fatigue in Ferroelectric Thin Films

    Institute of Scientific and Technical Information of China (English)

    王忆; K.H.WONG; 吴文彬

    2002-01-01

    The fatigue problem in ferroelectric thin films is investigated based on the switched charge per unit area versus switching cycles. The temperature, dielectric permittivity, voltage bias, frequency and defect valence dependent switching polarization properties are calculated quantitatively with an extended Dawber-Scott model. The results are in agreement with the recent experiments.

  1. 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

  2. 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)

  3. 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

  4. Fatigue of tooth-colored restoratives in aqueous environment.

    Science.gov (United States)

    Kawakami, Yoshiko; Takeshige, Fumio; Hayashi, Mikako; Ebisu, Shigeyuki

    2007-01-01

    The purpose of this study was to investigate the interaction between mechanical and chemical fatigue in resin composites and dental ceramics, and the effects thereof on fatigue resistance of tooth-colored restoratives. To this end, the fatigue fracture resistance of restoratives under dry and aqueous conditions were analyzed by a dynamic fatigue crack propagation test using beam-shaped specimens with a precrack. Fatigue crack propagation characteristics were expressed by the correlation between fatigue crack growth rate (da/dN) and stress intensity factor range (deltaK). In addition, fatigue crack growth threshold (deltaKth) was calculated. Following the fatigue test, a fractographic examination was performed using scanning electron microscopy. Fatigue crack initiation was retarded in resin composites under aqueous condition, but dental ceramics were susceptible to slow crack growth after crack initiation. SEM images of the fatigue facture surfaces reflected inorganic and organic filler particles of different sizes in composites and the bonding at crystal-glass interface in ceramics. It was concluded that water exerted different effects on the fatigue resistance of composites and ceramics.

  5. 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.

  6. Fatigue reliability of cracked engineering structures

    Science.gov (United States)

    Lanning, David Bruce, Jr.

    1997-12-01

    This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation

  7. 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.

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    BACKGROUND AND AIMS: Mobility-related fatigue is an important indicator of functional decline in old age, however, very little is known about fatigue in the oldest old population segment. The aim of this study was to examine the association between indoor mobility-related fatigue and muscle...... 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...... 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...

  9. 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.

  10. 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...

  11. 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.

  12. 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

  13. 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...

  14. 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

  15. 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

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

    Directory of Open Access Journals (Sweden)

    Pou Kuan Leong

    2015-01-01

    Full Text Available 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.

  17. 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)

  18. Fatigue crack growth in an aluminum alloy-fractographic study

    Science.gov (United States)

    Salam, I.; Muhammad, W.; Ejaz, N.

    2016-08-01

    A two-fold approach was adopted to understand the fatigue crack growth process in an Aluminum alloy; fatigue crack growth test of samples and analysis of fractured surfaces. Fatigue crack growth tests were conducted on middle tension M(T) samples prepared from an Aluminum alloy cylinder. The tests were conducted under constant amplitude loading at R ratio 0.1. The stress applied was from 20,30 and 40 per cent of the yield stress of the material. The fatigue crack growth data was recorded. After fatigue testing, the samples were subjected to detailed scanning electron microscopic (SEM) analysis. The resulting fracture surfaces were subjected to qualitative and quantitative fractographic examinations. Quantitative fracture analysis included an estimation of crack growth rate (CGR) in different regions. The effect of the microstructural features on fatigue crack growth was examined. It was observed that in stage II (crack growth region), the failure mode changes from intergranular to transgranular as the stress level increases. In the region of intergranular failure the localized brittle failure was observed and fatigue striations are difficult to reveal. However, in the region of transgranular failure the crack path is independent of the microstructural features. In this region, localized ductile failure mode was observed and well defined fatigue striations were present in the wake of fatigue crack. The effect of interaction of growing fatigue crack with microstructural features was not substantial. The final fracture (stage III) was ductile in all the cases.

  19. Biological computation

    CERN Document Server

    Lamm, Ehud

    2011-01-01

    Introduction and Biological BackgroundBiological ComputationThe Influence of Biology on Mathematics-Historical ExamplesBiological IntroductionModels and Simulations Cellular Automata Biological BackgroundThe Game of Life General Definition of Cellular Automata One-Dimensional AutomataExamples of Cellular AutomataComparison with a Continuous Mathematical Model Computational UniversalitySelf-Replication Pseudo Code Evolutionary ComputationEvolutionary Biology and Evolutionary ComputationGenetic AlgorithmsExample ApplicationsAnalysis of the Behavior of Genetic AlgorithmsLamarckian Evolution Genet

  20. Comparing three different approaches to the measurement of needs concerning fatigue in patients with advanced cancer

    DEFF Research Database (Denmark)

    Madsen, Ulla Riis; Groenvold, Mogens; Petersen, Morten Aagaard;

    2015-01-01

    -sectional nationwide survey, patients were asked about their needs concerning fatigue in three different ways: Fatigue intensity was measured with the European Organisation for Research and Treatment of Cancer quality of life questionnaire, fatigue burden (the extent fatigue was a problem) and fatigue felt need......: In total, 1447 patients participated (61 %). Of these, 34 % reported at least quite a bit fatigue (intensity), 36 % reported at least quite a bit fatigue burden, and 35 % reported experiencing an unmet need. There was a high correlation between fatigue intensity and fatigue burden (0.91). Fatigue intensity...... was also correlated with experiencing an unmet need and having at least a little fatigue predicted experiencing an unmet need. CONCLUSION: Overall, no matter which approach was used, about a third of the patients had a need concerning fatigue. In nearly all cases, patients who had fatigue also experienced...

  1. 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)

  2. Creep fatigue damage under multiaxial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lobitz, D.W.; Nickell, R.E.

    1977-01-01

    When structural components are subjected to severe cyclic loading conditions with intermittent periods of sustained loading at elevated temperature, the designer must guard against a failure mode caused by the interaction of time-dependent and time-independent deformation. This phenomena is referred to as creep-fatigue interaction. The most elementary form of interaction theory (called linear damage summation) is now embodied in the ASME Boiler and Pressure Vessel Code. In recent years, a competitor for the linear damage summation theory has emerged, called strainrange partitioning. This procedure is based upon the visualization of the cyclic strain in a uniaxial creep-fatigue test as a hysteresis loop, with the inelastic strains in the loop counter-balanced in one of two ways. The two theories are compared and contrasted in terms of ease of use, possible inconsistencies, and component life prediction. Future work to further test the damage theories is recommended. (TFD)

  3. 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.

  4. Fatigue design of hydraulic turbine runners

    Energy Technology Data Exchange (ETDEWEB)

    Huth, Hans-Joerg

    2005-07-01

    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 under a constant stress amplitude equal to that at the most highly loaded location at the welded joint between the blade and the band or crown of a Francis turbine runner yields a conservative estimate of the life of the runner. A more accurate prediction of fatigue life is obtained by considering the growth of a crack in the real, inhomogeneous stress field. For an idealised T-joint under pure bending, the stress field has been determined by means of plane strain finite element analysis. Finite element models of the entire Francis runner are built with respect to the calculation of fluid dynamic properties. Since in these models geometry transitions are modelled as a sharp notch, both a finite and a zero transition radius have been modelled, and the influence of the mesh size on the maximum stress has been investigated. For relatively small cracks, it is shown that the structural component geometry does not remarkably influence the stress intensity factor values, provided that the stress field in the vicinity of the crack is approximately the same. Therefore, in order to simplify the stress intensity factor retrieval and to generate a solution of extended applicability, a cracked finite-thickness plate is examined instead of the actual T-joint geometry. The stress intensity factors along the front of a semi-elliptical surface crack in such a plate are determined by means of an analysis using finite quarter-point wedge elements for different elementary loading conditions that can

  5. 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.

  6. 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.

  7. 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)

  8. 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...

  9. 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...

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Compassion Fatigue: Description, Causes and Prevention

    Directory of Open Access Journals (Sweden)

    Duygu Hicdurmaz

    2015-09-01

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

  16. 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.

  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. 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.

  20. 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.

  1. 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.

  2. Fatigue Analysis of Load-Carrying Fillet Welds

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tychsen, Jesper; Andersen, Jens Ulfkjær;

    2006-01-01

    is a doubler plate connection, which is often applied in connection with modifications of offshore structures. As a part of the present work, fatigue tests have been performed with test specimens fabricated by the current industry standard for welded offshore steel structures. The fatigue tests show...... that the degree of bending (DOB) has an influence on the fatigue lifetime. The fatigue lifetime decreases significantly when increasing the bending stress. In order to take into account the effect of the bending, a new fatigue stress definition applicable for fillet welds failing through the weld is presented....... Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve....

  3. FATIGUE CRACK PROPAGATION THROUGH AUSTEMPERED DUCTILE IRON MICROSTRUCTURE

    Directory of Open Access Journals (Sweden)

    Lukáš Bubenko

    2010-10-01

    Full Text Available Austempered ductile iron (ADI has a wide range of application, particularly for castings used in automotive and earth moving machinery industries. These components are usually subjected to variable dynamic loading that may promote initiation and propagation of fatigue cracks up to final fracture. Thus, it is important to determine the fatigue crack propagation behavior of ADI. Since fatigue crack growth rate (da/dN vs. stress intensity factor K data describe fatigue crack propagation resistance and fatigue durability of structural materials, da/dN vs. Ka curves of ADI 1050 are reported here. The threshold amplitude of stress intensity factor Kath is also determined. Finally, the influence of stress intensity factor amplitude to the character of fatigue crack propagation through the ADI microstructure is described.

  4. Fractographic analysis of fatigue damage in 7000 aluminium alloys.

    Science.gov (United States)

    Cvijović, Z; Vratnica, M; Gerić, K

    2008-12-01

    In this paper, an attempt is made to correlate the fatigue damage in 7000 aluminium alloys with different impurity contents to the microstructural features and to explain their interdependence through fractographic observations. The Paris constants of these alloys in the form of hot-forged plates subjected to the overaged T73 temper are evaluated and differences in the fatigue crack growth rate described by striation spacing measurements. Scanning electron microscopy analysis of fatigue fracture surfaces revealed that the type and morphological parameters of coarse intermetallic particles play a critical role in fatigue crack growth behaviour. The elemental distribution determined by means of energy-dispersive spectroscopy analysis showed that the fractured particles accelerating the crack advances are larger particles of Fe-rich phases. The fatigue crack growth rate increases considerably with increasing amounts of these particles. The smaller eta, S and Mg(2)Si particles contribute beneficially to fatigue life.

  5. Fatigue crack arrest in a self-healing polymer composite

    Energy Technology Data Exchange (ETDEWEB)

    Brown, E. N. (Eric N.); White, S. R. (Scott R.); Sottos, Nancy R.

    2004-01-01

    A comprehensive experimental program is performed to assess the in situ fatigue behavior of a self-healing polymer. A fatigue-life-extension protocol is established for characterizing healing efficiency of the self-healing epoxy under cyclic loading. At moderate {Delta}K{sub I} and at high {Delta}K{sub I}, when a rest period is employed, in situ healing extends fatigue life though temporary crack arrest and retardation. In situ self-healing permanently arrests crack growth at low {delta}K{sub I} and at moderate {Delta}K{sub I}, when a rest period is employed. Fatigue crack retardation and arrest result from two primary crack-tip shielding mechanisms: hydrodynamic pressure in the viscous healing agent and artificial crack closure. Application of self-healing functionality to fatigue slows the crack growth rate and increases the fatigue threshold.

  6. 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.

  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. 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...

  10. 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...

  11. 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....

  12. 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.

  13. 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 ...

  14. Neural effects of prolonged mental fatigue: a magnetoencephalography study.

    Science.gov (United States)

    Ishii, Akira; Tanaka, Masaaki; Shigihara, Yoshihito; Kanai, Etsuko; Funakura, Masami; Watanabe, Yasuyoshi

    2013-09-01

    Mental fatigue, manifest as a reduced efficiency for mental work load, is prevalent in modern society. It is important to understand the neural mechanisms of mental fatigue and to develop appropriate methods for evaluating mental fatigue. In this study we quantified the effect of a long-duration mental fatigue-inducing task on neural activity. We used magnetoencephalography (MEG) to examine the time course change of neural activity over the long duration of the task trials. Nine healthy male volunteers participated in this study. They performed two mental fatigue-inducing tasks on separate days. The order of task presentation was randomized in a single-blinded, crossover fashion. Each task consisted of 25-min mental fatigue-inducing 0- or 2-back task session for three times. Subjective rating of mental fatigue sensation and electrocardiogram, and resting state MEG measurements were performed just before and after each task session. MEG data were analyzed using narrow-band adaptive spatial filtering methods. Alpha band (8-13 Hz) power in the visual cortex decreased after performing the mental fatigue-inducing tasks, and the decrease of alpha power was greater when they performed 2-back task trials. The decrease in alpha power was positively associated with the self-reported level of mental fatigue sensation and sympathetic nerve activity level. These results demonstrate that performing the prolonged mental fatigue-inducing task causes overactivation of the visual cortex, manifest as decreased alpha power in this brain region. Our results increase understanding of the neural mechanisms of mental fatigue and can be used to develop new quantitative methods to assess mental fatigue.

  15. 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...

  16. Probabilistic Approach to Fatigue Assessment for Stay Cables

    DEFF Research Database (Denmark)

    Baussaron, Julien; Sørensen, John Dalsgaard; Toft, Henrik Stensgaard;

    2013-01-01

    points of the structures, develop into critical cracks and failure due to fatigue. Many parameters used for predicting times to failure of structure due to fatigue are uncertain and their variations have a big influence on the real lifetime. This paper will focus on a global methodology to take...... of the material. Probabilistic Wöhler curves are fitted using available data, and used to represent the variability of material fatigue behaviour. Finally, the reliability is assessed using Monte Carlo simulations....

  17. CNS fatigue provoked by prolonged exercise in the heat

    DEFF Research Database (Denmark)

    Nybo, Lars

    2010-01-01

    in the heat, but pharmacological manipulations provide evidence for involvement of the dopaminergic system and other monoamines. Thus, enhanced dopaminergic activity may counteract hyperthermia mediated central fatigue and improve performance in the heat, while noradrenaline re-uptake inhibition appears...... to aggravate central fatigue and degrade exercise performance. Hyperthermia mediated central fatigue may include other cerebral perturbations such as reduced perfusion of the brain, accumulation of ammonia or depletion of neuronal energy stores, but further research is needed to elucidate their possible...

  18. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

    Højerslev, Christian; Carstensen, Jesper V.; Brøndsted, Povl;

    2002-01-01

    The influence of microstructure on fatigue crack initiation and crack growth of a hardened and tempered high speed steel was investigated. The evolution of fatigue cracks was followed in four point bending at room temperature. It was found that a carbide damage zone exists above a threshold load ...... microns in front of the fatigue crack tip, which is comparable with the relevant mean free carbide spacing....

  19. [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

  20. 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...

  1. 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.

  2. 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

  3. 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.

  4. Relationship between fatigue life in the creep-fatigue region and stress-strain response

    Science.gov (United States)

    Berkovits, A.; Nadiv, S.

    1988-01-01

    On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the two more pairs of stress strain parameters must be ascertained.

  5. 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....

  6. Fatigue Life Assessment of Selected Engineering Materials Based on Modified Low-Cycle Fatigue Test

    Directory of Open Access Journals (Sweden)

    M. Maj

    2013-01-01

    Full Text Available In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade.The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF, which enables the determination of parameters resulting fromthe Manson-Coffin-Morrow relationship.The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidalgraphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties, confirmed also smallvariations in the geometrical parameters of graphite related with its content and morphological features.

  7. 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)

  8. Cryogenic fatigue behaviour of steel-concrete composite structures

    Energy Technology Data Exchange (ETDEWEB)

    Hou Wenqi; Ye Meixin; Zhang Yezhi, E-mail: 40951515@qq.com [School of Civil Engineering, Central South University, Changsha 410075 (China)

    2011-07-19

    Aiming to the application of steel-concrete composite structures in extremely cold zones, a special cryogenic test equipment was developed to simulate the temperature environment along Qinghai-Tibet railway, and cryogenic fatigue tests were carried out on 10 specimens composed of 14MnNbq steel, {Phi}22 studs and C50 concrete. Taking temperature variation and steel rolling direction into consideration, fatigue failure mode and fatigue behaviour of the composite structures under low-temperature were well studied. Test results were compared with that under normal temperature. Results showed that composite structures performed better cryogenic fatigue performance with temperature ranging from 0 deg. C to -50 deg. C, the lower the temperature is, the longer the fatigue life tends to be. This is due to the excellent cryogenic fatigue performance of 14MnNbq steel. Steel rolling direction has important influence on the fatigue behaviour of composite structures, specimens with along rolling steel girders showed longer fatigue life than those with transverse rolling steel girders. Welding {Phi}22 studs on 14MnNbq steel girders showed no influence on the material quality of 14MnNbq steel. For safety purpose, fatigue bearing capacity of {Phi}22 studs in Qinghai-Tibet railway composite bridges was suggested to be 80% of that under normal temperature.

  9. Influence of Rare Earths on Contact Fatigue of Rail Steels

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Rail/wheel contact fatigue of NbRE rail, Nb rail and U74 rail was investigated using contact fatigue tester. Microstructure and morphology as well as microhardness in the fatigue profiles were analyzed by scanning electron microscope and Vickers hardness respectively. The experimental results show that rare earths are able to delay the initiation and the propagation of fatigue cracks and postpone the surface shelling or spalling, even more, to reduce the crack propagation angle and the crack propagation depth in steady state as well as the plastic deformation area, and to improve work-hardening of the rail steel.

  10. Behaviour of Corroded Stud Shear Connectors under Fatigue Loading

    OpenAIRE

    Chen, Ju; Jiang, Ao-Yu; Jin, Wei-Liang

    2016-01-01

    Experimental investigation was conducted on corroded composite push-out specimens to study the behavior of shear studs subjected to fatigue loading. A total of eight standard EC4 push-out specimens were tested. The expected corrosion rate of test specimens ranged from 0 to 50%. The main purpose of these tests was to determine the fatigue life and the reduction effect caused by the corrosion on the fatigue life. The effect of corrosion on the fatigue crack, load-slip curves, and failure modes ...

  11. Shear/compressive fatigue of insulation systems at low temperatures

    Science.gov (United States)

    Reed, R. P.; Fabian, P. E.; Bauer-McDaniel, T. S.

    Fatigue tests under combined compression and shear loading were conducted at 76 K on four types of insulation system fabricated by vacuum-pressure impregnation and pre-impregnation. Fixtures developed for static tests with loading angles of 15 °, 45 °, 75 °, 84 ° and 90 ° were used to apply cyclic loads. Fatigue tests were conducted for each material over a fatigue-life range from 1 to 10 6 cycles. The constructed fatigue S-N curves were approximately linear for all materials; data variability was remarkably low.

  12. Cryogenic fatigue behaviour of steel-concrete composite structures

    International Nuclear Information System (INIS)

    Aiming to the application of steel-concrete composite structures in extremely cold zones, a special cryogenic test equipment was developed to simulate the temperature environment along Qinghai-Tibet railway, and cryogenic fatigue tests were carried out on 10 specimens composed of 14MnNbq steel, Φ22 studs and C50 concrete. Taking temperature variation and steel rolling direction into consideration, fatigue failure mode and fatigue behaviour of the composite structures under low-temperature were well studied. Test results were compared with that under normal temperature. Results showed that composite structures performed better cryogenic fatigue performance with temperature ranging from 0 deg. C to -50 deg. C, the lower the temperature is, the longer the fatigue life tends to be. This is due to the excellent cryogenic fatigue performance of 14MnNbq steel. Steel rolling direction has important influence on the fatigue behaviour of composite structures, specimens with along rolling steel girders showed longer fatigue life than those with transverse rolling steel girders. Welding Φ22 studs on 14MnNbq steel girders showed no influence on the material quality of 14MnNbq steel. For safety purpose, fatigue bearing capacity of Φ22 studs in Qinghai-Tibet railway composite bridges was suggested to be 80% of that under normal temperature.

  13. Inclusion of fatigue effects in human reliability analysis

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, Candice D. [Vanderbilt University, Nashville, TN (United States); Mahadevan, Sankaran, E-mail: sankaran.mahadevan@vanderbilt.edu [Vanderbilt University, Nashville, TN (United States)

    2011-11-15

    The effect of fatigue on human performance has been observed to be an important factor in many industrial accidents. However, defining and measuring fatigue is not easily accomplished. This creates difficulties in including fatigue effects in probabilistic risk assessments (PRA) of complex engineering systems that seek to include human reliability analysis (HRA). Thus the objectives of this paper are to discuss (1) the importance of the effects of fatigue on performance, (2) the difficulties associated with defining and measuring fatigue, (3) the current status of inclusion of fatigue in HRA methods, and (4) the future directions and challenges for the inclusion of fatigue, specifically sleep deprivation, in HRA. - Highlights: >We highlight the need for fatigue and sleep deprivation effects on performance to be included in human reliability analysis (HRA) methods. Current methods do not explicitly include sleep deprivation effects. > We discuss the difficulties in defining and measuring fatigue. > We review sleep deprivation research, and discuss the limitations and future needs of the current HRA methods.

  14. Fatigue crack propagation in turbine disks of EI698 superalloy

    OpenAIRE

    A.A. Shanyavskiy

    2013-01-01

    In-service fatigue cracking of turbine disks of EI698 superalloy is discussed based on crack growth analyses. In the bolt joint for disks to shaft connecting there is high level of stress-state, which directed to earlier in-disks fatigue crack origination in low-cycle-fatigue regime. Fracture surface pattern such as fatigue striations were used for their spacing measurement and crack growth duration estimating. Developed disk tests on a special bench by the equivalent program to in-service cy...

  15. Fatigue in Patients with Parkinson’s Disease

    Directory of Open Access Journals (Sweden)

    Kazuo Abe

    2000-01-01

    Full Text Available 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: Patients with PD had normal cognitive function as judged by the MMSE, but showed significantly high scores with the fatigue and depression scales in comparison to controls (p. There was no significant correlation between the depression scale and the fatigue scale, or between the degree of disability and the fatigue scale in patients with PD, although a significant correlation existed between the depression scale and the fatigue scale in controls. With SPECT, a significant correlation was found between the fatigue scale and the reduction of perfusion in the frontal lobe (p in patients with PD. Conclusions: The present study suggested that sense of fatigue in patients with PD might be associated with frontal lobe dysfunction.

  16. Statistical optimisation techniques in fatigue signal editing problem

    Energy Technology Data Exchange (ETDEWEB)

    Nopiah, Z. M.; Osman, M. H. [Fundamental Engineering Studies Unit Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM (Malaysia); Baharin, N.; Abdullah, S. [Department of Mechanical and Materials Engineering Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM (Malaysia)

    2015-02-03

    Success in fatigue signal editing is determined by the level of length reduction without compromising statistical constraints. A great reduction rate can be achieved by removing small amplitude cycles from the recorded signal. The long recorded signal sometimes renders the cycle-to-cycle editing process daunting. This has encouraged researchers to focus on the segment-based approach. This paper discusses joint application of the Running Damage Extraction (RDE) technique and single constrained Genetic Algorithm (GA) in fatigue signal editing optimisation.. In the first section, the RDE technique is used to restructure and summarise the fatigue strain. This technique combines the overlapping window and fatigue strain-life models. It is designed to identify and isolate the fatigue events that exist in the variable amplitude strain data into different segments whereby the retention of statistical parameters and the vibration energy are considered. In the second section, the fatigue data editing problem is formulated as a constrained single optimisation problem that can be solved using GA method. The GA produces the shortest edited fatigue signal by selecting appropriate segments from a pool of labelling segments. Challenges arise due to constraints on the segment selection by deviation level over three signal properties, namely cumulative fatigue damage, root mean square and kurtosis values. Experimental results over several case studies show that the idea of solving fatigue signal editing within a framework of optimisation is effective and automatic, and that the GA is robust for constrained segment selection.

  17. Hydrogen effect on fatigue threshold of structural steel

    International Nuclear Information System (INIS)

    A number of effects of hydrogen both as gas and dissolved in metal on the threshold fatigue crack growth in steels has been analysed: the effect of gas adsorption on the effective fatigue threshold ΔKtheff fatigue crack growth in structural steels in dependence of its strength and test temperature; use of ΔKtheff parameter for evaluation of the high temperature degradation of steels during operation; existence of three factors of ambiguous hydrogen influence on ΔKtheff ; a geometric model of crack closure in the hydrogenated steel caused by fracture surface roughness and the longitudinal shear; scale effect on the fatigue threshold. (author)

  18. Fatigue of weldments in nuclear pressure vessels and piping

    International Nuclear Information System (INIS)

    Current (ASME) Code fatigue design rules for nuclear pressure vessels and piping include no special considerations for weldments other than purely geometric factors. Research programs aimed at nonnuclear applications have found weldments to display fatigue behavior inferior to that of pure base material. Available information on fatigue of weldments relevant to nuclear pressure vessels and piping was reviewed and determined changes in the current design rules appear to be dictated by the available information. Information was obtained and summarized and stored in a computerized data management system to facilitate correlation of facts and development of conclusions. Significant areas where development of additional data would substantially increase the ability to judge the adequacy of the current ASME design rules include: a better understanding of the relative importance of crack initiation and crack propagation to fatigue life; additional fatigue data for prototypic commercial weldments, including cumulative damage; properties of repair welds; significance of reheat cracks; quantitative effect of Code-allowable weld defects; and the effect of variable microstructure across the weld joint. Based on the information that is available, there is no evidence that the ASME Code fatigue design procedures need to be changed at this time. The current ASME design procedures, which form the general basis for fatigue evaluation both in the US and abroad are reviewed. Included is a review of various factors that influence the fatigue of weldments and of service experience with nuclear systems regarding fatigue of weldments. Research programs that may contribute to available information are reviewed

  19. Fatigue test of RC beams strengthened with prestressed CFLs

    Science.gov (United States)

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

    2008-11-01

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

  20. Fatigue of continuous fiber reinforced titanium matrix composites

    Science.gov (United States)

    Johnson, W. S.

    1991-01-01

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

  1. Arterial Elasticity, Strength, Fatigue, and Endurance in Older Women

    Directory of Open Access Journals (Sweden)

    Gary R. Hunter

    2014-01-01

    Full Text Available Arterial health may influence muscle function in older adults. Study purpose was to determine whether arterial elasticity is related to strength, central and peripheral fatigue, fatigue at rest, and treadmill endurance. Subjects were 91 healthy women aged >60. Treadmill endurance and maximal oxygen uptake (VO2 max were measured. Peripheral and central fatigue for the knee extensors were evaluated using two isometric fatigue tests (one voluntary and one adding electrical stimulation. Arterial elasticity was determined using radial artery pulse wave analysis. Linear multiple regression was used in statistical analysis. Large artery elasticity was associated with central fatigue (P<0.01 and treadmill endurance (P<0.02 after adjusting for VO2 max and knee extension strength. Subjective fatigue at rest was related to large artery elasticity after adjusting for ethnic origin (<0.02. Strength was significantly related to small artery elasticity after adjusting for ethnic origin, leg lean tissue, age, and blood pressure. Arterial elasticity is independently related to strength and fatigue in older women, especially in the central nervous system where arterial elasticity is independently related to perceptions of fatigue at rest and central fatigue. These results suggest that arterial health may be involved with the ability of the central nervous system to activate muscle in older women.

  2. Altered resting brain connectivity in persistent cancer related fatigue

    Directory of Open Access Journals (Sweden)

    Johnson P. Hampson

    2015-01-01

    Full Text Available There is an estimated 3 million women in the US living as breast cancer survivors and persistent cancer related fatigue (PCRF disrupts the lives of an estimated 30% of these women. PCRF is associated with decreased quality of life, decreased sleep quality, impaired cognition and depression. The mechanisms of cancer related fatigue are not well understood; however, preliminary findings indicate dysfunctional activity in the brain as a potential factor. Here we investigate the relationship between PCRF on intrinsic resting state connectivity in this population. Twenty-three age matched breast cancer survivors (15 fatigued and 8 non-fatigued who completed all cancer-related treatments at least 12 weeks prior to the study, were recruited to undergo functional connectivity magnetic resonance imaging (fcMRI. Intrinsic resting state networks were examined with both seed based and independent component analysis methods. Comparisons of brain connectivity patterns between groups as well as correlations with self-reported fatigue symptoms were performed. Fatigued patients displayed greater left inferior parietal lobule to superior frontal gyrus connectivity as compared to non-fatigued patients (P < 0.05 FDR corrected. This enhanced connectivity was associated with increased physical fatigue (P = 0.04, r = 0.52 and poor sleep quality (P = 0.04, r = 0.52 in the fatigued group. In contrast greater connectivity in the non-fatigued group was found between the right precuneus to the periaqueductal gray as well as the left IPL to subgenual cortex (P < 0.05 FDR corrected. Mental fatigue scores were associated with greater default mode network (DMN connectivity to the superior frontal gyrus (P = 0.05 FDR corrected among fatigued subjects (r = 0.82 and less connectivity in the non-fatigued group (r = −0.88. These findings indicate that there is enhanced intrinsic DMN connectivity to the frontal gyrus in breast cancer survivors with persistent

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

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2013-01-01

    Reinforced Concrete Slab Foundation (RCSF) is the most common onshore wind turbine foundation type installed by the wind industry around the world. Fatigue cracks in a RCSF are an important issue to be considered by the designers. Causes and consequences of the cracks due to fatigue damage in RCSFs...... are discussed in this paper. A probabilistic fatigue model for a RCSF is established which makes a rational treatment of the uncertainties involved in the complex interaction between fatigue cyclic loads and reinforced concrete. Design and limit state equations are established considering concrete shear...

  4. Fatigue damage propagation in unidirectional glass fibre reinforced composites

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg; Alzamora Guzman, Vladimir Joel; Østergaard, R.C.;

    2012-01-01

    Damage progression in unidirectional glass fibre reinforced composites exposed to tension fatigue is investigated, and a quantitative explanation is given for the observed stiffness loss. The stiffness degradation during fatigue is directly related to fibre breaks in the load-carrying axial fibre...... bundles. The underlying mechanisms are examined using digital microscopy, and it is postulated that fatigue damage initiates due to stress concentrations between the backing (transverse) layer and the unidirectional layer, followed by a cyclic fretting and axial fibre debonding. This fretting mechanism...... needs further attention and understanding in order to improve the fatigue life-time of glass fibre reinforced composites....

  5. Thermal emission in fatigue described by power laws

    Directory of Open Access Journals (Sweden)

    Gallinatti A.E.

    2010-06-01

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

  6. Fatigue and ultrasonic testing of epoxy-glass composites

    Directory of Open Access Journals (Sweden)

    M. Rojek

    2007-01-01

    Full Text Available Purpose: The purpose of this paper was to find relationship between the degree of strength degradation causedby fatigue and the changes of ultrasonic wave characteristics such as wave velocity and damping coefficient.Design/methodology/approach: Epoxy-glass composites were subjected to oscillatory bending loadings withconstant deflection. During fatigue procedure the force needed to achieve constant deflection was measured.During fatigue tests samples were subjected to ultrasonic tests. Additionally before fatigue test and after 300000, 850 000 and 1 900 000 cycles parts of samples were subjected to destructive bending test.Findings: A good correlation between velocity of ultrasonic wave propagation and the degree of strengthdegradation of epoxy-glass composites caused by fatigue was found. Ultrasounds can be applied as effectivetool to assessment of fatigue degradation of polymer composites.Research limitations/implications: Achieved results showed that research have to be continued. Fatigue withother loading conditions and for other composite materials is planned.Practical implications: The results of present research can be applied to elaboration of non-destructive methodof measurement of the degree of fatigue degradation of polymer composites.Originality/value: Presented correlation between ultrasound wave characteristics and the degree of strengthdegradation caused by fatigue is original value of this paper.

  7. Method and procedure of fatigue analysis for nuclear equipment

    International Nuclear Information System (INIS)

    As an example, the fatigue analysis for the upper head of the pressurizer in one NPP was carried out by using ANSYS, a finite element method analysis software. According to RCC-M code, only two kinds of typical transients of temperature and pressure were considered in the fatigue analysis. Meanwhile, the influence of earthquake was taken into account. The method and procedure of fatigue analysis for nuclear safety equipment were described in detail. This paper provides a reference for fatigue analysis and assessment of nuclear safety grade equipment and pipe. (authors)

  8. Flex Fatigue Property and Fractography of High Performance Fibers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua-peng; LIU Xiao-yan; SHI Mei-wu; ZHANG Jian-chun; LAI Kan; WANG Shan-yuan

    2002-01-01

    The effects of pre-stress and bending angle on the flex fatigue lifetimes of para- aramds have been studied choosing the Twaron 2000 high performance filament as the studying subject by use of the self-developed flex fatigue apparatus. The fractography of the fatiguebreaking end of the single filaments has been obtained and the fatigue-breaking mechanisms have been analyzed using the LM and SEM. The differences of the fatigue properties and fractography of a variety of high performance fibers such as Kevlar 129, Kevlar 29 and UHMW PE have been discussed.

  9. Do negative aspects of social relations influence fatigue?

    DEFF Research Database (Denmark)

    Ekmann, Anette; Avlund, Kirsten; Osler, Merete;

    2012-01-01

    Fatigue is a common complaint among young and old adults and may be associated with negative aspects of social relations. Hence, the purpose of this study was to explore the association between demands from and conflicts with different sources of social relations and fatigue.......Fatigue is a common complaint among young and old adults and may be associated with negative aspects of social relations. Hence, the purpose of this study was to explore the association between demands from and conflicts with different sources of social relations and fatigue....

  10. Method and data analysis example of fatigue tests

    International Nuclear Information System (INIS)

    In the design and operation of a nuclear fusion reactor, it is important to accurately assess the fatigue life. Fatigue life is evaluated by preparing a database on the relationship between the added stress / strain amplitude and the number of cycles to failure based on the fatigue tests on standard specimens, and by comparing this relationship with the generated stress / strain of the actual constructions. This paper mainly chooses low-cycle fatigue as an object, and explains standard test methods, fatigue limit, life prediction formula and the like. Using reduced-activation ferrite steel F82H as a material, strain controlled low-cycle fatigue test was performed under room temperature atmosphere. From these results, the relationship between strain and the number of cycles to failure was analyzed. It was found that the relationship is asymptotic to the formula of Coffin-Manson Law under high-strain (low-cycle condition), and asymptotic to the formula of Basquin Law under low-strain (high-cycle condition). For F82H to be used for the blanket of a nuclear fusion prototype reactor, the arrangement of fatigue life data up to about 700°C and the establishment of optimal fatigue design curves are urgent tasks. As for fusion reactor structural materials, the evaluation of neutron irradiation effect on fatigue damage behavior and life is indispensable. For this purpose, it is necessary to establish standardized testing techniques when applied to small specimens. (A.O.)

  11. Statistical optimisation techniques in fatigue signal editing problem

    International Nuclear Information System (INIS)

    Success in fatigue signal editing is determined by the level of length reduction without compromising statistical constraints. A great reduction rate can be achieved by removing small amplitude cycles from the recorded signal. The long recorded signal sometimes renders the cycle-to-cycle editing process daunting. This has encouraged researchers to focus on the segment-based approach. This paper discusses joint application of the Running Damage Extraction (RDE) technique and single constrained Genetic Algorithm (GA) in fatigue signal editing optimisation.. In the first section, the RDE technique is used to restructure and summarise the fatigue strain. This technique combines the overlapping window and fatigue strain-life models. It is designed to identify and isolate the fatigue events that exist in the variable amplitude strain data into different segments whereby the retention of statistical parameters and the vibration energy are considered. In the second section, the fatigue data editing problem is formulated as a constrained single optimisation problem that can be solved using GA method. The GA produces the shortest edited fatigue signal by selecting appropriate segments from a pool of labelling segments. Challenges arise due to constraints on the segment selection by deviation level over three signal properties, namely cumulative fatigue damage, root mean square and kurtosis values. Experimental results over several case studies show that the idea of solving fatigue signal editing within a framework of optimisation is effective and automatic, and that the GA is robust for constrained segment selection

  12. Investigation on fatigue behavior and fatigue crack growth of spring steel. Part I: Wohler curve and fracture surfaces

    International Nuclear Information System (INIS)

    Full text: Fatigue behavior of spring steel at different stress ranges was investigated. The specimens were machined in hour-glass shape with polished surface and were subjected to symmetric cyclic rotating-b ending fatigue in air and room temperature to fracture. Fatigue life time data was obtained and Wohler curve of the investigated steel at different conditions is plotted. A mathematical description of the obtained results is presented. The fatigue test results are filled out with images and analysis of the fracture surface madden with the help of scanning electron microscope. A replication technique is used for short fatigue-crack growth monitoring for two specimens. The experimental data are presented in plots 'Crack lengths, a - cycles, N'. key words: rotating-bending fatigue, Wohler curve, fractography, crack growth; crack path

  13. Fatigue-Related Gene Networks Identified in CD14+ Cells Isolated From HIV-Infected Patients—Part II: Statistical Analysis

    Science.gov (United States)

    Voss, Joachim G.; Dobra, Adrian; Morse, Caryn; Kovacs, Joseph A.; Raju, Raghavan; Danner, Robert L.; Munson, Peter J.; Logan, Carolea; Rangel, Zoila; Adelsberger, Joseph W.; McLaughlin, Mary; Adams, Larry D.; Dalakas, Marinos C.

    2012-01-01

    Purpose In limited samples of valuable biological tissues, univariate ranking methods of microarray analyses often fail to show significant differences among expression profiles. In order to allow for hypothesis generation, novel statistical modeling systems can be greatly beneficial. The authors applied new statistical approaches to solve the issue of limited experimental data to generate new hypotheses in CD14+ cells of patients with HIV-related fatigue (HRF) and healthy controls. Methodology We compared gene expression profiles of CD14+ cells of nucleoside reverse transcriptase inhibitor (NRTI)-treated HIV patients with low versus high fatigue to healthy controls (n = 5 each). With novel Bayesian modeling procedures, the authors identified 32 genes predictive of low versus high fatigue and 33 genes predictive of healthy versus HIV infection. Sparse association and liquid association networks further elucidated the possible biological pathways in which these genes are involved. Relevance for nursing practice Genetic networks developed in a comprehensive Bayesian framework from small sample sizes allow nursing researchers to design future research approaches to address such issues as HRF. Implication for practice The findings from this pilot study may take us one step closer to the development of useful biomarker targets for fatigue status. Specific and reliable tests are needed to diagnosis, monitor and treat fatigue and mitochondrial dysfunction. PMID:22084402

  14. Interaction of Corrosion-Cumulative Fatigue and Shot Peening of 1100-H12 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Alalkawi H.J.M

    2015-03-01

    Full Text Available Corrosion-fatigue occurs by the combined actions of cyclic loading and corrosive environment. The effect of shot peening on cumulative corrosion-fatigue life of 1100-H12 Al alloy was investigated. Before fatigue testing, specimens were submerged in 3.5%NaCl solution for 71 days. Constant fatigue tests were performed with and without corrosive environment. Cumulative corrosion-fatigue tests were also carried out in order to determine the fatigue life before and after shot peening. The constant fatigue life was significantly reduced due to corrosive environment and the endurance fatigue limit was reduced by 13% compared with dry fatigue. In case of shot peening the cumulative , corrosion -fatigue life was increased by a factor of about (2 compared with cumulative corrosion-fatigue life without shot peening.It was found that the CFLIF%(Cumulative Fatigue Life Improvement Factor was about (2-6 due to shot peening surface treatment .

  15. Fucoidan Supplementation Improves Exercise Performance and Exhibits Anti-Fatigue Action in Mice

    Directory of Open Access Journals (Sweden)

    Yi-Ming Chen

    2014-12-01

    Full Text Available Fucoidan (FCD is a well-known bioactive constituent of seaweed extract that possess a wide spectrum of activities in biological systems, including anti-cancer, anti-inflammation and modulation of immune systems. However, evidence on the effects of FCD on exercise performance and physical fatigue is limited. Therefore, we investigated the potential beneficial effects of FCD on ergogenic and anti-fatigue functions following physiological challenge. Male ICR mice from three groups (n = 8 per group were orally administered FCD for 21 days at 0, 310 and 620 mg/kg/day, which were, respectively, designated the vehicle, FCD-1X and FCD-2X groups. The results indicated that the FCD supplementations increased the grip strength (p = 0.0002 and endurance swimming time (p = 0.0195 in a dose-depend manner. FCD treatments also produced dose-dependent decreases in serum levels of lactate (p < 0.0001 and ammonia (p = 0.0025, and also an increase in glucose level (p < 0.0001 after the 15-min swimming test. In addition, FCD supplementation had few subchronic toxic effects. Therefore, we suggest that long-term supplementation with FCD can have a wide spectrum of bioactivities on health promotion, performance improvement and anti-fatigue.

  16. Measuring fatigue in people living with HIV/AIDS: psychometric characteristics of the HIV-Related Fatigue Scale

    OpenAIRE

    BW, Pence; Barroso, J. (José); Leserman, J.; Harmon, J.L.; Salahuddin, N.

    2008-01-01

    In the era of life-prolonging antiretroviral therapy, chronic fatigue is one of the most prevalent and disabling symptoms of people living with HIV/AIDS, yet its measurement remains challenging. No instruments have been developed specifically to describe HIV-related fatigue. We assessed the reliability and construct validity of the HIV-Related Fatigue Scale (HRFS), a 56-item self-report instrument developed through formative qualitative research and designed to measure the intensity and conse...

  17. INVESTIGATION OF THE LOW-CYCLE FATIGUE AND FATIGUE CRACK GROWTH BEHAVIORS OF P91 BASE METAL AND WELD JOINTS

    Institute of Scientific and Technical Information of China (English)

    H.C. Yang; Y. Tu; M.M. Yu; J. Zhao

    2004-01-01

    Low cycle fatigue tests and crack growth propagations tests on P91 pipe base metal and its weld joints were conducted at three different temperatures: room temperature,550℃ and 575℃. The strain-life was analyzed, and the changes in fatigue life behavior and fatigue growth rates with increasing temperature were discussed. The different properties of the base metal and its weld joint have been analyzed.

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

    OpenAIRE

    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 increase in physical activity. METHOD: Three randomized controlled trials were reanalysed, previously conducted to evaluate the efficacy of CBT for CFS. In all samples, actigraphy was used to assess the...

  19. Fatigue in the Danish general population. Influence of sociodemographic factors and disease

    OpenAIRE

    Watt, T.; Groenvold, M.; Bjorner, J. B.; Noerholm, V.; Rasmussen, N; P. Bech

    2000-01-01

    OBJECTIVE—To measure the levels of fatigue in the general population, and to examine how disease and sociodemographic factors influence fatigue.
DESIGN—Cross sectional questionnaire study in the Danish general population.
SUBJECTS—A random, age stratified sample of 1608 people aged 20-77 with an equal gender distribution (response rate 67%).
MAIN OUTCOME MEASURES—Five fatigue scales from the questionnaire Multidimensional Fatigue Inventory: General Fatigue, Physical Fatigue, Reduced Activity,...

  20. Effect of processing, sterilization and crosslinking on UHMWPE fatigue fracture and fatigue wear mechanisms in joint arthroplasty.

    Science.gov (United States)

    Ansari, Farzana; Ries, Michael D; Pruitt, Lisa

    2016-01-01

    Ultra high molecular weight polyethylene (UHMWPE) has been used as a bearing surface in total joint replacements (TJR) for nearly five decades. This semi-crystalline polymer has extraordinary energetic toughness owing to its high molecular weight and entanglement density. However, it is challenged by a need to offer a combined resistance to fatigue, wear and oxidation in vivo. The processing, sterilization treatment, and microstructural tailoring of UHMWPE has evolved considerably in the past 50 years but an optimized microstructure remains elusive. This review seeks to provide an overview of this processing history to address two primary questions: First, how does microstructure affect fatigue fracture and fatigue wear mechanisms in UHMWPE? And second, can microstructure be optimized to provide resistance to fatigue, oxidation and wear in vivo? Previous literature demonstrates that while crosslinking improves resistance to adhesive/abrasive wear, it also reduces resistance to fatigue crack propagation and fatigue wear by restricting molecular mobility and rendering the polymer more brittle. Crystallinity improves fatigue resistance but generally increases elastic modulus and concomitant contact stresses in vivo. The presence of fusion defects or oxidation reduces further fatigue resistance and enhances fatigue wear. Thus, UHMWPE microstructural evolution comes with trade-offs. Currently there is no singular formulation of UHMWPE that is ideal for all TJR applications.

  1. Effect of processing, sterilization and crosslinking on UHMWPE fatigue fracture and fatigue wear mechanisms in joint arthroplasty.

    Science.gov (United States)

    Ansari, Farzana; Ries, Michael D; Pruitt, Lisa

    2016-01-01

    Ultra high molecular weight polyethylene (UHMWPE) has been used as a bearing surface in total joint replacements (TJR) for nearly five decades. This semi-crystalline polymer has extraordinary energetic toughness owing to its high molecular weight and entanglement density. However, it is challenged by a need to offer a combined resistance to fatigue, wear and oxidation in vivo. The processing, sterilization treatment, and microstructural tailoring of UHMWPE has evolved considerably in the past 50 years but an optimized microstructure remains elusive. This review seeks to provide an overview of this processing history to address two primary questions: First, how does microstructure affect fatigue fracture and fatigue wear mechanisms in UHMWPE? And second, can microstructure be optimized to provide resistance to fatigue, oxidation and wear in vivo? Previous literature demonstrates that while crosslinking improves resistance to adhesive/abrasive wear, it also reduces resistance to fatigue crack propagation and fatigue wear by restricting molecular mobility and rendering the polymer more brittle. Crystallinity improves fatigue resistance but generally increases elastic modulus and concomitant contact stresses in vivo. The presence of fusion defects or oxidation reduces further fatigue resistance and enhances fatigue wear. Thus, UHMWPE microstructural evolution comes with trade-offs. Currently there is no singular formulation of UHMWPE that is ideal for all TJR applications. PMID:26386167

  2. Towards Whole Body Fatigue Assessment of Human Movement: A Fatigue-Tracking System Based on Combined sEMG and Accelerometer Signals

    Directory of Open Access Journals (Sweden)

    Haiwei Dong

    2014-01-01

    Full Text Available This paper proposes a method to assess the overall fatigue of human body movement. First of all, according to previous research regarding localized muscular fatigue, a linear relation is assumed between the mean frequency and the muscular working time when the muscle is experiencing fatigue. This assumption is verified with a rigorous statistical analysis. Based on this proven linearity, localized muscular fatigue is simplified as a linear model. Furthermore, localized muscular fatigue is considered a dynamic process and, hence, the localized fatigue levels are tracked by updating the parameters with the most current surface electromyogram (sEMG measurements. Finally, an overall fatigue level is computed by fusing localized muscular fatigue levels. The developed fatigue-tracking system is evaluated with two fatigue experiments (in which 10 male subjects and seven female subjects participated, including holding self-weight (dip start position training and lifting weight with one arm (arm curl training.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

  4. Fatigue Performance of Powder Metallurgy (PM) Ti-6Al-4V Alloy: A Critical Analysis of Current Fatigue Data and Metallurgical Approaches for Improving Fatigue Strength

    Science.gov (United States)

    Cao, Fei; Ravi Chandran, K. S.

    2016-03-01

    A comprehensive assessment of fatigue performance of powder metallurgy (PM) Ti-6Al-4V alloy, manufactured using various powder-based processing approaches to-date, is performed in this work. The focus is on PM processes that use either blended element (BE) or pre-alloyed (PA) powder as feedstock. Porosity and the microstructure condition have been found to be the two most dominant material variables that control the fatigue strength. The evaluation reveals that the fatigue performance of PM Ti-6Al-4V, in the as-sintered state, is far lower than that in the wrought condition. This is largely caused by residual porosity, even if it is present in small amounts, or, by the coarse lamellar colony microstructure. The fatigue strength is significantly improved by the closure of pores, and it approaches the levels of wrought Ti-6Al-4V alloys, after hot-isostatic-pressing (HIPing). Further thermo-mechanical and heat treatments lead to additional increases in fatigue strength-in one case, a high fatigue strength level, exceeding that of the mill-annealed condition, was achieved. The work identifies the powder, process and microstructure improvements that are necessary for achieving high fatigue strength in powder metallurgical Ti-6Al-4V alloys in order for them to effectively compete with wrought forms. The present findings, gathered from the traditional titanium powder metallurgy, are also directly applicable to additively manufactured titanium, because of the similarities in pores, defects, and microstructures between the two manufacturing processes.

  5. The patient experience of fatigue in motor neurone disease

    Directory of Open Access Journals (Sweden)

    Chris J Gibbons

    2013-10-01

    Full Text Available Aims This paper is a qualitative investigation that aims to investigate the lived experience of fatigue in patients with motor neurone disease – a progressive and fatal neurological condition. Background Fatigue is a disabling symptom in motor neurone disease (MND that affects a large number of patients. However, the term ‘fatigue’ is in itself imprecise, as it remains a phenomenon without a widely accepted medical definition. This study sought to investigate the phenomenon of fatigue from the perspective of the MND patient. Methods Ten patients with MND participated in semi-structured recorded interviews at a regional neuroscience centre in Liverpool, U.K. Transcripts analysis was broadly informed by the principles of interpretative phenomenological analysis (IPA. Findings Fatigue was unanimously explained to be disabling and progressive phenomenon. Participants described two forms of fatigue: whole-body tiredness, or use-dependent reversible muscle weakness related to exertion of limb and bulbar muscles. Both weakness and whole-body tiredness could be experienced simultaneously, and patients used the terms ‘fatigue’ and ‘tiredness’ interchangeably. Alongside descriptions of fatigue themes of Adaptation, Motivation, Avoidance, Frustration and Stress were revealed. Fatigue could be defined as reversible motor weakness and whole-body tiredness that was predominantly brought on by muscular exertion and was partially relieved by rest.Conclusion The results of this study support a multi-dimensional model of fatigue for patients with MND. Fatigue appears to be experienced and explained in two ways, both as an inability to sustain motor function and as a pervasive tiredness. Fatigue was only partially relieved by rest and tended to worsen throughout the day. It is crucial that MND care practitioners and researchers appreciate the semantic dichotomy within fatigue.

  6. Selective effect of physical fatigue on motor imagery accuracy.

    Directory of Open Access Journals (Sweden)

    Franck Di Rienzo

    Full Text Available While the use of motor imagery (the mental representation of an action without overt execution during actual training sessions is usually recommended, experimental studies examining the effect of physical fatigue on subsequent motor imagery performance are sparse and yielded divergent findings. Here, we investigated whether physical fatigue occurring during an intense sport training session affected motor imagery ability. Twelve swimmers (nine males, mean age 15.5 years conducted a 45 min physically-fatiguing protocol where they swam from 70% to 100% of their maximal aerobic speed. We tested motor imagery ability immediately before and after fatigue state. Participants randomly imagined performing a swim turn using internal and external visual imagery. Self-reports ratings, imagery times and electrodermal responses, an index of alertness from the autonomic nervous system, were the dependent variables. Self-reports ratings indicated that participants did not encounter difficulty when performing motor imagery after fatigue. However, motor imagery times were significantly shortened during posttest compared to both pretest and actual turn times, thus indicating reduced timing accuracy. Looking at the selective effect of physical fatigue on external visual imagery did not reveal any difference before and after fatigue, whereas significantly shorter imagined times and electrodermal responses (respectively 15% and 48% decrease, p<0.001 were observed during the posttest for internal visual imagery. A significant correlation (r=0.64; p<0.05 was observed between motor imagery vividness (estimated through imagery questionnaire and autonomic responses during motor imagery after fatigue. These data support that unlike local muscle fatigue, physical fatigue occurring during intense sport training sessions is likely to affect motor imagery accuracy. These results might be explained by the updating of the internal representation of the motor sequence, due to

  7. Cortical Mechanisms of Central Fatigue and Sense of Effort.

    Directory of Open Access Journals (Sweden)

    Simon A Sharples

    Full Text Available The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle activation and fatigue the right first dorsal interosseous (FDI of 12 participants. One protocol was intended to assess the effects of muscle activation with minimal fatigue (control and the other was intended to elicit central fatigue (fatigue. We hypothesized that high frequency repetitive transcranial magnetic stimulation (rTMS of the supplementary motor area (SMA would hasten recovery from central fatigue and offset a fatigue-induced increase in sense of effort by facilitating the primary motor cortex (M1. Constant force-sensation contractions were used to assess sense of effort associated with muscle contraction. Paired-pulse TMS was used to assess intracortical inhibition (ICI and facilitation (ICF in the active M1 and interhemispheric inhibitory (IHI was assessed to determine if compensation occurs via the resting M1. These measures were made during and after the muscle contraction protocols. Corticospinal excitability progressively declined with fatigue in the active hemisphere. ICF increased at task failure and ICI was also reduced at task failure with no changes in IHI found. Although fatigue is associated with progressive reductions in corticospinal excitability, compensatory changes in inhibition and facilitation may act within, but not between hemispheres of the M1. rTMS of the SMA following fatigue enhanced recovery of maximal voluntary force and higher levels of ICF were associated with lower sense of effort following stimulation. rTMS of the SMA may have reduced the amount of upstream drive required to maintain motor output, thus contributing to a lower sense of effort and increased rate of recovery of maximal force.

  8. Cortical Mechanisms of Central Fatigue and Sense of Effort.

    Science.gov (United States)

    Sharples, Simon A; Gould, Jason A; Vandenberk, Michael S; Kalmar, Jayne M

    2016-01-01

    The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle activation and fatigue the right first dorsal interosseous (FDI) of 12 participants. One protocol was intended to assess the effects of muscle activation with minimal fatigue (control) and the other was intended to elicit central fatigue (fatigue). We hypothesized that high frequency repetitive transcranial magnetic stimulation (rTMS) of the supplementary motor area (SMA) would hasten recovery from central fatigue and offset a fatigue-induced increase in sense of effort by facilitating the primary motor cortex (M1). Constant force-sensation contractions were used to assess sense of effort associated with muscle contraction. Paired-pulse TMS was used to assess intracortical inhibition (ICI) and facilitation (ICF) in the active M1 and interhemispheric inhibitory (IHI) was assessed to determine if compensation occurs via the resting M1. These measures were made during and after the muscle contraction protocols. Corticospinal excitability progressively declined with fatigue in the active hemisphere. ICF increased at task failure and ICI was also reduced at task failure with no changes in IHI found. Although fatigue is associated with progressive reductions in corticospinal excitability, compensatory changes in inhibition and facilitation may act within, but not between hemispheres of the M1. rTMS of the SMA following fatigue enhanced recovery of maximal voluntary force and higher levels of ICF were associated with lower sense of effort following stimulation. rTMS of the SMA may have reduced the amount of upstream drive required to maintain motor output, thus contributing to a lower sense of effort and increased rate of recovery of maximal force.

  9. Fatigue life estimation of ultrasonic spot welded Mg alloy joints

    International Nuclear Information System (INIS)

    Highlights: • Fatigue life test of USWed similar Mg alloy was investigated. • USW joints exhibited a superior fatigue life compared with other welding processes. • Life prediction model agreed fairly well with the obtained experimental results. • The fatigue failure mode changed with decreasing cyclic load level. - Abstract: Lightweight magnesium alloys are increasingly used in automotive and other transportation industries for weight reduction and fuel efficiency improvement. The structural application of magnesium components requires proper welding and fatigue resistance to guarantee their durability and safety. The objective of this investigation was to identify failure mode and estimate fatigue life of ultrasonic spot welded (USWed) lap joints of an AZ31B-H24 magnesium alloy. It was observed that the solid-state USWed joints exhibited a superior fatigue life compared with other welding processes. Fatigue failure mode changed from interfacial failure to transverse-through-thickness crack growth with decreasing cyclic load level, depending on the welding energy. Fatigue crack initiation and propagation occurred from both the notch tip inside the faying surface and the edge of sonotrode indentation-footprints due to the presence of stress concentration. A life prediction model for the spot welded lap joints developed by Newman and Dowling was adopted to estimate the fatigue lives of the USWed magnesium alloy joints. The fatigue life estimation, based on the fatigue crack growth model with the global and local stress intensity factors as a function of kink length and the experimentally determined kink angle, agreed fairly well with the obtained experimental results

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

    Science.gov (United States)

    Buch, A.

    1994-04-01

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

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

    Science.gov (United States)

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

    2016-09-01

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

  12. Fatigue damage of nuclear facilities; Endommagement par fatigue des installations nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    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.)

  13. Interfacial fatigue stress in PVD TiN coated tool steels under rolling contact fatigue conditions

    NARCIS (Netherlands)

    Carvalho, N.J.M.; Huis in 't Veld, A.J.; Hosson, J.T. de

    1998-01-01

    Titanium-nitrogen (TiN) films were Physical Vapour Deposited (PVD) on tool steel substrates with different hardness and surface roughness, in a Bai 640R unit using a triode ion plating (e-gun) with a high plasma density. The coated substrates were submitted to a rolling contact fatigue test techniqu

  14. 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

    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...

  15. Interfacial fatigue stress in PVD TiN coated tool steels under rolling contact fatigue conditions

    NARCIS (Netherlands)

    Carvalho, N.J.M.; Huis in ’t Veld, A.J.; Hosson, J.Th. De

    1998-01-01

    Titanium–nitrogen (TiN) films were Physical Vapour Deposited (PVD) on tool steel substrates with different hardness and surface roughness, in a Bai 640R unit using a triode ion plating (e-gun) with a high plasma density. The coated substrates were submitted to a rolling contact fatigue test techniqu

  16. Fatigue failure by flow-induced vibration. Effect on initial defect size on cumulative fatigue damage

    International Nuclear Information System (INIS)

    The method of fatigue life prediction is presented for structures which suffer from flow-induced vibration. A small wind tunnel was made and used to reproduce fatigue failure by flow-induced vibration. A medium carbon steel specimen attached to a larger styrofoam cylinder was fixed to the experimental equipment. A small artificial hole was introduced onto the specimen surface. Fatigue crack initiated from the artificial hole. A small portable strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project of the authors' team was used to acquire the service strain histogram at a critical point of the specimen and to measure the variation of natural frequency. Fatigue damage D defined by the Modified Miner Rule was calculated by using the strain histogram at the initial stage of the operation of the wind turbine. The values of D were all smaller than 1.0 and ranged approximately from 0.2 to 0.8. The reason for small values of D is explained from the behaviour of small crack growth. (author)

  17. Fibromyalgia, chronic fatigue syndrome, and myofascial pain.

    Science.gov (United States)

    Bennett, R

    1998-03-01

    Epidemiologic studies continue to provide evidence that fibromyalgia is part of a spectrum of chronic widespread pain. The prevalence of chronic widespread pain is several times higher than fibromyalgia as defined by the 1990 American College of Rheumatology guidelines. There is now compelling evidence of a familial clustering of fibromyalgia cases in female sufferers; whether this clustering results from nature or nature remains to be elucidated. A wide spectrum of fibromyalgia-associated symptomatology and syndromes continues to be described. During the past year the association with interstitial cystitis has been explored, and neurally mediated hypotension has been documented in both fibromyalgia and chronic fatigue syndrome. Abnormalities of the growth hormone-insulin-like growth factor-1 axis have been also documented in both fibromyalgia and chronic fatigue syndrome. The commonly reported but anecdotal association of fibromyalgia with whiplash-type neck trauma was validated in a report from Israel. However, unlike North America, 100% of Israeli patients with posttraumatic fibromyalgia returned to work. Basic research in fibromyalgia continues to pinpoint abnormal sensory processing as being integral to understanding fibromyalgia pain. Drugs such as ketamine, which block N-methyl-D-aspartate receptors (which are often upregulated in central pain states) were shown to benefit fibromyalgia pain in an experimental setting. The combination of fluoxetine and amitriptyline was reported to be more beneficial than either drug alone in patients with fibromyalgia. A high prevalence of autoantibodies to cytoskeletal and nuclear envelope proteins was found in chronic fatigue syndrome, and an increased prevalence of antipolymer antibodies was found in symptomatic silicone breast implant recipients who often have fibromyalgia.

  18. Fatigue behavior of lubricated Ni-Ti endodontic rotary instruments

    Directory of Open Access Journals (Sweden)

    A. Brotzu

    2014-04-01

    Full Text Available The use of Ni-Ti alloys in the practice of endodontic comes from their important properties such as shape memory and superelasticity phenomena, good corrosion resistance and high compatibility with biological tissues. In the last twenty years a great variety of nickel-titanium rotary instruments, with various sections and taper, have been developed and marketed. Although they have many advantages and despite their increasing popularity, a major concern with the use of Ni-Ti rotary instruments is the possibility of unexpected failure in use due to several reasons: novice operator handling, presence manufacturing defects, fatigue etc. Recently, the use of an aqueous gel during experimental tests showed a longer duration of the instruments. The aim of the present work is to contribute to the study of the fracture behavior of these endodontic rotary instruments particularly assessing whether the use of the aqueous lubricant gel can extend their operative life stating its reasons. A finite element model (FEM has been developed to support the experimental results. The results were rather contradictory, also because the Perspex (Poly-methyl methacrylate, PMMA cannot simulate completely the dentin mechanical behavior; however the results highlight some interesting points which are discussed in the paper.

  19. Laser thermal shock and fatigue testing system

    Science.gov (United States)

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

    1997-08-01

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

  20. Fatigue life of automotive rubber jounce bumper

    Energy Technology Data Exchange (ETDEWEB)

    Sidhu, R S [Automotive Engineering Unit, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM Serdang, Selangor (Malaysia); Ali, Aidy, E-mail: aidy@eng.upm.edu.my [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor (Malaysia)

    2010-05-15

    It is evident that most rubber components in the automotive industry are subjected to repetitive loading. Vigorous research is needed towards improving the safety and reliability of the components. The study was done on an automotive rubber jounce bumper with a rubber hardness of 60 IRHD. The test was conducted in displacement-controlled environment under compressive load. The existing models by Kim, Harbour, Woo and Li were adopted to predict the fatigue life. The experimental results show strong similarities with the predicted models.